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The Objective Caml system
release 3.10
Documentation and user's manual
Xavier Leroy
(with Damien Doligez, Jacques Garrigue, Didier Rémy and Jérôme Vouillon)
May 16, 2007
Copyright © 2005 Institut National de Recherche en Informatique et en
Automatique
---------------------------------------------------------------------------
This manual is also available in PDF (1). Postscript (2), DVI (3), plain
text (4), as a bundle of HTML files (5), and as a bundle of Emacs Info files
(6).
---------------------------------------------------------------------------
---------------------------------------
(1) http://caml.inria.fr/distrib/ocaml-3.10/ocaml-3.10-refman.pdf
(2) http://caml.inria.fr/distrib/ocaml-3.10/ocaml-3.10-refman.ps.gz
(3) http://caml.inria.fr/distrib/ocaml-3.10/ocaml-3.10-refman.dvi.gz
(4) http://caml.inria.fr/distrib/ocaml-3.10/ocaml-3.10-refman.txt
(5) http://caml.inria.fr/distrib/ocaml-3.10/ocaml-3.10-refman.html.tar.gz
(6) http://caml.inria.fr/distrib/ocaml-3.10/ocaml-3.10-refman.info.tar.gz
Contents
********
- Part: I An introduction to Objective Caml
- Chapter 1 The core language
- 1.1 Basics
- 1.2 Data types
- 1.3 Functions as values
- 1.4 Records and variants
- 1.5 Imperative features
- 1.6 Exceptions
- 1.7 Symbolic processing of expressions
- 1.8 Pretty-printing and parsing
- 1.9 Standalone Caml programs
- Chapter 2 The module system
- 2.1 Structures
- 2.2 Signatures
- 2.3 Functors
- 2.4 Functors and type abstraction
- 2.5 Modules and separate compilation
- Chapter 3 Objects in Caml
- 3.1 Classes and objects
- 3.2 Immediate objects
- 3.3 Reference to self
- 3.4 Initializers
- 3.5 Virtual methods
- 3.6 Private methods
- 3.7 Class interfaces
- 3.8 Inheritance
- 3.9 Multiple inheritance
- 3.10 Parameterized classes
- 3.11 Polymorphic methods
- 3.12 Using coercions
- 3.13 Functional objects
- 3.14 Cloning objects
- 3.15 Recursive classes
- 3.16 Binary methods
- 3.17 Friends
- Chapter 4 Labels and variants
- 4.1 Labels
- 4.1.1 Optional arguments
- 4.1.2 Labels and type inference
- 4.1.3 Suggestions for labeling
- 4.2 Polymorphic variants
- 4.2.1 Weaknesses of polymorphic variants
- Chapter 5 Advanced examples with classes and modules
- 5.1 Extended example: bank accounts
- 5.2 Simple modules as classes
- 5.2.1 Strings
- 5.2.2 Hashtbl
- 5.2.3 Sets
- 5.3 The subject/observer pattern
- Part: II The Objective Caml language
- Chapter 6 The Objective Caml language
- 6.1 Lexical conventions
- 6.2 Values
- 6.2.1 Base values
- 6.2.2 Tuples
- 6.2.3 Records
- 6.2.4 Arrays
- 6.2.5 Variant values
- 6.2.6 Polymorphic variants
- 6.2.7 Functions
- 6.2.8 Objects
- 6.3 Names
- 6.4 Type expressions
- 6.5 Constants
- 6.6 Patterns
- 6.7 Expressions
- 6.7.1 Basic expressions
- 6.7.2 Control structures
- 6.7.3 Operations on data structures
- 6.7.4 Operators
- 6.7.5 Objects
- 6.8 Type and exception definitions
- 6.8.1 Type definitions
- 6.8.2 Exception definitions
- 6.9 Classes
- 6.9.1 Class types
- 6.9.2 Class expressions
- 6.9.3 Class definitions
- 6.9.4 Class specification
- 6.9.5 Class type definitions
- 6.10 Module types (module specifications)
- 6.10.1 Simple module types
- 6.10.2 Signatures
- 6.10.3 Functor types
- 6.10.4 The with operator
- 6.11 Module expressions (module implementations)
- 6.11.1 Simple module expressions
- 6.11.2 Structures
- 6.11.3 Functors
- 6.12 Compilation units
- Chapter 7 Language extensions
- 7.1 Integer literals for types int32, int64 and nativeint
- 7.2 Streams and stream parsers
- 7.3 Recursive definitions of values
- 7.4 Range patterns
- 7.5 Assertion checking
- 7.6 Lazy evaluation
- 7.7 Local modules
- 7.8 Private types
- 7.9 Recursive modules
- 7.10 Private row types
- Part: III The Objective Caml tools
- Chapter 8 Batch compilation (ocamlc)
- 8.1 Overview of the compiler
- 8.2 Options
- 8.3 Modules and the file system
- 8.4 Common errors
- Chapter 9 The toplevel system (ocaml)
- 9.1 Options
- 9.2 Toplevel directives
- 9.3 The toplevel and the module system
- 9.4 Common errors
- 9.5 Building custom toplevel systems: ocamlmktop
- 9.6 Options
- Chapter 10 The runtime system (ocamlrun)
- 10.1 Overview
- 10.2 Options
- 10.3 Dynamic loading of shared libraries
- 10.4 Common errors
- Chapter 11 Native-code compilation (ocamlopt)
- 11.1 Overview of the compiler
- 11.2 Options
- 11.3 Common errors
- 11.4 Running executables produced by ocamlopt
- 11.5 Compatibility with the bytecode compiler
- Chapter 12 Lexer and parser generators (ocamllex, ocamlyacc)
- 12.1 Overview of ocamllex
- 12.1.1 Options
- 12.2 Syntax of lexer definitions
- 12.2.1 Header and trailer
- 12.2.2 Naming regular expressions
- 12.2.3 Entry points
- 12.2.4 Regular expressions
- 12.2.5 Actions
- 12.2.6 Variables in regular expressions
- 12.2.7 Reserved identifiers
- 12.3 Overview of ocamlyacc
- 12.4 Syntax of grammar definitions
- 12.4.1 Header and trailer
- 12.4.2 Declarations
- 12.4.3 Rules
- 12.4.4 Error handling
- 12.5 Options
- 12.6 A complete example
- 12.7 Common errors
- Chapter 13 Dependency generator (ocamldep)
- 13.1 Options
- 13.2 A typical Makefile
- Chapter 14 The browser/editor (ocamlbrowser)
- 14.1 Invocation
- 14.2 Viewer
- 14.3 Module browsing
- 14.4 File editor
- 14.5 Shell
- Chapter 15 The documentation generator (ocamldoc)
- 15.1 Usage
- 15.1.1 Invocation
- 15.1.2 Merging of module information
- 15.1.3 Coding rules
- 15.2 Syntax of documentation comments
- 15.2.1 Placement of documentation comments
- 15.2.2 The Stop special comment
- 15.2.3 Syntax of documentation comments
- 15.2.4 Text formatting
- 15.2.5 Documentation tags (@-tags)
- 15.3 Custom generators
- 15.3.1 The generator class
- 15.3.2 Handling custom tags
- 15.4 Adding command line options
- 15.4.1 Compilation and usage
- Chapter 16 The debugger (ocamldebug)
- 16.1 Compiling for debugging
- 16.2 Invocation
- 16.2.1 Starting the debugger
- 16.2.2 Exiting the debugger
- 16.3 Commands
- 16.3.1 Getting help
- 16.3.2 Accessing the debugger state
- 16.4 Executing a program
- 16.4.1 Events
- 16.4.2 Starting the debugged program
- 16.4.3 Running the program
- 16.4.4 Time travel
- 16.4.5 Killing the program
- 16.5 Breakpoints
- 16.6 The call stack
- 16.7 Examining variable values
- 16.8 Controlling the debugger
- 16.8.1 Setting the program name and arguments
- 16.8.2 How programs are loaded
- 16.8.3 Search path for files
- 16.8.4 Working directory
- 16.8.5 Turning reverse execution on and off
- 16.8.6 Communication between the debugger and the program
- 16.8.7 Fine-tuning the debugger
- 16.8.8 User-defined printers
- 16.9 Miscellaneous commands
- 16.10 Running the debugger under Emacs
- Chapter 17 Profiling (ocamlprof)
- 17.1 Compiling for profiling
- 17.2 Profiling an execution
- 17.3 Printing profiling information
- 17.4 Time profiling
- Chapter 18 Interfacing C with Objective Caml
- 18.1 Overview and compilation information
- 18.1.1 Declaring primitives
- 18.1.2 Implementing primitives
- 18.1.3 Statically linking C code with Caml code
- 18.1.4 Dynamically linking C code with Caml code
- 18.1.5 Choosing between static linking and dynamic linking
- 18.1.6 Building standalone custom runtime systems
- 18.2 The value type
- 18.2.1 Integer values
- 18.2.2 Blocks
- 18.2.3 Pointers outside the heap
- 18.3 Representation of Caml data types
- 18.3.1 Atomic types
- 18.3.2 Tuples and records
- 18.3.3 Arrays
- 18.3.4 Concrete types
- 18.3.5 Objects
- 18.3.6 Variants
- 18.4 Operations on values
- 18.4.1 Kind tests
- 18.4.2 Operations on integers
- 18.4.3 Accessing blocks
- 18.4.4 Allocating blocks
- 18.4.5 Raising exceptions
- 18.5 Living in harmony with the garbage collector
- 18.5.1 Simple interface
- 18.5.2 Low-level interface
- 18.6 A complete example
- 18.7 Advanced topic: callbacks from C to Caml
- 18.7.1 Applying Caml closures from C
- 18.7.2 Registering Caml closures for use in C functions
- 18.7.3 Registering Caml exceptions for use in C functions
- 18.7.4 Main program in C
- 18.7.5 Embedding the Caml code in the C code
- 18.8 Advanced example with callbacks
- 18.9 Advanced topic: custom blocks
- 18.9.1 The struct custom_operations
- 18.9.2 Allocating custom blocks
- 18.9.3 Accessing custom blocks
- 18.9.4 Writing custom serialization and deserialization functions
- 18.9.5 Choosing identifiers
- 18.9.6 Finalized blocks
- 18.10 Building mixed C/Caml libraries: ocamlmklib
- Part: IV The Objective Caml library
- Chapter 19 The core library
- 19.1 Built-in types and predefined exceptions
- 19.2 Module Pervasives : The initially opened module.
- Chapter 20 The standard library
- 20.1 Module Arg : Parsing of command line arguments.
- 20.2 Module Array : Array operations.
- 20.3 Module Buffer : Extensible string buffers.
- 20.4 Module Callback : Registering Caml values with the C runtime.
- 20.5 Module Char : Character operations.
- 20.6 Module Complex : Complex numbers.
- 20.7 Module Digest : MD5 message digest.
- 20.8 Module Filename : Operations on file names.
- 20.9 Module Format : Pretty printing.
- 20.10 Module Gc : Memory management control and statistics; finalised
values.
- 20.11 Module Genlex : A generic lexical analyzer.
- 20.12 Module Hashtbl : Hash tables and hash functions.
- 20.13 Module Int32 : 32-bit integers.
- 20.14 Module Int64 : 64-bit integers.
- 20.15 Module Lazy : Deferred computations.
- 20.16 Module Lexing : The run-time library for lexers generated by
ocamllex.
- 20.17 Module List : List operations.
- 20.18 Module Map : Association tables over ordered types.
- 20.19 Module Marshal : Marshaling of data structures.
- 20.20 Module Nativeint : Processor-native integers.
- 20.21 Module Oo : Operations on objects
- 20.22 Module Parsing : The run-time library for parsers generated by
ocamlyacc.
- 20.23 Module Printexc : Facilities for printing exceptions.
- 20.24 Module Printf : Formatted output functions.
- 20.25 Module Queue : First-in first-out queues.
- 20.26 Module Random : Pseudo-random number generators (PRNG).
- 20.27 Module Scanf : Formatted input functions.
- 20.28 Module Set : Sets over ordered types.
- 20.29 Module Sort : Sorting and merging lists.
- 20.30 Module Stack : Last-in first-out stacks.
- 20.31 Module StdLabels : Standard labeled libraries.
- 20.32 Module Stream : Streams and parsers.
- 20.33 Module String : String operations.
- 20.34 Module Sys : System interface.
- 20.35 Module Weak : Arrays of weak pointers and hash tables of weak
pointers.
- Chapter 21 The unix library: Unix system calls
- 21.1 Module Unix : Interface to the Unix system
- 21.2 Module UnixLabels: labelized version of the interface
- Chapter 22 The num library: arbitrary-precision rational arithmetic
- 22.1 Module Num : Operation on arbitrary-precision numbers.
- 22.2 Module Big_int : Operations on arbitrary-precision integers.
- 22.3 Module Arith_status : Flags that control rational arithmetic.
- Chapter 23 The str library: regular expressions and string processing
- 23.1 Module Str : Regular expressions and high-level string
processing
- Chapter 24 The threads library
- 24.1 Module Thread : Lightweight threads for Posix 1003.1c and Win32.
- 24.2 Module Mutex : Locks for mutual exclusion.
- 24.3 Module Condition : Condition variables to synchronize between
threads.
- 24.4 Module Event : First-class synchronous communication.
- 24.5 Module ThreadUnix : Thread-compatible system calls.
- Chapter 25 The graphics library
- 25.1 Module Graphics : Machine-independent graphics primitives.
- Chapter 26 The dbm library: access to NDBM databases
- 26.1 Module Dbm : Interface to the NDBM database.
- Chapter 27 The dynlink library: dynamic loading and linking of object
files
- 27.1 Module Dynlink : Dynamic loading of bytecode object files.
- Chapter 28 The LablTk library: Tcl/Tk GUI interface
- 28.1 Module Tk : Basic functions and types for LablTk
- Chapter 29 The bigarray library
- 29.1 Module Bigarray : Large, multi-dimensional, numerical arrays.
- 29.2 Big arrays in the Caml-C interface
- 29.2.1 Include file
- 29.2.2 Accessing a Caml bigarray from C or Fortran
- 29.2.3 Wrapping a C or Fortran array as a Caml big array
- Part: V Appendix
- Chapter 30 Index to the library
- Chapter 31 Index of keywords
Foreword
********
This manual documents the release 3.10 of the Objective Caml system. It is
organized as follows.
- Part I, "An introduction to Objective Caml", gives an overview of the
language.
- Part II, "The Objective Caml language", is the reference description of the
language.
- Part III, "The Objective Caml tools", documents the compilers, toplevel
system, and programming utilities.
- Part IV, "The Objective Caml library", describes the modules provided in the
standard library.
Conventions
*=*=*=*=*=*
Objective Caml runs on several operating systems. The parts of this manual
that are specific to one operating system are presented as shown below:
Unix:
This is material specific to the Unix family of operating systems,
including Linux and MacOS X.
Windows:
This is material specific to Microsoft Windows (2000, XP, Vista).
License
*=*=*=*
The Objective Caml system is copyright © 1996, 1997, 1998, 1999, 2000, 2001,
2002, 2003, 2004, 2005, 2006, 2007 Institut National de Recherche en
Informatique et en Automatique (INRIA). INRIA holds all ownership rights to the
Objective Caml system.
The Objective Caml system is open source and can be freely redistributed. See
the file LICENSE in the distribution for licensing information.
The present documentation is copyright © 2005 Institut National de Recherche
en Informatique et en Automatique (INRIA). The Objective Caml documentation and
user's manual may be reproduced and distributed in whole or in part, subject to
the following conditions:
- The copyright notice above and this permission notice must be preserved
complete on all complete or partial copies.
- Any translation or derivative work of the Objective Caml documentation and
user's manual must be approved by the authors in writing before
distribution.
- If you distribute the Objective Caml documentation and user's manual in
part, instructions for obtaining the complete version of this manual must be
included, and a means for obtaining a complete version provided.
- Small portions may be reproduced as illustrations for reviews or quotes in
other works without this permission notice if proper citation is given.
Availability
*=*=*=*=*=*=
The complete Objective Caml distribution can be accessed via the
http://caml.inria.fr/Caml Web site. The http://caml.inria.fr/Caml Web site
contains a lot of additional information on Objective Caml.
Part: I
*******
An introduction to Objective Caml
*********************************
Chapter 1 The core language
******************************
This part of the manual is a tutorial introduction to the Objective Caml
language. A good familiarity with programming in a conventional languages (say,
Pascal or C) is assumed, but no prior exposure to functional languages is
required. The present chapter introduces the core language. Chapter 3 deals
with the object-oriented features, and chapter 2 with the module system.
1.1 Basics
*=*=*=*=*=*
For this overview of Caml, we use the interactive system, which is started by
running ocaml from the Unix shell, or by launching the OCamlwin.exe application
under Windows. This tutorial is presented as the transcript of a session with
the interactive system: lines starting with # represent user input; the system
responses are printed below, without a leading #.
Under the interactive system, the user types Caml phrases, terminated by ;;,
in response to the # prompt, and the system compiles them on the fly, executes
them, and prints the outcome of evaluation. Phrases are either simple
expressions, or let definitions of identifiers (either values or functions).
<<#1+2*3;;
- : int = 7
#let pi = 4.0 *. atan 1.0;;
val pi : float = 3.14159265358979312
#let square x = x *. x;;
val square : float -> float = <fun>
#square(sin pi) +. square(cos pi);;
- : float = 1.
>>
The Caml system computes both the value and the type for each phrase. Even
function parameters need no explicit type declaration: the system infers their
types from their usage in the function. Notice also that integers and
floating-point numbers are distinct types, with distinct operators: + and *
operate on integers, but +. and *. operate on floats.
<<#1.0 * 2;;
This expression has type float but is here used with type int
>>
Recursive functions are defined with the let rec binding:
<<#let rec fib n =
# if n < 2 then 1 else fib(n-1) + fib(n-2);;
val fib : int -> int = <fun>
#fib 10;;
- : int = 89
>>
1.2 Data types
*=*=*=*=*=*=*=*
In addition to integers and floating-point numbers, Caml offers the usual
basic data types: booleans, characters, and character strings.
<<#(1 < 2) = false;;
- : bool = false
#'a';;
- : char = 'a'
#"Hello world";;
- : string = "Hello world"
>>
Predefined data structures include tuples, arrays, and lists. General
mechanisms for defining your own data structures are also provided. They will
be covered in more details later; for now, we concentrate on lists. Lists are
either given in extension as a bracketed list of semicolon-separated elements,
or built from the empty list [] (pronounce "nil") by adding elements in front
using the :: ("cons") operator.
<<#let l = ["is"; "a"; "tale"; "told"; "etc."];;
val l : string list = ["is"; "a"; "tale"; "told"; "etc."]
#"Life" :: l;;
- : string list = ["Life"; "is"; "a"; "tale"; "told"; "etc."]
>>
As with all other Caml data structures, lists do not need to be explicitly
allocated and deallocated from memory: all memory management is entirely
automatic in Caml. Similarly, there is no explicit handling of pointers: the
Caml compiler silently introduces pointers where necessary.
As with most Caml data structures, inspecting and destructuring lists is
performed by pattern-matching. List patterns have the exact same shape as list
expressions, with identifier representing unspecified parts of the list. As an
example, here is insertion sort on a list:
<<#let rec sort lst =
# match lst with
# [] -> []
# | head :: tail -> insert head (sort tail)
#and insert elt lst =
# match lst with
# [] -> [elt]
# | head :: tail -> if elt <= head then elt :: lst else head :: insert elt
tail
#;;
val sort : 'a list -> 'a list = <fun>
val insert : 'a -> 'a list -> 'a list = <fun>
#sort l;;
- : string list = ["a"; "etc."; "is"; "tale"; "told"]
>>
The type inferred for sort, 'a list -> 'a list, means that sort can actually
apply to lists of any type, and returns a list of the same type. The type 'a is
a type variable, and stands for any given type. The reason why sort can apply
to lists of any type is that the comparisons (=, <=, etc.) are polymorphic in
Caml: they operate between any two values of the same type. This makes sort
itself polymorphic over all list types.
<<#sort [6;2;5;3];;
- : int list = [2; 3; 5; 6]
#sort [3.14; 2.718];;
- : float list = [2.718; 3.14]
>>
The sort function above does not modify its input list: it builds and returns
a new list containing the same elements as the input list, in ascending order.
There is actually no way in Caml to modify in-place a list once it is built: we
say that lists are immutable data structures. Most Caml data structures are
immutable, but a few (most notably arrays) are mutable, meaning that they can
be modified in-place at any time.
1.3 Functions as values
*=*=*=*=*=*=*=*=*=*=*=*=
Caml is a functional language: functions in the full mathematical sense are
supported and can be passed around freely just as any other piece of data. For
instance, here is a deriv function that takes any float function as argument
and returns an approximation of its derivative function:
<<#let deriv f dx = function x -> (f(x +. dx) -. f(x)) /. dx;;
val deriv : (float -> float) -> float -> float -> float = <fun>
#let sin' = deriv sin 1e-6;;
val sin' : float -> float = <fun>
#sin' pi;;
- : float = -1.00000000013961143
>>
Even function composition is definable:
<<#let compose f g = function x -> f(g(x));;
val compose : ('a -> 'b) -> ('c -> 'a) -> 'c -> 'b = <fun>
#let cos2 = compose square cos;;
val cos2 : float -> float = <fun>
>>
Functions that take other functions as arguments are called "functionals", or
"higher-order functions". Functionals are especially useful to provide
iterators or similar generic operations over a data structure. For instance,
the standard Caml library provides a List.map functional that applies a given
function to each element of a list, and returns the list of the results:
<<#List.map (function n -> n * 2 + 1) [0;1;2;3;4];;
- : int list = [1; 3; 5; 7; 9]
>>
This functional, along with a number of other list and array functionals, is
predefined because it is often useful, but there is nothing magic with it: it
can easily be defined as follows.
<<#let rec map f l =
# match l with
# [] -> []
# | hd :: tl -> f hd :: map f tl;;
val map : ('a -> 'b) -> 'a list -> 'b list = <fun>
>>
1.4 Records and variants
*=*=*=*=*=*=*=*=*=*=*=*=*
User-defined data structures include records and variants. Both are defined
with the type declaration. Here, we declare a record type to represent rational
numbers.
<<#type ratio = {num: int; denum: int};;
type ratio = { num : int; denum : int; }
#let add_ratio r1 r2 =
# {num = r1.num * r2.denum + r2.num * r1.denum;
# denum = r1.denum * r2.denum};;
val add_ratio : ratio -> ratio -> ratio = <fun>
#add_ratio {num=1; denum=3} {num=2; denum=5};;
- : ratio = {num = 11; denum = 15}
>>
The declaration of a variant type lists all possible shapes for values of
that type. Each case is identified by a name, called a constructor, which
serves both for constructing values of the variant type and inspecting them by
pattern-matching. Constructor names are capitalized to distinguish them from
variable names (which must start with a lowercase letter). For instance, here
is a variant type for doing mixed arithmetic (integers and floats):
<<#type number = Int of int | Float of float | Error;;
type number = Int of int | Float of float | Error
>>
This declaration expresses that a value of type number is either an integer,
a floating-point number, or the constant Error representing the result of an
invalid operation (e.g. a division by zero).
Enumerated types are a special case of variant types, where all alternatives
are constants:
<<#type sign = Positive | Negative;;
type sign = Positive | Negative
#let sign_int n = if n >= 0 then Positive else Negative;;
val sign_int : int -> sign = <fun>
>>
To define arithmetic operations for the number type, we use pattern-matching
on the two numbers involved:
<<#let add_num n1 n2 =
# match (n1, n2) with
# (Int i1, Int i2) ->
# (* Check for overflow of integer addition *)
# if sign_int i1 = sign_int i2 && sign_int(i1 + i2) <> sign_int i1
# then Float(float i1 +. float i2)
# else Int(i1 + i2)
# | (Int i1, Float f2) -> Float(float i1 +. f2)
# | (Float f1, Int i2) -> Float(f1 +. float i2)
# | (Float f1, Float f2) -> Float(f1 +. f2)
# | (Error, _) -> Error
# | (_, Error) -> Error;;
val add_num : number -> number -> number = <fun>
#add_num (Int 123) (Float 3.14159);;
- : number = Float 126.14159
>>
The most common usage of variant types is to describe recursive data
structures. Consider for example the type of binary trees:
<<#type 'a btree = Empty | Node of 'a * 'a btree * 'a btree;;
type 'a btree = Empty | Node of 'a * 'a btree * 'a btree
>>
This definition reads as follow: a binary tree containing values of type 'a
(an arbitrary type) is either empty, or is a node containing one value of type
'a and two subtrees containing also values of type 'a, that is, two 'a btree.
Operations on binary trees are naturally expressed as recursive functions
following the same structure as the type definition itself. For instance, here
are functions performing lookup and insertion in ordered binary trees (elements
increase from left to right):
<<#let rec member x btree =
# match btree with
# Empty -> false
# | Node(y, left, right) ->
# if x = y then true else
# if x < y then member x left else member x right;;
val member : 'a -> 'a btree -> bool = <fun>
#let rec insert x btree =
# match btree with
# Empty -> Node(x, Empty, Empty)
# | Node(y, left, right) ->
# if x <= y then Node(y, insert x left, right)
# else Node(y, left, insert x right);;
val insert : 'a -> 'a btree -> 'a btree = <fun>
>>
1.5 Imperative features
*=*=*=*=*=*=*=*=*=*=*=*=
Though all examples so far were written in purely applicative style, Caml is
also equipped with full imperative features. This includes the usual while and
for loops, as well as mutable data structures such as arrays. Arrays are either
given in extension between [| and |] brackets, or allocated and initialized
with the Array.create function, then filled up later by assignments. For
instance, the function below sums two vectors (represented as float arrays)
componentwise.
<<#let add_vect v1 v2 =
# let len = min (Array.length v1) (Array.length v2) in
# let res = Array.create len 0.0 in
# for i = 0 to len - 1 do
# res.(i) <- v1.(i) +. v2.(i)
# done;
# res;;
val add_vect : float array -> float array -> float array = <fun>
#add_vect [| 1.0; 2.0 |] [| 3.0; 4.0 |];;
- : float array = [|4.; 6.|]
>>
Record fields can also be modified by assignment, provided they are declared
mutable in the definition of the record type:
<<#type mutable_point = { mutable x: float; mutable y: float };;
type mutable_point = { mutable x : float; mutable y : float; }
#let translate p dx dy =
# p.x <- p.x +. dx; p.y <- p.y +. dy;;
val translate : mutable_point -> float -> float -> unit = <fun>
#let mypoint = { x = 0.0; y = 0.0 };;
val mypoint : mutable_point = {x = 0.; y = 0.}
#translate mypoint 1.0 2.0;;
- : unit = ()
#mypoint;;
- : mutable_point = {x = 1.; y = 2.}
>>
Caml has no built-in notion of variable -- identifiers whose current value
can be changed by assignment. (The let binding is not an assignment, it
introduces a new identifier with a new scope.) However, the standard library
provides references, which are mutable indirection cells (or one-element
arrays), with operators ! to fetch the current contents of the reference and :=
to assign the contents. Variables can then be emulated by let-binding a
reference. For instance, here is an in-place insertion sort over arrays:
<<#let insertion_sort a =
# for i = 1 to Array.length a - 1 do
# let val_i = a.(i) in
# let j = ref i in
# while !j > 0 && val_i < a.(!j - 1) do
# a.(!j) <- a.(!j - 1);
# j := !j - 1
# done;
# a.(!j) <- val_i
# done;;
val insertion_sort : 'a array -> unit = <fun>
>>
References are also useful to write functions that maintain a current state
between two calls to the function. For instance, the following pseudo-random
number generator keeps the last returned number in a reference:
<<#let current_rand = ref 0;;
val current_rand : int ref = {contents = 0}
#let random () =
# current_rand := !current_rand * 25713 + 1345;
# !current_rand;;
val random : unit -> int = <fun>
>>
Again, there is nothing magic with references: they are implemented as a
one-field mutable record, as follows.
<<#type 'a ref = { mutable contents: 'a };;
type 'a ref = { mutable contents : 'a; }
#let (!) r = r.contents;;
val ( ! ) : 'a ref -> 'a = <fun>
#let (:=) r newval = r.contents <- newval;;
val ( := ) : 'a ref -> 'a -> unit = <fun>
>>
In some special cases, you may need to store a polymorphic function in a data
structure, keeping its polymorphism. Without user-provided type annotations,
this is not allowed, as polymorphism is only introduced on a global level.
However, you can give explicitly polymorphic types to record fields.
<<#type idref = { mutable id: 'a. 'a -> 'a };;
type idref = { mutable id : 'a. 'a -> 'a; }
#let r = {id = fun x -> x};;
val r : idref = {id = <fun>}
#let g s = (s.id 1, s.id true);;
val g : idref -> int * bool = <fun>
#r.id <- (fun x -> print_string "called id\n"; x);;
- : unit = ()
#g r;;
called id
called id
- : int * bool = (1, true)
>>
1.6 Exceptions
*=*=*=*=*=*=*=*
Caml provides exceptions for signalling and handling exceptional conditions.
Exceptions can also be used as a general-purpose non-local control structure.
Exceptions are declared with the exception construct, and signalled with the
raise operator. For instance, the function below for taking the head of a list
uses an exception to signal the case where an empty list is given.
<<#exception Empty_list;;
exception Empty_list
#let head l =
# match l with
# [] -> raise Empty_list
# | hd :: tl -> hd;;
val head : 'a list -> 'a = <fun>
#head [1;2];;
- : int = 1
#head [];;
Exception: Empty_list.
>>
Exceptions are used throughout the standard library to signal cases where the
library functions cannot complete normally. For instance, the List.assoc
function, which returns the data associated with a given key in a list of (key,
data) pairs, raises the predefined exception Not_found when the key does not
appear in the list:
<<#List.assoc 1 [(0, "zero"); (1, "one")];;
- : string = "one"
#List.assoc 2 [(0, "zero"); (1, "one")];;
Exception: Not_found.
>>
Exceptions can be trapped with the try...with construct:
<<#let name_of_binary_digit digit =
# try
# List.assoc digit [0, "zero"; 1, "one"]
# with Not_found ->
# "not a binary digit";;
val name_of_binary_digit : int -> string = <fun>
#name_of_binary_digit 0;;
- : string = "zero"
#name_of_binary_digit (-1);;
- : string = "not a binary digit"
>>
The with part is actually a regular pattern-matching on the exception value.
Thus, several exceptions can be caught by one try...with construct. Also,
finalization can be performed by trapping all exceptions, performing the
finalization, then raising again the exception:
<<#let temporarily_set_reference ref newval funct =
# let oldval = !ref in
# try
# ref := newval;
# let res = funct () in
# ref := oldval;
# res
# with x ->
# ref := oldval;
# raise x;;
val temporarily_set_reference : 'a ref -> 'a -> (unit -> 'b) -> 'b = <fun>
>>
1.7 Symbolic processing of expressions
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
We finish this introduction with a more complete example representative of
the use of Caml for symbolic processing: formal manipulations of arithmetic
expressions containing variables. The following variant type describes the
expressions we shall manipulate:
<<#type expression =
# Const of float
# | Var of string
# | Sum of expression * expression (* e1 + e2 *)
# | Diff of expression * expression (* e1 - e2 *)
# | Prod of expression * expression (* e1 * e2 *)
# | Quot of expression * expression (* e1 / e2 *)
#;;
type expression =
Const of float
| Var of string
| Sum of expression * expression
| Diff of expression * expression
| Prod of expression * expression
| Quot of expression * expression
>>
We first define a function to evaluate an expression given an environment
that maps variable names to their values. For simplicity, the environment is
represented as an association list.
<<#exception Unbound_variable of string;;
exception Unbound_variable of string
#let rec eval env exp =
# match exp with
# Const c -> c
# | Var v ->
# (try List.assoc v env with Not_found -> raise(Unbound_variable v))
# | Sum(f, g) -> eval env f +. eval env g
# | Diff(f, g) -> eval env f -. eval env g
# | Prod(f, g) -> eval env f *. eval env g
# | Quot(f, g) -> eval env f /. eval env g;;
val eval : (string * float) list -> expression -> float = <fun>
#eval [("x", 1.0); ("y", 3.14)] (Prod(Sum(Var "x", Const 2.0), Var "y"));;
- : float = 9.42
>>
Now for a real symbolic processing, we define the derivative of an expression
with respect to a variable dv:
<<#let rec deriv exp dv =
# match exp with
# Const c -> Const 0.0
# | Var v -> if v = dv then Const 1.0 else Const 0.0
# | Sum(f, g) -> Sum(deriv f dv, deriv g dv)
# | Diff(f, g) -> Diff(deriv f dv, deriv g dv)
# | Prod(f, g) -> Sum(Prod(f, deriv g dv), Prod(deriv f dv, g))
# | Quot(f, g) -> Quot(Diff(Prod(deriv f dv, g), Prod(f, deriv g dv)),
# Prod(g, g))
#;;
val deriv : expression -> string -> expression = <fun>
#deriv (Quot(Const 1.0, Var "x")) "x";;
- : expression =
Quot (Diff (Prod (Const 0., Var "x"), Prod (Const 1., Const 1.)),
Prod (Var "x", Var "x"))
>>
1.8 Pretty-printing and parsing
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
As shown in the examples above, the internal representation (also called
abstract syntax) of expressions quickly becomes hard to read and write as the
expressions get larger. We need a printer and a parser to go back and forth
between the abstract syntax and the concrete syntax, which in the case of
expressions is the familiar algebraic notation (e.g. 2*x+1).
For the printing function, we take into account the usual precedence rules
(i.e. * binds tighter than +) to avoid printing unnecessary parentheses. To
this end, we maintain the current operator precedence and print parentheses
around an operator only if its precedence is less than the current precedence.
<<#let print_expr exp =
# (* Local function definitions *)
# let open_paren prec op_prec =
# if prec > op_prec then print_string "(" in
# let close_paren prec op_prec =
# if prec > op_prec then print_string ")" in
# let rec print prec exp = (* prec is the current precedence *)
# match exp with
# Const c -> print_float c
# | Var v -> print_string v
# | Sum(f, g) ->
# open_paren prec 0;
# print 0 f; print_string " + "; print 0 g;
# close_paren prec 0
# | Diff(f, g) ->
# open_paren prec 0;
# print 0 f; print_string " - "; print 1 g;
# close_paren prec 0
# | Prod(f, g) ->
# open_paren prec 2;
# print 2 f; print_string " * "; print 2 g;
# close_paren prec 2
# | Quot(f, g) ->
# open_paren prec 2;
# print 2 f; print_string " / "; print 3 g;
# close_paren prec 2
# in print 0 exp;;
val print_expr : expression -> unit = <fun>
#let e = Sum(Prod(Const 2.0, Var "x"), Const 1.0);;
val e : expression = Sum (Prod (Const 2., Var "x"), Const 1.)
#print_expr e; print_newline();;
2. * x + 1.
- : unit = ()
#print_expr (deriv e "x"); print_newline();;
2. * 1. + 0. * x + 0.
- : unit = ()
>>
Parsing (transforming concrete syntax into abstract syntax) is usually more
delicate. Caml offers several tools to help write parsers: on the one hand,
Caml versions of the lexer generator Lex and the parser generator Yacc (see
chapter 12), which handle LALR(1) languages using push-down automata; on the
other hand, a predefined type of streams (of characters or tokens) and
pattern-matching over streams, which facilitate the writing of
recursive-descent parsers for LL(1) languages. An example using ocamllex and
ocamlyacc is given in chapter 12. Here, we will use stream parsers. The
syntactic support for stream parsers is provided by the Camlp4 preprocessor,
which can be loaded into the interactive toplevel via the #load directive
below.
<<##load "camlp4o.cma";;
Camlp4 Parsing version 3.10+dev26 (2007-04-25)
#open Genlex;;
#let lexer = make_lexer ["("; ")"; "+"; "-"; "*"; "/"];;
val lexer : char Stream.t -> Genlex.token Stream.t = <fun>
>>
For the lexical analysis phase (transformation of the input text into a
stream of tokens), we use a "generic" lexer provided in the standard library
module Genlex. The make_lexer function takes a list of keywords and returns a
lexing function that "tokenizes" an input stream of characters. Tokens are
either identifiers, keywords, or literals (integer, floats, characters,
strings). Whitespace and comments are skipped.
<<#let token_stream = lexer(Stream.of_string "1.0 +x");;
val token_stream : Genlex.token Stream.t = <abstr>
#Stream.next token_stream;;
- : Genlex.token = Float 1.
#Stream.next token_stream;;
- : Genlex.token = Kwd "+"
#Stream.next token_stream;;
- : Genlex.token = Ident "x"
>>
The parser itself operates by pattern-matching on the stream of tokens. As
usual with recursive descent parsers, we use several intermediate parsing
functions to reflect the precedence and associativity of operators.
Pattern-matching over streams is more powerful than on regular data structures,
as it allows recursive calls to parsing functions inside the patterns, for
matching sub-components of the input stream. See the Camlp4 documentation for
more details.
<<#let rec parse_expr = parser
# [< e1 = parse_mult; e = parse_more_adds e1 >] -> e
#and parse_more_adds e1 = parser
# [< 'Kwd "+"; e2 = parse_mult; e = parse_more_adds (Sum(e1, e2)) >] -> e
# | [< 'Kwd "-"; e2 = parse_mult; e = parse_more_adds (Diff(e1, e2)) >] -> e
# | [< >] -> e1
#and parse_mult = parser
# [< e1 = parse_simple; e = parse_more_mults e1 >] -> e
#and parse_more_mults e1 = parser
# [< 'Kwd "*"; e2 = parse_simple; e = parse_more_mults (Prod(e1, e2)) >]
-> e
# | [< 'Kwd "/"; e2 = parse_simple; e = parse_more_mults (Quot(e1, e2)) >]
-> e
# | [< >] -> e1
#and parse_simple = parser
# [< 'Ident s >] -> Var s
# | [< 'Int i >] -> Const(float i)
# | [< 'Float f >] -> Const f
# | [< 'Kwd "("; e = parse_expr; 'Kwd ")" >] -> e;;
val parse_expr : Genlex.token Stream.t -> expression = <fun>
val parse_more_adds : expression -> Genlex.token Stream.t -> expression =
<fun>
val parse_mult : Genlex.token Stream.t -> expression = <fun>
val parse_more_mults : expression -> Genlex.token Stream.t -> expression =
<fun>
val parse_simple : Genlex.token Stream.t -> expression = <fun>
#let parse_expression = parser [< e = parse_expr; _ = Stream.empty >] -> e;;
val parse_expression : Genlex.token Stream.t -> expression = <fun>
>>
Composing the lexer and parser, we finally obtain a function to read an
expression from a character string:
<<#let read_expression s = parse_expression(lexer(Stream.of_string s));;
val read_expression : string -> expression = <fun>
#read_expression "2*(x+y)";;
- : expression = Prod (Const 2., Sum (Var "x", Var "y"))
>>
A small puzzle: why do we get different results in the following two
examples?
<<#read_expression "x - 1";;
- : expression = Diff (Var "x", Const 1.)
#read_expression "x-1";;
Exception: Stream.Error "".
>>
Answer: the generic lexer provided by Genlex recognizes negative integer
literals as one integer token. Hence, x-1 is read as the token Ident "x"
followed by the token Int(-1); this sequence does not match any of the parser
rules. On the other hand, the second space in x - 1 causes the lexer to return
the three expected tokens: Ident "x", then Kwd "-", then Int(1).
1.9 Standalone Caml programs
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
All examples given so far were executed under the interactive system. Caml
code can also be compiled separately and executed non-interactively using the
batch compilers ocamlc or ocamlopt. The source code must be put in a file with
extension .ml. It consists of a sequence of phrases, which will be evaluated at
runtime in their order of appearance in the source file. Unlike in interactive
mode, types and values are not printed automatically; the program must call
printing functions explicitly to produce some output. Here is a sample
standalone program to print Fibonacci numbers:
<<(* File fib.ml *)
let rec fib n =
if n < 2 then 1 else fib(n-1) + fib(n-2);;
let main () =
let arg = int_of_string Sys.argv.(1) in
print_int(fib arg);
print_newline();
exit 0;;
main ();;
>>
Sys.argv is an array of strings containing the command-line parameters.
Sys.argv.(1) is thus the first command-line parameter. The program above is
compiled and executed with the following shell commands:
<<$ ocamlc -o fib fib.ml
$ ./fib 10
89
$ ./fib 20
10946
>>
Chapter 2 The module system
******************************
This chapter introduces the module system of Objective Caml.
2.1 Structures
*=*=*=*=*=*=*=*
A primary motivation for modules is to package together related definitions
(such as the definitions of a data type and associated operations over that
type) and enforce a consistent naming scheme for these definitions. This avoids
running out of names or accidentally confusing names. Such a package is called
a structure and is introduced by the struct...end construct, which contains an
arbitrary sequence of definitions. The structure is usually given a name with
the module binding. Here is for instance a structure packaging together a type
of priority queues and their operations:
<<#module PrioQueue =
# struct
# type priority = int
# type 'a queue = Empty | Node of priority * 'a * 'a queue * 'a queue
# let empty = Empty
# let rec insert queue prio elt =
# match queue with
# Empty -> Node(prio, elt, Empty, Empty)
# | Node(p, e, left, right) ->
# if prio <= p
# then Node(prio, elt, insert right p e, left)
# else Node(p, e, insert right prio elt, left)
# exception Queue_is_empty
# let rec remove_top = function
# Empty -> raise Queue_is_empty
# | Node(prio, elt, left, Empty) -> left
# | Node(prio, elt, Empty, right) -> right
# | Node(prio, elt, (Node(lprio, lelt, _, _) as left),
# (Node(rprio, relt, _, _) as right)) ->
# if lprio <= rprio
# then Node(lprio, lelt, remove_top left, right)
# else Node(rprio, relt, left, remove_top right)
# let extract = function
# Empty -> raise Queue_is_empty
# | Node(prio, elt, _, _) as queue -> (prio, elt, remove_top queue)
# end;;
module PrioQueue :
sig
type priority = int
type 'a queue = Empty | Node of priority * 'a * 'a queue * 'a queue
val empty : 'a queue
val insert : 'a queue -> priority -> 'a -> 'a queue
exception Queue_is_empty
val remove_top : 'a queue -> 'a queue
val extract : 'a queue -> priority * 'a * 'a queue
end
>>
Outside the structure, its components can be referred to using the "dot
notation", that is, identifiers qualified by a structure name. For instance,
PrioQueue.insert in a value context is the function insert defined inside the
structure PrioQueue. Similarly, PrioQueue.queue in a type context is the type
queue defined in PrioQueue.
<<#PrioQueue.insert PrioQueue.empty 1 "hello";;
- : string PrioQueue.queue =
PrioQueue.Node (1, "hello", PrioQueue.Empty, PrioQueue.Empty)
>>
2.2 Signatures
*=*=*=*=*=*=*=*
Signatures are interfaces for structures. A signature specifies which
components of a structure are accessible from the outside, and with which type.
It can be used to hide some components of a structure (e.g. local function
definitions) or export some components with a restricted type. For instance,
the signature below specifies the three priority queue operations empty, insert
and extract, but not the auxiliary function remove_top. Similarly, it makes the
queue type abstract (by not providing its actual representation as a concrete
type).
<<#module type PRIOQUEUE =
# sig
# type priority = int (* still concrete *)
# type 'a queue (* now abstract *)
# val empty : 'a queue
# val insert : 'a queue -> int -> 'a -> 'a queue
# val extract : 'a queue -> int * 'a * 'a queue
# exception Queue_is_empty
# end;;
module type PRIOQUEUE =
sig
type priority = int
type 'a queue
val empty : 'a queue
val insert : 'a queue -> int -> 'a -> 'a queue
val extract : 'a queue -> int * 'a * 'a queue
exception Queue_is_empty
end
>>
Restricting the PrioQueue structure by this signature results in another
view of the PrioQueue structure where the remove_top function is not accessible
and the actual representation of priority queues is hidden:
<<#module AbstractPrioQueue = (PrioQueue : PRIOQUEUE);;
module AbstractPrioQueue : PRIOQUEUE
#AbstractPrioQueue.remove_top;;
Unbound value AbstractPrioQueue.remove_top
#AbstractPrioQueue.insert AbstractPrioQueue.empty 1 "hello";;
- : string AbstractPrioQueue.queue = <abstr>
>>
The restriction can also be performed during the definition of the
structure, as in
<<module PrioQueue = (struct ... end : PRIOQUEUE);;
>>
An alternate syntax is provided for the above:
<<module PrioQueue : PRIOQUEUE = struct ... end;;
>>
2.3 Functors
*=*=*=*=*=*=*
Functors are "functions" from structures to structures. They are used to
express parameterized structures: a structure A parameterized by a structure B
is simply a functor F with a formal parameter B (along with the expected
signature for B) which returns the actual structure A itself. The functor F can
then be applied to one or several implementations B_1 ...B_n of B, yielding the
corresponding structures A_1 ...A_n.
For instance, here is a structure implementing sets as sorted lists,
parameterized by a structure providing the type of the set elements and an
ordering function over this type (used to keep the sets sorted):
<<#type comparison = Less | Equal | Greater;;
type comparison = Less | Equal | Greater
#module type ORDERED_TYPE =
# sig
# type t
# val compare: t -> t -> comparison
# end;;
module type ORDERED_TYPE = sig type t val compare : t -> t -> comparison end
#module Set =
# functor (Elt: ORDERED_TYPE) ->
# struct
# type element = Elt.t
# type set = element list
# let empty = []
# let rec add x s =
# match s with
# [] -> [x]
# | hd::tl ->
# match Elt.compare x hd with
# Equal -> s (* x is already in s *)
# | Less -> x :: s (* x is smaller than all elements of s *)
# | Greater -> hd :: add x tl
# let rec member x s =
# match s with
# [] -> false
# | hd::tl ->
# match Elt.compare x hd with
# Equal -> true (* x belongs to s *)
# | Less -> false (* x is smaller than all elements of s *)
# | Greater -> member x tl
# end;;
module Set :
functor (Elt : ORDERED_TYPE) ->
sig
type element = Elt.t
type set = element list
val empty : 'a list
val add : Elt.t -> Elt.t list -> Elt.t list
val member : Elt.t -> Elt.t list -> bool
end
>>
By applying the Set functor to a structure implementing an ordered type, we
obtain set operations for this type:
<<#module OrderedString =
# struct
# type t = string
# let compare x y = if x = y then Equal else if x < y then Less else
Greater
# end;;
module OrderedString :
sig type t = string val compare : 'a -> 'a -> comparison end
#module StringSet = Set(OrderedString);;
module StringSet :
sig
type element = OrderedString.t
type set = element list
val empty : 'a list
val add : OrderedString.t -> OrderedString.t list -> OrderedString.t list
val member : OrderedString.t -> OrderedString.t list -> bool
end
#StringSet.member "bar" (StringSet.add "foo" StringSet.empty);;
- : bool = false
>>
2.4 Functors and type abstraction
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
As in the PrioQueue example, it would be good style to hide the actual
implementation of the type set, so that users of the structure will not rely on
sets being lists, and we can switch later to another, more efficient
representation of sets without breaking their code. This can be achieved by
restricting Set by a suitable functor signature:
<<#module type SETFUNCTOR =
# functor (Elt: ORDERED_TYPE) ->
# sig
# type element = Elt.t (* concrete *)
# type set (* abstract *)
# val empty : set
# val add : element -> set -> set
# val member : element -> set -> bool
# end;;
module type SETFUNCTOR =
functor (Elt : ORDERED_TYPE) ->
sig
type element = Elt.t
type set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#module AbstractSet = (Set : SETFUNCTOR);;
module AbstractSet : SETFUNCTOR
#module AbstractStringSet = AbstractSet(OrderedString);;
module AbstractStringSet :
sig
type element = OrderedString.t
type set = AbstractSet(OrderedString).set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#AbstractStringSet.add "gee" AbstractStringSet.empty;;
- : AbstractStringSet.set = <abstr>
>>
In an attempt to write the type constraint above more elegantly, one may wish
to name the signature of the structure returned by the functor, then use that
signature in the constraint:
<<#module type SET =
# sig
# type element
# type set
# val empty : set
# val add : element -> set -> set
# val member : element -> set -> bool
# end;;
module type SET =
sig
type element
type set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#module WrongSet = (Set : functor(Elt: ORDERED_TYPE) -> SET);;
module WrongSet : functor (Elt : ORDERED_TYPE) -> SET
#module WrongStringSet = WrongSet(OrderedString);;
module WrongStringSet :
sig
type element = WrongSet(OrderedString).element
type set = WrongSet(OrderedString).set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#WrongStringSet.add "gee" WrongStringSet.empty;;
This expression has type string but is here used with type
WrongStringSet.element = WrongSet(OrderedString).element
>>
The problem here is that SET specifies the type element abstractly, so that
the type equality between element in the result of the functor and t in its
argument is forgotten. Consequently, WrongStringSet.element is not the same
type as string, and the operations of WrongStringSet cannot be applied to
strings. As demonstrated above, it is important that the type element in the
signature SET be declared equal to Elt.t; unfortunately, this is impossible
above since SET is defined in a context where Elt does not exist. To overcome
this difficulty, Objective Caml provides a with type construct over signatures
that allows to enrich a signature with extra type equalities:
<<#module AbstractSet =
# (Set : functor(Elt: ORDERED_TYPE) -> (SET with type element = Elt.t));;
module AbstractSet :
functor (Elt : ORDERED_TYPE) ->
sig
type element = Elt.t
type set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
>>
As in the case of simple structures, an alternate syntax is provided for
defining functors and restricting their result:
<<module AbstractSet(Elt: ORDERED_TYPE) : (SET with type element = Elt.t) =
struct ... end;;
>>
Abstracting a type component in a functor result is a powerful technique that
provides a high degree of type safety, as we now illustrate. Consider an
ordering over character strings that is different from the standard ordering
implemented in the OrderedString structure. For instance, we compare strings
without distinguishing upper and lower case.
<<#module NoCaseString =
# struct
# type t = string
# let compare s1 s2 =
# OrderedString.compare (String.lowercase s1) (String.lowercase s2)
# end;;
module NoCaseString :
sig type t = string val compare : string -> string -> comparison end
#module NoCaseStringSet = AbstractSet(NoCaseString);;
module NoCaseStringSet :
sig
type element = NoCaseString.t
type set = AbstractSet(NoCaseString).set
val empty : set
val add : element -> set -> set
val member : element -> set -> bool
end
#NoCaseStringSet.add "FOO" AbstractStringSet.empty;;
This expression has type
AbstractStringSet.set = AbstractSet(OrderedString).set
but is here used with type
NoCaseStringSet.set = AbstractSet(NoCaseString).set
>>
Notice that the two types AbstractStringSet.set and NoCaseStringSet.set are
not compatible, and values of these two types do not match. This is the correct
behavior: even though both set types contain elements of the same type
(strings), both are built upon different orderings of that type, and different
invariants need to be maintained by the operations (being strictly increasing
for the standard ordering and for the case-insensitive ordering). Applying
operations from AbstractStringSet to values of type NoCaseStringSet.set could
give incorrect results, or build lists that violate the invariants of
NoCaseStringSet.
2.5 Modules and separate compilation
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
All examples of modules so far have been given in the context of the
interactive system. However, modules are most useful for large, batch-compiled
programs. For these programs, it is a practical necessity to split the source
into several files, called compilation units, that can be compiled separately,
thus minimizing recompilation after changes.
In Objective Caml, compilation units are special cases of structures and
signatures, and the relationship between the units can be explained easily in
terms of the module system. A compilation unit A comprises two files:
- the implementation file A.ml, which contains a sequence of definitions,
analogous to the inside of a struct...end construct;
- the interface file A.mli, which contains a sequence of specifications,
analogous to the inside of a sig...end construct.
Both files define a structure named A as if the following definition was
entered at top-level:
<<
module A: sig (* contents of file A.mli *) end
= struct (* contents of file A.ml *) end;;
>>
The files defining the compilation units can be compiled separately using
the ocamlc -c command (the -c option means "compile only, do not try to link");
this produces compiled interface files (with extension .cmi) and compiled
object code files (with extension .cmo). When all units have been compiled,
their .cmo files are linked together using the ocaml command. For instance, the
following commands compile and link a program composed of two compilation units
Aux and Main:
<<$ ocamlc -c Aux.mli # produces aux.cmi
$ ocamlc -c Aux.ml # produces aux.cmo
$ ocamlc -c Main.mli # produces main.cmi
$ ocamlc -c Main.ml # produces main.cmo
$ ocamlc -o theprogram Aux.cmo Main.cmo
>>
The program behaves exactly as if the following phrases were entered at
top-level:
<<
module Aux: sig (* contents of Aux.mli *) end
= struct (* contents of Aux.ml *) end;;
module Main: sig (* contents of Main.mli *) end
= struct (* contents of Main.ml *) end;;
>>
In particular, Main can refer to Aux: the definitions and declarations
contained in Main.ml and Main.mli can refer to definition in Aux.ml, using the
Aux.ident notation, provided these definitions are exported in Aux.mli.
The order in which the .cmo files are given to ocaml during the linking phase
determines the order in which the module definitions occur. Hence, in the
example above, Aux appears first and Main can refer to it, but Aux cannot refer
to Main.
Notice that only top-level structures can be mapped to separately-compiled
files, but not functors nor module types. However, all module-class objects can
appear as components of a structure, so the solution is to put the functor or
module type inside a structure, which can then be mapped to a file.
Chapter 3 Objects in Caml
****************************
(Chapter written by Jérôme Vouillon, Didier Rémy and Jacques Garrigue)
This chapter gives an overview of the object-oriented features of Objective
Caml. Note that the relation between object, class and type in Objective Caml
is very different from that in main stream object-oriented languages like Java
or C++, so that you should not assume that similar keywords mean the same
thing.
3.1 Classes and objects
3.2 Immediate objects
3.3 Reference to self
3.4 Initializers
3.5 Virtual methods
3.6 Private methods
3.7 Class interfaces
3.8 Inheritance
3.9 Multiple inheritance
3.10 Parameterized classes
3.11 Polymorphic methods
3.12 Using coercions
3.13 Functional objects
3.14 Cloning objects
3.15 Recursive classes
3.16 Binary methods
3.17 Friends
3.1 Classes and objects
*=*=*=*=*=*=*=*=*=*=*=*=
The class point below defines one instance variable x and two methods get_x
and move. The initial value of the instance variable is 0. The variable x is
declared mutable, so the method move can change its value.
<<#class point =
# object
# val mutable x = 0
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
object val mutable x : int method get_x : int method move : int -> unit end
>>
We now create a new point p, instance of the point class.
<<#let p = new point;;
val p : point = <obj>
>>
Note that the type of p is point. This is an abbreviation automatically
defined by the class definition above. It stands for the object type <get_x :
int; move : int -> unit>, listing the methods of class point along with their
types.
We now invoke some methods to p:
<<#p#get_x;;
- : int = 0
#p#move 3;;
- : unit = ()
#p#get_x;;
- : int = 3
>>
The evaluation of the body of a class only takes place at object creation
time. Therefore, in the following example, the instance variable x is
initialized to different values for two different objects.
<<#let x0 = ref 0;;
val x0 : int ref = {contents = 0}
#class point =
# object
# val mutable x = incr x0; !x0
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
object val mutable x : int method get_x : int method move : int -> unit end
#new point#get_x;;
- : int = 1
#new point#get_x;;
- : int = 2
>>
The class point can also be abstracted over the initial values of the x
coordinate.
<<#class point = fun x_init ->
# object
# val mutable x = x_init
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
int ->
object val mutable x : int method get_x : int method move : int -> unit end
>>
Like in function definitions, the definition above can be abbreviated as:
<<#class point x_init =
# object
# val mutable x = x_init
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
int ->
object val mutable x : int method get_x : int method move : int -> unit end
>>
An instance of the class point is now a function that expects an initial
parameter to create a point object:
<<#new point;;
- : int -> point = <fun>
#let p = new point 7;;
val p : point = <obj>
>>
The parameter x_init is, of course, visible in the whole body of the
definition, including methods. For instance, the method get_offset in the class
below returns the position of the object relative to its initial position.
<<#class point x_init =
# object
# val mutable x = x_init
# method get_x = x
# method get_offset = x - x_init
# method move d = x <- x + d
# end;;
class point :
int ->
object
val mutable x : int
method get_offset : int
method get_x : int
method move : int -> unit
end
>>
Expressions can be evaluated and bound before defining the object body of
the class. This is useful to enforce invariants. For instance, points can be
automatically adjusted to the nearest point on a grid, as follows:
<<#class adjusted_point x_init =
# let origin = (x_init / 10) * 10 in
# object
# val mutable x = origin
# method get_x = x
# method get_offset = x - origin
# method move d = x <- x + d
# end;;
class adjusted_point :
int ->
object
val mutable x : int
method get_offset : int
method get_x : int
method move : int -> unit
end
>>
(One could also raise an exception if the x_init coordinate is not on the
grid.) In fact, the same effect could here be obtained by calling the
definition of class point with the value of the origin.
<<#class adjusted_point x_init = point ((x_init / 10) * 10);;
class adjusted_point : int -> point
>>
An alternative solution would have been to define the adjustment in a
special allocation function:
<<#let new_adjusted_point x_init = new point ((x_init / 10) * 10);;
val new_adjusted_point : int -> point = <fun>
>>
However, the former pattern is generally more appropriate, since the code
for adjustment is part of the definition of the class and will be inherited.
This ability provides class constructors as can be found in other languages.
Several constructors can be defined this way to build objects of the same class
but with different initialization patterns; an alternative is to use
initializers, as decribed below in section 3.4.
3.2 Immediate objects
*=*=*=*=*=*=*=*=*=*=*=
There is another, more direct way to create an object: create it without
going through a class.
The syntax is exactly the same as for class expressions, but the result is a
single object rather than a class. All the constructs described in the rest of
this section also apply to immediate objects.
<<#let p =
# object
# val mutable x = 0
# method get_x = x
# method move d = x <- x + d
# end;;
val p : < get_x : int; move : int -> unit > = <obj>
#p#get_x;;
- : int = 0
#p#move 3;;
- : unit = ()
#p#get_x;;
- : int = 3
>>
Unlike classes, which cannot be defined inside an expression, immediate
objects can appear anywhere, using variables from their environment.
<<#let minmax x y =
# if x < y then object method min = x method max = y end
# else object method min = y method max = x end;;
val minmax : 'a -> 'a -> < max : 'a; min : 'a > = <fun>
>>
Immediate objects have two weaknesses compared to classes: their types are
not abbreviated, and you cannot inherit from them. But these two weaknesses can
be advantages in some situations, as we will see in sections 3.3 and 3.10.
3.3 Reference to self
*=*=*=*=*=*=*=*=*=*=*=
A method or an initializer can send messages to self (that is, the current
object). For that, self must be explicitly bound, here to the variable s (s
could be any identifier, even though we will often choose the name self.)
<<#class printable_point x_init =
# object (s)
# val mutable x = x_init
# method get_x = x
# method move d = x <- x + d
# method print = print_int s#get_x
# end;;
class printable_point :
int ->
object
val mutable x : int
method get_x : int
method move : int -> unit
method print : unit
end
#let p = new printable_point 7;;
val p : printable_point = <obj>
#p#print;;
7- : unit = ()
>>
Dynamically, the variable s is bound at the invocation of a method. In
particular, when the class printable_point is inherited, the variable s will be
correctly bound to the object of the subclass.
A common problem with self is that, as its type may be extended in
subclasses, you cannot fix it in advance. Here is a simple example.
<<#let ints = ref [];;
val ints : '_a list ref = {contents = []}
#class my_int =
# object (self)
# method n = 1
# method register = ints := self :: !ints
# end;;
This expression has type < n : int; register : 'a; .. >
but is here used with type 'b
Self type cannot escape its class
>>
You can ignore the first two lines of the error message. What matters is the
last one: putting self into an external reference would make it impossible to
extend it afterwards. We will see in section 3.12 a workaround to this problem.
Note however that, since immediate objects are not extensible, the problem does
not occur with them.
<<#let my_int =
# object (self)
# method n = 1
# method register = ints := self :: !ints
# end;;
val my_int : < n : int; register : unit > = <obj>
>>
3.4 Initializers
*=*=*=*=*=*=*=*=*
Let-bindings within class definitions are evaluated before the object is
constructed. It is also possible to evaluate an expression immediately after
the object has been built. Such code is written as an anonymous hidden method
called an initializer. Therefore, is can access self and the instance
variables.
<<#class printable_point x_init =
# let origin = (x_init / 10) * 10 in
# object (self)
# val mutable x = origin
# method get_x = x
# method move d = x <- x + d
# method print = print_int self#get_x
# initializer print_string "new point at "; self#print; print_newline()
# end;;
class printable_point :
int ->
object
val mutable x : int
method get_x : int
method move : int -> unit
method print : unit
end
#let p = new printable_point 17;;
new point at 10
val p : printable_point = <obj>
>>
Initializers cannot be overridden. On the contrary, all initializers are
evaluated sequentially. Initializers are particularly useful to enforce
invariants. Another example can be seen in section 5.1.
3.5 Virtual methods
*=*=*=*=*=*=*=*=*=*=
It is possible to declare a method without actually defining it, using the
keyword virtual. This method will be provided later in subclasses. A class
containing virtual methods must be flagged virtual, and cannot be instantiated
(that is, no object of this class can be created). It still defines type
abbreviations (treating virtual methods as other methods.)
<<#class virtual abstract_point x_init =
# object (self)
# method virtual get_x : int
# method get_offset = self#get_x - x_init
# method virtual move : int -> unit
# end;;
class virtual abstract_point :
int ->
object
method get_offset : int
method virtual get_x : int
method virtual move : int -> unit
end
#class point x_init =
# object
# inherit abstract_point x_init
# val mutable x = x_init
# method get_x = x
# method move d = x <- x + d
# end;;
class point :
int ->
object
val mutable x : int
method get_offset : int
method get_x : int
method move : int -> unit
end
>>
Instance variables can also be declared as virtual, with the same effect as
with methods.
<<#class virtual abstract_point2 =
# object
# val mutable virtual x : int
# method move d = x <- x + d
# end;;
class virtual abstract_point2 :
object val mutable virtual x : int method move : int -> unit end
#class point2 x_init =
# object
# inherit abstract_point2
# val mutable x = x_init
# method get_offset = x - x_init
# end;;
class point2 :
int ->
object
val mutable x : int
method get_offset : int
method move : int -> unit
end
>>
3.6 Private methods
*=*=*=*=*=*=*=*=*=*=
Private methods are methods that do not appear in object interfaces. They can
only be invoked from other methods of the same object.
<<#class restricted_point x_init =
# object (self)
# val mutable x = x_init
# method get_x = x
# method private move d = x <- x + d
# method bump = self#move 1
# end;;
class restricted_point :
int ->
object
val mutable x : int
method bump : unit
method get_x : int
method private move : int -> unit
end
#let p = new restricted_point 0;;
val p : restricted_point = <obj>
#p#move 10;;
This expression has type restricted_point
It has no method move
#p#bump;;
- : unit = ()
>>
Note that this is not the same thing as private and protected methods in
Java or C++, which can be called from other objects of the same class. This is
a direct consequence of the independence between types and classes in Objective
Caml: two unrelated classes may produce objects of the same type, and there is
no way at the type level to ensure that an object comes from a specific class.
However a possible encoding of friend methods is given in section 3.17.
Private methods are inherited (they are by default visible in subclasses),
unless they are hidden by signature matching, as described below.
Private methods can be made public in a subclass.
<<#class point_again x =
# object (self)
# inherit restricted_point x
# method virtual move : _
# end;;
class point_again :
int ->
object
val mutable x : int
method bump : unit
method get_x : int
method move : int -> unit
end
>>
The annotation virtual here is only used to mention a method without
providing its definition. Since we didn't add the private annotation, this
makes the method public, keeping the original definition.
An alternative definition is
<<#class point_again x =
# object (self : < move : _; ..> )
# inherit restricted_point x
# end;;
class point_again :
int ->
object
val mutable x : int
method bump : unit
method get_x : int
method move : int -> unit
end
>>
The constraint on self's type is requiring a public move method, and this is
sufficient to override private.
One could think that a private method should remain private in a subclass.
However, since the method is visible in a subclass, it is always possible to
pick its code and define a method of the same name that runs that code, so yet
another (heavier) solution would be:
<<#class point_again x =
# object
# inherit restricted_point x as super
# method move = super#move
# end;;
class point_again :
int ->
object
val mutable x : int
method bump : unit
method get_x : int
method move : int -> unit
end
>>
Of course, private methods can also be virtual. Then, the keywords must
appear in this order method private virtual.
3.7 Class interfaces
*=*=*=*=*=*=*=*=*=*=*
Class interfaces are inferred from class definitions. They may also be
defined directly and used to restrict the type of a class. Like class
declarations, they also define a new type abbreviation.
<<#class type restricted_point_type =
# object
# method get_x : int
# method bump : unit
#end;;
class type restricted_point_type =
object method bump : unit method get_x : int end
#fun (x : restricted_point_type) -> x;;
- : restricted_point_type -> restricted_point_type = <fun>
>>
In addition to program documentation, class interfaces can be used to
constrain the type of a class. Both concrete instance variables and concrete
private methods can be hidden by a class type constraint. Public methods and
virtual members, however, cannot.
<<#class restricted_point' x = (restricted_point x : restricted_point_type);;
class restricted_point' : int -> restricted_point_type
>>
Or, equivalently:
<<#class restricted_point' = (restricted_point : int ->
restricted_point_type);;
class restricted_point' : int -> restricted_point_type
>>
The interface of a class can also be specified in a module signature, and
used to restrict the inferred signature of a module.
<<#module type POINT = sig
# class restricted_point' : int ->
# object
# method get_x : int
# method bump : unit
# end
#end;;
module type POINT =
sig
class restricted_point' :
int -> object method bump : unit method get_x : int end
end
#module Point : POINT = struct
# class restricted_point' = restricted_point
#end;;
module Point : POINT
>>
3.8 Inheritance
*=*=*=*=*=*=*=*=
We illustrate inheritance by defining a class of colored points that inherits
from the class of points. This class has all instance variables and all methods
of class point, plus a new instance variable c and a new method color.
<<#class colored_point x (c : string) =
# object
# inherit point x
# val c = c
# method color = c
# end;;
class colored_point :
int ->
string ->
object
val c : string
val mutable x : int
method color : string
method get_offset : int
method get_x : int
method move : int -> unit
end
#let p' = new colored_point 5 "red";;
val p' : colored_point = <obj>
#p'#get_x, p'#color;;
- : int * string = (5, "red")
>>
A point and a colored point have incompatible types, since a point has no
method color. However, the function get_x below is a generic function applying
method get_x to any object p that has this method (and possibly some others,
which are represented by an ellipsis in the type). Thus, it applies to both
points and colored points.
<<#let get_succ_x p = p#get_x + 1;;
val get_succ_x : < get_x : int; .. > -> int = <fun>
#get_succ_x p + get_succ_x p';;
- : int = 8
>>
Methods need not be declared previously, as shown by the example:
<<#let set_x p = p#set_x;;
val set_x : < set_x : 'a; .. > -> 'a = <fun>
#let incr p = set_x p (get_succ_x p);;
val incr : < get_x : int; set_x : int -> 'a; .. > -> 'a = <fun>
>>
3.9 Multiple inheritance
*=*=*=*=*=*=*=*=*=*=*=*=*
Multiple inheritance is allowed. Only the last definition of a method is
kept: the redefinition in a subclass of a method that was visible in the parent
class overrides the definition in the parent class. Previous definitions of a
method can be reused by binding the related ancestor. Below, super is bound to
the ancestor printable_point. The name super is a pseudo value identifier that
can only be used to invoke a super-class method, as in super#print.
<<#class printable_colored_point y c =
# object (self)
# val c = c
# method color = c
# inherit printable_point y as super
# method print =
# print_string "(";
# super#print;
# print_string ", ";
# print_string (self#color);
# print_string ")"
# end;;
class printable_colored_point :
int ->
string ->
object
val c : string
val mutable x : int
method color : string
method get_x : int
method move : int -> unit
method print : unit
end
#let p' = new printable_colored_point 17 "red";;
new point at (10, red)
val p' : printable_colored_point = <obj>
#p'#print;;
(10, red)- : unit = ()
>>
A private method that has been hidden in the parent class is no longer
visible, and is thus not overridden. Since initializers are treated as private
methods, all initializers along the class hierarchy are evaluated, in the order
they are introduced.
3.10 Parameterized classes
*=*=*=*=*=*=*=*=*=*=*=*=*=*
Reference cells can be implemented as objects. The naive definition fails to
typecheck:
<<#class ref x_init =
# object
# val mutable x = x_init
# method get = x
# method set y = x <- y
# end;;
Some type variables are unbound in this type:
class ref :
'a ->
object val mutable x : 'a method get : 'a method set : 'a -> unit end
The method get has type 'a where 'a is unbound
>>
The reason is that at least one of the methods has a polymorphic type (here,
the type of the value stored in the reference cell), thus either the class
should be parametric, or the method type should be constrained to a monomorphic
type. A monomorphic instance of the class could be defined by:
<<#class ref (x_init:int) =
# object
# val mutable x = x_init
# method get = x
# method set y = x <- y
# end;;
class ref :
int ->
object val mutable x : int method get : int method set : int -> unit end
>>
Note that since immediate objects do not define a class type, the have no
such restriction.
<<#let new_ref x_init =
# object
# val mutable x = x_init
# method get = x
# method set y = x <- y
# end;;
val new_ref : 'a -> < get : 'a; set : 'a -> unit > = <fun>
>>
On the other hand, a class for polymorphic references must explicitly list
the type parameters in its declaration. Class type parameters are always listed
between [ and ]. The type parameters must also be bound somewhere in the class
body by a type constraint.
<<#class ['a] ref x_init =
# object
# val mutable x = (x_init : 'a)
# method get = x
# method set y = x <- y
# end;;
class ['a] ref :
'a -> object val mutable x : 'a method get : 'a method set : 'a -> unit end
#let r = new ref 1 in r#set 2; (r#get);;
- : int = 2
>>
The type parameter in the declaration may actually be constrained in the
body of the class definition. In the class type, the actual value of the type
parameter is displayed in the constraint clause.
<<#class ['a] ref_succ (x_init:'a) =
# object
# val mutable x = x_init + 1
# method get = x
# method set y = x <- y
# end;;
class ['a] ref_succ :
'a ->
object
constraint 'a = int
val mutable x : int
method get : int
method set : int -> unit
end
>>
Let us consider a more complex example: define a circle, whose center may be
any kind of point. We put an additional type constraint in method move, since
no free variables must remain unaccounted for by the class type parameters.
<<#class ['a] circle (c : 'a) =
# object
# val mutable center = c
# method center = center
# method set_center c = center <- c
# method move = (center#move : int -> unit)
# end;;
class ['a] circle :
'a ->
object
constraint 'a = < move : int -> unit; .. >
val mutable center : 'a
method center : 'a
method move : int -> unit
method set_center : 'a -> unit
end
>>
An alternate definition of circle, using a constraint clause in the class
definition, is shown below. The type #point used below in the constraint clause
is an abbreviation produced by the definition of class point. This abbreviation
unifies with the type of any object belonging to a subclass of class point. It
actually expands to < get_x : int; move : int -> unit; .. >. This leads to the
following alternate definition of circle, which has slightly stronger
constraints on its argument, as we now expect center to have a method get_x.
<<#class ['a] circle (c : 'a) =
# object
# constraint 'a = #point
# val mutable center = c
# method center = center
# method set_center c = center <- c
# method move = center#move
# end;;
class ['a] circle :
'a ->
object
constraint 'a = #point
val mutable center : 'a
method center : 'a
method move : int -> unit
method set_center : 'a -> unit
end
>>
The class colored_circle is a specialized version of class circle that
requires the type of the center to unify with #colored_point, and adds a method
color. Note that when specializing a parameterized class, the instance of type
parameter must always be explicitly given. It is again written between [ and ].
<<#class ['a] colored_circle c =
# object
# constraint 'a = #colored_point
# inherit ['a] circle c
# method color = center#color
# end;;
class ['a] colored_circle :
'a ->
object
constraint 'a = #colored_point
val mutable center : 'a
method center : 'a
method color : string
method move : int -> unit
method set_center : 'a -> unit
end
>>
3.11 Polymorphic methods
*=*=*=*=*=*=*=*=*=*=*=*=*
While parameterized classes may be polymorphic in their contents, they are
not enough to allow polymorphism of method use.
A classical example is defining an iterator.
<<#List.fold_left;;
- : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a = <fun>
#class ['a] intlist (l : int list) =
# object
# method empty = (l = [])
# method fold f (accu : 'a) = List.fold_left f accu l
# end;;
class ['a] intlist :
int list ->
object method empty : bool method fold : ('a -> int -> 'a) -> 'a -> 'a end
>>
At first look, we seem to have a polymorphic iterator, however this does not
work in practice.
<<#let l = new intlist [1; 2; 3];;
val l : '_a intlist = <obj>
#l#fold (fun x y -> x+y) 0;;
- : int = 6
#l;;
- : int intlist = <obj>
#l#fold (fun s x -> s ^ string_of_int x ^ " ") "";;
This expression has type int but is here used with type string
>>
Our iterator works, as shows its first use for summation. However, since
objects themselves are not polymorphic (only their constructors are), using the
fold method fixes its type for this individual object. Our next attempt to use
it as a string iterator fails.
The problem here is that quantification was wrongly located: this is not the
class we want to be polymorphic, but the fold method. This can be achieved by
giving an explicitly polymorphic type in the method definition.
<<#class intlist (l : int list) =
# object
# method empty = (l = [])
# method fold : 'a. ('a -> int -> 'a) -> 'a -> 'a =
# fun f accu -> List.fold_left f accu l
# end;;
class intlist :
int list ->
object method empty : bool method fold : ('a -> int -> 'a) -> 'a -> 'a end
#let l = new intlist [1; 2; 3];;
val l : intlist = <obj>
#l#fold (fun x y -> x+y) 0;;
- : int = 6
#l#fold (fun s x -> s ^ string_of_int x ^ " ") "";;
- : string = "1 2 3 "
>>
As you can see in the class type shown by the compiler, while polymorphic
method types must be fully explicit in class definitions (appearing immediately
after the method name), quantified type variables can be left implicit in class
descriptions. Why require types to be explicit? The problem is that (int -> int
-> int) -> int -> int would also be a valid type for fold, and it happens to be
incompatible with the polymorphic type we gave (automatic instantiation only
works for toplevel types variables, not for inner quantifiers, where it becomes
an undecidable problem.) So the compiler cannot choose between those two types,
and must be helped.
However, the type can be completely omitted in the class definition if it is
already known, through inheritance or type constraints on self. Here is an
example of method overriding.
<<#class intlist_rev l =
# object
# inherit intlist l
# method fold f accu = List.fold_left f accu (List.rev l)
# end;;
>>
The following idiom separates description and definition.
<<#class type ['a] iterator =
# object method fold : ('b -> 'a -> 'b) -> 'b -> 'b end;;
#class intlist l =
# object (self : int #iterator)
# method empty = (l = [])
# method fold f accu = List.fold_left f accu l
# end;;
>>
Note here the (self : int #iterator) idiom, which ensures that this object
implements the interface iterator.
Polymorphic methods are called in exactly the same way as normal methods, but
you should be aware of some limitations of type inference. Namely, a
polymorphic method can only be called if its type is known at the call site.
Otherwise, the method will be assumed to be monomorphic, and given an
incompatible type.
<<#let sum lst = lst#fold (fun x y -> x+y) 0;;
val sum : < fold : (int -> int -> int) -> int -> 'a; .. > -> 'a = <fun>
#sum l;;
This expression has type intlist but is here used with type
< fold : (int -> int -> int) -> int -> 'a; .. >
Types for method fold are incompatible
>>
The workaround is easy: you should put a type constraint on the parameter.
<<#let sum (lst : _ #iterator) = lst#fold (fun x y -> x+y) 0;;
val sum : int #iterator -> int = <fun>
>>
Of course the constraint may also be an explicit method type. Only
occurences of quantified variables are required.
<<#let sum lst =
# (lst : < fold : 'a. ('a -> _ -> 'a) -> 'a -> 'a; .. >)#fold (+) 0;;
val sum : < fold : 'a. ('a -> int -> 'a) -> 'a -> 'a; .. > -> int = <fun>
>>
Another use of polymorphic methods is to allow some form of implicit
subtyping in method arguments. We have already seen in section 3.8 how some
functions may be polymorphic in the class of their argument. This can be
extended to methods.
<<#class type point0 = object method get_x : int end;;
class type point0 = object method get_x : int end
#class distance_point x =
# object
# inherit point x
# method distance : 'a. (#point0 as 'a) -> int =
# fun other -> abs (other#get_x - x)
# end;;
class distance_point :
int ->
object
val mutable x : int
method distance : #point0 -> int
method get_offset : int
method get_x : int
method move : int -> unit
end
#let p = new distance_point 3 in
#(p#distance (new point 8), p#distance (new colored_point 1 "blue"));;
- : int * int = (5, 2)
>>
Note here the special syntax (#point0 as 'a) we have to use to quantify the
extensible part of #point0. As for the variable binder, it can be omitted in
class specifications. If you want polymorphism inside object field it must be
quantified independently.
<<#class multi_poly =
# object
# method m1 : 'a. (< n1 : 'b. 'b -> 'b; .. > as 'a) -> _ =
# fun o -> o#n1 true, o#n1 "hello"
# method m2 : 'a 'b. (< n2 : 'b -> bool; .. > as 'a) -> 'b -> _ =
# fun o x -> o#n2 x
# end;;
class multi_poly :
object
method m1 : < n1 : 'a. 'a -> 'a; .. > -> bool * string
method m2 : < n2 : 'b -> bool; .. > -> 'b -> bool
end
>>
In method m1, o must be an object with at least a method n1, itself
polymorphic. In method m2, the argument of n2 and x must have the same type,
which is quantified at the same level as 'a.
3.12 Using coercions
*=*=*=*=*=*=*=*=*=*=*
Subtyping is never implicit. There are, however, two ways to perform
subtyping. The most general construction is fully explicit: both the domain and
the codomain of the type coercion must be given.
We have seen that points and colored points have incompatible types. For
instance, they cannot be mixed in the same list. However, a colored point can
be coerced to a point, hiding its color method:
<<#let colored_point_to_point cp = (cp : colored_point :> point);;
val colored_point_to_point : colored_point -> point = <fun>
#let p = new point 3 and q = new colored_point 4 "blue";;
val p : point = <obj>
val q : colored_point = <obj>
#let l = [p; (colored_point_to_point q)];;
val l : point list = [<obj>; <obj>]
>>
An object of type t can be seen as an object of type t' only if t is a
subtype of t'. For instance, a point cannot be seen as a colored point.
<<#(p : point :> colored_point);;
Type point = < get_offset : int; get_x : int; move : int -> unit >
is not a subtype of type
colored_point =
< color : string; get_offset : int; get_x : int; move : int -> unit >
>>
Indeed, narrowing coercions without runtime checks would be unsafe. Runtime
type checks might raise exceptions, and they would require the presence of type
information at runtime, which is not the case in the Objective Caml system. For
these reasons, there is no such operation available in the language.
Be aware that subtyping and inheritance are not related. Inheritance is a
syntactic relation between classes while subtyping is a semantic relation
between types. For instance, the class of colored points could have been
defined directly, without inheriting from the class of points; the type of
colored points would remain unchanged and thus still be a subtype of points.
The domain of a coercion can often be omitted. For instance, one can define:
<<#let to_point cp = (cp :> point);;
val to_point : #point -> point = <fun>
>>
In this case, the function colored_point_to_point is an instance of the
function to_point. This is not always true, however. The fully explicit
coercion is more precise and is sometimes unavoidable. Consider, for example,
the following class:
<<#class c0 = object method m = {< >} method n = 0 end;;
class c0 : object ('a) method m : 'a method n : int end
>>
The object type c0 is an abbreviation for <m : 'a; n : int> as 'a. Consider
now the type declaration:
<<#class type c1 = object method m : c1 end;;
class type c1 = object method m : c1 end
>>
The object type c1 is an abbreviation for the type <m : 'a> as 'a. The
coercion from an object of type c0 to an object of type c1 is correct:
<<#fun (x:c0) -> (x : c0 :> c1);;
- : c0 -> c1 = <fun>
>>
However, the domain of the coercion cannot be omitted here:
<<#fun (x:c0) -> (x :> c1);;
This expression cannot be coerced to type c1 = < m : c1 >; it has type
c0 = < m : c0; n : int >
but is here used with type < m : #c1 as 'a; .. >
Type c0 = < m : c0; n : int > is not compatible with type 'a = < m : c1; .. >
Type c0 = < m : c0; n : int > is not compatible with type c1 = < m : c1 >
The second object type has no method n.
This simple coercion was not fully general. Consider using a double coercion.
>>
The solution is to use the explicit form. Sometimes, a change in the
class-type definition can also solve the problem
<<#class type c2 = object ('a) method m : 'a end;;
class type c2 = object ('a) method m : 'a end
#fun (x:c0) -> (x :> c2);;
- : c0 -> c2 = <fun>
>>
While class types c1 and c2 are different, both object types c1 and c2
expand to the same object type (same method names and types). Yet, when the
domain of a coercion is left implicit and its co-domain is an abbreviation of a
known class type, then the class type, rather than the object type, is used to
derive the coercion function. This allows to leave the domain implicit in most
cases when coercing form a subclass to its superclass. The type of a coercion
can always be seen as below:
<<#let to_c1 x = (x :> c1);;
val to_c1 : < m : #c1; .. > -> c1 = <fun>
#let to_c2 x = (x :> c2);;
val to_c2 : #c2 -> c2 = <fun>
>>
Note the difference between the two coercions: in the second case, the type
#c2 = < m : 'a; .. > as 'a is polymorphically recursive (according to the
explicit recursion in the class type of c2); hence the success of applying this
coercion to an object of class c0. On the other hand, in the first case, c1 was
only expanded and unrolled twice to obtain < m : < m : c1; .. >; .. > (remember
#c1 = < m : c1; .. >), without introducing recursion. You may also note that
the type of to_c2 is #c2 -> c2 while the type of to_c1 is more general than #c1
-> c1. This is not always true, since there are class types for which some
instances of #c are not subtypes of c, as explained in section 3.16. Yet, for
parameterless classes the coercion (_ :> c) is always more general than (_ : #c
:> c).
A common problem may occur when one tries to define a coercion to a class c
while defining class c. The problem is due to the type abbreviation not being
completely defined yet, and so its subtypes are not clearly known. Then, a
coercion (_ :> c) or (_ : #c :> c) is taken to be the identity function, as in
<<#function x -> (x :> 'a);;
- : 'a -> 'a = <fun>
>>
As a consequence, if the coercion is applied to self, as in the following
example, the type of self is unified with the closed type c (a closed object
type is an object type without ellipsis). This would constrain the type of self
be closed and is thus rejected. Indeed, the type of self cannot be closed: this
would prevent any further extension of the class. Therefore, a type error is
generated when the unification of this type with another type would result in a
closed object type.
<<#class c = object method m = 1 end
#and d = object (self)
# inherit c
# method n = 2
# method as_c = (self :> c)
#end;;
This expression cannot be coerced to type c = < m : int >; it has type
< as_c : c; m : int; n : int; .. >
but is here used with type c
Self type cannot be unified with a closed object type
>>
However, the most common instance of this problem, coercing self to its
current class, is detected as a special case by the type checker, and properly
typed.
<<#class c = object (self) method m = (self :> c) end;;
class c : object method m : c end
>>
This allows the following idiom, keeping a list of all objects belonging to
a class or its subclasses:
<<#let all_c = ref [];;
val all_c : '_a list ref = {contents = []}
#class c (m : int) =
# object (self)
# method m = m
# initializer all_c := (self :> c) :: !all_c
# end;;
class c : int -> object method m : int end
>>
This idiom can in turn be used to retrieve an object whose type has been
weakened:
<<#let rec lookup_obj obj = function [] -> raise Not_found
# | obj' :: l ->
# if (obj :> < >) = (obj' :> < >) then obj' else lookup_obj obj l ;;
val lookup_obj : < .. > -> (< .. > as 'a) list -> 'a = <fun>
#let lookup_c obj = lookup_obj obj !all_c;;
val lookup_c : < .. > -> < m : int > = <fun>
>>
The type < m : int > we see here is just the expansion of c, due to the use
of a reference; we have succeeded in getting back an object of type c.
The previous coercion problem can often be avoided by first defining the
abbreviation, using a class type:
<<#class type c' = object method m : int end;;
class type c' = object method m : int end
#class c : c' = object method m = 1 end
#and d = object (self)
# inherit c
# method n = 2
# method as_c = (self :> c')
#end;;
class c : c'
and d : object method as_c : c' method m : int method n : int end
>>
It is also possible to use a virtual class. Inheriting from this class
simultaneously allows to enforce all methods of c to have the same type as the
methods of c'.
<<#class virtual c' = object method virtual m : int end;;
class virtual c' : object method virtual m : int end
#class c = object (self) inherit c' method m = 1 end;;
class c : object method m : int end
>>
One could think of defining the type abbreviation directly:
<<#type c' = <m : int>;;
>>
However, the abbreviation #c' cannot be defined directly in a similar way.
It can only be defined by a class or a class-type definition. This is because
# sharp abbreviations carry an implicit anonymous variable .. that cannot be
explicitly named. The closer you get to it is:
<<#type 'a c'_class = 'a constraint 'a = < m : int; .. >;;
>>
with an extra type variable capturing the open object type.
3.13 Functional objects
*=*=*=*=*=*=*=*=*=*=*=*=
It is possible to write a version of class point without assignments on the
instance variables. The construct {< ... >} returns a copy of "self" (that is,
the current object), possibly changing the value of some instance variables.
<<#class functional_point y =
# object
# val x = y
# method get_x = x
# method move d = {< x = x + d >}
# end;;
class functional_point :
int ->
object ('a) val x : int method get_x : int method move : int -> 'a end
#let p = new functional_point 7;;
val p : functional_point = <obj>
#p#get_x;;
- : int = 7
#(p#move 3)#get_x;;
- : int = 10
#p#get_x;;
- : int = 7
>>
Note that the type abbreviation functional_point is recursive, which can be
seen in the class type of functional_point: the type of self is 'a and 'a
appears inside the type of the method move.
The above definition of functional_point is not equivalent to the following:
<<#class bad_functional_point y =
# object
# val x = y
# method get_x = x
# method move d = new bad_functional_point (x+d)
# end;;
class bad_functional_point :
int ->
object
val x : int
method get_x : int
method move : int -> bad_functional_point
end
>>
While objects of either class will behave the same, objects of their
subclasses will be different. In a subclass of the latter, the method move will
keep returning an object of the parent class. On the contrary, in a subclass of
the former, the method move will return an object of the subclass.
Functional update is often used in conjunction with binary methods as
illustrated in section 5.2.1.
3.14 Cloning objects
*=*=*=*=*=*=*=*=*=*=*
Objects can also be cloned, whether they are functional or imperative. The
library function Oo.copy makes a shallow copy of an object. That is, it
returns an object that is equal to the previous one. The instance variables
have been copied but their contents are shared. Assigning a new value to an
instance variable of the copy (using a method call) will not affect instance
variables of the original, and conversely. A deeper assignment (for example if
the instance variable if a reference cell) will of course affect both the
original and the copy.
The type of Oo.copy is the following:
<<#Oo.copy;;
- : (< .. > as 'a) -> 'a = <fun>
>>
The keyword as in that type binds the type variable 'a to the object type <
.. >. Therefore, Oo.copy takes an object with any methods (represented by the
ellipsis), and returns an object of the same type. The type of Oo.copy is
different from type < .. > -> < .. > as each ellipsis represents a different
set of methods. Ellipsis actually behaves as a type variable.
<<#let p = new point 5;;
val p : point = <obj>
#let q = Oo.copy p;;
val q : point = <obj>
#q#move 7; (p#get_x, q#get_x);;
- : int * int = (5, 12)
>>
In fact, Oo.copy p will behave as p#copy assuming that a public method copy
with body {< >} has been defined in the class of p.
Objects can be compared using the generic comparison functions = and <>. Two
objects are equal if and only if they are physically equal. In particular, an
object and its copy are not equal.
<<#let q = Oo.copy p;;
val q : point = <obj>
#p = q, p = p;;
- : bool * bool = (false, true)
>>
Other generic comparissons such as (<, <=,...) can also be used on objects.
The relation < defines an unspecified but strict ordering on objets. The
ordering relationship between two objects is fixed once for all after the two
objects have been created and it is not affected by mutation of fields.
Cloning and override have a non empty intersection. They are interchangeable
when used within an object and without overriding any field:
<<#class copy =
# object
# method copy = {< >}
# end;;
class copy : object ('a) method copy : 'a end
#class copy =
# object (self)
# method copy = Oo.copy self
# end;;
class copy : object ('a) method copy : 'a end
>>
Only the override can be used to actually override fields, and only the
Oo.copy primitive can be used externally.
Cloning can also be used to provide facilities for saving and restoring the
state of objects.
<<#class backup =
# object (self : 'mytype)
# val mutable copy = None
# method save = copy <- Some {< copy = None >}
# method restore = match copy with Some x -> x | None -> self
# end;;
class backup :
object ('a)
val mutable copy : 'a option
method restore : 'a
method save : unit
end
>>
The above definition will only backup one level. The backup facility can be
added to any class using multiple inheritance.
<<#class ['a] backup_ref x = object inherit ['a] ref x inherit backup end;;
class ['a] backup_ref :
'a ->
object ('b)
val mutable copy : 'b option
val mutable x : 'a
method get : 'a
method restore : 'b
method save : unit
method set : 'a -> unit
end
#let rec get p n = if n = 0 then p # get else get (p # restore) (n-1);;
val get : (< get : 'b; restore : 'a; .. > as 'a) -> int -> 'b = <fun>
#let p = new backup_ref 0 in
#p # save; p # set 1; p # save; p # set 2;
#[get p 0; get p 1; get p 2; get p 3; get p 4];;
- : int list = [2; 1; 1; 1; 1]
>>
A variant of backup could retain all copies. (We then add a method clear to
manually erase all copies.)
<<#class backup =
# object (self : 'mytype)
# val mutable copy = None
# method save = copy <- Some {< >}
# method restore = match copy with Some x -> x | None -> self
# method clear = copy <- None
# end;;
class backup :
object ('a)
val mutable copy : 'a option
method clear : unit
method restore : 'a
method save : unit
end
>>
<<#class ['a] backup_ref x = object inherit ['a] ref x inherit backup end;;
class ['a] backup_ref :
'a ->
object ('b)
val mutable copy : 'b option
val mutable x : 'a
method clear : unit
method get : 'a
method restore : 'b
method save : unit
method set : 'a -> unit
end
#let p = new backup_ref 0 in
#p # save; p # set 1; p # save; p # set 2;
#[get p 0; get p 1; get p 2; get p 3; get p 4];;
- : int list = [2; 1; 0; 0; 0]
>>
3.15 Recursive classes
*=*=*=*=*=*=*=*=*=*=*=*
Recursive classes can be used to define objects whose types are mutually
recursive.
<<#class window =
# object
# val mutable top_widget = (None : widget option)
# method top_widget = top_widget
# end
#and widget (w : window) =
# object
# val window = w
# method window = window
# end;;
class window :
object
val mutable top_widget : widget option
method top_widget : widget option
end
and widget : window -> object val window : window method window : window end
>>
Although their types are mutually recursive, the classes widget and window
are themselves independent.
3.16 Binary methods
*=*=*=*=*=*=*=*=*=*=
A binary method is a method which takes an argument of the same type as self.
The class comparable below is a template for classes with a binary method leq
of type 'a -> bool where the type variable 'a is bound to the type of self.
Therefore, #comparable expands to < leq : 'a -> bool; .. > as 'a. We see here
that the binder as also allows to write recursive types.
<<#class virtual comparable =
# object (_ : 'a)
# method virtual leq : 'a -> bool
# end;;
class virtual comparable : object ('a) method virtual leq : 'a -> bool end
>>
We then define a subclass money of comparable. The class money simply wraps
floats as comparable objects. We will extend it below with more operations.
There is a type constraint on the class parameter x as the primitive <= is a
polymorphic comparison function in Objective Caml. The inherit clause ensures
that the type of objects of this class is an instance of #comparable.
<<#class money (x : float) =
# object
# inherit comparable
# val repr = x
# method value = repr
# method leq p = repr <= p#value
# end;;
class money :
float ->
object ('a)
val repr : float
method leq : 'a -> bool
method value : float
end
>>
Note that the type money1 is not a subtype of type comparable, as the self
type appears in contravariant position in the type of method leq. Indeed, an
object m of class money has a method leq that expects an argument of type money
since it accesses its value method. Considering m of type comparable would
allow to call method leq on m with an argument that does not have a method
value, which would be an error.
Similarly, the type money2 below is not a subtype of type money.
<<#class money2 x =
# object
# inherit money x
# method times k = {< repr = k *. repr >}
# end;;
class money2 :
float ->
object ('a)
val repr : float
method leq : 'a -> bool
method times : float -> 'a
method value : float
end
>>
It is however possible to define functions that manipulate objects of type
either money or money2: the function min will return the minimum of any two
objects whose type unifies with #comparable. The type of min is not the same as
#comparable -> #comparable -> #comparable, as the abbreviation #comparable
hides a type variable (an ellipsis). Each occurrence of this abbreviation
generates a new variable.
<<#let min (x : #comparable) y =
# if x#leq y then x else y;;
val min : (#comparable as 'a) -> 'a -> 'a = <fun>
>>
This function can be applied to objects of type money or money2.
<<#(min (new money 1.3) (new money 3.1))#value;;
- : float = 1.3
#(min (new money2 5.0) (new money2 3.14))#value;;
- : float = 3.14
>>
More examples of binary methods can be found in sections 5.2.1 and 5.2.3.
Notice the use of functional update for method times. Writing new money2 (k
*. repr) instead of {< repr = k *. repr >} would not behave well with
inheritance: in a subclass money3 of money2 the times method would return an
object of class money2 but not of class money3 as would be expected.
The class money could naturally carry another binary method. Here is a direct
definition:
<<#class money x =
# object (self : 'a)
# val repr = x
# method value = repr
# method print = print_float repr
# method times k = {< repr = k *. x >}
# method leq (p : 'a) = repr <= p#value
# method plus (p : 'a) = {< repr = x +. p#value >}
# end;;
class money :
float ->
object ('a)
val repr : float
method leq : 'a -> bool
method plus : 'a -> 'a
method print : unit
method times : float -> 'a
method value : float
end
>>
3.17 Friends
*=*=*=*=*=*=*
The above class money reveals a problem that often occurs with binary
methods. In order to interact with other objects of the same class, the
representation of money objects must be revealed, using a method such as value.
If we remove all binary methods (here plus and leq), the representation can
easily be hidden inside objects by removing the method value as well. However,
this is not possible as long as some binary requires access to the
representation on object of the same class but different from self.
<<#class safe_money x =
# object (self : 'a)
# val repr = x
# method print = print_float repr
# method times k = {< repr = k *. x >}
# end;;
class safe_money :
float ->
object ('a)
val repr : float
method print : unit
method times : float -> 'a
end
>>
Here, the representation of the object is known only to a particular object.
To make it available to other objects of the same class, we are forced to make
it available to the whole world. However we can easily restrict the visibility
of the representation using the module system.
<<#module type MONEY =
# sig
# type t
# class c : float ->
# object ('a)
# val repr : t
# method value : t
# method print : unit
# method times : float -> 'a
# method leq : 'a -> bool
# method plus : 'a -> 'a
# end
# end;;
#module Euro : MONEY =
# struct
# type t = float
# class c x =
# object (self : 'a)
# val repr = x
# method value = repr
# method print = print_float repr
# method times k = {< repr = k *. x >}
# method leq (p : 'a) = repr <= p#value
# method plus (p : 'a) = {< repr = x +. p#value >}
# end
# end;;
>>
Another example of friend functions may be found in section 5.2.3. These
examples occur when a group of objects (here objects of the same class) and
functions should see each others internal representation, while their
representation should be hidden from the outside. The solution is always to
define all friends in the same module, give access to the representation and
use a signature constraint to make the representation abstract outside of the
module.
Chapter 4 Labels and variants
********************************
(Chapter written by Jacques Garrigue)
This chapter gives an overview of the new features in Objective Caml 3:
labels, and polymorphic variants.
4.1 Labels
*=*=*=*=*=*
If you have a look at modules ending in Labels in the standard library, you
will see that function types have annotations you did not have in the functions
you defined yourself.
<<#ListLabels.map;;
- : f:('a -> 'b) -> 'a list -> 'b list = <fun>
#StringLabels.sub;;
- : string -> pos:int -> len:int -> string = <fun>
>>
Such annotations of the form name: are called labels. They are meant to
document the code, allow more checking, and give more flexibility to function
application. You can give such names to arguments in your programs, by
prefixing them with a tilde ~.
<<#let f ~x ~y = x - y;;
val f : x:int -> y:int -> int = <fun>
#let x = 3 and y = 2 in f ~x ~y;;
- : int = 1
>>
When you want to use distinct names for the variable and the label appearing
in the type, you can use a naming label of the form ~name:. This also applies
when the argument is not a variable.
<<#let f ~x:x1 ~y:y1 = x1 - y1;;
val f : x:int -> y:int -> int = <fun>
#f ~x:3 ~y:2;;
- : int = 1
>>
Labels obey the same rules as other identifiers in Caml, that is you cannot
use a reserved keyword (like in or to) as label.
Formal parameters and arguments are matched according to their respective
labels (1), the absence of label being interpreted as the empty label. This
allows commuting arguments in applications. One can also partially apply a
function on any argument, creating a new function of the remaining parameters.
<<#let f ~x ~y = x - y;;
val f : x:int -> y:int -> int = <fun>
#f ~y:2 ~x:3;;
- : int = 1
#ListLabels.fold_left;;
- : f:('a -> 'b -> 'a) -> init:'a -> 'b list -> 'a = <fun>
#ListLabels.fold_left [1;2;3] ~init:0 ~f:(+);;
- : int = 6
#ListLabels.fold_left ~init:0;;
- : f:(int -> 'a -> int) -> 'a list -> int = <fun>
>>
If in a function several arguments bear the same label (or no label), they
will not commute among themselves, and order matters. But they can still
commute with other arguments.
<<#let hline ~x:x1 ~x:x2 ~y = (x1, x2, y);;
val hline : x:'a -> x:'b -> y:'c -> 'a * 'b * 'c = <fun>
#hline ~x:3 ~y:2 ~x:5;;
- : int * int * int = (3, 5, 2)
>>
As an exception to the above parameter matching rules, if an application is
total, labels may be omitted. In practice, most applications are total, so that
labels can be omitted in applications.
<<#f 3 2;;
- : int = 1
#ListLabels.map succ [1;2;3];;
- : int list = [2; 3; 4]
>>
But beware that functions like ListLabels.fold_left whose result type is a
type variable will never be considered as totally applied.
<<#ListLabels.fold_left (+) 0 [1;2;3];;
This expression has type int -> int -> int but is here used with type 'a list
>>
When a function is passed as an argument to an higher-order function, labels
must match in both types. Neither adding nor removing labels are allowed.
<<#let h g = g ~x:3 ~y:2;;
val h : (x:int -> y:int -> 'a) -> 'a = <fun>
#h f;;
- : int = 1
#h (+);;
This expression has type int -> int -> int but is here used with type
x:int -> y:int -> 'a
>>
Note that when you don't need an argument, you can still use a wildcard
pattern, but you must prefix it with the label.
<<#h (fun ~x:_ ~y -> y+1);;
- : int = 3
>>
4.1.1 Optional arguments
=========================
An interesting feature of labeled arguments is that they can be made
optional. For optional parameters, the question mark ? replaces the tilde ~ of
non-optional ones, and the label is also prefixed by ? in the function type.
Default values may be given for such optional parameters.
<<#let bump ?(step = 1) x = x + step;;
val bump : ?step:int -> int -> int = <fun>
#bump 2;;
- : int = 3
#bump ~step:3 2;;
- : int = 5
>>
A function taking some optional arguments must also take at least one
non-labeled argument. This is because the criterion for deciding whether an
optional has been omitted is the application on a non-labeled argument
appearing after this optional argument in the function type.
<<#let test ?(x = 0) ?(y = 0) () ?(z = 0) () = (x, y, z);;
val test : ?x:int -> ?y:int -> unit -> ?z:int -> unit -> int * int * int =
<fun>
#test ();;
- : ?z:int -> unit -> int * int * int = <fun>
#test ~x:2 () ~z:3 ();;
- : int * int * int = (2, 0, 3)
>>
Optional parameters may also commute with non-optional or unlabelled ones, as
long as they are applied simultaneously. By nature, optional arguments do not
commute with unlabeled arguments applied independently.
<<#test ~y:2 ~x:3 () ();;
- : int * int * int = (3, 2, 0)
#test () () ~z:1 ~y:2 ~x:3;;
- : int * int * int = (3, 2, 1)
#(test () ()) ~z:1;;
This expression is not a function, it cannot be applied
>>
Here (test () ()) is already (0,0,0) and cannot be further applied.
Optional arguments are actually implemented as option types. If you do not
give a default value, you have access to their internal representation, type 'a
option = None | Some of 'a. You can then provide different behaviors when an
argument is present or not.
<<#let bump ?step x =
# match step with
# | None -> x * 2
# | Some y -> x + y
#;;
val bump : ?step:int -> int -> int = <fun>
>>
It may also be useful to relay an optional argument from a function call to
another. This can be done by prefixing the applied argument with ?. This
question mark disables the wrapping of optional argument in an option type.
<<#let test2 ?x ?y () = test ?x ?y () ();;
val test2 : ?x:int -> ?y:int -> unit -> int * int * int = <fun>
#test2 ?x:None;;
- : ?y:int -> unit -> int * int * int = <fun>
>>
4.1.2 Labels and type inference
================================
While they provide an increased comfort for writing function applications,
labels and optional arguments have the pitfall that they cannot be inferred as
completely as the rest of the language.
You can see it in the following two examples.
<<#let h' g = g ~y:2 ~x:3;;
val h' : (y:int -> x:int -> 'a) -> 'a = <fun>
#h' f;;
This expression has type x:int -> y:int -> int but is here used with type
y:int -> x:int -> 'a
#let bump_it bump x =
# bump ~step:2 x;;
val bump_it : (step:int -> 'a -> 'b) -> 'a -> 'b = <fun>
#bump_it bump 1;;
This expression has type ?step:int -> int -> int but is here used with type
step:int -> 'a -> 'b
>>
The first case is simple: g is passed ~y and then ~x, but f expects ~x and
then ~y. This is correctly handled if we know the type of g to be x:int ->
y:int -> int in advance, but otherwise this causes the above type clash. The
simplest workaround is to apply formal parameters in a standard order.
The second example is more subtle: while we intended the argument bump to be
of type ?step:int -> int -> int, it is inferred as step:int -> int -> 'a. These
two types being incompatible (internally normal and optional arguments are
different), a type error occurs when applying bump_it to the real bump.
We will not try here to explain in detail how type inference works. One must
just understand that there is not enough information in the above program to
deduce the correct type of g or bump. That is, there is no way to know whether
an argument is optional or not, or which is the correct order, by looking only
at how a function is applied. The strategy used by the compiler is to assume
that there are no optional arguments, and that applications are done in the
right order.
The right way to solve this problem for optional parameters is to add a type
annotation to the argument bump.
<<#let bump_it (bump : ?step:int -> int -> int) x =
# bump ~step:2 x;;
val bump_it : (?step:int -> int -> int) -> int -> int = <fun>
#bump_it bump 1;;
- : int = 3
>>
In practive, such problems appear mostly when using objects whose methods
have optional arguments, so that writing the type of object arguments is often
a good idea.
Normally the compiler generates a type error if you attempt to pass to a
function a parameter whose type is different from the expected one. However, in
the specific case where the expected type is a non-labeled function type, and
the argument is a function expecting optional parameters, the compiler will
attempt to transform the argument to have it match the expected type, by
passing None for all optional parameters.
<<#let twice f (x : int) = f(f x);;
val twice : (int -> int) -> int -> int = <fun>
#twice bump 2;;
- : int = 8
>>
This transformation is coherent with the intended semantics, including
side-effects. That is, if the application of optional parameters shall produce
side-effects, these are delayed until the received function is really applied
to an argument.
4.1.3 Suggestions for labeling
===============================
Like for names, choosing labels for functions is not an easy task. A good
labeling is a labeling which
- makes programs more readable,
- is easy to remember,
- when possible, allows useful partial applications.
We explain here the rules we applied when labeling Objective Caml libraries.
To speak in an "object-oriented" way, one can consider that each function has
a main argument, its object, and other arguments related with its action, the
parameters. To permit the combination of functions through functionals in
commuting label mode, the object will not be labeled. Its role is clear by the
function itself. The parameters are labeled with names reminding either of
their nature or role. Best labels combine in their meaning nature and role.
When this is not possible the role is to prefer, since the nature will often be
given by the type itself. Obscure abbreviations should be avoided.
<<ListLabels.map : f:('a -> 'b) -> 'a list -> 'b list
UnixLabels.write : file_descr -> buf:string -> pos:int -> len:int -> unit
>>
When there are several objects of same nature and role, they are all left
unlabeled.
<<ListLabels.iter2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> unit
>>
When there is no preferable object, all arguments are labeled.
<<StringLabels.blit :
src:string -> src_pos:int -> dst:string -> dst_pos:int -> len:int -> unit
>>
However, when there is only one argument, it is often left unlabeled.
<<StringLabels.create : int -> string
>>
This principle also applies to functions of several arguments whose return
type is a type variable, as long as the role of each argument is not ambiguous.
Labeling such functions may lead to awkward error messages when one attempts to
omit labels in an application, as we have seen with ListLabels.fold_left.
Here are some of the label names you will find throughout the libraries.
------------------------------------------------------
|Label| Meaning |
------------------------------------------------------
| f: |a function to be applied |
|pos: |a position in a string or array |
|len: |a length |
|buf: |a string used as buffer |
|src: |the source of an operation |
|dst: |the destination of an operation |
|init:|the initial value for an iterator |
|cmp: |a comparison function, e.g. Pervasives.compare|
|mode:|an operation mode or a flag list |
------------------------------------------------------
All these are only suggestions, but one shall keep in mind that the choice of
labels is essential for readability. Bizarre choices will make the program
harder to maintain.
In the ideal, the right function name with right labels shall be enough to
understand the function's meaning. Since one can get this information with
OCamlBrowser or the ocaml toplevel, the documentation is only used when a more
detailed specification is needed.
4.2 Polymorphic variants
*=*=*=*=*=*=*=*=*=*=*=*=*
Variants as presented in section 1.4 are a powerful tool to build data
structures and algorithms. However they sometimes lack flexibility when used in
modular programming. This is due to the fact every constructor reserves a name
to be used with a unique type. One cannot use the same name in another type, or
consider a value of some type to belong to some other type with more
constructors.
With polymorphic variants, this original assumption is removed. That is, a
variant tag does not belong to any type in particular, the type system will
just check that it is an admissible value according to its use. You need not
define a type before using a variant tag. A variant type will be inferred
independently for each of its uses.
Basic use
=========
In programs, polymorphic variants work like usual ones. You just have to
prefix their names with a backquote character `.
<<#[`On; `Off];;
- : [> `Off | `On ] list = [`On; `Off]
#`Number 1;;
- : [> `Number of int ] = `Number 1
#let f = function `On -> 1 | `Off -> 0 | `Number n -> n;;
val f : [< `Number of int | `Off | `On ] -> int = <fun>
#List.map f [`On; `Off];;
- : int list = [1; 0]
>>
[>`Off|`On] list means that to match this list, you should at least be able
to match `Off and `On, without argument. [<`On|`Off|`Number of int] means that
f may be applied to `Off, `On (both without argument), or `Number n where n is
an integer. The > and < inside the variant type shows that they may still be
refined, either by defining more tags or allowing less. As such they contain an
implicit type variable. Both variant types appearing only once in the type, the
implicit type variables they constrain are not shown.
The above variant types were polymorphic, allowing further refinement. When
writing type annotations, one will most often describe fixed variant types,
that is types that can be no longer refined. This is also the case for type
abbreviations. Such types do not contain < or >, but just an enumeration of the
tags and their associated types, just like in a normal datatype definition.
<<#type 'a vlist = [`Nil | `Cons of 'a * 'a vlist];;
type 'a vlist = [ `Cons of 'a * 'a vlist | `Nil ]
#let rec map f : 'a vlist -> 'b vlist = function
# | `Nil -> `Nil
# | `Cons(a, l) -> `Cons(f a, map f l)
#;;
val map : ('a -> 'b) -> 'a vlist -> 'b vlist = <fun>
>>
Advanced use
============
Type-checking polymorphic variants is a subtle thing, and some expressions
may result in more complex type information.
<<#let f = function `A -> `C | `B -> `D | x -> x;;
val f : ([> `A | `B | `C | `D ] as 'a) -> 'a = <fun>
#f `E;;
- : [> `A | `B | `C | `D | `E ] = `E
>>
Here we are seeing two phenomena. First, since this matching is open (the
last case catches any tag), we obtain the type [> `A | `B] rather than [< `A |
`B] in a closed matching. Then, since x is returned as is, input and return
types are identical. The notation as 'a denotes such type sharing. If we apply
f to yet another tag `E, it gets added to the list.
<<#let f1 = function `A x -> x = 1 | `B -> true | `C -> false
#let f2 = function `A x -> x = "a" | `B -> true ;;
val f1 : [< `A of int | `B | `C ] -> bool = <fun>
val f2 : [< `A of string | `B ] -> bool = <fun>
#let f x = f1 x && f2 x;;
val f : [< `A of string & int | `B ] -> bool = <fun>
>>
Here f1 and f2 both accept the variant tags `A and `B, but the argument of
`A is int for f1 and string for f2. In f's type `C, only accepted by f1,
disappears, but both argument types appear for `A as int & string. This means
that if we pass the variant tag `A to f, its argument should be both int and
string. Since there is no such value, f cannot be applied to `A, and `B is the
only accepted input.
Even if a value has a fixed variant type, one can still give it a larger type
through coercions. Coercions are normally written with both the source type and
the destination type, but in simple cases the source type may be omitted.
<<#type 'a wlist = [`Nil | `Cons of 'a * 'a wlist | `Snoc of 'a wlist * 'a];;
type 'a wlist = [ `Cons of 'a * 'a wlist | `Nil | `Snoc of 'a wlist * 'a ]
#let wlist_of_vlist l = (l : 'a vlist :> 'a wlist);;
val wlist_of_vlist : 'a vlist -> 'a wlist = <fun>
#let open_vlist l = (l : 'a vlist :> [> 'a vlist]);;
val open_vlist : 'a vlist -> [> 'a vlist ] = <fun>
#fun x -> (x :> [`A|`B|`C]);;
- : [< `A | `B | `C ] -> [ `A | `B | `C ] = <fun>
>>
You may also selectively coerce values through pattern matching.
<<#let split_cases = function
# | `Nil | `Cons _ as x -> `A x
# | `Snoc _ as x -> `B x
#;;
val split_cases :
[< `Cons of 'a | `Nil | `Snoc of 'b ] ->
[> `A of [> `Cons of 'a | `Nil ] | `B of [> `Snoc of 'b ] ] = <fun>
>>
When an or-pattern composed of variant tags is wrapped inside an
alias-pattern, the alias is given a type containing only the tags enumerated in
the or-pattern. This allows for many useful idioms, like incremental definition
of functions.
<<#let num x = `Num x
#let eval1 eval (`Num x) = x
#let rec eval x = eval1 eval x ;;
val num : 'a -> [> `Num of 'a ] = <fun>
val eval1 : 'a -> [< `Num of 'b ] -> 'b = <fun>
val eval : [< `Num of 'a ] -> 'a = <fun>
#let plus x y = `Plus(x,y)
#let eval2 eval = function
# | `Plus(x,y) -> eval x + eval y
# | `Num _ as x -> eval1 eval x
#let rec eval x = eval2 eval x ;;
val plus : 'a -> 'b -> [> `Plus of 'a * 'b ] = <fun>
val eval2 : ('a -> int) -> [< `Num of int | `Plus of 'a * 'a ] -> int = <fun>
val eval : ([< `Num of int | `Plus of 'a * 'a ] as 'a) -> int = <fun>
>>
To make this even more confortable, you may use type definitions as
abbreviations for or-patterns. That is, if you have defined type myvariant =
[`Tag1 int | `Tag2 bool], then the pattern #myvariant is equivalent to writing
(`Tag1(_ : int) | `Tag2(_ : bool)).
Such abbreviations may be used alone,
<<#let f = function
# | #myvariant -> "myvariant"
# | `Tag3 -> "Tag3";;
val f : [< `Tag1 of int | `Tag2 of bool | `Tag3 ] -> string = <fun>
>>
or combined with with aliases.
<<#let g1 = function `Tag1 _ -> "Tag1" | `Tag2 _ -> "Tag2";;
val g1 : [< `Tag1 of 'a | `Tag2 of 'b ] -> string = <fun>
#let g = function
# | #myvariant as x -> g1 x
# | `Tag3 -> "Tag3";;
val g : [< `Tag1 of int | `Tag2 of bool | `Tag3 ] -> string = <fun>
>>
4.2.1 Weaknesses of polymorphic variants
=========================================
After seeing the power of polymorphic variants, one may wonder why they were
added to core language variants, rather than replacing them.
The answer is two fold. One first aspect is that while being pretty
efficient, the lack of static type information allows for less optimizations,
and makes polymorphic variants slightly heavier than core language ones.
However noticeable differences would only appear on huge data structures.
More important is the fact that polymorphic variants, while being type-safe,
result in a weaker type discipline. That is, core language variants do actually
much more than ensuring type-safety, they also check that you use only declared
constructors, that all constructors present in a data-structure are compatible,
and they enforce typing constraints to their parameters.
For this reason, you must be more careful about making types explicit when
you use polymorphic variants. When you write a library, this is easy since you
can describe exact types in interfaces, but for simple programs you are
probably better off with core language variants.
Beware also that some idioms make trivial errors very hard to find. For
instance, the following code is probably wrong but the compiler has no way to
see it.
<<#type abc = [`A | `B | `C] ;;
type abc = [ `A | `B | `C ]
#let f = function
# | `As -> "A"
# | #abc -> "other" ;;
val f : [< `A | `As | `B | `C ] -> string = <fun>
#let f : abc -> string = f ;;
val f : abc -> string = <fun>
>>
You can avoid such risks by annotating the definition itself.
<<#let f : abc -> string = function
# | `As -> "A"
# | #abc -> "other" ;;
Warning U: this match case is unused.
val f : abc -> string = <fun>
>>
---------------------------------------
(1) This correspond to the commuting label mode of Objective Caml 3.00 through
3.02, with some additional flexibility on total applications. The so-called
classic mode (-nolabels options) is now deprecated for normal use.
Chapter 5 Advanced examples with classes and modules
*******************************************************
(Chapter written by Didier Rémy)
In this chapter, we show some larger examples using objects, classes and
modules. We review many of the object features simultaneously on the example of
a bank account. We show how modules taken from the standard library can be
expressed as classes. Lastly, we describe a programming pattern know of as
virtual types through the example of window managers.
5.1 Extended example: bank accounts
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
In this section, we illustrate most aspects of Object and inheritance by
refining, debugging, and specializing the following initial naive definition
of a simple bank account. (We reuse the module Euro defined at the end of
chapter 3.)
<<#let euro = new Euro.c;;
val euro : float -> Euro.c = <fun>
#let zero = euro 0.;;
val zero : Euro.c = <obj>
#let neg x = x#times (-1.);;
val neg : < times : float -> 'a; .. > -> 'a = <fun>
#class account =
# object
# val mutable balance = zero
# method balance = balance
# method deposit x = balance <- balance # plus x
# method withdraw x =
# if x#leq balance then (balance <- balance # plus (neg x); x) else zero
# end;;
class account :
object
val mutable balance : Euro.c
method balance : Euro.c
method deposit : Euro.c -> unit
method withdraw : Euro.c -> Euro.c
end
#let c = new account in c # deposit (euro 100.); c # withdraw (euro 50.);;
- : Euro.c = <obj>
>>
We now refine this definition with a method to compute interest.
<<#class account_with_interests =
# object (self)
# inherit account
# method private interest = self # deposit (self # balance # times 0.03)
# end;;
class account_with_interests :
object
val mutable balance : Euro.c
method balance : Euro.c
method deposit : Euro.c -> unit
method private interest : unit
method withdraw : Euro.c -> Euro.c
end
>>
We make the method interest private, since clearly it should not be called
freely from the outside. Here, it is only made accessible to subclasses that
will manage monthly or yearly updates of the account.
We should soon fix a bug in the current definition: the deposit method can be
used for withdrawing money by depositing negative amounts. We can fix this
directly:
<<#class safe_account =
# object
# inherit account
# method deposit x = if zero#leq x then balance <- balance#plus x
# end;;
class safe_account :
object
val mutable balance : Euro.c
method balance : Euro.c
method deposit : Euro.c -> unit
method withdraw : Euro.c -> Euro.c
end
>>
However, the bug might be fixed more safely by the following definition:
<<#class safe_account =
# object
# inherit account as unsafe
# method deposit x =
# if zero#leq x then unsafe # deposit x
# else raise (Invalid_argument "deposit")
# end;;
class safe_account :
object
val mutable balance : Euro.c
method balance : Euro.c
method deposit : Euro.c -> unit
method withdraw : Euro.c -> Euro.c
end
>>
In particular, this does not require the knowledge of the implementation of
the method deposit.
To keep trace of operations, we extend the class with a mutable field history
and a private method trace to add an operation in the log. Then each method to
be traced is redefined.
<<#type 'a operation = Deposit of 'a | Retrieval of 'a;;
type 'a operation = Deposit of 'a | Retrieval of 'a
#class account_with_history =
# object (self)
# inherit safe_account as super
# val mutable history = []
# method private trace x = history <- x :: history
# method deposit x = self#trace (Deposit x); super#deposit x
# method withdraw x = self#trace (Retrieval x); super#withdraw x
# method history = List.rev history
# end;;
class account_with_history :
object
val mutable balance : Euro.c
val mutable history : Euro.c operation list
method balance : Euro.c
method deposit : Euro.c -> unit
method history : Euro.c operation list
method private trace : Euro.c operation -> unit
method withdraw : Euro.c -> Euro.c
end
>>
One may wish to open an account and simultaneously deposit some initial
amount. Although the initial implementation did not address this requirement,
it can be achieved by using an initializer.
<<#class account_with_deposit x =
# object
# inherit account_with_history
# initializer balance <- x
# end;;
class account_with_deposit :
Euro.c ->
object
val mutable balance : Euro.c
val mutable history : Euro.c operation list
method balance : Euro.c
method deposit : Euro.c -> unit
method history : Euro.c operation list
method private trace : Euro.c operation -> unit
method withdraw : Euro.c -> Euro.c
end
>>
A better alternative is:
<<#class account_with_deposit x =
# object (self)
# inherit account_with_history
# initializer self#deposit x
# end;;
class account_with_deposit :
Euro.c ->
object
val mutable balance : Euro.c
val mutable history : Euro.c operation list
method balance : Euro.c
method deposit : Euro.c -> unit
method history : Euro.c operation list
method private trace : Euro.c operation -> unit
method withdraw : Euro.c -> Euro.c
end
>>
Indeed, the latter is safer since the call to deposit will automatically
benefit from safety checks and from the trace. Let's test it:
<<#let ccp = new account_with_deposit (euro 100.) in
#let balance = ccp#withdraw (euro 50.) in
#ccp#history;;
Warning Y: unused variable balance.
- : Euro.c operation list = [Deposit <obj>; Retrieval <obj>]
>>
Closing an account can be done with the following polymorphic function:
<<#let close c = c#withdraw (c#balance);;
val close : < balance : 'a; withdraw : 'a -> 'b; .. > -> 'b = <fun>
>>
Of course, this applies to all sorts of accounts.
Finally, we gather several versions of the account into a module Account
abstracted over some currency.
<<#let today () = (01,01,2000) (* an approximation *)
#module Account (M:MONEY) =
# struct
# type m = M.c
# let m = new M.c
# let zero = m 0.
#
# class bank =
# object (self)
# val mutable balance = zero
# method balance = balance
# val mutable history = []
# method private trace x = history <- x::history
# method deposit x =
# self#trace (Deposit x);
# if zero#leq x then balance <- balance # plus x
# else raise (Invalid_argument "deposit")
# method withdraw x =
# if x#leq balance then
# (balance <- balance # plus (neg x); self#trace (Retrieval x); x)
# else zero
# method history = List.rev history
# end
#
# class type client_view =
# object
# method deposit : m -> unit
# method history : m operation list
# method withdraw : m -> m
# method balance : m
# end
#
# class virtual check_client x =
# let y = if (m 100.)#leq x then x
# else raise (Failure "Insufficient initial deposit") in
# object (self) initializer self#deposit y end
#
# module Client (B : sig class bank : client_view end) =
# struct
# class account x : client_view =
# object
# inherit B.bank
# inherit check_client x
# end
#
# let discount x =
# let c = new account x in
# if today() < (1998,10,30) then c # deposit (m 100.); c
# end
# end;;
>>
This shows the use of modules to group several class definitions that can in
fact be thought of as a single unit. This unit would be provided by a bank for
both internal and external uses. This is implemented as a functor that
abstracts over the currency so that the same code can be used to provide
accounts in different currencies.
The class bank is the real implementation of the bank account (it could have
been inlined). This is the one that will be used for further extensions,
refinements, etc. Conversely, the client will only be given the client view.
<<#module Euro_account = Account(Euro);;
#module Client = Euro_account.Client (Euro_account);;
#new Client.account (new Euro.c 100.);;
>>
Hence, the clients do not have direct access to the balance, nor the history
of their own accounts. Their only way to change their balance is to deposit or
withdraw money. It is important to give the clients a class and not just the
ability to create accounts (such as the promotional discount account), so that
they can personalize their account. For instance, a client may refine the
deposit and withdraw methods so as to do his own financial bookkeeping,
automatically. On the other hand, the function discount is given as such, with
no possibility for further personalization.
It is important that to provide the client's view as a functor Client so that
client accounts can still be build after a possible specialization of the bank.
The functor Client may remain unchanged and be passed the new definition to
initialize a client's view of the extended account.
<<#module Investment_account (M : MONEY) =
# struct
# type m = M.c
# module A = Account(M)
#
# class bank =
# object
# inherit A.bank as super
# method deposit x =
# if (new M.c 1000.)#leq x then
# print_string "Would you like to invest?";
# super#deposit x
# end
#
# module Client = A.Client
# end;;
>>
The functor Client may also be redefined when some new features of the
account can be given to the client.
<<#module Internet_account (M : MONEY) =
# struct
# type m = M.c
# module A = Account(M)
# class bank =
# object
# inherit A.bank
# method mail s = print_string s
# end
#
# class type client_view =
# object
# method deposit : m -> unit
# method history : m operation list
# method withdraw : m -> m
# method balance : m
# method mail : string -> unit
# end
#
# module Client (B : sig class bank : client_view end) =
# struct
# class account x : client_view =
# object
# inherit B.bank
# inherit A.check_client x
# end
# end
# end;;
>>
5.2 Simple modules as classes
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
One may wonder whether it is possible to treat primitive types such as
integers and strings as objects. Although this is usually uninteresting for
integers or strings, there may be some situations where this is desirable. The
class money above is such an example. We show here how to do it for strings.
5.2.1 Strings
==============
A naive definition of strings as objects could be:
<<#class ostring s =
# object
# method get n = String.get s n
# method set n c = String.set s n c
# method print = print_string s
# method copy = new ostring (String.copy s)
# end;;
class ostring :
string ->
object
method copy : ostring
method get : int -> char
method print : unit
method set : int -> char -> unit
end
>>
However, the method copy returns an object of the class ostring, and not an
objet of the current class. Hence, if the class is further extended, the method
copy will only return an object of the parent class.
<<#class sub_string s =
# object
# inherit ostring s
# method sub start len = new sub_string (String.sub s start len)
# end;;
class sub_string :
string ->
object
method copy : ostring
method get : int -> char
method print : unit
method set : int -> char -> unit
method sub : int -> int -> sub_string
end
>>
As seen in section 3.16, the solution is to use functional update instead.
We need to create an instance variable containing the representation s of the
string.
<<#class better_string s =
# object
# val repr = s
# method get n = String.get repr n
# method set n c = String.set repr n c
# method print = print_string repr
# method copy = {< repr = String.copy repr >}
# method sub start len = {< repr = String.sub s start len >}
# end;;
class better_string :
string ->
object ('a)
val repr : string
method copy : 'a
method get : int -> char
method print : unit
method set : int -> char -> unit
method sub : int -> int -> 'a
end
>>
As shown in the inferred type, the methods copy and sub now return objects
of the same type as the one of the class.
Another difficulty is the implementation of the method concat. In order to
concatenate a string with another string of the same class, one must be able
to access the instance variable externally. Thus, a method repr returning s
must be defined. Here is the correct definition of strings:
<<#class ostring s =
# object (self : 'mytype)
# val repr = s
# method repr = repr
# method get n = String.get repr n
# method set n c = String.set repr n c
# method print = print_string repr
# method copy = {< repr = String.copy repr >}
# method sub start len = {< repr = String.sub s start len >}
# method concat (t : 'mytype) = {< repr = repr ^ t#repr >}
# end;;
class ostring :
string ->
object ('a)
val repr : string
method concat : 'a -> 'a
method copy : 'a
method get : int -> char
method print : unit
method repr : string
method set : int -> char -> unit
method sub : int -> int -> 'a
end
>>
Another constructor of the class string can be defined to return an
uninitialized string of a given length:
<<#class cstring n = ostring (String.create n);;
class cstring : int -> ostring
>>
Here, exposing the representation of strings is probably harmless. We do
could also hide the representation of strings as we hid the currency in the
class money of section 3.17.
Stacks
------
There is sometimes an alternative between using modules or classes for
parametric data types. Indeed, there are situations when the two approaches
are quite similar. For instance, a stack can be straightforwardly implemented
as a class:
<<#exception Empty;;
exception Empty
#class ['a] stack =
# object
# val mutable l = ([] : 'a list)
# method push x = l <- x::l
# method pop = match l with [] -> raise Empty | a::l' -> l <- l'; a
# method clear = l <- []
# method length = List.length l
# end;;
class ['a] stack :
object
val mutable l : 'a list
method clear : unit
method length : int
method pop : 'a
method push : 'a -> unit
end
>>
However, writing a method for iterating over a stack is more problematic. A
method fold would have type ('b -> 'a -> 'b) -> 'b -> 'b. Here 'a is the
parameter of the stack. The parameter 'b is not related to the class 'a stack
but to the argument that will be passed to the method fold. A naive approach is
to make 'b an extra parameter of class stack:
<<#class ['a, 'b] stack2 =
# object
# inherit ['a] stack
# method fold f (x : 'b) = List.fold_left f x l
# end;;
class ['a, 'b] stack2 :
object
val mutable l : 'a list
method clear : unit
method fold : ('b -> 'a -> 'b) -> 'b -> 'b
method length : int
method pop : 'a
method push : 'a -> unit
end
>>
However, the method fold of a given object can only be applied to functions
that all have the same type:
<<#let s = new stack2;;
val s : ('_a, '_b) stack2 = <obj>
#s#fold (+) 0;;
- : int = 0
#s;;
- : (int, int) stack2 = <obj>
>>
A better solution is to use polymorphic methods, which were introduced in
Objective Caml version 3.05. Polymorphic methods makes it possible to treat the
type variable 'b in the type of fold as universally quantified, giving fold the
polymorphic type Forall 'b. ('b -> 'a -> 'b) -> 'b -> 'b. An explicit type
declaration on the method fold is required, since the type checker cannot infer
the polymorphic type by itself.
<<#class ['a] stack3 =
# object
# inherit ['a] stack
# method fold : 'b. ('b -> 'a -> 'b) -> 'b -> 'b
# = fun f x -> List.fold_left f x l
# end;;
class ['a] stack3 :
object
val mutable l : 'a list
method clear : unit
method fold : ('b -> 'a -> 'b) -> 'b -> 'b
method length : int
method pop : 'a
method push : 'a -> unit
end
>>
5.2.2 Hashtbl
==============
A simplified version of object-oriented hash tables should have the following
class type.
<<#class type ['a, 'b] hash_table =
# object
# method find : 'a -> 'b
# method add : 'a -> 'b -> unit
# end;;
class type ['a, 'b] hash_table =
object method add : 'a -> 'b -> unit method find : 'a -> 'b end
>>
A simple implementation, which is quite reasonable for small hastables is to
use an association list:
<<#class ['a, 'b] small_hashtbl : ['a, 'b] hash_table =
# object
# val mutable table = []
# method find key = List.assoc key table
# method add key valeur = table <- (key, valeur) :: table
# end;;
class ['a, 'b] small_hashtbl : ['a, 'b] hash_table
>>
A better implementation, and one that scales up better, is to use a true
hash tables... whose elements are small hash tables!
<<#class ['a, 'b] hashtbl size : ['a, 'b] hash_table =
# object (self)
# val table = Array.init size (fun i -> new small_hashtbl)
# method private hash key =
# (Hashtbl.hash key) mod (Array.length table)
# method find key = table.(self#hash key) # find key
# method add key = table.(self#hash key) # add key
# end;;
class ['a, 'b] hashtbl : int -> ['a, 'b] hash_table
>>
5.2.3 Sets
===========
Implementing sets leads to another difficulty. Indeed, the method union needs
to be able to access the internal representation of another object of the same
class.
This is another instance of friend functions as seen in section 3.17. Indeed,
this is the same mechanism used in the module Set in the absence of objects.
In the object-oriented version of sets, we only need to add an additional
method tag to return the representation of a set. Since sets are parametric in
the type of elements, the method tag has a parametric type 'a tag, concrete
within the module definition but abstract in its signature. From outside, it
will then be guaranteed that two objects with a method tag of the same type
will share the same representation.
<<#module type SET =
# sig
# type 'a tag
# class ['a] c :
# object ('b)
# method is_empty : bool
# method mem : 'a -> bool
# method add : 'a -> 'b
# method union : 'b -> 'b
# method iter : ('a -> unit) -> unit
# method tag : 'a tag
# end
# end;;
#module Set : SET =
# struct
# let rec merge l1 l2 =
# match l1 with
# [] -> l2
# | h1 :: t1 ->
# match l2 with
# [] -> l1
# | h2 :: t2 ->
# if h1 < h2 then h1 :: merge t1 l2
# else if h1 > h2 then h2 :: merge l1 t2
# else merge t1 l2
# type 'a tag = 'a list
# class ['a] c =
# object (_ : 'b)
# val repr = ([] : 'a list)
# method is_empty = (repr = [])
# method mem x = List.exists ((=) x) repr
# method add x = {< repr = merge [x] repr >}
# method union (s : 'b) = {< repr = merge repr s#tag >}
# method iter (f : 'a -> unit) = List.iter f repr
# method tag = repr
# end
# end;;
>>
5.3 The subject/observer pattern
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The following example, known as the subject/observer pattern, is often
presented in the literature as a difficult inheritance problem with
inter-connected classes. The general pattern amounts to the definition a pair
of two classes that recursively interact with one another.
The class observer has a distinguished method notify that requires two
arguments, a subject and an event to execute an action.
<<#class virtual ['subject, 'event] observer =
# object
# method virtual notify : 'subject -> 'event -> unit
# end;;
class virtual ['a, 'b] observer :
object method virtual notify : 'a -> 'b -> unit end
>>
The class subject remembers a list of observers in an instance variable, and
has a distinguished method notify_observers to broadcast the message notify to
all observers with a particular event e.
<<#class ['observer, 'event] subject =
# object (self)
# val mutable observers = ([]:'observer list)
# method add_observer obs = observers <- (obs :: observers)
# method notify_observers (e : 'event) =
# List.iter (fun x -> x#notify self e) observers
# end;;
class ['a, 'b] subject :
object ('c)
constraint 'a = < notify : 'c -> 'b -> unit; .. >
val mutable observers : 'a list
method add_observer : 'a -> unit
method notify_observers : 'b -> unit
end
>>
The difficulty usually relies in defining instances of the pattern above by
inheritance. This can be done in a natural and obvious manner in Ocaml, as
shown on the following example manipulating windows.
<<#type event = Raise | Resize | Move;;
type event = Raise | Resize | Move
#let string_of_event = function
# Raise -> "Raise" | Resize -> "Resize" | Move -> "Move";;
val string_of_event : event -> string = <fun>
#let count = ref 0;;
val count : int ref = {contents = 0}
#class ['observer] window_subject =
# let id = count := succ !count; !count in
# object (self)
# inherit ['observer, event] subject
# val mutable position = 0
# method identity = id
# method move x = position <- position + x; self#notify_observers Move
# method draw = Printf.printf "{Position = %d}\n" position;
# end;;
class ['a] window_subject :
object ('b)
constraint 'a = < notify : 'b -> event -> unit; .. >
val mutable observers : 'a list
val mutable position : int
method add_observer : 'a -> unit
method draw : unit
method identity : int
method move : int -> unit
method notify_observers : event -> unit
end
#class ['subject] window_observer =
# object
# inherit ['subject, event] observer
# method notify s e = s#draw
# end;;
class ['a] window_observer :
object
constraint 'a = < draw : unit; .. >
method notify : 'a -> event -> unit
end
>>
Unsurprisingly the type of window is recursive.
<<#let window = new window_subject;;
val window : < notify : 'a -> event -> unit; _.. > window_subject as 'a =
<obj>
>>
However, the two classes of window_subject and window_observer are not
mutually recursive.
<<#let window_observer = new window_observer;;
val window_observer : < draw : unit; _.. > window_observer = <obj>
#window#add_observer window_observer;;
- : unit = ()
#window#move 1;;
{Position = 1}
- : unit = ()
>>
Classes window_observer and window_subject can still be extended by
inheritance. For instance, one may enrich the subject with new behaviors and
refined the behavior of the observer.
<<#class ['observer] richer_window_subject =
# object (self)
# inherit ['observer] window_subject
# val mutable size = 1
# method resize x = size <- size + x; self#notify_observers Resize
# val mutable top = false
# method raise = top <- true; self#notify_observers Raise
# method draw = Printf.printf "{Position = %d; Size = %d}\n" position
size;
# end;;
class ['a] richer_window_subject :
object ('b)
constraint 'a = < notify : 'b -> event -> unit; .. >
val mutable observers : 'a list
val mutable position : int
val mutable size : int
val mutable top : bool
method add_observer : 'a -> unit
method draw : unit
method identity : int
method move : int -> unit
method notify_observers : event -> unit
method raise : unit
method resize : int -> unit
end
#class ['subject] richer_window_observer =
# object
# inherit ['subject] window_observer as super
# method notify s e = if e <> Raise then s#raise; super#notify s e
# end;;
class ['a] richer_window_observer :
object
constraint 'a = < draw : unit; raise : unit; .. >
method notify : 'a -> event -> unit
end
>>
We can also create a different kind of observer:
<<#class ['subject] trace_observer =
# object
# inherit ['subject, event] observer
# method notify s e =
# Printf.printf
# "<Window %d <== %s>\n" s#identity (string_of_event e)
# end;;
class ['a] trace_observer :
object
constraint 'a = < identity : int; .. >
method notify : 'a -> event -> unit
end
>>
and attached several observers to the same object:
<<#let window = new richer_window_subject;;
val window :
< notify : 'a -> event -> unit; _.. > richer_window_subject as 'a = <obj>
#window#add_observer (new richer_window_observer);;
- : unit = ()
#window#add_observer (new trace_observer);;
- : unit = ()
#window#move 1; window#resize 2;;
<Window 1 <== Move>
<Window 1 <== Raise>
{Position = 1; Size = 1}
{Position = 1; Size = 1}
<Window 1 <== Resize>
<Window 1 <== Raise>
{Position = 1; Size = 3}
{Position = 1; Size = 3}
- : unit = ()
>>
Part: II
********
The Objective Caml language
***************************
Chapter 6 The Objective Caml language
****************************************
Foreword
*=*=*=*=
This document is intended as a reference manual for the Objective Caml
language. It lists the language constructs, and gives their precise syntax and
informal semantics. It is by no means a tutorial introduction to the language:
there is not a single example. A good working knowledge of Caml is assumed.
No attempt has been made at mathematical rigor: words are employed with their
intuitive meaning, without further definition. As a consequence, the typing
rules have been left out, by lack of the mathematical framework required to
express them, while they are definitely part of a full formal definition of the
language.
Notations
=========
The syntax of the language is given in BNF-like notation. Terminal symbols
are set in typewriter font (like this). Non-terminal symbols are set in italic
font (like that). Square brackets [...] denote optional components. Curly
brackets {...} denotes zero, one or several repetitions of the enclosed
components. Curly bracket with a trailing plus sign {...}^+ denote one or
several repetitions of the enclosed components. Parentheses (...) denote
grouping.
6.1 Lexical conventions
*=*=*=*=*=*=*=*=*=*=*=*=
Blanks
------
The following characters are considered as blanks: space, newline, horizontal
tabulation, carriage return, line feed and form feed. Blanks are ignored, but
they separate adjacent identifiers, literals and keywords that would otherwise
be confused as one single identifier, literal or keyword.
Comments
--------
Comments are introduced by the two characters (*, with no intervening blanks,
and terminated by the characters *), with no intervening blanks. Comments are
treated as blank characters. Comments do not occur inside string or character
literals. Nested comments are handled correctly.
Identifiers
-----------
ident ::= (letter| _) { letter| 0...9| _| ' }
letter ::= A ... Z | a ... z
Identifiers are sequences of letters, digits, _ (the underscore character),
and ' (the single quote), starting with a letter or an underscore. Letters
contain at least the 52 lowercase and uppercase letters from the ASCII set. The
current implementation also recognizes as letters all accented characters from
the ISO 8859-1 ("ISO Latin 1") set. All characters in an identifier are
meaningful. The current implementation accepts identifiers up to 16000000
characters in length.
Integer literals
----------------
integer-literal ::= [-] (0...9) { 0...9| _ }
| [-] (0x| 0X) (0...9| A...F| a...f) { 0...9| A...F|
a...f| _ }
| [-] (0o| 0O) (0...7) { 0...7| _ }
| [-] (0b| 0B) (0...1) { 0...1| _ }
An integer literal is a sequence of one or more digits, optionally preceded
by a minus sign. By default, integer literals are in decimal (radix 10). The
following prefixes select a different radix:
--------------------------------
|Prefix | Radix |
--------------------------------
| 0x, 0X|hexadecimal (radix 16)|
|0o, 0O |octal (radix 8) |
|0b, 0B |binary (radix 2) |
--------------------------------
(The initial 0 is the digit zero; the O for octal is the letter O.) The
interpretation of integer literals that fall outside the range of representable
integer values is undefined.
For convenience and readability, underscore characters (_) are accepted (and
ignored) within integer literals.
Floating-point literals
-----------------------
float-literal ::= [-] (0...9) { 0...9| _ } [. { 0...9| _ }] [(e| E) [+| -]
(0...9) { 0...9| _ }]
Floating-point decimals consist in an integer part, a decimal part and an
exponent part. The integer part is a sequence of one or more digits, optionally
preceded by a minus sign. The decimal part is a decimal point followed by zero,
one or more digits. The exponent part is the character e or E followed by an
optional + or - sign, followed by one or more digits. The decimal part or the
exponent part can be omitted, but not both to avoid ambiguity with integer
literals. The interpretation of floating-point literals that fall outside the
range of representable floating-point values is undefined.
For convenience and readability, underscore characters (_) are accepted (and
ignored) within floating-point literals.
Character literals
------------------
char-literal ::= ' regular-char '
| ' escape-sequence '
escape-sequence ::= \ (\ | " | ' | n | t | b | r)
| \ (0...9) (0...9) (0...9)
| \x (0...9| A...F| a...f) (0...9| A...F| a...f)
Character literals are delimited by ' (single quote) characters. The two
single quotes enclose either one character different from ' and \, or one of
the escape sequences below:
----------------------------------------------------------
|Sequence| Character denoted |
----------------------------------------------------------
| \\ |backslash (\) |
|\" |double quote (") |
|\' |single quote (') |
|\n |linefeed (LF) |
|\r |carriage return (CR) |
|\t |horizontal tabulation (TAB) |
|\b |backspace (BS) |
|\space |space (SPC) |
|\ddd |the character with ASCII code ddd in decimal |
|\xhh |the character with ASCII code hh in hexadecimal|
----------------------------------------------------------
String literals
---------------
string-literal ::= " { string-character } "
string-character ::= regular-char-str
| escape-sequence
String literals are delimited by " (double quote) characters. The two double
quotes enclose a sequence of either characters different from " and \, or
escape sequences from the table given above for character literals.
To allow splitting long string literals across lines, the sequence \newline
blanks (a \ at end-of-line followed by any number of blanks at the beginning of
the next line) is ignored inside string literals.
The current implementation places practically no restrictions on the length
of string literals.
Naming labels
-------------
To avoid ambiguities, naming labels cannot just be defined syntactically as
the sequence of the three tokens ~, ident and :, and have to be defined at the
lexical level.
label ::= ~ (a ... z| _) { letter| 0...9| _| ' } :
optlabel ::= ? (a ... z| _) { letter| 0...9| _| ' } :
Naming labels come in two flavours: label for normal arguments and optlabel
for optional ones. They are simply distinguished by their first character,
either ~ or ?.
Prefix and infix symbols
------------------------
infix-symbol ::= (= | < | > | @ | ^ | | | & | + | - | * | / | $
| %) { operator-char }
prefix-symbol ::= (! | ? | ~) { operator-char }
operator-char ::= ! | $ | % | & | * | + | - | . | / | : | < | = |
> | ? | @ | ^ | | | ~
Sequences of "operator characters", such as <=> or !!, are read as a single
token from the infix-symbol or prefix-symbol class. These symbols are parsed as
prefix and infix operators inside expressions, but otherwise behave much as
identifiers.
Keywords
--------
The identifiers below are reserved as keywords, and cannot be employed
otherwise:
<< and as assert asr begin class
constraint do done downto else end
exception external false for fun function
functor if in include inherit initializer
land lazy let lor lsl lsr
lxor match method mod module mutable
new object of open or private
rec sig struct then to true
try type val virtual when while
with
>>
The following character sequences are also keywords:
<< != # & && ' ( ) * + , -
-. -> . .. : :: := :> ; ;; <
<- = > >] >} ? ?? [ [< [> [|
] _ ` { {< | |] } ~
>>
Note that the following identifiers are keywords of the Camlp4 extensions and
should be avoided for compatibility reasons.
<< parser << <: >> $ $$ $:
>>
Ambiguities
-----------
Lexical ambiguities are resolved according to the "longest match" rule: when
a character sequence can be decomposed into two tokens in several different
ways, the decomposition retained is the one with the longest first token.
Line number directives
----------------------
+
linenum-directive ::= # {0 ... 9}
+
| # {0 ... 9} " { string-character } "
Preprocessors that generate Caml source code can insert line number
directives in their output so that error messages produced by the compiler
contain line numbers and file names referring to the source file before
preprocessing, instead of after preprocessing. A line number directive is
composed of a # (sharp sign), followed by a positive integer (the source line
number), optionally followed by a character string (the source file name). Line
number directives are treated as blank characters during lexical analysis.
6.2 Values
*=*=*=*=*=*
This section describes the kinds of values that are manipulated by Objective
Caml programs.
6.2.1 Base values
==================
Integer numbers
---------------
Integer values are integer numbers from -2^30 to 2^30-1, that is -1073741824
to 1073741823. The implementation may support a wider range of integer values:
on 64-bit platforms, the current implementation supports integers ranging from
-2^62 to 2^62-1.
Floating-point numbers
----------------------
Floating-point values are numbers in floating-point representation. The
current implementation uses double-precision floating-point numbers conforming
to the IEEE 754 standard, with 53 bits of mantissa and an exponent ranging from
-1022 to 1023.
Characters
----------
Character values are represented as 8-bit integers between 0 and 255.
Character codes between 0 and 127 are interpreted following the ASCII standard.
The current implementation interprets character codes between 128 and 255
following the ISO 8859-1 standard.
Character strings
-----------------
String values are finite sequences of characters. The current implementation
supports strings containing up to 2^24 - 5 characters (16777211 characters); on
64-bit platforms, the limit is 2^57 - 9.
6.2.2 Tuples
=============
Tuples of values are written (v_1, ..., v_n), standing for the n-tuple of
values v_1 to v_n. The current implementation supports tuple of up to 2^22 - 1
elements (4194303 elements).
6.2.3 Records
==============
Record values are labeled tuples of values. The record value written {
field_1 = v_1; ...; field_n = v_n } associates the value v_i to the record
field field_i, for i = 1 ... n. The current implementation supports records
with up to 2^22 - 1 fields (4194303 fields).
6.2.4 Arrays
=============
Arrays are finite, variable-sized sequences of values of the same type. The
current implementation supports arrays containing up to 2^22 - 1 elements
(4194303 elements) unless the elements are floating-point numbers (2097151
elements in this case); on 64-bit platforms, the limit is 2^54 - 1 for all
arrays.
6.2.5 Variant values
=====================
Variant values are either a constant constructor, or a pair of a non-constant
constructor and a value. The former case is written constr; the latter case is
written constr(v), where v is said to be the argument of the non-constant
constructor constr.
The following constants are treated like built-in constant constructors:
----------------------------
|Constant| Constructor |
----------------------------
| false |the boolean false|
|true |the boolean true |
|() |the "unit" value |
|[] |the empty list |
----------------------------
The current implementation limits each variant type to have at most 246
non-constant constructors.
6.2.6 Polymorphic variants
===========================
Polymorphic variants are an alternate form of variant values, not belonging
explicitly to a predefined variant type, and following specific typing rules.
They can be either constant, written `tag-name, or non-constant, written
`tag-name(v).
6.2.7 Functions
================
Functional values are mappings from values to values.
6.2.8 Objects
==============
Objects are composed of a hidden internal state which is a record of instance
variables, and a set of methods for accessing and modifying these variables.
The structure of an object is described by the toplevel class that created it.
6.3 Names
*=*=*=*=*=
Identifiers are used to give names to several classes of language objects and
refer to these objects by name later:
- value names (syntactic class value-name),
- value constructors and exception constructors (class constr-name),
- labels (label-name),
- variant tags (tag-name),
- type constructors (typeconstr-name),
- record fields (field-name),
- class names (class-name),
- method names (method-name),
- instance variable names (inst-var-name),
- module names (module-name),
- module type names (modtype-name).
These eleven name spaces are distinguished both by the context and by the
capitalization of the identifier: whether the first letter of the identifier is
in lowercase (written lowercase-ident below) or in uppercase (written
capitalized-ident). Underscore is considered a lowercase letter for this
purpose.
Naming objects
--------------
value-name ::= lowercase-ident
| ( operator-name )
operator-name ::= prefix-symbol | infix-op
infix-op ::= infix-symbol
| * | = | or | & | :=
| mod | land | lor | lxor | lsl | lsr | asr
constr-name ::= capitalized-ident
label-name ::= lowercase-ident
tag-name ::= capitalized-ident
typeconstr-name ::= lowercase-ident
field-name ::= lowercase-ident
module-name ::= capitalized-ident
modtype-name ::= ident
class-name ::= lowercase-ident
inst-var-name ::= lowercase-ident
method-name ::= lowercase-ident
As shown above, prefix and infix symbols as well as some keywords can be
used as value names, provided they are written between parentheses. The
capitalization rules are summarized in the table below.
-----------------------------------------
| Name space |Case of first letter|
-----------------------------------------
| Values |lowercase |
|Constructors |uppercase |
|Labels |lowercase |
|Variant tags |uppercase |
|Exceptions |uppercase |
|Type constructors |lowercase |
|Record fields |lowercase |
|Classes |lowercase |
|Instance variables|lowercase |
|Methods |lowercase |
|Modules |uppercase |
|Module types |any |
-----------------------------------------
Note on variant tags: the current implementation accepts lowercase variant
tags in addition to uppercase variant tags, but we suggest you avoid lowercase
variant tags for portability and compatibility with future OCaml versions.
Referring to named objects
--------------------------
value-path ::= value-name
| module-path . value-name
constr ::= constr-name
| module-path . constr-name
typeconstr ::= typeconstr-name
| extended-module-path . typeconstr-name
field ::= field-name
| module-path . field-name
module-path ::= module-name
| module-path . module-name
extended-module-path ::= module-name
| extended-module-path . module-name
| extended-module-path ( extended-module-path )
modtype-path ::= modtype-name
| extended-module-path . modtype-name
class-path ::= class-name
| module-path . class-name
A named object can be referred to either by its name (following the usual
static scoping rules for names) or by an access path prefix . name, where
prefix designates a module and name is the name of an object defined in that
module. The first component of the path, prefix, is either a simple module name
or an access path name_1 . name_2 ..., in case the defining module is itself
nested inside other modules. For referring to type constructors or module
types, the prefix can also contain simple functor applications (as in the
syntactic class extended-module-path above), in case the defining module is the
result of a functor application.
Label names, tag names, method names and instance variable names need not be
qualified: the former three are global labels, while the latter are local to a
class.
6.4 Type expressions
*=*=*=*=*=*=*=*=*=*=*
typexpr ::= ' ident
| _
| ( typexpr )
| [[?]label-name:] typexpr -> typexpr
+
| typexpr { * typexpr }
| typeconstr
| typexpr typeconstr
| ( typexpr { , typexpr } ) typeconstr
| typexpr as ' ident
| variant-type
| < [..] >
| < method-type { ; method-type } [; ..] >
| # class-path
| typexpr # class-path
| ( typexpr { , typexpr } ) # class-path
poly-typexpr ::= typexpr
+
| { ' ident } . typexpr
method-type ::= method-name : poly-typexpr
The table below shows the relative precedences and associativity of operators
and non-closed type constructions. The constructions with higher precedences
come first.
---------------------------------------------
| Operator |Associativity|
---------------------------------------------
| Type constructor application|-- |
|* |-- |
|-> |right |
|as |-- |
---------------------------------------------
Type expressions denote types in definitions of data types as well as in type
constraints over patterns and expressions.
Type variables
--------------
The type expression ' ident stands for the type variable named ident. The
type expression _ stands for an anonymous type variable. In data type
definitions, type variables are names for the data type parameters. In type
constraints, they represent unspecified types that can be instantiated by any
type to satisfy the type constraint. In general the scope of a named type
variable is the whole enclosing definition; and they can only be generalized
when leaving this scope. Anonymous variables have no such restriction. In the
following cases, the scope of named type variables is restricted to the type
expression where they appear: 1) for universal (explicitly polymorphic) type
variables; 2) for type variables that only appear in public method
specifications (as those variables will be made universal, as described in
section 6.9.1); 3) for variables used as aliases, when the type they are
aliased to would be invalid in the scope of the enclosing definition (i.e. when
it contains free universal type variables, or locally defined types.)
Parenthesized types
-------------------
The type expression ( typexpr ) denotes the same type as typexpr.
Function types
--------------
The type expression typexpr_1 -> typexpr_2 denotes the type of functions
mapping arguments of type typexpr_1 to results of type typexpr_2.
label-name : typexpr_1 -> typexpr_2 denotes the same function type, but the
argument is labeled label.
optlabel typexpr_1 -> typexpr_2 denotes the type of functions mapping an
optional labeled argument of type typexpr_1 to results of type typexpr_2. That
is, the physical type of the function will be typexpr_1 option -> typexpr_2.
Tuple types
-----------
The type expression typexpr_1 * ... * typexpr_n denotes the type of tuples
whose elements belong to types typexpr_1, ... typexpr_n respectively.
Constructed types
-----------------
Type constructors with no parameter, as in typeconstr, are type expressions.
The type expression typexpr typeconstr, where typeconstr is a type
constructor with one parameter, denotes the application of the unary type
constructor typeconstr to the type typexpr.
The type expression (typexpr_1,..., typexpr_n) typeconstr, where typeconstr
is a type constructor with n parameters, denotes the application of the n-ary
type constructor typeconstr to the types typexpr_1 through typexpr_n.
Aliased and recursive types
---------------------------
The type expression typexpr as ' ident denotes the same type as typexpr, and
also binds the type variable ident to type typexpr both in typexpr and in other
types. In general the scope of an alias is the same as for a named type
variable, and covers the whole enclosing definition. If the type variable ident
actually occurs in typexpr, a recursive type is created. Recursive types for
which there exists a recursive path that does not contain an object or variant
type constructor are rejected, except when the -rectypes mode is selected.
If ' ident denotes an explicit polymorphic variable, and typexpr denotes
either an object or variant type, the row variable of typexpr is captured by '
ident, and quantified upon.
Variant types
-------------
variant-type ::= [ [ | ] tag-spec { | tag-spec } ]
| [> [ tag-spec ] { | tag-spec } ]
+
| [< [ | ] tag-spec-full { | tag-spec-full } [ > {
`tag-name } ] ]
tag-spec ::= `tag-name [ of typexpr ]
| typexpr
tag-spec-full ::= `tag-name [ of typexpr ] { & typexpr }
| typexpr
Variant types describe the values a polymorphic variant may take.
The first case is an exact variant type: all possible tags are known, with
their associated types, and they can all be present. Its structure is fully
known.
The second case is an open variant type, describing a polymorphic variant
value: it gives the list of all tags the value could take, with their
associated types. This type is still compatible with a variant type containing
more tags. A special case is the unknown type, which does not define any tag,
and is compatible with any variant type.
The third case is a closed variant type. It gives information about all the
possible tags and their associated types, and which tags are known to
potentially appear in values. The above exact variant type is just an
abbreviation for a closed variant type where all possible tags are also
potentially present.
In all three cases, tags may be either specified directly in the `tag-name
[...] form, or indirectly through a type expression. In this last case, the
type expression must expand to an exact variant type, whose tag specifications
are inserted in its place.
Full specification of variant tags are only used for non-exact closed types.
They can be understood as a conjunctive type for the argument: it is intended
to have all the types enumerated in the specification.
Such conjunctive constraints may be unsatisfiable. In such a case the
corresponding tag may not be used in a value of this type. This does not mean
that the whole type is not valid: one can still use other available tags.
Object types
------------
An object type < method-type { ; method-type } > is a record of method
types.
Each method may have an explicit polymorphic type: { ' ident }^+ . typexpr.
Explicit polymorphic variables have a local scope, and an explicit polymorphic
type can only be unified to an equivalent one, with polymorphic variables at
the same positions.
The type < method-type { ; method-type } ; .. > is the type of an object
with methods and their associated types are described by method-type_1, ...,
method-type_n, and possibly some other methods represented by the ellipsis.
This ellipsis actually is a special kind of type variable (also called row
variable in the literature) that stands for any number of extra method types.
#-types
-------
The type # class-path is a special kind of abbreviation. This abbreviation
unifies with the type of any object belonging to a subclass of class
class-path. It is handled in a special way as it usually hides a type variable
(an ellipsis, representing the methods that may be added in a subclass). In
particular, it vanishes when the ellipsis gets instantiated. Each type
expression # class-path defines a new type variable, so type # class-path -> #
class-path is usually not the same as type (# class-path as ' ident) -> '
ident.
Use of #-types to abbreviate variant types is deprecated. If t is an exact
variant type then #t translates to [< t], and #t[> `tag_1 ...`tag_k] translates
to [< t > `tag_1 ...`tag_k]
Variant and record types
------------------------
There are no type expressions describing (defined) variant types nor record
types, since those are always named, i.e. defined before use and referred to by
name. Type definitions are described in section 6.8.1.
6.5 Constants
*=*=*=*=*=*=*=
constant ::= integer-literal
| float-literal
| char-literal
| string-literal
| constr
| false
| true
| []
| ()
| `tag-name
The syntactic class of constants comprises literals from the four base types
(integers, floating-point numbers, characters, character strings), and constant
constructors from both normal and polymorphic variants, as well as the special
constants false, true, [], and (), which behave like constant constructors.
6.6 Patterns
*=*=*=*=*=*=*
pattern ::= value-name
| _
| constant
| pattern as value-name
| ( pattern )
| ( pattern : typexpr )
| pattern | pattern
| constr pattern
| `tag-name pattern
| #typeconstr-name
| pattern { , pattern }
| { field = pattern { ; field = pattern } }
| [ pattern { ; pattern } ]
| pattern :: pattern
| [| pattern { ; pattern } |]
The table below shows the relative precedences and associativity of operators
and non-closed pattern constructions. The constructions with higher precedences
come first.
----------------------------------------
| Operator |Associativity|
----------------------------------------
| Constructor application|-- |
|:: |right |
|, |-- |
|| |left |
|as |-- |
----------------------------------------
Patterns are templates that allow selecting data structures of a given shape,
and binding identifiers to components of the data structure. This selection
operation is called pattern matching; its outcome is either "this value does
not match this pattern", or "this value matches this pattern, resulting in the
following bindings of names to values".
Variable patterns
-----------------
A pattern that consists in a value name matches any value, binding the name
to the value. The pattern _ also matches any value, but does not bind any name.
Patterns are linear: a variable cannot appear several times in a given
pattern. In particular, there is no way to test for equality between two parts
of a data structure using only a pattern (but when guards can be used for this
purpose).
Constant patterns
-----------------
A pattern consisting in a constant matches the values that are equal to this
constant.
Alias patterns
--------------
The pattern pattern_1 as value-name matches the same values as pattern_1. If
the matching against pattern_1 is successful, the name name is bound to the
matched value, in addition to the bindings performed by the matching against
pattern_1.
Parenthesized patterns
----------------------
The pattern ( pattern_1 ) matches the same values as pattern_1. A type
constraint can appear in a parenthesized pattern, as in ( pattern_1 : typexpr
). This constraint forces the type of pattern_1 to be compatible with typexpr.
"Or" patterns
-------------
The pattern pattern_1 | pattern_2 represents the logical "or" of the two
patterns pattern_1 and pattern_2. A value matches pattern_1 | pattern_2 either
if it matches pattern_1 or if it matches pattern_2. The two sub-patterns
pattern_1 and pattern_2 must bind exactly the same identifiers to values having
the same types. Matching is performed from left to right. More precisely, in
case some value v matches pattern_1 | pattern_2, the bindings performed are
those of pattern_1 when v matches pattern_1. Otherwise, value v matches
pattern_2 whose bindings are performed.
Variant patterns
----------------
The pattern constr pattern_1 matches all variants whose constructor is equal
to constr, and whose argument matches pattern_1.
The pattern pattern_1 :: pattern_2 matches non-empty lists whose heads match
pattern_1, and whose tails match pattern_2.
The pattern [ pattern_1 ; ... ; pattern_n ] matches lists of length n whose
elements match pattern_1 ...pattern_n, respectively. This pattern behaves like
pattern_1 :: ... :: pattern_n :: [].
Polymorphic variant patterns
----------------------------
The pattern `tag-name pattern_1 matches all polymorphic variants whose tag is
equal to tag-name, and whose argument matches pattern_1.
Variant abbreviation patterns
-----------------------------
If the type [('a,'b,...)] typeconstr = [`tag_1 typexpr_1 | ... | `tag_n
typexpr_n] is defined, then the pattern #typeconstr is a shorthand for the
or-pattern (`tag_1(_ : typexpr_1) | ... | `tag_n(_ : typexpr_n)). It matches
all values of type #typeconstr.
Tuple patterns
--------------
The pattern pattern_1 , ... , pattern_n matches n-tuples whose components
match the patterns pattern_1 through pattern_n. That is, the pattern matches
the tuple values (v_1, ..., v_n) such that pattern_i matches v_i for i = 1,...
, n.
Record patterns
---------------
The pattern { field_1 = pattern_1 ; ... ; field_n = pattern_n } matches
records that define at least the fields field_1 through field_n, and such that
the value associated to field_i matches the pattern pattern_i, for i = 1,... ,
n. The record value can define more fields than field_1 ...field_n; the values
associated to these extra fields are not taken into account for matching.
Array patterns
--------------
The pattern [| pattern_1 ; ... ; pattern_n |] matches arrays of length n
such that the i-th array element matches the pattern pattern_i, for i = 1,... ,
n.
6.7 Expressions
*=*=*=*=*=*=*=*=
expr ::= value-path
| constant
| ( expr )
| begin expr end
| ( expr : typexpr )
| expr , expr { , expr }
| constr expr
| `tag-name expr
| expr :: expr
| [ expr { ; expr } ]
| [| expr { ; expr } |]
| { field = expr { ; field = expr } }
| { expr with field = expr { ; field = expr } }
+
| expr { argument }
| prefix-symbol expr
| expr infix-op expr
| expr . field
| expr . field <- expr
| expr .( expr )
| expr .( expr ) <- expr
| expr .[ expr ]
| expr .[ expr ] <- expr
| if expr then expr [ else expr ]
| while expr do expr done
| for ident = expr ( to | downto ) expr do expr done
| expr ; expr
| match expr with pattern-matching
| function pattern-matching
| fun multiple-matching
| try expr with pattern-matching
| let [rec] let-binding { and let-binding } in expr
| new class-path
| object class-body end
| expr # method-name
| inst-var-name
| inst-var-name <- expr
| ( expr :> typexpr )
| ( expr : typexpr :> typexpr )
| {< inst-var-name = expr { ; inst-var-name = expr }
>}
| assert expr
| lazy expr
argument ::= expr
| ~ label-name
| ~ label-name : expr
| ? label-name
| ? label-name : expr
pattern-matching ::= [ | ] pattern [when expr] -> expr { | pattern
[when expr] -> expr }
+
multiple-matching ::= { parameter } [when expr] -> expr
let-binding ::= pattern = expr
| value-name { parameter } [: typexpr] = expr
parameter ::= pattern
| ~ label-name
| ~ ( label-name [: typexpr] )
| ~ label-name : pattern
| ? label-name
| ? ( label-name [: typexpr] [= expr] )
| ? label-name : pattern
| ? label-name : ( pattern [: typexpr] [= expr] )
The table below shows the relative precedences and associativity of operators
and non-closed constructions. The constructions with higher precedence come
first. For infix and prefix symbols, we write "*..." to mean "any symbol
starting with *".
---------------------------------------------------------------------------
| Construction or operator |Associativity|
---------------------------------------------------------------------------
| prefix-symbol |-- |
|. .( .[ |-- |
|function application, constructor application, assert, lazy|left |
|- -. (prefix) |-- |
|**... lsl lsr asr |right |
|*... /... %... mod land lor lxor |left |
| +... -... |left |
|:: |right |
|@... ^... |right |
|comparisons (= == < etc.), all other infix symbols |left |
|& && |left |
|or || |left |
|, |-- |
|<- := |right |
|if |-- |
|; |right |
|let match fun function try |-- |
---------------------------------------------------------------------------
6.7.1 Basic expressions
========================
Constants
---------
Expressions consisting in a constant evaluate to this constant.
Value paths
-----------
Expressions consisting in an access path evaluate to the value bound to this
path in the current evaluation environment. The path can be either a value name
or an access path to a value component of a module.
Parenthesized expressions
-------------------------
The expressions ( expr ) and begin expr end have the same value as expr. Both
constructs are semantically equivalent, but it is good style to use begin ...
end inside control structures:
<<
if ... then begin ... ; ... end else begin ... ; ... end
>>
and ( ... ) for the other grouping situations.
Parenthesized expressions can contain a type constraint, as in ( expr :
typexpr ). This constraint forces the type of expr to be compatible with
typexpr.
Parenthesized expressions can also contain coercions ( expr [: typexpr] :>
typexpr) (see subsection 6.7.5 below).
Function application
--------------------
Function application is denoted by juxtaposition of (possibly labeled)
expressions. The expression expr argument_1 ... argument_n evaluates the
expression expr and those appearing in argument_1 to argument_n. The expression
expr must evaluate to a functional value f, which is then applied to the values
of argument_1, ..., argument_n.
The order in which the expressions expr, argument_1, ..., argument_n are
evaluated is not specified.
Arguments and parameters are matched according to their respective labels.
Argument order is irrelevant, except among arguments with the same label, or no
label.
If a parameter is specified as optional (label prefixed by ?) in the type of
expr, the corresponding argument will be automatically wrapped with the
constructor Some, except if the argument itself is also prefixed by ?, in which
case it is passed as is. If a non-labeled argument is passed, and its
corresponding parameter is preceded by one or several optional parameters, then
these parameters are defaulted, i.e. the value None will be passed for them.
All other missing parameters (without corresponding argument), both optional
and non-optional, will be kept, and the result of the function will still be a
function of these missing parameters to the body of f.
As a special case, if the function has a known arity, all the arguments are
unlabeled, and their number matches the number of non-optional parameters, then
labels are ignored and non-optional parameters are matched in their definition
order. Optional arguments are defaulted.
In all cases but exact match of order and labels, without optional
parameters, the function type should be known at the application point. This
can be ensured by adding a type constraint. Principality of the derivation can
be checked in the -principal mode.
Function definition
-------------------
Two syntactic forms are provided to define functions. The first form is
introduced by the keyword function:
function pattern -> expr
1 1
| ...
| pattern -> expr
n n
This expression evaluates to a functional value with one argument. When this
function is applied to a value v, this value is matched against each pattern
pattern_1 to pattern_n. If one of these matchings succeeds, that is, if the
value v matches the pattern pattern_i for some i, then the expression expr_i
associated to the selected pattern is evaluated, and its value becomes the
value of the function application. The evaluation of expr_i takes place in an
environment enriched by the bindings performed during the matching.
If several patterns match the argument v, the one that occurs first in the
function definition is selected. If none of the patterns matches the argument,
the exception Match_failure is raised.
The other form of function definition is introduced by the keyword fun:
fun parameter_1 ... parameter_n -> expr
This expression is equivalent to:
fun parameter_1 -> ... fun parameter_n -> expr
Functions of the form fun optlabel ( pattern = expr_0 ) -> expr are
equivalent to
fun optlabel ident -> let pattern = match ident with Some ident ->
ident | None -> expr_0 in expr
where ident is a fresh variable. When expr_0 will be evaluated is left
unspecified.
After these two transformations, expressions are of the form
fun [label_1] pattern_1 -> ... fun [label_n] pattern_n -> expr
If we ignore labels, which will only be meaningful at function application,
this is equivalent to
function pattern_1 -> ... function pattern_n -> expr
That is, the fun expression above evaluates to a curried function with n
arguments: after applying this function n times to the values v_1 ... v_m, the
values will be matched in parallel against the patterns pattern_1 ...
pattern_n. If the matching succeeds, the function returns the value of expr in
an environment enriched by the bindings performed during the matchings. If the
matching fails, the exception Match_failure is raised.
Guards in pattern-matchings
---------------------------
Cases of a pattern matching (in the function, fun, match and try constructs)
can include guard expressions, which are arbitrary boolean expressions that
must evaluate to true for the match case to be selected. Guards occur just
before the -> token and are introduced by the when keyword:
function pattern [when cond ] -> expr
1 1 1
| ...
| pattern [when cond ] -> expr
n n n
Matching proceeds as described before, except that if the value matches some
pattern pattern_i which has a guard cond_i, then the expression cond_i is
evaluated (in an environment enriched by the bindings performed during
matching). If cond_i evaluates to true, then expr_i is evaluated and its value
returned as the result of the matching, as usual. But if cond_i evaluates to
false, the matching is resumed against the patterns following pattern_i.
Local definitions
-----------------
The let and let rec constructs bind value names locally. The construct
let pattern_1 = expr_1 and ... and pattern_n = expr_n in expr
evaluates expr_1 ... expr_n in some unspecified order, then matches their
values against the patterns pattern_1 ... pattern_n. If the matchings succeed,
expr is evaluated in the environment enriched by the bindings performed during
matching, and the value of expr is returned as the value of the whole let
expression. If one of the matchings fails, the exception Match_failure is
raised.
An alternate syntax is provided to bind variables to functional values:
instead of writing
let ident = fun parameter_1 ... parameter_m -> expr
in a let expression, one may instead write
let ident parameter_1 ... parameter_m = expr
Recursive definitions of names are introduced by let rec:
let rec pattern_1 = expr_1 and ... and pattern_n = expr_n in expr
The only difference with the let construct described above is that the
bindings of names to values performed by the pattern-matching are considered
already performed when the expressions expr_1 to expr_n are evaluated. That is,
the expressions expr_1 to expr_n can reference identifiers that are bound by
one of the patterns pattern_1, ..., pattern_n, and expect them to have the
same value as in expr, the body of the let rec construct.
The recursive definition is guaranteed to behave as described above if the
expressions expr_1 to expr_n are function definitions (fun ... or function
...), and the patterns pattern_1 ... pattern_n are just value names, as in:
let rec name_1 = fun ... and ... and name_n = fun ... in expr
This defines name_1 ... name_n as mutually recursive functions local to
expr.
The behavior of other forms of let rec definitions is
implementation-dependent. The current implementation also supports a certain
class of recursive definitions of non-functional values, as explained in
section 7.3.
6.7.2 Control structures
=========================
Sequence
--------
The expression expr_1 ; expr_2 evaluates expr_1 first, then expr_2, and
returns the value of expr_2.
Conditional
-----------
The expression if expr_1 then expr_2 else expr_3 evaluates to the value of
expr_2 if expr_1 evaluates to the boolean true, and to the value of expr_3 if
expr_1 evaluates to the boolean false.
The else expr_3 part can be omitted, in which case it defaults to else ().
Case expression
---------------
The expression
match expr
with pattern -> expr
1 1
| ...
| pattern -> expr
n n
matches the value of expr against the patterns pattern_1 to pattern_n. If
the matching against pattern_i succeeds, the associated expression expr_i is
evaluated, and its value becomes the value of the whole match expression. The
evaluation of expr_i takes place in an environment enriched by the bindings
performed during matching. If several patterns match the value of expr, the one
that occurs first in the match expression is selected. If none of the patterns
match the value of expr, the exception Match_failure is raised.
Boolean operators
-----------------
The expression expr_1 && expr_2 evaluates to true if both expr_1 and expr_2
evaluate to true; otherwise, it evaluates to false. The first component,
expr_1, is evaluated first. The second component, expr_2, is not evaluated if
the first component evaluates to false. Hence, the expression expr_1 && expr_2
behaves exactly as
if expr_1 then expr_2 else false.
The expression expr_1 || expr_2 evaluates to true if one of expr_1 and
expr_2 evaluates to true; otherwise, it evaluates to false. The first
component, expr_1, is evaluated first. The second component, expr_2, is not
evaluated if the first component evaluates to true. Hence, the expression
expr_1 || expr_2 behaves exactly as
if expr_1 then true else expr_2.
The boolean operator & is synonymous for &&. The boolean operator or is
synonymous for ||.
Loops
-----
The expression while expr_1 do expr_2 done repeatedly evaluates expr_2
while expr_1 evaluates to true. The loop condition expr_1 is evaluated and
tested at the beginning of each iteration. The whole while ... done expression
evaluates to the unit value ().
The expression for name = expr_1 to expr_2 do expr_3 done first evaluates
the expressions expr_1 and expr_2 (the boundaries) into integer values n and p.
Then, the loop body expr_3 is repeatedly evaluated in an environment where name
is successively bound to the values n, n+1, ..., p-1, p. The loop body is never
evaluated if n > p.
The expression for name = expr_1 downto expr_2 do expr_3 done evaluates
similarly, except that name is successively bound to the values n, n-1, ...,
p+1, p. The loop body is never evaluated if n < p.
In both cases, the whole for expression evaluates to the unit value ().
Exception handling
------------------
The expression
try expr
with pattern -> expr
1 1
| ...
| pattern -> expr
n n
evaluates the expression expr and returns its value if the evaluation of
expr does not raise any exception. If the evaluation of expr raises an
exception, the exception value is matched against the patterns pattern_1 to
pattern_n. If the matching against pattern_i succeeds, the associated
expression expr_i is evaluated, and its value becomes the value of the whole
try expression. The evaluation of expr_i takes place in an environment enriched
by the bindings performed during matching. If several patterns match the value
of expr, the one that occurs first in the try expression is selected. If none
of the patterns matches the value of expr, the exception value is raised again,
thereby transparently "passing through" the try construct.
6.7.3 Operations on data structures
====================================
Products
--------
The expression expr_1 , ... , expr_n evaluates to the n-tuple of the values
of expressions expr_1 to expr_n. The evaluation order for the subexpressions is
not specified.
Variants
--------
The expression constr expr evaluates to the variant value whose constructor
is constr, and whose argument is the value of expr.
For lists, some syntactic sugar is provided. The expression expr_1 :: expr_2
stands for the constructor ( :: ) applied to the argument ( expr_1 , expr_2
), and therefore evaluates to the list whose head is the value of expr_1 and
whose tail is the value of expr_2. The expression [ expr_1 ; ... ; expr_n ] is
equivalent to expr_1 :: ... :: expr_n :: [], and therefore evaluates to the
list whose elements are the values of expr_1 to expr_n.
Polymorphic variants
--------------------
The expression `tag-name expr evaluates to the variant value whose tag is
tag-name, and whose argument is the value of expr.
Records
-------
The expression { field_1 = expr_1 ; ... ; field_n = expr_n } evaluates to
the record value { field_1 = v_1; ...; field_n = v_n } where v_i is the value
of expr_i for i = 1,... , n. The fields field_1 to field_n must all belong to
the same record types; all fields belonging to this record type must appear
exactly once in the record expression, though they can appear in any order. The
order in which expr_1 to expr_n are evaluated is not specified.
The expression { expr with field_1 = expr_1 ; ... ; field_n = expr_n }
builds a fresh record with fields field_1 ... field_n equal to expr_1 ...
expr_n, and all other fields having the same value as in the record expr. In
other terms, it returns a shallow copy of the record expr, except for the
fields field_1 ... field_n, which are initialized to expr_1 ... expr_n.
The expression expr_1 . field evaluates expr_1 to a record value, and
returns the value associated to field in this record value.
The expression expr_1 . field <- expr_2 evaluates expr_1 to a record value,
which is then modified in-place by replacing the value associated to field in
this record by the value of expr_2. This operation is permitted only if field
has been declared mutable in the definition of the record type. The whole
expression expr_1 . field <- expr_2 evaluates to the unit value ().
Arrays
------
The expression [| expr_1 ; ... ; expr_n |] evaluates to a n-element array,
whose elements are initialized with the values of expr_1 to expr_n
respectively. The order in which these expressions are evaluated is
unspecified.
The expression expr_1 .( expr_2 ) returns the value of element number expr_2
in the array denoted by expr_1. The first element has number 0; the last
element has number n-1, where n is the size of the array. The exception
Invalid_argument is raised if the access is out of bounds.
The expression expr_1 .( expr_2 ) <- expr_3 modifies in-place the array
denoted by expr_1, replacing element number expr_2 by the value of expr_3. The
exception Invalid_argument is raised if the access is out of bounds. The value
of the whole expression is ().
Strings
-------
The expression expr_1 .[ expr_2 ] returns the value of character number
expr_2 in the string denoted by expr_1. The first character has number 0; the
last character has number n-1, where n is the length of the string. The
exception Invalid_argument is raised if the access is out of bounds.
The expression expr_1 .[ expr_2 ] <- expr_3 modifies in-place the string
denoted by expr_1, replacing character number expr_2 by the value of expr_3.
The exception Invalid_argument is raised if the access is out of bounds. The
value of the whole expression is ().
6.7.4 Operators
================
Symbols from the class infix-symbols, as well as the keywords *, =, or and &,
can appear in infix position (between two expressions). Symbols from the class
prefix-symbols can appear in prefix position (in front of an expression).
Infix and prefix symbols do not have a fixed meaning: they are simply
interpreted as applications of functions bound to the names corresponding to
the symbols. The expression prefix-symbol expr is interpreted as the
application ( prefix-symbol ) expr. Similarly, the expression expr_1
infix-symbol expr_2 is interpreted as the application ( infix-symbol ) expr_1
expr_2.
The table below lists the symbols defined in the initial environment and
their initial meaning. (See the description of the standard library module
Pervasive in chapter 20 for more details). Their meaning may be changed at any
time using let ( infix-op ) name_1 name_2 = ...
------------------------------------------------
| Operator | Initial meaning |
------------------------------------------------
| + |Integer addition. |
|- (infix) |Integer subtraction. |
|- (prefix) |Integer negation. |
|* |Integer multiplication. |
|/ |Integer division. Raise |
| |Division_by_zero if second |
| |argument is zero. |
|mod |Integer modulus. Raise |
| |Division_by_zero if second |
| |argument is zero. |
|land |Bitwise logical "and" on integers.|
| | |
|lor |Bitwise logical "or" on integers. |
|lxor |Bitwise logical "exclusive or" on |
| |integers. |
|lsl |Bitwise logical shift left on |
| |integers. |
|lsr |Bitwise logical shift right on |
| |integers. |
|asr |Bitwise arithmetic shift right on |
| |integers. |
|+. |Floating-point addition. |
|-. (infix) |Floating-point subtraction. |
|-. (prefix)|Floating-point negation. |
|*. |Floating-point multiplication. |
|/. |Floating-point division. |
|** |Floating-point exponentiation. |
|@ |List concatenation. |
|^ |String concatenation. |
|! |Dereferencing (return the current |
| |contents of a reference). |
|:= |Reference assignment (update the |
| |reference given as first argument |
| |with the value of the second |
| |argument). |
|= |Structural equality test. |
|<> |Structural inequality test. |
|== |Physical equality test. |
|!= |Physical inequality test. |
|< |Test "less than". |
|<= |Test "less than or equal". |
|> |Test "greater than". |
|>= |Test "greater than or equal". |
------------------------------------------------
6.7.5 Objects
==============
Object creation
---------------
When class-path evaluates to a class body, new class-path evaluates to an
object containing the instance variables and methods of this class.
When class-path evaluates to a class function, new class-path evaluates to a
function expecting the same number of arguments and returning a new object of
this class.
Immediate object creation
-------------------------
Creating directly an object through the object class-body end construct is
operationally equivalent to defining locally a class class-name = object
class-body end ---see sections 6.9.2 and following for the syntax of
class-body--- and immediately creating a single object from it by new
class-name.
The typing of immediate objects is slightly different from explicitely
defining a class in two respects. First, the inferred object type may contain
free type variables. Second, since the class body of an immediate object will
never be extended, its self type can be unified with a closed object type.
Message sending
---------------
The expression expr # method-name invokes the method method-name of the
object denoted by expr.
If method-name is a polymorphic method, its type should be known at the
invocation site. This is true for instance if expr is the name of a fresh
object (let ident = new class-path ... ) or if there is a type constraint.
Principality of the derivation can be checked in the -principal mode.
Accessing and modifying instance variables
------------------------------------------
The instance variables of a class are visible only in the body of the methods
defined in the same class or a class that inherits from the class defining the
instance variables. The expression inst-var-name evaluates to the value of the
given instance variable. The expression inst-var-name <- expr assigns the
value of expr to the instance variable inst-var-name, which must be mutable.
The whole expression inst-var-name <- expr evaluates to ().
Coercion
--------
The type of an object can be coerced (weakened) to a supertype. The
expression (expr :> typexpr) coerces the expression expr to type typexpr. The
expression (expr : typexpr_1 :> typexpr_2) coerces the expression expr from
type typexpr_1 to type typexpr_2. The former operator will sometimes fail to
coerce an expression expr from a type t_1 to a type t_2 even if type t_1 is a
subtype of type t_2: in the current implementation it only expands two levels
of type abbreviations containing objects and/or variants, keeping only
recursion when it is explicit in the class type. In case of failure, the latter
operator should be used.
In a class definition, coercion to the type this class defines is the
identity, as this type abbreviation is not yet completely defined.
Object duplication
------------------
An object can be duplicated using the library function Oo.copy (see section
20.21). Inside a method, the expression {< inst-var-name = expr { ;
inst-var-name = expr } >} returns a copy of self with the given instance
variables replaced by the values of the associated expressions; other instance
variables have the same value in the returned object as in self.
6.8 Type and exception definitions
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
6.8.1 Type definitions
=======================
Type definitions bind type constructors to data types: either variant types,
record types, type abbreviations, or abstract data types. They also bind the
value constructors and record fields associated with the definition.
type-definition ::= type typedef { and typedef }
typedef ::= [type-params] typeconstr-name [type-information]
type-information ::= [type-equation] [type-representation] {
type-constraint }
type-equation ::= = typexpr
type-representation ::= = constr-decl { | constr-decl }
| = { field-decl { ; field-decl } }
type-params ::= type-param
| ( type-param { , type-param } )
type-param ::= ' ident
| + ' ident
| - ' ident
constr-decl ::= constr-name
| constr-name of typexpr { * typexpr }
field-decl ::= field-name : poly-typexpr
| mutable field-name : poly-typexpr
type-constraint ::= constraint ' ident = typexpr
Type definitions are introduced by the type keyword, and consist in one or
several simple definitions, possibly mutually recursive, separated by the and
keyword. Each simple definition defines one type constructor.
A simple definition consists in a lowercase identifier, possibly preceded by
one or several type parameters, and followed by an optional type equation, then
an optional type representation, and then a constraint clause. The identifier
is the name of the type constructor being defined.
The optional type parameters are either one type variable ' ident, for type
constructors with one parameter, or a list of type variables ('ident_1,...,'
ident_n), for type constructors with several parameters. Each type parameter
may be prefixed by a variance constraint + (resp. -) indicating that the
parameter is covariant (resp. contravariant). These type parameters can appear
in the type expressions of the right-hand side of the definition, restricted
eventually by a variance constraint ; i.e. a covariant parameter may only
appear on the right side of a functional arrow (more precisely, follow the left
branch of an even number of arrows), and a contravariant parameter only the
left side (left branch of an odd number of arrows). If the type has either a
representation or an equation, and the parameter is free (i.e. not bound via a
type constraint to a constructed type), its variance constraint is checked but
subtyping etc. will use the inferred variance of the parameter, which may be
better; otherwise (i.e. for abstract types or non-free parameters), the
variance must be given explicitly, and the parameter is invariant if no
variance was given.
The optional type equation = typexpr makes the defined type equivalent to the
type expression typexpr on the right of the = sign: one can be substituted for
the other during typing. If no type equation is given, a new type is generated:
the defined type is incompatible with any other type.
The optional type representation describes the data structure representing
the defined type, by giving the list of associated constructors (if it is a
variant type) or associated fields (if it is a record type). If no type
representation is given, nothing is assumed on the structure of the type
besides what is stated in the optional type equation.
The type representation = constr-decl { | constr-decl } describes a variant
type. The constructor declarations constr-decl_1, ..., constr-decl_n describe
the constructors associated to this variant type. The constructor declaration
constr-name of typexpr_1, ..., typexpr_n declares the name constr-name as a
non-constant constructor, whose arguments have types typexpr_1 ...typexpr_n.
The constructor declaration constr-name declares the name constr-name as a
constant constructor. Constructor names must be capitalized.
The type representation = { field-decl { ; field-decl } } describes a record
type. The field declarations field-decl_1, ..., field-decl_n describe the
fields associated to this record type. The field declaration field-name :
poly-typexpr declares field-name as a field whose argument has type
poly-typexpr. The field declaration mutable field-name : poly-typexpr behaves
similarly; in addition, it allows physical modification over the argument to
this field. Immutable fields are covariant, but mutable fields are neither
covariant nor contravariant. Both mutable and immutable field may have an
explicitly polymorphic type. The polymorphism of the contents is statically
checked whenever a record value is created or modified. Extracted values may
have their types instanciated.
The two components of a type definition, the optional equation and the
optional representation, can be combined independently, giving rise to four
typical situations:
Abstract type: no equation, no representation.
When appearing in a module signature, this definition specifies nothing on the
type constructor, besides its number of parameters: its representation is
hidden and it is assumed incompatible with any other type.
Type abbreviation: an equation, no representation.
This defines the type constructor as an abbreviation for the type expression
on the right of the = sign.
New variant type or record type: no equation, a representation.
This generates a new type constructor and defines associated constructors or
fields, through which values of that type can be directly built or
inspected.
Re-exported variant type or record type: an equation, a representation.
In this case, the type constructor is defined as an abbreviation for the type
expression given in the equation, but in addition the constructors or fields
given in the representation remain attached to the defined type constructor.
The type expression in the equation part must agree with the representation:
it must be of the same kind (record or variant) and have exactly the same
constructors or fields, in the same order, with the same arguments.
The type variables appearing as type parameters can optionally be prefixed by
+ or - to indicate that the type constructor is covariant or contravariant with
respect to this parameter. This variance information is used to decide
subtyping relations when checking the validity of :> coercions (see section
6.7.5).
For instance, type +'a t declares t as an abstract type that is covariant in
its parameter; this means that if the type tau is a subtype of the type sigma,
then tau t is a subtype of sigma t. Similarly, type -'a t declares that the
abstract type t is contravariant in its parameter: if tau is subtype of sigma,
then sigma t is subtype of tau t. If no + or - variance annotation is
given, the type constructor is assumed invariant in the corresponding
parameter. For instance, the abstract type declaration type 'a t means that tau
t is neither a subtype nor a supertype of sigma t if tau is subtype of
sigma.
The variance indicated by the + and - annotations on parameters are required
only for abstract types. For abbreviations, variant types or record types, the
variance properties of the type constructor are inferred from its definition,
and the variance annotations are only checked for conformance with the
definition.
The construct constraint ' ident = typexpr allows to specify type
parameters. Any actual type argument corresponding to the type parameter ident
has to be an instance of typexpr (more precisely, ident and typexpr are
unified). Type variables of typexpr can appear in the type equation and the
type declaration.
6.8.2 Exception definitions
============================
exception-definition ::= exception constr-name [of typexpr { * typexpr }]
| exception constr-name = constr
Exception definitions add new constructors to the built-in variant type `exn'
of exception values. The constructors are declared as for a definition of a
variant type.
The form exception constr-name [of typexpr { * typexpr }] generates a new
exception, distinct from all other exceptions in the system. The form exception
constr-name = constr gives an alternate name to an existing exception.
6.9 Classes
*=*=*=*=*=*=
Classes are defined using a small language, similar to the module language.
6.9.1 Class types
==================
Class types are the class-level equivalent of type expressions: they specify
the general shape and type properties of classes.
class-type ::= class-body-type
| [[?]label-name:] typexpr -> class-type
class-body-type ::= object [( typexpr )] {class-field-spec} end
| class-path
| [ typexpr {, typexpr} ] class-path
class-field-spec ::= inherit class-type
| val [mutable] [virtual] inst-var-name : typexpr
| method [private] method-name : poly-typexpr
| method [private] virtual method-name : poly-typexpr
| constraint typexpr = typexpr
Simple class expressions
------------------------
The expression class-path is equivalent to the class type bound to the name
class-path. Similarly, the expression [ typexpr_1 , ... typexpr_n ]
class-path is equivalent to the parametric class type bound to the name
class-path, in which type parameters have been instanciated to respectively
typexpr_1, ...typexpr_n.
Class function type
-------------------
The class type expression typexpr -> class-type is the type of class
functions (functions from values to classes) that take as argument a value of
type typexpr and return as result a class of type class-type.
Class body type
---------------
The class type expression object [( typexpr )] {class-field-spec} end is the
type of a class body. It specifies its instance variables and methods. In this
type, typexpr is matched against the self type, therefore providing a binding
for the self type.
A class body will match a class body type if it provides definitions for all
the components specified in the class type, and these definitions meet the type
requirements given in the class type. Furthermore, all methods either virtual
or public present in the class body must also be present in the class type (on
the other hand, some instance variables and concrete private methods may be
omitted). A virtual method will match a concrete method, which makes it
possible to forget its implementation. An immutable instance variable will
match a mutable instance variable.
Inheritance
-----------
The inheritance construct inherit class-type allows to include methods and
instance variables from other classes types. The instance variable and method
types from this class type are added into the current class type.
Instance variable specification
-------------------------------
A specification of an instance variable is written val [mutable] [virtual]
inst-var-name : typexpr, where inst-var-name is the name of the instance
variable and typexpr its expected type. The flag mutable indicates whether this
instance variable can be physically modified. The flag virtual indicates that
this instance variable is not initialized. It can be initialized later through
inheritance.
An instance variable specification will hide any previous specification of an
instance variable of the same name.
Method specification
--------------------
The specification of a method is written method [private] method-name :
poly-typexpr, where method-name is the name of the method and poly-typexpr its
expected type, possibly polymorphic. The flag private indicates that the method
cannot be accessed from outside the object.
The polymorphism may be left implicit in public method specifications: any
type variable which is not bound to a class parameter and does not appear
elsewhere inside the class specification will be assumed to be universal, and
made polymorphic in the resulting method type. Writing an explicit polymorphic
type will disable this behaviour.
Several specification for the same method must have compatible types. Any
non-private specification of a method forces it to be public.
Virtual method specification
----------------------------
Virtual method specification is written method [private] virtual method-name
: poly-typexpr, where method-name is the name of the method and poly-typexpr
its expected type.
Constraints on type parameters
------------------------------
The construct constraint typexpr_1 = typexpr_2 forces the two type
expressions to be equals. This is typically used to specify type parameters:
they can be that way be bound to a specified type expression.
6.9.2 Class expressions
========================
Class expressions are the class-level equivalent of value expressions: they
evaluate to classes, thus providing implementations for the specifications
expressed in class types.
class-expr ::= class-path
| [ typexpr {, typexpr} ] class-path
| ( class-expr )
| ( class-expr : class-type )
+
| class-expr {argument}
+
| fun {parameter} -> class-expr
| let [rec] let-binding {and let-binding} in class-expr
| object [( pattern [: typexpr] )] { class-field } end
class-field ::= inherit class-expr [as value-name]
| val [mutable] inst-var-name [: typexpr] = expr
| val [mutable] virtual inst-var-name : typexpr
| method [private] method-name {parameter} [: typexpr] =
expr
| method [private] method-name : poly-typexpr = expr
| method [private] virtual method-name : poly-typexpr
| constraint typexpr = typexpr
| initializer expr
Simple class expressions
------------------------
The expression class-path evaluates to the class bound to the name
class-path. Similarly, the expression [ typexpr_1 , ... typexpr_n ]
class-path evaluates to the parametric class bound to the name class-path, in
which type parameters have been instanciated to respectively typexpr_1,
...typexpr_n.
The expression ( class-expr ) evaluates to the same module as class-expr.
The expression ( class-expr : class-type ) checks that class-type match the
type of class-expr (that is, that the implementation class-expr meets the type
specification class-type). The whole expression evaluates to the same class as
class-expr, except that all components not specified in class-type are hidden
and can no longer be accessed.
Class application
-----------------
Class application is denoted by juxtaposition of (possibly labeled)
expressions. Evaluation works as for expression application.
Class function
--------------
The expression fun [[?]label-name:] pattern -> class-expr evaluates to a
function from values to classes. When this function is applied to a value v,
this value is matched against the pattern pattern and the result is the result
of the evaluation of class-expr in the extended environment.
Conversion from functions with default values to functions with patterns only
works identically for class functions as for normal functions.
The expression
fun parameter_1 ... parameter_n -> class-expr
is a short form for
fun parameter_1 -> ... fun parameter_n -> expr
Local definitions
-----------------
The let and let rec constructs bind value names locally, as for the core
language expressions.
Class body
----------
class-body ::= [( pattern [: typexpr] )] { class-field }
The expression object class-body end denotes a class body. This is the
prototype for an object : it lists the instance variables and methods of an
objet of this class.
A class body is a class value: it is not evaluated at once. Rather, its
components are evaluated each time an object is created.
In a class body, the pattern ( pattern [: typexpr] ) is matched against
self, therefore provinding a binding for self and self type. Self can only be
used in method and initializers.
Self type cannot be a closed object type, so that the class remains
extensible.
Inheritance
-----------
The inheritance construct inherit class-expr allows to reuse methods and
instance variables from other classes. The class expression class-expr must
evaluate to a class body. The instance variables, methods and initializers from
this class body are added into the current class. The addition of a method will
override any previously defined methods of the same name.
An ancestor can be bound by prepending the construct as value-name to the
inheritance construct above. value-name is not a true variable and can only be
used to select a method, i.e. in an expression value-name # method-name. This
gives access to the method method-name as it was defined in the parent class
even if it is redefined in the current class. The scope of an ancestor binding
is limited to the current class. The ancestor method may be called from a
subclass but only indirectly.
Instance variable definition
----------------------------
The definition val [mutable] inst-var-name = expr adds an instance variable
inst-var-name whose initial value is the value of expression expr. The flag
mutable allows physical modification of this variable by methods.
An instance variables can only be used in the following methods and
initializers of the class.
Since version 3.10, redefinitions of a visible instance variable with the
same name do not create a new variable, but are merged, using the last value
for initialization. They must have identical types and mutability. However, if
an instance variable is hidden by omitting it from an interface, it will be
kept distinct from other instance variables with the same name.
Virtual instance variable definition
------------------------------------
Variable specification is written val [mutable] virtual inst-var-name :
typexpr. It specifies whether the variable is modifiable, and gives its type.
Virtual instance variables were added in version 3.10.
Method definition
-----------------
Method definition is written method method-name = expr. The definition of a
method overrides any previous definition of this method. The method will be
public (that is, not private) if any of the definition states so.
A private method, method private method-name = expr, is a method that can
only be invoked on self (from other methods of the same object, defined in this
class or one of its subclasses). This invocation is performed using the
expression value-name # method-name, where value-name is directly bound to
self at the beginning of the class definition. Private methods do not appear in
object types. A method may have both public and private definitions, but as
soon as there is a public one, all subsequent definitions will be made public.
Methods may have an explicitly polymorphic type, allowing them to be used
polymorphically in programs (even for the same object). The explicit
declaration may be done in one of three ways: (1) by giving an explicit
polymorphic type in the method definition, immediately after the method name,
i.e. method [private] method-name : {' ident}^+ . typexpr = expr; (2) by a
forward declaration of the explicit polymorphic type through a virtual method
definition; (3) by importing such a declaration through inheritance and/or
constraining the type of self.
Some special expressions are available in method bodies for manipulating
instance variables and duplicating self:
expr ::= ...
| inst-var-name <- expr
| {< [ inst-var-name = expr { ; inst-var-name = expr } ] >}
The expression inst-var-name <- expr modifies in-place the current object by
replacing the value associated to inst-var-name by the value of expr. Of
course, this instance variable must have been declared mutable.
The expression {< [ inst-var-name = expr { ; inst-var-name = expr } ] >}
evaluates to a copy of the current object in which the values of instance
variables inst-var-name_1, ..., inst-var-name_n have been replaced by the
values of the corresponding expressions expr_1, ..., expr_n.
Virtual method definition
-------------------------
Method specification is written method [private] virtual method-name :
poly-typexpr. It specifies whether the method is public or private, and gives
its type. If the method is intended to be polymorphic, the type should be
explicit.
Constraints on type parameters
------------------------------
The construct constraint typexpr_1 = typexpr_2 forces the two type
expressions to be equals. This is typically used to specify type parameters:
they can be that way be bound to a specified type expression.
Initializers
------------
A class initializer initializer expr specifies an expression that will be
evaluated when an object will be created from the class, once all the instance
variables have been initialized.
6.9.3 Class definitions
========================
class-definition ::= class class-binding { and class-binding }
class-binding ::= [virtual] [[ type-parameters ]] class-name
{parameter} [: class-type] = class-expr
type-parameters ::= ' ident { , ' ident }
A class definition class class-binding { and class-binding } is recursive.
Each class-binding defines a class-name that can be used in the whole
expression except for inheritance. It can also be used for inheritance, but
only in the definitions that follow its own.
A class binding binds the class name class-name to the value of expression
class-expr. It also binds the class type class-name to the type of the class,
and defines two type abbreviations : class-name and # class-name. The first one
is the type of objects of this class, while the second is more general as it
unifies with the type of any object belonging to a subclass (see section 6.4).
Virtual class
-------------
A class must be flagged virtual if one of its methods is virtual (that is,
appears in the class type, but is not actually defined). Objects cannot be
created from a virtual class.
Type parameters
---------------
The class type parameters correspond to the ones of the class type and of the
two type abbreviations defined by the class binding. They must be bound to
actual types in the class definition using type constraints. So that the
abbreviations are well-formed, type variables of the inferred type of the class
must either be type parameters or be bound in the constraint clause.
6.9.4 Class specification
==========================
class-specification ::= class class-spec { and class-spec }
class-spec ::= [virtual] [[ type-parameters ]] class-name :
class-type
This is the counterpart in signatures of class definitions. A class
specification matches a class definition if they have the same type parameters
and their types match.
6.9.5 Class type definitions
=============================
classtype-definition ::= class type classtype-def { and classtype-def }
classtype-def ::= [virtual] [[ type-parameters ]] class-name =
class-body-type
A class type definition class class-name = class-body-type defines an
abbreviation class-name for the class body type class-body-type. As for class
definitions, two type abbreviations class-name and # class-name are also
defined. The definition can be parameterized by some type parameters. If any
method in the class type body is virtual, the definition must be flagged
virtual.
Two class type definitions match if they have the same type parameters and
the types they expand to match.
6.10 Module types (module specifications)
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Module types are the module-level equivalent of type expressions: they
specify the general shape and type properties of modules.
module-type ::= modtype-path
| sig { specification [;;] } end
| functor ( module-name : module-type ) -> module-type
| module-type with mod-constraint { and mod-constraint }
| ( module-type )
mod-constraint ::= type [type-parameters] typeconstr = typexpr
| module module-path = extended-module-path
specification ::= val value-name : typexpr
| external value-name : typexpr = external-declaration
| type-definition
| exception constr-decl
| class-specification
| classtype-definition
| module module-name : module-type
| module module-name { ( module-name : module-type ) } :
module-type
| module type modtype-name
| module type modtype-name = module-type
| open module-path
| include module-type
6.10.1 Simple module types
===========================
The expression modtype-path is equivalent to the module type bound to the
name modtype-path. The expression ( module-type ) denotes the same type as
module-type.
6.10.2 Signatures
==================
Signatures are type specifications for structures. Signatures sig ... end are
collections of type specifications for value names, type names, exceptions,
module names and module type names. A structure will match a signature if the
structure provides definitions (implementations) for all the names specified in
the signature (and possibly more), and these definitions meet the type
requirements given in the signature.
For compatibility with Caml Light, an optional ;; is allowed after each
specification in a signature. The ;; has no semantic meaning.
Value specifications
--------------------
A specification of a value component in a signature is written val value-name
: typexpr, where value-name is the name of the value and typexpr its expected
type.
The form external value-name : typexpr = external-declaration is similar,
except that it requires in addition the name to be implemented as the external
function specified in external-declaration (see chapter 18).
Type specifications
-------------------
A specification of one or several type components in a signature is written
type typedef { and typedef } and consists of a sequence of mutually recursive
definitions of type names.
Each type definition in the signature specifies an optional type equation =
typexpr and an optional type representation = constr-decl ... or = {
field-decl ... }. The implementation of the type name in a matching structure
must be compatible with the type expression specified in the equation (if
given), and have the specified representation (if given). Conversely, users of
that signature will be able to rely on the type equation or type
representation, if given. More precisely, we have the following four
situations:
Abstract type: no equation, no representation.
Names that are defined as abstract types in a signature can be implemented in
a matching structure by any kind of type definition (provided it has the
same number of type parameters). The exact implementation of the type will
be hidden to the users of the structure. In particular, if the type is
implemented as a variant type or record type, the associated constructors
and fields will not be accessible to the users; if the type is implemented
as an abbreviation, the type equality between the type name and the
right-hand side of the abbreviation will be hidden from the users of the
structure. Users of the structure consider that type as incompatible with
any other type: a fresh type has been generated.
Type abbreviation: an equation = typexpr, no representation.
The type name must be implemented by a type compatible with typexpr. All users
of the structure know that the type name is compatible with typexpr.
New variant type or record type: no equation, a representation.
The type name must be implemented by a variant type or record type with
exactly the constructors or fields specified. All users of the structure
have access to the constructors or fields, and can use them to create or
inspect values of that type. However, users of the structure consider that
type as incompatible with any other type: a fresh type has been generated.
Re-exported variant type or record type: an equation, a representation.
This case combines the previous two: the representation of the type is made
visible to all users, and no fresh type is generated.
Exception specification
-----------------------
The specification exception constr-decl in a signature requires the matching
structure to provide an exception with the name and arguments specified in the
definition, and makes the exception available to all users of the structure.
Class specifications
--------------------
A specification of one or several classes in a signature is written class
class-spec { and class-spec } and consists of a sequence of mutually recursive
definitions of class names.
Class specifications are described more precisely in section 6.9.4.
Class type specifications
-------------------------
A specification of one or several classe types in a signature is written
class type classtype-def { and classtype-def } and consists of a sequence of
mutually recursive definitions of class type names. Class type specifications
are described more precisely in section 6.9.5.
Module specifications
---------------------
A specification of a module component in a signature is written module
module-name : module-type, where module-name is the name of the module
component and module-type its expected type. Modules can be nested arbitrarily;
in particular, functors can appear as components of structures and functor
types as components of signatures.
For specifying a module component that is a functor, one may write
module module-name ( name_1 : module-type_1 ) ... ( name_n :
module-type_n ) : module-type
instead of
module module-name : functor ( name_1 : module-type_1 ) -> ... ->
module-type
Module type specifications
--------------------------
A module type component of a signature can be specified either as a manifest
module type or as an abstract module type.
An abstract module type specification module type modtype-name allows the
name modtype-name to be implemented by any module type in a matching signature,
but hides the implementation of the module type to all users of the signature.
A manifest module type specification module type modtype-name = module-type
requires the name modtype-name to be implemented by the module type module-type
in a matching signature, but makes the equality between modtype-name and
module-type apparent to all users of the signature.
Opening a module path
---------------------
The expression open module-path in a signature does not specify any
components. It simply affects the parsing of the following items of the
signature, allowing components of the module denoted by module-path to be
referred to by their simple names name instead of path accesses module-path .
name. The scope of the open stops at the end of the signature expression.
Including a signature
---------------------
The expression include module-type in a signature performs textual inclusion
of the components of the signature denoted by module-type. It behaves as if the
components of the included signature were copied at the location of the
include. The module-type argument must refer to a module type that is a
signature, not a functor type.
6.10.3 Functor types
=====================
The module type expression functor ( module-name : module-type_1 ) ->
module-type_2 is the type of functors (functions from modules to modules) that
take as argument a module of type module-type_1 and return as result a module
of type module-type_2. The module type module-type_2 can use the name
module-name to refer to type components of the actual argument of the functor.
No restrictions are placed on the type of the functor argument; in particular,
a functor may take another functor as argument ("higher-order" functor).
6.10.4 The with operator
=========================
Assuming module-type denotes a signature, the expression module-type with
mod-constraint { and mod-constraint } denotes the same signature where type
equations have been added to some of the type specifications, as described by
the constraints following the with keyword. The constraint type
[type-parameters] typeconstr = typexpr adds the type equation = typexpr to
the specification of the type component named typeconstr of the constrained
signature. The constraint module module-path = extended-module-path adds type
equations to all type components of the sub-structure denoted by module-path,
making them equivalent to the corresponding type components of the structure
denoted by extended-module-path.
For instance, if the module type name S is bound to the signature
<< sig type t module M: (sig type u end) end
>>
then S with type t=int denotes the signature
<< sig type t=int module M: (sig type u end) end
>>
and S with module M = N denotes the signature
<< sig type t module M: (sig type u=N.u end) end
>>
A functor taking two arguments of type S that share their t component is
written
<< functor (A: S) (B: S with type t = A.t) ...
>>
Constraints are added left to right. After each constraint has been applied,
the resulting signature must be a subtype of the signature before the
constraint was applied. Thus, the with operator can only add information on the
type components of a signature, but never remove information.
6.11 Module expressions (module implementations)
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Module expressions are the module-level equivalent of value expressions: they
evaluate to modules, thus providing implementations for the specifications
expressed in module types.
module-expr ::= module-path
| struct { definition [;;] } end
| functor ( module-name : module-type ) -> module-expr
| module-expr ( module-expr )
| ( module-expr )
| ( module-expr : module-type )
definition ::= let [rec] let-binding { and let-binding }
| external value-name : typexpr = external-declaration
| type-definition
| exception-definition
| class-definition
| classtype-definition
| module module-name { ( module-name : module-type ) } [ :
module-type ] = module-expr
| module type modtype-name = module-type
| open module-path
| include module-expr
6.11.1 Simple module expressions
=================================
The expression module-path evaluates to the module bound to the name
module-path.
The expression ( module-expr ) evaluates to the same module as module-expr.
The expression ( module-expr : module-type ) checks that the type of
module-expr is a subtype of module-type, that is, that all components specified
in module-type are implemented in module-expr, and their implementation meets
the requirements given in module-type. In other terms, it checks that the
implementation module-expr meets the type specification module-type. The whole
expression evaluates to the same module as module-expr, except that all
components not specified in module-type are hidden and can no longer be
accessed.
6.11.2 Structures
==================
Structures struct ... end are collections of definitions for value names,
type names, exceptions, module names and module type names. The definitions are
evaluated in the order in which they appear in the structure. The scope of the
bindings performed by the definitions extend to the end of the structure. As a
consequence, a definition may refer to names bound by earlier definitions in
the same structure.
For compatibility with toplevel phrases (chapter 9) and with Caml Light, an
optional ;; is allowed after each definition in a structure. The ;; has no
semantic meaning. Also for compatibility, ;; expr is allowed as a component of
a structure, meaning let _ = expr, i.e. evaluate expr for its side-effects.
Value definitions
-----------------
A value definition let [rec] let-binding { and let-binding } bind value
names in the same way as a let ... in ... expression (see section 6.7.1). The
value names appearing in the left-hand sides of the bindings are bound to the
corresponding values in the right-hand sides.
A value definition external value-name : typexpr = external-declaration
implements value-name as the external function specified in
external-declaration (see chapter 18).
Type definitions
----------------
A definition of one or several type components is written type typedef { and
typedef } and consists of a sequence of mutually recursive definitions of type
names.
Exception definitions
---------------------
Exceptions are defined with the syntax exception constr-decl or exception
constr-name = constr.
Class definitions
-----------------
A definition of one or several classes is written class class-binding { and
class-binding } and consists of a sequence of mutually recursive definitions of
class names. Class definitions are described more precisely in section 6.9.3.
Class type definitions
----------------------
A definition of one or several classes is written class type classtype-def {
and classtype-def } and consists of a sequence of mutually recursive
definitions of class type names. Class type definitions are described more
precisely in section 6.9.5.
Module definitions
------------------
The basic form for defining a module component is module module-name =
module-expr, which evaluates module-expr and binds the result to the name
module-name.
One can write
module module-name : module-type = module-expr
instead of
module module-name = ( module-expr : module-type ).
Another derived form is
module module-name ( name_1 : module-type_1 ) ... ( name_n :
module-type_n ) = module-expr
which is equivalent to
module module-name = functor ( name_1 : module-type_1 ) -> ... ->
module-expr
Module type definitions
-----------------------
A definition for a module type is written module type modtype-name =
module-type. It binds the name modtype-name to the module type denoted by the
expression module-type.
Opening a module path
---------------------
The expression open module-path in a structure does not define any components
nor perform any bindings. It simply affects the parsing of the following items
of the structure, allowing components of the module denoted by module-path to
be referred to by their simple names name instead of path accesses module-path
. name. The scope of the open stops at the end of the structure expression.
Including the components of another structure
---------------------------------------------
The expression include module-expr in a structure re-exports in the current
structure all definitions of the structure denoted by module-expr. For
instance, if the identifier S is bound to the module
<< struct type t = int let x = 2 end
>>
the module expression
<< struct include S let y = (x + 1 : t) end
>>
is equivalent to the module expression
<< struct type t = int let x = 2 let y = (x + 1 : t) end
>>
The difference between open and include is that open simply provides short
names for the components of the opened structure, without defining any
components of the current structure, while include also adds definitions for
the components of the included structure.
6.11.3 Functors
================
Functor definition
------------------
The expression functor ( module-name : module-type ) -> module-expr
evaluates to a functor that takes as argument modules of the type
module-type_1, binds module-name to these modules, evaluates module-expr in the
extended environment, and returns the resulting modules as results. No
restrictions are placed on the type of the functor argument; in particular, a
functor may take another functor as argument ("higher-order" functor).
Functor application
-------------------
The expression module-expr_1 ( module-expr_2 ) evaluates module-expr_1 to a
functor and module-expr_2 to a module, and applies the former to the latter.
The type of module-expr_2 must match the type expected for the arguments of the
functor module-expr_1.
6.12 Compilation units
*=*=*=*=*=*=*=*=*=*=*=*
unit-interface ::= { specification [;;] }
unit-implementation ::= { definition [;;] }
Compilation units bridge the module system and the separate compilation
system. A compilation unit is composed of two parts: an interface and an
implementation. The interface contains a sequence of specifications, just as
the inside of a sig ... end signature expression. The implementation contains a
sequence of definitions, just as the inside of a struct ... end module
expression. A compilation unit also has a name unit-name, derived from the
names of the files containing the interface and the implementation (see chapter
8 for more details). A compilation unit behaves roughly as the module
definition
module unit-name : sig unit-interface end = struct unit-implementation end
A compilation unit can refer to other compilation units by their names, as if
they were regular modules. For instance, if U is a compilation unit that
defines a type t, other compilation units can refer to that type under the name
U.t; they can also refer to U as a whole structure. Except for names of other
compilation units, a unit interface or unit implementation must not have any
other free variables. In other terms, the type-checking and compilation of an
interface or implementation proceeds in the initial environment
name_1 : sig specification_1 end ... name_n : sig specification_n end
where name_1 ... name_n are the names of the other compilation units
available in the search path (see chapter 8 for more details) and
specification_1 ... specification_n are their respective interfaces.
Chapter 7 Language extensions
********************************
This chapter describes language extensions and convenience features that are
implemented in Objective Caml, but not described in the Objective Caml
reference manual.
7.1 Integer literals for types int32, int64 and nativeint
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
int32-literal ::= integer-literal l
int64-literal ::= integer-literal L
nativeint-literal ::= integer-literal n
An integer literal can be followed by one of the letters l, L or n to
indicate that this integer has type int32, int64 or nativeint respectively,
instead of the default type int for integer literals. The library modules
Int32[], Int64[] and Nativeint[] provide operations on these integer types.
7.2 Streams and stream parsers
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The syntax for streams and stream parsers is no longer part of the Objective
Caml language, but available through a Camlp4 syntax extension. See the Camlp4
reference manual for more information. Support for basic operations on streams
is still available through the Stream[] module of the standard library.
Objective Caml programs that use the stream parser syntax should be compiled
with the -pp camlp4o option to ocamlc and ocamlopt. For interactive use, run
ocaml and issue the `#load "camlp4o.cma";;' command.
7.3 Recursive definitions of values
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
As mentioned in section 6.7.1, the let rec binding construct, in addition to
the definition of recursive functions, also supports a certain class of
recursive definitions of non-functional values, such as
let rec name_1 = 1 :: name_2 and name_2 = 2 :: name_1 in expr
which binds name_1 to the cyclic list 1::2::1::2::..., and name_2 to the
cyclic list 2::1::2::1::...Informally, the class of accepted definitions
consists of those definitions where the defined names occur only inside
function bodies or as argument to a data constructor.
More precisely, consider the expression:
let rec name_1 = expr_1 and ... and name_n = expr_n in expr
It will be accepted if each one of expr_1 ... expr_n is statically
constructive with respect to name_1 ... name_n and not immediately linked to
any of name_1 ... name_n
An expression e is said to be statically constructive with respect to the
variables name_1 ... name_n if at least one of the following conditions is
true:
- e has no free occurrence of any of name_1 ... name_n
- e is a variable
- e has the form fun ... -> ...
- e has the form function ... -> ...
- e has the form lazy ( ... )
- e has one of the following forms, where each one of expr_1 ... expr_m is
statically constructive with respect to name_1 ... name_n, and expr_0 is
statically constructive with respect to name_1 ... name_n, xname_1 ...
xname_m:
- let [rec] xname_1 = expr_1 and ... and xname_m = expr_m in expr_0
- let module ... in expr_1
- constr ( expr_1, ... , expr_m)
- `tag-name ( expr_1, ... , expr_m)
- [| expr_1; ... ; expr_m |]
- { field_1 = expr_1; ... ; field_m = expr_m }
- { expr_1 with field_2 = expr_2; ... ; field_m = expr_m } where expr_1
is not immediately linked to name_1 ... name_n
- ( expr_1, ... , expr_m )
- expr_1; ... ; expr_m
An expression e is said to be immediately linked to the variable name in the
following cases:
- e is name
- e has the form expr_1; ... ; expr_m where expr_m is immediately linked to
name
- e has the form let [rec] xname_1 = expr_1 and ... and xname_m = expr_m in
expr_0 where expr_0 is immediately linked to name or to one of the xname_i
such that expr_i is immediately linked to name.
7.4 Range patterns
*=*=*=*=*=*=*=*=*=*
In patterns, Objective Caml recognizes the form ' c ' .. ' d ' (two character
literals separated by ..) as shorthand for the pattern
' c ' | ' c_1 ' | ' c_2 ' | ... | ' c_n ' | ' d '
where c_1, c_2, ..., c_n are the characters that occur between c and d in
the ASCII character set. For instance, the pattern '0'..'9' matches all
characters that are digits.
7.5 Assertion checking
*=*=*=*=*=*=*=*=*=*=*=*
Objective Caml supports the assert construct to check debugging assertions.
The expression assert expr evaluates the expression expr and returns () if expr
evaluates to true. Otherwise, the exception Assert_failure is raised with the
source file name and the location of expr as arguments. Assertion checking can
be turned off with the -noassert compiler option.
As a special case, assert false is reduced to raise (Assert_failure ...),
which is polymorphic (and is not turned off by the -noassert option).
7.6 Lazy evaluation
*=*=*=*=*=*=*=*=*=*=
The expression lazy expr returns a value v of type Lazy.t that encapsulates
the computation of expr. The argument expr is not evaluated at this point in
the program. Instead, its evaluation will be performed the first time
Lazy.force is applied to the value v, returning the actual value of expr.
Subsequent applications of Lazy.force to v do not evaluate expr again. For more
information, see the description of module Lazy in the standard library (see
section 20.15).
7.7 Local modules
*=*=*=*=*=*=*=*=*=
The expression let module module-name = module-expr in expr locally binds
the module expression module-expr to the identifier module-name during the
evaluation of the expression expr. It then returns the value of expr. For
example:
<< let remove_duplicates comparison_fun string_list =
let module StringSet =
Set.Make(struct type t = string
let compare = comparison_fun end) in
StringSet.elements
(List.fold_right StringSet.add string_list StringSet.empty)
>>
7.8 Private types
*=*=*=*=*=*=*=*=*=
type-representation ::= ...
| = private constr-decl { | constr-decl }
| = private { field-decl { ; field-decl } }
Private types are variant or record types. Values of these types can be
de-structured normally in pattern-matching or via the expr . field notation
for record accesses. However, values of these types cannot be constructed
directly by constructor application or record construction. Moreover,
assignment on a mutable field of a private record type is not allowed.
The typical use of private types is in the export signature of a module, to
ensure that construction of values of the private type always go through the
functions provided by the module, while still allowing pattern-matching outside
the defining module. For example:
<< module M : sig
type t = private A | B of int
val a : t
val b : int -> t
end
= struct
type t = A | B of int
let a = A
let b n = assert (n > 0); B n
end
>>
Here, the private declaration ensures that in any value of type M.t, the
argument to the B constructor is always a positive integer.
With respect to the variance of their parameters, private types are handled
like abstract types. That is, if a private type has parameters, their variance
is the one explicitly given by prefixing the parameter by a `+' or a `-', it is
invariant otherwise.
7.9 Recursive modules
*=*=*=*=*=*=*=*=*=*=*=
definition ::= ...
| module rec module-name : module-type = module-expr {
and module-name: module-type = module-expr }
specification ::= ...
| module rec module-name : module-type { and module-name:
module-type }
Recursive module definitions, introduced by the 'module rec' ...'and' ...
construction, generalize regular module definitions module module-name =
module-expr and module specifications module module-name : module-type by
allowing the defining module-expr and the module-type to refer recursively to
the module identifiers being defined. A typical example of a recursive module
definition is:
<< module rec A : sig
type t = Leaf of string | Node of ASet.t
val compare: t -> t -> int
end
= struct
type t = Leaf of string | Node of ASet.t
let compare t1 t2 =
match (t1, t2) with
(Leaf s1, Leaf s2) -> Pervasives.compare s1 s2
| (Leaf _, Node _) -> 1
| (Node _, Leaf _) -> -1
| (Node n1, Node n2) -> ASet.compare n1 n2
end
and ASet : Set.S with type elt = A.t
= Set.Make(A)
>>
It can be given the following specification:
<< module rec A : sig
type t = Leaf of string | Node of ASet.t
val compare: t -> t -> int
end
and ASet : Set.S with type elt = A.t
>>
This is an experimental extension of Objective Caml: the class of recursive
definitions accepted, as well as its dynamic semantics are not final and
subject to change in future releases.
Currently, the compiler requires that all dependency cycles between the
recursively-defined module identifiers go through at least one "safe" module. A
module is "safe" if all value definitions that it contains have function types
typexpr_1 -> typexpr_2. Evaluation of a recursive module definition proceeds
by building initial values for the safe modules involved, binding all
(functional) values to fun _ -> raise Undefined_recursive_module. The defining
module expressions are then evaluated, and the initial values for the safe
modules are replaced by the values thus computed. If a function component of a
safe module is applied during this computation (which corresponds to an
ill-founded recursive definition), the Undefined_recursive_module exception is
raised.
7.10 Private row types
*=*=*=*=*=*=*=*=*=*=*=*
type-equation ::= ...
| = private typexpr
Private row types are type abbreviations where part of the structure of the
type is left abstract. Concretely typexpr in the above should denote either an
object type or a polymorphic variant type, with some possibility of refinement
left. If the private declaration is used in an interface, the corresponding
implementation may either provide a ground instance, or a refined private type.
<< module M : sig type c = private < x : int; .. > val o : c end =
struct
class c = object method x = 3 method y = 2 end
let o = new c
end
>>
This declaration does more than hiding the y method, it also makes the type c
incompatible with any other closed object type, meaning that only o will be of
type c. In that respect it behaves similarly to private record types. But
private row types are more flexible with respect to incremental refinement.
This feature can be used in combination with functors.
<< module F(X : sig type c = private < x : int; .. > end) =
struct
let get_x (o : X.c) = o#x
end
module G(X : sig type c = private < x : int; y : int; .. > end) =
struct
include F(X)
let get_y (o : X.c) = o#y
end
>>
Polymorphic variant types can be refined in two ways, either to allow the
addition of new constructors, or to allow the disparition of declared
constructors. The second case corresponds to private variant types (one cannot
create a value of the private type), while the first case requires default
cases in pattern-matching to handle addition.
<< type t = [ `A of int | `B of bool ]
type u = private [< t > `A ]
type v = private [> t ]
>>
With type u, it is possible to create values of the form (`A n), but not (`B
b). With type v, construction is not restricted but pattern-matching must have
a default case.
Like for abstract and private types, the variance of type parameters is not
infered, and must be given explicitly.
Part: III
*********
The Objective Caml tools
************************
Chapter 8 Batch compilation (ocamlc)
***************************************
This chapter describes the Objective Caml batch compiler ocamlc, which
compiles Caml source files to bytecode object files and link these object files
to produce standalone bytecode executable files. These executable files are
then run by the bytecode interpreter ocamlrun.
8.1 Overview of the compiler
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The ocamlc command has a command-line interface similar to the one of most C
compilers. It accepts several types of arguments and processes them
sequentially:
- Arguments ending in .mli are taken to be source files for compilation unit
interfaces. Interfaces specify the names exported by compilation units: they
declare value names with their types, define public data types, declare
abstract data types, and so on. From the file x.mli, the ocamlc compiler
produces a compiled interface in the file x.cmi.
- Arguments ending in .ml are taken to be source files for compilation unit
implementations. Implementations provide definitions for the names exported
by the unit, and also contain expressions to be evaluated for their
side-effects. From the file x.ml, the ocamlc compiler produces compiled
object bytecode in the file x.cmo.
If the interface file x.mli exists, the implementation x.ml is checked against
the corresponding compiled interface x.cmi, which is assumed to exist. If no
interface x.mli is provided, the compilation of x.ml produces a compiled
interface file x.cmi in addition to the compiled object code file x.cmo. The
file x.cmi produced corresponds to an interface that exports everything that
is defined in the implementation x.ml.
- Arguments ending in .cmo are taken to be compiled object bytecode. These
files are linked together, along with the object files obtained by compiling
.ml arguments (if any), and the Objective Caml standard library, to produce
a standalone executable program. The order in which .cmo and .ml arguments
are presented on the command line is relevant: compilation units are
initialized in that order at run-time, and it is a link-time error to use a
component of a unit before having initialized it. Hence, a given x.cmo file
must come before all .cmo files that refer to the unit x.
- Arguments ending in .cma are taken to be libraries of object bytecode. A
library of object bytecode packs in a single file a set of object bytecode
files (.cmo files). Libraries are built with ocamlc -a (see the description
of the -a option below). The object files contained in the library are
linked as regular .cmo files (see above), in the order specified when the
.cma file was built. The only difference is that if an object file contained
in a library is not referenced anywhere in the program, then it is not
linked in.
- Arguments ending in .c are passed to the C compiler, which generates a .o
object file. This object file is linked with the program if the -custom flag
is set (see the description of -custom below).
- Arguments ending in .o or .a (.obj or .lib under Windows) are assumed to be
C object files and libraries. They are passed to the C linker when linking
in -custom mode (see the description of -custom below).
- Arguments ending in .so (.dll under Windows) are assumed to be C shared
libraries (DLLs). During linking, they are searched for external C functions
referenced from the Caml code, and their names are written in the generated
bytecode executable. The run-time system ocamlrun then loads them
dynamically at program start-up time.
The output of the linking phase is a file containing compiled bytecode that
can be executed by the Objective Caml bytecode interpreter: the command named
ocamlrun. If caml.out is the name of the file produced by the linking phase,
the command
<<
ocamlrun caml.out arg_1 arg_2 ... arg_n
>>
executes the compiled code contained in caml.out, passing it as arguments
the character strings arg_1 to arg_n. (See chapter 10 for more details.)
On most systems, the file produced by the linking phase can be run directly,
as in:
<<
./caml.out arg_1 arg_2 ... arg_n
>>
The produced file has the executable bit set, and it manages to launch the
bytecode interpreter by itself.
8.2 Options
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The following command-line options are recognized by ocamlc.
-a Build a library (.cma file) with the object files (.cmo files) given on
the command line, instead of linking them into an executable file. The name
of the library must be set with the -o option.
If -custom, -cclib or -ccopt options are passed on the command line, these
options are stored in the resulting .cma library. Then, linking with this
library automatically adds back the -custom, -cclib and -ccopt options as if
they had been provided on the command line, unless the -noautolink option is
given.
-c Compile only. Suppress the linking phase of the compilation. Source code
files are turned into compiled files, but no executable file is produced.
This option is useful to compile modules separately.
-cc ccomp Use ccomp as the C linker called by ocamlc -custom and as the C
compiler for compiling .c source files.
-cclib -llibname Pass the -llibname option to the C linker when linking in
"custom runtime" mode (see the -custom option). This causes the given C
library to be linked with the program.
-ccopt option Pass the given option to the C compiler and linker, when
linking in "custom runtime" mode (see the -custom option). For instance,
-ccopt -Ldir causes the C linker to search for C libraries in directory dir.
-custom Link in "custom runtime" mode. In the default linking mode, the
linker produces bytecode that is intended to be executed with the shared
runtime system, ocamlrun. In the custom runtime mode, the linker produces an
output file that contains both the runtime system and the bytecode for the
program. The resulting file is larger, but it can be executed directly, even
if the ocamlrun command is not installed. Moreover, the "custom runtime"
mode enables static linking of Caml code with user-defined C functions, as
described in chapter 18. Unix:
Never use the strip command on executables produced by ocamlc -custom.
This would remove the bytecode part of the executable.
-dllib -llibname Arrange for the C shared library dlllibname.so
(dlllibname.dll under Windows) to be loaded dynamically by the run-time
system ocamlrun at program start-up time.
-dllpath dir Adds the directory dir to the run-time search path for shared C
libraries. At link-time, shared libraries are searched in the standard
search path (the one corresponding to the -I option). The -dllpath option
simply stores dir in the produced executable file, where ocamlrun can find
it and exploit it as described in section 10.3.
-dtypes Dump detailed type information. The information for file x.ml is put
into file x.annot. In case of a type error, dump all the information
inferred by the type-checker before the error. The x.annot file can be used
with the emacs commands given in emacs/caml-types.el to display types
interactively.
-g Add debugging information while compiling and linking. This option is
required in order to be able to debug the program with ocamldebug (see
chapter 16), and to produce stack backtraces when the program terminates on
an uncaught exception (see section 10.2).
-i Cause the compiler to print all defined names (with their inferred types
or their definitions) when compiling an implementation (.ml file). No
compiled files (.cmo and .cmi files) are produced. This can be useful to
check the types inferred by the compiler. Also, since the output follows the
syntax of interfaces, it can help in writing an explicit interface (.mli
file) for a file: just redirect the standard output of the compiler to a
.mli file, and edit that file to remove all declarations of unexported
names.
-I directory Add the given directory to the list of directories searched for
compiled interface files (.cmi), compiled object code files (.cmo),
libraries (.cma), and C libraries specified with -cclib -lxxx. By default,
the current directory is searched first, then the standard library
directory. Directories added with -I are searched after the current
directory, in the order in which they were given on the command line, but
before the standard library directory.
If the given directory starts with +, it is taken relative to the standard
library directory. For instance, -I +labltk adds the subdirectory labltk of
the standard library to the search path.
-impl filename Compile the file filename as an implementation file, even if
its extension is not .ml.
-intf filename Compile the file filename as an interface file, even if its
extension is not .mli.
-linkall Force all modules contained in libraries to be linked in. If this
flag is not given, unreferenced modules are not linked in. When building a
library (-a flag), setting the -linkall flag forces all subsequent links of
programs involving that library to link all the modules contained in the
library.
-make-runtime Build a custom runtime system (in the file specified by option
-o) incorporating the C object files and libraries given on the command
line. This custom runtime system can be used later to execute bytecode
executables produced with the ocamlc -use-runtime runtime-name option. See
section 18.1.6 for more information.
-noassert Turn assertion checking off: assertions are not compiled. This flag
has no effect when linking already compiled files.
-noautolink When linking .cma libraries, ignore -custom, -cclib and -ccopt
options potentially contained in the libraries (if these options were given
when building the libraries). This can be useful if a library contains
incorrect specifications of C libraries or C options; in this case, during
linking, set -noautolink and pass the correct C libraries and options on the
command line.
-nolabels Ignore non-optional labels in types. Labels cannot be used in
applications, and parameter order becomes strict.
-o exec-file Specify the name of the output file produced by the linker. The
default output name is a.out under Unix and camlprog.exe under Windows. If
the -a option is given, specify the name of the library produced. If the
-pack option is given, specify the name of the packed object file produced.
If the -output-obj option is given, specify the name of the output file
produced.
-output-obj Cause the linker to produce a C object file instead of a bytecode
executable file. This is useful to wrap Caml code as a C library, callable
from any C program. See chapter 18, section 18.7.5. The name of the output
object file is camlprog.o by default; it can be set with the -o option.
-pack Build a bytecode object file (.cmo file) and its associated compiled
interface (.cmi) that combines the object files given on the command line,
making them appear as sub-modules of the output .cmo file. The name of the
output .cmo file must be given with the -o option. For instance,
<< ocamlc -pack -o p.cmo a.cmo b.cmo c.cmo
>>
generates compiled files p.cmo and p.cmi describing a compilation unit having
three sub-modules A, B and C, corresponding to the contents of the object
files a.cmo, b.cmo and c.cmo. These contents can be referenced as P.A, P.B
and P.C in the remainder of the program.
-pp command Cause the compiler to call the given command as a preprocessor
for each source file. The output of command is redirected to an intermediate
file, which is compiled. If there are no compilation errors, the
intermediate file is deleted afterwards. The name of this file is built from
the basename of the source file with the extension .ppi for an interface
(.mli) file and .ppo for an implementation (.ml) file.
-principal Check information path during type-checking, to make sure that all
types are derived in a principal way. When using labelled arguments and/or
polymorphic methods, this flag is required to ensure future versions of the
compiler will be able to infer types correctly, even if internal algorithms
change. All programs accepted in -principal mode are also accepted in
default mode with equivalent types, but different binary signatures, and
this may slow down type checking; yet this is a good idea to use it once
before publishing source code.
-rectypes Allow arbitrary recursive types during type-checking. By default,
only recursive types where the recursion goes through an object type are
supported. Note that once you have created an interface using this flag, you
must use it again for all dependencies.
-thread Compile or link multithreaded programs, in combination with the
system threads library described in chapter 24.
-unsafe Turn bound checking off on array and string accesses (the v.(i) and
s.[i] constructs). Programs compiled with -unsafe are therefore slightly
faster, but unsafe: anything can happen if the program accesses an array or
string outside of its bounds.
-use-runtime runtime-name Generate a bytecode executable file that can be
executed on the custom runtime system runtime-name, built earlier with
ocamlc -make-runtime runtime-name. See section 18.1.6 for more information.
-v Print the version number of the compiler and the location of the standard
library directory, then exit.
-verbose Print all external commands before they are executed, in particular
invocations of the C compiler and linker in -custom mode. Useful to debug C
library problems.
-version Print the version number of the compiler in short form (e.g. 3.06),
then exit.
-vmthread Compile or link multithreaded programs, in combination with the
VM-level threads library described in chapter 24.
-w warning-list Enable or disable warnings according to the argument
warning-list. The argument is a string of one or several characters, with
the following meaning for each character:
A/a enable/disable all warnings.
C/c enable/disable warnings for suspicious comments.
D/d enable/disable warnings for deprecated features.
E/e enable/disable warnings for fragile pattern matchings (matchings that
would remain complete if additional constructors are added to a variant
type involved).
F/f enable/disable warnings for partially applied functions (i.e. f x;
expr where the application f x has a function type).
L/l enable/disable warnings for labels omitted in application.
M/m enable/disable warnings for overriden methods.
P/p enable/disable warnings for partial matches (missing cases in pattern
matchings).
S/s enable/disable warnings for statements that do not have type unit
(e.g. expr1; expr2 when expr1 does not have type unit), and that are not
functions (covered by warning F).
U/u enable/disable warnings for unused (redundant) match cases.
V/v enable/disable warnings for hidden instance variables.
Y/y enable/disable warnings for unused variables bound with the let or as
keywords and that don't start with an underscore.
Z/z enable/disable warnings for all other unused variables that don't
start with an underscore.
X/x enable/disable warnings that don't fit in the above categories.
The default setting is -w Aelz (all warnings enabled except fragile
matchings, omitted labels, non-suspicious unused variables). Warnings F and
S rely on the type system, thus they are not triggered when the type of the
statement is unknown.
-warn-error warning-list Turn the warnings indicated in the argument
warning-list into errors. The compiler will stop with an error when one of
these warnings is emitted. The warning-list is a string of one or several
characters, with the same meaning as for the -w option: an uppercase
character turns the corresponding warning into an error, a lowercase
character leaves it as a warning. The default setting is -warn-error a (none
of the warnings is treated as an error).
-where Print the location of the standard library, then exit.
8.3 Modules and the file system
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This short section is intended to clarify the relationship between the names
of the modules corresponding to compilation units and the names of the files
that contain their compiled interface and compiled implementation.
The compiler always derives the module name by taking the capitalized base
name of the source file (.ml or .mli file). That is, it strips the leading
directory name, if any, as well as the .ml or .mli suffix; then, it set the
first letter to uppercase, in order to comply with the requirement that module
names must be capitalized. For instance, compiling the file mylib/misc.ml
provides an implementation for the module named Misc. Other compilation units
may refer to components defined in mylib/misc.ml under the names Misc.name;
they can also do open Misc, then use unqualified names name.
The .cmi and .cmo files produced by the compiler have the same base name as
the source file. Hence, the compiled files always have their base name equal
(modulo capitalization of the first letter) to the name of the module they
describe (for .cmi files) or implement (for .cmo files).
When the compiler encounters a reference to a free module identifier Mod, it
looks in the search path for a file named Mod.cmi or mod.cmi and loads the
compiled interface contained in that file. As a consequence, renaming .cmi
files is not advised: the name of a .cmi file must always correspond to the
name of the compilation unit it implements. It is admissible to move them to
another directory, if their base name is preserved, and the correct -I options
are given to the compiler. The compiler will flag an error if it loads a .cmi
file that has been renamed.
Compiled bytecode files (.cmo files), on the other hand, can be freely
renamed once created. That's because the linker never attempts to find by
itself the .cmo file that implements a module with a given name: it relies
instead on the user providing the list of .cmo files by hand.
8.4 Common errors
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This section describes and explains the most frequently encountered error
messages.
Cannot find file filename The named file could not be found in the current
directory, nor in the directories of the search path. The filename is either
a compiled interface file (.cmi file), or a compiled bytecode file (.cmo
file). If filename has the format mod.cmi, this means you are trying to
compile a file that references identifiers from module mod, but you have not
yet compiled an interface for module mod. Fix: compile mod.mli or mod.ml
first, to create the compiled interface mod.cmi.
If filename has the format mod.cmo, this means you are trying to link a
bytecode object file that does not exist yet. Fix: compile mod.ml first.
If your program spans several directories, this error can also appear because
you haven't specified the directories to look into. Fix: add the correct -I
options to the command line.
Corrupted compiled interface filename The compiler produces this error when
it tries to read a compiled interface file (.cmi file) that has the wrong
structure. This means something went wrong when this .cmi file was written:
the disk was full, the compiler was interrupted in the middle of the file
creation, and so on. This error can also appear if a .cmi file is modified
after its creation by the compiler. Fix: remove the corrupted .cmi file, and
rebuild it.
This expression has type t_1, but is used with type t_2 This is by far the
most common type error in programs. Type t_1 is the type inferred for the
expression (the part of the program that is displayed in the error message),
by looking at the expression itself. Type t_2 is the type expected by the
context of the expression; it is deduced by looking at how the value of this
expression is used in the rest of the program. If the two types t_1 and t_2
are not compatible, then the error above is produced.
In some cases, it is hard to understand why the two types t_1 and t_2 are
incompatible. For instance, the compiler can report that "expression of type
foo cannot be used with type foo", and it really seems that the two types
foo are compatible. This is not always true. Two type constructors can have
the same name, but actually represent different types. This can happen if a
type constructor is redefined. Example:
<< type foo = A | B
let f = function A -> 0 | B -> 1
type foo = C | D
f C
>>
This result in the error message "expression C of type foo cannot be used with
type foo".
The type of this expression, t, contains type variables that cannot be
generalized Type variables ('a, 'b, ...) in a type t can be in either of
two states: generalized (which means that the type t is valid for all
possible instantiations of the variables) and not generalized (which means
that the type t is valid only for one instantiation of the variables). In a
let binding let name = expr, the type-checker normally generalizes as many
type variables as possible in the type of expr. However, this leads to
unsoundness (a well-typed program can crash) in conjunction with polymorphic
mutable data structures. To avoid this, generalization is performed at let
bindings only if the bound expression expr belongs to the class of
"syntactic values", which includes constants, identifiers, functions, tuples
of syntactic values, etc. In all other cases (for instance, expr is a
function application), a polymorphic mutable could have been created and
generalization is therefore turned off for all variables occuring in
contravariant or non-variant branches of the type. For instance, if the type
of a non-value is 'a list the variable is generalizable (list is a covariant
type constructor), but not in 'a list -> 'a list (the left branch of -> is
contravariant) or 'a ref (ref is non-variant).
Non-generalized type variables in a type cause no difficulties inside a given
structure or compilation unit (the contents of a .ml file, or an interactive
session), but they cannot be allowed inside signatures nor in compiled
interfaces (.cmi file), because they could be used inconsistently later.
Therefore, the compiler flags an error when a structure or compilation unit
defines a value name whose type contains non-generalized type variables.
There are two ways to fix this error:
- Add a type constraint or a .mli file to give a monomorphic type (without
type variables) to name. For instance, instead of writing
<< let sort_int_list = Sort.list (<)
(* inferred type 'a list -> 'a list, with 'a not generalized *)
>>
write
<< let sort_int_list = (Sort.list (<) : int list -> int list);;
>>
- If you really need name to have a polymorphic type, turn its defining
expression into a function by adding an extra parameter. For instance,
instead of writing
<< let map_length = List.map Array.length
(* inferred type 'a array list -> int list, with 'a not generalized
*)
>>
write
<< let map_length lv = List.map Array.length lv
>>
Reference to undefined global mod This error appears when trying to link an
incomplete or incorrectly ordered set of files. Either you have forgotten to
provide an implementation for the compilation unit named mod on the command
line (typically, the file named mod.cmo, or a library containing that file).
Fix: add the missing .ml or .cmo file to the command line. Or, you have
provided an implementation for the module named mod, but it comes too late
on the command line: the implementation of mod must come before all bytecode
object files that reference mod. Fix: change the order of .ml and .cmo files
on the command line.
Of course, you will always encounter this error if you have mutually recursive
functions across modules. That is, function Mod1.f calls function Mod2.g,
and function Mod2.g calls function Mod1.f. In this case, no matter what
permutations you perform on the command line, the program will be rejected
at link-time. Fixes:
- Put f and g in the same module.
- Parameterize one function by the other. That is, instead of having
<<mod1.ml: let f x = ... Mod2.g ...
mod2.ml: let g y = ... Mod1.f ...
>>
define
<<mod1.ml: let f g x = ... g ...
mod2.ml: let rec g y = ... Mod1.f g ...
>>
and link mod1.cmo before mod2.cmo.
- Use a reference to hold one of the two functions, as in :
<<mod1.ml: let forward_g =
ref((fun x -> failwith "forward_g") : <type>)
let f x = ... !forward_g ...
mod2.ml: let g y = ... Mod1.f ...
let _ = Mod1.forward_g := g
>>
The external function f is not available This error appears when trying to
link code that calls external functions written in C. As explained in
chapter 18, such code must be linked with C libraries that implement the
required f C function. If the C libraries in question are not shared
libraries (DLLs), the code must be linked in "custom runtime" mode. Fix: add
the required C libraries to the command line, and possibly the -custom
option.
Chapter 9 The toplevel system (ocaml)
****************************************
This chapter describes the toplevel system for Objective Caml, that permits
interactive use of the Objective Caml system through a read-eval-print loop. In
this mode, the system repeatedly reads Caml phrases from the input, then
typechecks, compile and evaluate them, then prints the inferred type and result
value, if any. The system prints a # (sharp) prompt before reading each phrase.
Input to the toplevel can span several lines. It is terminated by ;; (a
double-semicolon). The toplevel input consists in one or several toplevel
phrases, with the following syntax:
toplevel-input ::= { toplevel-phrase } ;;
toplevel-phrase ::= definition
| expr
| # ident directive-argument
directive-argument ::= epsilon
| string-literal
| integer-literal
| value-path
A phrase can consist of a definition, similar to those found in
implementations of compilation units or in struct ... end module expressions.
The definition can bind value names, type names, an exception, a module name,
or a module type name. The toplevel system performs the bindings, then prints
the types and values (if any) for the names thus defined.
A phrase may also consist in a open directive (see section 6.11), or a value
expression (section 6.7). Expressions are simply evaluated, without performing
any bindings, and the value of the expression is printed.
Finally, a phrase can also consist in a toplevel directive, starting with #
(the sharp sign). These directives control the behavior of the toplevel; they
are listed below in section 9.2.
Unix:
The toplevel system is started by the command ocaml, as follows:
<<
ocaml options objects # interactive mode
ocaml options objects scriptfile # script mode
>>
options are described below. objects are filenames ending in .cmo or .cma;
they are loaded into the interpreter immediately after options are set.
scriptfile is any file name not ending in .cmo or .cma.
If no scriptfile is given on the command line, the toplevel system enters
interactive mode: phrases are read on standard input, results are printed on
standard output, errors on standard error. End-of-file on standard input
terminates ocaml (see also the #quit directive in section 9.2).
On start-up (before the first phrase is read), if the file .ocamlinit exists
in the current directory, its contents are read as a sequence of Objective
Caml phrases and executed as per the #use directive described in section
9.2. The evaluation outcode for each phrase are not displayed. If the
current directory does not contain an .ocamlinit file, but the user's home
directory (environment variable HOME) does, the latter is read and executed
as described below.
The toplevel system does not perform line editing, but it can easily be used
in conjunction with an external line editor such as ledit, ocaml2 or rlwrap
(see the Caml Hump (1)). Another option is to use ocaml under Gnu Emacs,
which gives the full editing power of Emacs (command run-caml from library
inf-caml).
At any point, the parsing, compilation or evaluation of the current phrase
can be interrupted by pressing ctrl-C (or, more precisely, by sending the
INTR signal to the ocaml process). The toplevel then immediately returns to
the # prompt.
If scriptfile is given on the command-line to ocaml, the toplevel system
enters script mode: the contents of the file are read as a sequence of
Objective Caml phrases and executed, as per the #use directive (section
9.2). The outcome of the evaluation is not printed. On reaching the end of
file, the ocaml command exits immediately. No commands are read from
standard input. Sys.argv is transformed, ignoring all Objective Caml
parameters, and starting with the script file name in Sys.argv.(0).
In script mode, the first line of the script is ignored if it starts with
#!. Thus, it should be possible to make the script itself executable and put
as first line #!/usr/local/bin/ocaml, thus calling the toplevel system
automatically when the script is run. However, ocaml itself is a #! script
on most installations of Objective Caml, and Unix kernels usually do not
handle nested #! scripts. A better solution is to put the following as the
first line of the script:
<< #!/usr/local/bin/ocamlrun /usr/local/bin/ocaml
>>
Windows:
In addition to the text-only command ocaml.exe, which works exactly as
under Unix (see above), a graphical user interface for the toplevel is
available under the name ocamlwin.exe. It should be launched from the
Windows file manager or program manager. This interface provides a text
window in which commands can be entered and edited, and the toplevel
responses are printed.
9.1 Options
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The following command-line options are recognized by the ocaml command.
-I directory Add the given directory to the list of directories searched for
source and compiled files. By default, the current directory is searched
first, then the standard library directory. Directories added with -I are
searched after the current directory, in the order in which they were given
on the command line, but before the standard library directory.
If the given directory starts with +, it is taken relative to the standard
library directory. For instance, -I +labltk adds the subdirectory labltk of
the standard library to the search path.
Directories can also be added to the search path once the toplevel is running
with the #directory directive (section 9.2).
-nolabels Ignore non-optional labels in types. Labels cannot be used in
applications, and parameter order becomes strict.
-principal Check information path during type-checking, to make sure that all
types are derived in a principal way. All programs accepted in -principal
mode are also accepted in default mode with equivalent types.
-rectypes Allow arbitrary recursive types during type-checking. By default,
only recursive types where the recursion goes through an object type are
supported.
-unsafe See the corresponding option for ocamlc, chapter 8. Turn bound
checking off on array and string accesses (the v.(i) and s.[i] constructs).
Programs compiled with -unsafe are therefore slightly faster, but unsafe:
anything can happen if the program accesses an array or string outside of
its bounds.
-version Print version and exit.
-w warning-list Enable or disable warnings according to the argument
warning-list.
Unix:
The following environment variables are also consulted:
LC_CTYPE If set to iso_8859_1, accented characters (from the ISO Latin-1
character set) in string and character literals are printed as is;
otherwise, they are printed as decimal escape sequences (\ddd).
TERM When printing error messages, the toplevel system attempts to
underline visually the location of the error. It consults the TERM
variable to determines the type of output terminal and look up its
capabilities in the terminal database.
HOME Directory where the .ocamlinit file is searched.
9.2 Toplevel directives
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The following directives control the toplevel behavior, load files in memory,
and trace program execution.
Note: all directives start with a # (sharp) symbol. This # must be typed
before the directive, and must not be confused with the # prompt displayed by
the interactive loop. For instance, typing #quit;; will exit the toplevel loop,
but typing quit;; will result in an "unbound value quit" error.
#quit;; Exit the toplevel loop and terminate the ocaml command.
#labels bool;; Ignore labels in function types if argument is false, or
switch back to default behaviour (commuting style) if argument is true.
#warnings "warning-list";; Enable or disable warnings according to the
argument.
#directory "dir-name";; Add the given directory to the list of directories
searched for source and compiled files.
#cd "dir-name";; Change the current working directory.
#load "file-name";; Load in memory a bytecode object file (.cmo file)
produced by the batch compiler ocamlc.
#use "file-name";; Read, compile and execute source phrases from the given
file. This is textual inclusion: phrases are processed just as if they were
typed on standard input. The reading of the file stops at the first error
encountered.
#install_printer printer-name;; This directive registers the function named
printer-name (a value path) as a printer for values whose types match the
argument type of the function. That is, the toplevel loop will call
printer-name when it has such a value to print.
The printing function printer-name should have type Format.formatter -> t ->
unit, where t is the type for the values to be printed, and should output
its textual representation for the value of type t on the given formatter,
using the functions provided by the Format library. For backward
compatibility, printer-name can also have type t -> unit and should then
output on the standard formatter, but this usage is deprecated.
#remove_printer printer-name;; Remove the named function from the table of
toplevel printers.
#trace function-name;; After executing this directive, all calls to the
function named function-name will be "traced". That is, the argument and the
result are displayed for each call, as well as the exceptions escaping out
of the function, raised either by the function itself or by another function
it calls. If the function is curried, each argument is printed as it is
passed to the function.
#untrace function-name;; Stop tracing the given function.
#untrace_all;; Stop tracing all functions traced so far.
#print_depth n;; Limit the printing of values to a maximal depth of n. The
parts of values whose depth exceeds n are printed as ... (ellipsis).
#print_length n;; Limit the number of value nodes printed to at most n.
Remaining parts of values are printed as ... (ellipsis).
9.3 The toplevel and the module system
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Toplevel phrases can refer to identifiers defined in compilation units with
the same mechanisms as for separately compiled units: either by using qualified
names (Modulename.localname), or by using the open construct and unqualified
names (see section 6.3).
However, before referencing another compilation unit, an implementation of
that unit must be present in memory. At start-up, the toplevel system contains
implementations for all the modules in the the standard library.
Implementations for user modules can be entered with the #load directive
described above. Referencing a unit for which no implementation has been
provided results in the error "Reference to undefined global `...' ".
Note that entering open Mod merely accesses the compiled interface (.cmi
file) for Mod, but does not load the implementation of Mod, and does not cause
any error if no implementation of Mod has been loaded. The error "reference to
undefined global Mod" will occur only when executing a value or module
definition that refers to Mod.
9.4 Common errors
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This section describes and explains the most frequently encountered error
messages.
Cannot find file filename The named file could not be found in the current
directory, nor in the directories of the search path.
If filename has the format mod.cmi, this means you have referenced the
compilation unit mod, but its compiled interface could not be found. Fix:
compile mod.mli or mod.ml first, to create the compiled interface mod.cmi.
If filename has the format mod.cmo, this means you are trying to load with
#load a bytecode object file that does not exist yet. Fix: compile mod.ml
first.
If your program spans several directories, this error can also appear because
you haven't specified the directories to look into. Fix: use the #directory
directive to add the correct directories to the search path.
This expression has type t_1, but is used with type t_2 See section 8.4.
Reference to undefined global mod You have neglected to load in memory an
implementation for a module with #load. See section 9.3 above.
9.5 Building custom toplevel systems: ocamlmktop
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The ocamlmktop command builds Objective Caml toplevels that contain user code
preloaded at start-up.
The ocamlmktop command takes as argument a set of .cmo and .cma files, and
links them with the object files that implement the Objective Caml toplevel.
The typical use is:
<< ocamlmktop -o mytoplevel foo.cmo bar.cmo gee.cmo
>>
This creates the bytecode file mytoplevel, containing the Objective Caml
toplevel system, plus the code from the three .cmo files. This toplevel is
directly executable and is started by:
<< ./mytoplevel
>>
This enters a regular toplevel loop, except that the code from foo.cmo,
bar.cmo and gee.cmo is already loaded in memory, just as if you had typed:
<< #load "foo.cmo";;
#load "bar.cmo";;
#load "gee.cmo";;
>>
on entrance to the toplevel. The modules Foo, Bar and Gee are not opened,
though; you still have to do
<< open Foo;;
>>
yourself, if this is what you wish.
9.6 Options
*=*=*=*=*=*=
The following command-line options are recognized by ocamlmktop.
-cclib libname Pass the -llibname option to the C linker when linking in
"custom runtime" mode. See the corresponding option for ocamlc, in chapter
8.
-ccopt option Pass the given option to the C compiler and linker, when
linking in "custom runtime" mode. See the corresponding option for ocamlc,
in chapter 8.
-custom Link in "custom runtime" mode. See the corresponding option for
ocamlc, in chapter 8.
-I directory Add the given directory to the list of directories searched for
compiled object code files (.cmo and .cma).
-o exec-file Specify the name of the toplevel file produced by the linker.
The default is a.out.
---------------------------------------
(1) http://caml.inria.fr/humps/index_framed_caml.html
Chapter 10 The runtime system (ocamlrun)
*******************************************
The ocamlrun command executes bytecode files produced by the linking phase of
the ocamlc command.
10.1 Overview
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The ocamlrun command comprises three main parts: the bytecode interpreter,
that actually executes bytecode files; the memory allocator and garbage
collector; and a set of C functions that implement primitive operations such as
input/output.
The usage for ocamlrun is:
<<
ocamlrun options bytecode-executable arg_1 ... arg_n
>>
The first non-option argument is taken to be the name of the file containing
the executable bytecode. (That file is searched in the executable path as well
as in the current directory.) The remaining arguments are passed to the Caml
program, in the string array Sys.argv. Element 0 of this array is the name of
the bytecode executable file; elements 1 to n are the remaining arguments arg_1
to arg_n.
As mentioned in chapter 8, the bytecode executable files produced by the
ocamlc command are self-executable, and manage to launch the ocamlrun command
on themselves automatically. That is, assuming caml.out is a bytecode
executable file,
<<
caml.out arg_1 ... arg_n
>>
works exactly as
<<
ocamlrun caml.out arg_1 ... arg_n
>>
Notice that it is not possible to pass options to ocamlrun when invoking
caml.out directly.
Windows:
Under several versions of Windows, bytecode executable files are
self-executable only if their name ends in .exe. It is recommended to always
give .exe names to bytecode executables, e.g. compile with ocamlc -o
myprog.exe ... rather than ocamlc -o myprog ....
10.2 Options
*=*=*=*=*=*=*
The following command-line options are recognized by ocamlrun.
-b When the program aborts due to an uncaught exception, print a detailed
"back trace" of the execution, showing where the exception was raised and
which function calls were outstanding at this point. The back trace is
printed only if the bytecode executable contains debugging information, i.e.
was compiled and linked with the -g option to ocamlc set. This is equivalent
to setting the b flag in the OCAMLRUNPARAM environment variable (see below).
-I dir Search the directory dir for dynamically-loaded libraries, in addition
to the standard search path (see section 10.3).
-v Direct the memory manager to print some progress messages on standard
error. This is equivalent to setting v=63 in the OCAMLRUNPARAM environment
variable (see below).
-version Print version and exit.
The following environment variables are also consulted:
CAML_LD_LIBRARY_PATH Additional directories to search for dynamically-loaded
libraries (see section 10.3).
OCAMLLIB The directory containing the Objective Caml standard library. (If
OCAMLLIB is not set, CAMLLIB will be used instead.) Used to locate the
ld.conf configuration file for dynamic loading (see section 10.3). If not
set, default to the library directory specified when compiling Objective
Caml.
OCAMLRUNPARAM Set the runtime system options and garbage collection
parameters. (If OCAMLRUNPARAM is not set, CAMLRUNPARAM will be used
instead.) This variable must be a sequence of parameter specifications. A
parameter specification is an option letter followed by an = sign, a decimal
number (or an hexadecimal number prefixed by 0x), and an optional
multiplier. There are nine options, six of which correspond to the fields of
the control record documented in section 20.10.
b (backtrace) Trigger the printing of a stack backtrace when an uncaught
exception aborts the program. This option takes no argument.
p (parser trace) Turn on debugging support for ocamlyacc-generated
parsers. When this option is on, the pushdown automaton that executes the
parsers prints a trace of its actions. This option takes no argument.
s (minor_heap_size) Size of the minor heap. (in words)
i (major_heap_increment) Default size increment for the major heap. (in
words)
o (space_overhead) The major GC speed setting.
O (max_overhead) The heap compaction trigger setting.
v (verbose) What GC messages to print to stderr. This is a sum of values
selected from the following:
1 (= 0x001) Start of major GC cycle.
2 (= 0x002) Minor collection and major GC slice.
4 (= 0x004) Growing and shrinking of the heap.
8 (= 0x008) Resizing of stacks and memory manager tables.
16 (= 0x010) Heap compaction.
32 (= 0x020) Change of GC parameters.
64 (= 0x040) Computation of major GC slice size.
128 (= 0x080) Calling of finalisation functions
256 (= 0x100) Startup messages (loading the bytecode executable file,
resolving shared libraries).
l (stack_limit) The limit (in words) of the stack size.
h The initial size of the major heap (in words).
The multiplier is k, M, or G, for multiplication by 2^10, 2^20, and 2^30
respectively. For example, on a 32-bit machine, under bash the command
<<
export OCAMLRUNPARAM='b,s=256k,v=0x015'
>>
tells a subsequent ocamlrun to print backtraces for uncaught exceptions, set
its initial minor heap size to 1 megabyte and print a message at the start
of each major GC cycle, when the heap size changes, and when compaction is
triggered.
CAMLRUNPARAM If OCAMLRUNPARAM is not found in the environment, then
CAMLRUNPARAM will be used instead. If CAMLRUNPARAM is not found, then the
default values will be used.
PATH List of directories searched to find the bytecode executable file.
10.3 Dynamic loading of shared libraries
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On platforms that support dynamic loading, ocamlrun can link dynamically with
C shared libraries (DLLs) providing additional C primitives beyond those
provided by the standard runtime system. The names for these libraries are
provided at link time as described in section 18.1.4), and recorded in the
bytecode executable file; ocamlrun, then, locates these libraries and resolves
references to their primitives when the bytecode executable program starts.
The ocamlrun command searches shared libraries in the following directories,
in the order indicated:
1. Directories specified on the ocamlrun command line with the -I option.
2. Directories specified in the CAML_LD_LIBRARY_PATH environment variable.
3. Directories specified at link-time via the -dllpath option to ocamlc.
(These directories are recorded in the bytecode executable file.)
4. Directories specified in the file ld.conf. This file resides in the
Objective Caml standard library directory, and lists directory names (one
per line) to be searched. Typically, it contains only one line naming the
stublibs subdirectory of the Objective Caml standard library directory.
Users can add there the names of other directories containing
frequently-used shared libraries; however, for consistency of installation,
we recommend that shared libraries are installed directly in the system
stublibs directory, rather than adding lines to the ld.conf file.
5. Default directories searched by the system dynamic loader. Under Unix,
these generally include /lib and /usr/lib, plus the directories listed in
the file /etc/ld.so.conf and the environment variable LD_LIBRARY_PATH. Under
Windows, these include the Windows system directories, plus the directories
listed in the PATH environment variable.
10.4 Common errors
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This section describes and explains the most frequently encountered error
messages.
filename: no such file or directory If filename is the name of a
self-executable bytecode file, this means that either that file does not
exist, or that it failed to run the ocamlrun bytecode interpreter on itself.
The second possibility indicates that Objective Caml has not been properly
installed on your system.
Cannot exec ocamlrun (When launching a self-executable bytecode file.) The
ocamlrun could not be found in the executable path. Check that Objective
Caml has been properly installed on your system.
Cannot find the bytecode file The file that ocamlrun is trying to execute
(e.g. the file given as first non-option argument to ocamlrun) either does
not exist, or is not a valid executable bytecode file.
Truncated bytecode file The file that ocamlrun is trying to execute is not a
valid executable bytecode file. Probably it has been truncated or mangled
since created. Erase and rebuild it.
Uncaught exception The program being executed contains a "stray" exception.
That is, it raises an exception at some point, and this exception is never
caught. This causes immediate termination of the program. The name of the
exception is printed, along with its string and integer arguments (arguments
of more complex types are not correctly printed). To locate the context of
the uncaught exception, compile the program with the -g option and either
run it again under the ocamldebug debugger (see chapter 16), or run it with
ocamlrun -b or with the OCAMLRUNPARAM environment variable set to b=1.
Out of memory The program being executed requires more memory than available.
Either the program builds excessively large data structures; or the program
contains too many nested function calls, and the stack overflows. In some
cases, your program is perfectly correct, it just requires more memory than
your machine provides. In other cases, the "out of memory" message reveals
an error in your program: non-terminating recursive function, allocation of
an excessively large array or string, attempts to build an infinite list or
other data structure, ...
To help you diagnose this error, run your program with the -v option to
ocamlrun, or with the OCAMLRUNPARAM environment variable set to v=63. If it
displays lots of "Growing stack..." messages, this is probably a looping
recursive function. If it displays lots of "Growing heap..." messages, with
the heap size growing slowly, this is probably an attempt to construct a
data structure with too many (infinitely many?) cells. If it displays few
"Growing heap..." messages, but with a huge increment in the heap size, this
is probably an attempt to build an excessively large array or string.
Chapter 11 Native-code compilation (ocamlopt)
************************************************
This chapter describes the Objective Caml high-performance native-code
compiler ocamlopt, which compiles Caml source files to native code object files
and link these object files to produce standalone executables.
The native-code compiler is only available on certain platforms. It produces
code that runs faster than the bytecode produced by ocamlc, at the cost of
increased compilation time and executable code size. Compatibility with the
bytecode compiler is extremely high: the same source code should run
identically when compiled with ocamlc and ocamlopt.
It is not possible to mix native-code object files produced by ocamlopt with
bytecode object files produced by ocamlc: a program must be compiled entirely
with ocamlopt or entirely with ocamlc. Native-code object files produced by
ocamlopt cannot be loaded in the toplevel system ocaml.
11.1 Overview of the compiler
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The ocamlopt command has a command-line interface very close to that of
ocamlc. It accepts the same types of arguments, and processes them
sequentially:
- Arguments ending in .mli are taken to be source files for compilation unit
interfaces. Interfaces specify the names exported by compilation units: they
declare value names with their types, define public data types, declare
abstract data types, and so on. From the file x.mli, the ocamlopt compiler
produces a compiled interface in the file x.cmi. The interface produced is
identical to that produced by the bytecode compiler ocamlc.
- Arguments ending in .ml are taken to be source files for compilation unit
implementations. Implementations provide definitions for the names exported
by the unit, and also contain expressions to be evaluated for their
side-effects. From the file x.ml, the ocamlopt compiler produces two files:
x.o, containing native object code, and x.cmx, containing extra information
for linking and optimization of the clients of the unit. The compiled
implementation should always be referred to under the name x.cmx (when given
a .o file, ocamlopt assumes that it contains code compiled from C, not from
Caml).
The implementation is checked against the interface file x.mli (if it exists)
as described in the manual for ocamlc (chapter 8).
- Arguments ending in .cmx are taken to be compiled object code. These files
are linked together, along with the object files obtained by compiling .ml
arguments (if any), and the Caml standard library, to produce a native-code
executable program. The order in which .cmx and .ml arguments are presented
on the command line is relevant: compilation units are initialized in that
order at run-time, and it is a link-time error to use a component of a unit
before having initialized it. Hence, a given x.cmx file must come before all
.cmx files that refer to the unit x.
- Arguments ending in .cmxa are taken to be libraries of object code. Such a
library packs in two files (lib.cmxa and lib.a) a set of object files
(.cmx/.o files). Libraries are build with ocamlopt -a (see the description
of the -a option below). The object files contained in the library are
linked as regular .cmx files (see above), in the order specified when the
library was built. The only difference is that if an object file contained
in a library is not referenced anywhere in the program, then it is not
linked in.
- Arguments ending in .c are passed to the C compiler, which generates a .o
object file. This object file is linked with the program.
- Arguments ending in .o, .a or .so (.obj, .lib and .dll under Windows) are
assumed to be C object files and libraries. They are linked with the
program.
The output of the linking phase is a regular Unix or Windows executable file.
It does not need ocamlrun to run.
11.2 Options
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The following command-line options are recognized by ocamlopt.
-a Build a library (.cmxa/.a file) with the object files (.cmx/.o files)
given on the command line, instead of linking them into an executable file.
The name of the library can be set with the -o option. The default name is
library.cmxa.
If -cclib or -ccopt options are passed on the command line, these options are
stored in the resulting .cmxa library. Then, linking with this library
automatically adds back the -cclib and -ccopt options as if they had been
provided on the command line, unless the -noautolink option is given.
-c Compile only. Suppress the linking phase of the compilation. Source code
files are turned into compiled files, but no executable file is produced.
This option is useful to compile modules separately.
-cc ccomp Use ccomp as the C linker called to build the final executable and
as the C compiler for compiling .c source files.
-cclib -llibname Pass the -llibname option to the linker. This causes the
given C library to be linked with the program.
-ccopt option Pass the given option to the C compiler and linker. For
instance, -ccopt -Ldir causes the C linker to search for C libraries in
directory dir.
-compact Optimize the produced code for space rather than for time. This
results in slightly smaller but slightly slower programs. The default is to
optimize for speed.
-dtypes Dump detailed type information. The information for file x.ml is put
into file x.annot. In case of a type error, dump all the information
inferred by the type-checker before the error. The x.annot file can be used
with the emacs commands given in emacs/caml-types.el to display types
interactively.
-for-pack module-path Generate an object file (.cmx/.o file) that can later
be included as a sub-module (with the given access path) of a compilation
unit constructed with -pack. For instance, ocamlopt -for-pack P -c A.ml will
generate a.cmx and a.o files that can later be used with ocamlopt -pack -o
P.cmx a.cmx.
-g Add debugging information while compiling and linking. This option is
required in order to produce stack backtraces when the program terminates on
an uncaught exception (see section 10.2).
-i Cause the compiler to print all defined names (with their inferred types
or their definitions) when compiling an implementation (.ml file). No
compiled files (.cmo and .cmi files) are produced. This can be useful to
check the types inferred by the compiler. Also, since the output follows the
syntax of interfaces, it can help in writing an explicit interface (.mli
file) for a file: just redirect the standard output of the compiler to a
.mli file, and edit that file to remove all declarations of unexported
names.
-I directory Add the given directory to the list of directories searched for
compiled interface files (.cmi), compiled object code files (.cmx), and
libraries (.cmxa). By default, the current directory is searched first, then
the standard library directory. Directories added with -I are searched after
the current directory, in the order in which they were given on the command
line, but before the standard library directory.
If the given directory starts with +, it is taken relative to the standard
library directory. For instance, -I +labltk adds the subdirectory labltk of
the standard library to the search path.
-inline n Set aggressiveness of inlining to n, where n is a positive integer.
Specifying -inline 0 prevents all functions from being inlined, except those
whose body is smaller than the call site. Thus, inlining causes no expansion
in code size. The default aggressiveness, -inline 1, allows slightly larger
functions to be inlined, resulting in a slight expansion in code size.
Higher values for the -inline option cause larger and larger functions to
become candidate for inlining, but can result in a serious increase in code
size.
-linkall Forces all modules contained in libraries to be linked in. If this
flag is not given, unreferenced modules are not linked in. When building a
library (-a flag), setting the -linkall flag forces all subsequent links of
programs involving that library to link all the modules contained in the
library.
-noassert Turn assertion checking off: assertions are not compiled. This flag
has no effect when linking already compiled files.
-noautolink When linking .cmxa libraries, ignore -cclib and -ccopt options
potentially contained in the libraries (if these options were given when
building the libraries). This can be useful if a library contains incorrect
specifications of C libraries or C options; in this case, during linking,
set -noautolink and pass the correct C libraries and options on the command
line.
-nolabels Ignore non-optional labels in types. Labels cannot be used in
applications, and parameter order becomes strict.
-o exec-file Specify the name of the output file produced by the linker. The
default output name is a.out under Unix and camlprog.exe under Windows. If
the -a option is given, specify the name of the library produced. If the
-pack option is given, specify the name of the packed object file produced.
If the -output-obj option is given, specify the name of the output file
produced.
-output-obj Cause the linker to produce a C object file instead of an
executable file. This is useful to wrap Caml code as a C library, callable
from any C program. See chapter 18, section 18.7.5. The name of the output
object file is camlprog.o by default; it can be set with the -o option.
-p Generate extra code to write profile information when the program is
executed. The profile information can then be examined with the analysis
program gprof. (See chapter 17 for more information on profiling.) The -p
option must be given both at compile-time and at link-time. Linking object
files not compiled with -p is possible, but results in less precise
profiling.
Unix:
See the Unix manual page for gprof(1) for more information about the
profiles.
Full support for gprof is only available for certain platforms
(currently: Intel x86/Linux and Alpha/Digital Unix). On other platforms,
the -p option will result in a less precise profile (no call graph
information, only a time profile).
Windows:
The -p option does not work under Windows.
-pack Build an object file (.cmx/.o file) and its associated compiled
interface (.cmi) that combines the .cmx object files given on the command
line, making them appear as sub-modules of the output .cmx file. The name of
the output .cmx file must be given with the -o option. For instance,
<< ocamlopt -pack -o P.cmx A.cmx B.cmx C.cmx
>>
generates compiled files P.cmx, P.o and P.cmi describing a compilation unit
having three sub-modules A, B and C, corresponding to the contents of the
object files A.cmx, B.cmx and C.cmx. These contents can be referenced as
P.A, P.B and P.C in the remainder of the program.
The .cmx object files being combined must have been compiled with the
appropriate -for-pack option. In the example above, A.cmx, B.cmx and C.cmx
must have been compiled with ocamlopt -for-pack P.
Multiple levels of packing can be achieved by combining -pack with -for-pack.
Consider the following example:
<< ocamlopt -for-pack P.Q -c A.ml
ocamlopt -pack -o Q.cmx -for-pack P A.cmx
ocamlopt -for-pack P -c B.ml
ocamlopt -pack -o P.cmx Q.cmx B.cmx
>>
The resulting P.cmx object file has sub-modules P.Q, P.Q.A and P.B.
-pp command Cause the compiler to call the given command as a preprocessor
for each source file. The output of command is redirected to an intermediate
file, which is compiled. If there are no compilation errors, the
intermediate file is deleted afterwards. The name of this file is built from
the basename of the source file with the extension .ppi for an interface
(.mli) file and .ppo for an implementation (.ml) file.
-principal Check information path during type-checking, to make sure that all
types are derived in a principal way. All programs accepted in -principal
mode are also accepted in default mode with equivalent types, but different
binary signatures.
-rectypes Allow arbitrary recursive types during type-checking. By default,
only recursive types where the recursion goes through an object type are
supported. Note that once you have created an interface using this flag, you
must use it again for all dependencies.
-S Keep the assembly code produced during the compilation. The assembly code
for the source file x.ml is saved in the file x.s.
-thread Compile or link multithreaded programs, in combination with the
system threads library described in chapter 24.
-unsafe Turn bound checking off on array and string accesses (the v.(i) and
s.[i] constructs). Programs compiled with -unsafe are therefore faster, but
unsafe: anything can happen if the program accesses an array or string
outside of its bounds. Additionally, turn off the check for zero divisor in
integer division and modulus operations. With -unsafe, an integer division
(or modulus) by zero can halt the program or continue with an unspecified
result instead of raising a Division_by_zero exception.
-v Print the version number of the compiler and the location of the standard
library directory, then exit.
-verbose Print all external commands before they are executed, in particular
invocations of the assembler, C compiler, and linker.
-version Print the version number of the compiler in short form (e.g. 3.06),
then exit.
-w warning-list Enable or disable warnings according to the argument
warning-list. The argument is a string of one or several characters, with
the following meaning for each character:
A/a enable/disable all warnings.
C/c enable/disable warnings for suspicious comments.
D/d enable/disable warnings for deprecated features.
E/e enable/disable warnings for fragile pattern matchings (matchings that
would remain complete if additional constructors are added to a variant
type involved).
F/f enable/disable warnings for partially applied functions (i.e. f x;
expr where the application f x has a function type).
L/l enable/disable warnings for labels omitted in application.
M/m enable/disable warnings for overriden methods.
P/p enable/disable warnings for partial matches (missing cases in pattern
matchings).
S/s enable/disable warnings for statements that do not have type unit
(e.g. expr1; expr2 when expr1 does not have type unit).
U/u enable/disable warnings for unused (redundant) match cases.
V/v enable/disable warnings for hidden instance variables.
Y/y enable/disable warnings for unused variables bound with the let or as
keywords and that don't start with an underscore.
Z/z enable/disable warnings for all unused variables that don't start with
an underscore.
X/x enable/disable all other warnings.
The default setting is -w Aelyz (all warnings enabled except fragile
matchings, omitted labels, unused variables).
-warn-error warning-list Turn the warnings indicated in the argument
warning-list into errors. The compiler will stop on an error as soon as one
of these warnings is emitted, instead of going on. The warning-list is a
string of one or several characters, with the same meaning as for the -w
option: an uppercase character turns the corresponding warning into an
error, a lowercase character leaves it as a warning. The default setting is
-warn-error a (all warnings are not treated as errors).
-where Print the location of the standard library.
Options for the IA32 architecture
The IA32 code generator (Intel Pentium, AMD Athlon) supports the following
additional option:
-ffast-math Use the IA32 instructions to compute trigonometric and
exponential functions, instead of calling the corresponding library
routines. The functions affected are: atan, atan2, cos, log, log10, sin,
sqrt, and tan. The resulting code runs faster, but the range of supported
arguments and the precision of the result can be reduced. In particular,
trigonometric operations cos, sin, tan have their range reduced to [-2^64,
2^64].
Options for the Sparc architecture
The Sparc code generator supports the following additional options:
-march=v8 Generate SPARC version 8 code.
-march=v9 Generate SPARC version 9 code.
The default is to generate code for SPARC version 7, which runs on all SPARC
processors.
11.3 Common errors
*=*=*=*=*=*=*=*=*=*
The error messages are almost identical to those of ocamlc. See section 8.4.
11.4 Running executables produced by ocamlopt
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Executables generated by ocamlopt are native, statically-linked, stand-alone
executable files that can be invoked directly. They do not depend on the
ocamlrun bytecode runtime system.
During execution of an ocamlopt-generated executable, the following
environment variables are also consulted:
OCAMLRUNPARAM Same usage as in ocamlrun (see section 10.2), except that
option l is ignored (the operating system's stack size limit is used
instead) and option b is ignored (stack backtraces on uncaught exceptions
are not printed).
CAMLRUNPARAM If OCAMLRUNPARAM is not found in the environment, then
CAMLRUNPARAM will be used instead. If CAMLRUNPARAM is not found, then the
default values will be used.
11.5 Compatibility with the bytecode compiler
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This section lists the known incompatibilities between the bytecode compiler
and the native-code compiler. Except on those points, the two compilers should
generate code that behave identically.
- Signals are detected only when the program performs an allocation in the
heap. That is, if a signal is delivered while in a piece of code that does
not allocate, its handler will not be called until the next heap allocation.
- Stack overflow, typically caused by excessively deep recursion, is handled
in one of the following ways, depending on the platform used:
- By raising a Stack_overflow exception, like the bytecode compiler does.
(IA32/Linux, AMD64/Linux, PowerPC/MacOSX, MS Windows 32-bit ports).
- By aborting the program on a "segmentation fault" signal. (All other Unix
systems.)
- By terminating the program silently. (MS Windows 64 bits).
- On IA32 processors only (Intel Pentium, AMD Athlon, etc, in 32-bit mode),
some intermediate results in floating-point computations are kept in
extended precision rather than being rounded to double precision like the
bytecode compiler always does. Floating-point results can therefore differ
between bytecode and native code; in general, the results obtained with
native code are "more exact" (less affected by rounding errors and loss of
precision).
- On the Alpha processor only, floating-point operations involving infinite or
denormalized numbers can abort the program on a "floating-point exception"
signal.
Chapter 12 Lexer and parser generators (ocamllex, ocamlyacc)
***************************************************************
This chapter describes two program generators: ocamllex, that produces a
lexical analyzer from a set of regular expressions with associated semantic
actions, and ocamlyacc, that produces a parser from a grammar with associated
semantic actions.
These program generators are very close to the well-known lex and yacc
commands that can be found in most C programming environments. This chapter
assumes a working knowledge of lex and yacc: while it describes the input
syntax for ocamllex and ocamlyacc and the main differences with lex and yacc,
it does not explain the basics of writing a lexer or parser description in lex
and yacc. Readers unfamiliar with lex and yacc are referred to "Compilers:
principles, techniques, and tools" by Aho, Sethi and Ullman (Addison-Wesley,
1986), or "Lex & Yacc", by Levine, Mason and Brown (O'Reilly, 1992).
12.1 Overview of ocamllex
*=*=*=*=*=*=*=*=*=*=*=*=*=
The ocamllex command produces a lexical analyzer from a set of regular
expressions with attached semantic actions, in the style of lex. Assuming the
input file is lexer.mll, executing
<<
ocamllex lexer.mll
>>
produces Caml code for a lexical analyzer in file lexer.ml. This file
defines one lexing function per entry point in the lexer definition. These
functions have the same names as the entry points. Lexing functions take as
argument a lexer buffer, and return the semantic attribute of the corresponding
entry point.
Lexer buffers are an abstract data type implemented in the standard library
module Lexing. The functions Lexing.from_channel, Lexing.from_string and
Lexing.from_function create lexer buffers that read from an input channel, a
character string, or any reading function, respectively. (See the description
of module Lexing in chapter 20.)
When used in conjunction with a parser generated by ocamlyacc, the semantic
actions compute a value belonging to the type token defined by the generated
parsing module. (See the description of ocamlyacc below.)
12.1.1 Options
===============
The following command-line options are recognized by ocamllex.
-o output-file Specify the name of the output file produced by ocamllex.
Default is lexer.ml, ocamllex being invoked as ocamllex lexer.mll.
-ml Output code that does not use the Caml built-in automata interpreter.
Instead, the automaton is encoded by Caml functions. This option is useful
for debugging ocamllex, using it for production lexers is not recommended.
-q Quiet mode. ocamllex normally outputs informational messages to standard
output. They are suppressed if option -q is used.
-version Print version and exit.
12.2 Syntax of lexer definitions
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The format of lexer definitions is as follows:
<<
{ header }
let ident = regexp ...
rule entrypoint [arg_1... arg_n] =
parse regexp { action }
| ...
| regexp { action }
and entrypoint [arg_1... arg_n] =
parse ...
and ...
{ trailer }
>>
Comments are delimited by (* and *), as in Caml. The parse keyword, can be
replaced by the shortest keyword, with the semantic consequences explained
below.
12.2.1 Header and trailer
==========================
The header and trailer sections are arbitrary Caml text enclosed in curly
braces. Either or both can be omitted. If present, the header text is copied as
is at the beginning of the output file and the trailer text at the end.
Typically, the header section contains the `open' directives required by the
actions, and possibly some auxiliary functions used in the actions.
12.2.2 Naming regular expressions
==================================
Between the header and the entry points, one can give names to
frequently-occurring regular expressions. This is written let ident = regexp.
In regular expressions that follow this declaration, the identifier ident can
be used as shorthand for regexp.
12.2.3 Entry points
====================
The names of the entry points must be valid identifiers for Caml values
(starting with a lowercase letter). Similarily, the arguments arg_1... arg_n
must be valid identifiers for Caml. Each entry point becomes a Caml function
that takes n+1 arguments, the extra implicit last argument being of type
Lexing.lexbuf. Characters are read from the Lexing.lexbuf argument and matched
against the regular expressions provided in the rule, until a prefix of the
input matches one of the rule. The corresponding action is then evaluated and
returned as the result of the function.
If several regular expressions match a prefix of the input, the "longest
match" rule applies: the regular expression that matches the longest prefix of
the input is selected. In case of tie, the regular expression that occurs
earlier in the rule is selected.
However, if lexer rules are introduced with the shortest keyword in place of
the parse keyword, then the "shortest match" rule applies: the shortest prefix
of the input is selected. In case of tie, the regular expression that occurs
earlier in the rule is still selected. This feature is not intended for use in
ordinary lexical analyzers, it may facilitate the use of ocamllex as a simple
text processing tool.
12.2.4 Regular expressions
===========================
The regular expressions are in the style of lex, with a more Caml-like
syntax.
regexp ::= ...
' regular-char | escape-sequence ' A character constant, with the same
syntax as Objective Caml character constants. Match the denoted character.
_ (Underscore.) Match any character.
eof Match the end of the lexer input.
Note: On some systems, with interactive input, an end-of-file may be followed
by more characters. However, ocamllex will not correctly handle regular
expressions that contain eof followed by something else.
" { string-character } " A string constant, with the same syntax as Objective
Caml string constants. Match the corresponding sequence of characters.
[ character-set ] Match any single character belonging to the given character
set. Valid character sets are: single character constants ' c '; ranges of
characters ' c_1 ' - ' c_2 ' (all characters between c_1 and c_2,
inclusive); and the union of two or more character sets, denoted by
concatenation.
[ ^ character-set ] Match any single character not belonging to the given
character set.
regexp_1 # regexp_2 (Difference of character sets). Regular expressions
regexp_1 and regexp_2 must be character sets defined with [... ] (or a a
single character expression or underscore _). Match the difference of the
two specified character sets.
regexp * (Repetition.) Match the concatenation of zero or more strings that
match regexp.
regexp + (Strict repetition.) Match the concatenation of one or more strings
that match regexp.
regexp ? (Option.) Match either the empty string, or a string matching
regexp.
regexp_1 | regexp_2 (Alternative.) Match any string that matches either
regexp_1 or regexp_2
regexp_1 regexp_2 (Concatenation.) Match the concatenation of two strings,
the first matching regexp_1, the second matching regexp_2.
( regexp ) Match the same strings as regexp.
ident Reference the regular expression bound to ident by an earlier let ident
= regexp definition.
regexp as ident Bind the substring matched by regexp to identifier ident.
Concerning the precedences of operators, * and + have highest precedence,
followed by ?, then concatenation, then | (alternation), then as.
12.2.5 Actions
===============
The actions are arbitrary Caml expressions. They are evaluated in a context
where the identifiers defined by using the as construct are bound to subparts
of the matched string. Additionally, lexbuf is bound to the current lexer
buffer. Some typical uses for lexbuf, in conjunction with the operations on
lexer buffers provided by the Lexing standard library module, are listed below.
Lexing.lexeme lexbuf Return the matched string.
Lexing.lexeme_char lexbuf n Return the n^th character in the matched string.
The first character corresponds to n = 0.
Lexing.lexeme_start lexbuf Return the absolute position in the input text of
the beginning of the matched string. The first character read from the input
text has position 0.
Lexing.lexeme_end lexbuf Return the absolute position in the input text of
the end of the matched string. The first character read from the input text
has position 0.
entrypoint [exp_1... exp_n] lexbuf (Where entrypoint is the name of another
entry point in the same lexer definition.) Recursively call the lexer on the
given entry point. Notice that lexbuf is the last argument. Useful for
lexing nested comments, for example.
12.2.6 Variables in regular expressions
========================================
The as construct is similar to "groups" as provided by numerous regular
expression packages. The type of these variables can be string, char, string
option or char option.
We first consider the case of linear patterns, that is the case when all as
bound variables are distinct. In regexp as ident, the type of ident normally
is string (or string option) except when regexp is a character constant, an
underscore, a string constant of length one, a character set specification, or
an alternation of those. Then, the type of ident is char (or char option).
Option types are introduced when overall rule matching does not imply matching
of the bound sub-pattern. This is in particular the case of ( regexp as ident
) ? and of regexp_1 | ( regexp_2 as ident ).
There is no linearity restriction over as bound variables. When a variable is
bound more than once, the previous rules are to be extended as follows:
- A variable is a char variable when all its occurrences bind char occurrences
in the previous sense.
- A variable is an option variable when the overall expression can be matched
without binding this variable.
For instance, in `('a' as x) | ( 'a' (_ as x) )' the variable `x' is of type
char, whereas in `("ab" as x) | ( 'a' (_ as x) ? )' the variable `x' is of
type string option.
In some cases, a sucessful match may not yield a unique set of bindings. For
instance the matching of `aba' by the regular expression `(('a'|"ab") as x)
(("ba"|'a') as y)' may result in binding either `x' to `"ab"' and `y' to `"a"',
or `x' to `"a"' and `y' to `"ba"'. The automata produced ocamllex on such
ambiguous regular expressions will select one of the possible resulting sets of
bindings. The selected set of bindings is purposely left unspecified.
12.2.7 Reserved identifiers
============================
All identifiers starting with __ocaml_lex are reserved for use by ocamllex;
do not use any such identifier in your programs.
12.3 Overview of ocamlyacc
*=*=*=*=*=*=*=*=*=*=*=*=*=*
The ocamlyacc command produces a parser from a context-free grammar
specification with attached semantic actions, in the style of yacc. Assuming
the input file is grammar.mly, executing
<<
ocamlyacc options grammar.mly
>>
produces Caml code for a parser in the file grammar.ml, and its interface in
file grammar.mli.
The generated module defines one parsing function per entry point in the
grammar. These functions have the same names as the entry points. Parsing
functions take as arguments a lexical analyzer (a function from lexer buffers
to tokens) and a lexer buffer, and return the semantic attribute of the
corresponding entry point. Lexical analyzer functions are usually generated
from a lexer specification by the ocamllex program. Lexer buffers are an
abstract data type implemented in the standard library module Lexing. Tokens
are values from the concrete type token, defined in the interface file
grammar.mli produced by ocamlyacc.
12.4 Syntax of grammar definitions
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Grammar definitions have the following format:
<<
%{
header
%}
declarations
%%
rules
%%
trailer
>>
Comments are enclosed between `/*' and `*/' (as in C) in the "declarations"
and "rules" sections, and between `(*' and `*)' (as in Caml) in the "header"
and "trailer" sections.
12.4.1 Header and trailer
==========================
The header and the trailer sections are Caml code that is copied as is into
file grammar.ml. Both sections are optional. The header goes at the beginning
of the output file; it usually contains open directives and auxiliary functions
required by the semantic actions of the rules. The trailer goes at the end of
the output file.
12.4.2 Declarations
====================
Declarations are given one per line. They all start with a `%' sign.
%token constr ... constr Declare the given symbols constr ... constr as
tokens (terminal symbols). These symbols are added as constant constructors
for the token concrete type.
%token < typexpr > constr ... constr Declare the given symbols constr ...
constr as tokens with an attached attribute of the given type. These symbols
are added as constructors with arguments of the given type for the token
concrete type. The typexpr part is an arbitrary Caml type expression, except
that all type constructor names must be fully qualified (e.g.
Modname.typename) for all types except standard built-in types, even if the
proper `open' directives (e.g. `open Modname') were given in the header
section. That's because the header is copied only to the .ml output file,
but not to the .mli output file, while the typexpr part of a `%token'
declaration is copied to both.
%start symbol ... symbol Declare the given symbols as entry points for the
grammar. For each entry point, a parsing function with the same name is
defined in the output module. Non-terminals that are not declared as entry
points have no such parsing function. Start symbols must be given a type
with the `%type' directive below.
%type < typexpr > symbol ... symbol Specify the type of the semantic
attributes for the given symbols. This is mandatory for start symbols only.
Other nonterminal symbols need not be given types by hand: these types will
be inferred when running the output files through the Objective Caml
compiler (unless the `-s' option is in effect). The typexpr part is an
arbitrary Caml type expression, except that all type constructor names must
be fully qualified, as explained above for %token.
%left symbol ... symbol
%right symbol ... symbol
%nonassoc symbol ... symbol
Associate precedences and associativities to the given symbols. All symbols on
the same line are given the same precedence. They have higher precedence
than symbols declared before in a `%left', `%right' or `%nonassoc' line.
They have lower precedence than symbols declared after in a `%left',
`%right' or `%nonassoc' line. The symbols are declared to associate to the
left (`%left'), to the right (`%right'), or to be non-associative
(`%nonassoc'). The symbols are usually tokens. They can also be dummy
nonterminals, for use with the `%prec' directive inside the rules.
The precedence declarations are used in the following way to resolve
reduce/reduce and shift/reduce conflicts:
- Tokens and rules have precedences. By default, the precedence of a rule
is the precedence of its rightmost terminal. You can override this
default by using the %prec directive in the rule.
- A reduce/reduce conflict is resolved in favor of the first rule (in the
order given by the source file), and ocamlyacc outputs a warning.
- A shift/reduce conflict is resolved by comparing the precedence of the
rule to be reduced with the precedence of the token to be shifted. If the
precedence of the rule is higher, then the rule will be reduced; if the
precedence of the token is higher, then the token will be shifted.
- A shift/reduce conflict between a rule and a token with the same
precedence will be resolved using the associativity: if the token is
left-associative, then the parser will reduce; if the token is
right-associative, then the parser will shift. If the token is
non-associative, then the parser will declare a syntax error.
- When a shift/reduce conflict cannot be resolved using the above method,
then ocamlyacc will output a warning and the parser will always shift.
12.4.3 Rules
=============
The syntax for rules is as usual:
<<
nonterminal :
symbol ... symbol { semantic-action }
| ...
| symbol ... symbol { semantic-action }
;
>>
Rules can also contain the `%prec 'symbol directive in the right-hand side
part, to override the default precedence and associativity of the rule with the
precedence and associativity of the given symbol.
Semantic actions are arbitrary Caml expressions, that are evaluated to
produce the semantic attribute attached to the defined nonterminal. The
semantic actions can access the semantic attributes of the symbols in the
right-hand side of the rule with the `$' notation: `$1' is the attribute for
the first (leftmost) symbol, `$2' is the attribute for the second symbol, etc.
The rules may contain the special symbol error to indicate resynchronization
points, as in yacc.
Actions occurring in the middle of rules are not supported.
Nonterminal symbols are like regular Caml symbols, except that they cannot
end with ' (single quote).
12.4.4 Error handling
======================
Error recovery is supported as follows: when the parser reaches an error
state (no grammar rules can apply), it calls a function named parse_error with
the string "syntax error" as argument. The default parse_error function does
nothing and returns, thus initiating error recovery (see below). The user can
define a customized parse_error function in the header section of the grammar
file.
The parser also enters error recovery mode if one of the grammar actions
raises the Parsing.Parse_error exception.
In error recovery mode, the parser discards states from the stack until it
reaches a place where the error token can be shifted. It then discards tokens
from the input until it finds three successive tokens that can be accepted, and
starts processing with the first of these. If no state can be uncovered where
the error token can be shifted, then the parser aborts by raising the
Parsing.Parse_error exception.
Refer to documentation on yacc for more details and guidance in how to use
error recovery.
12.5 Options
*=*=*=*=*=*=*
The ocamlyacc command recognizes the following options:
-bprefix Name the output files prefix.ml, prefix.mli, prefix.output, instead
of the default naming convention.
-v Generate a description of the parsing tables and a report on conflicts
resulting from ambiguities in the grammar. The description is put in file
grammar.output.
-version Print version and exit.
At run-time, the ocamlyacc-generated parser can be debugged by setting the p
option in the OCAMLRUNPARAM environment variable (see section 10.2). This
causes the pushdown automaton executing the parser to print a trace of its
action (tokens shifted, rules reduced, etc). The trace mentions rule numbers
and state numbers that can be interpreted by looking at the file grammar.output
generated by ocamlyacc -v.
12.6 A complete example
*=*=*=*=*=*=*=*=*=*=*=*=
The all-time favorite: a desk calculator. This program reads arithmetic
expressions on standard input, one per line, and prints their values. Here is
the grammar definition:
<< /* File parser.mly */
%token <int> INT
%token PLUS MINUS TIMES DIV
%token LPAREN RPAREN
%token EOL
%left PLUS MINUS /* lowest precedence */
%left TIMES DIV /* medium precedence */
%nonassoc UMINUS /* highest precedence */
%start main /* the entry point */
%type <int> main
%%
main:
expr EOL { $1 }
;
expr:
INT { $1 }
| LPAREN expr RPAREN { $2 }
| expr PLUS expr { $1 + $3 }
| expr MINUS expr { $1 - $3 }
| expr TIMES expr { $1 * $3 }
| expr DIV expr { $1 / $3 }
| MINUS expr %prec UMINUS { - $2 }
;
>>
Here is the definition for the corresponding lexer:
<< (* File lexer.mll *)
{
open Parser (* The type token is defined in parser.mli *)
exception Eof
}
rule token = parse
[' ' '\t'] { token lexbuf } (* skip blanks *)
| ['\n' ] { EOL }
| ['0'-'9']+ as lxm { INT(int_of_string lxm) }
| '+' { PLUS }
| '-' { MINUS }
| '*' { TIMES }
| '/' { DIV }
| '(' { LPAREN }
| ')' { RPAREN }
| eof { raise Eof }
>>
Here is the main program, that combines the parser with the lexer:
<< (* File calc.ml *)
let _ =
try
let lexbuf = Lexing.from_channel stdin in
while true do
let result = Parser.main Lexer.token lexbuf in
print_int result; print_newline(); flush stdout
done
with Lexer.Eof ->
exit 0
>>
To compile everything, execute:
<< ocamllex lexer.mll # generates lexer.ml
ocamlyacc parser.mly # generates parser.ml and parser.mli
ocamlc -c parser.mli
ocamlc -c lexer.ml
ocamlc -c parser.ml
ocamlc -c calc.ml
ocamlc -o calc lexer.cmo parser.cmo calc.cmo
>>
12.7 Common errors
*=*=*=*=*=*=*=*=*=*
ocamllex: transition table overflow, automaton is too big
The deterministic automata generated by ocamllex are limited to at most 32767
transitions. The message above indicates that your lexer definition is too
complex and overflows this limit. This is commonly caused by lexer
definitions that have separate rules for each of the alphabetic keywords of
the language, as in the following example.
<<rule token = parse
"keyword1" { KWD1 }
| "keyword2" { KWD2 }
| ...
| "keyword100" { KWD100 }
| ['A'-'Z' 'a'-'z'] ['A'-'Z' 'a'-'z' '0'-'9' '_'] * as id
{ IDENT id}
>>
To keep the generated automata small, rewrite those definitions with only one
general "identifier" rule, followed by a hashtable lookup to separate
keywords from identifiers:
<<{ let keyword_table = Hashtbl.create 53
let _ =
List.iter (fun (kwd, tok) -> Hashtbl.add keyword_table kwd tok)
[ "keyword1", KWD1;
"keyword2", KWD2; ...
"keyword100", KWD100 ]
}
rule token = parse
['A'-'Z' 'a'-'z'] ['A'-'Z' 'a'-'z' '0'-'9' '_'] * as id
{ try
Hashtbl.find keyword_table id
with Not_found ->
IDENT id }
>>
ocamllex: Position memory overflow, too many bindings The deterministic
automata generated by ocamllex maintains a table of positions inside the
scanned lexer buffer. The size of this table is limited to at most 255
cells. This error should not show up in normal situations.
Chapter 13 Dependency generator (ocamldep)
*********************************************
The ocamldep command scans a set of Objective Caml source files (.ml and .mli
files) for references to external compilation units, and outputs dependency
lines in a format suitable for the make utility. This ensures that make will
compile the source files in the correct order, and recompile those files that
need to when a source file is modified.
The typical usage is:
<<
ocamldep options *.mli *.ml > .depend
>>
where *.mli *.ml expands to all source files in the current directory and
.depend is the file that should contain the dependencies. (See below for a
typical Makefile.)
Dependencies are generated both for compiling with the bytecode compiler
ocamlc and with the native-code compiler ocamlopt.
13.1 Options
*=*=*=*=*=*=*
The following command-line option is recognized by ocamldep.
-I directory Add the given directory to the list of directories searched for
source files. If a source file foo.ml mentions an external compilation unit
Bar, a dependency on that unit's interface bar.cmi is generated only if the
source for bar is found in the current directory or in one of the
directories specified with -I. Otherwise, Bar is assumed to be a module from
the standard library, and no dependencies are generated. For programs that
span multiple directories, it is recommended to pass ocamldep the same -I
options that are passed to the compiler.
-native Generate dependencies for a pure native-code program (no bytecode
version). When an implementation file (.ml file) has no explicit interface
file (.mli file), ocamldep generates dependencies on the bytecode compiled
file (.cmo file) to reflect interface changes. This can cause unnecessary
bytecode recompilations for programs that are compiled to native-code only.
The flag -native causes dependencies on native compiled files (.cmx) to be
generated instead of on .cmo files. (This flag makes no difference if all
source files have explicit .mli interface files.)
-version Print version and exit.
13.2 A typical Makefile
*=*=*=*=*=*=*=*=*=*=*=*=
Here is a template Makefile for a Objective Caml program.
<<OCAMLC=ocamlc
OCAMLOPT=ocamlopt
OCAMLDEP=ocamldep
INCLUDES= # all relevant -I options here
OCAMLFLAGS=$(INCLUDES) # add other options for ocamlc here
OCAMLOPTFLAGS=$(INCLUDES) # add other options for ocamlopt here
# prog1 should be compiled to bytecode, and is composed of three
# units: mod1, mod2 and mod3.
# The list of object files for prog1
PROG1_OBJS=mod1.cmo mod2.cmo mod3.cmo
prog1: $(PROG1_OBJS)
$(OCAMLC) -o prog1 $(OCAMLFLAGS) $(PROG1_OBJS)
# prog2 should be compiled to native-code, and is composed of two
# units: mod4 and mod5.
# The list of object files for prog2
PROG2_OBJS=mod4.cmx mod5.cmx
prog2: $(PROG2_OBJS)
$(OCAMLOPT) -o prog2 $(OCAMLFLAGS) $(PROG2_OBJS)
# Common rules
.SUFFIXES: .ml .mli .cmo .cmi .cmx
.ml.cmo:
$(OCAMLC) $(OCAMLFLAGS) -c $<
.mli.cmi:
$(OCAMLC) $(OCAMLFLAGS) -c $<
.ml.cmx:
$(OCAMLOPT) $(OCAMLOPTFLAGS) -c $<
# Clean up
clean:
rm -f prog1 prog2
rm -f *.cm[iox]
# Dependencies
depend:
$(OCAMLDEP) $(INCLUDES) *.mli *.ml > .depend
include .depend
>>
Chapter 14 The browser/editor (ocamlbrowser)
***********************************************
This chapter describes OCamlBrowser, a source and compiled interface browser,
written using LablTk. This is a useful companion to the programmer.
Its functions are:
- navigation through Objective Caml's modules (using compiled interfaces).
- source editing, type-checking, and browsing.
- integrated Objective Caml shell, running as a subprocess.
14.1 Invocation
*=*=*=*=*=*=*=*=
The browser is started by the command ocamlbrowser, as follows:
<<
ocamlbrowser options
>>
The following command-line options are recognized by ocamlbrowser.
-I directory Add the given directory to the list of directories searched for
source and compiled files. By default, only the standard library directory
is searched. The standard library can also be changed by setting the
OCAMLLIB environment variable.
-nolabels Ignore non-optional labels in types. Labels cannot be used in
applications, and parameter order becomes strict.
-oldui Old multi-window interface. The default is now more like Smalltalk's
class browser.
-rectypes Allow arbitrary recursive types during type-checking. By default,
only recursive types where the recursion goes through an object type are
supported.
-version Print version and exit.
-w warning-list Enable or disable warnings according to the argument
warning-list.
Most options can also be modified inside the application by the Modules -
Path editor and Compiler - Preferences commands. They are inherited when you
start a toplevel shell.
14.2 Viewer
*=*=*=*=*=*=
This is the first window you get when you start OCamlBrowser. It displays a
search window, and the list of modules in the load path. At the top a row of
menus.
- File - Open and File - Editor give access to the editor.
- File - Shell creates an Objective Caml subprocess in a shell.
- View - Show all defs displays the signature of the currently selected
module.
- View - Search entry shows/hides the search entry just below the menu bar.
- Modules - Path editor changes the load path. Modules - Reset cache rescans
the load path and resets the module cache. Do it if you recompile some
interface, or get confused about what is in the cache.
- Modules - Search symbol allows to search a symbol either by its name, like
the bottom line of the viewer, or, more interestingly, by its type. Exact
type searches for a type with exactly the same information as the pattern
(variables match only variables). Included type allows to give only partial
information: the actual type may take more arguments and return more
results, and variables in the pattern match anything. In both cases,
argument and tuple order is irrelevant (1), and unlabeled arguments in the
pattern match any label.
- The Search entry just below the menu bar allows one to search for an
identifier in all modules (wildcards "?" and "*" allowed). If you choose the
type option, the search is done by type inclusion (cf. Search Symbol -
Included type).
- The Close all button is there to dismiss the windows created by the Detach
button. By double-clicking on it you will quit the browser.
14.3 Module browsing
*=*=*=*=*=*=*=*=*=*=*
You select a module in the leftmost box by either cliking on it or pressing
return when it is selected. Fast access is available in all boxes pressing the
first few letter of the desired name. Double-clicking / double-return displays
the whole signature for the module.
Defined identifiers inside the module are displayed in a box to the right of
the previous one. If you click on one, this will either display its contents in
another box (if this is a sub-module) or display the signature for this
identifier below.
Signatures are clickable. Double clicking with the left mouse button on an
identifier in a signature brings you to its signature. A single click on the
right button pops up a menu displaying the type declaration for the selected
identifier. Its title, when selectable, also brings you to its signature.
At the bottom, a series of buttons, depending on the context.
- Detach copies the currently displayed signature in a new window, to keep it.
- Impl and Intf bring you to the implementation or interface of the currently
displayed signature, if it is available.
Control-S lets you search a string in the signature.
14.4 File editor
*=*=*=*=*=*=*=*=*
You can edit files with it, if you're not yet used to emacs. Otherwise you
can use it as a browser, making occasional corrections.
The Edit menu contains commands for jump (C-g), search (C-s), and sending the
current phrase (or selection if some text is selected) to a sub-shell (M-x).
For this last option, you may choose the shell via a dialog.
Essential functions are in the Compiler menu.
- Preferences opens a dialog to set internals of the editor and type-checker.
- Lex adds colors according to lexical categories.
- Typecheck verifies typing, and memorizes to let one see an expression's type
by double-clicking on it. This is also valid for interfaces. If an error
occurs, the part of the interface preceding the error is computed.
After typechecking, pressing the right button pops up a menu giving the type
of the pointed expression, and eventually allowing to follow some links.
- Clear errors dismisses type-checker error messages and warnings.
- Signature shows the signature of the current file (after type checking).
14.5 Shell
*=*=*=*=*=*
When you create a shell, a dialog is presented to you, letting you choose
which command you want to run, and the title of the shell (to choose it in the
Editor).
The executed subshell is given the current load path.
- File use a source file or load a bytecode file. You may also import the
browser's path into the subprocess.
- History M-p and M-n browse up and down.
- Signal C-c interrupts, and you can also kill the subprocess.
---------------------------------------
(1) To avoid combinatorial explosion of the search space, optional arguments
in the actual type are ignored in the actual if (1) there are too many of
them, and (2) they do not appear explicitly in the pattern.
Chapter 15 The documentation generator (ocamldoc)
****************************************************
This chapter describes OCamldoc, a tool that generates documentation from
special comments embedded in source files. The comments used by OCamldoc are of
the form (**...*) and follow the format described in section 15.2.
OCamldoc can produce documentation in various formats: HTML, LaTeX, TeXinfo,
Unix man pages, and dot dependency graphs. Moreover, users can add their own
custom generators, as explained in section 15.3.
In this chapter, we use the word element to refer to any of the following
parts of an OCaml source file: a type declaration, a value, a module, an
exception, a module type, a type constructor, a record field, a class, a class
type, a class method, a class value or a class inheritance clause.
15.1 Usage
*=*=*=*=*=*
15.1.1 Invocation
==================
OCamldoc is invoked via the command ocamldoc, as follows:
<<
ocamldoc options sourcefiles
>>
Options for choosing the output format
--------------------------------------
The following options determine the format for the generated documentation.
-html Generate documentation in HTML default format. The generated HTML pages
are stored in the current directory, or in the directory specified with the
-d option. You can customize the style of the generated pages by editing the
generated style.css file, or by providing your own style sheet using option
-css-style. The file style.css is not generated if it already exists.
-latex Generate documentation in LaTeX default format. The generated LaTeX
document is saved in file ocamldoc.out, or in the file specified with the -o
option. The document uses the style file ocamldoc.sty. This file is
generated when using the -latex option, if it does not already exist. You
can change this file to customize the style of your LaTeX documentation.
-texi Generate documentation in TeXinfo default format. The generated LaTeX
document is saved in file ocamldoc.out, or in the file specified with the -o
option.
-man Generate documentation as a set of Unix man pages. The generated pages
are stored in the current directory, or in the directory specified with the
-d option.
-dot Generate a dependency graph for the toplevel modules, in a format
suitable for displaying and processing by dot. The dot tool is available
from http://www.research.att.com/sw/tools/graphviz/. The textual
representation of the graph is written to the file ocamldoc.out, or to the
file specified with the -o option. Use dot ocamldoc.out to display it.
-g file.cm[o,a] Dynamically load the given file, which defines a custom
documentation generator. See section 15.4.1. This option is supported by the
ocamldoc command, but not by its native-code version ocamldoc.opt. If the
given file is a simple one and does not exist in the current directory, then
ocamldoc looks for it in the custom generators default directory, and in the
directories specified with optional -i options.
-customdir Display the custom generators default directory.
-i directory Add the given directory to the path where to look for custom
generators.
General options
---------------
-d dir Generate files in directory dir, rather than in the current directory.
-dump file Dump collected information into file. This information can be read
with the -load option in a subsequent invocation of ocamldoc.
-hide modules Hide the given complete module names in the generated
documentation modules is a list of complete module names are separated by
',', without blanks. For instance: Pervasives,M2.M3.
-inv-merge-ml-mli Inverse implementations and interfaces when merging. All
elements in implementation files are kept, and the -m option indicates which
parts of the comments in interface files are merged with the comments in
implementation files.
-keep-code Always keep the source code for values, methods and instance
variables, when available. The source code is always kept when a .ml file is
given, but is by default discarded when a .mli is given. This option allows
to always keep the source code.
-load file Load information from file, which has been produced by ocamldoc
-dump. Several -load options can be given.
-m flags Specify merge options between interfaces and implementations. (see
section 15.1.2 for details). flags can be one or several of the following
characters:
d merge description
a merge @author
v merge @version
l merge @see
s merge @since
o merge @deprecated
p merge @param
e merge @raise
r merge @return
A merge everything
-no-custom-tags Do not allow custom @-tags (see section 15.2.5).
-no-stop Keep elements placed after/between the (**/**) special comment(s)
(see section 15.2).
-o file Output the generated documentation to file instead of ocamldoc.out.
This option is meaningful only in conjunction with the -latex, -texi, or
-dot options.
-pp command Pipe sources through preprocessor command.
-sort Sort the list of top-level modules before generating the documentation.
-stars Remove blank characters until the first asterisk ('*') in each line of
comments.
-t title Use title as the title for the generated documentation.
-intro file Use content of file as ocamldoc text to use as introduction
(HTML, LaTeXand TeXinfo only). For HTML, the file is used to create the
whole index.html file.
-v Verbose mode. Display progress information.
-warn-error Treat warnings as errors.
-hide-warnings Do not print OCamldoc warnings.
Type-checking options
---------------------
OCamldoc calls the Objective Caml type-checker to obtain type informations.
The following options impact the type-checking phase. They have the same
meaning as for the ocamlc and ocamlopt commands.
-I directory Add directory to the list of directories search for compiled
interface files (.cmi files).
-nolabels Ignore non-optional labels in types.
-rectypes Allow arbitrary recursive types. (See the -rectypes option to
ocamlc.)
Options for generating HTML pages
---------------------------------
The following options apply in conjunction with the -html option:
-all-params Display the complete list of parameters for functions and
methods.
-css-style filename Use filename as the Cascading Style Sheet file.
-colorize-code Colorize the OCaml code enclosed in [ ] and \{[ ]\}, using
colors to emphasize keywords, etc. If the code fragments are not
syntactically correct, no color is added.
-index-only Generate only index files.
-short-functors Use a short form to display functors: module M : functor
(A:Module) -> functor (B:Module2) -> sig .. end is displayed as module M
(A:Module) (B:Module2) : sig .. end.
Options for generating LaTeX files
----------------------------------
The following options apply in conjunction with the -latex option:
-latex-value-prefix prefix Give a prefix to use for the labels of the values
in the generated LaTeX document. The default prefix is the empty string. You
can also use the options -latex-type-prefix, -latex-exception-prefix,
-latex-module-prefix, -latex-module-type-prefix, -latex-class-prefix,
-latex-class-type-prefix, -latex-attribute-prefix and -latex-method-prefix.
These options are useful when you have, for example, a type and a value with
the same name. If you do not specify prefixes, LaTeX will complain about
multiply defined labels.
-latextitle n,style Associate style number n to the given LaTeX sectioning
command style, e.g. section or subsection. (LaTeX only.) This is useful when
including the generated document in another LaTeX document, at a given
sectioning level. The default association is 1 for section, 2 for
subsection, 3 for subsubsection, 4 for paragraph and 5 for subparagraph.
-noheader Suppress header in generated documentation.
-notoc Do not generate a table of contents.
-notrailer Suppress trailer in generated documentation.
-sepfiles Generate one .tex file per toplevel module, instead of the global
ocamldoc.out file.
Options for generating TeXinfo files
------------------------------------
The following options apply in conjunction with the -texi option:
-esc8 Escape accented characters in Info files.
-info-entry Specify Info directory entry.
-info-section Specify section of Info directory.
-noheader Suppress header in generated documentation.
-noindex Do not build index for Info files.
-notrailer Suppress trailer in generated documentation.
Options for generating dot graphs
---------------------------------
The following options apply in conjunction with the -dot option:
-dot-colors colors Specify the colors to use in the generated dot code. When
generating module dependencies, ocamldoc uses different colors for modules,
depending on the directories in which they reside. When generating types
dependencies, ocamldoc uses different colors for types, depending on the
modules in which they are defined. colors is a list of color names separated
by ',', as in Red,Blue,Green. The available colors are the ones supported by
the dot tool.
-dot-include-all Include all modules in the dot output, not only modules
given on the command line or loaded with the -load option.
-dot-reduce Perform a transitive reduction of the dependency graph before
outputting the dot code. This can be useful if there are a lot of transitive
dependencies that clutter the graph.
-dot-types Output dot code describing the type dependency graph instead of
the module dependency graph.
Options for generating man files
--------------------------------
The following options apply in conjunction with the -man option:
-man-mini Generate man pages only for modules, module types, clases and class
types, instead of pages for all elements.
-man-suffix Set the suffix used for generated man filenames. Default is 'o',
like in List.o.
15.1.2 Merging of module information
=====================================
Information on a module can be extracted either from the .mli or .ml file, or
both, depending on the files given on the command line. When both .mli and .ml
files are given for the same module, information extracted from these files is
merged according to the following rules:
- Only elements (values, types, classes, ...) declared in the .mli file are
kept. In other terms, definitions from the .ml file that are not exported in
the .mli file are not documented.
- Descriptions of elements and descriptions in @-tags are handled as follows.
If a description for the same element or in the same @-tag of the same
element is present in both files, then the description of the .ml file is
concatenated to the one in the .mli file, if the corresponding -m flag is
given on the command line. If a description is present in the .ml file and
not in the .mli file, the .ml description is kept. In either case, all the
information given in the .mli file is kept.
15.1.3 Coding rules
====================
The following rules must be respected in order to avoid name clashes
resulting in cross-reference errors:
- In a module, there must not be two modules, two module types or a module and
a module type with the same name. In the default HTML generator, modules ab
and AB will be printed to the same file on case insensitive file systems.
- In a module, there must not be two classes, two class types or a class and a
class type with the same name.
- In a module, there must not be two values, two types, or two exceptions with
the same name.
- Values defined in tuple, as in let (x,y,z) = (1,2,3) are not kept by
OCamldoc.
- Avoid the following construction:
<<open Foo (* which has a module Bar with a value x *)
module Foo =
struct
module Bar =
struct
let x = 1
end
end
let dummy = Bar.x
>>
In this case, OCamldoc will associate Bar.x to the x of module Foo defined
just above, instead of to the Bar.x defined in the opened module Foo.
15.2 Syntax of documentation comments
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Comments containing documentation material are called special comments and
are written between (** and *). Special comments must start exactly with (**.
Comments beginning with ( and more than two * are ignored.
15.2.1 Placement of documentation comments
===========================================
OCamldoc can associate comments to some elements of the language encountered
in the source files. The association is made according to the locations of
comments with respect to the language elements. The locations of comments in
.mli and .ml files are different.
Comments in .mli files
----------------------
A special comment is associated to an element if it is placed before or
after the element.
A special comment before an element is associated to this element if :
- There is no blank line or another special comment between the special
comment and the element. However, a regular comment can occur between the
special comment and the element.
- The special comment is not already associated to the previous element.
- The special comment is not the first one of a toplevel module.
A special comment after an element is associated to this element if there is
no blank line or comment between the special comment and the element.
There are two exceptions: for type constructors and record fields in type
definitions, the associated comment can only be placed after the constructor or
field definition, without blank lines or other comments between them. The
special comment for a type constructor with another type constructor following
must be placed before the '|' character separating the two constructors.
The following sample interface file foo.mli illustrates the placement rules
for comments in .mli files.
<<(** The first special comment of the file is the comment associated
with the whole module.*)
(** Special comments can be placed between elements and are kept
by the OCamldoc tool, but are not associated to any element.
@-tags in these comments are ignored.*)
(*******************************************************************)
(** Comments like the one above, with more than two asterisks,
are ignored. *)
(** The comment for function f. *)
val f : int -> int -> int
(** The continuation of the comment for function f. *)
(** Comment for exception My_exception, even with a simple comment
between the special comment and the exception.*)
(* Hello, I'm a simple comment :-) *)
exception My_exception of (int -> int) * int
(** Comment for type weather *)
type weather =
| Rain of int (** The comment for construtor Rain *)
| Sun (** The comment for constructor Sun *)
(** Comment for type weather2 *)
type weather2 =
| Rain of int (** The comment for construtor Rain *)
| Sun (** The comment for constructor Sun *)
(** I can continue the comment for type weather2 here
because there is already a comment associated to the last constructor.*)
(** The comment for type my_record *)
type my_record = {
val foo : int ; (** Comment for field foo *)
val bar : string ; (** Comment for field bar *)
}
(** Continuation of comment for type my_record *)
(** Comment for foo *)
val foo : string
(** This comment is associated to foo and not to bar. *)
val bar : string
(** This comment is assciated to bar. *)
(** The comment for class my_class *)
class my_class :
object
(** A comment to describe inheritance from cl *)
inherit cl
(** The comment for attribute tutu *)
val mutable tutu : string
(** The comment for attribute toto. *)
val toto : int
(** This comment is not attached to titi since
there is a blank line before titi, but is kept
as a comment in the class. *)
val titi : string
(** Comment for method toto *)
method toto : string
(** Comment for method m *)
method m : float -> int
end
(** The comment for the class type my_class_type *)
class type my_class_type =
object
(** The comment for variable x. *)
val mutable x : int
(** The commend for method m. *)
method m : int -> int
end
(** The comment for module Foo *)
module Foo =
struct
(** The comment for x *)
val x : int
(** A special comment that is kept but not associated to any element *)
end
(** The comment for module type my_module_type. *)
module type my_module_type =
sig
(** The comment for value x. *)
val x : int
(** The comment for module M. *)
module M =
struct
(** The comment for value y. *)
val y : int
(* ... *)
end
end
>>
Comments in .ml files
---------------------
A special comment is associated to an element if it is placed before the
element and there is no blank line between the comment and the element.
Meanwhile, there can be a simple comment between the special comment and the
element. There are two exceptions, for type constructors and record fields in
type definitions, whose associated comment must be placed after the constructor
or field definition, without blank line between them. The special comment for a
type constructor with another type constructor following must be placed before
the '|' character separating the two constructors.
The following example of file toto.ml shows where to place comments in a .ml
file.
<<(** The first special comment of the file is the comment associated
to the whole module.*)
(** The comment for function f *)
let f x y = x + y
(** This comment is not attached to any element since there is another
special comment just before the next element. *)
(** Comment for exception My_exception, even with a simple comment
between the special comment and the exception.*)
(* A simple comment. *)
exception My_exception of (int -> int) * int
(** Comment for type weather *)
type weather =
| Rain of int (** The comment for constructor Rain *)
| Sun (** The comment for constructor Sun *)
(** The comment for type my_record *)
type my_record = {
val foo : int ; (** Comment for field foo *)
val bar : string ; (** Comment for field bar *)
}
(** The comment for class my_class *)
class my_class =
object
(** A comment to describe inheritance from cl *)
inherit cl
(** The comment for the instance variable tutu *)
val mutable tutu = "tutu"
(** The comment for toto *)
val toto = 1
val titi = "titi"
(** Comment for method toto *)
method toto = tutu ^ "!"
(** Comment for method m *)
method m (f : float) = 1
end
(** The comment for class type my_class_type *)
class type my_class_type =
object
(** The comment for the instance variable x. *)
val mutable x : int
(** The commend for method m. *)
method m : int -> int
end
(** The comment for module Foo *)
module Foo =
struct
(** The comment for x *)
val x : int
(** A special comment in the class, but not associated to any element. *)
end
(** The comment for module type my_module_type. *)
module type my_module_type =
sig
(* Comment for value x. *)
val x : int
(* ... *)
end
>>
15.2.2 The Stop special comment
================================
The special comment (**/**) tells OCamldoc to discard elements placed after
this comment, up to the end of the current class, class type, module or module
type, or up to the next stop comment. For instance:
<<class type foo =
object
(** comment for method m *)
method m : string
(**/**)
(** This method won't appear in the documentation *)
method bar : int
end
(** This value appears in the documentation, since the Stop special comment
in the class does not affect the parent module of the class.*)
val foo : string
(**/**)
(** The value bar does not appear in the documentation.*)
val bar : string
(**/**)
(** The type t appears since in the documentation since the previous stop
comment
toggled off the "no documentation mode". *)
type t = string
>>
The -no-stop option to ocamldoc causes the Stop special comments to be
ignored.
15.2.3 Syntax of documentation comments
========================================
The inside of documentation comments (**...*) consists of free-form text with
optional formatting annotations, followed by optional tags giving more specific
information about parameters, version, authors, ... The tags are distinguished
by a leading @ character. Thus, a documentation comment has the following
shape:
<<(** The comment begins with a description, which is text formatted
according to the rules described in the next section.
The description continues until the first non-escaped '@' character.
@author Mr Smith
@param x description for parameter x
*)
>>
Some elements support only a subset of all @-tags. Tags that are not relevant
to the documented element are simply ignored. For instance, all tags are
ignored when documenting type constructors, record fields, and class
inheritance clauses. Similarly, a @param tag on a class instance variable is
ignored.
At last, (**) is the empty documentation comment.
15.2.4 Text formatting
=======================
Here is the BNF grammar for the simple markup language used to format text
descriptions.
text ::= (text_element)+
text_element ::=
| {[0-9]+ text} format text as a section
header; the integer
following { indicates the
sectioning level.
| {[0-9]+:label text} same, but also associate
the name label to the
current point. This point
can be referenced by its
fully-qualified label in a
{! command, just like any
other element.
| {b text} set text in bold.
| {i text} set text in italic.
| {e text} emphasize text.
| {C text} center text.
| {L text} left align text.
| {R text} right align text.
| {ul list} build a list.
| {ol list} build an enumerated list.
| {{:string}text} put a link to the given
address (given as a string)
on the given text.
| [string] set the given string in
source code style.
| {[string]} set the given string in
preformatted source code
style.
| {v string v} set the given string in
verbatim style.
| {% string %} take the given string as raw
LaTeX code.
| {!string} insert a reference to the
element named string. string
must be a fully qualified
element name, for example
Foo.Bar.t. The kind of the
referenced element can be
forced (useful when various
elements have the same
qualified name) with the
following syntax: {!kind:
Foo.Bar.t} where kind can be
module, modtype, class,
classtype, val, type,
exception, attribute, method
or section.
| {!modules: string string ...} insert an index table for
the given module names. Used
in HTML only.
| {!indexlist} insert a table of links to
the various indexes (types,
values, modules, ...). Used
in HTML only.
| {^ text} set text in superscript.
| {_ text} set text in subscript.
| escaped_string typeset the given string as
is; special characters ('{',
'}', '[', ']' and '@') must
be escaped by a '\'
| blank_line force a new line.
list ::=
| ({- text})+
| ({li text})+
A shortcut syntax exists for lists and enumerated lists:
<<(** Here is a {b list}
- item 1
- item 2
- item 3
The list is ended by the blank line.*)
>>
is equivalent to:
<<(** Here is a {b list}
{ul {- item 1}
{- item 2}
{- item 3}}
The list is ended by the blank line.*)
>>
The same shortcut is available for enumerated lists, using '+' instead of
'-'. Note that only one list can be defined by this shortcut in nested lists.
In the description of a value, type, exception, module, module type, class or
class type, the first sentence is sometimes used in indexes, or when just a
part of the description is needed. The first sentence is composed of the first
characters of the description, until
- the first dot followed by a blank, or
- the first blank line
outside of the following text formatting : {ul list}, {ol list}, [string],
{[string]}, {v string v}, {% string%}, {!string}, {^ text}, {_ text}.
15.2.5 Documentation tags (@-tags)
===================================
Predefined tags
---------------
The folowing table gives the list of predefined @-tags, with their syntax
and meaning.
---------------------------------------------
|@author string|The author of the element. |
| |One author by @author tag. |
| |There may be several @author|
| |tags for the same element. |
---------------------------------------------
| @deprecated |The text should describe |
|text |when the element was |
| |deprecated, what to use as a|
| |replacement, and possibly |
| |the reason for deprecation. |
---------------------------------------------
| @param id |Associate the given |
|text |description (text) to the |
| |given parameter name id. |
| |This tag is used for |
| |functions, methods, classes |
| |and functors. |
---------------------------------------------
| @raise Exc |Explain that the element may|
|text |raise the exception Exc. |
---------------------------------------------
| @return text |Describe the return value |
| |and its possible values. |
| |This tag is used for |
| |functions and methods. |
---------------------------------------------
| @see <url> |Add a reference to the URL |
|text |between '<' and '>' with the|
| |given text as comment. |
---------------------------------------------
| @see |Add a reference to the given|
|'filename' |file name (written between |
|text |single quotes), with the |
| |given text as comment. |
---------------------------------------------
| @see |Add a reference to the given|
|"document |document name (written |
|name" text |between double quotes), with|
| |the given text as comment. |
---------------------------------------------
| @since string|Indicates when the element |
| |was introduced. |
---------------------------------------------
| @version |The version number for the |
|string |element. |
---------------------------------------------
Custom tags
-----------
You can use custom tags in the documentation comments, but they will have
no effect if the generator used does not handle them. To use a custom tag, for
example foo, just put @foo with some text in your comment, as in:
<<(** My comment to show you a custom tag.
@foo this is the text argument to the [foo] custom tag.
*)
>>
To handle custom tags, you need to define a custom generator, as explained in
section 15.3.2.
15.3 Custom generators
*=*=*=*=*=*=*=*=*=*=*=*
OCamldoc operates in two steps:
1. analysis of the source files;
2. generation of documentation, through a documentation generator, which is
an object of class Odoc_args.class_generator.
Users can provide their own documentation generator to be used during step 2
instead of the default generators. All the information retrieved during the
analysis step is available through the Odoc_info module, which gives access to
all the types and functions representing the elements found in the given
modules, with their associated description.
The files you can used to define custom generators are installed in the
ocamldoc sub-directory of the OCaml standard library.
15.3.1 The generator class
===========================
A generator class is a class of type Odoc_args.doc_generator. It has only
one method
generator : Odoc_info.Module.t_module list -> unit
This method will be called with the list of analysed and possibly merged
Odoc_info.t_module structures. Of course the class can have other methods, but
the object of this class must be coerced to Odoc_args.doc_generator before
being passed to the function
Odoc_args.set_doc_generator : Odoc_args.doc_generator -> unit
which installs the new documentation generator.
The following example shows how to define and install a new documentation
generator. See the odoc_fhtml generator (in the Ocamldoc Hump) for a complete
example.
<<class my_doc_gen =
object
(* ... *)
method generate module_list =
(* ... *)
()
(* ... *)
end
let my_generator = new my_doc_gen
let _ = Odoc_args.set_doc_generator (my_generator :> Odoc_args.doc_generator)
>>
Note: The new class can inherit from Odoc_html.html, Odoc_latex.latex,
Odoc_man.man, Odoc_texi.texi or Odoc_dot.dot, and redefine only some methods to
benefit from the existing methods.
15.3.2 Handling custom tags
============================
Making a custom generator handle custom tags (see 15.2.5) is very simple.
For HTML
--------
Here is how to develop a HTML generator handling your custom tags.
The class Odoc_html.html inherits from the class Odoc_html.info, containing a
field tag_functions which is a list pairs composed of a custom tag (e.g. 'foo')
and a function taking a text and returning HTML code (of type string). To
handle a new tag bar, create a HTML generator class from the existing one and
complete the tag_functions field:
<<class my_gen =
object(self)
inherit Odoc_html.html
(** Return HTML code for the given text of a bar tag. *)
method html_of_bar t = (* your code here *)
initializer
tag_functions <- ("bar", self#html_of_bar) :: tag_functions
end
>>
Another method of the class Odoc_html.info will look for the function
associated to a custom tag and apply it to the text given to the tag. If no
function is associated to a custom tag, then the method prints a warning
message on stderr.
For other generators
--------------------
As for the HTML custom generator, you can define a new LaTeX(resp. man)
generator by inheriting from the class Odoc_latex.latex (resp. Odoc_man.man)
and adding your own tag handler to the field tag_functions.
15.4 Adding command line options
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The command line analysis is performed after loading the module containing
the documentation generator, thus allowing command line options to be added to
the list of existing ones. Adding an option can be done with the function
Odoc_args.add_option : string * Arg.spec * string -> unit
Note: Existing command line options can be redefined using this function.
15.4.1 Compilation and usage
=============================
Defining a custom generator class in one file
---------------------------------------------
Let custom.ml be the file defining a new generator class. Compilation of
custom.ml can be performed by the following command :
ocamlc -I +ocamldoc -c custom.ml
The file custom.cmo is created and can be used this way :
ocamldoc -g custom.cmo other-options source-files
It is important not to give the -html or any other option selecting a built
in generator to ocamldoc, which would result in using this generator instead of
the one you just loaded.
Defining a custom generator class in several files
--------------------------------------------------
It is possible to define a generator class in several modules, which are
defined in several files file1.ml[i], file2.ml[i], ..., fileN.ml[i]. A .cma
library file must be created, including all these files.
The following commands create the custom.cma file from files file1.ml[i],
..., fileN.ml[i] :
ocamlc -I +ocamldoc -c file1.ml[i]
ocamlc -I +ocamldoc -c file2.ml[i]
...
ocamlc -I +ocamldoc -c fileN.ml[i]
ocamlc -o custom.cma -a file1.cmo file2.cmo ... fileN.cmo
Then, the following command uses custom.cma as custom generator:
ocamldoc -g custom.cma other-options source-files
Again, it is important not to give the -html or any other option selecting a
built in generator to ocamldoc, which would result in using this generator
instead of the one you just loaded.
Chapter 16 The debugger (ocamldebug)
***************************************
This chapter describes the Objective Caml source-level replay debugger
ocamldebug.
Unix:
The debugger is available on Unix systems that provide BSD sockets.
Windows:
The debugger is available under the Cygwin port of Objective Caml, but not
under the native Win32 ports.
16.1 Compiling for debugging
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Before the debugger can be used, the program must be compiled and linked with
the -g option: all .cmo and .cma files that are part of the program should have
been created with ocamlc -g, and they must be linked together with ocamlc -g.
Compiling with -g entails no penalty on the running time of programs: object
files and bytecode executable files are bigger and take longer to produce, but
the executable files run at exactly the same speed as if they had been compiled
without -g.
16.2 Invocation
*=*=*=*=*=*=*=*=
16.2.1 Starting the debugger
=============================
The Objective Caml debugger is invoked by running the program ocamldebug with
the name of the bytecode executable file as first argument:
<<
ocamldebug [options] program [arguments]
>>
The arguments following program are optional, and are passed as command-line
arguments to the program being debugged. (See also the set arguments command.)
The following command-line options are recognized:
-I directory Add directory to the list of directories searched for source
files and compiled files. (See also the directory command.)
-s socket Use socket for communicating with the debugged program. See the
description of the command set socket (section 16.8.6) for the format of
socket.
-c count Set the maximum number of simultaneously live checkpoints to count.
-cd directory Run the debugger program from the working directory directory,
instead of the current directory. (See also the cd command.)
-emacs Tell the debugger it is executed under Emacs. (See section 16.10 for
information on how to run the debugger under Emacs.)
-version Print version and exit.
16.2.2 Exiting the debugger
============================
The command quit exits the debugger. You can also exit the debugger by typing
an end-of-file character (usually ctrl-D).
Typing an interrupt character (usually ctrl-C) will not exit the debugger,
but will terminate the action of any debugger command that is in progress and
return to the debugger command level.
16.3 Commands
*=*=*=*=*=*=*=
A debugger command is a single line of input. It starts with a command name,
which is followed by arguments depending on this name. Examples:
<< run
goto 1000
set arguments arg1 arg2
>>
A command name can be truncated as long as there is no ambiguity. For
instance, go 1000 is understood as goto 1000, since there are no other commands
whose name starts with go. For the most frequently used commands, ambiguous
abbreviations are allowed. For instance, r stands for run even though there are
others commands starting with r. You can test the validity of an abbreviation
using the help command.
If the previous command has been successful, a blank line (typing just RET)
will repeat it.
16.3.1 Getting help
====================
The Objective Caml debugger has a simple on-line help system, which gives a
brief description of each command and variable.
help Print the list of commands.
help command Give help about the command command.
help set variable, help show variable Give help about the variable variable.
The list of all debugger variables can be obtained with help set.
help info topic Give help about topic. Use help info to get a list of known
topics.
16.3.2 Accessing the debugger state
====================================
set variable value Set the debugger variable variable to the value value.
show variable Print the value of the debugger variable variable.
info subject Give information about the given subject. For instance, info
breakpoints will print the list of all breakpoints.
16.4 Executing a program
*=*=*=*=*=*=*=*=*=*=*=*=*
16.4.1 Events
==============
Events are "interesting" locations in the source code, corresponding to the
beginning or end of evaluation of "interesting" sub-expressions. Events are the
unit of single-stepping (stepping goes to the next or previous event
encountered in the program execution). Also, breakpoints can only be set at
events. Thus, events play the role of line numbers in debuggers for
conventional languages.
During program execution, a counter is incremented at each event encountered.
The value of this counter is referred as the current time. Thanks to reverse
execution, it is possible to jump back and forth to any time of the execution.
Here is where the debugger events (written §§) are located in the source
code:
- Following a function application:
<<
(f arg)§§
>>
- On entrance to a function:
<<
fun x y z -> §§ ...
>>
- On each case of a pattern-matching definition (function, match...with
construct, try...with construct):
<<
function pat1 -> §§ expr1
| ...
| patN -> §§ exprN
>>
- Between subexpressions of a sequence:
<<
expr1; §§ expr2; §§ ...; §§ exprN
>>
- In the two branches of a conditional expression:
<<
if cond then §§ expr1 else §§ expr2
>>
- At the beginning of each iteration of a loop:
<<
while cond do §§ body done
for i = a to b do §§ body done
>>
Exceptions: A function application followed by a function return is replaced
by the compiler by a jump (tail-call optimization). In this case, no event is
put after the function application.
16.4.2 Starting the debugged program
=====================================
The debugger starts executing the debugged program only when needed. This
allows setting breapoints or assigning debugger variables before execution
starts. There are several ways to start execution:
run Run the program until a breakpoint is hit, or the program terminates.
step 0 Load the program and stop on the first event.
goto time Load the program and execute it until the given time. Useful when
you already know approximately at what time the problem appears. Also useful
to set breakpoints on function values that have not been computed at time 0
(see section 16.5).
The execution of a program is affected by certain information it receives
when the debugger starts it, such as the command-line arguments to the program
and its working directory. The debugger provides commands to specify this
information (set arguments and cd). These commands must be used before program
execution starts. If you try to change the arguments or the working directory
after starting your program, the debugger will kill the program (after asking
for confirmation).
16.4.3 Running the program
===========================
The following commands execute the program forward or backward, starting at
the current time. The execution will stop either when specified by the command
or when a breakpoint is encountered.
run Execute the program forward from current time. Stops at next breakpoint
or when the program terminates.
reverse Execute the program backward from current time. Mostly useful to go
to the last breakpoint encountered before the current time.
step [count] Run the program and stop at the next event. With an argument, do
it count times.
backstep [count] Run the program backward and stop at the previous event.
With an argument, do it count times.
next [count] Run the program and stop at the next event, skipping over
function calls. With an argument, do it count times.
previous [count] Run the program backward and stop at the previous event,
skipping over function calls. With an argument, do it count times.
finish Run the program until the current function returns.
start Run the program backward and stop at the first event before the current
function invocation.
16.4.4 Time travel
===================
You can jump directly to a given time, without stopping on breakpoints, using
the goto command.
As you move through the program, the debugger maintains an history of the
successive times you stop at. The last command can be used to revisit these
times: each last command moves one step back through the history. That is
useful mainly to undo commands such as step and next.
goto time Jump to the given time.
last [count] Go back to the latest time recorded in the execution history.
With an argument, do it count times.
set history size Set the size of the execution history.
16.4.5 Killing the program
===========================
kill Kill the program being executed. This command is mainly useful if you
wish to recompile the program without leaving the debugger.
16.5 Breakpoints
*=*=*=*=*=*=*=*=*
A breakpoint causes the program to stop whenever a certain point in the
program is reached. It can be set in several ways using the break command.
Breakpoints are assigned numbers when set, for further reference. The most
comfortable way to set breakpoints is through the Emacs interface (see section
16.10).
break Set a breakpoint at the current position in the program execution. The
current position must be on an event (i.e., neither at the beginning, nor at
the end of the program).
break function Set a breakpoint at the beginning of function. This works only
when the functional value of the identifier function has been computed and
assigned to the identifier. Hence this command cannot be used at the very
beginning of the program execution, when all identifiers are still
undefined; use goto time to advance execution until the functional value is
available.
break @ [module] line Set a breakpoint in module module (or in the current
module if module is not given), at the first event of line line.
break @ [module] line column Set a breakpoint in module module (or in the
current module if module is not given), at the event closest to line line,
column column.
break @ [module] # character Set a breakpoint in module module at the event
closest to character number character.
break address Set a breakpoint at the code address address.
delete [breakpoint-numbers] Delete the specified breakpoints. Without
argument, all breakpoints are deleted (after asking for confirmation).
info breakpoints Print the list of all breakpoints.
16.6 The call stack
*=*=*=*=*=*=*=*=*=*=
Each time the program performs a function application, it saves the location
of the application (the return address) in a block of data called a stack
frame. The frame also contains the local variables of the caller function. All
the frames are allocated in a region of memory called the call stack. The
command backtrace (or bt) displays parts of the call stack.
At any time, one of the stack frames is "selected" by the debugger; several
debugger commands refer implicitly to the selected frame. In particular,
whenever you ask the debugger for the value of a local variable, the value is
found in the selected frame. The commands frame, up and down select whichever
frame you are interested in.
When the program stops, the debugger automatically selects the currently
executing frame and describes it briefly as the frame command does.
frame Describe the currently selected stack frame.
frame frame-number Select a stack frame by number and describe it. The frame
currently executing when the program stopped has number 0; its caller has
number 1; and so on up the call stack.
backtrace [count], bt [count] Print the call stack. This is useful to see
which sequence of function calls led to the currently executing frame. With
a positive argument, print only the innermost count frames. With a negative
argument, print only the outermost -count frames.
up [count] Select and display the stack frame just "above" the selected
frame, that is, the frame that called the selected frame. An argument says
how many frames to go up.
down [count] Select and display the stack frame just "below" the selected
frame, that is, the frame that was called by the selected frame. An argument
says how many frames to go down.
16.7 Examining variable values
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The debugger can print the current value of simple expressions. The
expressions can involve program variables: all the identifiers that are in
scope at the selected program point can be accessed.
Expressions that can be printed are a subset of Objective Caml expressions,
as described by the following grammar:
simple-expr ::= lowercase-ident
| { capitalized-ident . } lowercase-ident
| *
| $ integer
| simple-expr . lowercase-ident
| simple-expr .( integer )
| simple-expr .[ integer ]
| ! simple-expr
| ( simple-expr )
The first two cases refer to a value identifier, either unqualified or
qualified by the path to the structure that define it. * refers to the result
just computed (typically, the value of a function application), and is valid
only if the selected event is an "after" event (typically, a function
application). $ integer refer to a previously printed value. The remaining four
forms select part of an expression: respectively, a record field, an array
element, a string element, and the current contents of a reference.
print variables Print the values of the given variables. print can be
abbreviated as p.
display variables Same as print, but limit the depth of printing to 1. Useful
to browse large data structures without printing them in full. display can
be abbreviated as d.
When printing a complex expression, a name of the form $integer is
automatically assigned to its value. Such names are also assigned to parts of
the value that cannot be printed because the maximal printing depth is
exceeded. Named values can be printed later on with the commands p $integer or
d $integer. Named values are valid only as long as the program is stopped. They
are forgotten as soon as the program resumes execution.
set print_depth d Limit the printing of values to a maximal depth of d.
set print_length l Limit the printing of values to at most l nodes printed.
16.8 Controlling the debugger
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
16.8.1 Setting the program name and arguments
==============================================
set program file Set the program name to file.
set arguments arguments Give arguments as command-line arguments for the
program.
A shell is used to pass the arguments to the debugged program. You can
therefore use wildcards, shell variables, and file redirections inside the
arguments. To debug programs that read from standard input, it is recommended
to redirect their input from a file (using set arguments < input-file),
otherwise input to the program and input to the debugger are not properly
separated, and inputs are not properly replayed when running the program
backwards.
16.8.2 How programs are loaded
===============================
The loadingmode variable controls how the program is executed.
set loadingmode direct The program is run directly by the debugger. This is
the default mode.
set loadingmode runtime The debugger execute the Objective Caml runtime
ocamlrun on the program. Rarely useful; moreover it prevents the debugging
of programs compiled in "custom runtime" mode.
set loadingmode manual The user starts manually the program, when asked by
the debugger. Allows remote debugging (see section 16.8.6).
16.8.3 Search path for files
=============================
The debugger searches for source files and compiled interface files in a list
of directories, the search path. The search path initially contains the current
directory . and the standard library directory. The directory command adds
directories to the path.
Whenever the search path is modified, the debugger will clear any information
it may have cached about the files.
directory directorynames Add the given directories to the search path. These
directories are added at the front, and will therefore be searched first.
directory Reset the search path. This requires confirmation.
16.8.4 Working directory
=========================
Each time a program is started in the debugger, it inherits its working
directory from the current working directory of the debugger. This working
directory is initially whatever it inherited from its parent process (typically
the shell), but you can specify a new working directory in the debugger with
the cd command or the -cd command-line option.
cd directory Set the working directory for camldebug to directory.
pwd Print the working directory for camldebug.
16.8.5 Turning reverse execution on and off
============================================
In some cases, you may want to turn reverse execution off. This speeds up the
program execution, and is also sometimes useful for interactive programs.
Normally, the debugger takes checkpoints of the program state from time to
time. That is, it makes a copy of the current state of the program (using the
Unix system call fork). If the variable checkpoints is set to off, the debugger
will not take any checkpoints.
set checkpoints on/off Select whether the debugger makes checkpoints or not.
16.8.6 Communication between the debugger and the program
==========================================================
The debugger communicate with the program being debugged through a Unix
socket. You may need to change the socket name, for example if you need to run
the debugger on a machine and your program on another.
set socket socket Use socket for communication with the program. socket can
be either a file name, or an Internet port specification host:port, where
host is a host name or an Internet address in dot notation, and port is a
port number on the host.
On the debugged program side, the socket name is passed through the
CAML_DEBUG_SOCKET environment variable.
16.8.7 Fine-tuning the debugger
================================
Several variables enables to fine-tune the debugger. Reasonable defaults are
provided, and you should normally not have to change them.
set processcount count Set the maximum number of checkpoints to count. More
checkpoints facilitate going far back in time, but use more memory and
create more Unix processes.
As checkpointing is quite expensive, it must not be done too often. On the
other hand, backward execution is faster when checkpoints are taken more often.
In particular, backward single-stepping is more responsive when many
checkpoints have been taken just before the current time. To fine-tune the
checkpointing strategy, the debugger does not take checkpoints at the same
frequency for long displacements (e.g. run) and small ones (e.g. step). The two
variables bigstep and smallstep contain the number of events between two
checkpoints in each case.
set bigstep count Set the number of events between two checkpoints for long
displacements.
set smallstep count Set the number of events between two checkpoints for
small displacements.
The following commands display information on checkpoints and events:
info checkpoints Print a list of checkpoints.
info events [module] Print the list of events in the given module (the
current module, by default).
16.8.8 User-defined printers
=============================
Just as in the toplevel system (section 9.2), the user can register functions
for printing values of certain types. For technical reasons, the debugger
cannot call printing functions that reside in the program being debugged. The
code for the printing functions must therefore be loaded explicitly in the
debugger.
load_printer "file-name" Load in the debugger the indicated .cmo or .cma
object file. The file is loaded in an environment consisting only of the
Objective Caml standard library plus the definitions provided by object
files previously loaded using load_printer. If this file depends on other
object files not yet loaded, the debugger automatically loads them if it is
able to find them in the search path. The loaded file does not have direct
access to the modules of the program being debugged.
install_printer printer-name Register the function named printer-name (a
value path) as a printer for objects whose types match the argument type of
the function. That is, the debugger will call printer-name when it has such
an object to print. The printing function printer-name must use the Format
library module to produce its output, otherwise its output will not be
correctly located in the values printed by the toplevel loop.
The value path printer-name must refer to one of the functions defined by the
object files loaded using load_printer. It cannot reference the functions of
the program being debugged.
remove_printer printer-name Remove the named function from the table of value
printers.
16.9 Miscellaneous commands
*=*=*=*=*=*=*=*=*=*=*=*=*=*=
list [module] [beginning] [end] List the source of module module, from line
number beginning to line number end. By default, 20 lines of the current
module are displayed, starting 10 lines before the current position.
source filename Read debugger commands from the script filename.
16.10 Running the debugger under Emacs
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The most user-friendly way to use the debugger is to run it under Emacs. See
the file emacs/README in the distribution for information on how to load the
Emacs Lisp files for Caml support.
The Caml debugger is started under Emacs by the command M-x camldebug, with
argument the name of the executable file progname to debug. Communication with
the debugger takes place in an Emacs buffer named *camldebug-progname*. The
editing and history facilities of Shell mode are available for interacting with
the debugger.
In addition, Emacs displays the source files containing the current event
(the current position in the program execution) and highlights the location of
the event. This display is updated synchronously with the debugger action.
The following bindings for the most common debugger commands are available in
the *camldebug-progname* buffer:
C-c C-s (command step): execute the program one step forward.
C-c C-k (command backstep): execute the program one step backward.
C-c C-n (command next): execute the program one step forward, skipping over
function calls.
Middle mouse button (command display): display named value. $n under mouse
cursor (support incremental browsing of large data structures).
C-c C-p (command print): print value of identifier at point.
C-c C-d (command display): display value of identifier at point.
C-c C-r (command run): execute the program forward to next breakpoint.
C-c C-v (command reverse): execute the program backward to latest breakpoint.
C-c C-l (command last): go back one step in the command history.
C-c C-t (command backtrace): display backtrace of function calls.
C-c C-f (command finish): run forward till the current function returns.
C-c < (command up): select the stack frame below the current frame.
C-c > (command down): select the stack frame above the current frame.
In all buffers in Caml editing mode, the following debugger commands are also
available:
C-x C-a C-b (command break): set a breakpoint at event closest to point
C-x C-a C-p (command print): print value of identifier at point
C-x C-a C-d (command display): display value of identifier at point
Chapter 17 Profiling (ocamlprof)
***********************************
This chapter describes how the execution of Objective Caml programs can be
profiled, by recording how many times functions are called, branches of
conditionals are taken, ...
17.1 Compiling for profiling
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Before profiling an execution, the program must be compiled in profiling
mode, using the ocamlcp front-end to the ocamlc compiler (see chapter 8). When
compiling modules separately, ocamlcp must be used when compiling the modules
(production of .cmo files), and can also be used (though this is not strictly
necessary) when linking them together.
Note
If a module (.ml file) doesn't have a corresponding interface (.mli file),
then compiling it with ocamlcp will produce object files (.cmi and .cmo) that
are not compatible with the ones produced by ocamlc, which may lead to problems
(if the .cmi or .cmo is still around) when switching between profiling and
non-profiling compilations. To avoid this problem, you should always have a
.mli file for each .ml file.
Note
To make sure your programs can be compiled in profiling mode, avoid using
any identifier that begins with __ocaml_prof.
The amount of profiling information can be controlled through the -p option
to ocamlcp, followed by one or several letters indicating which parts of the
program should be profiled:
a all options
f function calls : a count point is set at the beginning of function bodies
i if ...then ...else ... : count points are set in both then branch and else
branch
l while, for loops: a count point is set at the beginning of the loop body
m match branches: a count point is set at the beginning of the body of each
branch
t try ...with ... branches: a count point is set at the beginning of the body
of each branch
For instance, compiling with ocamlcp -p film profiles function calls,
if...then...else..., loops and pattern matching.
Calling ocamlcp without the -p option defaults to -p fm, meaning that only
function calls and pattern matching are profiled.
Note: Due to the implementation of streams and stream patterns as syntactic
sugar, it is hard to predict what parts of stream expressions and patterns will
be profiled by a given flag. To profile a program with streams, we recommend
using ocamlcp -p a.
17.2 Profiling an execution
*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Running a bytecode executable file that has been compiled with ocamlcp
records the execution counts for the specified parts of the program and saves
them in a file called ocamlprof.dump in the current directory.
If the environment variable OCAMLPROF_DUMP is set when the program exits, its
value is used as the file name instead of ocamlprof.dump.
The dump file is written only if the program terminates normally (by calling
exit or by falling through). It is not written if the program terminates with
an uncaught exception.
If a compatible dump file already exists in the current directory, then the
profiling information is accumulated in this dump file. This allows, for
instance, the profiling of several executions of a program on different inputs.
17.3 Printing profiling information
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
The ocamlprof command produces a source listing of the program modules where
execution counts have been inserted as comments. For instance,
<< ocamlprof foo.ml
>>
prints the source code for the foo module, with comments indicating how many
times the functions in this module have been called. Naturally, this
information is accurate only if the source file has not been modified since the
profiling execution took place.
The following options are recognized by ocamlprof:
-f dumpfile Specifies an alternate dump file of profiling information to be
read.
-F string Specifies an additional string to be output with profiling
information. By default, ocamlprof will annotate programs with comments of
the form (* n *) where n is the counter value for a profiling point. With
option -F s, the annotation will be (* sn *).
-impl sourcefile Treat sourcefile as an implementation file (i.e. as if its
name ended with .ml).
-intf sourcefile Treat sourcefile as an interface file (i.e. as if its name
ended with .mli).
-version Print the version number of ocamlprof and exit.
-instrument
-m flags These options are undocumented; they are used internally by ocamlcp.
17.4 Time profiling
*=*=*=*=*=*=*=*=*=*=
Profiling with ocamlprof only records execution counts, not the actual time
spent into each function. There is currently no way to perform time profiling
on bytecode programs generated by ocamlc.
Native-code programs generated by ocamlopt can be profiled for time and
execution counts using the -p option and the standard Unix profiler gprof. Just
add the -p option when compiling and linking the program:
<<
ocamlopt -o myprog -p other-options files
./myprog
gprof myprog
>>
Caml function names in the output of gprof have the following format:
<<
Module-name_function-name_unique-number
>>
Other functions shown are either parts of the Caml run-time system or
external C functions linked with the program.
The output of gprof is described in the Unix manual page for gprof(1). It
generally consists of two parts: a "flat" profile showing the time spent in
each function and the number of invocation of each function, and a
"hierarchical" profile based on the call graph. Currently, only the Intel
x86/Linux and Alpha/Digital Unix ports of ocamlopt support the two profiles. On
other platforms, gprof will report only the "flat" profile with just time
information. When reading the output of gprof, keep in mind that the
accumulated times computed by gprof are based on heuristics and may not be
exact.
Chapter 18 Interfacing C with Objective Caml
***********************************************
This chapter describes how user-defined primitives, written in C, can be
linked with Caml code and called from Caml functions.
18.1 Overview and compilation information
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
18.1.1 Declaring primitives
============================
User primitives are declared in an implementation file or struct...end
module expression using the external keyword:
<<
external name : type = C-function-name
>>
This defines the value name name as a function with type type that executes
by calling the given C function. For instance, here is how the input primitive
is declared in the standard library module Pervasives:
<< external input : in_channel -> string -> int -> int -> int
= "input"
>>
Primitives with several arguments are always curried. The C function does not
necessarily have the same name as the ML function.
External functions thus defined can be specified in interface files or
sig...end signatures either as regular values
<<
val name : type
>>
thus hiding their implementation as a C function, or explicitly as
"manifest" external functions
<<
external name : type = C-function-name
>>
The latter is slightly more efficient, as it allows clients of the module to
call directly the C function instead of going through the corresponding Caml
function.
The arity (number of arguments) of a primitive is automatically determined
from its Caml type in the external declaration, by counting the number of
function arrows in the type. For instance, input above has arity 4, and the
input C function is called with four arguments. Similarly,
<< external input2 : in_channel * string * int * int -> int = "input2"
>>
has arity 1, and the input2 C function receives one argument (which is a
quadruple of Caml values).
Type abbreviations are not expanded when determining the arity of a
primitive. For instance,
<< type int_endo = int -> int
external f : int_endo -> int_endo = "f"
external g : (int -> int) -> (int -> int) = "f"
>>
f has arity 1, but g has arity 2. This allows a primitive to return a
functional value (as in the f example above): just remember to name the
functional return type in a type abbreviation.
18.1.2 Implementing primitives
===============================
User primitives with arity n <= 5 are implemented by C functions that take n
arguments of type value, and return a result of type value. The type value is
the type of the representations for Caml values. It encodes objects of several
base types (integers, floating-point numbers, strings, ...), as well as Caml
data structures. The type value and the associated conversion functions and
macros are described in details below. For instance, here is the declaration
for the C function implementing the input primitive:
<<CAMLprim value input(value channel, value buffer, value offset, value length)
{
...
}
>>
When the primitive function is applied in a Caml program, the C function is
called with the values of the expressions to which the primitive is applied as
arguments. The value returned by the function is passed back to the Caml
program as the result of the function application.
User primitives with arity greater than 5 should be implemented by two C
functions. The first function, to be used in conjunction with the bytecode
compiler ocamlc, receives two arguments: a pointer to an array of Caml values
(the values for the arguments), and an integer which is the number of arguments
provided. The other function, to be used in conjunction with the native-code
compiler ocamlopt, takes its arguments directly. For instance, here are the two
C functions for the 7-argument primitive Nat.add_nat:
<<CAMLprim value add_nat_native(value nat1, value ofs1, value len1,
value nat2, value ofs2, value len2,
value carry_in)
{
...
}
CAMLprim value add_nat_bytecode(value * argv, int argn)
{
return add_nat_native(argv[0], argv[1], argv[2], argv[3],
argv[4], argv[5], argv[6]);
}
>>
The names of the two C functions must be given in the primitive declaration,
as follows:
<<
external name : type =
bytecode-C-function-name native-code-C-function-name
>>
For instance, in the case of add_nat, the declaration is:
<< external add_nat: nat -> int -> int -> nat -> int -> int -> int ->
int
= "add_nat_bytecode" "add_nat_native"
>>
Implementing a user primitive is actually two separate tasks: on the one
hand, decoding the arguments to extract C values from the given Caml values,
and encoding the return value as a Caml value; on the other hand, actually
computing the result from the arguments. Except for very simple primitives, it
is often preferable to have two distinct C functions to implement these two
tasks. The first function actually implements the primitive, taking native C
values as arguments and returning a native C value. The second function, often
called the "stub code", is a simple wrapper around the first function that
converts its arguments from Caml values to C values, call the first function,
and convert the returned C value to Caml value. For instance, here is the stub
code for the input primitive:
<<CAMLprim value input(value channel, value buffer, value offset, value length)
{
return Val_long(getblock((struct channel *) channel,
&Byte(buffer, Long_val(offset)),
Long_val(length)));
}
>>
(Here, Val_long, Long_val and so on are conversion macros for the type value,
that will be described later. The CAMLprim macro expands to the required
compiler directives to ensure that the function following it is exported and
accessible from Caml.) The hard work is performed by the function getblock,
which is declared as:
<<long getblock(struct channel * channel, char * p, long n)
{
...
}
>>
To write C code that operates on Objective Caml values, the following include
files are provided:
-----------------------------------------------------
| Include file | Provides |
-----------------------------------------------------
| caml/mlvalues.h|definition of the value type, and |
| |conversion macros |
|caml/alloc.h |allocation functions (to create |
| |structured Caml objects) |
|caml/memory.h |miscellaneous memory-related |
| |functions and macros (for GC |
| |interface, in-place modification |
| |of structures, etc). |
|caml/fail.h |functions for raising exceptions |
| |(see section 18.4.5) |
|caml/callback.h |callback from C to Caml (see |
| |section 18.7). |
|caml/custom.h |operations on custom blocks (see |
| |section 18.9). |
|caml/intext.h |operations for writing |
| |user-defined serialization and |
| |deserialization functions for |
| |custom blocks (see section 18.9). |
-----------------------------------------------------
These files reside in the caml/ subdirectory of the Objective Caml standard
library directory (usually /usr/local/lib/ocaml).
18.1.3 Statically linking C code with Caml code
================================================
The Objective Caml runtime system comprises three main parts: the bytecode
interpreter, the memory manager, and a set of C functions that implement the
primitive operations. Some bytecode instructions are provided to call these C
functions, designated by their offset in a table of functions (the table of
primitives).
In the default mode, the Caml linker produces bytecode for the standard
runtime system, with a standard set of primitives. References to primitives
that are not in this standard set result in the "unavailable C primitive"
error. (Unless dynamic loading of C libraries is supported -- see section
18.1.4 below.)
In the "custom runtime" mode, the Caml linker scans the object files and
determines the set of required primitives. Then, it builds a suitable runtime
system, by calling the native code linker with:
- the table of the required primitives;
- a library that provides the bytecode interpreter, the memory manager, and
the standard primitives;
- libraries and object code files (.o files) mentioned on the command line for
the Caml linker, that provide implementations for the user's primitives.
This builds a runtime system with the required primitives. The Caml linker
generates bytecode for this custom runtime system. The bytecode is appended to
the end of the custom runtime system, so that it will be automatically executed
when the output file (custom runtime + bytecode) is launched.
To link in "custom runtime" mode, execute the ocamlc command with:
- the -custom option;
- the names of the desired Caml object files (.cmo and .cma files) ;
- the names of the C object files and libraries (.o and .a files) that
implement the required primitives. Under Unix and Windows, a library named
libname.a residing in one of the standard library directories can also be
specified as -cclib -lname.
If you are using the native-code compiler ocamlopt, the -custom flag is not
needed, as the final linking phase of ocamlopt always builds a standalone
executable. To build a mixed Caml/C executable, execute the ocamlopt command
with:
- the names of the desired Caml native object files (.cmx and .cmxa files);
- the names of the C object files and libraries (.o, .a, .so or .dll files)
that implement the required primitives.
Starting with OCaml 3.00, it is possible to record the -custom option as well
as the names of C libraries in a Caml library file .cma or .cmxa. For instance,
consider a Caml library mylib.cma, built from the Caml object files a.cmo and
b.cmo, which reference C code in libmylib.a. If the library is built as
follows:
<<
ocamlc -a -o mylib.cma -custom a.cmo b.cmo -cclib -lmylib
>>
users of the library can simply link with mylib.cma:
<<
ocamlc -o myprog mylib.cma ...
>>
and the system will automatically add the -custom and -cclib -lmylib
options, achieving the same effect as
<<
ocamlc -o myprog -custom a.cmo b.cmo ... -cclib -lmylib
>>
The alternative, of course, is to build the library without extra options:
<<
ocamlc -a -o mylib.cma a.cmo b.cmo
>>
and then ask users to provide the -custom and -cclib -lmylib options
themselves at link-time:
<<
ocamlc -o myprog -custom mylib.cma ... -cclib -lmylib
>>
The former alternative is more convenient for the final users of the
library, however.
18.1.4 Dynamically linking C code with Caml code
=================================================
Starting with OCaml 3.03, an alternative to static linking of C code using
the -custom code is provided. In this mode, the Caml linker generates a pure
bytecode executable (no embedded custom runtime system) that simply records the
names of dynamically-loaded libraries containing the C code. The standard Caml
runtime system ocamlrun then loads dynamically these libraries, and resolves
references to the required primitives, before executing the bytecode.
This facility is currently supported and known to work well under Linux,
MacOS X, and Windows (the native Windows port). It is supported, but not fully
tested yet, under FreeBSD, Tru64, Solaris and Irix. It is not supported yet
under other Unixes and under Cygwin for Windows.
To dynamically link C code with Caml code, the C code must first be compiled
into a shared library (under Unix) or DLL (under Windows). This involves 1-
compiling the C files with appropriate C compiler flags for producing
position-independent code, and 2- building a shared library from the resulting
object files. The resulting shared library or DLL file must be installed in a
place where ocamlrun can find it later at program start-up time (see section
10.3). Finally (step 3), execute the ocamlc command with
- the names of the desired Caml object files (.cmo and .cma files) ;
- the names of the C shared libraries (.so or .dll files) that implement the
required primitives. Under Unix and Windows, a library named dllname.so
(respectively, .dll) residing in one of the standard library directories can
also be specified as -dllib -lname.
Do not set the -custom flag, otherwise you're back to static linking as
described in section 18.1.3. Under Unix, the ocamlmklib tool (see section
18.10) automates steps 2 and 3.
As in the case of static linking, it is possible (and recommended) to record
the names of C libraries in a Caml .cmo library archive. Consider again a Caml
library mylib.cma, built from the Caml object files a.cmo and b.cmo, which
reference C code in dllmylib.so. If the library is built as follows:
<<
ocamlc -a -o mylib.cma a.cmo b.cmo -dllib -lmylib
>>
users of the library can simply link with mylib.cma:
<<
ocamlc -o myprog mylib.cma ...
>>
and the system will automatically add the -dllib -lmylib option, achieving
the same effect as
<<
ocamlc -o myprog a.cmo b.cmo ... -dllib -lmylib
>>
Using this mechanism, users of the library mylib.cma do not need to known
that it references C code, nor whether this C code must be statically linked
(using -custom) or dynamically linked.
18.1.5 Choosing between static linking and dynamic linking
===========================================================
After having described two different ways of linking C code with Caml code,
we now review the pros and cons of each, to help developers of mixed Caml/C
libraries decide.
The main advantage of dynamic linking is that it preserves the
platform-independence of bytecode executables. That is, the bytecode executable
contains no machine code, and can therefore be compiled on platform A and
executed on other platforms B, C, ..., as long as the required shared libraries
are available on all these platforms. In contrast, executables generated by
ocamlc -custom run only on the platform on which they were created, because
they embark a custom-tailored runtime system specific to that platform. In
addition, dynamic linking results in smaller executables.
Another advantage of dynamic linking is that the final users of the library
do not need to have a C compiler, C linker, and C runtime libraries installed
on their machines. This is no big deal under Unix and Cygwin, but many Windows
users are reluctant to install Microsoft Visual C just to be able to do ocamlc
-custom.
There are two drawbacks to dynamic linking. The first is that the resulting
executable is not stand-alone: it requires the shared libraries, as well as
ocamlrun, to be installed on the machine executing the code. If you wish to
distribute a stand-alone executable, it is better to link it statically, using
ocamlc -custom -ccopt -static or ocamlopt -ccopt -static. Dynamic linking also
raises the "DLL hell" problem: some care must be taken to ensure that the right
versions of the shared libraries are found at start-up time.
The second drawback of dynamic linking is that it complicates the
construction of the library. The C compiler and linker flags to compile to
position-independent code and build a shared library vary wildly between
different Unix systems. Also, dynamic linking is not supported on all Unix
systems, requiring a fall-back case to static linking in the Makefile for the
library. The ocamlmklib command (see section 18.10) tries to hide some of these
system dependencies.
In conclusion: dynamic linking is highly recommended under the native Windows
port, because there are no portability problems and it is much more convenient
for the end users. Under Unix, dynamic linking should be considered for mature,
frequently used libraries because it enhances platform-independence of bytecode
executables. For new or rarely-used libraries, static linking is much simpler
to set up in a portable way.
18.1.6 Building standalone custom runtime systems
==================================================
It is sometimes inconvenient to build a custom runtime system each time Caml
code is linked with C libraries, like ocamlc -custom does. For one thing, the
building of the runtime system is slow on some systems (that have bad linkers
or slow remote file systems); for another thing, the platform-independence of
bytecode files is lost, forcing to perform one ocamlc -custom link per platform
of interest.
An alternative to ocamlc -custom is to build separately a custom runtime
system integrating the desired C libraries, then generate "pure" bytecode
executables (not containing their own runtime system) that can run on this
custom runtime. This is achieved by the -make_runtime and -use_runtime flags to
ocamlc. For example, to build a custom runtime system integrating the C parts
of the "Unix" and "Threads" libraries, do:
<< ocamlc -make-runtime -o /home/me/ocamlunixrun unix.cma threads.cma
>>
To generate a bytecode executable that runs on this runtime system, do:
<<
ocamlc -use-runtime /home/me/ocamlunixrun -o myprog \
unix.cma threads.cma your .cmo and .cma files
>>
The bytecode executable myprog can then be launched as usual: myprog args or
/home/me/ocamlunixrun myprog args.
Notice that the bytecode libraries unix.cma and threads.cma must be given
twice: when building the runtime system (so that ocamlc knows which C
primitives are required) and also when building the bytecode executable (so
that the bytecode from unix.cma and threads.cma is actually linked in).
18.2 The value type
*=*=*=*=*=*=*=*=*=*=
All Caml objects are represented by the C type value, defined in the include
file caml/mlvalues.h, along with macros to manipulate values of that type. An
object of type value is either:
- an unboxed integer;
- a pointer to a block inside the heap (such as the blocks allocated through
one of the `caml_alloc_*' functions below);
- a pointer to an object outside the heap (e.g., a pointer to a block
allocated by malloc, or to a C variable).
18.2.1 Integer values
======================
Integer values encode 31-bit signed integers (63-bit on 64-bit
architectures). They are unboxed (unallocated).
18.2.2 Blocks
==============
Blocks in the heap are garbage-collected, and therefore have strict structure
constraints. Each block includes a header containing the size of the block (in
words), and the tag of the block. The tag governs how the contents of the
blocks are structured. A tag lower than No_scan_tag indicates a structured
block, containing well-formed values, which is recursively traversed by the
garbage collector. A tag greater than or equal to No_scan_tag indicates a raw
block, whose contents are not scanned by the garbage collector. For the
benefits of ad-hoc polymorphic primitives such as equality and structured
input-output, structured and raw blocks are further classified according to
their tags as follows:
--------------------------------------------------
| Tag | Contents of the block |
--------------------------------------------------
| 0 to No_scan_tag-1|A structured block (an array|
| |of Caml objects). Each field|
| |is a value. |
|Closure_tag |A closure representing a |
| |functional value. The first |
| |word is a pointer to a piece|
| |of code, the remaining words|
| |are value containing the |
| |environment. |
|String_tag |A character string. |
|Double_tag |A double-precision |
| |floating-point number. |
|Double_array_tag |An array or record of |
| |double-precision |
| |floating-point numbers. |
|Abstract_tag |A block representing an |
| |abstract datatype. |
|Custom_tag |A block representing an |
| |abstract datatype with |
| |user-defined finalization, |
| |comparison, hashing, |
| |serialization and |
| |deserialization functions |
| |atttached. |
--------------------------------------------------
18.2.3 Pointers outside the heap
=================================
Any word-aligned pointer to an address outside the heap can be safely cast to
and from the type value. This includes pointers returned by malloc, and
pointers to C variables (of size at least one word) obtained with the `&'
operator.
Caution: if a pointer returned by malloc is cast to the type value and
returned to Caml, explicit deallocation of the pointer using free is
potentially dangerous, because the pointer may still be accessible from the
Caml world. Worse, the memory space deallocated by free can later be
reallocated as part of the Caml heap; the pointer, formerly pointing outside
the Caml heap, now points inside the Caml heap, and this can confuse the
garbage collector. To avoid these problems, it is preferable to wrap the
pointer in a Caml block with tag Abstract_tag or Custom_tag.
18.3 Representation of Caml data types
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This section describes how Caml data types are encoded in the value type.
18.3.1 Atomic types
====================
------------------------------------------------
|Caml type| Encoding |
------------------------------------------------
| int |Unboxed integer values. |
|char |Unboxed integer values (ASCII code).|
|float |Blocks with tag Double_tag. |
|string |Blocks with tag String_tag. |
|int32 |Blocks with tag Custom_tag. |
|int64 |Blocks with tag Custom_tag. |
|nativeint|Blocks with tag Custom_tag. |
------------------------------------------------
18.3.2 Tuples and records
==========================
Tuples are represented by pointers to blocks, with tag 0.
Records are also represented by zero-tagged blocks. The ordering of labels in
the record type declaration determines the layout of the record fields: the
value associated to the label declared first is stored in field 0 of the block,
the value associated to the label declared next goes in field 1, and so on.
As an optimization, records whose fields all have static type float are
represented as arrays of floating-point numbers, with tag Double_array_tag.
(See the section below on arrays.)
18.3.3 Arrays
==============
Arrays of integers and pointers are represented like tuples, that is, as
pointers to blocks tagged 0. They are accessed with the Field macro for reading
and the modify function for writing.
Arrays of floating-point numbers (type float array) have a special, unboxed,
more efficient representation. These arrays are represented by pointers to
blocks with tag Double_array_tag. They should be accessed with the Double_field
and Store_double_field macros.
18.3.4 Concrete types
======================
Constructed terms are represented either by unboxed integers (for constant
constructors) or by blocks whose tag encode the constructor (for non-constant
constructors). The constant constructors and the non-constant constructors for
a given concrete type are numbered separately, starting from 0, in the order in
which they appear in the concrete type declaration. Constant constructors are
represented by unboxed integers equal to the constructor number. Non-constant
constructors declared with a n-tuple as argument are represented by a block of
size n, tagged with the constructor number; the n fields contain the components
of its tuple argument. Other non-constant constructors are represented by a
block of size 1, tagged with the constructor number; the field 0 contains the
value of the constructor argument. Example:
------------------------------------------
|Constructed term| Representation |
------------------------------------------
| () |Val_int(0) |
|false |Val_int(0) |
|true |Val_int(1) |
|[] |Val_int(0) |
|h::t |Block with size = 2 and|
| |tag = 0; first field |
| |contains h, second |
| |field t |
------------------------------------------
As a convenience, caml/mlvalues.h defines the macros Val_unit, Val_false and
Val_true to refer to (), false and true.
18.3.5 Objects
===============
Objects are represented as blocks with tag Object_tag. The first field of the
block refers to the object class and associated method suite, in a format that
cannot easily be exploited from C. The second field contains a unique object
ID, used for comparisons. The remaining fields of the object contain the values
of the instance variables of the object. It is unsafe to access directly
instance variables, as the type system provides no guaranteee about the
instance variables contained by an object.
One may extract a public method from an object using the C function
caml_get_public_method (declared in <caml/mlvalues.h>.) Since public method
tags are hashed in the same way as variant tags, and methods are functions
taking self as first argument, if you want to do the method call foo#bar from
the C side, you should call:
<< callback(caml_get_public_method(foo, hash_variant("bar")), foo);
>>
18.3.6 Variants
================
Like constructed terms, values of variant types are represented either as
integers (for variants without arguments), or as blocks (for variants with an
argument). Unlike constructed terms, variant constructors are not numbered
starting from 0, but identified by a hash value (a Caml integer), as computed
by the C function hash_variant (declared in <caml/mlvalues.h>): the hash value
for a variant constructor named, say, VConstr is hash_variant("VConstr").
The variant value `VConstr is represented by hash_variant("VConstr"). The
variant value `VConstr(v) is represented by a block of size 2 and tag 0, with
field number 0 containing hash_variant("VConstr") and field number 1 containing
v.
Unlike constructed values, variant values taking several arguments are not
flattened. That is, `VConstr(v, v') is represented by a block of size 2, whose
field number 1 contains the representation of the pair (v, v'), rather than a
block of size 3 containing v and v' in fields 1 and 2.
18.4 Operations on values
*=*=*=*=*=*=*=*=*=*=*=*=*=
18.4.1 Kind tests
==================
- Is_long(v) is true if value v is an immediate integer, false otherwise
- Is_block(v) is true if value v is a pointer to a block, and false if it is
an immediate integer.
18.4.2 Operations on integers
==============================
- Val_long(l) returns the value encoding the long int l.
- Long_val(v) returns the long int encoded in value v.
- Val_int(i) returns the value encoding the int i.
- Int_val(v) returns the int encoded in value v.
- Val_bool(x) returns the Caml boolean representing the truth value of the C
integer x.
- Bool_val(v) returns 0 if v is the Caml boolean false, 1 if v is true.
- Val_true, Val_false represent the Caml booleans true and false.
18.4.3 Accessing blocks
========================
- Wosize_val(v) returns the size of the block v, in words, excluding the
header.
- Tag_val(v) returns the tag of the block v.
- Field(v, n) returns the value contained in the n^th field of the structured
block v. Fields are numbered from 0 to Wosize_val(v)-1.
- Store_field(b, n, v) stores the value v in the field number n of value b,
which must be a structured block.
- Code_val(v) returns the code part of the closure v.
- string_length(v) returns the length (number of characters) of the string v.
- Byte(v, n) returns the n^th character of the string v, with type char.
Characters are numbered from 0 to string_length(v)-1.
- Byte_u(v, n) returns the n^th character of the string v, with type unsigned
char. Characters are numbered from 0 to string_length(v)-1.
- String_val(v) returns a pointer to the first byte of the string v, with type
char *. This pointer is a valid C string: there is a null character after
the last character in the string. However, Caml strings can contain embedded
null characters, that will confuse the usual C functions over strings.
- Double_val(v) returns the floating-point number contained in value v, with
type double.
- Double_field(v, n) returns the n^th element of the array of floating-point
numbers v (a block tagged Double_array_tag).
- Store_double_field(v, n, d) stores the double precision floating-point
number d in the n^th element of the array of floating-point numbers v.
- Data_custom_val(v) returns a pointer to the data part of the custom block v.
This pointer has type void * and must be cast to the type of the data
contained in the custom block.
- Int32_val(v) returns the 32-bit integer contained in the int32 v.
- Int64_val(v) returns the 64-bit integer contained in the int64 v.
- Nativeint_val(v) returns the long integer contained in the nativeint v.
The expressions Field(v, n), Byte(v, n) and Byte_u(v, n) are valid l-values.
Hence, they can be assigned to, resulting in an in-place modification of value
v. Assigning directly to Field(v, n) must be done with care to avoid confusing
the garbage collector (see below).
18.4.4 Allocating blocks
=========================
Simple interface
----------------
- Atom(t) returns an "atom" (zero-sized block) with tag t. Zero-sized blocks
are preallocated outside of the heap. It is incorrect to try and allocate a
zero-sized block using the functions below. For instance, Atom(0) represents
the empty array.
- caml_alloc(n, t) returns a fresh block of size n with tag t. If t is less
than No_scan_tag, then the fields of the block are initialized with a valid
value in order to satisfy the GC constraints.
- caml_alloc_tuple(n) returns a fresh block of size n words, with tag 0.
- caml_alloc_string(n) returns a string value of length n characters. The
string initially contains garbage.
- caml_copy_string(s) returns a string value containing a copy of the
null-terminated C string s (a char *).
- caml_copy_double(d) returns a floating-point value initialized with the
double d.
- caml_copy_int32(i), copy_int64(i) and caml_copy_nativeint(i) return a value
of Caml type int32, int64 and nativeint, respectively, initialized with the
integer i.
- caml_alloc_array(f, a) allocates an array of values, calling function f over
each element of the input array a to transform it into a value. The array a
is an array of pointers terminated by the null pointer. The function f
receives each pointer as argument, and returns a value. The zero-tagged
block returned by alloc_array(f, a) is filled with the values returned by
the successive calls to f. (This function must not be used to build an array
of floating-point numbers.)
- caml_copy_string_array(p) allocates an array of strings, copied from the
pointer to a string array p (a `char **'). p must be NULL-terminated.
Low-level interface
-------------------
The following functions are slightly more efficient than caml_alloc, but also
much more difficult to use.
From the standpoint of the allocation functions, blocks are divided according
to their size as zero-sized blocks, small blocks (with size less than or equal
to `Max_young_wosize'), and large blocks (with size greater than
`Max_young_wosize'). The constant `Max_young_wosize' is declared in the include
file mlvalues.h. It is guaranteed to be at least 64 (words), so that any block
with constant size less than or equal to 64 can be assumed to be small. For
blocks whose size is computed at run-time, the size must be compared against
`Max_young_wosize' to determine the correct allocation procedure.
- caml_alloc_small(n, t) returns a fresh small block of size n <=
Max_young_wosize words, with tag t. If this block is a structured block
(i.e. if t < No_scan_tag), then the fields of the block (initially
containing garbage) must be initialized with legal values (using direct
assignment to the fields of the block) before the next allocation.
- caml_alloc_shr(n, t) returns a fresh block of size n, with tag t. The size
of the block can be greater than `Max_young_wosize'. (It can also be
smaller, but in this case it is more efficient to call caml_alloc_small
instead of caml_alloc_shr.) If this block is a structured block (i.e. if t
< No_scan_tag), then the fields of the block (initially containing garbage)
must be initialized with legal values (using the initialize function
described below) before the next allocation.
18.4.5 Raising exceptions
==========================
Two functions are provided to raise two standard exceptions:
- caml_failwith(s), where s is a null-terminated C string (with type `char
*'), raises exception Failure with argument s.
- caml_invalid_argument(s), where s is a null-terminated C string (with type
`char *'), raises exception Invalid_argument with argument s.
Raising arbitrary exceptions from C is more delicate: the exception
identifier is dynamically allocated by the Caml program, and therefore must be
communicated to the C function using the registration facility described below
in section 18.7.3. Once the exception identifier is recovered in C, the
following functions actually raise the exception:
- caml_raise_constant(id) raises the exception id with no argument;
- caml_raise_with_arg(id, v) raises the exception id with the Caml value v as
argument;
- caml_raise_with_string(id, s), where s is a null-terminated C string, raises
the exception id with a copy of the C string s as argument.
18.5 Living in harmony with the garbage collector
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Unused blocks in the heap are automatically reclaimed by the garbage
collector. This requires some cooperation from C code that manipulates
heap-allocated blocks.
18.5.1 Simple interface
========================
All the macros described in this section are declared in the memory.h header
file.
Rule 1 A function that has parameters or local variables of type value must
begin with a call to one of the CAMLparam macros and return with CAMLreturn,
CAMLreturn0, or CAMLreturnT.
There are six CAMLparam macros: CAMLparam0 to CAMLparam5, which take zero to
five arguments respectively. If your function has fewer than 5 parameters of
type value, use the corresponding macros with these parameters as arguments. If
your function has more than 5 parameters of type value, use CAMLparam5 with
five of these parameters, and use one or more calls to the CAMLxparam macros
for the remaining parameters (CAMLxparam1 to CAMLxparam5).
The macros CAMLreturn, CAMLreturn0, and CAMLreturnT are used to replace the C
keyword return. Every occurence of return x must be replaced by CAMLreturn (x)
if x has type value, or CAMLreturnT (t, x) (where t is the type of x); every
occurence of return without argument must be replaced by CAMLreturn0. If your C
function is a procedure (i.e. if it returns void), you must insert CAMLreturn0
at the end (to replace C's implicit return).
Note:
some C compilers give bogus warnings about unused variables caml__dummy_xxx
at each use of CAMLparam and CAMLlocal. You should ignore them.
Example:
<<void foo (value v1, value v2, value v3)
{
CAMLparam3 (v1, v2, v3);
...
CAMLreturn0;
}
>>
Note:
if your function is a primitive with more than 5 arguments for use with the
byte-code runtime, its arguments are not values and must not be declared (they
have types value * and int).
Rule 2 Local variables of type value must be declared with one of the
CAMLlocal macros. Arrays of values are declared with CAMLlocalN. These macros
must be used at the beginning of the function, not in a nested block.
The macros CAMLlocal1 to CAMLlocal5 declare and initialize one to five local
variables of type value. The variable names are given as arguments to the
macros. CAMLlocalN(x, n) declares and initializes a local variable of type
value [n]. You can use several calls to these macros if you have more than 5
local variables.
Example:
<<value bar (value v1, value v2, value v3)
{
CAMLparam3 (v1, v2, v3);
CAMLlocal1 (result);
result = caml_alloc (3, 0);
...
CAMLreturn (result);
}
>>
Rule 3 Assignments to the fields of structured blocks must be done with the
Store_field macro (for normal blocks) or Store_double_field macro (for arrays
and records of floating-point numbers). Other assignments must not use
Store_field nor Store_double_field.
Store_field (b, n, v) stores the value v in the field number n of value b,
which must be a block (i.e. Is_block(b) must be true).
Example:
<<value bar (value v1, value v2, value v3)
{
CAMLparam3 (v1, v2, v3);
CAMLlocal1 (result);
result = caml_alloc (3, 0);
Store_field (result, 0, v1);
Store_field (result, 1, v2);
Store_field (result, 2, v3);
CAMLreturn (result);
}
>>
Warning:
The first argument of Store_field and Store_double_field must be a variable
declared by CAMLparam* or a parameter declared by CAMLlocal* to ensure that a
garbage collection triggered by the evaluation of the other arguments will not
invalidate the first argument after it is computed.
Rule 4 Global variables containing values must be registered with the
garbage collector using the register_global_root function.
Registration of a global variable v is achieved by calling
caml_register_global_root(&v) just before a valid value is stored in v for the
first time.
A registered global variable v can be un-registered by calling
caml_remove_global_root(&v).
Note: The CAML macros use identifiers (local variables, type identifiers,
structure tags) that start with caml__. Do not use any identifier starting with
caml__ in your programs.
18.5.2 Low-level interface
===========================
We now give the GC rules corresponding to the low-level allocation functions
caml_alloc_small and caml_alloc_shr. You can ignore those rules if you stick to
the simplified allocation function caml_alloc.
Rule 5 After a structured block (a block with tag less than No_scan_tag) is
allocated with the low-level functions, all fields of this block must be filled
with well-formed values before the next allocation operation. If the block has
been allocated with caml_alloc_small, filling is performed by direct assignment
to the fields of the block:
<<
Field(v, n) = v_n;
>>
If the block has been allocated with caml_alloc_shr, filling is performed
through the caml_initialize function:
<<
caml_initialize(&Field(v, n), v_n);
>>
The next allocation can trigger a garbage collection. The garbage collector
assumes that all structured blocks contain well-formed values. Newly created
blocks contain random data, which generally do not represent well-formed
values.
If you really need to allocate before the fields can receive their final
value, first initialize with a constant value (e.g. Val_unit), then allocate,
then modify the fields with the correct value (see rule 6).
Rule 6 Direct assignment to a field of a block, as in
<<
Field(v, n) = w;
>>
is safe only if v is a block newly allocated by caml_alloc_small; that is,
if no allocation took place between the allocation of v and the assignment to
the field. In all other cases, never assign directly. If the block has just
been allocated by caml_alloc_shr, use caml_initialize to assign a value to a
field for the first time:
<<
caml_initialize(&Field(v, n), w);
>>
Otherwise, you are updating a field that previously contained a well-formed
value; then, call the caml_modify function:
<<
caml_modify(&Field(v, n), w);
>>
To illustrate the rules above, here is a C function that builds and returns a
list containing the two integers given as parameters. First, we write it using
the simplified allocation functions:
<<value alloc_list_int(int i1, int i2)
{
CAMLparam0 ();
CAMLlocal2 (result, r);
r = caml_alloc(2, 0); /* Allocate a cons cell */
Store_field(r, 0, Val_int(i2)); /* car = the integer i2 */
Store_field(r, 1, Val_int(0)); /* cdr = the empty list [] */
result = caml_alloc(2, 0); /* Allocate the other cons cell */
Store_field(result, 0, Val_int(i1)); /* car = the integer i1 */
Store_field(result, 1, r); /* cdr = the first cons cell */
CAMLreturn (result);
}
>>
Here, the registering of result is not strictly needed, because no allocation
takes place after it gets its value, but it's easier and safer to simply
register all the local variables that have type value.
Here is the same function written using the low-level allocation functions.
We notice that the cons cells are small blocks and can be allocated with
caml_alloc_small, and filled by direct assignments on their fields.
<<value alloc_list_int(int i1, int i2)
{
CAMLparam0 ();
CAMLlocal2 (result, r);
r = caml_alloc_small(2, 0); /* Allocate a cons cell */
Field(r, 0) = Val_int(i2); /* car = the integer i2 */
Field(r, 1) = Val_int(0); /* cdr = the empty list [] */
result = caml_alloc_small(2, 0); /* Allocate the other cons cell */
Field(result, 0) = Val_int(i1); /* car = the integer i1 */
Field(result, 1) = r; /* cdr = the first cons cell */
CAMLreturn (result);
}
>>
In the two examples above, the list is built bottom-up. Here is an alternate
way, that proceeds top-down. It is less efficient, but illustrates the use of
modify.
<<value alloc_list_int(int i1, int i2)
{
CAMLparam0 ();
CAMLlocal2 (tail, r);
r = caml_alloc_small(2, 0); /* Allocate a cons cell */
Field(r, 0) = Val_int(i1); /* car = the integer i1 */
Field(r, 1) = Val_int(0); /* A dummy value
tail = caml_alloc_small(2, 0); /* Allocate the other cons cell */
Field(tail, 0) = Val_int(i2); /* car = the integer i2 */
Field(tail, 1) = Val_int(0); /* cdr = the empty list [] */
caml_modify(&Field(r, 1), tail); /* cdr of the result = tail */
CAMLreturn (r);
}
>>
It would be incorrect to perform Field(r, 1) = tail directly, because the
allocation of tail has taken place since r was allocated.
18.6 A complete example
*=*=*=*=*=*=*=*=*=*=*=*=
This section outlines how the functions from the Unix curses library can be
made available to Objective Caml programs. First of all, here is the interface
curses.mli that declares the curses primitives and data types:
<<type window (* The type "window" remains abstract *)
external initscr: unit -> window = "curses_initscr"
external endwin: unit -> unit = "curses_endwin"
external refresh: unit -> unit = "curses_refresh"
external wrefresh : window -> unit = "curses_wrefresh"
external newwin: int -> int -> int -> int -> window = "curses_newwin"
external addch: char -> unit = "curses_addch"
external mvwaddch: window -> int -> int -> char -> unit = "curses_mvwaddch"
external addstr: string -> unit = "curses_addstr"
external mvwaddstr: window -> int -> int -> string -> unit =
"curses_mvwaddstr"
(* lots more omitted *)
>>
To compile this interface:
<< ocamlc -c curses.mli
>>
To implement these functions, we just have to provide the stub code; the core
functions are already implemented in the curses library. The stub code file,
curses_stubs.c, looks like this:
<<#include <curses.h>
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/alloc.h>
#include <caml/custom.h>
/* Encapsulation of opaque window handles (of type WINDOW *)
as Caml custom blocks. */
static struct custom_operations curses_window_ops = {
"fr.inria.caml.curses_windows",
custom_finalize_default,
custom_compare_default,
custom_hash_default,
custom_serialize_default,
custom_deserialize_default
};
/* Accessing the WINDOW * part of a Caml custom block */
#define Window_val(v) (*((WINDOW **) Data_custom_val(v)))
/* Allocating a Caml custom block to hold the given WINDOW * */
static value alloc_window(WINDOW * w)
{
value v = alloc_custom(&curses_window_ops, sizeof(WINDOW *), 0, 1);
Window_val(v) = w;
return v;
}
value caml_curses_initscr(value unit)
{
CAMLparam1 (unit);
CAMLreturn (alloc_window(initscr()));
}
value caml_curses_endwin(value unit)
{
CAMLparam1 (unit);
endwin();
CAMLreturn (Val_unit);
}
value caml_curses_refresh(value unit)
{
CAMLparam1 (unit);
refresh();
CAMLreturn (Val_unit);
}
value caml_curses_wrefresh(value win)
{
CAMLparam1 (win);
wrefresh(Window_val(win));
CAMLreturn (Val_unit);
}
value caml_curses_newwin(value nlines, value ncols, value x0, value y0)
{
CAMLparam4 (nlines, ncols, x0, y0);
CAMLreturn (alloc_window(newwin(Int_val(nlines), Int_val(ncols),
Int_val(x0), Int_val(y0))));
}
value caml_curses_addch(value c)
{
CAMLparam1 (c);
addch(Int_val(c)); /* Characters are encoded like integers */
CAMLreturn (Val_unit);
}
value caml_curses_mvwaddch(value win, value x, value y, value c)
{
CAMLparam4 (win, x, y, c);
mvwaddch(Window_val(win), Int_val(x), Int_val(y), Int_val(c));
CAMLreturn (Val_unit);
}
value caml_curses_addstr(value s)
{
CAMLparam1 (s);
addstr(String_val(s));
CAMLreturn (Val_unit);
}
value caml_curses_mvwaddstr(value win, value x, value y, value s)
{
CAMLparam4 (win, x, y, s);
mvwaddstr(Window_val(win), Int_val(x), Int_val(y), String_val(s));
CAMLreturn (Val_unit);
}
/* This goes on for pages. */
>>
The file curses_stubs.c can be compiled with:
<< cc -c -I/usr/local/lib/ocaml curses.c
>>
or, even simpler,
<< ocamlc -c curses.c
>>
(When passed a .c file, the ocamlc command simply calls the C compiler on
that file, with the right -I option.)
Now, here is a sample Caml program test.ml that uses the curses module:
<<open Curses
let main_window = initscr () in
let small_window = newwin 10 5 20 10 in
mvwaddstr main_window 10 2 "Hello";
mvwaddstr small_window 4 3 "world";
refresh();
Unix.sleep 5;
endwin()
>>
To compile and link this program, run:
<< ocamlc -custom -o test unix.cma test.ml curses_stubs.o -cclib
-lcurses
>>
(On some machines, you may need to put -cclib -ltermcap or -cclib -lcurses
-cclib -ltermcap instead of -cclib -lcurses.)
18.7 Advanced topic: callbacks from C to Caml
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
So far, we have described how to call C functions from Caml. In this section,
we show how C functions can call Caml functions, either as callbacks (Caml
calls C which calls Caml), or because the main program is written in C.
18.7.1 Applying Caml closures from C
=====================================
C functions can apply Caml functional values (closures) to Caml values. The
following functions are provided to perform the applications:
- caml_callback(f, a) applies the functional value f to the value a and return
the value returned by f.
- caml_callback2(f, a, b) applies the functional value f (which is assumed to
be a curried Caml function with two arguments) to a and b.
- caml_callback3(f, a, b, c) applies the functional value f (a curried Caml
function with three arguments) to a, b and c.
- caml_callbackN(f, n, args) applies the functional value f to the n arguments
contained in the array of values args.
If the function f does not return, but raises an exception that escapes the
scope of the application, then this exception is propagated to the next
enclosing Caml code, skipping over the C code. That is, if a Caml function f
calls a C function g that calls back a Caml function h that raises a stray
exception, then the execution of g is interrupted and the exception is
propagated back into f.
If the C code wishes to catch exceptions escaping the Caml function, it can
use the functions caml_callback_exn, caml_callback2_exn, caml_callback3_exn,
caml_callbackN_exn. These functions take the same arguments as their non-_exn
counterparts, but catch escaping exceptions and return them to the C code. The
return value v of the caml_callback*_exn functions must be tested with the
macro Is_exception_result(v). If the macro returns "false", no exception
occured, and v is the value returned by the Caml function. If
Is_exception_result(v) returns "true", an exception escaped, and its value (the
exception descriptor) can be recovered using Extract_exception(v).
18.7.2 Registering Caml closures for use in C functions
========================================================
The main difficulty with the callback functions described above is obtaining
a closure to the Caml function to be called. For this purpose, Objective Caml
provides a simple registration mechanism, by which Caml code can register Caml
functions under some global name, and then C code can retrieve the
corresponding closure by this global name.
On the Caml side, registration is performed by evaluating Callback.register n
v. Here, n is the global name (an arbitrary string) and v the Caml value. For
instance:
<< let f x = print_string "f is applied to "; print_int n; print_newline()
let _ = Callback.register "test function" f
>>
On the C side, a pointer to the value registered under name n is obtained by
calling caml_named_value(n). The returned pointer must then be dereferenced to
recover the actual Caml value. If no value is registered under the name n, the
null pointer is returned. For example, here is a C wrapper that calls the Caml
function f above:
<< void call_caml_f(int arg)
{
caml_callback(*caml_named_value("test function"), Val_int(arg));
}
>>
The pointer returned by caml_named_value is constant and can safely be cached
in a C variable to avoid repeated name lookups. On the other hand, the value
pointed to can change during garbage collection and must always be recomputed
at the point of use. Here is a more efficient variant of call_caml_f above that
calls caml_named_value only once:
<< void call_caml_f(int arg)
{
static value * closure_f = NULL;
if (closure_f == NULL) {
/* First time around, look up by name */
closure_f = caml_named_value("test function");
}
caml_callback(*closure_f, Val_int(arg));
}
>>
18.7.3 Registering Caml exceptions for use in C functions
==========================================================
The registration mechanism described above can also be used to communicate
exception identifiers from Caml to C. The Caml code registers the exception by
evaluating Callback.register_exception n exn, where n is an arbitrary name and
exn is an exception value of the exception to register. For example:
<< exception Error of string
let _ = Callback.register_exception "test exception" (Error "any string")
>>
The C code can then recover the exception identifier using caml_named_value
and pass it as first argument to the functions raise_constant, raise_with_arg,
and raise_with_string (described in section 18.4.5) to actually raise the
exception. For example, here is a C function that raises the Error exception
with the given argument:
<< void raise_error(char * msg)
{
caml_raise_with_string(*caml_named_value("test exception"), msg);
}
>>
18.7.4 Main program in C
=========================
In normal operation, a mixed Caml/C program starts by executing the Caml
initialization code, which then may proceed to call C functions. We say that
the main program is the Caml code. In some applications, it is desirable that
the C code plays the role of the main program, calling Caml functions when
needed. This can be achieved as follows:
- The C part of the program must provide a main function, which will override
the default main function provided by the Caml runtime system. Execution
will start in the user-defined main function just like for a regular C
program.
- At some point, the C code must call caml_main(argv) to initialize the Caml
code. The argv argument is a C array of strings (type char **), terminated
with a NULL pointer, which represents the command-line arguments, as passed
as second argument to main. The Caml array Sys.argv will be initialized from
this parameter. For the bytecode compiler, argv[0] and argv[1] are also
consulted to find the file containing the bytecode.
- The call to caml_main initializes the Caml runtime system, loads the
bytecode (in the case of the bytecode compiler), and executes the
initialization code of the Caml program. Typically, this initialization code
registers callback functions using Callback.register. Once the Caml
initialization code is complete, control returns to the C code that called
caml_main.
- The C code can then invoke Caml functions using the callback mechanism (see
section 18.7.1).
18.7.5 Embedding the Caml code in the C code
=============================================
The bytecode compiler in custom runtime mode (ocamlc -custom) normally
appends the bytecode to the executable file containing the custom runtime. This
has two consequences. First, the final linking step must be performed by
ocamlc. Second, the Caml runtime library must be able to find the name of the
executable file from the command-line arguments. When using caml_main(argv) as
in section 18.7.4, this means that argv[0] or argv[1] must contain the
executable file name.
An alternative is to embed the bytecode in the C code. The -output-obj option
to ocamlc is provided for this purpose. It causes the ocamlc compiler to output
a C object file (.o file) containing the bytecode for the Caml part of the
program, as well as a caml_startup function. The C object file produced by
ocamlc -output-obj can then be linked with C code using the standard C
compiler, or stored in a C library.
The caml_startup function must be called from the main C program in order to
initialize the Caml runtime and execute the Caml initialization code. Just like
caml_main, it takes one argv parameter containing the command-line parameters.
Unlike caml_main, this argv parameter is used only to initialize Sys.argv, but
not for finding the name of the executable file.
The native-code compiler ocamlopt also supports the -output-obj option,
causing it to output a C object file containing the native code for all Caml
modules on the command-line, as well as the Caml startup code. Initialization
is performed by calling caml_startup as in the case of the bytecode compiler.
For the final linking phase, in addition to the object file produced by
-output-obj, you will have to provide the Objective Caml runtime library
(libcamlrun.a for bytecode, libasmrun.a for native-code), as well as all C
libraries that are required by the Caml libraries used. For instance, assume
the Caml part of your program uses the Unix library. With ocamlc, you should
do:
<<
ocamlc -output-obj -o camlcode.o unix.cma other .cmo and .cma files
cc -o myprog C objects and libraries \
camlcode.o -L/usr/local/lib/ocaml -lunix -lcamlrun
>>
With ocamlopt, you should do:
<<
ocamlopt -output-obj -o camlcode.o unix.cmxa other .cmx and .cmxa
files
cc -o myprog C objects and libraries \
camlcode.o -L/usr/local/lib/ocaml -lunix -lasmrun
>>
Warning:
On some ports, special options are required on the final linking phase that
links together the object file produced by the -output-obj option and the
remainder of the program. Those options are shown in the configuration file
config/Makefile generated during compilation of Objective Caml, as the
variables BYTECCLINKOPTS (for object files produced by ocamlc -output-obj) and
NATIVECCLINKOPTS (for object files produced by ocamlopt -output-obj).
Currently, the only ports that require special attention are:
- Alpha under Digital Unix / Tru64 Unix with gcc: object files produced by
ocamlc -output-obj must be linked with the gcc options -Wl,-T,12000000
-Wl,-D,14000000. This is not necessary for object files produced by ocamlopt
-output-obj.
- Windows NT: the object file produced by Objective Caml have been compiled
with the /MT flag, and therefore all other object files linked with it
should also be compiled with /MT.
18.8 Advanced example with callbacks
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This section illustrates the callback facilities described in section 18.7.
We are going to package some Caml functions in such a way that they can be
linked with C code and called from C just like any C functions. The Caml
functions are defined in the following mod.ml Caml source:
<<(* File mod.ml -- some ``useful'' Caml functions *)
let rec fib n = if n < 2 then 1 else fib(n-1) + fib(n-2)
let format_result n = Printf.sprintf "Result is: %d\n" n
(* Export those two functions to C *)
let _ = Callback.register "fib" fib
let _ = Callback.register "format_result" format_result
>>
Here is the C stub code for calling these functions from C:
<</* File modwrap.c -- wrappers around the Caml functions */
#include <stdio.h>
#include <string.h>
#include <caml/mlvalues.h>
#include <caml/callback.h>
int fib(int n)
{
static value * fib_closure = NULL;
if (fib_closure == NULL) fib_closure = caml_named_value("fib");
return Int_val(caml_callback(*fib_closure, Val_int(n)));
}
char * format_result(int n)
{
static value * format_result_closure = NULL;
if (format_result_closure == NULL)
format_result_closure = caml_named_value("format_result");
return strdup(String_val(caml_callback(*format_result_closure,
Val_int(n))));
/* We copy the C string returned by String_val to the C heap
so that it remains valid after garbage collection. */
}
>>
We now compile the Caml code to a C object file and put it in a C library
along with the stub code in modwrap.c and the Caml runtime system:
<< ocamlc -custom -output-obj -o modcaml.o mod.ml
ocamlc -c modwrap.c
cp /usr/local/lib/ocaml/libcamlrun.a mod.a
ar r mod.a modcaml.o modwrap.o
>>
(One can also use ocamlopt -output-obj instead of ocamlc -custom -output-obj.
In this case, replace libcamlrun.a (the bytecode runtime library) by
libasmrun.a (the native-code runtime library).)
Now, we can use the two functions fib and format_result in any C program,
just like regular C functions. Just remember to call caml_startup once before.
<</* File main.c -- a sample client for the Caml functions */
#include <stdio.h>
int main(int argc, char ** argv)
{
int result;
/* Initialize Caml code */
caml_startup(argv);
/* Do some computation */
result = fib(10);
printf("fib(10) = %s\n", format_result(result));
return 0;
}
>>
To build the whole program, just invoke the C compiler as follows:
<< cc -o prog main.c mod.a -lcurses
>>
(On some machines, you may need to put -ltermcap or -lcurses -ltermcap
instead of -lcurses.)
18.9 Advanced topic: custom blocks
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Blocks with tag Custom_tag contain both arbitrary user data and a pointer to
a C struct, with type struct custom_operations, that associates user-provided
finalization, comparison, hashing, serialization and deserialization functions
to this block.
18.9.1 The struct custom_operations
====================================
The struct custom_operations is defined in <caml/custom.h> and contains the
following fields:
- char *identifier
A zero-terminated character string serving as an identifier for serialization
and deserialization operations.
- void (*finalize)(value v)
The finalize field contains a pointer to a C function that is called when the
block becomes unreachable and is about to be reclaimed. The block is passed
as first argument to the function. The finalize field can also be
custom_finalize_default to indicate that no finalization function is
associated with the block.
- int (*compare)(value v1, value v2)
The compare field contains a pointer to a C function that is called whenever
two custom blocks are compared using Caml's generic comparison operators (=,
<>, <=, >=, <, > and compare). The C function should return 0 if the data
contained in the two blocks are structurally equal, a negative integer if
the data from the first block is less than the data from the second block,
and a positive integer if the data from the first block is greater than the
data from the second block.
The compare field can be set to custom_compare_default; this default
comparison function simply raises Failure.
- long (*hash)(value v)
The hash field contains a pointer to a C function that is called whenever
Caml's generic hash operator (see module Hashtbl) is applied to a custom
block. The C function can return an arbitrary long integer representing the
hash value of the data contained in the given custom block. The hash value
must be compatible with the compare function, in the sense that two
structurally equal data (that is, two custom blocks for which compare
returns 0) must have the same hash value.
The hash field can be set to custom_hash_default, in which case the custom
block is ignored during hash computation.
- void (*serialize)(value v, unsigned long * wsize_32, unsigned long *
wsize_64)
The serialize field contains a pointer to a C function that is called whenever
the custom block needs to be serialized (marshaled) using the Caml functions
output_value or Marshal.to_.... For a custom block, those functions first
write the identifier of the block (as given by the identifier field) to the
output stream, then call the user-provided serialize function. That function
is responsible for writing the data contained in the custom block, using the
serialize_... functions defined in <caml/intext.h> and listed below. The
user-provided serialize function must then store in its wsize_32 and
wsize_64 parameters the sizes in bytes of the data part of the custom block
on a 32-bit architecture and on a 64-bit architecture, respectively.
The serialize field can be set to custom_serialize_default, in which case the
Failure exception is raised when attempting to serialize the custom block.
- unsigned long (*deserialize)(void * dst)
The deserialize field contains a pointer to a C function that is called
whenever a custom block with identifier identifier needs to be deserialized
(un-marshaled) using the Caml functions input_value or Marshal.from_....
This user-provided function is responsible for reading back the data written
by the serialize operation, using the deserialize_... functions defined in
<caml/intext.h> and listed below. It must then rebuild the data part of the
custom block and store it at the pointer given as the dst argument. Finally,
it returns the size in bytes of the data part of the custom block. This size
must be identical to the wsize_32 result of the serialize operation if the
architecture is 32 bits, or wsize_64 if the architecture is 64 bits.
The deserialize field can be set to custom_deserialize_default to indicate
that deserialization is not supported. In this case, do not register the
struct custom_operations with the deserializer using
register_custom_operations (see below).
Note: the finalize, compare, hash, serialize and deserialize functions
attached to custom block descriptors must never trigger a garbage collection.
Within these functions, do not call any of the Caml allocation functions, and
do not perform a callback into Caml code. Do not use CAMLparam to register the
parameters to these functions, and do not use CAMLreturn to return the result.
18.9.2 Allocating custom blocks
================================
Custom blocks must be allocated via the caml_alloc_custom function.
caml_alloc_custom(ops, size, used, max) returns a fresh custom block, with room
for size bytes of user data, and whose associated operations are given by ops
(a pointer to a struct custom_operations, usually statically allocated as a C
global variable).
The two parameters used and max are used to control the speed of garbage
collection when the finalized object contains pointers to out-of-heap
resources. Generally speaking, the Caml incremental major collector adjusts its
speed relative to the allocation rate of the program. The faster the program
allocates, the harder the GC works in order to reclaim quickly unreachable
blocks and avoid having large amount of "floating garbage" (unreferenced
objects that the GC has not yet collected).
Normally, the allocation rate is measured by counting the in-heap size of
allocated blocks. However, it often happens that finalized objects contain
pointers to out-of-heap memory blocks and other resources (such as file
descriptors, X Windows bitmaps, etc.). For those blocks, the in-heap size of
blocks is not a good measure of the quantity of resources allocated by the
program.
The two arguments used and max give the GC an idea of how much out-of-heap
resources are consumed by the finalized block being allocated: you give the
amount of resources allocated to this object as parameter used, and the maximum
amount that you want to see in floating garbage as parameter max. The units are
arbitrary: the GC cares only about the ratio used / max.
For instance, if you are allocating a finalized block holding an X Windows
bitmap of w by h pixels, and you'd rather not have more than 1 mega-pixels of
unreclaimed bitmaps, specify used = w * h and max = 1000000.
Another way to describe the effect of the used and max parameters is in terms
of full GC cycles. If you allocate many custom blocks with used / max = 1 / N,
the GC will then do one full cycle (examining every object in the heap and
calling finalization functions on those that are unreachable) every N
allocations. For instance, if used = 1 and max = 1000, the GC will do one full
cycle at least every 1000 allocations of custom blocks.
If your finalized blocks contain no pointers to out-of-heap resources, or if
the previous discussion made little sense to you, just take used = 0 and max =
1. But if you later find that the finalization functions are not called "often
enough", consider increasing the used / max ratio.
18.9.3 Accessing custom blocks
===============================
The data part of a custom block v can be accessed via the pointer
Data_custom_val(v). This pointer has type void * and should be cast to the
actual type of the data stored in the custom block.
The contents of custom blocks are not scanned by the garbage collector, and
must therefore not contain any pointer inside the Caml heap. In other terms,
never store a Caml value in a custom block, and do not use Field, Store_field
nor modify to access the data part of a custom block. Conversely, any C data
structure (not containing heap pointers) can be stored in a custom block.
18.9.4 Writing custom serialization and deserialization functions
==================================================================
The following functions, defined in <caml/intext.h>, are provided to write
and read back the contents of custom blocks in a portable way. Those functions
handle endianness conversions when e.g. data is written on a little-endian
machine and read back on a big-endian machine.
-------------------------------------------------------
| Function | Action |
-------------------------------------------------------
| caml_serialize_int_1 |Write a 1-byte integer |
|caml_serialize_int_2 |Write a 2-byte integer |
|caml_serialize_int_4 |Write a 4-byte integer |
|caml_serialize_int_8 |Write a 8-byte integer |
|caml_serialize_float_4 |Write a 4-byte float |
|caml_serialize_float_8 |Write a 8-byte float |
|caml_serialize_block_1 |Write an array of 1-byte |
| |quantities |
|caml_serialize_block_2 |Write an array of 2-byte |
| |quantities |
|caml_serialize_block_4 |Write an array of 4-byte |
| |quantities |
|caml_serialize_block_8 |Write an array of 8-byte |
| |quantities |
|caml_deserialize_uint_1 |Read an unsigned 1-byte |
| |integer |
|caml_deserialize_sint_1 |Read a signed 1-byte integer|
| | |
|caml_deserialize_uint_2 |Read an unsigned 2-byte |
| |integer |
|caml_deserialize_sint_2 |Read a signed 2-byte integer|
| | |
|caml_deserialize_uint_4 |Read an unsigned 4-byte |
| |integer |
|caml_deserialize_sint_4 |Read a signed 4-byte integer|
| | |
|caml_deserialize_uint_8 |Read an unsigned 8-byte |
| |integer |
|caml_deserialize_sint_8 |Read a signed 8-byte integer|
| | |
|caml_deserialize_float_4|Read a 4-byte float |
|caml_deserialize_float_8|Read an 8-byte float |
|caml_deserialize_block_1|Read an array of 1-byte |
| |quantities |
|caml_deserialize_block_2|Read an array of 2-byte |
| |quantities |
|caml_deserialize_block_4|Read an array of 4-byte |
| |quantities |
|caml_deserialize_block_8|Read an array of 8-byte |
| |quantities |
|caml_deserialize_error |Signal an error during |
| |deserialization; input_value|
| |or Marshal.from_... raise a |
| |Failure exception after |
| |cleaning up their internal |
| |data structures |
-------------------------------------------------------
Serialization functions are attached to the custom blocks to which they
apply. Obviously, deserialization functions cannot be attached this way, since
the custom block does not exist yet when deserialization begins! Thus, the
struct custom_operations that contain deserialization functions must be
registered with the deserializer in advance, using the
register_custom_operations function declared in <caml/custom.h>.
Deserialization proceeds by reading the identifier off the input stream,
allocating a custom block of the size specified in the input stream, searching
the registered struct custom_operation blocks for one with the same identifier,
and calling its deserialize function to fill the data part of the custom block.
18.9.5 Choosing identifiers
============================
Identifiers in struct custom_operations must be chosen carefully, since they
must identify uniquely the data structure for serialization and deserialization
operations. In particular, consider including a version number in the
identifier; this way, the format of the data can be changed later, yet
backward-compatible deserialisation functions can be provided.
Identifiers starting with _ (an underscore character) are reserved for the
Objective Caml runtime system; do not use them for your custom data. We
recommend to use a URL (http://mymachine.mydomain.com/mylibrary/version-number)
or a Java-style package name (com.mydomain.mymachine.mylibrary.version-number)
as identifiers, to minimize the risk of identifier collision.
18.9.6 Finalized blocks
========================
Custom blocks generalize the finalized blocks that were present in Objective
Caml prior to version 3.00. For backward compatibility, the format of custom
blocks is compatible with that of finalized blocks, and the alloc_final
function is still available to allocate a custom block with a given
finalization function, but default comparison, hashing and serialization
functions. caml_alloc_final(n, f, used, max) returns a fresh custom block of
size n words, with finalization function f. The first word is reserved for
storing the custom operations; the other n-1 words are available for your data.
The two parameters used and max are used to control the speed of garbage
collection, as described for caml_alloc_custom.
18.10 Building mixed C/Caml libraries: ocamlmklib
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
The ocamlmklib command facilitates the construction of libraries containing
both Caml code and C code, and usable both in static linking and dynamic
linking modes.
Windows:
This command is available only under Cygwin, but not for the native Win32
port.
The ocamlmklib command takes three kinds of arguments:
- Caml source files and object files (.cmo, .cmx, .ml) comprising the Caml
part of the library;
- C object files (.o, .a) comprising the C part of the library;
- Support libraries for the C part (-llib).
It generates the following outputs:
- A Caml bytecode library .cma incorporating the .cmo and .ml Caml files given
as arguments, and automatically referencing the C library generated with the
C object files.
- A Caml native-code library .cmxa incorporating the .cmx and .ml Caml files
given as arguments, and automatically referencing the C library generated
with the C object files.
- If dynamic linking is supported on the target platform, a .so shared library
built from the C object files given as arguments, and automatically
referencing the support libraries.
- A C static library .a built from the C object files.
In addition, the following options are recognized:
-cclib, -ccopt, -I, -linkall These options are passed as is to ocamlc or
ocamlopt. See the documentation of these commands.
-pthread, -rpath, -R, -Wl,-rpath, -Wl,-R These options are passed as is to
the C compiler. Refer to the documentation of the C compiler.
-custom Force the construction of a statically linked library only, even if
dynamic linking is supported.
-failsafe Fall back to building a statically linked library if a problem
occurs while building the shared library (e.g. some of the support libraries
are not available as shared libraries).
-Ldir Add dir to the search path for support libraries (-llib).
-ocamlc cmd Use cmd instead of ocamlc to call the bytecode compiler.
-ocamlopt cmd Use cmd instead of ocamlopt to call the native-code compiler.
-o output Set the name of the generated Caml library. ocamlmklib will
generate output.cma and/or output.cmxa. If not specified, defaults to a.
-oc outputc Set the name of the generated C library. ocamlmklib will generate
liboutputc.so (if shared libraries are supported) and liboutputc.a. If not
specified, defaults to the output name given with -o.
Example
Consider a Caml interface to the standard libz C library for reading and
writing compressed files. Assume this library resides in /usr/local/zlib. This
interface is composed of a Caml part zip.cmo/zip.cmx and a C part zipstubs.o
containing the stub code around the libz entry points. The following command
builds the Caml libraries zip.cma and zip.cmxa, as well as the companion C
libraries dllzip.so and libzip.a:
<<ocamlmklib -o zip zip.cmo zip.cmx zipstubs.o -lz -L/usr/local/zlib
>>
If shared libraries are supported, this performs the following commands:
<<ocamlc -a -o zip.cma zip.cmo -dllib -lzip \
-cclib -lzip -cclib -lz -ccopt -L/usr/local/zlib
ocamlopt -a -o zip.cmxa zip.cmx -cclib -lzip \
-cclib -lzip -cclib -lz -ccopt -L/usr/local/zlib
gcc -shared -o dllzip.so zipstubs.o -lz -L/usr/local/zlib
ar rc libzip.a zipstubs.o
>>
If shared libraries are not supported, the following commands are performed
instead:
<<ocamlc -a -custom -o zip.cma zip.cmo -cclib -lzip \
-cclib -lz -ccopt -L/usr/local/zlib
ocamlopt -a -o zip.cmxa zip.cmx -lzip \
-cclib -lz -ccopt -L/usr/local/zlib
ar rc libzip.a zipstubs.o
>>
Instead of building simultaneously the bytecode library, the native-code
library and the C libraries, ocamlmklib can be called three times to build each
separately. Thus,
<<ocamlmklib -o zip zip.cmo -lz -L/usr/local/zlib
>>
builds the bytecode library zip.cma, and
<<ocamlmklib -o zip zip.cmx -lz -L/usr/local/zlib
>>
builds the native-code library zip.cmxa, and
<<ocamlmklib -o zip zipstubs.o -lz -L/usr/local/zlib
>>
builds the C libraries dllzip.so and libzip.a. Notice that the support
libraries (-lz) and the corresponding options (-L/usr/local/zlib) must be given
on all three invocations of ocamlmklib, because they are needed at different
times depending on whether shared libraries are supported.
Part: IV
********
The Objective Caml library
**************************
Chapter 19 The core library
******************************
This chapter describes the Objective Caml core library, which is composed of
declarations for built-in types and exceptions, plus the module Pervasives that
provides basic operations on these built-in types. The Pervasives module is
special in two ways:
- It is automatically linked with the user's object code files by the ocamlc
command (chapter 8).
- It is automatically "opened" when a compilation starts, or when the toplevel
system is launched. Hence, it is possible to use unqualified identifiers to
refer to the functions provided by the Pervasives module, without adding a
open Pervasives directive.
Conventions
*=*=*=*=*=*
The declarations of the built-in types and the components of module
Pervasives are printed one by one in typewriter font, followed by a short
comment. All library modules and the components they provide are indexed at the
end of this report.
19.1 Built-in types and predefined exceptions
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
The following built-in types and predefined exceptions are always defined in
the compilation environment, but are not part of any module. As a consequence,
they can only be referred by their short names.
Built-in types
==============
<<
type int
>>
The type of integer numbers.
<<
type char
>>
The type of characters.
<<
type string
>>
The type of character strings.
<<
type float
>>
The type of floating-point numbers.
<<
type bool = false | true
>>
The type of booleans (truth values).
<<
type unit = ()
>>
The type of the unit value.
<<
type exn
>>
The type of exception values.
<<
type 'a array
>>
The type of arrays whose elements have type 'a.
<<
type 'a list = [] | :: of 'a * 'a list
>>
The type of lists whose elements have type 'a.
<<
type 'a option = None | Some of 'a
>>
The type of optional values of type 'a.
<<
type int32
>>
The type of signed 32-bit integers. See the Int32[] module.
<<
type int64
>>
The type of signed 64-bit integers. See the Int64[] module.
<<
type nativeint
>>
The type of signed, platform-native integers (32 bits on 32-bit processors,
64 bits on 64-bit processors). See the Nativeint[] module.
<<
type ('a, 'b, 'c, 'd) format4
>>
The type of format strings. 'a is the type of the parameters of the format,
'd is the result type for the printf-style function, 'b is the type of the
first argument given to \%a and \%t printing functions (see module
Printf[]), and 'c is the result type of these functions.
<<
type 'a lazy_t
>>
This type is used to implement the Lazy[] module. It should not be used
directly.
Predefined exceptions
=====================
<<
exception Match_failure of (string * int * int)
>>
Exception raised when none of the cases of a pattern-matching apply. The
arguments are the location of the match keyword in the source code (file
name, line number, column number).
<<
exception Assert_failure of (string * int * int)
>>
Exception raised when an assertion fails. The arguments are the location of
the assert keyword in the source code (file name, line number, column
number).
<<
exception Invalid_argument of string
>>
Exception raised by library functions to signal that the given arguments do
not make sense.
<<
exception Failure of string
>>
Exception raised by library functions to signal that they are undefined on
the given arguments.
<<
exception Not_found
>>
Exception raised by search functions when the desired object could not be
found.
<<
exception Out_of_memory
>>
Exception raised by the garbage collector when there is insufficient memory
to complete the computation.
<<
exception Stack_overflow
>>
Exception raised by the bytecode interpreter when the evaluation stack
reaches its maximal size. This often indicates infinite or excessively deep
recursion in the user's program. (Not fully implemented by the native-code
compiler; see section 11.5.)
<<
exception Sys_error of string
>>
Exception raised by the input/output functions to report an operating
system error.
<<
exception End_of_file
>>
Exception raised by input functions to signal that the end of file has been
reached.
<<
exception Division_by_zero
>>
Exception raised by division and remainder operations when their second
argument is null. (Not fully implemented by the native-code compiler; see
section 11.5.)
<<
exception Sys_blocked_io
>>
A special case of Sys_error raised when no I/O is possible on a
non-blocking I/O channel.
<<
exception Undefined_recursive_module of (string * int * int)
>>
Exception raised when an ill-founded recursive module definition is
evaluated. (See section 7.9.) The arguments are the location of the
definition in the source code (file name, line number, column number).
19.2 Module Pervasives : The initially opened module.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module provides the basic operations over the built-in types (numbers,
booleans, strings, exceptions, references, lists, arrays, input-output
channels, ...)
This module is automatically opened at the beginning of each compilation. All
components of this module can therefore be referred by their short name,
without prefixing them by Pervasives.
Exceptions
==========
<<
val raise : exn -> 'a
>>
Raise the given exception value
<<
val invalid_arg : string -> 'a
>>
Raise exception Invalid_argument with the given string.
<<
val failwith : string -> 'a
>>
Raise exception Failure with the given string.
<<
exception Exit
>>
The Exit exception is not raised by any library function. It is provided
for use in your programs.
Comparisons
===========
<<
val (=) : 'a -> 'a -> bool
>>
e1 = e2 tests for structural equality of e1 and e2. Mutable structures
(e.g. references and arrays) are equal if and only if their current contents
are structurally equal, even if the two mutable objects are not the same
physical object. Equality between functional values raises Invalid_argument.
Equality between cyclic data structures does not terminate.
<<
val (<>) : 'a -> 'a -> bool
>>
Negation of Pervasives.(=)[19.2].
<<
val (<) : 'a -> 'a -> bool
>>
See Pervasives.(>=)[19.2].
<<
val (>) : 'a -> 'a -> bool
>>
See Pervasives.(>=)[19.2].
<<
val (<=) : 'a -> 'a -> bool
>>
See Pervasives.(>=)[19.2].
<<
val (>=) : 'a -> 'a -> bool
>>
Structural ordering functions. These functions coincide with the usual
orderings over integers, characters, strings and floating-point numbers, and
extend them to a total ordering over all types. The ordering is compatible
with (=). As in the case of (=), mutable structures are compared by
contents. Comparison between functional values raises Invalid_argument.
Comparison between cyclic structures does not terminate.
<<
val compare : 'a -> 'a -> int
>>
compare x y returns 0 if x is equal to y, a negative integer if x is less
than y, and a positive integer if x is greater than y. The ordering
implemented by compare is compatible with the comparison predicates =, < and
> defined above, with one difference on the treatment of the float value
Pervasives.nan[19.2]. Namely, the comparison predicates treat nan as
different from any other float value, including itself; while compare treats
nan as equal to itself and less than any other float value. This treatment
of nan ensures that compare defines a total ordering relation.
compare applied to functional values may raise Invalid_argument. compare
applied to cyclic structures may not terminate.
The compare function can be used as the comparison function required by the
Set.Make[20.28] and Map.Make[20.18] functors, as well as the
List.sort[20.17] and Array.sort[20.2] functions.
<<
val min : 'a -> 'a -> 'a
>>
Return the smaller of the two arguments.
<<
val max : 'a -> 'a -> 'a
>>
Return the greater of the two arguments.
<<
val (==) : 'a -> 'a -> bool
>>
e1 == e2 tests for physical equality of e1 and e2. On integers and
characters, physical equality is identical to structural equality. On
mutable structures, e1 == e2 is true if and only if physical modification of
e1 also affects e2. On non-mutable structures, the behavior of (==) is
implementation-dependent; however, it is guaranteed that e1 == e2 implies
compare e1 e2 = 0.
<<
val (!=) : 'a -> 'a -> bool
>>
Negation of Pervasives.(==)[19.2].
Boolean operations
==================
<<
val not : bool -> bool
>>
The boolean negation.
<<
val (&&) : bool -> bool -> bool
>>
The boolean "and". Evaluation is sequential, left-to-right: in e1 && e2, e1
is evaluated first, and if it returns false, e2 is not evaluated at all.
<<
val (&) : bool -> bool -> bool
>>
Deprecated. Pervasives.(&&)[19.2] should be used instead.
<<
val (||) : bool -> bool -> bool
>>
The boolean "or". Evaluation is sequential, left-to-right: in e1 || e2, e1
is evaluated first, and if it returns true, e2 is not evaluated at all.
<<
val or : bool -> bool -> bool
>>
Deprecated. Pervasives.(||)[19.2] should be used instead.
Integer arithmetic
==================
Integers are 31 bits wide (or 63 bits on 64-bit processors). All operations
are taken modulo 2^31 (or 2^63). They do not fail on overflow.
<<
val (~-) : int -> int
>>
Unary negation. You can also write -e instead of ~-e.
<<
val succ : int -> int
>>
succ x is x+1.
<<
val pred : int -> int
>>
pred x is x-1.
<<
val (+) : int -> int -> int
>>
Integer addition.
<<
val (-) : int -> int -> int
>>
Integer subtraction.
<<
val (*) : int -> int -> int
>>
Integer multiplication.
<<
val (/) : int -> int -> int
>>
Integer division. Raise Division_by_zero if the second argument is 0.
Integer division rounds the real quotient of its arguments towards zero.
More precisely, if x >= 0 and y > 0, x / y is the greatest integer less than
or equal to the real quotient of x by y. Moreover, (-x) / y = x / (-y) = -(x
/ y).
<<
val mod : int -> int -> int
>>
Integer remainder. If y is not zero, the result of x mod y satisfies the
following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
abs(y)-1. If y = 0, x mod y raises Division_by_zero. Notice that x mod y is
nonpositive if and only if x < 0. Raise Division_by_zero if y is zero.
<<
val abs : int -> int
>>
Return the absolute value of the argument. Note that this may be negative
if the argument is min_int.
<<
val max_int : int
>>
The greatest representable integer.
<<
val min_int : int
>>
The smallest representable integer.
Bitwise operations
------------------
<<
val land : int -> int -> int
>>
Bitwise logical and.
<<
val lor : int -> int -> int
>>
Bitwise logical or.
<<
val lxor : int -> int -> int
>>
Bitwise logical exclusive or.
<<
val lnot : int -> int
>>
Bitwise logical negation.
<<
val lsl : int -> int -> int
>>
n lsl m shifts n to the left by m bits. The result is unspecified if m < 0
or m >= bitsize, where bitsize is 32 on a 32-bit platform and 64 on a 64-bit
platform.
<<
val lsr : int -> int -> int
>>
n lsr m shifts n to the right by m bits. This is a logical shift: zeroes
are inserted regardless of the sign of n. The result is unspecified if m < 0
or m >= bitsize.
<<
val asr : int -> int -> int
>>
n asr m shifts n to the right by m bits. This is an arithmetic shift: the
sign bit of n is replicated. The result is unspecified if m < 0 or m >=
bitsize.
Floating-point arithmetic
=========================
Caml's floating-point numbers follow the IEEE 754 standard, using double
precision (64 bits) numbers. Floating-point operations never raise an exception
on overflow, underflow, division by zero, etc. Instead, special IEEE numbers
are returned as appropriate, such as infinity for 1.0 /. 0.0, neg_infinity for
-1.0 /. 0.0, and nan ("not a number") for 0.0 /. 0.0. These special numbers
then propagate through floating-point computations as expected: for instance,
1.0 /. infinity is 0.0, and any operation with nan as argument returns nan as
result.
<<
val (~-.) : float -> float
>>
Unary negation. You can also write -.e instead of ~-.e.
<<
val (+.) : float -> float -> float
>>
Floating-point addition
<<
val (-.) : float -> float -> float
>>
Floating-point subtraction
<<
val (*.) : float -> float -> float
>>
Floating-point multiplication
<<
val (/.) : float -> float -> float
>>
Floating-point division.
<<
val (**) : float -> float -> float
>>
Exponentiation
<<
val sqrt : float -> float
>>
Square root
<<
val exp : float -> float
>>
Exponential.
<<
val log : float -> float
>>
Natural logarithm.
<<
val log10 : float -> float
>>
Base 10 logarithm.
<<
val cos : float -> float
>>
See Pervasives.atan2[19.2].
<<
val sin : float -> float
>>
See Pervasives.atan2[19.2].
<<
val tan : float -> float
>>
See Pervasives.atan2[19.2].
<<
val acos : float -> float
>>
See Pervasives.atan2[19.2].
<<
val asin : float -> float
>>
See Pervasives.atan2[19.2].
<<
val atan : float -> float
>>
See Pervasives.atan2[19.2].
<<
val atan2 : float -> float -> float
>>
The usual trigonometric functions.
<<
val cosh : float -> float
>>
See Pervasives.tanh[19.2].
<<
val sinh : float -> float
>>
See Pervasives.tanh[19.2].
<<
val tanh : float -> float
>>
The usual hyperbolic trigonometric functions.
<<
val ceil : float -> float
>>
See Pervasives.floor[19.2].
<<
val floor : float -> float
>>
Round the given float to an integer value. floor f returns the greatest
integer value less than or equal to f. ceil f returns the least integer
value greater than or equal to f.
<<
val abs_float : float -> float
>>
Return the absolute value of the argument.
<<
val mod_float : float -> float -> float
>>
mod_float a b returns the remainder of a with respect to b. The returned
value is a -. n *. b, where n is the quotient a /. b rounded towards zero to
an integer.
<<
val frexp : float -> float * int
>>
frexp f returns the pair of the significant and the exponent of f. When f
is zero, the significant x and the exponent n of f are equal to zero. When f
is non-zero, they are defined by f = x *. 2 ** n and 0.5 <= x < 1.0.
<<
val ldexp : float -> int -> float
>>
ldexp x n returns x *. 2 ** n.
<<
val modf : float -> float * float
>>
modf f returns the pair of the fractional and integral part of f.
<<
val float : int -> float
>>
Same as Pervasives.float_of_int[19.2].
<<
val float_of_int : int -> float
>>
Convert an integer to floating-point.
<<
val truncate : float -> int
>>
Same as Pervasives.int_of_float[19.2].
<<
val int_of_float : float -> int
>>
Truncate the given floating-point number to an integer. The result is
unspecified if the argument is nan or falls outside the range of
representable integers.
<<
val infinity : float
>>
Positive infinity.
<<
val neg_infinity : float
>>
Negative infinity.
<<
val nan : float
>>
A special floating-point value denoting the result of an undefined
operation such as 0.0 /. 0.0. Stands for "not a number". Any floating-point
operation with nan as argument returns nan as result. As for floating-point
comparisons, =, <, <=, > and >= return false and <> returns true if one or
both of their arguments is nan.
<<
val max_float : float
>>
The largest positive finite value of type float.
<<
val min_float : float
>>
The smallest positive, non-zero, non-denormalized value of type float.
<<
val epsilon_float : float
>>
The smallest positive float x such that 1.0 +. x <> 1.0.
<<
type fpclass =
| FP_normal
>>
Normal number, none of the below
<<
| FP_subnormal
>>
Number very close to 0.0, has reduced precision
<<
| FP_zero
>>
Number is 0.0 or -0.0
<<
| FP_infinite
>>
Number is positive or negative infinity
<<
| FP_nan
>>
Not a number: result of an undefined operation
The five classes of floating-point numbers, as determined by the
Pervasives.classify_float[19.2] function.
<<
val classify_float : float -> fpclass
>>
Return the class of the given floating-point number: normal, subnormal,
zero, infinite, or not a number.
String operations
=================
More string operations are provided in module String[20.33].
<<
val (^) : string -> string -> string
>>
String concatenation.
Character operations
====================
More character operations are provided in module Char[20.5].
<<
val int_of_char : char -> int
>>
Return the ASCII code of the argument.
<<
val char_of_int : int -> char
>>
Return the character with the given ASCII code. Raise Invalid_argument
"char_of_int" if the argument is outside the range 0--255.
Unit operations
===============
<<
val ignore : 'a -> unit
>>
Discard the value of its argument and return (). For instance, ignore(f x)
discards the result of the side-effecting function f. It is equivalent to f
x; (), except that the latter may generate a compiler warning; writing
ignore(f x) instead avoids the warning.
String conversion functions
===========================
<<
val string_of_bool : bool -> string
>>
Return the string representation of a boolean.
<<
val bool_of_string : string -> bool
>>
Convert the given string to a boolean. Raise Invalid_argument
"bool_of_string" if the string is not "true" or "false".
<<
val string_of_int : int -> string
>>
Return the string representation of an integer, in decimal.
<<
val int_of_string : string -> int
>>
Convert the given string to an integer. The string is read in decimal (by
default) or in hexadecimal (if it begins with 0x or 0X), octal (if it begins
with 0o or 0O), or binary (if it begins with 0b or 0B). Raise Failure
"int_of_string" if the given string is not a valid representation of an
integer, or if the integer represented exceeds the range of integers
representable in type int.
<<
val string_of_float : float -> string
>>
Return the string representation of a floating-point number.
<<
val float_of_string : string -> float
>>
Convert the given string to a float. Raise Failure "float_of_string" if the
given string is not a valid representation of a float.
Pair operations
===============
<<
val fst : 'a * 'b -> 'a
>>
Return the first component of a pair.
<<
val snd : 'a * 'b -> 'b
>>
Return the second component of a pair.
List operations
===============
More list operations are provided in module List[20.17].
<<
val (@) : 'a list -> 'a list -> 'a list
>>
List concatenation.
Input/output
============
<<
type in_channel
>>
The type of input channel.
<<
type out_channel
>>
The type of output channel.
<<
val stdin : in_channel
>>
The standard input for the process.
<<
val stdout : out_channel
>>
The standard output for the process.
<<
val stderr : out_channel
>>
The standard error ouput for the process.
Output functions on standard output
-----------------------------------
<<
val print_char : char -> unit
>>
Print a character on standard output.
<<
val print_string : string -> unit
>>
Print a string on standard output.
<<
val print_int : int -> unit
>>
Print an integer, in decimal, on standard output.
<<
val print_float : float -> unit
>>
Print a floating-point number, in decimal, on standard output.
<<
val print_endline : string -> unit
>>
Print a string, followed by a newline character, on standard output and
flush standard output.
<<
val print_newline : unit -> unit
>>
Print a newline character on standard output, and flush standard output.
This can be used to simulate line buffering of standard output.
Output functions on standard error
----------------------------------
<<
val prerr_char : char -> unit
>>
Print a character on standard error.
<<
val prerr_string : string -> unit
>>
Print a string on standard error.
<<
val prerr_int : int -> unit
>>
Print an integer, in decimal, on standard error.
<<
val prerr_float : float -> unit
>>
Print a floating-point number, in decimal, on standard error.
<<
val prerr_endline : string -> unit
>>
Print a string, followed by a newline character on standard error and flush
standard error.
<<
val prerr_newline : unit -> unit
>>
Print a newline character on standard error, and flush standard error.
Input functions on standard input
---------------------------------
<<
val read_line : unit -> string
>>
Flush standard output, then read characters from standard input until a
newline character is encountered. Return the string of all characters read,
without the newline character at the end.
<<
val read_int : unit -> int
>>
Flush standard output, then read one line from standard input and convert
it to an integer. Raise Failure "int_of_string" if the line read is not a
valid representation of an integer.
<<
val read_float : unit -> float
>>
Flush standard output, then read one line from standard input and convert
it to a floating-point number. The result is unspecified if the line read is
not a valid representation of a floating-point number.
General output functions
------------------------
<<
type open_flag =
| Open_rdonly
>>
open for reading.
<<
| Open_wronly
>>
open for writing.
<<
| Open_append
>>
open for appending: always write at end of file.
<<
| Open_creat
>>
create the file if it does not exist.
<<
| Open_trunc
>>
empty the file if it already exists.
<<
| Open_excl
>>
fail if Open_creat and the file already exists.
<<
| Open_binary
>>
open in binary mode (no conversion).
<<
| Open_text
>>
open in text mode (may perform conversions).
<<
| Open_nonblock
>>
open in non-blocking mode.
Opening modes for Pervasives.open_out_gen[19.2] and
Pervasives.open_in_gen[19.2].
<<
val open_out : string -> out_channel
>>
Open the named file for writing, and return a new output channel on that
file, positionned at the beginning of the file. The file is truncated to
zero length if it already exists. It is created if it does not already
exists. Raise Sys_error if the file could not be opened.
<<
val open_out_bin : string -> out_channel
>>
Same as Pervasives.open_out[19.2], but the file is opened in binary mode,
so that no translation takes place during writes. On operating systems that
do not distinguish between text mode and binary mode, this function behaves
like Pervasives.open_out[19.2].
<<
val open_out_gen : open_flag list -> int -> string -> out_channel
>>
open_out_gen mode perm filename opens the named file for writing, as
described above. The extra argument mode specify the opening mode. The extra
argument perm specifies the file permissions, in case the file must be
created. Pervasives.open_out[19.2] and Pervasives.open_out_bin[19.2] are
special cases of this function.
<<
val flush : out_channel -> unit
>>
Flush the buffer associated with the given output channel, performing all
pending writes on that channel. Interactive programs must be careful about
flushing standard output and standard error at the right time.
<<
val flush_all : unit -> unit
>>
Flush all open output channels; ignore errors.
<<
val output_char : out_channel -> char -> unit
>>
Write the character on the given output channel.
<<
val output_string : out_channel -> string -> unit
>>
Write the string on the given output channel.
<<
val output : out_channel -> string -> int -> int -> unit
>>
output oc buf pos len writes len characters from string buf, starting at
offset pos, to the given output channel oc. Raise Invalid_argument "output"
if pos and len do not designate a valid substring of buf.
<<
val output_byte : out_channel -> int -> unit
>>
Write one 8-bit integer (as the single character with that code) on the
given output channel. The given integer is taken modulo 256.
<<
val output_binary_int : out_channel -> int -> unit
>>
Write one integer in binary format (4 bytes, big-endian) on the given
output channel. The given integer is taken modulo 2^32. The only reliable
way to read it back is through the Pervasives.input_binary_int[19.2]
function. The format is compatible across all machines for a given version
of Objective Caml.
<<
val output_value : out_channel -> 'a -> unit
>>
Write the representation of a structured value of any type to a channel.
Circularities and sharing inside the value are detected and preserved. The
object can be read back, by the function Pervasives.input_value[19.2]. See
the description of module Marshal[20.19] for more information.
Pervasives.output_value[19.2] is equivalent to Marshal.to_channel[20.19]
with an empty list of flags.
<<
val seek_out : out_channel -> int -> unit
>>
seek_out chan pos sets the current writing position to pos for channel
chan. This works only for regular files. On files of other kinds (such as
terminals, pipes and sockets), the behavior is unspecified.
<<
val pos_out : out_channel -> int
>>
Return the current writing position for the given channel. Does not work on
channels opened with the Open_append flag (returns unspecified results).
<<
val out_channel_length : out_channel -> int
>>
Return the size (number of characters) of the regular file on which the
given channel is opened. If the channel is opened on a file that is not a
regular file, the result is meaningless.
<<
val close_out : out_channel -> unit
>>
Close the given channel, flushing all buffered write operations. Output
functions raise a Sys_error exception when they are applied to a closed
output channel, except close_out and flush, which do nothing when applied to
an already closed channel. Note that close_out may raise Sys_error if the
operating system signals an error when flushing or closing.
<<
val close_out_noerr : out_channel -> unit
>>
Same as close_out, but ignore all errors.
<<
val set_binary_mode_out : out_channel -> bool -> unit
>>
set_binary_mode_out oc true sets the channel oc to binary mode: no
translations take place during output. set_binary_mode_out oc false sets the
channel oc to text mode: depending on the operating system, some
translations may take place during output. For instance, under Windows,
end-of-lines will be translated from \n to \r\n. This function has no effect
under operating systems that do not distinguish between text mode and binary
mode.
General input functions
-----------------------
<<
val open_in : string -> in_channel
>>
Open the named file for reading, and return a new input channel on that
file, positionned at the beginning of the file. Raise Sys_error if the file
could not be opened.
<<
val open_in_bin : string -> in_channel
>>
Same as Pervasives.open_in[19.2], but the file is opened in binary mode, so
that no translation takes place during reads. On operating systems that do
not distinguish between text mode and binary mode, this function behaves
like Pervasives.open_in[19.2].
<<
val open_in_gen : open_flag list -> int -> string -> in_channel
>>
open_in mode perm filename opens the named file for reading, as described
above. The extra arguments mode and perm specify the opening mode and file
permissions. Pervasives.open_in[19.2] and Pervasives.open_in_bin[19.2] are
special cases of this function.
<<
val input_char : in_channel -> char
>>
Read one character from the given input channel. Raise End_of_file if there
are no more characters to read.
<<
val input_line : in_channel -> string
>>
Read characters from the given input channel, until a newline character is
encountered. Return the string of all characters read, without the newline
character at the end. Raise End_of_file if the end of the file is reached at
the beginning of line.
<<
val input : in_channel -> string -> int -> int -> int
>>
input ic buf pos len reads up to len characters from the given channel ic,
storing them in string buf, starting at character number pos. It returns the
actual number of characters read, between 0 and len (inclusive). A return
value of 0 means that the end of file was reached. A return value between 0
and len exclusive means that not all requested len characters were read,
either because no more characters were available at that time, or because
the implementation found it convenient to do a partial read; input must be
called again to read the remaining characters, if desired. (See also
Pervasives.really_input[19.2] for reading exactly len characters.) Exception
Invalid_argument "input" is raised if pos and len do not designate a valid
substring of buf.
<<
val really_input : in_channel -> string -> int -> int -> unit
>>
really_input ic buf pos len reads len characters from channel ic, storing
them in string buf, starting at character number pos. Raise End_of_file if
the end of file is reached before len characters have been read. Raise
Invalid_argument "really_input" if pos and len do not designate a valid
substring of buf.
<<
val input_byte : in_channel -> int
>>
Same as Pervasives.input_char[19.2], but return the 8-bit integer
representing the character. Raise End_of_file if an end of file was reached.
<<
val input_binary_int : in_channel -> int
>>
Read an integer encoded in binary format (4 bytes, big-endian) from the
given input channel. See Pervasives.output_binary_int[19.2]. Raise
End_of_file if an end of file was reached while reading the integer.
<<
val input_value : in_channel -> 'a
>>
Read the representation of a structured value, as produced by
Pervasives.output_value[19.2], and return the corresponding value. This
function is identical to Marshal.from_channel[20.19]; see the description of
module Marshal[20.19] for more information, in particular concerning the
lack of type safety.
<<
val seek_in : in_channel -> int -> unit
>>
seek_in chan pos sets the current reading position to pos for channel chan.
This works only for regular files. On files of other kinds, the behavior is
unspecified.
<<
val pos_in : in_channel -> int
>>
Return the current reading position for the given channel.
<<
val in_channel_length : in_channel -> int
>>
Return the size (number of characters) of the regular file on which the
given channel is opened. If the channel is opened on a file that is not a
regular file, the result is meaningless. The returned size does not take
into account the end-of-line translations that can be performed when reading
from a channel opened in text mode.
<<
val close_in : in_channel -> unit
>>
Close the given channel. Input functions raise a Sys_error exception when
they are applied to a closed input channel, except close_in, which does
nothing when applied to an already closed channel. Note that close_in may
raise Sys_error if the operating system signals an error.
<<
val close_in_noerr : in_channel -> unit
>>
Same as close_in, but ignore all errors.
<<
val set_binary_mode_in : in_channel -> bool -> unit
>>
set_binary_mode_in ic true sets the channel ic to binary mode: no
translations take place during input. set_binary_mode_out ic false sets the
channel ic to text mode: depending on the operating system, some
translations may take place during input. For instance, under Windows,
end-of-lines will be translated from \r\n to \n. This function has no effect
under operating systems that do not distinguish between text mode and binary
mode.
Operations on large files
-------------------------
<<
module LargeFile : >>
sig
<<
val seek_out : Pervasives.out_channel -> int64 -> unit
>>
<<
val pos_out : Pervasives.out_channel -> int64
>>
<<
val out_channel_length : Pervasives.out_channel -> int64
>>
<<
val seek_in : Pervasives.in_channel -> int64 -> unit
>>
<<
val pos_in : Pervasives.in_channel -> int64
>>
<<
val in_channel_length : Pervasives.in_channel -> int64
>>
end
Operations on large files. This sub-module provides 64-bit variants of the
channel functions that manipulate file positions and file sizes. By
representing positions and sizes by 64-bit integers (type int64) instead of
regular integers (type int), these alternate functions allow operating on
files whose sizes are greater than max_int.
References
==========
<<
type 'a ref = {
mutable contents : 'a ;
}
>>
The type of references (mutable indirection cells) containing a value of
type 'a.
<<
val ref : 'a -> 'a ref
>>
Return a fresh reference containing the given value.
<<
val (!) : 'a ref -> 'a
>>
!r returns the current contents of reference r. Equivalent to fun r ->
r.contents.
<<
val (:=) : 'a ref -> 'a -> unit
>>
r := a stores the value of a in reference r. Equivalent to fun r v ->
r.contents <- v.
<<
val incr : int ref -> unit
>>
Increment the integer contained in the given reference. Equivalent to fun r
-> r := succ !r.
<<
val decr : int ref -> unit
>>
Decrement the integer contained in the given reference. Equivalent to fun r
-> r := pred !r.
Operations on format strings
============================
<<
type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
>>
See modules Printf[20.24] and Scanf[20.27] for more operations on format
strings.
<<
type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
>>
Simplified type for format strings, included for backward compatibility
with earlier releases of Objective Caml. 'a is the type of the parameters of
the format, 'c is the result type for the "printf"-style function, and 'b is
the type of the first argument given to %a and %t printing functions.
<<
val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
>>
Converts a format string into a string.
<<
val format_of_string :
('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c, 'd, 'e, 'f) format6
>>
format_of_string s returns a format string read from the string literal s.
<<
val (^^) :
('a, 'b, 'c, 'd, 'e, 'f) format6 ->
('f, 'b, 'c, 'e, 'g, 'h) format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
>>
f1 ^^f2 catenates formats f1 and f2. The result is a format that accepts
arguments from f1, then arguments from f2.
Program termination
===================
<<
val exit : int -> 'a
>>
Terminate the process, returning the given status code to the operating
system: usually 0 to indicate no errors, and a small positive integer to
indicate failure. All open output channels are flushed with flush_all. An
implicit exit 0 is performed each time a program terminates normally. An
implicit exit 2 is performed if the program terminates early because of an
uncaught exception.
<<
val at_exit : (unit -> unit) -> unit
>>
Register the given function to be called at program termination time. The
functions registered with at_exit will be called when the program executes
Pervasives.exit[19.2], or terminates, either normally or because of an
uncaught exception. The functions are called in "last in, first out" order:
the function most recently added with at_exit is called first.
Chapter 20 The standard library
**********************************
This chapter describes the functions provided by the Objective Caml standard
library. The modules from the standard library are automatically linked with
the user's object code files by the ocamlc command. Hence, these modules can be
used in standalone programs without having to add any .cmo file on the command
line for the linking phase. Similarly, in interactive use, these globals can be
used in toplevel phrases without having to load any .cmo file in memory.
Unlike the Pervasive module from the core library, the modules from the
standard library are not automatically "opened" when a compilation starts, or
when the toplevel system is launched. Hence it is necessary to use qualified
identifiers to refer to the functions provided by these modules, or to add open
directives.
Conventions
*=*=*=*=*=*
For easy reference, the modules are listed below in alphabetical order of
module names. For each module, the declarations from its signature are printed
one by one in typewriter font, followed by a short comment. All modules and the
identifiers they export are indexed at the end of this report.
20.1 Module Arg : Parsing of command line arguments.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module provides a general mechanism for extracting options and arguments
from the command line to the program.
Syntax of command lines: A keyword is a character string starting with a -.
An option is a keyword alone or followed by an argument. The types of keywords
are: Unit, Bool, Set, Clear, String, Set_string, Int, Set_int, Float,
Set_float, Tuple, Symbol, and Rest. Unit, Set and Clear keywords take no
argument. A Rest keyword takes the remaining of the command line as arguments.
Every other keyword takes the following word on the command line as argument.
Arguments not preceded by a keyword are called anonymous arguments.
Examples (cmd is assumed to be the command name):
- cmd -flag (a unit option)
- cmd -int 1 (an int option with argument 1)
- cmd -string foobar (a string option with argument "foobar")
- cmd -float 12.34 (a float option with argument 12.34)
- cmd a b c (three anonymous arguments: "a", "b", and "c")
- cmd a b -- c d (two anonymous arguments and a rest option with two
arguments)
<<
type spec =
| Unit of (unit -> unit)
>>
Call the function with unit argument
<<
| Bool of (bool -> unit)
>>
Call the function with a bool argument
<<
| Set of bool Pervasives.ref
>>
Set the reference to true
<<
| Clear of bool Pervasives.ref
>>
Set the reference to false
<<
| String of (string -> unit)
>>
Call the function with a string argument
<<
| Set_string of string Pervasives.ref
>>
Set the reference to the string argument
<<
| Int of (int -> unit)
>>
Call the function with an int argument
<<
| Set_int of int Pervasives.ref
>>
Set the reference to the int argument
<<
| Float of (float -> unit)
>>
Call the function with a float argument
<<
| Set_float of float Pervasives.ref
>>
Set the reference to the float argument
<<
| Tuple of spec list
>>
Take several arguments according to the spec list
<<
| Symbol of string list * (string -> unit)
>>
Take one of the symbols as argument and call the function with the symbol
<<
| Rest of (string -> unit)
>>
Stop interpreting keywords and call the function with each remaining
argument
The concrete type describing the behavior associated with a keyword.
<<
type key = string
>>
<<
type doc = string
>>
<<
type usage_msg = string
>>
<<
type anon_fun = string -> unit
>>
<<
val parse : (key * spec * doc) list -> anon_fun -> usage_msg -> unit
>>
Arg.parse speclist anon_fun usage_msg parses the command line. speclist is
a list of triples (key, spec, doc). key is the option keyword, it must start
with a '-' character. spec gives the option type and the function to call
when this option is found on the command line. doc is a one-line description
of this option. anon_fun is called on anonymous arguments. The functions in
spec and anon_fun are called in the same order as their arguments appear on
the command line.
If an error occurs, Arg.parse exits the program, after printing an error
message as follows:
- The reason for the error: unknown option, invalid or missing argument,
etc.
- usage_msg
- The list of options, each followed by the corresponding doc string.
For the user to be able to specify anonymous arguments starting with a -,
include for example ("-", String anon_fun, doc) in speclist.
By default, parse recognizes two unit options, -help and --help, which will
display usage_msg and the list of options, and exit the program. You can
override this behaviour by specifying your own -help and --help options in
speclist.
<<
val parse_argv :
?current:int Pervasives.ref ->
string array ->
(key * spec * doc) list -> anon_fun -> usage_msg -> unit
>>
Arg.parse_argv ~current args speclist anon_fun usage_msg parses the array
args as if it were the command line. It uses and updates the value of
~current (if given), or Arg.current. You must set it before calling
parse_argv. The initial value of current is the index of the program name
(argument 0) in the array. If an error occurs, Arg.parse_argv raises Arg.Bad
with the error message as argument. If option -help or --help is given,
Arg.parse_argv raises Arg.Help with the help message as argument.
<<
exception Help of string
>>
Raised by Arg.parse_argv when the user asks for help.
<<
exception Bad of string
>>
Functions in spec or anon_fun can raise Arg.Bad with an error message to
reject invalid arguments. Arg.Bad is also raised by Arg.parse_argv in case
of an error.
<<
val usage : (key * spec * doc) list -> usage_msg -> unit
>>
Arg.usage speclist usage_msg prints an error message including the list of
valid options. This is the same message that Arg.parse[20.1] prints in case
of error. speclist and usage_msg are the same as for Arg.parse.
<<
val align : (key * spec * doc) list -> (key * spec * doc) list
>>
Align the documentation strings by inserting spaces at the first space,
according to the length of the keyword. Use a space as the first character
in a doc string if you want to align the whole string. The doc strings
corresponding to Symbol arguments are not aligned.
<<
val current : int Pervasives.ref
>>
Position (in Sys.argv[20.34]) of the argument being processed. You can
change this value, e.g. to force Arg.parse[20.1] to skip some arguments.
Arg.parse[20.1] uses the initial value of Arg.current[20.1] as the index of
argument 0 (the program name) and starts parsing arguments at the next
element.
20.2 Module Array : Array operations.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val length : 'a array -> int
>>
Return the length (number of elements) of the given array.
<<
val get : 'a array -> int -> 'a
>>
Array.get a n returns the element number n of array a. The first element
has number 0. The last element has number Array.length a - 1. You can also
write a.(n) instead of Array.get a n.
Raise Invalid_argument "index out of bounds" if n is outside the range 0 to
(Array.length a - 1).
<<
val set : 'a array -> int -> 'a -> unit
>>
Array.set a n x modifies array a in place, replacing element number n with
x. You can also write a.(n) <- x instead of Array.set a n x.
Raise Invalid_argument "index out of bounds" if n is outside the range 0 to
Array.length a - 1.
<<
val make : int -> 'a -> 'a array
>>
Array.make n x returns a fresh array of length n, initialized with x. All
the elements of this new array are initially physically equal to x (in the
sense of the == predicate). Consequently, if x is mutable, it is shared
among all elements of the array, and modifying x through one of the array
entries will modify all other entries at the same time.
Raise Invalid_argument if n < 0 or n > Sys.max_array_length. If the value of
x is a floating-point number, then the maximum size is only
Sys.max_array_length / 2.
<<
val create : int -> 'a -> 'a array
>>
Deprecated. Array.create is an alias for Array.make[20.2].
<<
val init : int -> (int -> 'a) -> 'a array
>>
Array.init n f returns a fresh array of length n, with element number i
initialized to the result of f i. In other terms, Array.init n f tabulates
the results of f applied to the integers 0 to n-1.
Raise Invalid_argument if n < 0 or n > Sys.max_array_length. If the return
type of f is float, then the maximum size is only Sys.max_array_length / 2.
<<
val make_matrix : int -> int -> 'a -> 'a array array
>>
Array.make_matrix dimx dimy e returns a two-dimensional array (an array of
arrays) with first dimension dimx and second dimension dimy. All the
elements of this new matrix are initially physically equal to e. The element
(x,y) of a matrix m is accessed with the notation m.(x).(y).
Raise Invalid_argument if dimx or dimy is negative or greater than
Sys.max_array_length. If the value of e is a floating-point number, then the
maximum size is only Sys.max_array_length / 2.
<<
val create_matrix : int -> int -> 'a -> 'a array array
>>
Deprecated. Array.create_matrix is an alias for Array.make_matrix[20.2].
<<
val append : 'a array -> 'a array -> 'a array
>>
Array.append v1 v2 returns a fresh array containing the concatenation of
the arrays v1 and v2.
<<
val concat : 'a array list -> 'a array
>>
Same as Array.append, but concatenates a list of arrays.
<<
val sub : 'a array -> int -> int -> 'a array
>>
Array.sub a start len returns a fresh array of length len, containing the
elements number start to start + len - 1 of array a.
Raise Invalid_argument "Array.sub" if start and len do not designate a valid
subarray of a; that is, if start < 0, or len < 0, or start + len >
Array.length a.
<<
val copy : 'a array -> 'a array
>>
Array.copy a returns a copy of a, that is, a fresh array containing the
same elements as a.
<<
val fill : 'a array -> int -> int -> 'a -> unit
>>
Array.fill a ofs len x modifies the array a in place, storing x in elements
number ofs to ofs + len - 1.
Raise Invalid_argument "Array.fill" if ofs and len do not designate a valid
subarray of a.
<<
val blit : 'a array -> int -> 'a array -> int -> int -> unit
>>
Array.blit v1 o1 v2 o2 len copies len elements from array v1, starting at
element number o1, to array v2, starting at element number o2. It works
correctly even if v1 and v2 are the same array, and the source and
destination chunks overlap.
Raise Invalid_argument "Array.blit" if o1 and len do not designate a valid
subarray of v1, or if o2 and len do not designate a valid subarray of v2.
<<
val to_list : 'a array -> 'a list
>>
Array.to_list a returns the list of all the elements of a.
<<
val of_list : 'a list -> 'a array
>>
Array.of_list l returns a fresh array containing the elements of l.
<<
val iter : ('a -> unit) -> 'a array -> unit
>>
Array.iter f a applies function f in turn to all the elements of a. It is
equivalent to f a.(0); f a.(1); ...; f a.(Array.length a - 1); ().
<<
val map : ('a -> 'b) -> 'a array -> 'b array
>>
Array.map f a applies function f to all the elements of a, and builds an
array with the results returned by f: [| f a.(0); f a.(1); ...; f
a.(Array.length a - 1) |].
<<
val iteri : (int -> 'a -> unit) -> 'a array -> unit
>>
Same as Array.iter[20.2], but the function is applied to the index of the
element as first argument, and the element itself as second argument.
<<
val mapi : (int -> 'a -> 'b) -> 'a array -> 'b array
>>
Same as Array.map[20.2], but the function is applied to the index of the
element as first argument, and the element itself as second argument.
<<
val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b array -> 'a
>>
Array.fold_left f x a computes f (... (f (f x a.(0)) a.(1)) ...) a.(n-1),
where n is the length of the array a.
<<
val fold_right : ('a -> 'b -> 'b) -> 'a array -> 'b -> 'b
>>
Array.fold_right f a x computes f a.(0) (f a.(1) ( ... (f a.(n-1) x) ...)),
where n is the length of the array a.
Sorting
=======
<<
val sort : ('a -> 'a -> int) -> 'a array -> unit
>>
Sort an array in increasing order according to a comparison function. The
comparison function must return 0 if its arguments compare as equal, a
positive integer if the first is greater, and a negative integer if the
first is smaller (see below for a complete specification). For example,
Pervasives.compare[19.2] is a suitable comparison function, provided there
are no floating-point NaN values in the data. After calling Array.sort, the
array is sorted in place in increasing order. Array.sort is guaranteed to
run in constant heap space and (at most) logarithmic stack space.
The current implementation uses Heap Sort. It runs in constant stack space.
Specification of the comparison function: Let a be the array and cmp the
comparison function. The following must be true for all x, y, z in a :
- cmp x y > 0 if and only if cmp y x < 0
- if cmp x y >= 0 and cmp y z >= 0 then cmp x z >= 0
When Array.sort returns, a contains the same elements as before, reordered
in such a way that for all i and j valid indices of a :
- cmp a.(i) a.(j) >= 0 if and only if i >= j
<<
val stable_sort : ('a -> 'a -> int) -> 'a array -> unit
>>
Same as Array.sort[20.2], but the sorting algorithm is stable (i.e.
elements that compare equal are kept in their original order) and not
guaranteed to run in constant heap space.
The current implementation uses Merge Sort. It uses n/2 words of heap space,
where n is the length of the array. It is usually faster than the current
implementation of Array.sort[20.2].
<<
val fast_sort : ('a -> 'a -> int) -> 'a array -> unit
>>
Same as Array.sort[20.2] or Array.stable_sort[20.2], whichever is faster on
typical input.
20.3 Module Buffer : Extensible string buffers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements string buffers that automatically expand as necessary.
It provides accumulative concatenation of strings in quasi-linear time (instead
of quadratic time when strings are concatenated pairwise).
<<
type t
>>
The abstract type of buffers.
<<
val create : int -> t
>>
create n returns a fresh buffer, initially empty. The n parameter is the
initial size of the internal string that holds the buffer contents. That
string is automatically reallocated when more than n characters are stored
in the buffer, but shrinks back to n characters when reset is called. For
best performance, n should be of the same order of magnitude as the number
of characters that are expected to be stored in the buffer (for instance, 80
for a buffer that holds one output line). Nothing bad will happen if the
buffer grows beyond that limit, however. In doubt, take n = 16 for instance.
If n is not between 1 and Sys.max_string_length[20.34], it will be clipped
to that interval.
<<
val contents : t -> string
>>
Return a copy of the current contents of the buffer. The buffer itself is
unchanged.
<<
val sub : t -> int -> int -> string
>>
Buffer.sub b off len returns (a copy of) the substring of the current
contents of the buffer b starting at offset off of length len bytes. May
raise Invalid_argument if out of bounds request. The buffer itself is
unaffected.
<<
val nth : t -> int -> char
>>
get the n-th character of the buffer. Raise Invalid_argument if index out
of bounds
<<
val length : t -> int
>>
Return the number of characters currently contained in the buffer.
<<
val clear : t -> unit
>>
Empty the buffer.
<<
val reset : t -> unit
>>
Empty the buffer and deallocate the internal string holding the buffer
contents, replacing it with the initial internal string of length n that was
allocated by Buffer.create[20.3] n. For long-lived buffers that may have
grown a lot, reset allows faster reclamation of the space used by the
buffer.
<<
val add_char : t -> char -> unit
>>
add_char b c appends the character c at the end of the buffer b.
<<
val add_string : t -> string -> unit
>>
add_string b s appends the string s at the end of the buffer b.
<<
val add_substring : t -> string -> int -> int -> unit
>>
add_substring b s ofs len takes len characters from offset ofs in string s
and appends them at the end of the buffer b.
<<
val add_substitute : t -> (string -> string) -> string -> unit
>>
add_substitute b f s appends the string pattern s at the end of the buffer
b with substitution. The substitution process looks for variables into the
pattern and substitutes each variable name by its value, as obtained by
applying the mapping f to the variable name. Inside the string pattern, a
variable name immediately follows a non-escaped $ character and is one of
the following:
- a non empty sequence of alphanumeric or _ characters,
- an arbitrary sequence of characters enclosed by a pair of matching
parentheses or curly brackets. An escaped $ character is a $ that
immediately follows a backslash character; it then stands for a plain $.
Raise Not_found if the closing character of a parenthesized variable
cannot be found.
<<
val add_buffer : t -> t -> unit
>>
add_buffer b1 b2 appends the current contents of buffer b2 at the end of
buffer b1. b2 is not modified.
<<
val add_channel : t -> Pervasives.in_channel -> int -> unit
>>
add_channel b ic n reads exactly n character from the input channel ic and
stores them at the end of buffer b. Raise End_of_file if the channel
contains fewer than n characters.
<<
val output_buffer : Pervasives.out_channel -> t -> unit
>>
output_buffer oc b writes the current contents of buffer b on the output
channel oc.
20.4 Module Callback : Registering Caml values with the C runtime.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module allows Caml values to be registered with the C runtime under a
symbolic name, so that C code can later call back registered Caml functions, or
raise registered Caml exceptions.
<<
val register : string -> 'a -> unit
>>
Callback.register n v registers the value v under the name n. C code can
later retrieve a handle to v by calling caml_named_value(n).
<<
val register_exception : string -> exn -> unit
>>
Callback.register_exception n exn registers the exception contained in the
exception value exn under the name n. C code can later retrieve a handle to
the exception by calling caml_named_value(n). The exception value thus
obtained is suitable for passign as first argument to raise_constant or
raise_with_arg.
20.5 Module Char : Character operations.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
val code : char -> int
>>
Return the ASCII code of the argument.
<<
val chr : int -> char
>>
Return the character with the given ASCII code. Raise Invalid_argument
"Char.chr" if the argument is outside the range 0--255.
<<
val escaped : char -> string
>>
Return a string representing the given character, with special characters
escaped following the lexical conventions of Objective Caml.
<<
val lowercase : char -> char
>>
Convert the given character to its equivalent lowercase character.
<<
val uppercase : char -> char
>>
Convert the given character to its equivalent uppercase character.
<<
type t = char
>>
An alias for the type of characters.
<<
val compare : t -> t -> int
>>
The comparison function for characters, with the same specification as
Pervasives.compare[19.2]. Along with the type t, this function compare
allows the module Char to be passed as argument to the functors
Set.Make[20.28] and Map.Make[20.18].
20.6 Module Complex : Complex numbers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module provides arithmetic operations on complex numbers. Complex
numbers are represented by their real and imaginary parts (cartesian
representation). Each part is represented by a double-precision floating-point
number (type float).
<<
type t = {
re : float ;
im : float ;
}
>>
The type of complex numbers. re is the real part and im the imaginary part.
<<
val zero : t
>>
The complex number 0.
<<
val one : t
>>
The complex number 1.
<<
val i : t
>>
The complex number i.
<<
val neg : t -> t
>>
Unary negation.
<<
val conj : t -> t
>>
Conjugate: given the complex x + i.y, returns x - i.y.
<<
val add : t -> t -> t
>>
Addition
<<
val sub : t -> t -> t
>>
Subtraction
<<
val mul : t -> t -> t
>>
Multiplication
<<
val inv : t -> t
>>
Multiplicative inverse (1/z).
<<
val div : t -> t -> t
>>
Division
<<
val sqrt : t -> t
>>
Square root. The result x + i.y is such that x > 0 or x = 0 and y >= 0.
This function has a discontinuity along the negative real axis.
<<
val norm2 : t -> float
>>
Norm squared: given x + i.y, returns x^2 + y^2.
<<
val norm : t -> float
>>
Norm: given x + i.y, returns sqrt(x^2 + y^2).
<<
val arg : t -> float
>>
Argument. The argument of a complex number is the angle in the complex
plane between the positive real axis and a line passing through zero and the
number. This angle ranges from -pi to pi. This function has a discontinuity
along the negative real axis.
<<
val polar : float -> float -> t
>>
polar norm arg returns the complex having norm norm and argument arg.
<<
val exp : t -> t
>>
Exponentiation. exp z returns e to the z power.
<<
val log : t -> t
>>
Natural logarithm (in base e).
<<
val pow : t -> t -> t
>>
Power function. pow z1 z2 returns z1 to the z2 power.
20.7 Module Digest : MD5 message digest.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module provides functions to compute 128-bit "digests" of
arbitrary-length strings or files. The digests are of cryptographic quality: it
is very hard, given a digest, to forge a string having that digest. The
algorithm used is MD5.
<<
type t = string
>>
The type of digests: 16-character strings.
<<
val string : string -> t
>>
Return the digest of the given string.
<<
val substring : string -> int -> int -> t
>>
Digest.substring s ofs len returns the digest of the substring of s
starting at character number ofs and containing len characters.
<<
val channel : Pervasives.in_channel -> int -> t
>>
If len is nonnegative, Digest.channel ic len reads len characters from
channel ic and returns their digest, or raises End_of_file if end-of-file is
reached before len characters are read. If len is negative, Digest.channel
ic len reads all characters from ic until end-of-file is reached and return
their digest.
<<
val file : string -> t
>>
Return the digest of the file whose name is given.
<<
val output : Pervasives.out_channel -> t -> unit
>>
Write a digest on the given output channel.
<<
val input : Pervasives.in_channel -> t
>>
Read a digest from the given input channel.
<<
val to_hex : t -> string
>>
Return the printable hexadecimal representation of the given digest.
20.8 Module Filename : Operations on file names.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
val current_dir_name : string
>>
The conventional name for the current directory (e.g. . in Unix).
<<
val parent_dir_name : string
>>
The conventional name for the parent of the current directory (e.g. .. in
Unix).
<<
val concat : string -> string -> string
>>
concat dir file returns a file name that designates file file in directory
dir.
<<
val is_relative : string -> bool
>>
Return true if the file name is relative to the current directory, false if
it is absolute (i.e. in Unix, starts with /).
<<
val is_implicit : string -> bool
>>
Return true if the file name is relative and does not start with an
explicit reference to the current directory (./ or ../ in Unix), false if it
starts with an explicit reference to the root directory or the current
directory.
<<
val check_suffix : string -> string -> bool
>>
check_suffix name suff returns true if the filename name ends with the
suffix suff.
<<
val chop_suffix : string -> string -> string
>>
chop_suffix name suff removes the suffix suff from the filename name. The
behavior is undefined if name does not end with the suffix suff.
<<
val chop_extension : string -> string
>>
Return the given file name without its extension. The extension is the
shortest suffix starting with a period and not including a directory
separator, .xyz for instance.
Raise Invalid_argument if the given name does not contain an extension.
<<
val basename : string -> string
>>
Split a file name into directory name / base file name. concat (dirname
name) (basename name) returns a file name which is equivalent to name.
Moreover, after setting the current directory to dirname name (with
Sys.chdir[20.34]), references to basename name (which is a relative file
name) designate the same file as name before the call to Sys.chdir[20.34].
The result is not specified if the argument is not a valid file name (for
example, under Unix if there is a NUL character in the string).
<<
val dirname : string -> string
>>
See Filename.basename[20.8].
<<
val temp_file : string -> string -> string
>>
temp_file prefix suffix returns the name of a fresh temporary file in the
temporary directory. The base name of the temporary file is formed by
concatenating prefix, then a suitably chosen integer number, then suffix.
The temporary file is created empty, with permissions 0o600 (readable and
writable only by the file owner). The file is guaranteed to be different
from any other file that existed when temp_file was called.
<<
val open_temp_file :
?mode:Pervasives.open_flag list ->
string -> string -> string * Pervasives.out_channel
>>
Same as Filename.temp_file[20.8], but returns both the name of a fresh
temporary file, and an output channel opened (atomically) on this file. This
function is more secure than temp_file: there is no risk that the temporary
file will be modified (e.g. replaced by a symbolic link) before the program
opens it. The optional argument mode is a list of additional flags to
control the opening of the file. It can contain one or several of
Open_append, Open_binary, and Open_text. The default is [Open_text] (open in
text mode).
<<
val temp_dir_name : string
>>
The name of the temporary directory: Under Unix, the value of the TMPDIR
environment variable, or "/tmp" if the variable is not set. Under Windows,
the value of the TEMP environment variable, or "." if the variable is not
set.
<<
val quote : string -> string
>>
Return a quoted version of a file name, suitable for use as one argument in
a command line, escaping all meta-characters. Warning: under Windows, the
output is only suitable for use with programs that follow the standard
Windows quoting conventions.
20.9 Module Format : Pretty printing.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements a pretty-printing facility to format text within
"pretty-printing boxes". The pretty-printer breaks lines at specified break
hints, and indents lines according to the box structure.
For a gentle introduction to the basics of pretty-printing using Format, read
http://caml.inria.fr/resources/doc/guides/format.html[http://caml.inria.fr/reso
urces/doc/guides/format.html].
You may consider this module as providing an extension to the printf facility
to provide automatic line breaking. The addition of pretty-printing annotations
to your regular printf formats gives you fancy indentation and line breaks.
Pretty-printing annotations are described below in the documentation of the
function Format.fprintf[20.9].
You may also use the explicit box management and printing functions provided
by this module. This style is more basic but more verbose than the fprintf
concise formats.
For instance, the sequence open_box 0; print_string "x ="; print_space ();
print_int 1; close_box () that prints x = 1 within a pretty-printing box, can
be abbreviated as printf "@[%s@ %i@]" "x =" 1, or even shorter printf "@[x =@
%i@]" 1.
Rule of thumb for casual users of this library:
- use simple boxes (as obtained by open_box 0);
- use simple break hints (as obtained by print_cut () that outputs a simple
break hint, or by print_space () that outputs a space indicating a break
hint);
- once a box is opened, display its material with basic printing functions (e.
g. print_int and print_string);
- when the material for a box has been printed, call close_box () to close the
box;
- at the end of your routine, evaluate print_newline () to close all remaining
boxes and flush the pretty-printer.
The behaviour of pretty-printing commands is unspecified if there is no
opened pretty-printing box. Each box opened via one of the open_ functions
below must be closed using close_box for proper formatting. Otherwise, some of
the material printed in the boxes may not be output, or may be formatted
incorrectly.
In case of interactive use, the system closes all opened boxes and flushes
all pending text (as with the print_newline function) after each phrase. Each
phrase is therefore executed in the initial state of the pretty-printer.
Warning: the material output by the following functions is delayed in the
pretty-printer queue in order to compute the proper line breaking. Hence, you
should not mix calls to the printing functions of the basic I/O system with
calls to the functions of this module: this could result in some strange output
seemingly unrelated with the evaluation order of printing commands.
Boxes
=====
<<
val open_box : int -> unit
>>
open_box d opens a new pretty-printing box with offset d. This box is the
general purpose pretty-printing box. Material in this box is displayed
"horizontal or vertical": break hints inside the box may lead to a new line,
if there is no more room on the line to print the remainder of the box, or
if a new line may lead to a new indentation (demonstrating the indentation
of the box). When a new line is printed in the box, d is added to the
current indentation.
<<
val close_box : unit -> unit
>>
Closes the most recently opened pretty-printing box.
Formatting functions
====================
<<
val print_string : string -> unit
>>
print_string str prints str in the current box.
<<
val print_as : int -> string -> unit
>>
print_as len str prints str in the current box. The pretty-printer formats
str as if it were of length len.
<<
val print_int : int -> unit
>>
Prints an integer in the current box.
<<
val print_float : float -> unit
>>
Prints a floating point number in the current box.
<<
val print_char : char -> unit
>>
Prints a character in the current box.
<<
val print_bool : bool -> unit
>>
Prints a boolean in the current box.
Break hints
===========
<<
val print_space : unit -> unit
>>
print_space () is used to separate items (typically to print a space
between two words). It indicates that the line may be split at this point.
It either prints one space or splits the line. It is equivalent to
print_break 1 0.
<<
val print_cut : unit -> unit
>>
print_cut () is used to mark a good break position. It indicates that the
line may be split at this point. It either prints nothing or splits the
line. This allows line splitting at the current point, without printing
spaces or adding indentation. It is equivalent to print_break 0 0.
<<
val print_break : int -> int -> unit
>>
Inserts a break hint in a pretty-printing box. print_break nspaces offset
indicates that the line may be split (a newline character is printed) at
this point, if the contents of the current box does not fit on the current
line. If the line is split at that point, offset is added to the current
indentation. If the line is not split, nspaces spaces are printed.
<<
val print_flush : unit -> unit
>>
Flushes the pretty printer: all opened boxes are closed, and all pending
text is displayed.
<<
val print_newline : unit -> unit
>>
Equivalent to print_flush followed by a new line.
<<
val force_newline : unit -> unit
>>
Forces a newline in the current box. Not the normal way of pretty-printing,
you should prefer break hints.
<<
val print_if_newline : unit -> unit
>>
Executes the next formatting command if the preceding line has just been
split. Otherwise, ignore the next formatting command.
Margin
======
<<
val set_margin : int -> unit
>>
set_margin d sets the value of the right margin to d (in characters): this
value is used to detect line overflows that leads to split lines. Nothing
happens if d is smaller than 2. If d is too large, the right margin is set
to the maximum admissible value (which is greater than 10^10).
<<
val get_margin : unit -> int
>>
Returns the position of the right margin.
Maximum indentation limit
=========================
<<
val set_max_indent : int -> unit
>>
set_max_indent d sets the value of the maximum indentation limit to d (in
characters): once this limit is reached, boxes are rejected to the left, if
they do not fit on the current line. Nothing happens if d is smaller than 2.
If d is too large, the limit is set to the maximum admissible value (which
is greater than 10^10).
<<
val get_max_indent : unit -> int
>>
Return the value of the maximum indentation limit (in characters).
Formatting depth: maximum number of boxes allowed before ellipsis
=================================================================
<<
val set_max_boxes : int -> unit
>>
set_max_boxes max sets the maximum number of boxes simultaneously opened.
Material inside boxes nested deeper is printed as an ellipsis (more
precisely as the text returned by get_ellipsis_text ()). Nothing happens if
max is smaller than 2.
<<
val get_max_boxes : unit -> int
>>
Returns the maximum number of boxes allowed before ellipsis.
<<
val over_max_boxes : unit -> bool
>>
Tests if the maximum number of boxes allowed have already been opened.
Advanced formatting
===================
<<
val open_hbox : unit -> unit
>>
open_hbox () opens a new pretty-printing box. This box is "horizontal": the
line is not split in this box (new lines may still occur inside boxes nested
deeper).
<<
val open_vbox : int -> unit
>>
open_vbox d opens a new pretty-printing box with offset d. This box is
"vertical": every break hint inside this box leads to a new line. When a new
line is printed in the box, d is added to the current indentation.
<<
val open_hvbox : int -> unit
>>
open_hvbox d opens a new pretty-printing box with offset d. This box is
"horizontal-vertical": it behaves as an "horizontal" box if it fits on a
single line, otherwise it behaves as a "vertical" box. When a new line is
printed in the box, d is added to the current indentation.
<<
val open_hovbox : int -> unit
>>
open_hovbox d opens a new pretty-printing box with offset d. This box is
"horizontal or vertical": break hints inside this box may lead to a new
line, if there is no more room on the line to print the remainder of the
box. When a new line is printed in the box, d is added to the current
indentation.
Tabulations
===========
<<
val open_tbox : unit -> unit
>>
Opens a tabulation box.
<<
val close_tbox : unit -> unit
>>
Closes the most recently opened tabulation box.
<<
val print_tbreak : int -> int -> unit
>>
Break hint in a tabulation box. print_tbreak spaces offset moves the
insertion point to the next tabulation (spaces being added to this
position). Nothing occurs if insertion point is already on a tabulation
mark. If there is no next tabulation on the line, then a newline is printed
and the insertion point moves to the first tabulation of the box. If a new
line is printed, offset is added to the current indentation.
<<
val set_tab : unit -> unit
>>
Sets a tabulation mark at the current insertion point.
<<
val print_tab : unit -> unit
>>
print_tab () is equivalent to print_tbreak (0,0).
Ellipsis
========
<<
val set_ellipsis_text : string -> unit
>>
Set the text of the ellipsis printed when too many boxes are opened (a
single dot, ., by default).
<<
val get_ellipsis_text : unit -> string
>>
Return the text of the ellipsis.
Tags
====
<<
type tag = string
>>
Tags are used to decorate printed entities for user's defined purposes, e.g.
setting font and giving size indications for a display device, or marking
delimitations of semantics entities (e.g. HTML or TeX elements or terminal
escape sequences).
By default, those tags do not influence line breaking calculation: the tag
"markers" are not considered as part of the printing material that drives line
breaking (in other words, the length of those strings is considered as zero for
line breaking).
Thus, tag handling is in some sense transparent to pretty-printing and does
not interfere with usual pretty-printing. Hence, a single pretty printing
routine can output both simple "verbatim" material or richer decorated output
depending on the treatment of tags. By default, tags are not active, hence the
output is not decorated with tag information. Once set_tags is set to true, the
pretty printer engine honors tags and decorates the output accordingly.
When a tag has been opened (or closed), it is both and successively "printed"
and "marked". Printing a tag means calling a formatter specific function with
the name of the tag as argument: that "tag printing" function can then print
any regular material to the formatter (so that this material is enqueued as
usual in the formatter queue for further line-breaking computation). Marking a
tag means to output an arbitrary string (the "tag marker"), directly into the
output device of the formatter. Hence, the formatter specific "tag marking"
function must return the tag marker string associated to its tag argument.
Being flushed directly into the output device of the formatter, tag marker
strings are not considered as part of the printing material that drives line
breaking (in other words, the length of the strings corresponding to tag
markers is considered as zero for line breaking). In addition, advanced users
may take advantage of the specificity of tag markers to be precisely output
when the pretty printer has already decided where to break the lines, and
precisely when the queue is flushed into the output device.
In the spirit of HTML tags, the default tag marking functions output tags
enclosed in "<" and ">": hence, the opening marker of tag t is "<t>" and the
closing marker "</t>".
Default tag printing functions just do nothing.
Tag marking and tag printing functions are user definable and can be set by
calling set_formatter_tag_functions.
<<
val open_tag : tag -> unit
>>
open_tag t opens the tag named t; the print_open_tag function of the
formatter is called with t as argument; the tag marker mark_open_tag t will
be flushed into the output device of the formatter.
<<
val close_tag : unit -> unit
>>
close_tag () closes the most recently opened tag t. In addition, the
print_close_tag function of the formatter is called with t as argument. The
marker mark_close_tag t will be flushed into the output device of the
formatter.
<<
val set_tags : bool -> unit
>>
set_tags b turns on or off the treatment of tags (default is off).
<<
val set_print_tags : bool -> unit
>>
<<
val set_mark_tags : bool -> unit
>>
set_print_tags b turns on or off the printing of tags, while set_mark_tags
b turns on or off the output of tag markers.
<<
val get_print_tags : unit -> bool
>>
<<
val get_mark_tags : unit -> bool
>>
Return the current status of tags printing and tags marking.
Redirecting formatter output
============================
<<
val set_formatter_out_channel : Pervasives.out_channel -> unit
>>
Redirect the pretty-printer output to the given channel.
<<
val set_formatter_output_functions :
(string -> int -> int -> unit) -> (unit -> unit) -> unit
>>
set_formatter_output_functions out flush redirects the pretty-printer
output to the functions out and flush.
The out function performs the pretty-printer output. It is called with a
string s, a start position p, and a number of characters n; it is supposed
to output characters p to p + n - 1 of s. The flush function is called
whenever the pretty-printer is flushed using print_flush or print_newline.
<<
val get_formatter_output_functions :
unit -> (string -> int -> int -> unit) * (unit -> unit)
>>
Return the current output functions of the pretty-printer.
Changing the meaning of printing tags
=====================================
<<
type formatter_tag_functions = {
mark_open_tag : tag -> string ;
mark_close_tag : tag -> string ;
print_open_tag : tag -> unit ;
print_close_tag : tag -> unit ;
}
>>
The tag handling functions specific to a formatter: mark versions are the
"tag marking" functions that associate a string marker to a tag in order for
the pretty-printing engine to flush those markers as 0 length tokens in the
output device of the formatter. print versions are the "tag printing"
functions that can perform regular printing when a tag is closed or opened.
<<
val set_formatter_tag_functions : formatter_tag_functions -> unit
>>
set_formatter_tag_functions tag_funs changes the meaning of opening and
closing tags to use the functions in tag_funs.
When opening a tag name t, the string t is passed to the opening tag marking
function (the mark_open_tag field of the record tag_funs), that must return the
opening tag marker for that name. When the next call to close_tag () happens,
the tag name t is sent back to the closing tag marking function (the
mark_close_tag field of record tag_funs), that must return a closing tag marker
for that name.
The print_ field of the record contains the functions that are called at tag
opening and tag closing time, to output regular material in the pretty-printer
queue.
<<
val get_formatter_tag_functions : unit -> formatter_tag_functions
>>
Return the current tag functions of the pretty-printer.
Changing the meaning of pretty printing (indentation, line breaking, and
========================================================================
printing material)
==================
<<
val set_all_formatter_output_functions :
out:(string -> int -> int -> unit) ->
flush:(unit -> unit) ->
newline:(unit -> unit) -> spaces:(int -> unit) -> unit
>>
set_all_formatter_output_functions out flush outnewline outspace redirects
the pretty-printer output to the functions out and flush as described in
set_formatter_output_functions. In addition, the pretty-printer function
that outputs a newline is set to the function outnewline and the function
that outputs indentation spaces is set to the function outspace.
This way, you can change the meaning of indentation (which can be something
else than just printing space characters) and the meaning of new lines
opening (which can be connected to any other action needed by the
application at hand). The two functions outspace and outnewline are normally
connected to out and flush: respective default values for outspace and
outnewline are out (String.make n ' ') 0 n and out "\n" 0 1.
<<
val get_all_formatter_output_functions :
unit ->
(string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) *
(int -> unit)
>>
Return the current output functions of the pretty-printer, including line
breaking and indentation functions.
Multiple formatted output
=========================
<<
type formatter
>>
Abstract data type corresponding to a pretty-printer (also called a
formatter) and all its machinery. Defining new pretty-printers permits the
output of material in parallel on several channels. Parameters of a
pretty-printer are local to this pretty-printer: margin, maximum indentation
limit, maximum number of boxes simultaneously opened, ellipsis, and so on,
are specific to each pretty-printer and may be fixed independently. Given an
output channel oc, a new formatter writing to that channel is obtained by
calling formatter_of_out_channel oc. Alternatively, the make_formatter
function allocates a new formatter with explicit output and flushing
functions (convenient to output material to strings for instance).
<<
val formatter_of_out_channel : Pervasives.out_channel -> formatter
>>
formatter_of_out_channel oc returns a new formatter that writes to the
corresponding channel oc.
<<
val std_formatter : formatter
>>
The standard formatter used by the formatting functions above. It is
defined as formatter_of_out_channel stdout.
<<
val err_formatter : formatter
>>
A formatter to use with formatting functions below for output to standard
error. It is defined as formatter_of_out_channel stderr.
<<
val formatter_of_buffer : Buffer.t -> formatter
>>
formatter_of_buffer b returns a new formatter writing to buffer b. As
usual, the formatter has to be flushed at the end of pretty printing, using
pp_print_flush or pp_print_newline, to display all the pending material.
<<
val stdbuf : Buffer.t
>>
The string buffer in which str_formatter writes.
<<
val str_formatter : formatter
>>
A formatter to use with formatting functions below for output to the stdbuf
string buffer. str_formatter is defined as formatter_of_buffer stdbuf.
<<
val flush_str_formatter : unit -> string
>>
Returns the material printed with str_formatter, flushes the formatter and
resets the corresponding buffer.
<<
val make_formatter :
(string -> int -> int -> unit) -> (unit -> unit) -> formatter
>>
make_formatter out flush returns a new formatter that writes according to
the output function out, and the flushing function flush. Hence, a formatter
to the out channel oc is returned by make_formatter (output oc) (fun () ->
flush oc).
Basic functions to use with formatters
======================================
<<
val pp_open_hbox : formatter -> unit -> unit
>>
<<
val pp_open_vbox : formatter -> int -> unit
>>
<<
val pp_open_hvbox : formatter -> int -> unit
>>
<<
val pp_open_hovbox : formatter -> int -> unit
>>
<<
val pp_open_box : formatter -> int -> unit
>>
<<
val pp_close_box : formatter -> unit -> unit
>>
<<
val pp_open_tag : formatter -> string -> unit
>>
<<
val pp_close_tag : formatter -> unit -> unit
>>
<<
val pp_print_string : formatter -> string -> unit
>>
<<
val pp_print_as : formatter -> int -> string -> unit
>>
<<
val pp_print_int : formatter -> int -> unit
>>
<<
val pp_print_float : formatter -> float -> unit
>>
<<
val pp_print_char : formatter -> char -> unit
>>
<<
val pp_print_bool : formatter -> bool -> unit
>>
<<
val pp_print_break : formatter -> int -> int -> unit
>>
<<
val pp_print_cut : formatter -> unit -> unit
>>
<<
val pp_print_space : formatter -> unit -> unit
>>
<<
val pp_force_newline : formatter -> unit -> unit
>>
<<
val pp_print_flush : formatter -> unit -> unit
>>
<<
val pp_print_newline : formatter -> unit -> unit
>>
<<
val pp_print_if_newline : formatter -> unit -> unit
>>
<<
val pp_open_tbox : formatter -> unit -> unit
>>
<<
val pp_close_tbox : formatter -> unit -> unit
>>
<<
val pp_print_tbreak : formatter -> int -> int -> unit
>>
<<
val pp_set_tab : formatter -> unit -> unit
>>
<<
val pp_print_tab : formatter -> unit -> unit
>>
<<
val pp_set_tags : formatter -> bool -> unit
>>
<<
val pp_set_print_tags : formatter -> bool -> unit
>>
<<
val pp_set_mark_tags : formatter -> bool -> unit
>>
<<
val pp_get_print_tags : formatter -> unit -> bool
>>
<<
val pp_get_mark_tags : formatter -> unit -> bool
>>
<<
val pp_set_margin : formatter -> int -> unit
>>
<<
val pp_get_margin : formatter -> unit -> int
>>
<<
val pp_set_max_indent : formatter -> int -> unit
>>
<<
val pp_get_max_indent : formatter -> unit -> int
>>
<<
val pp_set_max_boxes : formatter -> int -> unit
>>
<<
val pp_get_max_boxes : formatter -> unit -> int
>>
<<
val pp_over_max_boxes : formatter -> unit -> bool
>>
<<
val pp_set_ellipsis_text : formatter -> string -> unit
>>
<<
val pp_get_ellipsis_text : formatter -> unit -> string
>>
<<
val pp_set_formatter_out_channel :
formatter -> Pervasives.out_channel -> unit
>>
<<
val pp_set_formatter_output_functions :
formatter -> (string -> int -> int -> unit) -> (unit -> unit) -> unit
>>
<<
val pp_get_formatter_output_functions :
formatter -> unit -> (string -> int -> int -> unit) * (unit -> unit)
>>
<<
val pp_set_all_formatter_output_functions :
formatter ->
out:(string -> int -> int -> unit) ->
flush:(unit -> unit) ->
newline:(unit -> unit) -> spaces:(int -> unit) -> unit
>>
<<
val pp_get_all_formatter_output_functions :
formatter ->
unit ->
(string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) *
(int -> unit)
>>
<<
val pp_set_formatter_tag_functions :
formatter -> formatter_tag_functions -> unit
>>
<<
val pp_get_formatter_tag_functions :
formatter -> unit -> formatter_tag_functions
>>
These functions are the basic ones: usual functions operating on the
standard formatter are defined via partial evaluation of these primitives.
For instance, print_string is equal to pp_print_string std_formatter.
printf like functions for pretty-printing.
==========================================
<<
val fprintf : formatter -> ('a, formatter, unit) Pervasives.format -> 'a
>>
fprintf ff format arg1 ... argN formats the arguments arg1 to argN
according to the format string format, and outputs the resulting string on
the formatter ff. The format is a character string which contains three
types of objects: plain characters and conversion specifications as
specified in the printf module, and pretty-printing indications. The
pretty-printing indication characters are introduced by a @ character, and
their meanings are:
- @[: open a pretty-printing box. The type and offset of the box may be
optionally specified with the following syntax: the < character, followed
by an optional box type indication, then an optional integer offset, and
the closing > character. Box type is one of h, v, hv, b, or hov, which
stand respectively for an horizontal box, a vertical box, an
"horizontal-vertical" box, or an "horizontal or vertical" box (b standing
for an "horizontal or vertical" box demonstrating indentation and hov
standing for a regular"horizontal or vertical" box). For instance, @[<hov
2> opens an "horizontal or vertical" box with indentation 2 as obtained
with open_hovbox 2. For more details about boxes, see the various box
opening functions open_*box.
- @]: close the most recently opened pretty-printing box.
- @,: output a good break as with print_cut ().
- @ : output a space, as with print_space ().
- @\n: force a newline, as with force_newline ().
- @;: output a good break as with print_break. The nspaces and offset
parameters of the break may be optionally specified with the following
syntax: the < character, followed by an integer nspaces value, then an
integer offset, and a closing > character. If no parameters are provided,
the good break defaults to a space.
- @?: flush the pretty printer as with print_flush (). This is equivalent
to the conversion %!.
- @.: flush the pretty printer and output a new line, as with print_newline
().
- @<n>: print the following item as if it were of length n. Hence, printf
"@<0>%s" arg is equivalent to print_as 0 arg. If @<n> is not followed by
a conversion specification, then the following character of the format is
printed as if it were of length n.
- @{: open a tag. The name of the tag may be optionally specified with the
following syntax: the < character, followed by an optional string
specification, and the closing > character. The string specification is
any character string that does not contain the closing character '>'. If
omitted, the tag name defaults to the empty string. For more details
about tags, see the functions open_tag and close_tag.
- @}: close the most recently opened tag.
- @@: print a plain @ character.
Example: printf "@[%s@ %d@]" "x =" 1 is equivalent to open_box ();
print_string "x ="; print_space (); print_int 1; close_box (). It prints x =
1 within a pretty-printing box.
<<
val printf : ('a, formatter, unit) Pervasives.format -> 'a
>>
Same as fprintf above, but output on std_formatter.
<<
val eprintf : ('a, formatter, unit) Pervasives.format -> 'a
>>
Same as fprintf above, but output on err_formatter.
<<
val sprintf : ('a, unit, string) Pervasives.format -> 'a
>>
Same as printf above, but instead of printing on a formatter, returns a
string containing the result of formatting the arguments. Note that the
pretty-printer queue is flushed at the end of each call to sprintf.
In case of multiple and related calls to sprintf to output material on a
single string, you should consider using fprintf with a formatter writing to
a buffer: flushing the buffer at the end of pretty-printing returns the
desired string. You can also use the predefined formatter str_formatter and
call flush_str_formatter () to get the result.
<<
val bprintf : Buffer.t -> ('a, formatter, unit) Pervasives.format -> 'a
>>
Same as sprintf above, but instead of printing on a string, writes into the
given extensible buffer. As for sprintf, the pretty-printer queue is flushed
at the end of each call to bprintf.
In case of multiple and related calls to bprintf to output material on the
same buffer b, you should consider using fprintf with a formatter writing to
the buffer b (as obtained by formatter_of_buffer b), otherwise the repeated
flushes of the pretty-printer queue would result in unexpected and badly
formatted output.
<<
val kfprintf :
(formatter -> 'a) ->
formatter -> ('b, formatter, unit, 'a) Pervasives.format4 -> 'b
>>
Same as fprintf above, but instead of returning immediately, passes the
formatter to its first argument at the end of printing.
<<
val ifprintf : formatter -> ('a, formatter, unit) Pervasives.format -> 'a
>>
Same as fprintf above, but does not print anything. Useful to ignore some
material when conditionally printing.
<<
val ksprintf :
(string -> 'a) -> ('b, unit, string, 'a) Pervasives.format4 -> 'b
>>
Same as sprintf above, but instead of returning the string, passes it to
the first argument.
<<
val kprintf :
(string -> 'a) -> ('b, unit, string, 'a) Pervasives.format4 -> 'b
>>
A deprecated synonym for ksprintf.
20.10 Module Gc : Memory management control and statistics; finalised values.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
type stat = {
minor_words : float ;
>>
Number of words allocated in the minor heap since the program was started.
This number is accurate in byte-code programs, but only an approximation in
programs compiled to native code.
<<
promoted_words : float ;
>>
Number of words allocated in the minor heap that survived a minor
collection and were moved to the major heap since the program was started.
<<
major_words : float ;
>>
Number of words allocated in the major heap, including the promoted words,
since the program was started.
<<
minor_collections : int ;
>>
Number of minor collections since the program was started.
<<
major_collections : int ;
>>
Number of major collection cycles completed since the program was started.
<<
heap_words : int ;
>>
Total size of the major heap, in words.
<<
heap_chunks : int ;
>>
Number of contiguous pieces of memory that make up the major heap.
<<
live_words : int ;
>>
Number of words of live data in the major heap, including the header words.
<<
live_blocks : int ;
>>
Number of live blocks in the major heap.
<<
free_words : int ;
>>
Number of words in the free list.
<<
free_blocks : int ;
>>
Number of blocks in the free list.
<<
largest_free : int ;
>>
Size (in words) of the largest block in the free list.
<<
fragments : int ;
>>
Number of wasted words due to fragmentation. These are 1-words free blocks
placed between two live blocks. They are not available for allocation.
<<
compactions : int ;
>>
Number of heap compactions since the program was started.
<<
top_heap_words : int ;
>>
Maximum size reached by the major heap, in words.
<<
}
>>
The memory management counters are returned in a stat record.
The total amount of memory allocated by the program since it was started is
(in words) minor_words + major_words - promoted_words. Multiply by the word
size (4 on a 32-bit machine, 8 on a 64-bit machine) to get the number of
bytes.
<<
type control = {
mutable minor_heap_size : int ;
>>
The size (in words) of the minor heap. Changing this parameter will trigger
a minor collection. Default: 32k.
<<
mutable major_heap_increment : int ;
>>
The minimum number of words to add to the major heap when increasing it.
Default: 62k.
<<
mutable space_overhead : int ;
>>
The major GC speed is computed from this parameter. This is the memory that
will be "wasted" because the GC does not immediatly collect unreachable
blocks. It is expressed as a percentage of the memory used for live data.
The GC will work more (use more CPU time and collect blocks more eagerly) if
space_overhead is smaller. Default: 80.
<<
mutable verbose : int ;
>>
This value controls the GC messages on standard error output. It is a sum
of some of the following flags, to print messages on the corresponding
events:
- 0x001 Start of major GC cycle.
- 0x002 Minor collection and major GC slice.
- 0x004 Growing and shrinking of the heap.
- 0x008 Resizing of stacks and memory manager tables.
- 0x010 Heap compaction.
- 0x020 Change of GC parameters.
- 0x040 Computation of major GC slice size.
- 0x080 Calling of finalisation functions.
- 0x100 Bytecode executable search at start-up.
- 0x200 Computation of compaction triggering condition. Default: 0.
<<
mutable max_overhead : int ;
>>
Heap compaction is triggered when the estimated amount of "wasted" memory
is more than max_overhead percent of the amount of live data. If
max_overhead is set to 0, heap compaction is triggered at the end of each
major GC cycle (this setting is intended for testing purposes only). If
max_overhead >= 1000000, compaction is never triggered. Default: 500.
<<
mutable stack_limit : int ;
>>
The maximum size of the stack (in words). This is only relevant to the
byte-code runtime, as the native code runtime uses the operating system's
stack. Default: 256k.
<<
}
>>
The GC parameters are given as a control record. Note that these parameters
can also be initialised by setting the OCAMLRUNPARAM environment variable.
See the documentation of ocamlrun.
<<
val stat : unit -> stat
>>
Return the current values of the memory management counters in a stat
record. This function examines every heap block to get the statistics.
<<
val quick_stat : unit -> stat
>>
Same as stat except that live_words, live_blocks, free_words, free_blocks,
largest_free, and fragments are set to 0. This function is much faster than
stat because it does not need to go through the heap.
<<
val counters : unit -> float * float * float
>>
Return (minor_words, promoted_words, major_words). This function is as fast
at quick_stat.
<<
val get : unit -> control
>>
Return the current values of the GC parameters in a control record.
<<
val set : control -> unit
>>
set r changes the GC parameters according to the control record r. The
normal usage is: Gc.set { (Gc.get()) with Gc.verbose = 0x00d }
<<
val minor : unit -> unit
>>
Trigger a minor collection.
<<
val major_slice : int -> int
>>
Do a minor collection and a slice of major collection. The argument is the
size of the slice, 0 to use the automatically-computed slice size. In all
cases, the result is the computed slice size.
<<
val major : unit -> unit
>>
Do a minor collection and finish the current major collection cycle.
<<
val full_major : unit -> unit
>>
Do a minor collection, finish the current major collection cycle, and
perform a complete new cycle. This will collect all currently unreachable
blocks.
<<
val compact : unit -> unit
>>
Perform a full major collection and compact the heap. Note that heap
compaction is a lengthy operation.
<<
val print_stat : Pervasives.out_channel -> unit
>>
Print the current values of the memory management counters (in
human-readable form) into the channel argument.
<<
val allocated_bytes : unit -> float
>>
Return the total number of bytes allocated since the program was started.
It is returned as a float to avoid overflow problems with int on 32-bit
machines.
<<
val finalise : ('a -> unit) -> 'a -> unit
>>
finalise f v registers f as a finalisation function for v. v must be
heap-allocated. f will be called with v as argument at some point between
the first time v becomes unreachable and the time v is collected by the GC.
Several functions can be registered for the same value, or even several
instances of the same function. Each instance will be called once (or never,
if the program terminates before v becomes unreachable).
The GC will call the finalisation functions in the order of deallocation.
When several values become unreachable at the same time (i.e. during the
same GC cycle), the finalisation functions will be called in the reverse
order of the corresponding calls to finalise. If finalise is called in the
same order as the values are allocated, that means each value is finalised
before the values it depends upon. Of course, this becomes false if
additional dependencies are introduced by assignments.
Anything reachable from the closure of finalisation functions is considered
reachable, so the following code will not work as expected:
- let v = ... in Gc.finalise (fun x -> ...) v
Instead you should write:
- let f = fun x -> ... ;; let v = ... in Gc.finalise f v
The f function can use all features of O'Caml, including assignments that
make the value reachable again. It can also loop forever (in this case, the
other finalisation functions will be called during the execution of f). It
can call finalise on v or other values to register other functions or even
itself. It can raise an exception; in this case the exception will interrupt
whatever the program was doing when the function was called.
finalise will raise Invalid_argument if v is not heap-allocated. Some
examples of values that are not heap-allocated are integers, constant
constructors, booleans, the empty array, the empty list, the unit value. The
exact list of what is heap-allocated or not is implementation-dependent.
Some constant values can be heap-allocated but never deallocated during the
lifetime of the program, for example a list of integer constants; this is
also implementation-dependent. You should also be aware that compiler
optimisations may duplicate some immutable values, for example
floating-point numbers when stored into arrays, so they can be finalised and
collected while another copy is still in use by the program.
The results of calling String.make[20.33], String.create[20.33],
Array.make[20.2], and Pervasives.ref[19.2] are guaranteed to be
heap-allocated and non-constant except when the length argument is 0.
<<
val finalise_release : unit -> unit
>>
A finalisation function may call finalise_release to tell the GC that it
can launch the next finalisation function without waiting for the current
one to return.
<<
type alarm
>>
An alarm is a piece of data that calls a user function at the end of each
major GC cycle. The following functions are provided to create and delete
alarms.
<<
val create_alarm : (unit -> unit) -> alarm
>>
create_alarm f will arrange for f to be called at the end of each major GC
cycle, starting with the current cycle or the next one. A value of type
alarm is returned that you can use to call delete_alarm.
<<
val delete_alarm : alarm -> unit
>>
delete_alarm a will stop the calls to the function associated to a. Calling
delete_alarm a again has no effect.
20.11 Module Genlex : A generic lexical analyzer.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements a simple "standard" lexical analyzer, presented as a
function from character streams to token streams. It implements roughly the
lexical conventions of Caml, but is parameterized by the set of keywords of
your language.
Example: a lexer suitable for a desk calculator is obtained by
<<
let lexer = make_lexer ["+";"-";"*";"/";"let";"="; "("; ")"]
>>
The associated parser would be a function from token stream to, for instance,
int, and would have rules such as:
<<
let parse_expr = parser
[< 'Int n >] -> n
| [< 'Kwd "("; n = parse_expr; 'Kwd ")" >] -> n
| [< n1 = parse_expr; n2 = parse_remainder n1 >] -> n2
and parse_remainder n1 = parser
[< 'Kwd "+"; n2 = parse_expr >] -> n1+n2
| ...
>>
<<
type token =
| Kwd of string
| Ident of string
| Int of int
| Float of float
| String of string
| Char of char
>>
The type of tokens. The lexical classes are: Int and Float for integer and
floating-point numbers; String for string literals, enclosed in double
quotes; Char for character literals, enclosed in single quotes; Ident for
identifiers (either sequences of letters, digits, underscores and quotes, or
sequences of "operator characters" such as +, *, etc); and Kwd for keywords
(either identifiers or single "special characters" such as (, }, etc).
<<
val make_lexer : string list -> char Stream.t -> token Stream.t
>>
Construct the lexer function. The first argument is the list of keywords.
An identifier s is returned as Kwd s if s belongs to this list, and as Ident
s otherwise. A special character s is returned as Kwd s if s belongs to this
list, and cause a lexical error (exception Parse_error) otherwise. Blanks
and newlines are skipped. Comments delimited by (* and *) are skipped as
well, and can be nested.
20.12 Module Hashtbl : Hash tables and hash functions.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Hash tables are hashed association tables, with in-place modification.
Generic interface
=================
<<
type ('a, 'b) t
>>
The type of hash tables from type 'a to type 'b.
<<
val create : int -> ('a, 'b) t
>>
Hashtbl.create n creates a new, empty hash table, with initial size n. For
best results, n should be on the order of the expected number of elements
that will be in the table. The table grows as needed, so n is just an
initial guess.
<<
val clear : ('a, 'b) t -> unit
>>
Empty a hash table.
<<
val add : ('a, 'b) t -> 'a -> 'b -> unit
>>
Hashtbl.add tbl x y adds a binding of x to y in table tbl. Previous
bindings for x are not removed, but simply hidden. That is, after performing
Hashtbl.remove[20.12] tbl x, the previous binding for x, if any, is
restored. (Same behavior as with association lists.)
<<
val copy : ('a, 'b) t -> ('a, 'b) t
>>
Return a copy of the given hashtable.
<<
val find : ('a, 'b) t -> 'a -> 'b
>>
Hashtbl.find tbl x returns the current binding of x in tbl, or raises
Not_found if no such binding exists.
<<
val find_all : ('a, 'b) t -> 'a -> 'b list
>>
Hashtbl.find_all tbl x returns the list of all data associated with x in
tbl. The current binding is returned first, then the previous bindings, in
reverse order of introduction in the table.
<<
val mem : ('a, 'b) t -> 'a -> bool
>>
Hashtbl.mem tbl x checks if x is bound in tbl.
<<
val remove : ('a, 'b) t -> 'a -> unit
>>
Hashtbl.remove tbl x removes the current binding of x in tbl, restoring the
previous binding if it exists. It does nothing if x is not bound in tbl.
<<
val replace : ('a, 'b) t -> 'a -> 'b -> unit
>>
Hashtbl.replace tbl x y replaces the current binding of x in tbl by a
binding of x to y. If x is unbound in tbl, a binding of x to y is added to
tbl. This is functionally equivalent to Hashtbl.remove[20.12] tbl x followed
by Hashtbl.add[20.12] tbl x y.
<<
val iter : ('a -> 'b -> unit) -> ('a, 'b) t -> unit
>>
Hashtbl.iter f tbl applies f to all bindings in table tbl. f receives the
key as first argument, and the associated value as second argument. Each
binding is presented exactly once to f. The order in which the bindings are
passed to f is unspecified. However, if the table contains several bindings
for the same key, they are passed to f in reverse order of introduction,
that is, the most recent binding is passed first.
<<
val fold : ('a -> 'b -> 'c -> 'c) -> ('a, 'b) t -> 'c -> 'c
>>
Hashtbl.fold f tbl init computes (f kN dN ... (f k1 d1 init)...), where k1
... kN are the keys of all bindings in tbl, and d1 ... dN are the associated
values. Each binding is presented exactly once to f. The order in which the
bindings are passed to f is unspecified. However, if the table contains
several bindings for the same key, they are passed to f in reverse order of
introduction, that is, the most recent binding is passed first.
<<
val length : ('a, 'b) t -> int
>>
Hashtbl.length tbl returns the number of bindings in tbl. Multiple bindings
are counted multiply, so Hashtbl.length gives the number of times
Hashtbl.iter calls its first argument.
Functorial interface
====================
<<
module type HashedType = >>
sig
<<
type t
>>
The type of the hashtable keys.
<<
val equal : t -> t -> bool
>>
The equality predicate used to compare keys.
<<
val hash : t -> int
>>
A hashing function on keys. It must be such that if two keys are equal
according to equal, then they have identical hash values as computed by
hash. Examples: suitable (equal, hash) pairs for arbitrary key types
include ((=), Hashtbl.hash[20.12]) for comparing objects by structure,
((fun x y -> compare x y = 0), Hashtbl.hash[20.12]) for comparing objects
by structure and handling Pervasives.nan[19.2] correctly, and ((==),
Hashtbl.hash[20.12]) for comparing objects by addresses (e.g. for cyclic
keys).
end
The input signature of the functor Hashtbl.Make[20.12].
<<
module type S = >>
sig
<<
type key
>>
<<
type 'a t
>>
<<
val create : int -> 'a t
>>
<<
val clear : 'a t -> unit
>>
<<
val copy : 'a t -> 'a t
>>
<<
val add : 'a t -> key -> 'a -> unit
>>
<<
val remove : 'a t -> key -> unit
>>
<<
val find : 'a t -> key -> 'a
>>
<<
val find_all : 'a t -> key -> 'a list
>>
<<
val replace : 'a t -> key -> 'a -> unit
>>
<<
val mem : 'a t -> key -> bool
>>
<<
val iter : (key -> 'a -> unit) -> 'a t -> unit
>>
<<
val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
>>
<<
val length : 'a t -> int
>>
end
The output signature of the functor Hashtbl.Make[20.12].
<<
module Make : >>
functor (H : HashedType) -> S with type key = H.t
Functor building an implementation of the hashtable structure. The functor
Hashtbl.Make returns a structure containing a type key of keys and a type 'a
t of hash tables associating data of type 'a to keys of type key. The
operations perform similarly to those of the generic interface, but use the
hashing and equality functions specified in the functor argument H instead
of generic equality and hashing.
The polymorphic hash primitive
==============================
<<
val hash : 'a -> int
>>
Hashtbl.hash x associates a positive integer to any value of any type. It
is guaranteed that if x = y or Pervasives.compare x y = 0, then hash x =
hash y. Moreover, hash always terminates, even on cyclic structures.
<<
val hash_param : int -> int -> 'a -> int
>>
Hashtbl.hash_param n m x computes a hash value for x, with the same
properties as for hash. The two extra parameters n and m give more precise
control over hashing. Hashing performs a depth-first, right-to-left
traversal of the structure x, stopping after n meaningful nodes were
encountered, or m nodes, meaningful or not, were encountered. Meaningful
nodes are: integers; floating-point numbers; strings; characters; booleans;
and constant constructors. Larger values of m and n means that more nodes
are taken into account to compute the final hash value, and therefore
collisions are less likely to happen. However, hashing takes longer. The
parameters m and n govern the tradeoff between accuracy and speed.
20.13 Module Int32 : 32-bit integers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module provides operations on the type int32 of signed 32-bit integers.
Unlike the built-in int type, the type int32 is guaranteed to be exactly 32-bit
wide on all platforms. All arithmetic operations over int32 are taken modulo
2^32.
Performance notice: values of type int32 occupy more memory space than values
of type int, and arithmetic operations on int32 are generally slower than those
on int. Use int32 only when the application requires exact 32-bit arithmetic.
<<
val zero : int32
>>
The 32-bit integer 0.
<<
val one : int32
>>
The 32-bit integer 1.
<<
val minus_one : int32
>>
The 32-bit integer -1.
<<
val neg : int32 -> int32
>>
Unary negation.
<<
val add : int32 -> int32 -> int32
>>
Addition.
<<
val sub : int32 -> int32 -> int32
>>
Subtraction.
<<
val mul : int32 -> int32 -> int32
>>
Multiplication.
<<
val div : int32 -> int32 -> int32
>>
Integer division. Raise Division_by_zero if the second argument is zero.
This division rounds the real quotient of its arguments towards zero, as
specified for Pervasives.(/)[19.2].
<<
val rem : int32 -> int32 -> int32
>>
Integer remainder. If y is not zero, the result of Int32.rem x y satisfies
the following property: x = Int32.add (Int32.mul (Int32.div x y) y)
(Int32.rem x y). If y = 0, Int32.rem x y raises Division_by_zero.
<<
val succ : int32 -> int32
>>
Successor. Int32.succ x is Int32.add x Int32.one.
<<
val pred : int32 -> int32
>>
Predecessor. Int32.pred x is Int32.sub x Int32.one.
<<
val abs : int32 -> int32
>>
Return the absolute value of its argument.
<<
val max_int : int32
>>
The greatest representable 32-bit integer, 2^31 - 1.
<<
val min_int : int32
>>
The smallest representable 32-bit integer, -2^31.
<<
val logand : int32 -> int32 -> int32
>>
Bitwise logical and.
<<
val logor : int32 -> int32 -> int32
>>
Bitwise logical or.
<<
val logxor : int32 -> int32 -> int32
>>
Bitwise logical exclusive or.
<<
val lognot : int32 -> int32
>>
Bitwise logical negation
<<
val shift_left : int32 -> int -> int32
>>
Int32.shift_left x y shifts x to the left by y bits. The result is
unspecified if y < 0 or y >= 32.
<<
val shift_right : int32 -> int -> int32
>>
Int32.shift_right x y shifts x to the right by y bits. This is an
arithmetic shift: the sign bit of x is replicated and inserted in the
vacated bits. The result is unspecified if y < 0 or y >= 32.
<<
val shift_right_logical : int32 -> int -> int32
>>
Int32.shift_right_logical x y shifts x to the right by y bits. This is a
logical shift: zeroes are inserted in the vacated bits regardless of the
sign of x. The result is unspecified if y < 0 or y >= 32.
<<
val of_int : int -> int32
>>
Convert the given integer (type int) to a 32-bit integer (type int32).
<<
val to_int : int32 -> int
>>
Convert the given 32-bit integer (type int32) to an integer (type int). On
32-bit platforms, the 32-bit integer is taken modulo 2^31, i.e. the
high-order bit is lost during the conversion. On 64-bit platforms, the
conversion is exact.
<<
val of_float : float -> int32
>>
Convert the given floating-point number to a 32-bit integer, discarding the
fractional part (truncate towards 0). The result of the conversion is
undefined if, after truncation, the number is outside the range
[Int32.min_int[20.13], Int32.max_int[20.13]].
<<
val to_float : int32 -> float
>>
Convert the given 32-bit integer to a floating-point number.
<<
val of_string : string -> int32
>>
Convert the given string to a 32-bit integer. The string is read in decimal
(by default) or in hexadecimal, octal or binary if the string begins with
0x, 0o or 0b respectively. Raise Failure "int_of_string" if the given string
is not a valid representation of an integer, or if the integer represented
exceeds the range of integers representable in type int32.
<<
val to_string : int32 -> string
>>
Return the string representation of its argument, in signed decimal.
<<
val bits_of_float : float -> int32
>>
Return the internal representation of the given float according to the IEEE
754 floating-point "single format" bit layout. Bit 31 of the result
represents the sign of the float; bits 30 to 23 represent the (biased)
exponent; bits 22 to 0 represent the mantissa.
<<
val float_of_bits : int32 -> float
>>
Return the floating-point number whose internal representation, according
to the IEEE 754 floating-point "single format" bit layout, is the given
int32.
<<
type t = int32
>>
An alias for the type of 32-bit integers.
<<
val compare : t -> t -> int
>>
The comparison function for 32-bit integers, with the same specification as
Pervasives.compare[19.2]. Along with the type t, this function compare
allows the module Int32 to be passed as argument to the functors
Set.Make[20.28] and Map.Make[20.18].
20.14 Module Int64 : 64-bit integers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module provides operations on the type int64 of signed 64-bit integers.
Unlike the built-in int type, the type int64 is guaranteed to be exactly 64-bit
wide on all platforms. All arithmetic operations over int64 are taken modulo
2^64
Performance notice: values of type int64 occupy more memory space than values
of type int, and arithmetic operations on int64 are generally slower than those
on int. Use int64 only when the application requires exact 64-bit arithmetic.
<<
val zero : int64
>>
The 64-bit integer 0.
<<
val one : int64
>>
The 64-bit integer 1.
<<
val minus_one : int64
>>
The 64-bit integer -1.
<<
val neg : int64 -> int64
>>
Unary negation.
<<
val add : int64 -> int64 -> int64
>>
Addition.
<<
val sub : int64 -> int64 -> int64
>>
Subtraction.
<<
val mul : int64 -> int64 -> int64
>>
Multiplication.
<<
val div : int64 -> int64 -> int64
>>
Integer division. Raise Division_by_zero if the second argument is zero.
This division rounds the real quotient of its arguments towards zero, as
specified for Pervasives.(/)[19.2].
<<
val rem : int64 -> int64 -> int64
>>
Integer remainder. If y is not zero, the result of Int64.rem x y satisfies
the following property: x = Int64.add (Int64.mul (Int64.div x y) y)
(Int64.rem x y). If y = 0, Int64.rem x y raises Division_by_zero.
<<
val succ : int64 -> int64
>>
Successor. Int64.succ x is Int64.add x Int64.one.
<<
val pred : int64 -> int64
>>
Predecessor. Int64.pred x is Int64.sub x Int64.one.
<<
val abs : int64 -> int64
>>
Return the absolute value of its argument.
<<
val max_int : int64
>>
The greatest representable 64-bit integer, 2^63 - 1.
<<
val min_int : int64
>>
The smallest representable 64-bit integer, -2^63.
<<
val logand : int64 -> int64 -> int64
>>
Bitwise logical and.
<<
val logor : int64 -> int64 -> int64
>>
Bitwise logical or.
<<
val logxor : int64 -> int64 -> int64
>>
Bitwise logical exclusive or.
<<
val lognot : int64 -> int64
>>
Bitwise logical negation
<<
val shift_left : int64 -> int -> int64
>>
Int64.shift_left x y shifts x to the left by y bits. The result is
unspecified if y < 0 or y >= 64.
<<
val shift_right : int64 -> int -> int64
>>
Int64.shift_right x y shifts x to the right by y bits. This is an
arithmetic shift: the sign bit of x is replicated and inserted in the
vacated bits. The result is unspecified if y < 0 or y >= 64.
<<
val shift_right_logical : int64 -> int -> int64
>>
Int64.shift_right_logical x y shifts x to the right by y bits. This is a
logical shift: zeroes are inserted in the vacated bits regardless of the
sign of x. The result is unspecified if y < 0 or y >= 64.
<<
val of_int : int -> int64
>>
Convert the given integer (type int) to a 64-bit integer (type int64).
<<
val to_int : int64 -> int
>>
Convert the given 64-bit integer (type int64) to an integer (type int). On
64-bit platforms, the 64-bit integer is taken modulo 2^63, i.e. the
high-order bit is lost during the conversion. On 32-bit platforms, the
64-bit integer is taken modulo 2^31, i.e. the top 33 bits are lost during
the conversion.
<<
val of_float : float -> int64
>>
Convert the given floating-point number to a 64-bit integer, discarding the
fractional part (truncate towards 0). The result of the conversion is
undefined if, after truncation, the number is outside the range
[Int64.min_int[20.14], Int64.max_int[20.14]].
<<
val to_float : int64 -> float
>>
Convert the given 64-bit integer to a floating-point number.
<<
val of_int32 : int32 -> int64
>>
Convert the given 32-bit integer (type int32) to a 64-bit integer (type
int64).
<<
val to_int32 : int64 -> int32
>>
Convert the given 64-bit integer (type int64) to a 32-bit integer (type
int32). The 64-bit integer is taken modulo 2^32, i.e. the top 32 bits are
lost during the conversion.
<<
val of_nativeint : nativeint -> int64
>>
Convert the given native integer (type nativeint) to a 64-bit integer (type
int64).
<<
val to_nativeint : int64 -> nativeint
>>
Convert the given 64-bit integer (type int64) to a native integer. On
32-bit platforms, the 64-bit integer is taken modulo 2^32. On 64-bit
platforms, the conversion is exact.
<<
val of_string : string -> int64
>>
Convert the given string to a 64-bit integer. The string is read in decimal
(by default) or in hexadecimal, octal or binary if the string begins with
0x, 0o or 0b respectively. Raise Failure "int_of_string" if the given string
is not a valid representation of an integer, or if the integer represented
exceeds the range of integers representable in type int64.
<<
val to_string : int64 -> string
>>
Return the string representation of its argument, in decimal.
<<
val bits_of_float : float -> int64
>>
Return the internal representation of the given float according to the IEEE
754 floating-point "double format" bit layout. Bit 63 of the result
represents the sign of the float; bits 62 to 52 represent the (biased)
exponent; bits 51 to 0 represent the mantissa.
<<
val float_of_bits : int64 -> float
>>
Return the floating-point number whose internal representation, according
to the IEEE 754 floating-point "double format" bit layout, is the given
int64.
<<
type t = int64
>>
An alias for the type of 64-bit integers.
<<
val compare : t -> t -> int
>>
The comparison function for 64-bit integers, with the same specification as
Pervasives.compare[19.2]. Along with the type t, this function compare
allows the module Int64 to be passed as argument to the functors
Set.Make[20.28] and Map.Make[20.18].
20.15 Module Lazy : Deferred computations.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
type 'a t = 'a lazy_t
>>
A value of type 'a Lazy.t is a deferred computation, called a suspension,
that has a result of type 'a. The special expression syntax lazy (expr)
makes a suspension of the computation of expr, without computing expr itself
yet. "Forcing" the suspension will then compute expr and return its result.
Note: lazy_t is the built-in type constructor used by the compiler for the
lazy keyword. You should not use it directly. Always use Lazy.t instead.
Note: if the program is compiled with the -rectypes option, ill-founded
recursive definitions of the form let rec x = lazy x or let rec x =
lazy(lazy(...(lazy x))) are accepted by the type-checker and lead, when
forced, to ill-formed values that trigger infinite loops in the garbage
collector and other parts of the run-time system. Without the -rectypes
option, such ill-founded recursive definitions are rejected by the
type-checker.
<<
exception Undefined
>>
<<
val force : 'a t -> 'a
>>
force x forces the suspension x and returns its result. If x has already
been forced, Lazy.force x returns the same value again without recomputing
it. If it raised an exception, the same exception is raised again. Raise
Undefined if the forcing of x tries to force x itself recursively.
<<
val force_val : 'a t -> 'a
>>
force_val x forces the suspension x and returns its result. If x has
already been forced, force_val x returns the same value again without
recomputing it. Raise Undefined if the forcing of x tries to force x itself
recursively. If the computation of x raises an exception, it is unspecified
whether force_val x raises the same exception or Undefined.
<<
val lazy_from_fun : (unit -> 'a) -> 'a t
>>
lazy_from_fun f is the same as lazy (f ()) but slightly more efficient.
<<
val lazy_from_val : 'a -> 'a t
>>
lazy_from_val v returns an already-forced suspension of v This is for
special purposes only and should not be confused with lazy (v).
<<
val lazy_is_val : 'a t -> bool
>>
lazy_is_val x returns true if x has already been forced and did not raise
an exception.
20.16 Module Lexing : The run-time library for lexers generated by ocamllex.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Positions
=========
<<
type position = {
pos_fname : string ;
pos_lnum : int ;
pos_bol : int ;
pos_cnum : int ;
}
>>
A value of type position describes a point in a source file. pos_fname is
the file name; pos_lnum is the line number; pos_bol is the offset of the
beginning of the line (number of characters between the beginning of the
file and the beginning of the line); pos_cnum is the offset of the position
(number of characters between the beginning of the file and the position).
See the documentation of type lexbuf for information about how the lexing
engine will manage positions.
<<
val dummy_pos : position
>>
A value of type position, guaranteed to be different from any valid
position.
Lexer buffers
=============
<<
type lexbuf = {
refill_buff : lexbuf -> unit ;
mutable lex_buffer : string ;
mutable lex_buffer_len : int ;
mutable lex_abs_pos : int ;
mutable lex_start_pos : int ;
mutable lex_curr_pos : int ;
mutable lex_last_pos : int ;
mutable lex_last_action : int ;
mutable lex_eof_reached : bool ;
mutable lex_mem : int array ;
mutable lex_start_p : position ;
mutable lex_curr_p : position ;
}
>>
The type of lexer buffers. A lexer buffer is the argument passed to the
scanning functions defined by the generated scanners. The lexer buffer holds
the current state of the scanner, plus a function to refill the buffer from
the input.
Note that the lexing engine will only change the pos_cnum field of
lex_curr_p by updating it with the number of characters read since the start
of the lexbuf. The other fields are copied without change by the lexing
engine. In order to keep them accurate, they must be initialised before the
first use of the lexbuf, and updated by the relevant lexer actions (i.e. at
each end of line).
<<
val from_channel : Pervasives.in_channel -> lexbuf
>>
Create a lexer buffer on the given input channel. Lexing.from_channel
inchan returns a lexer buffer which reads from the input channel inchan, at
the current reading position.
<<
val from_string : string -> lexbuf
>>
Create a lexer buffer which reads from the given string. Reading starts
from the first character in the string. An end-of-input condition is
generated when the end of the string is reached.
<<
val from_function : (string -> int -> int) -> lexbuf
>>
Create a lexer buffer with the given function as its reading method. When
the scanner needs more characters, it will call the given function, giving
it a character string s and a character count n. The function should put n
characters or less in s, starting at character number 0, and return the
number of characters provided. A return value of 0 means end of input.
Functions for lexer semantic actions
====================================
The following functions can be called from the semantic actions of lexer
definitions (the ML code enclosed in braces that computes the value returned by
lexing functions). They give access to the character string matched by the
regular expression associated with the semantic action. These functions must be
applied to the argument lexbuf, which, in the code generated by ocamllex, is
bound to the lexer buffer passed to the parsing function.
<<
val lexeme : lexbuf -> string
>>
Lexing.lexeme lexbuf returns the string matched by the regular expression.
<<
val lexeme_char : lexbuf -> int -> char
>>
Lexing.lexeme_char lexbuf i returns character number i in the matched
string.
<<
val lexeme_start : lexbuf -> int
>>
Lexing.lexeme_start lexbuf returns the offset in the input stream of the
first character of the matched string. The first character of the stream has
offset 0.
<<
val lexeme_end : lexbuf -> int
>>
Lexing.lexeme_end lexbuf returns the offset in the input stream of the
character following the last character of the matched string. The first
character of the stream has offset 0.
<<
val lexeme_start_p : lexbuf -> position
>>
Like lexeme_start, but return a complete position instead of an offset.
<<
val lexeme_end_p : lexbuf -> position
>>
Like lexeme_end, but return a complete position instead of an offset.
Miscellaneous functions
=======================
<<
val flush_input : lexbuf -> unit
>>
Discard the contents of the buffer and reset the current position to 0. The
next use of the lexbuf will trigger a refill.
20.17 Module List : List operations.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Some functions are flagged as not tail-recursive. A tail-recursive function
uses constant stack space, while a non-tail-recursive function uses stack space
proportional to the length of its list argument, which can be a problem with
very long lists. When the function takes several list arguments, an approximate
formula giving stack usage (in some unspecified constant unit) is shown in
parentheses.
The above considerations can usually be ignored if your lists are not longer
than about 10000 elements.
<<
val length : 'a list -> int
>>
Return the length (number of elements) of the given list.
<<
val hd : 'a list -> 'a
>>
Return the first element of the given list. Raise Failure "hd" if the list
is empty.
<<
val tl : 'a list -> 'a list
>>
Return the given list without its first element. Raise Failure "tl" if the
list is empty.
<<
val nth : 'a list -> int -> 'a
>>
Return the n-th element of the given list. The first element (head of the
list) is at position 0. Raise Failure "nth" if the list is too short. Raise
Invalid_argument "List.nth" if n is negative.
<<
val rev : 'a list -> 'a list
>>
List reversal.
<<
val append : 'a list -> 'a list -> 'a list
>>
Catenate two lists. Same function as the infix operator @. Not
tail-recursive (length of the first argument). The @ operator is not
tail-recursive either.
<<
val rev_append : 'a list -> 'a list -> 'a list
>>
List.rev_append l1 l2 reverses l1 and concatenates it to l2. This is
equivalent to List.rev[20.17] l1 @ l2, but rev_append is tail-recursive and
more efficient.
<<
val concat : 'a list list -> 'a list
>>
Concatenate a list of lists. The elements of the argument are all
concatenated together (in the same order) to give the result. Not
tail-recursive (length of the argument + length of the longest sub-list).
<<
val flatten : 'a list list -> 'a list
>>
Same as concat. Not tail-recursive (length of the argument + length of the
longest sub-list).
Iterators
=========
<<
val iter : ('a -> unit) -> 'a list -> unit
>>
List.iter f [a1; ...; an] applies function f in turn to a1; ...; an. It is
equivalent to begin f a1; f a2; ...; f an; () end.
<<
val map : ('a -> 'b) -> 'a list -> 'b list
>>
List.map f [a1; ...; an] applies function f to a1, ..., an, and builds the
list [f a1; ...; f an] with the results returned by f. Not tail-recursive.
<<
val rev_map : ('a -> 'b) -> 'a list -> 'b list
>>
List.rev_map f l gives the same result as List.rev[20.17] (List.map[20.17]
f l), but is tail-recursive and more efficient.
<<
val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a
>>
List.fold_left f a [b1; ...; bn] is f (... (f (f a b1) b2) ...) bn.
<<
val fold_right : ('a -> 'b -> 'b) -> 'a list -> 'b -> 'b
>>
List.fold_right f [a1; ...; an] b is f a1 (f a2 (... (f an b) ...)). Not
tail-recursive.
Iterators on two lists
======================
<<
val iter2 : ('a -> 'b -> unit) -> 'a list -> 'b list -> unit
>>
List.iter2 f [a1; ...; an] [b1; ...; bn] calls in turn f a1 b1; ...; f an
bn. Raise Invalid_argument if the two lists have different lengths.
<<
val map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
>>
List.map2 f [a1; ...; an] [b1; ...; bn] is [f a1 b1; ...; f an bn]. Raise
Invalid_argument if the two lists have different lengths. Not
tail-recursive.
<<
val rev_map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
>>
List.rev_map2 f l1 l2 gives the same result as List.rev[20.17]
(List.map2[20.17] f l1 l2), but is tail-recursive and more efficient.
<<
val fold_left2 : ('a -> 'b -> 'c -> 'a) -> 'a -> 'b list -> 'c list -> 'a
>>
List.fold_left2 f a [b1; ...; bn] [c1; ...; cn] is f (... (f (f a b1 c1) b2
c2) ...) bn cn. Raise Invalid_argument if the two lists have different
lengths.
<<
val fold_right2 : ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> 'c -> 'c
>>
List.fold_right2 f [a1; ...; an] [b1; ...; bn] c is f a1 b1 (f a2 b2 (...
(f an bn c) ...)). Raise Invalid_argument if the two lists have different
lengths. Not tail-recursive.
List scanning
=============
<<
val for_all : ('a -> bool) -> 'a list -> bool
>>
for_all p [a1; ...; an] checks if all elements of the list satisfy the
predicate p. That is, it returns (p a1) && (p a2) && ... && (p an).
<<
val exists : ('a -> bool) -> 'a list -> bool
>>
exists p [a1; ...; an] checks if at least one element of the list satisfies
the predicate p. That is, it returns (p a1) || (p a2) || ... || (p an).
<<
val for_all2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool
>>
Same as List.for_all[20.17], but for a two-argument predicate. Raise
Invalid_argument if the two lists have different lengths.
<<
val exists2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool
>>
Same as List.exists[20.17], but for a two-argument predicate. Raise
Invalid_argument if the two lists have different lengths.
<<
val mem : 'a -> 'a list -> bool
>>
mem a l is true if and only if a is equal to an element of l.
<<
val memq : 'a -> 'a list -> bool
>>
Same as List.mem[20.17], but uses physical equality instead of structural
equality to compare list elements.
List searching
==============
<<
val find : ('a -> bool) -> 'a list -> 'a
>>
find p l returns the first element of the list l that satisfies the
predicate p. Raise Not_found if there is no value that satisfies p in the
list l.
<<
val filter : ('a -> bool) -> 'a list -> 'a list
>>
filter p l returns all the elements of the list l that satisfy the
predicate p. The order of the elements in the input list is preserved.
<<
val find_all : ('a -> bool) -> 'a list -> 'a list
>>
find_all is another name for List.filter[20.17].
<<
val partition : ('a -> bool) -> 'a list -> 'a list * 'a list
>>
partition p l returns a pair of lists (l1, l2), where l1 is the list of all
the elements of l that satisfy the predicate p, and l2 is the list of all
the elements of l that do not satisfy p. The order of the elements in the
input list is preserved.
Association lists
=================
<<
val assoc : 'a -> ('a * 'b) list -> 'b
>>
assoc a l returns the value associated with key a in the list of pairs l.
That is, assoc a [ ...; (a,b); ...] = b if (a,b) is the leftmost binding of
a in list l. Raise Not_found if there is no value associated with a in the
list l.
<<
val assq : 'a -> ('a * 'b) list -> 'b
>>
Same as List.assoc[20.17], but uses physical equality instead of structural
equality to compare keys.
<<
val mem_assoc : 'a -> ('a * 'b) list -> bool
>>
Same as List.assoc[20.17], but simply return true if a binding exists, and
false if no bindings exist for the given key.
<<
val mem_assq : 'a -> ('a * 'b) list -> bool
>>
Same as List.mem_assoc[20.17], but uses physical equality instead of
structural equality to compare keys.
<<
val remove_assoc : 'a -> ('a * 'b) list -> ('a * 'b) list
>>
remove_assoc a l returns the list of pairs l without the first pair with
key a, if any. Not tail-recursive.
<<
val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list
>>
Same as List.remove_assoc[20.17], but uses physical equality instead of
structural equality to compare keys. Not tail-recursive.
Lists of pairs
==============
<<
val split : ('a * 'b) list -> 'a list * 'b list
>>
Transform a list of pairs into a pair of lists: split [(a1,b1); ...;
(an,bn)] is ([a1; ...; an], [b1; ...; bn]). Not tail-recursive.
<<
val combine : 'a list -> 'b list -> ('a * 'b) list
>>
Transform a pair of lists into a list of pairs: combine [a1; ...; an] [b1;
...; bn] is [(a1,b1); ...; (an,bn)]. Raise Invalid_argument if the two lists
have different lengths. Not tail-recursive.
Sorting
=======
<<
val sort : ('a -> 'a -> int) -> 'a list -> 'a list
>>
Sort a list in increasing order according to a comparison function. The
comparison function must return 0 if its arguments compare as equal, a
positive integer if the first is greater, and a negative integer if the
first is smaller (see Array.sort for a complete specification). For example,
Pervasives.compare[19.2] is a suitable comparison function. The resulting
list is sorted in increasing order. List.sort is guaranteed to run in
constant heap space (in addition to the size of the result list) and
logarithmic stack space.
The current implementation uses Merge Sort. It runs in constant heap space
and logarithmic stack space.
<<
val stable_sort : ('a -> 'a -> int) -> 'a list -> 'a list
>>
Same as List.sort[20.17], but the sorting algorithm is guaranteed to be
stable (i.e. elements that compare equal are kept in their original order) .
The current implementation uses Merge Sort. It runs in constant heap space
and logarithmic stack space.
<<
val fast_sort : ('a -> 'a -> int) -> 'a list -> 'a list
>>
Same as List.sort[20.17] or List.stable_sort[20.17], whichever is faster on
typical input.
<<
val merge : ('a -> 'a -> int) -> 'a list -> 'a list -> 'a list
>>
Merge two lists: Assuming that l1 and l2 are sorted according to the
comparison function cmp, merge cmp l1 l2 will return a sorted list
containting all the elements of l1 and l2. If several elements compare
equal, the elements of l1 will be before the elements of l2. Not
tail-recursive (sum of the lengths of the arguments).
20.18 Module Map : Association tables over ordered types.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements applicative association tables, also known as finite
maps or dictionaries, given a total ordering function over the keys. All
operations over maps are purely applicative (no side-effects). The
implementation uses balanced binary trees, and therefore searching and
insertion take time logarithmic in the size of the map.
<<
module type OrderedType = >>
sig
<<
type t
>>
The type of the map keys.
<<
val compare : t -> t -> int
>>
A total ordering function over the keys. This is a two-argument function
f such that f e1 e2 is zero if the keys e1 and e2 are equal, f e1 e2 is
strictly negative if e1 is smaller than e2, and f e1 e2 is strictly
positive if e1 is greater than e2. Example: a suitable ordering function
is the generic structural comparison function Pervasives.compare[19.2].
end
Input signature of the functor Map.Make[20.18].
<<
module type S = >>
sig
<<
type key
>>
The type of the map keys.
<<
type +'a t
>>
The type of maps from type key to type 'a.
<<
val empty : 'a t
>>
The empty map.
<<
val is_empty : 'a t -> bool
>>
Test whether a map is empty or not.
<<
val add : key -> 'a -> 'a t -> 'a t
>>
add x y m returns a map containing the same bindings as m, plus a
binding of x to y. If x was already bound in m, its previous binding
disappears.
<<
val find : key -> 'a t -> 'a
>>
find x m returns the current binding of x in m, or raises Not_found if
no such binding exists.
<<
val remove : key -> 'a t -> 'a t
>>
remove x m returns a map containing the same bindings as m, except for x
which is unbound in the returned map.
<<
val mem : key -> 'a t -> bool
>>
mem x m returns true if m contains a binding for x, and false otherwise.
<<
val iter : (key -> 'a -> unit) -> 'a t -> unit
>>
iter f m applies f to all bindings in map m. f receives the key as first
argument, and the associated value as second argument. The bindings are
passed to f in increasing order with respect to the ordering over the
type of the keys. Only current bindings are presented to f: bindings
hidden by more recent bindings are not passed to f.
<<
val map : ('a -> 'b) -> 'a t -> 'b t
>>
map f m returns a map with same domain as m, where the associated value
a of all bindings of m has been replaced by the result of the application
of f to a. The bindings are passed to f in increasing order with respect
to the ordering over the type of the keys.
<<
val mapi : (key -> 'a -> 'b) -> 'a t -> 'b t
>>
Same as Map.S.map[20.18], but the function receives as arguments both
the key and the associated value for each binding of the map.
<<
val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
>>
fold f m a computes (f kN dN ... (f k1 d1 a)...), where k1 ... kN are
the keys of all bindings in m (in increasing order), and d1 ... dN are
the associated data.
<<
val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
>>
Total ordering between maps. The first argument is a total ordering used
to compare data associated with equal keys in the two maps.
<<
val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
>>
equal cmp m1 m2 tests whether the maps m1 and m2 are equal, that is,
contain equal keys and associate them with equal data. cmp is the
equality predicate used to compare the data associated with the keys.
end
Output signature of the functor Map.Make[20.18].
<<
module Make : >>
functor (Ord : OrderedType) -> S with type key = Ord.t
Functor building an implementation of the map structure given a totally
ordered type.
20.19 Module Marshal : Marshaling of data structures.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module provides functions to encode arbitrary data structures as
sequences of bytes, which can then be written on a file or sent over a pipe or
network connection. The bytes can then be read back later, possibly in another
process, and decoded back into a data structure. The format for the byte
sequences is compatible across all machines for a given version of Objective
Caml.
Warning: marshaling is currently not type-safe. The type of marshaled data is
not transmitted along the value of the data, making it impossible to check that
the data read back possesses the type expected by the context. In particular,
the result type of the Marshal.from_* functions is given as 'a, but this is
misleading: the returned Caml value does not possess type 'a for all 'a; it has
one, unique type which cannot be determined at compile-type. The programmer
should explicitly give the expected type of the returned value, using the
following syntax:
- (Marshal.from_channel chan : type). Anything can happen at run-time if the
object in the file does not belong to the given type.
The representation of marshaled values is not human-readable, and uses bytes
that are not printable characters. Therefore, input and output channels used in
conjunction with Marshal.to_channel and Marshal.from_channel must be opened in
binary mode, using e.g. open_out_bin or open_in_bin; channels opened in text
mode will cause unmarshaling errors on platforms where text channels behave
differently than binary channels, e.g. Windows.
<<
type extern_flags =
| No_sharing
>>
Don't preserve sharing
<<
| Closures
>>
Send function closures
The flags to the Marshal.to_* functions below.
<<
val to_channel : Pervasives.out_channel -> 'a -> extern_flags list -> unit
>>
Marshal.to_channel chan v flags writes the representation of v on channel
chan. The flags argument is a possibly empty list of flags that governs the
marshaling behavior with respect to sharing and functional values.
If flags does not contain Marshal.No_sharing, circularities and sharing
inside the value v are detected and preserved in the sequence of bytes
produced. In particular, this guarantees that marshaling always terminates.
Sharing between values marshaled by successive calls to Marshal.to_channel
is not detected, though. If flags contains Marshal.No_sharing, sharing is
ignored. This results in faster marshaling if v contains no shared
substructures, but may cause slower marshaling and larger byte
representations if v actually contains sharing, or even non-termination if v
contains cycles.
If flags does not contain Marshal.Closures, marshaling fails when it
encounters a functional value inside v: only "pure" data structures,
containing neither functions nor objects, can safely be transmitted between
different programs. If flags contains Marshal.Closures, functional values
will be marshaled as a position in the code of the program. In this case,
the output of marshaling can only be read back in processes that run exactly
the same program, with exactly the same compiled code. (This is checked at
un-marshaling time, using an MD5 digest of the code transmitted along with
the code position.)
<<
val to_string : 'a -> extern_flags list -> string
>>
Marshal.to_string v flags returns a string containing the representation of
v as a sequence of bytes. The flags argument has the same meaning as for
Marshal.to_channel[20.19].
<<
val to_buffer : string -> int -> int -> 'a -> extern_flags list -> int
>>
Marshal.to_buffer buff ofs len v flags marshals the value v, storing its
byte representation in the string buff, starting at character number ofs,
and writing at most len characters. It returns the number of characters
actually written to the string. If the byte representation of v does not fit
in len characters, the exception Failure is raised.
<<
val from_channel : Pervasives.in_channel -> 'a
>>
Marshal.from_channel chan reads from channel chan the byte representation
of a structured value, as produced by one of the Marshal.to_* functions, and
reconstructs and returns the corresponding value.
<<
val from_string : string -> int -> 'a
>>
Marshal.from_string buff ofs unmarshals a structured value like
Marshal.from_channel[20.19] does, except that the byte representation is not
read from a channel, but taken from the string buff, starting at position
ofs.
<<
val header_size : int
>>
The bytes representing a marshaled value are composed of a fixed-size
header and a variable-sized data part, whose size can be determined from the
header. Marshal.header_size[20.19] is the size, in characters, of the
header. Marshal.data_size[20.19] buff ofs is the size, in characters, of the
data part, assuming a valid header is stored in buff starting at position
ofs. Finally, Marshal.total_size[20.19] buff ofs is the total size, in
characters, of the marshaled value. Both Marshal.data_size[20.19] and
Marshal.total_size[20.19] raise Failure if buff, ofs does not contain a
valid header.
To read the byte representation of a marshaled value into a string buffer,
the program needs to read first Marshal.header_size[20.19] characters into
the buffer, then determine the length of the remainder of the representation
using Marshal.data_size[20.19], make sure the buffer is large enough to hold
the remaining data, then read it, and finally call
Marshal.from_string[20.19] to unmarshal the value.
<<
val data_size : string -> int -> int
>>
See Marshal.header_size[20.19].
<<
val total_size : string -> int -> int
>>
See Marshal.header_size[20.19].
20.20 Module Nativeint : Processor-native integers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module provides operations on the type nativeint of signed 32-bit
integers (on 32-bit platforms) or signed 64-bit integers (on 64-bit platforms).
This integer type has exactly the same width as that of a long integer type in
the C compiler. All arithmetic operations over nativeint are taken modulo 2^32
or 2^64 depending on the word size of the architecture.
Performance notice: values of type nativeint occupy more memory space than
values of type int, and arithmetic operations on nativeint are generally slower
than those on int. Use nativeint only when the application requires the extra
bit of precision over the int type.
<<
val zero : nativeint
>>
The native integer 0.
<<
val one : nativeint
>>
The native integer 1.
<<
val minus_one : nativeint
>>
The native integer -1.
<<
val neg : nativeint -> nativeint
>>
Unary negation.
<<
val add : nativeint -> nativeint -> nativeint
>>
Addition.
<<
val sub : nativeint -> nativeint -> nativeint
>>
Subtraction.
<<
val mul : nativeint -> nativeint -> nativeint
>>
Multiplication.
<<
val div : nativeint -> nativeint -> nativeint
>>
Integer division. Raise Division_by_zero if the second argument is zero.
This division rounds the real quotient of its arguments towards zero, as
specified for Pervasives.(/)[19.2].
<<
val rem : nativeint -> nativeint -> nativeint
>>
Integer remainder. If y is not zero, the result of Nativeint.rem x y
satisfies the following properties: Nativeint.zero <= Nativeint.rem x y <
Nativeint.abs y and x = Nativeint.add (Nativeint.mul (Nativeint.div x y) y)
(Nativeint.rem x y). If y = 0, Nativeint.rem x y raises Division_by_zero.
<<
val succ : nativeint -> nativeint
>>
Successor. Nativeint.succ x is Nativeint.add x Nativeint.one.
<<
val pred : nativeint -> nativeint
>>
Predecessor. Nativeint.pred x is Nativeint.sub x Nativeint.one.
<<
val abs : nativeint -> nativeint
>>
Return the absolute value of its argument.
<<
val size : int
>>
The size in bits of a native integer. This is equal to 32 on a 32-bit
platform and to 64 on a 64-bit platform.
<<
val max_int : nativeint
>>
The greatest representable native integer, either 2^31 - 1 on a 32-bit
platform, or 2^63 - 1 on a 64-bit platform.
<<
val min_int : nativeint
>>
The greatest representable native integer, either -2^31 on a 32-bit
platform, or -2^63 on a 64-bit platform.
<<
val logand : nativeint -> nativeint -> nativeint
>>
Bitwise logical and.
<<
val logor : nativeint -> nativeint -> nativeint
>>
Bitwise logical or.
<<
val logxor : nativeint -> nativeint -> nativeint
>>
Bitwise logical exclusive or.
<<
val lognot : nativeint -> nativeint
>>
Bitwise logical negation
<<
val shift_left : nativeint -> int -> nativeint
>>
Nativeint.shift_left x y shifts x to the left by y bits. The result is
unspecified if y < 0 or y >= bitsize, where bitsize is 32 on a 32-bit
platform and 64 on a 64-bit platform.
<<
val shift_right : nativeint -> int -> nativeint
>>
Nativeint.shift_right x y shifts x to the right by y bits. This is an
arithmetic shift: the sign bit of x is replicated and inserted in the
vacated bits. The result is unspecified if y < 0 or y >= bitsize.
<<
val shift_right_logical : nativeint -> int -> nativeint
>>
Nativeint.shift_right_logical x y shifts x to the right by y bits. This is
a logical shift: zeroes are inserted in the vacated bits regardless of the
sign of x. The result is unspecified if y < 0 or y >= bitsize.
<<
val of_int : int -> nativeint
>>
Convert the given integer (type int) to a native integer (type nativeint).
<<
val to_int : nativeint -> int
>>
Convert the given native integer (type nativeint) to an integer (type int).
The high-order bit is lost during the conversion.
<<
val of_float : float -> nativeint
>>
Convert the given floating-point number to a native integer, discarding the
fractional part (truncate towards 0). The result of the conversion is
undefined if, after truncation, the number is outside the range
[Nativeint.min_int[20.20], Nativeint.max_int[20.20]].
<<
val to_float : nativeint -> float
>>
Convert the given native integer to a floating-point number.
<<
val of_int32 : int32 -> nativeint
>>
Convert the given 32-bit integer (type int32) to a native integer.
<<
val to_int32 : nativeint -> int32
>>
Convert the given native integer to a 32-bit integer (type int32). On
64-bit platforms, the 64-bit native integer is taken modulo 2^32, i.e. the
top 32 bits are lost. On 32-bit platforms, the conversion is exact.
<<
val of_string : string -> nativeint
>>
Convert the given string to a native integer. The string is read in decimal
(by default) or in hexadecimal, octal or binary if the string begins with
0x, 0o or 0b respectively. Raise Failure "int_of_string" if the given string
is not a valid representation of an integer, or if the integer represented
exceeds the range of integers representable in type nativeint.
<<
val to_string : nativeint -> string
>>
Return the string representation of its argument, in decimal.
<<
type t = nativeint
>>
An alias for the type of native integers.
<<
val compare : t -> t -> int
>>
The comparison function for native integers, with the same specification as
Pervasives.compare[19.2]. Along with the type t, this function compare
allows the module Nativeint to be passed as argument to the functors
Set.Make[20.28] and Map.Make[20.18].
20.21 Module Oo : Operations on objects
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val copy : (< .. > as 'a) -> 'a
>>
Oo.copy o returns a copy of object o, that is a fresh object with the same
methods and instance variables as o
<<
val id : < .. > -> int
>>
Return an integer identifying this object, unique for the current execution
of the program.
20.22 Module Parsing : The run-time library for parsers generated by
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
ocamlyacc.
*=*=*=*=*=
<<
val symbol_start : unit -> int
>>
symbol_start and Parsing.symbol_end[20.22] are to be called in the action
part of a grammar rule only. They return the offset of the string that
matches the left-hand side of the rule: symbol_start() returns the offset of
the first character; symbol_end() returns the offset after the last
character. The first character in a file is at offset 0.
<<
val symbol_end : unit -> int
>>
See Parsing.symbol_start[20.22].
<<
val rhs_start : int -> int
>>
Same as Parsing.symbol_start[20.22] and Parsing.symbol_end[20.22], but
return the offset of the string matching the nth item on the right-hand side
of the rule, where n is the integer parameter to rhs_start and rhs_end. n is
1 for the leftmost item.
<<
val rhs_end : int -> int
>>
See Parsing.rhs_start[20.22].
<<
val symbol_start_pos : unit -> Lexing.position
>>
Same as symbol_start, but return a position instead of an offset.
<<
val symbol_end_pos : unit -> Lexing.position
>>
Same as symbol_end, but return a position instead of an offset.
<<
val rhs_start_pos : int -> Lexing.position
>>
Same as rhs_start, but return a position instead of an offset.
<<
val rhs_end_pos : int -> Lexing.position
>>
Same as rhs_end, but return a position instead of an offset.
<<
val clear_parser : unit -> unit
>>
Empty the parser stack. Call it just after a parsing function has returned,
to remove all pointers from the parser stack to structures that were built
by semantic actions during parsing. This is optional, but lowers the memory
requirements of the programs.
<<
exception Parse_error
>>
Raised when a parser encounters a syntax error. Can also be raised from the
action part of a grammar rule, to initiate error recovery.
20.23 Module Printexc : Facilities for printing exceptions.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val to_string : exn -> string
>>
Printexc.to_string e returns a string representation of the exception e.
<<
val print : ('a -> 'b) -> 'a -> 'b
>>
Printexc.print fn x applies fn to x and returns the result. If the
evaluation of fn x raises any exception, the name of the exception is
printed on standard error output, and the exception is raised again. The
typical use is to catch and report exceptions that escape a function
application.
<<
val catch : ('a -> 'b) -> 'a -> 'b
>>
Printexc.catch fn x is similar to Printexc.print[20.23], but aborts the
program with exit code 2 after printing the uncaught exception. This
function is deprecated: the runtime system is now able to print uncaught
exceptions as precisely as Printexc.catch does. Moreover, calling
Printexc.catch makes it harder to track the location of the exception using
the debugger or the stack backtrace facility. So, do not use Printexc.catch
in new code.
20.24 Module Printf : Formatted output functions.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
val fprintf :
Pervasives.out_channel ->
('a, Pervasives.out_channel, unit) Pervasives.format -> 'a
>>
fprintf outchan format arg1 ... argN formats the arguments arg1 to argN
according to the format string format, and outputs the resulting string on
the channel outchan.
The format is a character string which contains two types of objects: plain
characters, which are simply copied to the output channel, and conversion
specifications, each of which causes conversion and printing of arguments.
Conversion specifications have the following form:
% [positional specifier] [flags] [width] [.precision] type
In short, a conversion specification consists in the % character, followed
by optional modifiers and a type which is made of one or two characters. The
types and their meanings are:
- d, i, n, l, L, or N: convert an integer argument to signed decimal.
- u: convert an integer argument to unsigned decimal.
- x: convert an integer argument to unsigned hexadecimal, using lowercase
letters.
- X: convert an integer argument to unsigned hexadecimal, using uppercase
letters.
- o: convert an integer argument to unsigned octal.
- s: insert a string argument.
- S: insert a string argument in Caml syntax (double quotes, escapes).
- c: insert a character argument.
- C: insert a character argument in Caml syntax (single quotes, escapes).
- f: convert a floating-point argument to decimal notation, in the style
dddd.ddd.
- F: convert a floating-point argument to Caml syntax (dddd. or dddd.ddd or
d.ddd e+-dd).
- e or E: convert a floating-point argument to decimal notation, in the
style d.ddd e+-dd (mantissa and exponent).
- g or G: convert a floating-point argument to decimal notation, in style f
or e, E (whichever is more compact).
- B: convert a boolean argument to the string true or false
- b: convert a boolean argument (for backward compatibility; do not use in
new programs).
- ld, li, lu, lx, lX, lo: convert an int32 argument to the format specified
by the second letter (decimal, hexadecimal, etc).
- nd, ni, nu, nx, nX, no: convert a nativeint argument to the format
specified by the second letter.
- Ld, Li, Lu, Lx, LX, Lo: convert an int64 argument to the format specified
by the second letter.
- a: user-defined printer. Takes two arguments and applies the first one to
outchan (the current output channel) and to the second argument. The
first argument must therefore have type out_channel -> 'b -> unit and the
second 'b. The output produced by the function is inserted in the output
of fprintf at the current point.
- t: same as %a, but takes only one argument (with type out_channel ->
unit) and apply it to outchan.
- { fmt %}: convert a format string argument. The argument must have the
same type as the internal format string fmt.
- ( fmt %): format string substitution. Takes a format string argument and
substitutes it to the internal format string fmt to print following
arguments. The argument must have the same type as fmt.
- !: take no argument and flush the output.
- %: take no argument and output one % character.
The optional positional specifier consists of an integer followed by a $;
the integer indicates which argument to use, the first argument being
denoted by 1.
The optional flags are:
- -: left-justify the output (default is right justification).
- 0: for numerical conversions, pad with zeroes instead of spaces.
- +: for numerical conversions, prefix number with a + sign if positive.
- space: for numerical conversions, prefix number with a space if positive.
- `#': request an alternate formatting style for numbers.
The optional width is an integer indicating the minimal width of the result.
For instance, %6d prints an integer, prefixing it with spaces to fill at
least 6 characters.
The optional precision is a dot . followed by an integer indicating how many
digits follow the decimal point in the %f, %e, and %E conversions. For
instance, %.4f prints a float with 4 fractional digits.
The integer in a width or precision can also be specified as *, in which
case an extra integer argument is taken to specify the corresponding width
or precision. This integer argument precedes immediately the argument to
print, unless an optional positional specifier is given to indicates which
argument to use. For instance, %.*3$f prints a float with as many fractional
digits as the value of the third argument.
<<
val printf : ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a
>>
Same as Printf.fprintf[20.24], but output on stdout.
<<
val eprintf : ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a
>>
Same as Printf.fprintf[20.24], but output on stderr.
<<
val ifprintf : 'a -> ('b, 'a, unit) Pervasives.format -> 'b
>>
Same as Printf.fprintf[20.24], but does not print anything. Useful to
ignore some material when conditionally printing.
<<
val sprintf : ('a, unit, string) Pervasives.format -> 'a
>>
Same as Printf.fprintf[20.24], but instead of printing on an output
channel, return a string containing the result of formatting the arguments.
<<
val bprintf : Buffer.t -> ('a, Buffer.t, unit) Pervasives.format -> 'a
>>
Same as Printf.fprintf[20.24], but instead of printing on an output
channel, append the formatted arguments to the given extensible buffer (see
module Buffer[20.3]).
<<
val kfprintf :
(Pervasives.out_channel -> 'a) ->
Pervasives.out_channel ->
('b, Pervasives.out_channel, unit, 'a) Pervasives.format4 -> 'b
>>
Formatted output functions with continuations.
Same as fprintf, but instead of returning immediately, passes the out
channel to its first argument at the end of printing.
<<
val ksprintf :
(string -> 'a) -> ('b, unit, string, 'a) Pervasives.format4 -> 'b
>>
Same as sprintf above, but instead of returning the string, passes it to
the first argument.
<<
val kbprintf :
(Buffer.t -> 'a) ->
Buffer.t -> ('b, Buffer.t, unit, 'a) Pervasives.format4 -> 'b
>>
Same as bprintf, but instead of returning immediately, passes the buffer to
its first argument at the end of printing.
<<
val kprintf :
(string -> 'a) -> ('b, unit, string, 'a) Pervasives.format4 -> 'b
>>
A deprecated synonym for ksprintf.
20.25 Module Queue : First-in first-out queues.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements queues (FIFOs), with in-place modification.
<<
type 'a t
>>
The type of queues containing elements of type 'a.
<<
exception Empty
>>
Raised when Queue.take[20.25] or Queue.peek[20.25] is applied to an empty
queue.
<<
val create : unit -> 'a t
>>
Return a new queue, initially empty.
<<
val add : 'a -> 'a t -> unit
>>
add x q adds the element x at the end of the queue q.
<<
val push : 'a -> 'a t -> unit
>>
push is a synonym for add.
<<
val take : 'a t -> 'a
>>
take q removes and returns the first element in queue q, or raises Empty if
the queue is empty.
<<
val pop : 'a t -> 'a
>>
pop is a synonym for take.
<<
val peek : 'a t -> 'a
>>
peek q returns the first element in queue q, without removing it from the
queue, or raises Empty if the queue is empty.
<<
val top : 'a t -> 'a
>>
top is a synonym for peek.
<<
val clear : 'a t -> unit
>>
Discard all elements from a queue.
<<
val copy : 'a t -> 'a t
>>
Return a copy of the given queue.
<<
val is_empty : 'a t -> bool
>>
Return true if the given queue is empty, false otherwise.
<<
val length : 'a t -> int
>>
Return the number of elements in a queue.
<<
val iter : ('a -> unit) -> 'a t -> unit
>>
iter f q applies f in turn to all elements of q, from the least recently
entered to the most recently entered. The queue itself is unchanged.
<<
val fold : ('a -> 'b -> 'a) -> 'a -> 'b t -> 'a
>>
fold f accu q is equivalent to List.fold_left f accu l, where l is the list
of q's elements. The queue remains unchanged.
<<
val transfer : 'a t -> 'a t -> unit
>>
transfer q1 q2 adds all of q1's elements at the end of the queue q2, then
clears q1. It is equivalent to the sequence iter (fun x -> add x q2) q1;
clear q1, but runs in constant time.
20.26 Module Random : Pseudo-random number generators (PRNG).
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Basic functions
===============
<<
val init : int -> unit
>>
Initialize the generator, using the argument as a seed. The same seed will
always yield the same sequence of numbers.
<<
val full_init : int array -> unit
>>
Same as Random.init[20.26] but takes more data as seed.
<<
val self_init : unit -> unit
>>
Initialize the generator with a more-or-less random seed chosen in a
system-dependent way.
<<
val bits : unit -> int
>>
Return 30 random bits in a nonnegative integer.
<<
val int : int -> int
>>
Random.int bound returns a random integer between 0 (inclusive) and bound
(exclusive). bound must be greater than 0 and less than 2^30.
<<
val int32 : Int32.t -> Int32.t
>>
Random.int32 bound returns a random integer between 0 (inclusive) and bound
(exclusive). bound must be greater than 0.
<<
val nativeint : Nativeint.t -> Nativeint.t
>>
Random.nativeint bound returns a random integer between 0 (inclusive) and
bound (exclusive). bound must be greater than 0.
<<
val int64 : Int64.t -> Int64.t
>>
Random.int64 bound returns a random integer between 0 (inclusive) and bound
(exclusive). bound must be greater than 0.
<<
val float : float -> float
>>
Random.float bound returns a random floating-point number between 0
(inclusive) and bound (exclusive). If bound is negative, the result is
negative or zero. If bound is 0, the result is 0.
<<
val bool : unit -> bool
>>
Random.bool () returns true or false with probability 0.5 each.
Advanced functions
==================
The functions from module State manipulate the current state of the random
generator explicitely. This allows using one or several deterministic PRNGs,
even in a multi-threaded program, without interference from other parts of the
program.
<<
module State : >>
sig
<<
type t
>>
The type of PRNG states.
<<
val make : int array -> t
>>
Create a new state and initialize it with the given seed.
<<
val make_self_init : unit -> t
>>
Create a new state and initialize it with a system-dependent low-entropy
seed.
<<
val copy : t -> t
>>
Return a copy of the given state.
<<
val bits : t -> int
>>
<<
val int : t -> int -> int
>>
<<
val int32 : t -> Int32.t -> Int32.t
>>
<<
val nativeint : t -> Nativeint.t -> Nativeint.t
>>
<<
val int64 : t -> Int64.t -> Int64.t
>>
<<
val float : t -> float -> float
>>
<<
val bool : t -> bool
>>
These functions are the same as the basic functions, except that they
use (and update) the given PRNG state instead of the default one.
end
<<
val get_state : unit -> State.t
>>
Return the current state of the generator used by the basic functions.
<<
val set_state : State.t -> unit
>>
Set the state of the generator used by the basic functions.
20.27 Module Scanf : Formatted input functions.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Functional input with format strings.
=====================================
The formatted input functions provided by module Scanf are functionals that
apply their function argument to the values they read in the input. The
specification of the values to read is simply given by a format string (the
same format strings as those used to print material using module Printf[20.24]
or module Format[20.9]).
As an example, consider the formatted input function scanf that reads from
standard input; a typical call to scanf is simply scanf fmt f, meaning that f
should be applied to the arguments read according to the format string fmt. For
instance, if f is defined as let f x = x + 1, then scanf "%d" f will read a
decimal integer i from stdin and return f i; thus, if we enter 41 at the
keyboard, scanf "%d" f evaluates to 42.
This module provides general formatted input functions that read from any
kind of input, including strings, files, or anything that can return
characters. Hence, a typical call to a formatted input function bscan is bscan
ib fmt f, meaning that f should be applied to the arguments read from input ib,
according to the format string fmt.
The Caml scanning facility is reminiscent of the corresponding C feature.
However, it is also largely different, simpler, and yet more powerful: the
formatted input functions are higher-order functionals and the parameter
passing mechanism is simply the regular function application not the variable
assigment based mechanism which is typical of formatted input in imperative
languages; the format strings also feature useful additions to easily define
complex tokens; as expected of a functional programming language feature, the
formatted input functions support polymorphism, in particular arbitrary
interaction with polymorphic user-defined scanners. Furthermore, the Caml
formatted input facility is fully type-checked at compile time.
<<
module Scanning : >>
sig
<<
type scanbuf
>>
The type of scanning buffers. A scanning buffer is the source from which
a formatted input function gets characters. The scanning buffer holds the
current state of the scan, plus a function to get the next char from the
input, and a token buffer to store the string matched so far.
Note: a scan may often require to examine one character in advance; when
this "lookahead" character does not belong to the token read, it is
stored back in the scanning buffer and becomes the next character read.
<<
val stdib : scanbuf
>>
The scanning buffer reading from stdin. stdib is equivalent to
Scanning.from_channel stdin.
Note: when input is read interactively from stdin, the newline character
that triggers the evaluation is incorporated in the input; thus, scanning
specifications must properly skip this character (simply add a '\n' as
the last character of the format string).
<<
val from_string : string -> scanbuf
>>
Scanning.from_string s returns a scanning buffer which reads from the
given string. Reading starts from the first character in the string. The
end-of-input condition is set when the end of the string is reached.
<<
val from_file : string -> scanbuf
>>
Bufferized file reading in text mode. The efficient and usual way to
scan text mode files (in effect, from_file returns a scanning buffer that
reads characters in large chunks, rather than one character at a time as
buffers returned by from_channel do). Scanning.from_file fname returns a
scanning buffer which reads from the given file fname in text mode.
<<
val from_file_bin : string -> scanbuf
>>
Bufferized file reading in binary mode.
<<
val from_function : (unit -> char) -> scanbuf
>>
Scanning.from_function f returns a scanning buffer with the given
function as its reading method.
When scanning needs one more character, the given function is called.
When the function has no more character to provide, it must signal an
end-of-input condition by raising the exception End_of_file.
<<
val from_channel : Pervasives.in_channel -> scanbuf
>>
Scanning.from_channel ic returns a scanning buffer which reads one
character at a time from the input channel ic, starting at the current
reading position.
<<
val end_of_input : scanbuf -> bool
>>
Scanning.end_of_input ib tests the end-of-input condition of the given
scanning buffer.
<<
val beginning_of_input : scanbuf -> bool
>>
Scanning.beginning_of_input ib tests the beginning of input condition of
the given scanning buffer.
<<
val name_of_input : scanbuf -> string
>>
Scanning.file_name_of_input ib returns the name of the character source
for the scanning buffer ib.
end
Scanning buffers
================
<<
exception Scan_failure of string
>>
The exception raised by formatted input functions when the input cannot be
read according to the given format.
<<
type ('a, 'b, 'c, 'd) scanner = ('a, Scanning.scanbuf, 'b, 'c, 'a -> 'd, 'd)
format6 -> 'c
>>
The type of formatted input scanners: ('a, 'b, 'c, 'd) scanner is the type
of a formatted input function that reads from some scanning buffer according
to some format string; more precisely, if scan is some formatted input
function, then scan ib fmt f applies f to the arguments specified by the
format string fmt, when scan has read those arguments from some scanning
buffer ib.
For instance, the scanf function below has type ('a, 'b, 'c, 'd) scanner,
since it is a formatted input function that reads from stdib: scanf fmt f
applies f to the arguments specified by fmt, reading those arguments from
stdin as expected.
If the format fmt has some %r indications, the corresponding input functions
must be provided before the f argument. For instance, if read_elem is an
input function for values of type t, then bscanf ib "%r;" read_elem f reads
a value of type t followed by a ';' character.
Formatted input functions
=========================
<<
val bscanf : Scanning.scanbuf -> ('a, 'b, 'c, 'd) scanner
>>
bscanf ib fmt r1 ... rN f reads arguments for the function f from the
scanning buffer ib according to the format string fmt, and applies f to
these values. The result of this call to f is returned as the result of
bscanf. For instance, if f is the function fun s i -> i + 1, then
Scanf.sscanf "x = 1" "%s = %i" f returns 2.
Arguments r1 to rN are user-defined input functions that read the argument
corresponding to a %r conversion.
The format is a character string which contains three types of objects:
- plain characters, which are simply matched with the characters of the
input,
- conversion specifications, each of which causes reading and conversion of
one argument for f,
- scanning indications to specify boundaries of tokens.
Among plain characters the space character (ASCII code 32) has a special
meaning: it matches "whitespace", that is any number of tab, space, line
feed and carriage return characters. Hence, a space in the format matches
any amount of whitespace in the input.
Conversion specifications consist in the % character, followed by an
optional flag, an optional field width, and followed by one or two
conversion characters. The conversion characters and their meanings are:
- d: reads an optionally signed decimal integer.
- i: reads an optionally signed integer (usual input formats for
hexadecimal (0x[d]+ and 0X[d]+), octal (0o[d]+), and binary 0b[d]+
notations are understood).
- u: reads an unsigned decimal integer.
- x or X: reads an unsigned hexadecimal integer.
- o: reads an unsigned octal integer.
- s: reads a string argument that spreads as much as possible, until the
next white space, the next scanning indication, or the end-of-input is
reached. Hence, this conversion always succeeds: it returns an empty
string if the bounding condition holds when the scan begins.
- S: reads a delimited string argument (delimiters and special escaped
characters follow the lexical conventions of Caml).
- c: reads a single character. To test the current input character without
reading it, specify a null field width, i.e. use specification %0c. Raise
Invalid_argument, if the field width specification is greater than 1.
- C: reads a single delimited character (delimiters and special escaped
characters follow the lexical conventions of Caml).
- f, e, E, g, G: reads an optionally signed floating-point number in
decimal notation, in the style dddd.ddd e/E+-dd.
- F: reads a floating point number according to the lexical conventions of
Caml (hence the decimal point is mandatory if the exponent part is not
mentioned).
- B: reads a boolean argument (true or false).
- b: reads a boolean argument (for backward compatibility; do not use in
new programs).
- ld, li, lu, lx, lX, lo: reads an int32 argument to the format specified
by the second letter (decimal, hexadecimal, etc).
- nd, ni, nu, nx, nX, no: reads a nativeint argument to the format
specified by the second letter.
- Ld, Li, Lu, Lx, LX, Lo: reads an int64 argument to the format specified
by the second letter.
- [ range ]: reads characters that matches one of the characters mentioned
in the range of characters range (or not mentioned in it, if the range
starts with ^). Reads a string that can be empty, if the next input
character does not match the range. The set of characters from c1 to c2
(inclusively) is denoted by c1-c2. Hence, %[0-9] returns a string
representing a decimal number or an empty string if no decimal digit is
found; similarly, %[\\048-\\057\\065-\\070] returns a string of
hexadecimal digits. If a closing bracket appears in a range, it must
occur as the first character of the range (or just after the ^ in case of
range negation); hence []] matches a ] character and [^]] matches any
character that is not ].
- r: user-defined reader. Takes the next ri formatted input function and
applies it to the scanning buffer ib to read the next argument. The input
function ri must therefore have type Scanning.scanbuf -> 'a and the
argument read has type 'a.
- { fmt %}: reads a format string argument to the format specified by the
internal format fmt. The format string to be read must have the same type
as the internal format fmt. For instance, "%{%i%}" reads any format
string that can read a value of type int; hence Scanf.sscanf
"fmt:\\\"number is %u\\\"" "fmt:%{%i%}" succeeds and returns the format
string "number is %u".
- \( fmt %\): scanning format substitution. Reads a format string to
replace fmt. The format string read must have the same type as fmt.
- l: returns the number of lines read so far.
- n: returns the number of characters read so far.
- N or L: returns the number of tokens read so far.
- !: matches the end of input condition.
- %: matches one % character in the input.
Following the % character that introduces a conversion, there may be the
special flag _: the conversion that follows occurs as usual, but the
resulting value is discarded. For instance, if f is the function fun i -> i
+ 1, then Scanf.sscanf "x = 1" "%_s = %i" f returns 2.
The field width is composed of an optional integer literal indicating the
maximal width of the token to read. For instance, %6d reads an integer,
having at most 6 decimal digits; %4f reads a float with at most 4
characters; and %8[\\000-\\255] returns the next 8 characters (or all the
characters still available, if fewer than 8 characters are available in the
input).
Scanning indications appear just after the string conversions %s and %[
range ] to delimit the end of the token. A scanning indication is introduced
by a @ character, followed by some constant character c. It means that the
string token should end just before the next matching c (which is skipped).
If no c character is encountered, the string token spreads as much as
possible. For instance, "%s@\t" reads a string up to the next tab character
or to the end of input. If a scanning indication @c does not follow a string
conversion, it is treated as a plain c character.
Raise Scanf.Scan_failure if the input does not match the format.
Raise Failure if a conversion to a number is not possible.
Raise End_of_file if the end of input is encountered while some more
characters are needed to read the current conversion specification. As a
consequence, scanning a %s conversion never raises exception End_of_file: if
the end of input is reached the conversion succeeds and simply returns the
characters read so far, or "" if none were read.
Raise Invalid_argument if the format string is invalid.
Notes:
- the scanning indications introduce slight differences in the syntax of
Scanf format strings compared to those used by the Printf module.
However, scanning indications are similar to those of the Format module;
hence, when producing formatted text to be scanned by !Scanf.bscanf, it
is wise to use printing functions from Format (or, if you need to use
functions from Printf, banish or carefully double check the format
strings that contain '@' characters).
- in addition to relevant digits, '_' characters may appear inside numbers
(this is reminiscent to the usual Caml lexical conventions). If stricter
scanning is desired, use the range conversion facility instead of the
number conversions.
- the scanf facility is not intended for heavy duty lexical analysis and
parsing. If it appears not expressive enough for your needs, several
alternative exists: regular expressions (module Str), stream parsers,
ocamllex-generated lexers, ocamlyacc-generated parsers.
<<
val fscanf : Pervasives.in_channel -> ('a, 'b, 'c, 'd) scanner
>>
Same as Scanf.bscanf[20.27], but reads from the given channel.
Warning: since all formatted input functions operate from a scanning buffer,
be aware that each fscanf invocation must allocate a new fresh scanning
buffer (unless you make careful use of partial application). Hence, there
are chances that some characters seem to be skipped (in fact they are
pending in the previously used scanning buffer). This happens in particular
when calling fscanf again after a scan involving a format that necessitated
some look ahead (such as a format that ends by skipping whitespace in the
input).
To avoid confusion, consider using bscanf with an explicitly created
scanning buffer. Use for instance Scanning.from_file f to allocate the
scanning buffer reading from file f.
This method is not only clearer it is also faster, since scanning buffers to
files are optimized for fast buffered reading.
<<
val sscanf : string -> ('a, 'b, 'c, 'd) scanner
>>
Same as Scanf.bscanf[20.27], but reads from the given string.
<<
val scanf : ('a, 'b, 'c, 'd) scanner
>>
Same as Scanf.bscanf[20.27], but reads from the predefined scanning buffer
Scanf.Scanning.stdib[20.27] that is connected to stdin.
<<
val kscanf :
Scanning.scanbuf ->
(Scanning.scanbuf -> exn -> 'a) -> ('b, 'c, 'd, 'a) scanner
>>
Same as Scanf.bscanf[20.27], but takes an additional function argument ef
that is called in case of error: if the scanning process or some conversion
fails, the scanning function aborts and calls the error handling function ef
with the scanning buffer and the exception that aborted the scanning
process.
<<
val bscanf_format :
Scanning.scanbuf ->
('a, 'b, 'c, 'd, 'e, 'f) format6 ->
(('a, 'b, 'c, 'd, 'e, 'f) format6 -> 'g) -> 'g
>>
bscanf_format ib fmt f reads a format string token from the scannning
buffer ib, according to the given format string fmt, and applies f to the
resulting format string value. Raise Scan_failure if the format string value
read doesn't have the same type as fmt.
<<
val sscanf_format :
string ->
('a, 'b, 'c, 'd, 'e, 'f) format6 ->
(('a, 'b, 'c, 'd, 'e, 'f) format6 -> 'g) -> 'g
>>
Same as Scanf.bscanf_format[20.27], but reads from the given string.
<<
val format_from_string :
string ->
('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c, 'd, 'e, 'f) format6
>>
format_from_string s fmt converts a string argument to a format string,
according to the given format string fmt. Raise Scan_failure if s,
considered as a format string, doesn't have the same type as fmt.
20.28 Module Set : Sets over ordered types.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
This module implements the set data structure, given a total ordering
function over the set elements. All operations over sets are purely applicative
(no side-effects). The implementation uses balanced binary trees, and is
therefore reasonably efficient: insertion and membership take time logarithmic
in the size of the set, for instance.
<<
module type OrderedType = >>
sig
<<
type t
>>
The type of the set elements.
<<
val compare : t -> t -> int
>>
A total ordering function over the set elements. This is a two-argument
function f such that f e1 e2 is zero if the elements e1 and e2 are equal,
f e1 e2 is strictly negative if e1 is smaller than e2, and f e1 e2 is
strictly positive if e1 is greater than e2. Example: a suitable ordering
function is the generic structural comparison function
Pervasives.compare[19.2].
end
Input signature of the functor Set.Make[20.28].
<<
module type S = >>
sig
<<
type elt
>>
The type of the set elements.
<<
type t
>>
The type of sets.
<<
val empty : t
>>
The empty set.
<<
val is_empty : t -> bool
>>
Test whether a set is empty or not.
<<
val mem : elt -> t -> bool
>>
mem x s tests whether x belongs to the set s.
<<
val add : elt -> t -> t
>>
add x s returns a set containing all elements of s, plus x. If x was
already in s, s is returned unchanged.
<<
val singleton : elt -> t
>>
singleton x returns the one-element set containing only x.
<<
val remove : elt -> t -> t
>>
remove x s returns a set containing all elements of s, except x. If x
was not in s, s is returned unchanged.
<<
val union : t -> t -> t
>>
Set union.
<<
val inter : t -> t -> t
>>
Set intersection.
<<
val diff : t -> t -> t
>>
Set difference.
<<
val compare : t -> t -> int
>>
Total ordering between sets. Can be used as the ordering function for
doing sets of sets.
<<
val equal : t -> t -> bool
>>
equal s1 s2 tests whether the sets s1 and s2 are equal, that is, contain
equal elements.
<<
val subset : t -> t -> bool
>>
subset s1 s2 tests whether the set s1 is a subset of the set s2.
<<
val iter : (elt -> unit) -> t -> unit
>>
iter f s applies f in turn to all elements of s. The elements of s are
presented to f in increasing order with respect to the ordering over the
type of the elements.
<<
val fold : (elt -> 'a -> 'a) -> t -> 'a -> 'a
>>
fold f s a computes (f xN ... (f x2 (f x1 a))...), where x1 ... xN are
the elements of s, in increasing order.
<<
val for_all : (elt -> bool) -> t -> bool
>>
for_all p s checks if all elements of the set satisfy the predicate p.
<<
val exists : (elt -> bool) -> t -> bool
>>
exists p s checks if at least one element of the set satisfies the
predicate p.
<<
val filter : (elt -> bool) -> t -> t
>>
filter p s returns the set of all elements in s that satisfy predicate
p.
<<
val partition : (elt -> bool) -> t -> t * t
>>
partition p s returns a pair of sets (s1, s2), where s1 is the set of
all the elements of s that satisfy the predicate p, and s2 is the set of
all the elements of s that do not satisfy p.
<<
val cardinal : t -> int
>>
Return the number of elements of a set.
<<
val elements : t -> elt list
>>
Return the list of all elements of the given set. The returned list is
sorted in increasing order with respect to the ordering Ord.compare,
where Ord is the argument given to Set.Make[20.28].
<<
val min_elt : t -> elt
>>
Return the smallest element of the given set (with respect to the
Ord.compare ordering), or raise Not_found if the set is empty.
<<
val max_elt : t -> elt
>>
Same as Set.S.min_elt[20.28], but returns the largest element of the
given set.
<<
val choose : t -> elt
>>
Return one element of the given set, or raise Not_found if the set is
empty. Which element is chosen is unspecified, but equal elements will be
chosen for equal sets.
<<
val split : elt -> t -> t * bool * t
>>
split x s returns a triple (l, present, r), where l is the set of
elements of s that are strictly less than x; r is the set of elements of
s that are strictly greater than x; present is false if s contains no
element equal to x, or true if s contains an element equal to x.
end
Output signature of the functor Set.Make[20.28].
<<
module Make : >>
functor (Ord : OrderedType) -> S with type elt = Ord.t
Functor building an implementation of the set structure given a totally
ordered type.
20.29 Module Sort : Sorting and merging lists.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module is obsolete and exists only for backward compatibility. The
sorting functions in Array[20.2] and List[20.17] should be used instead. The
new functions are faster and use less memory.Sorting and merging lists.
<<
val list : ('a -> 'a -> bool) -> 'a list -> 'a list
>>
Sort a list in increasing order according to an ordering predicate. The
predicate should return true if its first argument is less than or equal to
its second argument.
<<
val array : ('a -> 'a -> bool) -> 'a array -> unit
>>
Sort an array in increasing order according to an ordering predicate. The
predicate should return true if its first argument is less than or equal to
its second argument. The array is sorted in place.
<<
val merge : ('a -> 'a -> bool) -> 'a list -> 'a list -> 'a list
>>
Merge two lists according to the given predicate. Assuming the two argument
lists are sorted according to the predicate, merge returns a sorted list
containing the elements from the two lists. The behavior is undefined if the
two argument lists were not sorted.
20.30 Module Stack : Last-in first-out stacks.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements stacks (LIFOs), with in-place modification.
<<
type 'a t
>>
The type of stacks containing elements of type 'a.
<<
exception Empty
>>
Raised when Stack.pop[20.30] or Stack.top[20.30] is applied to an empty
stack.
<<
val create : unit -> 'a t
>>
Return a new stack, initially empty.
<<
val push : 'a -> 'a t -> unit
>>
push x s adds the element x at the top of stack s.
<<
val pop : 'a t -> 'a
>>
pop s removes and returns the topmost element in stack s, or raises Empty
if the stack is empty.
<<
val top : 'a t -> 'a
>>
top s returns the topmost element in stack s, or raises Empty if the stack
is empty.
<<
val clear : 'a t -> unit
>>
Discard all elements from a stack.
<<
val copy : 'a t -> 'a t
>>
Return a copy of the given stack.
<<
val is_empty : 'a t -> bool
>>
Return true if the given stack is empty, false otherwise.
<<
val length : 'a t -> int
>>
Return the number of elements in a stack.
<<
val iter : ('a -> unit) -> 'a t -> unit
>>
iter f s applies f in turn to all elements of s, from the element at the
top of the stack to the element at the bottom of the stack. The stack itself
is unchanged.
20.31 Module StdLabels : Standard labeled libraries.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This meta-module provides labelized version of the Array[20.2], List[20.17]
and String[20.33] modules.
They only differ by their labels. Detailed interfaces can be found in
arrayLabels.mli, listLabels.mli and stringLabels.mli.
<<
module Array : >>
sig
<<
val length : 'a array -> int
>>
<<
val get : 'a array -> int -> 'a
>>
<<
val set : 'a array -> int -> 'a -> unit
>>
<<
val make : int -> 'a -> 'a array
>>
<<
val create : int -> 'a -> 'a array
>>
<<
val init : int -> f:(int -> 'a) -> 'a array
>>
<<
val make_matrix : dimx:int -> dimy:int -> 'a -> 'a array array
>>
<<
val create_matrix : dimx:int -> dimy:int -> 'a -> 'a array array
>>
<<
val append : 'a array -> 'a array -> 'a array
>>
<<
val concat : 'a array list -> 'a array
>>
<<
val sub : 'a array -> pos:int -> len:int -> 'a array
>>
<<
val copy : 'a array -> 'a array
>>
<<
val fill : 'a array -> pos:int -> len:int -> 'a -> unit
>>
<<
val blit :
src:'a array -> src_pos:int -> dst:'a array -> dst_pos:int -> len:int ->
unit
>>
<<
val to_list : 'a array -> 'a list
>>
<<
val of_list : 'a list -> 'a array
>>
<<
val iter : f:('a -> unit) -> 'a array -> unit
>>
<<
val map : f:('a -> 'b) -> 'a array -> 'b array
>>
<<
val iteri : f:(int -> 'a -> unit) -> 'a array -> unit
>>
<<
val mapi : f:(int -> 'a -> 'b) -> 'a array -> 'b array
>>
<<
val fold_left : f:('a -> 'b -> 'a) -> init:'a -> 'b array -> 'a
>>
<<
val fold_right : f:('a -> 'b -> 'b) -> 'a array -> init:'b -> 'b
>>
<<
val sort : cmp:('a -> 'a -> int) -> 'a array -> unit
>>
<<
val stable_sort : cmp:('a -> 'a -> int) -> 'a array -> unit
>>
<<
val fast_sort : cmp:('a -> 'a -> int) -> 'a array -> unit
>>
<<
val unsafe_get : 'a array -> int -> 'a
>>
<<
val unsafe_set : 'a array -> int -> 'a -> unit
>>
end
<<
module List : >>
sig
<<
val length : 'a list -> int
>>
<<
val hd : 'a list -> 'a
>>
<<
val tl : 'a list -> 'a list
>>
<<
val nth : 'a list -> int -> 'a
>>
<<
val rev : 'a list -> 'a list
>>
<<
val append : 'a list -> 'a list -> 'a list
>>
<<
val rev_append : 'a list -> 'a list -> 'a list
>>
<<
val concat : 'a list list -> 'a list
>>
<<
val flatten : 'a list list -> 'a list
>>
<<
val iter : f:('a -> unit) -> 'a list -> unit
>>
<<
val map : f:('a -> 'b) -> 'a list -> 'b list
>>
<<
val rev_map : f:('a -> 'b) -> 'a list -> 'b list
>>
<<
val fold_left : f:('a -> 'b -> 'a) -> init:'a -> 'b list -> 'a
>>
<<
val fold_right : f:('a -> 'b -> 'b) -> 'a list -> init:'b -> 'b
>>
<<
val iter2 : f:('a -> 'b -> unit) -> 'a list -> 'b list -> unit
>>
<<
val map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
>>
<<
val rev_map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
>>
<<
val fold_left2 :
f:('a -> 'b -> 'c -> 'a) -> init:'a -> 'b list -> 'c list -> 'a
>>
<<
val fold_right2 :
f:('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> init:'c -> 'c
>>
<<
val for_all : f:('a -> bool) -> 'a list -> bool
>>
<<
val exists : f:('a -> bool) -> 'a list -> bool
>>
<<
val for_all2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
>>
<<
val exists2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
>>
<<
val mem : 'a -> set:'a list -> bool
>>
<<
val memq : 'a -> set:'a list -> bool
>>
<<
val find : f:('a -> bool) -> 'a list -> 'a
>>
<<
val filter : f:('a -> bool) -> 'a list -> 'a list
>>
<<
val find_all : f:('a -> bool) -> 'a list -> 'a list
>>
<<
val partition : f:('a -> bool) -> 'a list -> 'a list * 'a list
>>
<<
val assoc : 'a -> ('a * 'b) list -> 'b
>>
<<
val assq : 'a -> ('a * 'b) list -> 'b
>>
<<
val mem_assoc : 'a -> map:('a * 'b) list -> bool
>>
<<
val mem_assq : 'a -> map:('a * 'b) list -> bool
>>
<<
val remove_assoc : 'a -> ('a * 'b) list -> ('a * 'b) list
>>
<<
val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list
>>
<<
val split : ('a * 'b) list -> 'a list * 'b list
>>
<<
val combine : 'a list -> 'b list -> ('a * 'b) list
>>
<<
val sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
>>
<<
val stable_sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
>>
<<
val fast_sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
>>
<<
val merge : cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list
>>
end
<<
module String : >>
sig
<<
val length : string -> int
>>
<<
val get : string -> int -> char
>>
<<
val set : string -> int -> char -> unit
>>
<<
val create : int -> string
>>
<<
val make : int -> char -> string
>>
<<
val copy : string -> string
>>
<<
val sub : string -> pos:int -> len:int -> string
>>
<<
val fill : string -> pos:int -> len:int -> char -> unit
>>
<<
val blit :
src:string -> src_pos:int -> dst:string -> dst_pos:int -> len:int ->
unit
>>
<<
val concat : sep:string -> string list -> string
>>
<<
val iter : f:(char -> unit) -> string -> unit
>>
<<
val escaped : string -> string
>>
<<
val index : string -> char -> int
>>
<<
val rindex : string -> char -> int
>>
<<
val index_from : string -> int -> char -> int
>>
<<
val rindex_from : string -> int -> char -> int
>>
<<
val contains : string -> char -> bool
>>
<<
val contains_from : string -> int -> char -> bool
>>
<<
val rcontains_from : string -> int -> char -> bool
>>
<<
val uppercase : string -> string
>>
<<
val lowercase : string -> string
>>
<<
val capitalize : string -> string
>>
<<
val uncapitalize : string -> string
>>
<<
type t = string
>>
<<
val compare : t -> t -> int
>>
<<
val unsafe_get : string -> int -> char
>>
<<
val unsafe_set : string -> int -> char -> unit
>>
<<
val unsafe_blit :
src:string -> src_pos:int -> dst:string -> dst_pos:int -> len:int ->
unit
>>
<<
val unsafe_fill : string -> pos:int -> len:int -> char -> unit
>>
end
20.32 Module Stream : Streams and parsers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
type 'a t
>>
The type of streams holding values of type 'a.
<<
exception Failure
>>
Raised by parsers when none of the first components of the stream patterns
is accepted.
<<
exception Error of string
>>
Raised by parsers when the first component of a stream pattern is accepted,
but one of the following components is rejected.
Stream builders
===============
Warning: these functions create streams with fast access; it is illegal to
mix them with streams built with [< >]; would raise Failure when accessing such
mixed streams.
<<
val from : (int -> 'a option) -> 'a t
>>
Stream.from f returns a stream built from the function f. To create a new
stream element, the function f is called with the current stream count. The
user function f must return either Some <value> for a value or None to
specify the end of the stream.
<<
val of_list : 'a list -> 'a t
>>
Return the stream holding the elements of the list in the same order.
<<
val of_string : string -> char t
>>
Return the stream of the characters of the string parameter.
<<
val of_channel : Pervasives.in_channel -> char t
>>
Return the stream of the characters read from the input channel.
Stream iterator
===============
<<
val iter : ('a -> unit) -> 'a t -> unit
>>
Stream.iter f s scans the whole stream s, applying function f in turn to
each stream element encountered.
Predefined parsers
==================
<<
val next : 'a t -> 'a
>>
Return the first element of the stream and remove it from the stream. Raise
Stream.Failure if the stream is empty.
<<
val empty : 'a t -> unit
>>
Return () if the stream is empty, else raise Stream.Failure.
Useful functions
================
<<
val peek : 'a t -> 'a option
>>
Return Some of "the first element" of the stream, or None if the stream is
empty.
<<
val junk : 'a t -> unit
>>
Remove the first element of the stream, possibly unfreezing it before.
<<
val count : 'a t -> int
>>
Return the current count of the stream elements, i.e. the number of the
stream elements discarded.
<<
val npeek : int -> 'a t -> 'a list
>>
npeek n returns the list of the n first elements of the stream, or all its
remaining elements if less than n elements are available.
20.33 Module String : String operations.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
val length : string -> int
>>
Return the length (number of characters) of the given string.
<<
val get : string -> int -> char
>>
String.get s n returns character number n in string s. The first character
is character number 0. The last character is character number String.length
s - 1. You can also write s.[n] instead of String.get s n.
Raise Invalid_argument "index out of bounds" if n is outside the range 0 to
(String.length s - 1).
<<
val set : string -> int -> char -> unit
>>
String.set s n c modifies string s in place, replacing the character number
n by c. You can also write s.[n] <- c instead of String.set s n c. Raise
Invalid_argument "index out of bounds" if n is outside the range 0 to
(String.length s - 1).
<<
val create : int -> string
>>
String.create n returns a fresh string of length n. The string initially
contains arbitrary characters. Raise Invalid_argument if n < 0 or n >
Sys.max_string_length.
<<
val make : int -> char -> string
>>
String.make n c returns a fresh string of length n, filled with the
character c. Raise Invalid_argument if n < 0 or n >
Sys.max_string_length[20.34].
<<
val copy : string -> string
>>
Return a copy of the given string.
<<
val sub : string -> int -> int -> string
>>
String.sub s start len returns a fresh string of length len, containing the
characters number start to start + len - 1 of string s. Raise
Invalid_argument if start and len do not designate a valid substring of s;
that is, if start < 0, or len < 0, or start + len > String.length[20.33] s.
<<
val fill : string -> int -> int -> char -> unit
>>
String.fill s start len c modifies string s in place, replacing the
characters number start to start + len - 1 by c. Raise Invalid_argument if
start and len do not designate a valid substring of s.
<<
val blit : string -> int -> string -> int -> int -> unit
>>
String.blit src srcoff dst dstoff len copies len characters from string
src, starting at character number srcoff, to string dst, starting at
character number dstoff. It works correctly even if src and dst are the same
string, and the source and destination chunks overlap. Raise
Invalid_argument if srcoff and len do not designate a valid substring of
src, or if dstoff and len do not designate a valid substring of dst.
<<
val concat : string -> string list -> string
>>
String.concat sep sl concatenates the list of strings sl, inserting the
separator string sep between each.
<<
val iter : (char -> unit) -> string -> unit
>>
String.iter f s applies function f in turn to all the characters of s. It
is equivalent to f s.[0]; f s.[1]; ...; f s.[String.length s - 1]; ().
<<
val escaped : string -> string
>>
Return a copy of the argument, with special characters represented by
escape sequences, following the lexical conventions of Objective Caml. If
there is no special character in the argument, return the original string
itself, not a copy.
<<
val index : string -> char -> int
>>
String.index s c returns the position of the leftmost occurrence of
character c in string s. Raise Not_found if c does not occur in s.
<<
val rindex : string -> char -> int
>>
String.rindex s c returns the position of the rightmost occurrence of
character c in string s. Raise Not_found if c does not occur in s.
<<
val index_from : string -> int -> char -> int
>>
Same as String.index[20.33], but start searching at the character position
given as second argument. String.index s c is equivalent to
String.index_from s 0 c.
<<
val rindex_from : string -> int -> char -> int
>>
Same as String.rindex[20.33], but start searching at the character position
given as second argument. String.rindex s c is equivalent to
String.rindex_from s (String.length s - 1) c.
<<
val contains : string -> char -> bool
>>
String.contains s c tests if character c appears in the string s.
<<
val contains_from : string -> int -> char -> bool
>>
String.contains_from s start c tests if character c appears in the
substring of s starting from start to the end of s. Raise Invalid_argument
if start is not a valid index of s.
<<
val rcontains_from : string -> int -> char -> bool
>>
String.rcontains_from s stop c tests if character c appears in the
substring of s starting from the beginning of s to index stop. Raise
Invalid_argument if stop is not a valid index of s.
<<
val uppercase : string -> string
>>
Return a copy of the argument, with all lowercase letters translated to
uppercase, including accented letters of the ISO Latin-1 (8859-1) character
set.
<<
val lowercase : string -> string
>>
Return a copy of the argument, with all uppercase letters translated to
lowercase, including accented letters of the ISO Latin-1 (8859-1) character
set.
<<
val capitalize : string -> string
>>
Return a copy of the argument, with the first character set to uppercase.
<<
val uncapitalize : string -> string
>>
Return a copy of the argument, with the first character set to lowercase.
<<
type t = string
>>
An alias for the type of strings.
<<
val compare : t -> t -> int
>>
The comparison function for strings, with the same specification as
Pervasives.compare[19.2]. Along with the type t, this function compare
allows the module String to be passed as argument to the functors
Set.Make[20.28] and Map.Make[20.18].
20.34 Module Sys : System interface.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
val argv : string array
>>
The command line arguments given to the process. The first element is the
command name used to invoke the program. The following elements are the
command-line arguments given to the program.
<<
val executable_name : string
>>
The name of the file containing the executable currently running.
<<
val file_exists : string -> bool
>>
Test if a file with the given name exists.
<<
val is_directory : string -> bool
>>
Returns true if the given name refers to a directory, false if it refers to
another kind of file. Raise Sys_error if no file exists with the given name.
<<
val remove : string -> unit
>>
Remove the given file name from the file system.
<<
val rename : string -> string -> unit
>>
Rename a file. The first argument is the old name and the second is the new
name. If there is already another file under the new name, rename may
replace it, or raise an exception, depending on your operating system.
<<
val getenv : string -> string
>>
Return the value associated to a variable in the process environment. Raise
Not_found if the variable is unbound.
<<
val command : string -> int
>>
Execute the given shell command and return its exit code.
<<
val time : unit -> float
>>
Return the processor time, in seconds, used by the program since the
beginning of execution.
<<
val chdir : string -> unit
>>
Change the current working directory of the process.
<<
val getcwd : unit -> string
>>
Return the current working directory of the process.
<<
val readdir : string -> string array
>>
Return the names of all files present in the given directory. Names
denoting the current directory and the parent directory ("." and ".." in
Unix) are not returned. Each string in the result is a file name rather than
a complete path. There is no guarantee that the name strings in the
resulting array will appear in any specific order; they are not, in
particular, guaranteed to appear in alphabetical order.
<<
val interactive : bool Pervasives.ref
>>
This reference is initially set to false in standalone programs and to true
if the code is being executed under the interactive toplevel system ocaml.
<<
val os_type : string
>>
Operating system currently executing the Caml program. One of
- "Unix" (for all Unix versions, including Linux and Mac OS X),
- "Win32" (for MS-Windows, OCaml compiled with MSVC++ or Mingw),
- "Cygwin" (for MS-Windows, OCaml compiled with Cygwin).
<<
val word_size : int
>>
Size of one word on the machine currently executing the Caml program, in
bits: 32 or 64.
<<
val max_string_length : int
>>
Maximum length of a string.
<<
val max_array_length : int
>>
Maximum length of a normal array. The maximum length of a float array is
max_array_length/2 on 32-bit machines and max_array_length on 64-bit
machines.
Signal handling
===============
<<
type signal_behavior =
| Signal_default
| Signal_ignore
| Signal_handle of (int -> unit)
>>
What to do when receiving a signal:
- Signal_default: take the default behavior (usually: abort the program)
- Signal_ignore: ignore the signal
- Signal_handle f: call function f, giving it the signal number as
argument.
<<
val signal : int -> signal_behavior -> signal_behavior
>>
Set the behavior of the system on receipt of a given signal. The first
argument is the signal number. Return the behavior previously associated
with the signal. If the signal number is invalid (or not available on your
system), an Invalid_argument exception is raised.
<<
val set_signal : int -> signal_behavior -> unit
>>
Same as Sys.signal[20.34] but return value is ignored.
Signal numbers for the standard POSIX signals.
----------------------------------------------
<<
val sigabrt : int
>>
Abnormal termination
<<
val sigalrm : int
>>
Timeout
<<
val sigfpe : int
>>
Arithmetic exception
<<
val sighup : int
>>
Hangup on controlling terminal
<<
val sigill : int
>>
Invalid hardware instruction
<<
val sigint : int
>>
Interactive interrupt (ctrl-C)
<<
val sigkill : int
>>
Termination (cannot be ignored)
<<
val sigpipe : int
>>
Broken pipe
<<
val sigquit : int
>>
Interactive termination
<<
val sigsegv : int
>>
Invalid memory reference
<<
val sigterm : int
>>
Termination
<<
val sigusr1 : int
>>
Application-defined signal 1
<<
val sigusr2 : int
>>
Application-defined signal 2
<<
val sigchld : int
>>
Child process terminated
<<
val sigcont : int
>>
Continue
<<
val sigstop : int
>>
Stop
<<
val sigtstp : int
>>
Interactive stop
<<
val sigttin : int
>>
Terminal read from background process
<<
val sigttou : int
>>
Terminal write from background process
<<
val sigvtalrm : int
>>
Timeout in virtual time
<<
val sigprof : int
>>
Profiling interrupt
<<
exception Break
>>
Exception raised on interactive interrupt if Sys.catch_break[20.34] is on.
<<
val catch_break : bool -> unit
>>
catch_break governs whether interactive interrupt (ctrl-C) terminates the
program or raises the Break exception. Call catch_break true to enable
raising Break, and catch_break false to let the system terminate the program
on user interrupt.
<<
val ocaml_version : string
>>
ocaml_version is the version of Objective Caml. It is a string of the form
"major.minor[.patchlevel][+additional-info]", where major, minor, and
patchlevel are integers, and additional-info is an arbitrary string. The
[.patchlevel] and [+additional-info] parts may be absent.
20.35 Module Weak : Arrays of weak pointers and hash tables of weak pointers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Low-level functions
===================
<<
type 'a t
>>
The type of arrays of weak pointers (weak arrays). A weak pointer is a
value that the garbage collector may erase at any time. A weak pointer is
said to be full if it points to a value, empty if the value was erased by
the GC. Note that weak arrays cannot be marshaled using
Pervasives.output_value[19.2] or the functions of the Marshal[20.19] module.
<<
val create : int -> 'a t
>>
Weak.create n returns a new weak array of length n. All the pointers are
initially empty. Raise Invalid_argument if n is negative or greater than
Sys.max_array_length[20.34]-1.
<<
val length : 'a t -> int
>>
Weak.length ar returns the length (number of elements) of ar.
<<
val set : 'a t -> int -> 'a option -> unit
>>
Weak.set ar n (Some el) sets the nth cell of ar to be a (full) pointer to
el; Weak.set ar n None sets the nth cell of ar to empty. Raise
Invalid_argument "Weak.set" if n is not in the range 0 to Weak.length[20.35]
a - 1.
<<
val get : 'a t -> int -> 'a option
>>
Weak.get ar n returns None if the nth cell of ar is empty, Some x (where x
is the value) if it is full. Raise Invalid_argument "Weak.get" if n is not
in the range 0 to Weak.length[20.35] a - 1.
<<
val get_copy : 'a t -> int -> 'a option
>>
Weak.get_copy ar n returns None if the nth cell of ar is empty, Some x
(where x is a (shallow) copy of the value) if it is full. In addition to
pitfalls with mutable values, the interesting difference with get is that
get_copy does not prevent the incremental GC from erasing the value in its
current cycle (get may delay the erasure to the next GC cycle). Raise
Invalid_argument "Weak.get" if n is not in the range 0 to Weak.length[20.35]
a - 1.
<<
val check : 'a t -> int -> bool
>>
Weak.check ar n returns true if the nth cell of ar is full, false if it is
empty. Note that even if Weak.check ar n returns true, a subsequent
Weak.get[20.35] ar n can return None.
<<
val fill : 'a t -> int -> int -> 'a option -> unit
>>
Weak.fill ar ofs len el sets to el all pointers of ar from ofs to ofs + len
- 1. Raise Invalid_argument "Weak.fill" if ofs and len do not designate a
valid subarray of a.
<<
val blit : 'a t -> int -> 'a t -> int -> int -> unit
>>
Weak.blit ar1 off1 ar2 off2 len copies len weak pointers from ar1 (starting
at off1) to ar2 (starting at off2). It works correctly even if ar1 and ar2
are the same. Raise Invalid_argument "Weak.blit" if off1 and len do not
designate a valid subarray of ar1, or if off2 and len do not designate a
valid subarray of ar2.
Weak hash tables
================
A weak hash table is a hashed set of values. Each value may magically
disappear from the set when it is not used by the rest of the program any more.
This is normally used to share data structures without inducing memory leaks.
Weak hash tables are defined on values from a Hashtbl.HashedType[20.12] module;
the equal relation and hash function are taken from that module. We will say
that v is an instance of x if equal x v is true.
The equal relation must be able to work on a shallow copy of the values and
give the same result as with the values themselves.
<<
module type S = >>
sig
<<
type data
>>
The type of the elements stored in the table.
<<
type t
>>
The type of tables that contain elements of type data. Note that weak
hash tables cannot be marshaled using Pervasives.output_value[19.2] or
the functions of the Marshal[20.19] module.
<<
val create : int -> t
>>
create n creates a new empty weak hash table, of initial size n. The
table will grow as needed.
<<
val clear : t -> unit
>>
Remove all elements from the table.
<<
val merge : t -> data -> data
>>
merge t x returns an instance of x found in t if any, or else adds x to
t and return x.
<<
val add : t -> data -> unit
>>
add t x adds x to t. If there is already an instance of x in t, it is
unspecified which one will be returned by subsequent calls to find and
merge.
<<
val remove : t -> data -> unit
>>
remove t x removes from t one instance of x. Does nothing if there is no
instance of x in t.
<<
val find : t -> data -> data
>>
find t x returns an instance of x found in t. Raise Not_found if there
is no such element.
<<
val find_all : t -> data -> data list
>>
find_all t x returns a list of all the instances of x found in t.
<<
val mem : t -> data -> bool
>>
mem t x returns true if there is at least one instance of x in t, false
otherwise.
<<
val iter : (data -> unit) -> t -> unit
>>
iter f t calls f on each element of t, in some unspecified order. It is
not specified what happens if f tries to change t itself.
<<
val fold : (data -> 'a -> 'a) -> t -> 'a -> 'a
>>
fold f t init computes (f d1 (... (f dN init))) where d1 ... dN are the
elements of t in some unspecified order. It is not specified what happens
if f tries to change t itself.
<<
val count : t -> int
>>
Count the number of elements in the table. count t gives the same result
as fold (fun _ n -> n+1) t 0 but does not delay the deallocation of the
dead elements.
<<
val stats : t -> int * int * int * int * int * int
>>
Return statistics on the table. The numbers are, in order: table length,
number of entries, sum of bucket lengths, smallest bucket length, median
bucket length, biggest bucket length.
end
The output signature of the functor Weak.Make[20.35].
<<
module Make : >>
functor (H : Hashtbl.HashedType) -> S with type data = H.t
Functor building an implementation of the weak hash table structure.
Chapter 21 The unix library: Unix system calls
*************************************************
The unix library makes many Unix system calls and system-related library
functions available to Objective Caml programs. This chapter describes briefly
the functions provided. Refer to sections 2 and 3 of the Unix manual for more
details on the behavior of these functions.
Not all functions are provided by all Unix variants. If some functions are
not available, they will raise Invalid_arg when called.
Programs that use the unix library must be linked as follows:
<<
ocamlc other options unix.cma other files
ocamlopt other options unix.cmxa other files
>>
For interactive use of the unix library, do:
<<
ocamlmktop -o mytop unix.cma
./mytop
>>
or (if dynamic linking of C libraries is supported on your platform), start
ocaml and type #load "unix.cma";;.
Windows:
A fairly complete emulation of the Unix system calls is provided in the
Windows version of Objective Caml. The end of this chapter gives more
information on the functions that are not supported under Windows.
21.1 Module Unix : Interface to the Unix system
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Error report
============
<<
type error =
| E2BIG
>>
Argument list too long
<<
| EACCES
>>
Permission denied
<<
| EAGAIN
>>
Resource temporarily unavailable; try again
<<
| EBADF
>>
Bad file descriptor
<<
| EBUSY
>>
Resource unavailable
<<
| ECHILD
>>
No child process
<<
| EDEADLK
>>
Resource deadlock would occur
<<
| EDOM
>>
Domain error for math functions, etc.
<<
| EEXIST
>>
File exists
<<
| EFAULT
>>
Bad address
<<
| EFBIG
>>
File too large
<<
| EINTR
>>
Function interrupted by signal
<<
| EINVAL
>>
Invalid argument
<<
| EIO
>>
Hardware I/O error
<<
| EISDIR
>>
Is a directory
<<
| EMFILE
>>
Too many open files by the process
<<
| EMLINK
>>
Too many links
<<
| ENAMETOOLONG
>>
Filename too long
<<
| ENFILE
>>
Too many open files in the system
<<
| ENODEV
>>
No such device
<<
| ENOENT
>>
No such file or directory
<<
| ENOEXEC
>>
Not an executable file
<<
| ENOLCK
>>
No locks available
<<
| ENOMEM
>>
Not enough memory
<<
| ENOSPC
>>
No space left on device
<<
| ENOSYS
>>
Function not supported
<<
| ENOTDIR
>>
Not a directory
<<
| ENOTEMPTY
>>
Directory not empty
<<
| ENOTTY
>>
Inappropriate I/O control operation
<<
| ENXIO
>>
No such device or address
<<
| EPERM
>>
Operation not permitted
<<
| EPIPE
>>
Broken pipe
<<
| ERANGE
>>
Result too large
<<
| EROFS
>>
Read-only file system
<<
| ESPIPE
>>
Invalid seek e.g. on a pipe
<<
| ESRCH
>>
No such process
<<
| EXDEV
>>
Invalid link
<<
| EWOULDBLOCK
>>
Operation would block
<<
| EINPROGRESS
>>
Operation now in progress
<<
| EALREADY
>>
Operation already in progress
<<
| ENOTSOCK
>>
Socket operation on non-socket
<<
| EDESTADDRREQ
>>
Destination address required
<<
| EMSGSIZE
>>
Message too long
<<
| EPROTOTYPE
>>
Protocol wrong type for socket
<<
| ENOPROTOOPT
>>
Protocol not available
<<
| EPROTONOSUPPORT
>>
Protocol not supported
<<
| ESOCKTNOSUPPORT
>>
Socket type not supported
<<
| EOPNOTSUPP
>>
Operation not supported on socket
<<
| EPFNOSUPPORT
>>
Protocol family not supported
<<
| EAFNOSUPPORT
>>
Address family not supported by protocol family
<<
| EADDRINUSE
>>
Address already in use
<<
| EADDRNOTAVAIL
>>
Can't assign requested address
<<
| ENETDOWN
>>
Network is down
<<
| ENETUNREACH
>>
Network is unreachable
<<
| ENETRESET
>>
Network dropped connection on reset
<<
| ECONNABORTED
>>
Software caused connection abort
<<
| ECONNRESET
>>
Connection reset by peer
<<
| ENOBUFS
>>
No buffer space available
<<
| EISCONN
>>
Socket is already connected
<<
| ENOTCONN
>>
Socket is not connected
<<
| ESHUTDOWN
>>
Can't send after socket shutdown
<<
| ETOOMANYREFS
>>
Too many references: can't splice
<<
| ETIMEDOUT
>>
Connection timed out
<<
| ECONNREFUSED
>>
Connection refused
<<
| EHOSTDOWN
>>
Host is down
<<
| EHOSTUNREACH
>>
No route to host
<<
| ELOOP
>>
Too many levels of symbolic links
<<
| EOVERFLOW
>>
File size or position not representable
<<
| EUNKNOWNERR of int
>>
Unknown error
The type of error codes. Errors defined in the POSIX standard and
additional errors from UNIX98 and BSD. All other errors are mapped to
EUNKNOWNERR.
<<
exception Unix_error of error * string * string
>>
Raised by the system calls below when an error is encountered. The first
component is the error code; the second component is the function name; the
third component is the string parameter to the function, if it has one, or
the empty string otherwise.
<<
val error_message : error -> string
>>
Return a string describing the given error code.
<<
val handle_unix_error : ('a -> 'b) -> 'a -> 'b
>>
handle_unix_error f x applies f to x and returns the result. If the
exception Unix_error is raised, it prints a message describing the error and
exits with code 2.
Access to the process environment
=================================
<<
val environment : unit -> string array
>>
Return the process environment, as an array of strings with the format
"variable=value".
<<
val getenv : string -> string
>>
Return the value associated to a variable in the process environment. Raise
Not_found if the variable is unbound. (This function is identical to
Sys.getenv.)
<<
val putenv : string -> string -> unit
>>
Unix.putenv name value sets the value associated to a variable in the
process environment. name is the name of the environment variable, and value
its new associated value.
Process handling
================
<<
type process_status =
| WEXITED of int
>>
The process terminated normally by exit; the argument is the return code.
<<
| WSIGNALED of int
>>
The process was killed by a signal; the argument is the signal number.
<<
| WSTOPPED of int
>>
The process was stopped by a signal; the argument is the signal number.
The termination status of a process.
<<
type wait_flag =
| WNOHANG
>>
do not block if no child has died yet, but immediately return with a pid
equal to 0.
<<
| WUNTRACED
>>
report also the children that receive stop signals.
Flags for Unix.waitpid[21.1].
<<
val execv : string -> string array -> 'a
>>
execv prog args execute the program in file prog, with the arguments args,
and the current process environment. These execv* functions never return: on
success, the current program is replaced by the new one; on failure, a
Unix.Unix_error[21.1] exception is raised.
<<
val execve : string -> string array -> string array -> 'a
>>
Same as Unix.execv[21.1], except that the third argument provides the
environment to the program executed.
<<
val execvp : string -> string array -> 'a
>>
Same as Unix.execv[21.1], except that the program is searched in the path.
<<
val execvpe : string -> string array -> string array -> 'a
>>
Same as Unix.execve[21.1], except that the program is searched in the path.
<<
val fork : unit -> int
>>
Fork a new process. The returned integer is 0 for the child process, the
pid of the child process for the parent process.
<<
val wait : unit -> int * process_status
>>
Wait until one of the children processes die, and return its pid and
termination status.
<<
val waitpid : wait_flag list -> int -> int * process_status
>>
Same as Unix.wait[21.1], but waits for the child process whose pid is
given. A pid of -1 means wait for any child. A pid of 0 means wait for any
child in the same process group as the current process. Negative pid
arguments represent process groups. The list of options indicates whether
waitpid should return immediately without waiting, or also report stopped
children.
<<
val system : string -> process_status
>>
Execute the given command, wait until it terminates, and return its
termination status. The string is interpreted by the shell /bin/sh and
therefore can contain redirections, quotes, variables, etc. The result
WEXITED 127 indicates that the shell couldn't be executed.
<<
val getpid : unit -> int
>>
Return the pid of the process.
<<
val getppid : unit -> int
>>
Return the pid of the parent process.
<<
val nice : int -> int
>>
Change the process priority. The integer argument is added to the "nice"
value. (Higher values of the "nice" value mean lower priorities.) Return the
new nice value.
Basic file input/output
=======================
<<
type file_descr
>>
The abstract type of file descriptors.
<<
val stdin : file_descr
>>
File descriptor for standard input.
<<
val stdout : file_descr
>>
File descriptor for standard output.
<<
val stderr : file_descr
>>
File descriptor for standard error.
<<
type open_flag =
| O_RDONLY
>>
Open for reading
<<
| O_WRONLY
>>
Open for writing
<<
| O_RDWR
>>
Open for reading and writing
<<
| O_NONBLOCK
>>
Open in non-blocking mode
<<
| O_APPEND
>>
Open for append
<<
| O_CREAT
>>
Create if nonexistent
<<
| O_TRUNC
>>
Truncate to 0 length if existing
<<
| O_EXCL
>>
Fail if existing
<<
| O_NOCTTY
>>
Don't make this dev a controlling tty
<<
| O_DSYNC
>>
Writes complete as `Synchronised I/O data integrity completion'
<<
| O_SYNC
>>
Writes complete as `Synchronised I/O file integrity completion'
<<
| O_RSYNC
>>
Reads complete as writes (depending on O_SYNC/O_DSYNC)
The flags to Unix.openfile[21.1].
<<
type file_perm = int
>>
The type of file access rights, e.g. 0o640 is read and write for user, read
for group, none for others
<<
val openfile : string -> open_flag list -> file_perm -> file_descr
>>
Open the named file with the given flags. Third argument is the permissions
to give to the file if it is created. Return a file descriptor on the named
file.
<<
val close : file_descr -> unit
>>
Close a file descriptor.
<<
val read : file_descr -> string -> int -> int -> int
>>
read fd buff ofs len reads len characters from descriptor fd, storing them
in string buff, starting at position ofs in string buff. Return the number
of characters actually read.
<<
val write : file_descr -> string -> int -> int -> int
>>
write fd buff ofs len writes len characters to descriptor fd, taking them
from string buff, starting at position ofs in string buff. Return the number
of characters actually written. write repeats the writing operation until
all characters have been written or an error occurs.
<<
val single_write : file_descr -> string -> int -> int -> int
>>
Same as write, but attempts to write only once. Thus, if an error occurs,
single_write guarantees that no data has been written.
Interfacing with the standard input/output library
==================================================
<<
val in_channel_of_descr : file_descr -> Pervasives.in_channel
>>
Create an input channel reading from the given descriptor. The channel is
initially in binary mode; use set_binary_mode_in ic false if text mode is
desired.
<<
val out_channel_of_descr : file_descr -> Pervasives.out_channel
>>
Create an output channel writing on the given descriptor. The channel is
initially in binary mode; use set_binary_mode_out oc false if text mode is
desired.
<<
val descr_of_in_channel : Pervasives.in_channel -> file_descr
>>
Return the descriptor corresponding to an input channel.
<<
val descr_of_out_channel : Pervasives.out_channel -> file_descr
>>
Return the descriptor corresponding to an output channel.
Seeking and truncating
======================
<<
type seek_command =
| SEEK_SET
>>
indicates positions relative to the beginning of the file
<<
| SEEK_CUR
>>
indicates positions relative to the current position
<<
| SEEK_END
>>
indicates positions relative to the end of the file
Positioning modes for Unix.lseek[21.1].
<<
val lseek : file_descr -> int -> seek_command -> int
>>
Set the current position for a file descriptor
<<
val truncate : string -> int -> unit
>>
Truncates the named file to the given size.
<<
val ftruncate : file_descr -> int -> unit
>>
Truncates the file corresponding to the given descriptor to the given size.
File status
===========
<<
type file_kind =
| S_REG
>>
Regular file
<<
| S_DIR
>>
Directory
<<
| S_CHR
>>
Character device
<<
| S_BLK
>>
Block device
<<
| S_LNK
>>
Symbolic link
<<
| S_FIFO
>>
Named pipe
<<
| S_SOCK
>>
Socket
<<
type stats = {
st_dev : int ;
>>
Device number
<<
st_ino : int ;
>>
Inode number
<<
st_kind : file_kind ;
>>
Kind of the file
<<
st_perm : file_perm ;
>>
Access rights
<<
st_nlink : int ;
>>
Number of links
<<
st_uid : int ;
>>
User id of the owner
<<
st_gid : int ;
>>
Group ID of the file's group
<<
st_rdev : int ;
>>
Device minor number
<<
st_size : int ;
>>
Size in bytes
<<
st_atime : float ;
>>
Last access time
<<
st_mtime : float ;
>>
Last modification time
<<
st_ctime : float ;
>>
Last status change time
<<
}
>>
The informations returned by the Unix.stat[21.1] calls.
<<
val stat : string -> stats
>>
Return the information for the named file.
<<
val lstat : string -> stats
>>
Same as Unix.stat[21.1], but in case the file is a symbolic link, return
the information for the link itself.
<<
val fstat : file_descr -> stats
>>
Return the information for the file associated with the given descriptor.
<<
val isatty : file_descr -> bool
>>
Return true if the given file descriptor refers to a terminal or console
window, false otherwise.
File operations on large files
==============================
<<
module LargeFile : >>
sig
<<
val lseek : Unix.file_descr -> int64 -> Unix.seek_command -> int64
>>
<<
val truncate : string -> int64 -> unit
>>
<<
val ftruncate : Unix.file_descr -> int64 -> unit
>>
<<
type stats = {
st_dev : int ;
>>
Device number
<<
st_ino : int ;
>>
Inode number
<<
st_kind : Unix.file_kind ;
>>
Kind of the file
<<
st_perm : Unix.file_perm ;
>>
Access rights
<<
st_nlink : int ;
>>
Number of links
<<
st_uid : int ;
>>
User id of the owner
<<
st_gid : int ;
>>
Group ID of the file's group
<<
st_rdev : int ;
>>
Device minor number
<<
st_size : int64 ;
>>
Size in bytes
<<
st_atime : float ;
>>
Last access time
<<
st_mtime : float ;
>>
Last modification time
<<
st_ctime : float ;
>>
Last status change time
<<
}
>>
<<
val stat : string -> stats
>>
<<
val lstat : string -> stats
>>
<<
val fstat : Unix.file_descr -> stats
>>
end
File operations on large files. This sub-module provides 64-bit variants of
the functions Unix.lseek[21.1] (for positioning a file descriptor),
Unix.truncate[21.1] and Unix.ftruncate[21.1] (for changing the size of a
file), and Unix.stat[21.1], Unix.lstat[21.1] and Unix.fstat[21.1] (for
obtaining information on files). These alternate functions represent
positions and sizes by 64-bit integers (type int64) instead of regular
integers (type int), thus allowing operating on files whose sizes are
greater than max_int.
Operations on file names
========================
<<
val unlink : string -> unit
>>
Removes the named file
<<
val rename : string -> string -> unit
>>
rename old new changes the name of a file from old to new.
<<
val link : string -> string -> unit
>>
link source dest creates a hard link named dest to the file named source.
File permissions and ownership
==============================
<<
type access_permission =
| R_OK
>>
Read permission
<<
| W_OK
>>
Write permission
<<
| X_OK
>>
Execution permission
<<
| F_OK
>>
File exists
Flags for the Unix.access[21.1] call.
<<
val chmod : string -> file_perm -> unit
>>
Change the permissions of the named file.
<<
val fchmod : file_descr -> file_perm -> unit
>>
Change the permissions of an opened file.
<<
val chown : string -> int -> int -> unit
>>
Change the owner uid and owner gid of the named file.
<<
val fchown : file_descr -> int -> int -> unit
>>
Change the owner uid and owner gid of an opened file.
<<
val umask : int -> int
>>
Set the process's file mode creation mask, and return the previous mask.
<<
val access : string -> access_permission list -> unit
>>
Check that the process has the given permissions over the named file. Raise
Unix_error otherwise.
Operations on file descriptors
==============================
<<
val dup : file_descr -> file_descr
>>
Return a new file descriptor referencing the same file as the given
descriptor.
<<
val dup2 : file_descr -> file_descr -> unit
>>
dup2 fd1 fd2 duplicates fd1 to fd2, closing fd2 if already opened.
<<
val set_nonblock : file_descr -> unit
>>
Set the "non-blocking" flag on the given descriptor. When the non-blocking
flag is set, reading on a descriptor on which there is temporarily no data
available raises the EAGAIN or EWOULDBLOCK error instead of blocking;
writing on a descriptor on which there is temporarily no room for writing
also raises EAGAIN or EWOULDBLOCK.
<<
val clear_nonblock : file_descr -> unit
>>
Clear the "non-blocking" flag on the given descriptor. See
Unix.set_nonblock[21.1].
<<
val set_close_on_exec : file_descr -> unit
>>
Set the "close-on-exec" flag on the given descriptor. A descriptor with the
close-on-exec flag is automatically closed when the current process starts
another program with one of the exec functions.
<<
val clear_close_on_exec : file_descr -> unit
>>
Clear the "close-on-exec" flag on the given descriptor. See
Unix.set_close_on_exec[21.1].
Directories
===========
<<
val mkdir : string -> file_perm -> unit
>>
Create a directory with the given permissions.
<<
val rmdir : string -> unit
>>
Remove an empty directory.
<<
val chdir : string -> unit
>>
Change the process working directory.
<<
val getcwd : unit -> string
>>
Return the name of the current working directory.
<<
val chroot : string -> unit
>>
Change the process root directory.
<<
type dir_handle
>>
The type of descriptors over opened directories.
<<
val opendir : string -> dir_handle
>>
Open a descriptor on a directory
<<
val readdir : dir_handle -> string
>>
Return the next entry in a directory.
Raises End_of_file when the end of the directory has been reached.
<<
val rewinddir : dir_handle -> unit
>>
Reposition the descriptor to the beginning of the directory
<<
val closedir : dir_handle -> unit
>>
Close a directory descriptor.
Pipes and redirections
======================
<<
val pipe : unit -> file_descr * file_descr
>>
Create a pipe. The first component of the result is opened for reading,
that's the exit to the pipe. The second component is opened for writing,
that's the entrance to the pipe.
<<
val mkfifo : string -> file_perm -> unit
>>
Create a named pipe with the given permissions.
High-level process and redirection management
=============================================
<<
val create_process :
string ->
string array -> file_descr -> file_descr -> file_descr -> int
>>
create_process prog args new_stdin new_stdout new_stderr forks a new
process that executes the program in file prog, with arguments args. The pid
of the new process is returned immediately; the new process executes
concurrently with the current process. The standard input and outputs of the
new process are connected to the descriptors new_stdin, new_stdout and
new_stderr. Passing e.g. stdout for new_stdout prevents the redirection and
causes the new process to have the same standard output as the current
process. The executable file prog is searched in the path. The new process
has the same environment as the current process.
<<
val create_process_env :
string ->
string array ->
string array -> file_descr -> file_descr -> file_descr -> int
>>
create_process_env prog args env new_stdin new_stdout new_stderr works as
Unix.create_process[21.1], except that the extra argument env specifies the
environment passed to the program.
<<
val open_process_in : string -> Pervasives.in_channel
>>
High-level pipe and process management. This function runs the given
command in parallel with the program. The standard output of the command is
redirected to a pipe, which can be read via the returned input channel. The
command is interpreted by the shell /bin/sh (cf. system).
<<
val open_process_out : string -> Pervasives.out_channel
>>
Same as Unix.open_process_in[21.1], but redirect the standard input of the
command to a pipe. Data written to the returned output channel is sent to
the standard input of the command. Warning: writes on output channels are
buffered, hence be careful to call Pervasives.flush[19.2] at the right times
to ensure correct synchronization.
<<
val open_process : string -> Pervasives.in_channel * Pervasives.out_channel
>>
Same as Unix.open_process_out[21.1], but redirects both the standard input
and standard output of the command to pipes connected to the two returned
channels. The input channel is connected to the output of the command, and
the output channel to the input of the command.
<<
val open_process_full :
string ->
string array ->
Pervasives.in_channel * Pervasives.out_channel * Pervasives.in_channel
>>
Similar to Unix.open_process[21.1], but the second argument specifies the
environment passed to the command. The result is a triple of channels
connected respectively to the standard output, standard input, and standard
error of the command.
<<
val close_process_in : Pervasives.in_channel -> process_status
>>
Close channels opened by Unix.open_process_in[21.1], wait for the
associated command to terminate, and return its termination status.
<<
val close_process_out : Pervasives.out_channel -> process_status
>>
Close channels opened by Unix.open_process_out[21.1], wait for the
associated command to terminate, and return its termination status.
<<
val close_process :
Pervasives.in_channel * Pervasives.out_channel -> process_status
>>
Close channels opened by Unix.open_process[21.1], wait for the associated
command to terminate, and return its termination status.
<<
val close_process_full :
Pervasives.in_channel * Pervasives.out_channel * Pervasives.in_channel ->
process_status
>>
Close channels opened by Unix.open_process_full[21.1], wait for the
associated command to terminate, and return its termination status.
Symbolic links
==============
<<
val symlink : string -> string -> unit
>>
symlink source dest creates the file dest as a symbolic link to the file
source.
<<
val readlink : string -> string
>>
Read the contents of a link.
Polling
=======
<<
val select :
file_descr list ->
file_descr list ->
file_descr list ->
float -> file_descr list * file_descr list * file_descr list
>>
Wait until some input/output operations become possible on some channels.
The three list arguments are, respectively, a set of descriptors to check
for reading (first argument), for writing (second argument), or for
exceptional conditions (third argument). The fourth argument is the maximal
timeout, in seconds; a negative fourth argument means no timeout (unbounded
wait). The result is composed of three sets of descriptors: those ready for
reading (first component), ready for writing (second component), and over
which an exceptional condition is pending (third component).
Locking
=======
<<
type lock_command =
| F_ULOCK
>>
Unlock a region
<<
| F_LOCK
>>
Lock a region for writing, and block if already locked
<<
| F_TLOCK
>>
Lock a region for writing, or fail if already locked
<<
| F_TEST
>>
Test a region for other process locks
<<
| F_RLOCK
>>
Lock a region for reading, and block if already locked
<<
| F_TRLOCK
>>
Lock a region for reading, or fail if already locked
Commands for Unix.lockf[21.1].
<<
val lockf : file_descr -> lock_command -> int -> unit
>>
lockf fd cmd size puts a lock on a region of the file opened as fd. The
region starts at the current read/write position for fd (as set by
Unix.lseek[21.1]), and extends size bytes forward if size is positive, size
bytes backwards if size is negative, or to the end of the file if size is
zero. A write lock prevents any other process from acquiring a read or write
lock on the region. A read lock prevents any other process from acquiring a
write lock on the region, but lets other processes acquire read locks on it.
The F_LOCK and F_TLOCK commands attempts to put a write lock on the
specified region. The F_RLOCK and F_TRLOCK commands attempts to put a read
lock on the specified region. If one or several locks put by another process
prevent the current process from acquiring the lock, F_LOCK and F_RLOCK
block until these locks are removed, while F_TLOCK and F_TRLOCK fail
immediately with an exception. The F_ULOCK removes whatever locks the
current process has on the specified region. Finally, the F_TEST command
tests whether a write lock can be acquired on the specified region, without
actually putting a lock. It returns immediately if successful, or fails
otherwise.
Signals
=======
Note: installation of signal handlers is performed via the functions
Sys.signal[20.34] and Sys.set_signal[20.34].
<<
val kill : int -> int -> unit
>>
kill pid sig sends signal number sig to the process with id pid.
<<
type sigprocmask_command =
| SIG_SETMASK
| SIG_BLOCK
| SIG_UNBLOCK
>>
<<
val sigprocmask : sigprocmask_command -> int list -> int list
>>
sigprocmask cmd sigs changes the set of blocked signals. If cmd is
SIG_SETMASK, blocked signals are set to those in the list sigs. If cmd is
SIG_BLOCK, the signals in sigs are added to the set of blocked signals. If
cmd is SIG_UNBLOCK, the signals in sigs are removed from the set of blocked
signals. sigprocmask returns the set of previously blocked signals.
<<
val sigpending : unit -> int list
>>
Return the set of blocked signals that are currently pending.
<<
val sigsuspend : int list -> unit
>>
sigsuspend sigs atomically sets the blocked signals to sigs and waits for a
non-ignored, non-blocked signal to be delivered. On return, the blocked
signals are reset to their initial value.
<<
val pause : unit -> unit
>>
Wait until a non-ignored, non-blocked signal is delivered.
Time functions
==============
<<
type process_times = {
tms_utime : float ;
>>
User time for the process
<<
tms_stime : float ;
>>
System time for the process
<<
tms_cutime : float ;
>>
User time for the children processes
<<
tms_cstime : float ;
>>
System time for the children processes
<<
}
>>
The execution times (CPU times) of a process.
<<
type tm = {
tm_sec : int ;
>>
Seconds 0..60
<<
tm_min : int ;
>>
Minutes 0..59
<<
tm_hour : int ;
>>
Hours 0..23
<<
tm_mday : int ;
>>
Day of month 1..31
<<
tm_mon : int ;
>>
Month of year 0..11
<<
tm_year : int ;
>>
Year - 1900
<<
tm_wday : int ;
>>
Day of week (Sunday is 0)
<<
tm_yday : int ;
>>
Day of year 0..365
<<
tm_isdst : bool ;
>>
Daylight time savings in effect
<<
}
>>
The type representing wallclock time and calendar date.
<<
val time : unit -> float
>>
Return the current time since 00:00:00 GMT, Jan. 1, 1970, in seconds.
<<
val gettimeofday : unit -> float
>>
Same as Unix.time[21.1], but with resolution better than 1 second.
<<
val gmtime : float -> tm
>>
Convert a time in seconds, as returned by Unix.time[21.1], into a date and
a time. Assumes UTC (Coordinated Universal Time), also known as GMT.
<<
val localtime : float -> tm
>>
Convert a time in seconds, as returned by Unix.time[21.1], into a date and
a time. Assumes the local time zone.
<<
val mktime : tm -> float * tm
>>
Convert a date and time, specified by the tm argument, into a time in
seconds, as returned by Unix.time[21.1]. The tm_isdst, tm_wday and tm_yday
fields of tm are ignored. Also return a normalized copy of the given tm
record, with the tm_wday, tm_yday, and tm_isdst fields recomputed from the
other fields, and the other fields normalized (so that, e.g., 40 October is
changed into 9 November). The tm argument is interpreted in the local time
zone.
<<
val alarm : int -> int
>>
Schedule a SIGALRM signal after the given number of seconds.
<<
val sleep : int -> unit
>>
Stop execution for the given number of seconds.
<<
val times : unit -> process_times
>>
Return the execution times of the process.
<<
val utimes : string -> float -> float -> unit
>>
Set the last access time (second arg) and last modification time (third
arg) for a file. Times are expressed in seconds from 00:00:00 GMT, Jan. 1,
1970.
<<
type interval_timer =
| ITIMER_REAL
>>
decrements in real time, and sends the signal SIGALRM when expired.
<<
| ITIMER_VIRTUAL
>>
decrements in process virtual time, and sends SIGVTALRM when expired.
<<
| ITIMER_PROF
>>
(for profiling) decrements both when the process is running and when the
system is running on behalf of the process; it sends SIGPROF when expired.
The three kinds of interval timers.
<<
type interval_timer_status = {
it_interval : float ;
>>
Period
<<
it_value : float ;
>>
Current value of the timer
<<
}
>>
The type describing the status of an interval timer
<<
val getitimer : interval_timer -> interval_timer_status
>>
Return the current status of the given interval timer.
<<
val setitimer :
interval_timer ->
interval_timer_status -> interval_timer_status
>>
setitimer t s sets the interval timer t and returns its previous status.
The s argument is interpreted as follows: s.it_value, if nonzero, is the
time to the next timer expiration; s.it_interval, if nonzero, specifies a
value to be used in reloading it_value when the timer expires. Setting
s.it_value to zero disable the timer. Setting s.it_interval to zero causes
the timer to be disabled after its next expiration.
User id, group id
=================
<<
val getuid : unit -> int
>>
Return the user id of the user executing the process.
<<
val geteuid : unit -> int
>>
Return the effective user id under which the process runs.
<<
val setuid : int -> unit
>>
Set the real user id and effective user id for the process.
<<
val getgid : unit -> int
>>
Return the group id of the user executing the process.
<<
val getegid : unit -> int
>>
Return the effective group id under which the process runs.
<<
val setgid : int -> unit
>>
Set the real group id and effective group id for the process.
<<
val getgroups : unit -> int array
>>
Return the list of groups to which the user executing the process belongs.
<<
type passwd_entry = {
pw_name : string ;
pw_passwd : string ;
pw_uid : int ;
pw_gid : int ;
pw_gecos : string ;
pw_dir : string ;
pw_shell : string ;
}
>>
Structure of entries in the passwd database.
<<
type group_entry = {
gr_name : string ;
gr_passwd : string ;
gr_gid : int ;
gr_mem : string array ;
}
>>
Structure of entries in the groups database.
<<
val getlogin : unit -> string
>>
Return the login name of the user executing the process.
<<
val getpwnam : string -> passwd_entry
>>
Find an entry in passwd with the given name, or raise Not_found.
<<
val getgrnam : string -> group_entry
>>
Find an entry in group with the given name, or raise Not_found.
<<
val getpwuid : int -> passwd_entry
>>
Find an entry in passwd with the given user id, or raise Not_found.
<<
val getgrgid : int -> group_entry
>>
Find an entry in group with the given group id, or raise Not_found.
Internet addresses
==================
<<
type inet_addr
>>
The abstract type of Internet addresses.
<<
val inet_addr_of_string : string -> inet_addr
>>
Conversion from the printable representation of an Internet address to its
internal representation. The argument string consists of 4 numbers separated
by periods (XXX.YYY.ZZZ.TTT) for IPv4 addresses, and up to 8 numbers
separated by colons for IPv6 addresses. Raise Failure when given a string
that does not match these formats.
<<
val string_of_inet_addr : inet_addr -> string
>>
Return the printable representation of the given Internet address. See
Unix.inet_addr_of_string[21.1] for a description of the printable
representation.
<<
val inet_addr_any : inet_addr
>>
A special IPv4 address, for use only with bind, representing all the
Internet addresses that the host machine possesses.
<<
val inet_addr_loopback : inet_addr
>>
A special IPv4 address representing the host machine (127.0.0.1).
<<
val inet6_addr_any : inet_addr
>>
A special IPv6 address, for use only with bind, representing all the
Internet addresses that the host machine possesses.
<<
val inet6_addr_loopback : inet_addr
>>
A special IPv6 address representing the host machine (::1).
Sockets
=======
<<
type socket_domain =
| PF_UNIX
>>
Unix domain
<<
| PF_INET
>>
Internet domain (IPv4)
<<
| PF_INET6
>>
Internet domain (IPv6)
The type of socket domains.
<<
type socket_type =
| SOCK_STREAM
>>
Stream socket
<<
| SOCK_DGRAM
>>
Datagram socket
<<
| SOCK_RAW
>>
Raw socket
<<
| SOCK_SEQPACKET
>>
Sequenced packets socket
The type of socket kinds, specifying the semantics of communications.
<<
type sockaddr =
| ADDR_UNIX of string
| ADDR_INET of inet_addr * int
>>
The type of socket addresses. ADDR_UNIX name is a socket address in the
Unix domain; name is a file name in the file system. ADDR_INET(addr,port) is
a socket address in the Internet domain; addr is the Internet address of the
machine, and port is the port number.
<<
val socket : socket_domain -> socket_type -> int -> file_descr
>>
Create a new socket in the given domain, and with the given kind. The third
argument is the protocol type; 0 selects the default protocol for that kind
of sockets.
<<
val domain_of_sockaddr : sockaddr -> socket_domain
>>
Return the socket domain adequate for the given socket address.
<<
val socketpair :
socket_domain ->
socket_type -> int -> file_descr * file_descr
>>
Create a pair of unnamed sockets, connected together.
<<
val accept : file_descr -> file_descr * sockaddr
>>
Accept connections on the given socket. The returned descriptor is a socket
connected to the client; the returned address is the address of the
connecting client.
<<
val bind : file_descr -> sockaddr -> unit
>>
Bind a socket to an address.
<<
val connect : file_descr -> sockaddr -> unit
>>
Connect a socket to an address.
<<
val listen : file_descr -> int -> unit
>>
Set up a socket for receiving connection requests. The integer argument is
the maximal number of pending requests.
<<
type shutdown_command =
| SHUTDOWN_RECEIVE
>>
Close for receiving
<<
| SHUTDOWN_SEND
>>
Close for sending
<<
| SHUTDOWN_ALL
>>
Close both
The type of commands for shutdown.
<<
val shutdown : file_descr -> shutdown_command -> unit
>>
Shutdown a socket connection. SHUTDOWN_SEND as second argument causes reads
on the other end of the connection to return an end-of-file condition.
SHUTDOWN_RECEIVE causes writes on the other end of the connection to return
a closed pipe condition (SIGPIPE signal).
<<
val getsockname : file_descr -> sockaddr
>>
Return the address of the given socket.
<<
val getpeername : file_descr -> sockaddr
>>
Return the address of the host connected to the given socket.
<<
type msg_flag =
| MSG_OOB
| MSG_DONTROUTE
| MSG_PEEK
>>
The flags for Unix.recv[21.1], Unix.recvfrom[21.1], Unix.send[21.1] and
Unix.sendto[21.1].
<<
val recv : file_descr -> string -> int -> int -> msg_flag list -> int
>>
Receive data from a connected socket.
<<
val recvfrom :
file_descr ->
string -> int -> int -> msg_flag list -> int * sockaddr
>>
Receive data from an unconnected socket.
<<
val send : file_descr -> string -> int -> int -> msg_flag list -> int
>>
Send data over a connected socket.
<<
val sendto :
file_descr ->
string -> int -> int -> msg_flag list -> sockaddr -> int
>>
Send data over an unconnected socket.
Socket options
==============
<<
type socket_bool_option =
| SO_DEBUG
>>
Record debugging information
<<
| SO_BROADCAST
>>
Permit sending of broadcast messages
<<
| SO_REUSEADDR
>>
Allow reuse of local addresses for bind
<<
| SO_KEEPALIVE
>>
Keep connection active
<<
| SO_DONTROUTE
>>
Bypass the standard routing algorithms
<<
| SO_OOBINLINE
>>
Leave out-of-band data in line
<<
| SO_ACCEPTCONN
>>
Report whether socket listening is enabled
The socket options that can be consulted with Unix.getsockopt[21.1] and
modified with Unix.setsockopt[21.1]. These options have a boolean
(true/false) value.
<<
type socket_int_option =
| SO_SNDBUF
>>
Size of send buffer
<<
| SO_RCVBUF
>>
Size of received buffer
<<
| SO_ERROR
>>
Report the error status and clear it
<<
| SO_TYPE
>>
Report the socket type
<<
| SO_RCVLOWAT
>>
Minimum number of bytes to process for input operations
<<
| SO_SNDLOWAT
>>
Minimum number of bytes to process for output operations
The socket options that can be consulted with Unix.getsockopt_int[21.1] and
modified with Unix.setsockopt_int[21.1]. These options have an integer
value.
<<
type socket_optint_option =
| SO_LINGER
>>
Whether to linger on closed connections that have data present, and for how
long (in seconds)
The socket options that can be consulted with Unix.getsockopt_optint[21.1]
and modified with Unix.setsockopt_optint[21.1]. These options have a value
of type int option, with None meaning "disabled".
<<
type socket_float_option =
| SO_RCVTIMEO
>>
Timeout for input operations
<<
| SO_SNDTIMEO
>>
Timeout for output operations
The socket options that can be consulted with Unix.getsockopt_float[21.1]
and modified with Unix.setsockopt_float[21.1]. These options have a
floating-point value representing a time in seconds. The value 0 means
infinite timeout.
<<
val getsockopt : file_descr -> socket_bool_option -> bool
>>
Return the current status of a boolean-valued option in the given socket.
<<
val setsockopt : file_descr -> socket_bool_option -> bool -> unit
>>
Set or clear a boolean-valued option in the given socket.
<<
val getsockopt_int : file_descr -> socket_int_option -> int
>>
Same as Unix.getsockopt[21.1] for an integer-valued socket option.
<<
val setsockopt_int : file_descr -> socket_int_option -> int -> unit
>>
Same as Unix.setsockopt[21.1] for an integer-valued socket option.
<<
val getsockopt_optint : file_descr -> socket_optint_option -> int option
>>
Same as Unix.getsockopt[21.1] for a socket option whose value is an int
option.
<<
val setsockopt_optint :
file_descr -> socket_optint_option -> int option -> unit
>>
Same as Unix.setsockopt[21.1] for a socket option whose value is an int
option.
<<
val getsockopt_float : file_descr -> socket_float_option -> float
>>
Same as Unix.getsockopt[21.1] for a socket option whose value is a
floating-point number.
<<
val setsockopt_float : file_descr -> socket_float_option -> float -> unit
>>
Same as Unix.setsockopt[21.1] for a socket option whose value is a
floating-point number.
High-level network connection functions
=======================================
<<
val open_connection :
sockaddr -> Pervasives.in_channel * Pervasives.out_channel
>>
Connect to a server at the given address. Return a pair of buffered
channels connected to the server. Remember to call Pervasives.flush[19.2] on
the output channel at the right times to ensure correct synchronization.
<<
val shutdown_connection : Pervasives.in_channel -> unit
>>
"Shut down" a connection established with Unix.open_connection[21.1]; that
is, transmit an end-of-file condition to the server reading on the other
side of the connection.
<<
val establish_server :
(Pervasives.in_channel -> Pervasives.out_channel -> unit) ->
sockaddr -> unit
>>
Establish a server on the given address. The function given as first
argument is called for each connection with two buffered channels connected
to the client. A new process is created for each connection. The function
Unix.establish_server[21.1] never returns normally.
Host and protocol databases
===========================
<<
type host_entry = {
h_name : string ;
h_aliases : string array ;
h_addrtype : socket_domain ;
h_addr_list : inet_addr array ;
}
>>
Structure of entries in the hosts database.
<<
type protocol_entry = {
p_name : string ;
p_aliases : string array ;
p_proto : int ;
}
>>
Structure of entries in the protocols database.
<<
type service_entry = {
s_name : string ;
s_aliases : string array ;
s_port : int ;
s_proto : string ;
}
>>
Structure of entries in the services database.
<<
val gethostname : unit -> string
>>
Return the name of the local host.
<<
val gethostbyname : string -> host_entry
>>
Find an entry in hosts with the given name, or raise Not_found.
<<
val gethostbyaddr : inet_addr -> host_entry
>>
Find an entry in hosts with the given address, or raise Not_found.
<<
val getprotobyname : string -> protocol_entry
>>
Find an entry in protocols with the given name, or raise Not_found.
<<
val getprotobynumber : int -> protocol_entry
>>
Find an entry in protocols with the given protocol number, or raise
Not_found.
<<
val getservbyname : string -> string -> service_entry
>>
Find an entry in services with the given name, or raise Not_found.
<<
val getservbyport : int -> string -> service_entry
>>
Find an entry in services with the given service number, or raise
Not_found.
<<
type addr_info = {
ai_family : socket_domain ;
>>
Socket domain
<<
ai_socktype : socket_type ;
>>
Socket type
<<
ai_protocol : int ;
>>
Socket protocol number
<<
ai_addr : sockaddr ;
>>
Address
<<
ai_canonname : string ;
>>
Canonical host name
<<
}
>>
Address information returned by Unix.getaddrinfo[21.1].
<<
type getaddrinfo_option =
| AI_FAMILY of socket_domain
>>
Impose the given socket domain
<<
| AI_SOCKTYPE of socket_type
>>
Impose the given socket type
<<
| AI_PROTOCOL of int
>>
Impose the given protocol
<<
| AI_NUMERICHOST
>>
Do not call name resolver, expect numeric IP address
<<
| AI_CANONNAME
>>
Fill the ai_canonname field of the result
<<
| AI_PASSIVE
>>
Set address to "any" address for use with Unix.bind[21.1]
Options to Unix.getaddrinfo[21.1].
<<
val getaddrinfo :
string -> string -> getaddrinfo_option list -> addr_info list
>>
getaddrinfo host service opts returns a list of Unix.addr_info[21.1]
records describing socket parameters and addresses suitable for
communicating with the given host and service. The empty list is returned if
the host or service names are unknown, or the constraints expressed in opts
cannot be satisfied.
host is either a host name or the string representation of an IP address.
host can be given as the empty string; in this case, the "any" address or
the "loopback" address are used, depending whether opts contains AI_PASSIVE.
service is either a service name or the string representation of a port
number. service can be given as the empty string; in this case, the port
field of the returned addresses is set to 0. opts is a possibly empty list
of options that allows the caller to force a particular socket domain (e.g.
IPv6 only or IPv4 only) or a particular socket type (e.g. TCP only or UDP
only).
<<
type name_info = {
ni_hostname : string ;
>>
Name or IP address of host
<<
ni_service : string ;
}
>>
Name of service or port number
Host and service information returned by Unix.getnameinfo[21.1].
<<
type getnameinfo_option =
| NI_NOFQDN
>>
Do not qualify local host names
<<
| NI_NUMERICHOST
>>
Always return host as IP address
<<
| NI_NAMEREQD
>>
Fail if host name cannot be determined
<<
| NI_NUMERICSERV
>>
Always return service as port number
<<
| NI_DGRAM
>>
Consider the service as UDP-based instead of the default TCP
Options to Unix.getnameinfo[21.1].
<<
val getnameinfo : sockaddr -> getnameinfo_option list -> name_info
>>
getnameinfo addr opts returns the host name and service name corresponding
to the socket address addr. opts is a possibly empty list of options that
governs how these names are obtained. Raise Not_found if an error occurs.
Terminal interface
==================
The following functions implement the POSIX standard terminal interface. They
provide control over asynchronous communication ports and pseudo-terminals.
Refer to the termios man page for a complete description.
<<
type terminal_io = {
mutable c_ignbrk : bool ;
>>
Ignore the break condition.
<<
mutable c_brkint : bool ;
>>
Signal interrupt on break condition.
<<
mutable c_ignpar : bool ;
>>
Ignore characters with parity errors.
<<
mutable c_parmrk : bool ;
>>
Mark parity errors.
<<
mutable c_inpck : bool ;
>>
Enable parity check on input.
<<
mutable c_istrip : bool ;
>>
Strip 8th bit on input characters.
<<
mutable c_inlcr : bool ;
>>
Map NL to CR on input.
<<
mutable c_igncr : bool ;
>>
Ignore CR on input.
<<
mutable c_icrnl : bool ;
>>
Map CR to NL on input.
<<
mutable c_ixon : bool ;
>>
Recognize XON/XOFF characters on input.
<<
mutable c_ixoff : bool ;
>>
Emit XON/XOFF chars to control input flow.
<<
mutable c_opost : bool ;
>>
Enable output processing.
<<
mutable c_obaud : int ;
>>
Output baud rate (0 means close connection).
<<
mutable c_ibaud : int ;
>>
Input baud rate.
<<
mutable c_csize : int ;
>>
Number of bits per character (5-8).
<<
mutable c_cstopb : int ;
>>
Number of stop bits (1-2).
<<
mutable c_cread : bool ;
>>
Reception is enabled.
<<
mutable c_parenb : bool ;
>>
Enable parity generation and detection.
<<
mutable c_parodd : bool ;
>>
Specify odd parity instead of even.
<<
mutable c_hupcl : bool ;
>>
Hang up on last close.
<<
mutable c_clocal : bool ;
>>
Ignore modem status lines.
<<
mutable c_isig : bool ;
>>
Generate signal on INTR, QUIT, SUSP.
<<
mutable c_icanon : bool ;
>>
Enable canonical processing (line buffering and editing)
<<
mutable c_noflsh : bool ;
>>
Disable flush after INTR, QUIT, SUSP.
<<
mutable c_echo : bool ;
>>
Echo input characters.
<<
mutable c_echoe : bool ;
>>
Echo ERASE (to erase previous character).
<<
mutable c_echok : bool ;
>>
Echo KILL (to erase the current line).
<<
mutable c_echonl : bool ;
>>
Echo NL even if c_echo is not set.
<<
mutable c_vintr : char ;
>>
Interrupt character (usually ctrl-C).
<<
mutable c_vquit : char ;
>>
Quit character (usually ctrl-\).
<<
mutable c_verase : char ;
>>
Erase character (usually DEL or ctrl-H).
<<
mutable c_vkill : char ;
>>
Kill line character (usually ctrl-U).
<<
mutable c_veof : char ;
>>
End-of-file character (usually ctrl-D).
<<
mutable c_veol : char ;
>>
Alternate end-of-line char. (usually none).
<<
mutable c_vmin : int ;
>>
Minimum number of characters to read before the read request is satisfied.
<<
mutable c_vtime : int ;
>>
Maximum read wait (in 0.1s units).
<<
mutable c_vstart : char ;
>>
Start character (usually ctrl-Q).
<<
mutable c_vstop : char ;
>>
Stop character (usually ctrl-S).
<<
}
>>
<<
val tcgetattr : file_descr -> terminal_io
>>
Return the status of the terminal referred to by the given file descriptor.
<<
type setattr_when =
| TCSANOW
| TCSADRAIN
| TCSAFLUSH
>>
<<
val tcsetattr : file_descr -> setattr_when -> terminal_io -> unit
>>
Set the status of the terminal referred to by the given file descriptor.
The second argument indicates when the status change takes place:
immediately (TCSANOW), when all pending output has been transmitted
(TCSADRAIN), or after flushing all input that has been received but not read
(TCSAFLUSH). TCSADRAIN is recommended when changing the output parameters;
TCSAFLUSH, when changing the input parameters.
<<
val tcsendbreak : file_descr -> int -> unit
>>
Send a break condition on the given file descriptor. The second argument is
the duration of the break, in 0.1s units; 0 means standard duration (0.25s).
<<
val tcdrain : file_descr -> unit
>>
Waits until all output written on the given file descriptor has been
transmitted.
<<
type flush_queue =
| TCIFLUSH
| TCOFLUSH
| TCIOFLUSH
>>
<<
val tcflush : file_descr -> flush_queue -> unit
>>
Discard data written on the given file descriptor but not yet transmitted,
or data received but not yet read, depending on the second argument:
TCIFLUSH flushes data received but not read, TCOFLUSH flushes data written
but not transmitted, and TCIOFLUSH flushes both.
<<
type flow_action =
| TCOOFF
| TCOON
| TCIOFF
| TCION
>>
<<
val tcflow : file_descr -> flow_action -> unit
>>
Suspend or restart reception or transmission of data on the given file
descriptor, depending on the second argument: TCOOFF suspends output, TCOON
restarts output, TCIOFF transmits a STOP character to suspend input, and
TCION transmits a START character to restart input.
<<
val setsid : unit -> int
>>
Put the calling process in a new session and detach it from its controlling
terminal.
21.2 Module UnixLabels: labelized version of the interface
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module is identical to Unix (21.1), and only differs by the addition of
labels. You may see these labels directly by looking at unixLabels.mli, or by
using the ocamlbrowser tool.
Windows:
The Cygwin port of Objective Caml fully implements all functions from the
Unix module. The native Win32 ports implement a subset of them. Below is a
list of the functions that are not implemented, or only partially
implemented, by the Win32 ports. Functions not mentioned are fully
implemented and behave as described previously in this chapter.
------------------------------------------------------
| Functions | Comment |
------------------------------------------------------
| fork |not implemented, use |
| |create_process or |
| |threads |
|wait |not implemented, use |
| |waitpid |
|waitpid |can only wait for a |
| |given PID, not any |
| |child process |
|getppid |not implemented |
| |(meaningless under |
| |Windows) |
|nice |not implemented |
|in_channel_of_descr |does not work on |
| |sockets under Windows |
| |95, 98, ME; works fine |
| |under NT, 2000, XP |
|out_channel_of_descr |ditto |
|truncate, ftruncate |not implemented |
|lstat, fstat |not implemented |
|link, symlink, readlink |not implemented (no |
| |links under Windows) |
|fchmod |not implemented |
|chown, fchown |not implemented (make |
| |no sense on a DOS file |
| |system) |
|umask |not implemented |
|set_nonblock, clear_nonblock|implemented as dummy |
| |functions; use threads |
| |instead of non-blocking|
| |I/O |
|rewinddir |not implemented; |
| |re-open the directory |
| |instead |
|mkfifo |not implemented |
|select |implemented, but works |
| |only for sockets; use |
| |threads if you need to |
| |wait on other kinds of |
| |file descriptors |
|lockf |not implemented |
|kill, pause |not implemented (no |
| |inter-process signals |
| |in Windows) |
|alarm, times |not implemented |
|getitimer, setitimer |not implemented |
|getuid, getgid |always return 1 |
|getgid, getegid, getgroups |not implemented |
|setuid, setgid |not implemented |
|getpwnam, getpwuid |always raise Not_found |
|getgrnam, getgrgid |always raise Not_found |
|type socket_domain |the domain PF_UNIX is |
| |not supported; PF_INET |
| |is fully supported |
|open_connection |does not work under |
| |Windows 95, 98, ME; |
| |works fine under NT, |
| |2000, XP |
|establish_server |not implemented; use |
| |threads |
|terminal functions (tc*) |not implemented |
------------------------------------------------------
Chapter 22 The num library: arbitrary-precision rational arithmetic
**********************************************************************
The num library implements integer arithmetic and rational arithmetic in
arbitrary precision.
More documentation on the functions provided in this library can be found in
The CAML Numbers Reference Manual by Valérie Ménissier-Morain, technical
report 141, INRIA, july 1992 (available electronically,
ftp://ftp.inria.fr/INRIA/publication/RT/RT-0141.ps.gz).
Programs that use the num library must be linked as follows:
<<
ocamlc other options nums.cma other files
ocamlopt other options nums.cmxa other files
>>
For interactive use of the nums library, do:
<<
ocamlmktop -o mytop nums.cma
./mytop
>>
or (if dynamic linking of C libraries is supported on your platform), start
ocaml and type #load "nums.cma";;.
22.1 Module Num : Operation on arbitrary-precision numbers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Numbers (type num) are arbitrary-precision rational numbers, plus the special
elements 1/0 (infinity) and 0/0 (undefined).
<<
type num =
| Int of int
| Big_int of Big_int.big_int
| Ratio of Ratio.ratio
>>
The type of numbers.
Arithmetic operations
=====================
<<
val (+/) : num -> num -> num
>>
Same as Num.add_num[22.1].
<<
val add_num : num -> num -> num
>>
Addition
<<
val minus_num : num -> num
>>
Unary negation.
<<
val (-/) : num -> num -> num
>>
Same as Num.sub_num[22.1].
<<
val sub_num : num -> num -> num
>>
Subtraction
<<
val (*/) : num -> num -> num
>>
Same as Num.mult_num[22.1].
<<
val mult_num : num -> num -> num
>>
Multiplication
<<
val square_num : num -> num
>>
Squaring
<<
val (//) : num -> num -> num
>>
Same as Num.div_num[22.1].
<<
val div_num : num -> num -> num
>>
Division
<<
val quo_num : num -> num -> num
>>
Euclidean division: quotient.
<<
val mod_num : num -> num -> num
>>
Euclidean division: remainder.
<<
val (**/) : num -> num -> num
>>
Same as Num.power_num[22.1].
<<
val power_num : num -> num -> num
>>
Exponentiation
<<
val abs_num : num -> num
>>
Absolute value.
<<
val succ_num : num -> num
>>
succ n is n+1
<<
val pred_num : num -> num
>>
pred n is n-1
<<
val incr_num : num Pervasives.ref -> unit
>>
incr r is r:=!r+1, where r is a reference to a number.
<<
val decr_num : num Pervasives.ref -> unit
>>
decr r is r:=!r-1, where r is a reference to a number.
<<
val is_integer_num : num -> bool
>>
Test if a number is an integer
The four following functions approximate a number by an integer :
<<
val integer_num : num -> num
>>
integer_num n returns the integer closest to n. In case of ties, rounds
towards zero.
<<
val floor_num : num -> num
>>
floor_num n returns the largest integer smaller or equal to n.
<<
val round_num : num -> num
>>
round_num n returns the integer closest to n. In case of ties, rounds off
zero.
<<
val ceiling_num : num -> num
>>
ceiling_num n returns the smallest integer bigger or equal to n.
<<
val sign_num : num -> int
>>
Return -1, 0 or 1 according to the sign of the argument.
Comparisons between numbers
---------------------------
<<
val (=/) : num -> num -> bool
>>
<<
val (</) : num -> num -> bool
>>
<<
val (>/) : num -> num -> bool
>>
<<
val (<=/) : num -> num -> bool
>>
<<
val (>=/) : num -> num -> bool
>>
<<
val (<>/) : num -> num -> bool
>>
<<
val eq_num : num -> num -> bool
>>
<<
val lt_num : num -> num -> bool
>>
<<
val le_num : num -> num -> bool
>>
<<
val gt_num : num -> num -> bool
>>
<<
val ge_num : num -> num -> bool
>>
<<
val compare_num : num -> num -> int
>>
Return -1, 0 or 1 if the first argument is less than, equal to, or greater
than the second argument.
<<
val max_num : num -> num -> num
>>
Return the greater of the two arguments.
<<
val min_num : num -> num -> num
>>
Return the smaller of the two arguments.
Coercions with strings
======================
<<
val string_of_num : num -> string
>>
Convert a number to a string, using fractional notation.
<<
val approx_num_fix : int -> num -> string
>>
See Num.approx_num_exp[22.1].
<<
val approx_num_exp : int -> num -> string
>>
Approximate a number by a decimal. The first argument is the required
precision. The second argument is the number to approximate.
Num.approx_num_fix[22.1] uses decimal notation; the first argument is the
number of digits after the decimal point. approx_num_exp uses scientific
(exponential) notation; the first argument is the number of digits in the
mantissa.
<<
val num_of_string : string -> num
>>
Convert a string to a number.
Coercions between numerical types
=================================
<<
val int_of_num : num -> int
>>
<<
val num_of_int : int -> num
>>
<<
val nat_of_num : num -> Nat.nat
>>
<<
val num_of_nat : Nat.nat -> num
>>
<<
val num_of_big_int : Big_int.big_int -> num
>>
<<
val big_int_of_num : num -> Big_int.big_int
>>
<<
val ratio_of_num : num -> Ratio.ratio
>>
<<
val num_of_ratio : Ratio.ratio -> num
>>
<<
val float_of_num : num -> float
>>
22.2 Module Big_int : Operations on arbitrary-precision integers.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Big integers (type big_int) are signed integers of arbitrary size.
<<
type big_int
>>
The type of big integers.
<<
val zero_big_int : big_int
>>
The big integer 0.
<<
val unit_big_int : big_int
>>
The big integer 1.
Arithmetic operations
=====================
<<
val minus_big_int : big_int -> big_int
>>
Unary negation.
<<
val abs_big_int : big_int -> big_int
>>
Absolute value.
<<
val add_big_int : big_int -> big_int -> big_int
>>
Addition.
<<
val succ_big_int : big_int -> big_int
>>
Successor (add 1).
<<
val add_int_big_int : int -> big_int -> big_int
>>
Addition of a small integer to a big integer.
<<
val sub_big_int : big_int -> big_int -> big_int
>>
Subtraction.
<<
val pred_big_int : big_int -> big_int
>>
Predecessor (subtract 1).
<<
val mult_big_int : big_int -> big_int -> big_int
>>
Multiplication of two big integers.
<<
val mult_int_big_int : int -> big_int -> big_int
>>
Multiplication of a big integer by a small integer
<<
val square_big_int : big_int -> big_int
>>
Return the square of the given big integer
<<
val sqrt_big_int : big_int -> big_int
>>
sqrt_big_int a returns the integer square root of a, that is, the largest
big integer r such that r * r <= a. Raise Invalid_argument if a is negative.
<<
val quomod_big_int : big_int -> big_int -> big_int * big_int
>>
Euclidean division of two big integers. The first part of the result is the
quotient, the second part is the remainder. Writing (q,r) = quomod_big_int a
b, we have a = q * b + r and 0 <= r < |b|. Raise Division_by_zero if the
divisor is zero.
<<
val div_big_int : big_int -> big_int -> big_int
>>
Euclidean quotient of two big integers. This is the first result q of
quomod_big_int (see above).
<<
val mod_big_int : big_int -> big_int -> big_int
>>
Euclidean modulus of two big integers. This is the second result r of
quomod_big_int (see above).
<<
val gcd_big_int : big_int -> big_int -> big_int
>>
Greatest common divisor of two big integers.
<<
val power_int_positive_int : int -> int -> big_int
>>
<<
val power_big_int_positive_int : big_int -> int -> big_int
>>
<<
val power_int_positive_big_int : int -> big_int -> big_int
>>
<<
val power_big_int_positive_big_int : big_int -> big_int -> big_int
>>
Exponentiation functions. Return the big integer representing the first
argument a raised to the power b (the second argument). Depending on the
function, a and b can be either small integers or big integers. Raise
Invalid_argument if b is negative.
Comparisons and tests
=====================
<<
val sign_big_int : big_int -> int
>>
Return 0 if the given big integer is zero, 1 if it is positive, and -1 if
it is negative.
<<
val compare_big_int : big_int -> big_int -> int
>>
compare_big_int a b returns 0 if a and b are equal, 1 if a is greater than
b, and -1 if a is smaller than b.
<<
val eq_big_int : big_int -> big_int -> bool
>>
<<
val le_big_int : big_int -> big_int -> bool
>>
<<
val ge_big_int : big_int -> big_int -> bool
>>
<<
val lt_big_int : big_int -> big_int -> bool
>>
<<
val gt_big_int : big_int -> big_int -> bool
>>
Usual boolean comparisons between two big integers.
<<
val max_big_int : big_int -> big_int -> big_int
>>
Return the greater of its two arguments.
<<
val min_big_int : big_int -> big_int -> big_int
>>
Return the smaller of its two arguments.
<<
val num_digits_big_int : big_int -> int
>>
Return the number of machine words used to store the given big integer.
Conversions to and from strings
===============================
<<
val string_of_big_int : big_int -> string
>>
Return the string representation of the given big integer, in decimal (base
10).
<<
val big_int_of_string : string -> big_int
>>
Convert a string to a big integer, in decimal. The string consists of an
optional - or + sign, followed by one or several decimal digits.
Conversions to and from other numerical types
=============================================
<<
val big_int_of_int : int -> big_int
>>
Convert a small integer to a big integer.
<<
val is_int_big_int : big_int -> bool
>>
Test whether the given big integer is small enough to be representable as a
small integer (type int) without loss of precision. On a 32-bit platform,
is_int_big_int a returns true if and only if a is between 2^30 and 2^30-1.
On a 64-bit platform, is_int_big_int a returns true if and only if a is
between -2^62 and 2^62-1.
<<
val int_of_big_int : big_int -> int
>>
Convert a big integer to a small integer (type int). Raises Failure
"int_of_big_int" if the big integer is not representable as a small integer.
<<
val float_of_big_int : big_int -> float
>>
Returns a floating-point number approximating the given big integer.
22.3 Module Arith_status : Flags that control rational arithmetic.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
<<
val arith_status : unit -> unit
>>
Print the current status of the arithmetic flags.
<<
val get_error_when_null_denominator : unit -> bool
>>
See Arith_status.set_error_when_null_denominator[22.3].
<<
val set_error_when_null_denominator : bool -> unit
>>
Get or set the flag null_denominator. When on, attempting to create a
rational with a null denominator raises an exception. When off, rationals
with null denominators are accepted. Initially: on.
<<
val get_normalize_ratio : unit -> bool
>>
See Arith_status.set_normalize_ratio[22.3].
<<
val set_normalize_ratio : bool -> unit
>>
Get or set the flag normalize_ratio. When on, rational numbers are
normalized after each operation. When off, rational numbers are not
normalized until printed. Initially: off.
<<
val get_normalize_ratio_when_printing : unit -> bool
>>
See Arith_status.set_normalize_ratio_when_printing[22.3].
<<
val set_normalize_ratio_when_printing : bool -> unit
>>
Get or set the flag normalize_ratio_when_printing. When on, rational
numbers are normalized before being printed. When off, rational numbers are
printed as is, without normalization. Initially: on.
<<
val get_approx_printing : unit -> bool
>>
See Arith_status.set_approx_printing[22.3].
<<
val set_approx_printing : bool -> unit
>>
Get or set the flag approx_printing. When on, rational numbers are printed
as a decimal approximation. When off, rational numbers are printed as a
fraction. Initially: off.
<<
val get_floating_precision : unit -> int
>>
See Arith_status.set_floating_precision[22.3].
<<
val set_floating_precision : int -> unit
>>
Get or set the parameter floating_precision. This parameter is the number
of digits displayed when approx_printing is on. Initially: 12.
Chapter 23 The str library: regular expressions and string processing
************************************************************************
The str library provides high-level string processing functions, some based
on regular expressions. It is intended to support the kind of file processing
that is usually performed with scripting languages such as awk, perl or sed.
Programs that use the str library must be linked as follows:
<<
ocamlc other options str.cma other files
ocamlopt other options str.cmxa other files
>>
For interactive use of the str library, do:
<<
ocamlmktop -o mytop str.cma
./mytop
>>
or (if dynamic linking of C libraries is supported on your platform), start
ocaml and type #load "str.cma";;.
23.1 Module Str : Regular expressions and high-level string processing
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
Regular expressions
===================
<<
type regexp
>>
The type of compiled regular expressions.
<<
val regexp : string -> regexp
>>
Compile a regular expression. The following constructs are recognized:
- . Matches any character except newline.
- * (postfix) Matches the preceding expression zero, one or several times
- + (postfix) Matches the preceding expression one or several times
- ? (postfix) Matches the preceding expression once or not at all
- [..] Character set. Ranges are denoted with -, as in [a-z]. An initial
^, as in [^0-9], complements the set. To include a ] character in a set,
make it the first character of the set. To include a - character in a
set, make it the first or the last character of the set.
- ^ Matches at beginning of line (either at the beginning of the matched
string, or just after a newline character).
- $ Matches at end of line (either at the end of the matched string, or
just before a newline character).
- \| (infix) Alternative between two expressions.
- \(..\) Grouping and naming of the enclosed expression.
- \1 The text matched by the first \(...\) expression (\2 for the second
expression, and so on up to \9).
- \b Matches word boundaries.
- \ Quotes special characters. The special characters are $^.*+?[].
<<
val regexp_case_fold : string -> regexp
>>
Same as regexp, but the compiled expression will match text in a
case-insensitive way: uppercase and lowercase letters will be considered
equivalent.
<<
val quote : string -> string
>>
Str.quote s returns a regexp string that matches exactly s and nothing
else.
<<
val regexp_string : string -> regexp
>>
Str.regexp_string s returns a regular expression that matches exactly s and
nothing else.
<<
val regexp_string_case_fold : string -> regexp
>>
Str.regexp_string_case_fold is similar to Str.regexp_string[23.1], but the
regexp matches in a case-insensitive way.
String matching and searching
=============================
<<
val string_match : regexp -> string -> int -> bool
>>
string_match r s start tests whether a substring of s that starts at
position start matches the regular expression r. The first character of a
string has position 0, as usual.
<<
val search_forward : regexp -> string -> int -> int
>>
search_forward r s start searches the string s for a substring matching the
regular expression r. The search starts at position start and proceeds
towards the end of the string. Return the position of the first character of
the matched substring, or raise Not_found if no substring matches.
<<
val search_backward : regexp -> string -> int -> int
>>
search_backward r s last searches the string s for a substring matching the
regular expression r. The search first considers substrings that start at
position last and proceeds towards the beginning of string. Return the
position of the first character of the matched substring; raise Not_found if
no substring matches.
<<
val string_partial_match : regexp -> string -> int -> bool
>>
Similar to Str.string_match[23.1], but also returns true if the argument
string is a prefix of a string that matches. This includes the case of a
true complete match.
<<
val matched_string : string -> string
>>
matched_string s returns the substring of s that was matched by the latest
Str.string_match[23.1], Str.search_forward[23.1] or
Str.search_backward[23.1]. The user must make sure that the parameter s is
the same string that was passed to the matching or searching function.
<<
val match_beginning : unit -> int
>>
match_beginning() returns the position of the first character of the
substring that was matched by Str.string_match[23.1],
Str.search_forward[23.1] or Str.search_backward[23.1].
<<
val match_end : unit -> int
>>
match_end() returns the position of the character following the last
character of the substring that was matched by string_match, search_forward
or search_backward.
<<
val matched_group : int -> string -> string
>>
matched_group n s returns the substring of s that was matched by the nth
group \(...\) of the regular expression during the latest
Str.string_match[23.1], Str.search_forward[23.1] or
Str.search_backward[23.1]. The user must make sure that the parameter s is
the same string that was passed to the matching or searching function.
matched_group n s raises Not_found if the nth group of the regular
expression was not matched. This can happen with groups inside alternatives
\|, options ? or repetitions *. For instance, the empty string will match
\(a\)*, but matched_group 1 "" will raise Not_found because the first group
itself was not matched.
<<
val group_beginning : int -> int
>>
group_beginning n returns the position of the first character of the
substring that was matched by the nth group of the regular expression.
Raises
- Not_found if the nth group of the regular expression was not matched.
- Invalid_argument if there are fewer than n groups in the regular
expression.
<<
val group_end : int -> int
>>
group_end n returns the position of the character following the last
character of substring that was matched by the nth group of the regular
expression.
Raises
- Not_found if the nth group of the regular expression was not matched.
- Invalid_argument if there are fewer than n groups in the regular
expression.
Replacement
===========
<<
val global_replace : regexp -> string -> string -> string
>>
global_replace regexp templ s returns a string identical to s, except that
all substrings of s that match regexp have been replaced by templ. The
replacement template templ can contain \1, \2, etc; these sequences will be
replaced by the text matched by the corresponding group in the regular
expression. \0 stands for the text matched by the whole regular expression.
<<
val replace_first : regexp -> string -> string -> string
>>
Same as Str.global_replace[23.1], except that only the first substring
matching the regular expression is replaced.
<<
val global_substitute : regexp -> (string -> string) -> string -> string
>>
global_substitute regexp subst s returns a string identical to s, except
that all substrings of s that match regexp have been replaced by the result
of function subst. The function subst is called once for each matching
substring, and receives s (the whole text) as argument.
<<
val substitute_first : regexp -> (string -> string) -> string -> string
>>
Same as Str.global_substitute[23.1], except that only the first substring
matching the regular expression is replaced.
<<
val replace_matched : string -> string -> string
>>
replace_matched repl s returns the replacement text repl in which \1, \2,
etc. have been replaced by the text matched by the corresponding groups in
the most recent matching operation. s must be the same string that was
matched during this matching operation.
Splitting
=========
<<
val split : regexp -> string -> string list
>>
split r s splits s into substrings, taking as delimiters the substrings
that match r, and returns the list of substrings. For instance, split
(regexp "[ \t]+") s splits s into blank-separated words. An occurrence of
the delimiter at the beginning and at the end of the string is ignored.
<<
val bounded_split : regexp -> string -> int -> string list
>>
Same as Str.split[23.1], but splits into at most n substrings, where n is
the extra integer parameter.
<<
val split_delim : regexp -> string -> string list
>>
Same as Str.split[23.1] but occurrences of the delimiter at the beginning
and at the end of the string are recognized and returned as empty strings in
the result. For instance, split_delim (regexp " ") " abc " returns ["";
"abc"; ""], while split with the same arguments returns ["abc"].
<<
val bounded_split_delim : regexp -> string -> int -> string list
>>
Same as Str.bounded_split[23.1], but occurrences of the delimiter at the
beginning and at the end of the string are recognized and returned as empty
strings in the result.
<<
type split_result =
| Text of string
| Delim of string
>>
<<
val full_split : regexp -> string -> split_result list
>>
Same as Str.split_delim[23.1], but returns the delimiters as well as the
substrings contained between delimiters. The former are tagged Delim in the
result list; the latter are tagged Text. For instance, full_split (regexp
"[{}]") "{ab}" returns [Delim "{"; Text "ab"; Delim "}"].
<<
val bounded_full_split : regexp -> string -> int -> split_result list
>>
Same as Str.bounded_split_delim[23.1], but returns the delimiters as well
as the substrings contained between delimiters. The former are tagged Delim
in the result list; the latter are tagged Text.
Extracting substrings
=====================
<<
val string_before : string -> int -> string
>>
string_before s n returns the substring of all characters of s that precede
position n (excluding the character at position n).
<<
val string_after : string -> int -> string
>>
string_after s n returns the substring of all characters of s that follow
position n (including the character at position n).
<<
val first_chars : string -> int -> string
>>
first_chars s n returns the first n characters of s. This is the same
function as Str.string_before[23.1].
<<
val last_chars : string -> int -> string
>>
last_chars s n returns the last n characters of s.
Chapter 24 The threads library
*********************************
The threads library allows concurrent programming in Objective Caml. It
provides multiple threads of control (also called lightweight processes) that
execute concurrently in the same memory space. Threads communicate by in-place
modification of shared data structures, or by sending and receiving data on
communication channels.
The threads library is implemented by time-sharing on a single processor. It
will not take advantage of multi-processor machines. Using this library will
therefore never make programs run faster. However, many programs are easier to
write when structured as several communicating processes.
Two implementations of the threads library are available, depending on the
capabilities of the operating system:
- System threads. This implementation builds on the OS-provided threads
facilities: POSIX 1003.1c threads for Unix, and Win32 threads for Windows.
When available, system threads support both bytecode and native-code
programs.
- VM-level threads. This implementation performs time-sharing and context
switching at the level of the OCaml virtual machine (bytecode interpreter).
It is available on Unix systems, and supports only bytecode programs. It
cannot be used with native-code programs.
Programs that use system threads must be linked as follows:
<<
ocamlc -thread other options unix.cma threads.cma other files
ocamlopt -thread other options unix.cmxa threads.cmxa other files
>>
Compilation units that use the threads library must also be compiled with
the -thread option (see chapter 8).
Programs that use VM-level threads must be compiled with the -vmthread option
to ocamlc (see chapter 8), and be linked as follows:
<<
ocamlc -vmthread other options threads.cma other files
>>
Compilation units that use threads library must also be compiled with the
-vmthread option (see chapter 8).
24.1 Module Thread : Lightweight threads for Posix 1003.1c and Win32.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
type t
>>
The type of thread handles.
Thread creation and termination
===============================
<<
val create : ('a -> 'b) -> 'a -> t
>>
Thread.create funct arg creates a new thread of control, in which the
function application funct arg is executed concurrently with the other
threads of the program. The application of Thread.create returns the handle
of the newly created thread. The new thread terminates when the application
funct arg returns, either normally or by raising an uncaught exception. In
the latter case, the exception is printed on standard error, but not
propagated back to the parent thread. Similarly, the result of the
application funct arg is discarded and not directly accessible to the parent
thread.
<<
val self : unit -> t
>>
Return the thread currently executing.
<<
val id : t -> int
>>
Return the identifier of the given thread. A thread identifier is an
integer that identifies uniquely the thread. It can be used to build data
structures indexed by threads.
<<
val exit : unit -> unit
>>
Terminate prematurely the currently executing thread.
<<
val kill : t -> unit
>>
Terminate prematurely the thread whose handle is given.
Suspending threads
==================
<<
val delay : float -> unit
>>
delay d suspends the execution of the calling thread for d seconds. The
other program threads continue to run during this time.
<<
val join : t -> unit
>>
join th suspends the execution of the calling thread until the thread th
has terminated.
<<
val wait_read : Unix.file_descr -> unit
>>
See Thread.wait_write[24.1].
<<
val wait_write : Unix.file_descr -> unit
>>
This function does nothing in this implementation.
<<
val wait_timed_read : Unix.file_descr -> float -> bool
>>
See Thread.wait_timed_read[24.1].
<<
val wait_timed_write : Unix.file_descr -> float -> bool
>>
Suspend the execution of the calling thread until at least one character is
available for reading (wait_read) or one character can be written without
blocking (wait_write) on the given Unix file descriptor. Wait for at most
the amount of time given as second argument (in seconds). Return true if the
file descriptor is ready for input/output and false if the timeout expired.
These functions return immediately true in the Win32 implementation.
<<
val select :
Unix.file_descr list ->
Unix.file_descr list ->
Unix.file_descr list ->
float -> Unix.file_descr list * Unix.file_descr list * Unix.file_descr list
>>
Suspend the execution of the calling thead until input/output becomes
possible on the given Unix file descriptors. The arguments and results have
the same meaning as for Unix.select. This function is not implemented yet
under Win32.
<<
val wait_pid : int -> int * Unix.process_status
>>
wait_pid p suspends the execution of the calling thread until the process
specified by the process identifier p terminates. Returns the pid of the
child caught and its termination status, as per Unix.wait. This function is
not implemented under MacOS.
<<
val yield : unit -> unit
>>
Re-schedule the calling thread without suspending it. This function can be
used to give scheduling hints, telling the scheduler that now is a good time
to switch to other threads.
Management of signals
=====================
Signal handling follows the POSIX thread model: signals generated by a thread
are delivered to that thread; signals generated externally are delivered to one
of the threads that does not block it. Each thread possesses a set of blocked
signals, which can be modified using Thread.sigmask[24.1]. This set is
inherited at thread creation time. Per-thread signal masks are supported only
by the system thread library under Unix, but not under Win32, nor by the VM
thread library.
<<
val sigmask : Unix.sigprocmask_command -> int list -> int list
>>
sigmask cmd sigs changes the set of blocked signals for the calling thread.
If cmd is SIG_SETMASK, blocked signals are set to those in the list sigs. If
cmd is SIG_BLOCK, the signals in sigs are added to the set of blocked
signals. If cmd is SIG_UNBLOCK, the signals in sigs are removed from the set
of blocked signals. sigmask returns the set of previously blocked signals
for the thread.
<<
val wait_signal : int list -> int
>>
wait_signal sigs suspends the execution of the calling thread until the
process receives one of the signals specified in the list sigs. It then
returns the number of the signal received. Signal handlers attached to the
signals in sigs will not be invoked. The signals sigs are expected to be
blocked before calling wait_signal.
24.2 Module Mutex : Locks for mutual exclusion.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Mutexes (mutual-exclusion locks) are used to implement critical sections and
protect shared mutable data structures against concurrent accesses. The typical
use is (if m is the mutex associated with the data structure D):
<<
Mutex.lock m;
(* Critical section that operates over D *);
Mutex.unlock m
>>
<<
type t
>>
The type of mutexes.
<<
val create : unit -> t
>>
Return a new mutex.
<<
val lock : t -> unit
>>
Lock the given mutex. Only one thread can have the mutex locked at any
time. A thread that attempts to lock a mutex already locked by another
thread will suspend until the other thread unlocks the mutex.
<<
val try_lock : t -> bool
>>
Same as Mutex.lock[24.2], but does not suspend the calling thread if the
mutex is already locked: just return false immediately in that case. If the
mutex is unlocked, lock it and return true.
<<
val unlock : t -> unit
>>
Unlock the given mutex. Other threads suspended trying to lock the mutex
will restart.
24.3 Module Condition : Condition variables to synchronize between threads.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Condition variables are used when one thread wants to wait until another
thread has finished doing something: the former thread "waits" on the condition
variable, the latter thread "signals" the condition when it is done. Condition
variables should always be protected by a mutex. The typical use is (if D is a
shared data structure, m its mutex, and c is a condition variable):
<<
Mutex.lock m;
while (* some predicate P over D is not satisfied *) do
Condition.wait c m
done;
(* Modify D *)
if (* the predicate P over D is now satified *) then Condition.signal c;
Mutex.unlock m
>>
<<
type t
>>
The type of condition variables.
<<
val create : unit -> t
>>
Return a new condition variable.
<<
val wait : t -> Mutex.t -> unit
>>
wait c m atomically unlocks the mutex m and suspends the calling process on
the condition variable c. The process will restart after the condition
variable c has been signalled. The mutex m is locked again before wait
returns.
<<
val signal : t -> unit
>>
signal c restarts one of the processes waiting on the condition variable
c.
<<
val broadcast : t -> unit
>>
broadcast c restarts all processes waiting on the condition variable c.
24.4 Module Event : First-class synchronous communication.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements synchronous inter-thread communications over channels.
As in John Reppy's Concurrent ML system, the communication events are
first-class values: they can be built and combined independently before being
offered for communication.
<<
type 'a channel
>>
The type of communication channels carrying values of type 'a.
<<
val new_channel : unit -> 'a channel
>>
Return a new channel.
<<
type +'a event
>>
The type of communication events returning a result of type 'a.
<<
val send : 'a channel -> 'a -> unit event
>>
send ch v returns the event consisting in sending the value v over the
channel ch. The result value of this event is ().
<<
val receive : 'a channel -> 'a event
>>
receive ch returns the event consisting in receiving a value from the
channel ch. The result value of this event is the value received.
<<
val always : 'a -> 'a event
>>
always v returns an event that is always ready for synchronization. The
result value of this event is v.
<<
val choose : 'a event list -> 'a event
>>
choose evl returns the event that is the alternative of all the events in
the list evl.
<<
val wrap : 'a event -> ('a -> 'b) -> 'b event
>>
wrap ev fn returns the event that performs the same communications as ev,
then applies the post-processing function fn on the return value.
<<
val wrap_abort : 'a event -> (unit -> unit) -> 'a event
>>
wrap_abort ev fn returns the event that performs the same communications as
ev, but if it is not selected the function fn is called after the
synchronization.
<<
val guard : (unit -> 'a event) -> 'a event
>>
guard fn returns the event that, when synchronized, computes fn() and
behaves as the resulting event. This allows to compute events with
side-effects at the time of the synchronization operation.
<<
val sync : 'a event -> 'a
>>
"Synchronize" on an event: offer all the communication possibilities
specified in the event to the outside world, and block until one of the
communications succeed. The result value of that communication is returned.
<<
val select : 'a event list -> 'a
>>
"Synchronize" on an alternative of events. select evl is shorthand for
sync(choose evl).
<<
val poll : 'a event -> 'a option
>>
Non-blocking version of Event.sync[24.4]: offer all the communication
possibilities specified in the event to the outside world, and if one can
take place immediately, perform it and return Some r where r is the result
value of that communication. Otherwise, return None without blocking.
24.5 Module ThreadUnix : Thread-compatible system calls.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
The functionality of this module has been merged back into the Unix[21.1]
module. Threaded programs can now call the functions from module Unix[21.1]
directly, and still get the correct behavior (block the calling thread, if
required, but do not block all threads in the process).Thread-compatible system
calls.
Process handling
================
<<
val execv : string -> string array -> unit
>>
<<
val execve : string -> string array -> string array -> unit
>>
<<
val execvp : string -> string array -> unit
>>
<<
val wait : unit -> int * Unix.process_status
>>
<<
val waitpid : Unix.wait_flag list -> int -> int * Unix.process_status
>>
<<
val system : string -> Unix.process_status
>>
Basic input/output
==================
<<
val read : Unix.file_descr -> string -> int -> int -> int
>>
<<
val write : Unix.file_descr -> string -> int -> int -> int
>>
Input/output with timeout
=========================
<<
val timed_read : Unix.file_descr -> string -> int -> int -> float -> int
>>
See ThreadUnix.timed_write[24.5].
<<
val timed_write : Unix.file_descr -> string -> int -> int -> float -> int
>>
Behave as ThreadUnix.read[24.5] and ThreadUnix.write[24.5], except that
Unix_error(ETIMEDOUT,_,_) is raised if no data is available for reading or
ready for writing after d seconds. The delay d is given in the fifth
argument, in seconds.
Polling
=======
<<
val select :
Unix.file_descr list ->
Unix.file_descr list ->
Unix.file_descr list ->
float -> Unix.file_descr list * Unix.file_descr list * Unix.file_descr list
>>
Pipes and redirections
======================
<<
val pipe : unit -> Unix.file_descr * Unix.file_descr
>>
<<
val open_process_in : string -> Pervasives.in_channel
>>
<<
val open_process_out : string -> Pervasives.out_channel
>>
<<
val open_process : string -> Pervasives.in_channel * Pervasives.out_channel
>>
Time
====
<<
val sleep : int -> unit
>>
Sockets
=======
<<
val socket : Unix.socket_domain -> Unix.socket_type -> int -> Unix.file_descr
>>
<<
val accept : Unix.file_descr -> Unix.file_descr * Unix.sockaddr
>>
<<
val connect : Unix.file_descr -> Unix.sockaddr -> unit
>>
<<
val recv :
Unix.file_descr -> string -> int -> int -> Unix.msg_flag list -> int
>>
<<
val recvfrom :
Unix.file_descr ->
string -> int -> int -> Unix.msg_flag list -> int * Unix.sockaddr
>>
<<
val send :
Unix.file_descr -> string -> int -> int -> Unix.msg_flag list -> int
>>
<<
val sendto :
Unix.file_descr ->
string -> int -> int -> Unix.msg_flag list -> Unix.sockaddr -> int
>>
<<
val open_connection :
Unix.sockaddr -> Pervasives.in_channel * Pervasives.out_channel
>>
Chapter 25 The graphics library
**********************************
The graphics library provides a set of portable drawing primitives. Drawing
takes place in a separate window that is created when Graphics.open_graph is
called.
Unix:
This library is implemented under the X11 windows system. Programs that
use the graphics library must be linked as follows:
<<
ocamlc other options graphics.cma other files
>>
For interactive use of the graphics library, do:
<<
ocamlmktop -o mytop graphics.cma
./mytop
>>
or (if dynamic linking of C libraries is supported on your platform), start
ocaml and type #load "graphics.cma";;.
Here are the graphics mode specifications supported by Graphics.open_graph
on the X11 implementation of this library: the argument to
Graphics.open_graph has the format "display-name geometry", where
display-name is the name of the X-windows display to connect to, and
geometry is a standard X-windows geometry specification. The two components
are separated by a space. Either can be omitted, or both. Examples:
Graphics.open_graph "foo:0" connects to the display foo:0 and creates a
window with the default geometry
Graphics.open_graph "foo:0 300x100+50-0" connects to the display foo:0 and
creates a window 300 pixels wide by 100 pixels tall, at location (50,0)
Graphics.open_graph " 300x100+50-0" connects to the default display and
creates a window 300 pixels wide by 100 pixels tall, at location (50,0)
Graphics.open_graph "" connects to the default display and creates a
window with the default geometry.
Windows:
This library is available both for standalone compiled programs and under
the toplevel application ocamlwin.exe. For the latter, this library must be
loaded in-core by typing
<< #load "graphics.cma";;
>>
The screen coordinates are interpreted as shown in the figure below. Notice
that the coordinate system used is the same as in mathematics: y increases from
the bottom of the screen to the top of the screen, and angles are measured
counterclockwise (in degrees). Drawing is clipped to the screen.
*libgraph.gif*
25.1 Module Graphics : Machine-independent graphics primitives.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
exception Graphic_failure of string
>>
Raised by the functions below when they encounter an error.
Initializations
===============
<<
val open_graph : string -> unit
>>
Show the graphics window or switch the screen to graphic mode. The graphics
window is cleared and the current point is set to (0, 0). The string
argument is used to pass optional information on the desired graphics mode,
the graphics window size, and so on. Its interpretation is
implementation-dependent. If the empty string is given, a sensible default
is selected.
<<
val close_graph : unit -> unit
>>
Delete the graphics window or switch the screen back to text mode.
<<
val set_window_title : string -> unit
>>
Set the title of the graphics window.
<<
val resize_window : int -> int -> unit
>>
Resize and erase the graphics window.
<<
val clear_graph : unit -> unit
>>
Erase the graphics window.
<<
val size_x : unit -> int
>>
See Graphics.size_y[25.1].
<<
val size_y : unit -> int
>>
Return the size of the graphics window. Coordinates of the screen pixels
range over 0 .. size_x()-1 and 0 .. size_y()-1. Drawings outside of this
rectangle are clipped, without causing an error. The origin (0,0) is at the
lower left corner.
Colors
======
<<
type color = int
>>
A color is specified by its R, G, B components. Each component is in the
range 0..255. The three components are packed in an int: 0xRRGGBB, where RR
are the two hexadecimal digits for the red component, GG for the green
component, BB for the blue component.
<<
val rgb : int -> int -> int -> color
>>
rgb r g b returns the integer encoding the color with red component r,
green component g, and blue component b. r, g and b are in the range 0..255.
<<
val set_color : color -> unit
>>
Set the current drawing color.
<<
val background : color
>>
See Graphics.foreground[25.1].
<<
val foreground : color
>>
Default background and foreground colors (usually, either black foreground
on a white background or white foreground on a black background).
Graphics.clear_graph[25.1] fills the screen with the background color. The
initial drawing color is foreground.
Some predefined colors
----------------------
<<
val black : color
>>
<<
val white : color
>>
<<
val red : color
>>
<<
val green : color
>>
<<
val blue : color
>>
<<
val yellow : color
>>
<<
val cyan : color
>>
<<
val magenta : color
>>
Point and line drawing
======================
<<
val plot : int -> int -> unit
>>
Plot the given point with the current drawing color.
<<
val plots : (int * int) array -> unit
>>
Plot the given points with the current drawing color.
<<
val point_color : int -> int -> color
>>
Return the color of the given point in the backing store (see "Double
buffering" below).
<<
val moveto : int -> int -> unit
>>
Position the current point.
<<
val rmoveto : int -> int -> unit
>>
rmoveto dx dy translates the current point by the given vector.
<<
val current_x : unit -> int
>>
Return the abscissa of the current point.
<<
val current_y : unit -> int
>>
Return the ordinate of the current point.
<<
val current_point : unit -> int * int
>>
Return the position of the current point.
<<
val lineto : int -> int -> unit
>>
Draw a line with endpoints the current point and the given point, and move
the current point to the given point.
<<
val rlineto : int -> int -> unit
>>
Draw a line with endpoints the current point and the current point
translated of the given vector, and move the current point to this point.
<<
val curveto : int * int -> int * int -> int * int -> unit
>>
curveto b c d draws a cubic Bezier curve starting from the current point to
point d, with control points b and c, and moves the current point to d.
<<
val draw_rect : int -> int -> int -> int -> unit
>>
draw_rect x y w h draws the rectangle with lower left corner at x,y, width
w and height h. The current point is unchanged. Raise Invalid_argument if w
or h is negative.
<<
val draw_poly_line : (int * int) array -> unit
>>
draw_poly_line points draws the line that joins the points given by the
array argument. The array contains the coordinates of the vertices of the
polygonal line, which need not be closed. The current point is unchanged.
<<
val draw_poly : (int * int) array -> unit
>>
draw_poly polygon draws the given polygon. The array contains the
coordinates of the vertices of the polygon. The current point is unchanged.
<<
val draw_segments : (int * int * int * int) array -> unit
>>
draw_segments segments draws the segments given in the array argument. Each
segment is specified as a quadruple (x0, y0, x1, y1) where (x0, y0) and (x1,
y1) are the coordinates of the end points of the segment. The current point
is unchanged.
<<
val draw_arc : int -> int -> int -> int -> int -> int -> unit
>>
draw_arc x y rx ry a1 a2 draws an elliptical arc with center x,y,
horizontal radius rx, vertical radius ry, from angle a1 to angle a2 (in
degrees). The current point is unchanged. Raise Invalid_argument if rx or ry
is negative.
<<
val draw_ellipse : int -> int -> int -> int -> unit
>>
draw_ellipse x y rx ry draws an ellipse with center x,y, horizontal radius
rx and vertical radius ry. The current point is unchanged. Raise
Invalid_argument if rx or ry is negative.
<<
val draw_circle : int -> int -> int -> unit
>>
draw_circle x y r draws a circle with center x,y and radius r. The current
point is unchanged. Raise Invalid_argument if r is negative.
<<
val set_line_width : int -> unit
>>
Set the width of points and lines drawn with the functions above. Under X
Windows, set_line_width 0 selects a width of 1 pixel and a faster, but less
precise drawing algorithm than the one used when set_line_width 1 is
specified. Raise Invalid_argument if the argument is negative.
Text drawing
============
<<
val draw_char : char -> unit
>>
See Graphics.draw_string[25.1].
<<
val draw_string : string -> unit
>>
Draw a character or a character string with lower left corner at current
position. After drawing, the current position is set to the lower right
corner of the text drawn.
<<
val set_font : string -> unit
>>
Set the font used for drawing text. The interpretation of the argument to
set_font is implementation-dependent.
<<
val set_text_size : int -> unit
>>
Set the character size used for drawing text. The interpretation of the
argument to set_text_size is implementation-dependent.
<<
val text_size : string -> int * int
>>
Return the dimensions of the given text, if it were drawn with the current
font and size.
Filling
=======
<<
val fill_rect : int -> int -> int -> int -> unit
>>
fill_rect x y w h fills the rectangle with lower left corner at x,y, width
w and height h, with the current color. Raise Invalid_argument if w or h is
negative.
<<
val fill_poly : (int * int) array -> unit
>>
Fill the given polygon with the current color. The array contains the
coordinates of the vertices of the polygon.
<<
val fill_arc : int -> int -> int -> int -> int -> int -> unit
>>
Fill an elliptical pie slice with the current color. The parameters are the
same as for Graphics.draw_arc[25.1].
<<
val fill_ellipse : int -> int -> int -> int -> unit
>>
Fill an ellipse with the current color. The parameters are the same as for
Graphics.draw_ellipse[25.1].
<<
val fill_circle : int -> int -> int -> unit
>>
Fill a circle with the current color. The parameters are the same as for
Graphics.draw_circle[25.1].
Images
======
<<
type image
>>
The abstract type for images, in internal representation. Externally,
images are represented as matrices of colors.
<<
val transp : color
>>
In matrices of colors, this color represent a "transparent" point: when
drawing the corresponding image, all pixels on the screen corresponding to a
transparent pixel in the image will not be modified, while other points will
be set to the color of the corresponding point in the image. This allows
superimposing an image over an existing background.
<<
val make_image : color array array -> image
>>
Convert the given color matrix to an image. Each sub-array represents one
horizontal line. All sub-arrays must have the same length; otherwise,
exception Graphic_failure is raised.
<<
val dump_image : image -> color array array
>>
Convert an image to a color matrix.
<<
val draw_image : image -> int -> int -> unit
>>
Draw the given image with lower left corner at the given point.
<<
val get_image : int -> int -> int -> int -> image
>>
Capture the contents of a rectangle on the screen as an image. The
parameters are the same as for Graphics.fill_rect[25.1].
<<
val create_image : int -> int -> image
>>
create_image w h returns a new image w pixels wide and h pixels tall, to be
used in conjunction with blit_image. The initial image contents are random,
except that no point is transparent.
<<
val blit_image : image -> int -> int -> unit
>>
blit_image img x y copies screen pixels into the image img, modifying img
in-place. The pixels copied are those inside the rectangle with lower left
corner at x,y, and width and height equal to those of the image. Pixels that
were transparent in img are left unchanged.
Mouse and keyboard events
=========================
<<
type status = {
mouse_x : int ;
>>
X coordinate of the mouse
<<
mouse_y : int ;
>>
Y coordinate of the mouse
<<
button : bool ;
>>
true if a mouse button is pressed
<<
keypressed : bool ;
>>
true if a key has been pressed
<<
key : char ;
>>
the character for the key pressed
<<
}
>>
To report events.
<<
type event =
| Button_down
>>
A mouse button is pressed
<<
| Button_up
>>
A mouse button is released
<<
| Key_pressed
>>
A key is pressed
<<
| Mouse_motion
>>
The mouse is moved
<<
| Poll
>>
Don't wait; return immediately
To specify events to wait for.
<<
val wait_next_event : event list -> status
>>
Wait until one of the events specified in the given event list occurs, and
return the status of the mouse and keyboard at that time. If Poll is given
in the event list, return immediately with the current status. If the mouse
cursor is outside of the graphics window, the mouse_x and mouse_y fields of
the event are outside the range 0..size_x()-1, 0..size_y()-1. Keypresses are
queued, and dequeued one by one when the Key_pressed event is specified.
Mouse and keyboard polling
==========================
<<
val mouse_pos : unit -> int * int
>>
Return the position of the mouse cursor, relative to the graphics window.
If the mouse cursor is outside of the graphics window, mouse_pos() returns a
point outside of the range 0..size_x()-1, 0..size_y()-1.
<<
val button_down : unit -> bool
>>
Return true if the mouse button is pressed, false otherwise.
<<
val read_key : unit -> char
>>
Wait for a key to be pressed, and return the corresponding character.
Keypresses are queued.
<<
val key_pressed : unit -> bool
>>
Return true if a keypress is available; that is, if read_key would not
block.
Sound
=====
<<
val sound : int -> int -> unit
>>
sound freq dur plays a sound at frequency freq (in hertz) for a duration
dur (in milliseconds).
Double buffering
================
<<
val auto_synchronize : bool -> unit
>>
By default, drawing takes place both on the window displayed on screen, and
in a memory area (the "backing store"). The backing store image is used to
re-paint the on-screen window when necessary.
To avoid flicker during animations, it is possible to turn off on-screen
drawing, perform a number of drawing operations in the backing store only,
then refresh the on-screen window explicitly.
auto_synchronize false turns on-screen drawing off. All subsequent drawing
commands are performed on the backing store only.
auto_synchronize true refreshes the on-screen window from the backing store
(as per synchronize), then turns on-screen drawing back on. All subsequent
drawing commands are performed both on screen and in the backing store.
The default drawing mode corresponds to auto_synchronize true.
<<
val synchronize : unit -> unit
>>
Synchronize the backing store and the on-screen window, by copying the
contents of the backing store onto the graphics window.
<<
val display_mode : bool -> unit
>>
Set display mode on or off. When turned on, drawings are done in the
graphics window; when turned off, drawings do not affect the graphics
window. This occurs independently of drawing into the backing store (see the
function Graphics.remember_mode[25.1] below). Default display mode is on.
<<
val remember_mode : bool -> unit
>>
Set remember mode on or off. When turned on, drawings are done in the
backing store; when turned off, the backing store is unaffected by drawings.
This occurs independently of drawing onto the graphics window (see the
function Graphics.display_mode[25.1] above). Default remember mode is on.
Chapter 26 The dbm library: access to NDBM databases
*******************************************************
The dbm library provides access to NDBM databases under Unix. NDBM databases
maintain key/data associations, where both the key and the data are arbitrary
strings. They support fairly large databases (several gigabytes) and can
retrieve a keyed item in one or two file system accesses. Refer to the Unix
manual pages for more information.
Unix:
Programs that use the dbm library must be linked as follows:
<<
ocamlc other options dbm.cma other files
ocamlopt other options dbm.cmxa other files
>>
For interactive use of the dbm library, do:
<<
ocamlmktop -o mytop dbm.cma
./mytop
>>
or (if dynamic linking of C libraries is supported on your platform), start
ocaml and type #load "dbm.cma";;.
Windows:
This library is not available.
26.1 Module Dbm : Interface to the NDBM database.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
<<
type t
>>
The type of file descriptors opened on NDBM databases.
<<
type open_flag =
| Dbm_rdonly
| Dbm_wronly
| Dbm_rdwr
| Dbm_create
>>
Flags for opening a database (see Dbm.opendbm[26.1]).
<<
exception Dbm_error of string
>>
Raised by the following functions when an error is encountered.
<<
val opendbm : string -> open_flag list -> int -> t
>>
Open a descriptor on an NDBM database. The first argument is the name of
the database (without the .dir and .pag suffixes). The second argument is a
list of flags: Dbm_rdonly opens the database for reading only, Dbm_wronly
for writing only, Dbm_rdwr for reading and writing; Dbm_create causes the
database to be created if it does not already exist. The third argument is
the permissions to give to the database files, if the database is created.
<<
val close : t -> unit
>>
Close the given descriptor.
<<
val find : t -> string -> string
>>
find db key returns the data associated with the given key in the database
opened for the descriptor db. Raise Not_found if the key has no associated
data.
<<
val add : t -> string -> string -> unit
>>
add db key data inserts the pair (key, data) in the database db. If the
database already contains data associated with key, raise Dbm_error "Entry
already exists".
<<
val replace : t -> string -> string -> unit
>>
replace db key data inserts the pair (key, data) in the database db. If the
database already contains data associated with key, that data is discarded
and silently replaced by the new data.
<<
val remove : t -> string -> unit
>>
remove db key data removes the data associated with key in db. If key has
no associated data, raise Dbm_error "dbm_delete".
<<
val firstkey : t -> string
>>
See Dbm.nextkey[26.1].
<<
val nextkey : t -> string
>>
Enumerate all keys in the given database, in an unspecified order. firstkey
db returns the first key, and repeated calls to nextkey db return the
remaining keys. Not_found is raised when all keys have been enumerated.
<<
val iter : (string -> string -> 'a) -> t -> unit
>>
iter f db applies f to each (key, data) pair in the database db. f receives
key as first argument and data as second argument.
Chapter 27 The dynlink library: dynamic loading and linking of object files
******************************************************************************
The dynlink library supports type-safe dynamic loading and linking of
bytecode object files (.cmo and .cma files) in a running bytecode program. Type
safety is ensured by limiting the set of modules from the running program that
the loaded object file can access, and checking that the running program and
the loaded object file have been compiled against the same interfaces for these
modules.
Programs that use the dynlink library simply need to link dynlink.cma with
their object files and other libraries. Dynamic linking is available only to
bytecode programs compiled with ocamlc, not to native-code programs compiled
with ocamlopt.
27.1 Module Dynlink : Dynamic loading of bytecode object files.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Initialization
==============
<<
val init : unit -> unit
>>
Initialize the Dynlink library. Must be called before any other function in
this module.
Dynamic loading of compiled bytecode files
==========================================
<<
val loadfile : string -> unit
>>
Load the given bytecode object file (.cmo file) or bytecode library file
(.cma file), and link it with the running program. All toplevel expressions
in the loaded compilation units are evaluated. No facilities are provided to
access value names defined by the unit. Therefore, the unit must register
itself its entry points with the main program, e.g. by modifying tables of
functions.
<<
val loadfile_private : string -> unit
>>
Same as loadfile, except that the compilation units just loaded are hidden
(cannot be referenced) from other modules dynamically loaded afterwards.
Access control
==============
<<
val allow_only : string list -> unit
>>
allow_only units restricts the compilation units that dynamically-linked
units can reference: it only allows references to the units named in list
units. References to any other compilation unit will cause a
Unavailable_unit error during loadfile or loadfile_private.
Initially (just after calling init), all compilation units composing the
program currently running are available for reference from
dynamically-linked units. allow_only can be used to grant access to some of
them only, e.g. to the units that compose the API for dynamically-linked
code, and prevent access to all other units, e.g. private, internal modules
of the running program.
<<
val prohibit : string list -> unit
>>
prohibit units prohibits dynamically-linked units from referencing the
units named in list units. This can be used to prevent access to selected
units, e.g. private, internal modules of the running program.
<<
val default_available_units : unit -> unit
>>
Reset the set of units that can be referenced from dynamically-linked code
to its default value, that is, all units composing the currently running
program.
<<
val allow_unsafe_modules : bool -> unit
>>
Govern whether unsafe object files are allowed to be dynamically linked. A
compilation unit is "unsafe" if it contains declarations of external
functions, which can break type safety. By default, dynamic linking of
unsafe object files is not allowed.
Deprecated, low-level API for access control
============================================
<<
val add_interfaces : string list -> string list -> unit
>>
add_interfaces units path grants dynamically-linked object files access to
the compilation units named in list units. The interfaces (.cmi files) for
these units are searched in path (a list of directory names).
<<
val add_available_units : (string * Digest.t) list -> unit
>>
Same as Dynlink.add_interfaces[27.1], but instead of searching .cmi files
to find the unit interfaces, uses the interface digests given for each unit.
This way, the .cmi interface files need not be available at run-time. The
digests can be extracted from .cmi files using the extract_crc program
installed in the Objective Caml standard library directory.
<<
val clear_available_units : unit -> unit
>>
Empty the list of compilation units accessible to dynamically-linked
programs.
Error reporting
===============
<<
type linking_error =
| Undefined_global of string
| Unavailable_primitive of string
| Uninitialized_global of string
>>
<<
type error =
| Not_a_bytecode_file of string
| Inconsistent_import of string
| Unavailable_unit of string
| Unsafe_file
| Linking_error of string * linking_error
| Corrupted_interface of string
| File_not_found of string
| Cannot_open_dll of string
>>
<<
exception Error of error
>>
Errors in dynamic linking are reported by raising the Error exception with
a description of the error.
<<
val error_message : error -> string
>>
Convert an error description to a printable message.
Chapter 28 The LablTk library: Tcl/Tk GUI interface
******************************************************
The labltk library provides access to the Tcl/Tk GUI from Objective Caml
programs. This interface is generated in an automated way, and you should refer
to Tcl/Tk books and man pages for detailed information on the behavior of the
numerous functions. We also suggest to use ocamlbrowser to see the types of the
various functions, that are the best documentation for the library itself.
Programs that use the labltk library must be linked as follows:
<<
ocamlc other options -I +labltk labltk.cma other files
ocamlopt other options -I +labltk labltk.cmxa other files
>>
Unix:
The labltk library is available for any system with Tcl/Tk installed,
starting from Tcl 7.5/Tk 4.1 up to Tcl/Tk 8.4. Beware that some beta
versions may have compatibility problems.
If the library was not compiled correctly, try to run again the configure
script with the option -tkdefs switches, where switches is a list of C-style
inclusion paths leading to the right tcl.h and tk.h, for instance
'-I/usr/local/include/tcl8.4 -I/usr/local/include/tk8.4'.
A script is installed, to make easier the use of the labltk library as
toplevel.
labltk This is a toplevel including the labltk library, and the path is
already set as to allow the use of the various modules. It also includes
code for the Unix and Str libraries. You can use it in place of ocaml.
Windows:
The labltk library has been precompiled for use with Tcl/Tk 8.4. You must
first have it installed on your system. It can be downloaded from
http://www.activestate.com/products/ActiveTcl/. After installing it, you
must put the dynamically loaded libraries tcl84.dll and tk84.dll (from the
bin directory of the Tcl installation) in a directory included in you path.
No toplevel is available, but you can load the library from the standard
toplevel with the following commands.
<<# #directory "+labltk";;
# #load "labltk.cma";;
>>
You can also load it directly from the command line.
<<C:\ocaml\bin> ocaml -I +labltk labltk.cma
>>
The labltk library is composed of a large number of modules.
<<Bell Imagebitmap Place
Button Imagephoto Radiobutton
Canvas Label Scale
Checkbutton Listbox Scrollbar
Clipboard Menu Selection
Dialog Menubutton Text
Entry Message Tk
Focus Option Tkwait
Frame Optionmenu Toplevel
Grab Pack Winfo
Grid Palette Wm
>>
Giving a detailed account of each of these module would be impractical here.
We will just present some of the basic functions in the module Tk. Note that
for most other modules information can be found in the Tcl man page of their
name.
28.1 Module Tk : Basic functions and types for LablTk
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Initialization and termination
==============================
<<
val openTk :
?display:string -> ?clas:string -> unit -> Widget.toplevel Widget.widget
>>
Initialize LablTk and open a toplevel window. display is described
according to the X11 conventions. clas is used for the X11 resource
mechanism.
<<
val mainLoop : unit -> unit
>>
Start the main event loop
<<
val closeTk : unit -> unit
>>
Quit the main loop and close all open windows.
<<
val destroy : 'a Widget.widget -> unit
>>
Destroy an individual widget.
Application wide commands
=========================
<<
val update : unit -> unit
>>
Synchronize display with internal state.
<<
val appname_get : unit -> string
>>
<<
val appname_set : string -> unit
>>
Get or set the application name.
Dimensions
==========
<<
type units = [ `Cm of float | `In of float | `Mm of float | `Pix of int | `Pt
of float ]
>>
<<
val pixels : units -> int
>>
Converts various on-screen units to pixels, respective to the default
display. Available units are pixels, centimeters, inches, millimeters and
points
Widget layout commands
======================
<<
type anchor = [ `Center | `E | `N | `Ne | `Nw | `S | `Se | `Sw | `W ]
>>
<<
type fillMode = [ `Both | `None | `X | `Y ]
>>
<<
type side = [ `Bottom | `Left | `Right | `Top ]
>>
<<
val pack :
?after:'a Widget.widget ->
?anchor:anchor ->
?before:'b Widget.widget ->
?expand:bool ->
?fill:fillMode ->
?inside:'c Widget.widget ->
?ipadx:int ->
?ipady:int ->
?padx:int -> ?pady:int -> ?side:side -> 'd Widget.widget list -> unit
>>
Pack a widget inside its parent, using the standard layout engine.
<<
val grid :
?column:int ->
?columnspan:int ->
?inside:'a Widget.widget ->
?ipadx:int ->
?ipady:int ->
?padx:int ->
?pady:int ->
?row:int -> ?rowspan:int -> ?sticky:string -> 'b Widget.widget list -> unit
>>
Pack a widget inside its parent, using the grid layout engine.
<<
type borderMode = [ `Ignore | `Inside | `Outside ]
>>
<<
val place :
?anchor:anchor ->
?bordermode:borderMode ->
?height:int ->
?inside:'a Widget.widget ->
?relheight:float ->
?relwidth:float ->
?relx:float ->
?rely:float -> ?width:int -> ?x:int -> ?y:int -> 'b Widget.widget -> unit
>>
Pack a widget inside its parent, at absolute coordinates.
<<
val raise_window : ?above:'a Widget.widget -> 'b Widget.widget -> unit
>>
<<
val lower_window : ?below:'a Widget.widget -> 'b Widget.widget -> unit
>>
Raise or lower the window associated to a widget.
Event handling
==============
<<
type modifier = [ `Alt
| `Button1
| `Button2
| `Button3
| `Button4
| `Button5
| `Control
| `Double
| `Lock
| `Meta
| `Mod1
| `Mod2
| `Mod3
| `Mod4
| `Mod5
| `Shift
| `Triple ]
>>
<<
type event = [ `ButtonPress
| `ButtonPressDetail of int
| `ButtonRelease
| `ButtonReleaseDetail of int
| `Circulate
| `ColorMap
| `Configure
| `Destroy
| `Enter
| `Expose
| `FocusIn
| `FocusOut
| `Gravity
| `KeyPress
| `KeyPressDetail of string
| `KeyRelease
| `KeyReleaseDetail of string
| `Leave
| `Map
| `Modified of modifier list * event
| `Motion
| `Property
| `Reparent
| `Unmap
| `Visibility ]
>>
An event can be either a basic X event, or modified by a key or mouse
modifier.
<<
type eventInfo = {
mutable ev_Above : int ;
mutable ev_ButtonNumber : int ;
mutable ev_Count : int ;
mutable ev_Detail : string ;
mutable ev_Focus : bool ;
mutable ev_Height : int ;
mutable ev_KeyCode : int ;
mutable ev_Mode : string ;
mutable ev_OverrideRedirect : bool ;
mutable ev_Place : string ;
mutable ev_State : string ;
mutable ev_Time : int ;
mutable ev_Width : int ;
mutable ev_MouseX : int ;
mutable ev_MouseY : int ;
mutable ev_Char : string ;
mutable ev_BorderWidth : int ;
mutable ev_SendEvent : bool ;
mutable ev_KeySymString : string ;
mutable ev_KeySymInt : int ;
mutable ev_RootWindow : int ;
mutable ev_SubWindow : int ;
mutable ev_Type : int ;
mutable ev_Widget : Widget.any Widget.widget ;
mutable ev_RootX : int ;
mutable ev_RootY : int ;
}
>>
Event related information accessible in callbacks.
<<
type eventField = [ `Above
| `BorderWidth
| `ButtonNumber
| `Char
| `Count
| `Detail
| `Focus
| `Height
| `KeyCode
| `KeySymInt
| `KeySymString
| `Mode
| `MouseX
| `MouseY
| `OverrideRedirect
| `Place
| `RootWindow
| `RootX
| `RootY
| `SendEvent
| `State
| `SubWindow
| `Time
| `Type
| `Widget
| `Width ]
>>
In order to access the above event information, one has to pass a list of
required event fields to the bind function.
<<
val bind :
events:event list ->
?extend:bool ->
?breakable:bool ->
?fields:eventField list ->
?action:(eventInfo -> unit) -> 'a Widget.widget -> unit
>>
Bind a succession of events on a widget to an action. If extend is true
then then binding is added after existing ones, otherwise it replaces them.
breakable should be true when break is to be called inside the action.
action is called with the fields required set in an eventInfo structure.
Other fields should not be accessed. If action is omitted then existing
bindings are removed.
<<
val bind_class :
events:event list ->
?extend:bool ->
?breakable:bool ->
?fields:eventField list ->
?action:(eventInfo -> unit) -> ?on:'a Widget.widget -> string -> unit
>>
Same thing for all widgets of a given class. If a widget is given with
label ~on:, the binding will be removed as soon as it is destroyed.
<<
val bind_tag :
events:event list ->
?extend:bool ->
?breakable:bool ->
?fields:eventField list ->
?action:(eventInfo -> unit) -> ?on:'a Widget.widget -> string -> unit
>>
Same thing for all widgets having a given tag
<<
val break : unit -> unit
>>
Used inside a bound action, do not call other actions after this one. This
is only possible if this action was bound with ~breakable:true.
Chapter 29 The bigarray library
**********************************
The bigarray library implements large, multi-dimensional, numerical arrays.
These arrays are called "big arrays" to distinguish them from the standard Caml
arrays described in section 20.2. The main differences between "big arrays"
and standard Caml arrays are as follows:
- Big arrays are not limited in size, unlike Caml arrays (float array are
limited to 2097151 elements on a 32-bit platform, other array types to
4194303 elements).
- Big arrays are multi-dimensional. Any number of dimensions between 1 and 16
is supported. In contrast, Caml arrays are mono-dimensional and require
encoding multi-dimensional arrays as arrays of arrays.
- Big arrays can only contain integers and floating-point numbers, while Caml
arrays can contain arbitrary Caml data types. However, big arrays provide
more space-efficient storage of integer and floating-point elements, in
particular because they support "small" types such as single-precision
floats and 8 and 16-bit integers, in addition to the standard Caml types of
double-precision floats and 32 and 64-bit integers.
- The memory layout of big arrays is entirely compatible with that of arrays
in C and Fortran, allowing large arrays to be passed back and forth between
Caml code and C / Fortran code with no data copying at all.
- Big arrays support interesting high-level operations that normal arrays do
not provide efficiently, such as extracting sub-arrays and "slicing" a
multi-dimensional array along certain dimensions, all without any copying.
Programs that use the bigarray library must be linked as follows:
<<
ocamlc other options bigarray.cma other files
ocamlopt other options bigarray.cmxa other files
>>
For interactive use of the bigarray library, do:
<<
ocamlmktop -o mytop bigarray.cma
./mytop
>>
or (if dynamic linking of C libraries is supported on your platform), start
ocaml and type #load "bigarray.cma";;.
29.1 Module Bigarray : Large, multi-dimensional, numerical arrays.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
This module implements multi-dimensional arrays of integers and
floating-point numbers, thereafter referred to as "big arrays". The
implementation allows efficient sharing of large numerical arrays between Caml
code and C or Fortran numerical libraries.
Concerning the naming conventions, users of this module are encouraged to do
open Bigarray in their source, then refer to array types and operations via
short dot notation, e.g. Array1.t or Array2.sub.
Big arrays support all the Caml ad-hoc polymorphic operations:
- comparisons (=, <>, <=, etc, as well as Pervasives.compare[19.2]);
- hashing (module Hash);
- and structured input-output (Pervasives.output_value[19.2] and
Pervasives.input_value[19.2], as well as the functions from the
Marshal[20.19] module).
Element kinds
=============
Big arrays can contain elements of the following kinds:
- IEEE single precision (32 bits) floating-point numbers
(Bigarray.float32_elt[29.1]),
- IEEE double precision (64 bits) floating-point numbers
(Bigarray.float64_elt[29.1]),
- IEEE single precision (2 * 32 bits) floating-point complex numbers
(Bigarray.complex32_elt[29.1]),
- IEEE double precision (2 * 64 bits) floating-point complex numbers
(Bigarray.complex64_elt[29.1]),
- 8-bit integers (signed or unsigned) (Bigarray.int8_signed_elt[29.1] or
Bigarray.int8_unsigned_elt[29.1]),
- 16-bit integers (signed or unsigned) (Bigarray.int16_signed_elt[29.1] or
Bigarray.int16_unsigned_elt[29.1]),
- Caml integers (signed, 31 bits on 32-bit architectures, 63 bits on 64-bit
architectures) (Bigarray.int_elt[29.1]),
- 32-bit signed integer (Bigarray.int32_elt[29.1]),
- 64-bit signed integers (Bigarray.int64_elt[29.1]),
- platform-native signed integers (32 bits on 32-bit architectures, 64 bits on
64-bit architectures) (Bigarray.nativeint_elt[29.1]).
Each element kind is represented at the type level by one of the abstract
types defined below.
<<
type float32_elt
>>
<<
type float64_elt
>>
<<
type complex32_elt
>>
<<
type complex64_elt
>>
<<
type int8_signed_elt
>>
<<
type int8_unsigned_elt
>>
<<
type int16_signed_elt
>>
<<
type int16_unsigned_elt
>>
<<
type int_elt
>>
<<
type int32_elt
>>
<<
type int64_elt
>>
<<
type nativeint_elt
>>
<<
type ('a, 'b) kind
>>
To each element kind is associated a Caml type, which is the type of Caml
values that can be stored in the big array or read back from it. This type
is not necessarily the same as the type of the array elements proper: for
instance, a big array whose elements are of kind float32_elt contains 32-bit
single precision floats, but reading or writing one of its elements from
Caml uses the Caml type float, which is 64-bit double precision floats.
The abstract type ('a, 'b) kind captures this association of a Caml type 'a
for values read or written in the big array, and of an element kind 'b which
represents the actual contents of the big array. The following predefined
values of type kind list all possible associations of Caml types with
element kinds:
<<
val float32 : (float, float32_elt) kind
>>
See Bigarray.char[29.1].
<<
val float64 : (float, float64_elt) kind
>>
See Bigarray.char[29.1].
<<
val complex32 : (Complex.t, complex32_elt) kind
>>
See Bigarray.char[29.1].
<<
val complex64 : (Complex.t, complex64_elt) kind
>>
See Bigarray.char[29.1].
<<
val int8_signed : (int, int8_signed_elt) kind
>>
See Bigarray.char[29.1].
<<
val int8_unsigned : (int, int8_unsigned_elt) kind
>>
See Bigarray.char[29.1].
<<
val int16_signed : (int, int16_signed_elt) kind
>>
See Bigarray.char[29.1].
<<
val int16_unsigned : (int, int16_unsigned_elt) kind
>>
See Bigarray.char[29.1].
<<
val int : (int, int_elt) kind
>>
See Bigarray.char[29.1].
<<
val int32 : (int32, int32_elt) kind
>>
See Bigarray.char[29.1].
<<
val int64 : (int64, int64_elt) kind
>>
See Bigarray.char[29.1].
<<
val nativeint : (nativeint, nativeint_elt) kind
>>
See Bigarray.char[29.1].
<<
val char : (char, int8_unsigned_elt) kind
>>
As shown by the types of the values above, big arrays of kind float32_elt
and float64_elt are accessed using the Caml type float. Big arrays of
complex kinds complex32_elt, complex64_elt are accessed with the Caml type
Complex.t[20.6]. Big arrays of integer kinds are accessed using the smallest
Caml integer type large enough to represent the array elements: int for 8-
and 16-bit integer bigarrays, as well as Caml-integer bigarrays; int32 for
32-bit integer bigarrays; int64 for 64-bit integer bigarrays; and nativeint
for platform-native integer bigarrays. Finally, big arrays of kind
int8_unsigned_elt can also be accessed as arrays of characters instead of
arrays of small integers, by using the kind value char instead of
int8_unsigned.
Array layouts
=============
<<
type c_layout
>>
See Bigarray.fortran_layout[29.1].
<<
type fortran_layout
>>
To facilitate interoperability with existing C and Fortran code, this
library supports two different memory layouts for big arrays, one compatible
with the C conventions, the other compatible with the Fortran conventions.
In the C-style layout, array indices start at 0, and multi-dimensional
arrays are laid out in row-major format. That is, for a two-dimensional
array, all elements of row 0 are contiguous in memory, followed by all
elements of row 1, etc. In other terms, the array elements at (x,y) and (x,
y+1) are adjacent in memory.
In the Fortran-style layout, array indices start at 1, and multi-dimensional
arrays are laid out in column-major format. That is, for a two-dimensional
array, all elements of column 0 are contiguous in memory, followed by all
elements of column 1, etc. In other terms, the array elements at (x,y) and
(x+1, y) are adjacent in memory.
Each layout style is identified at the type level by the abstract types
Bigarray.c_layout[29.1] and fortran_layout respectively.
<<
type 'a layout
>>
The type 'a layout represents one of the two supported memory layouts:
C-style if 'a is Bigarray.c_layout[29.1], Fortran-style if 'a is
Bigarray.fortran_layout[29.1].
Supported layouts
-----------------
The abstract values c_layout and fortran_layout represent the two supported
layouts at the level of values.
<<
val c_layout : c_layout layout
>>
<<
val fortran_layout : fortran_layout layout
>>
Generic arrays (of arbitrarily many dimensions)
===============================================
<<
module Genarray : >>
sig
<<
type ('a, 'b, 'c) t
>>
The type Genarray.t is the type of big arrays with variable numbers of
dimensions. Any number of dimensions between 1 and 16 is supported.
The three type parameters to Genarray.t identify the array element kind
and layout, as follows:
- the first parameter, 'a, is the Caml type for accessing array elements
(float, int, int32, int64, nativeint);
- the second parameter, 'b, is the actual kind of array elements
(float32_elt, float64_elt, int8_signed_elt, int8_unsigned_elt, etc);
- the third parameter, 'c, identifies the array layout (c_layout or
fortran_layout).
For instance, (float, float32_elt, fortran_layout) Genarray.t is the type
of generic big arrays containing 32-bit floats in Fortran layout; reads
and writes in this array use the Caml type float.
<<
val create :
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> int array -> ('a, 'b, 'c) t
>>
Genarray.create kind layout dimensions returns a new big array whose
element kind is determined by the parameter kind (one of float32,
float64, int8_signed, etc) and whose layout is determined by the
parameter layout (one of c_layout or fortran_layout). The dimensions
parameter is an array of integers that indicate the size of the big array
in each dimension. The length of dimensions determines the number of
dimensions of the bigarray.
For instance, Genarray.create int32 c_layout [|4;6;8|] returns a fresh
big array of 32-bit integers, in C layout, having three dimensions, the
three dimensions being 4, 6 and 8 respectively.
Big arrays returned by Genarray.create are not initialized: the initial
values of array elements is unspecified.
Genarray.create raises Invalid_arg if the number of dimensions is not in
the range 1 to 16 inclusive, or if one of the dimensions is negative.
<<
val num_dims : ('a, 'b, 'c) t -> int
>>
Return the number of dimensions of the given big array.
<<
val dims : ('a, 'b, 'c) t -> int array
>>
Genarray.dims a returns all dimensions of the big array a, as an array
of integers of length Genarray.num_dims a.
<<
val nth_dim : ('a, 'b, 'c) t -> int -> int
>>
Genarray.nth_dim a n returns the n-th dimension of the big array a. The
first dimension corresponds to n = 0; the second dimension corresponds to
n = 1; the last dimension, to n = Genarray.num_dims a - 1. Raise
Invalid_arg if n is less than 0 or greater or equal than
Genarray.num_dims a.
<<
val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
>>
Return the kind of the given big array.
<<
val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
>>
Return the layout of the given big array.
<<
val get : ('a, 'b, 'c) t -> int array -> 'a
>>
Read an element of a generic big array. Genarray.get a [|i1; ...; iN|]
returns the element of a whose coordinates are i1 in the first dimension,
i2 in the second dimension, ..., iN in the N-th dimension.
If a has C layout, the coordinates must be greater or equal than 0 and
strictly less than the corresponding dimensions of a. If a has Fortran
layout, the coordinates must be greater or equal than 1 and less or equal
than the corresponding dimensions of a. Raise Invalid_arg if the array a
does not have exactly N dimensions, or if the coordinates are outside the
array bounds.
If N > 3, alternate syntax is provided: you can write a.{i1, i2, ..., iN}
instead of Genarray.get a [|i1; ...; iN|]. (The syntax a.{...} with one,
two or three coordinates is reserved for accessing one-, two- and
three-dimensional arrays as described below.)
<<
val set : ('a, 'b, 'c) t -> int array -> 'a -> unit
>>
Assign an element of a generic big array. Genarray.set a [|i1; ...; iN|]
v stores the value v in the element of a whose coordinates are i1 in the
first dimension, i2 in the second dimension, ..., iN in the N-th
dimension.
The array a must have exactly N dimensions, and all coordinates must lie
inside the array bounds, as described for Genarray.get; otherwise,
Invalid_arg is raised.
If N > 3, alternate syntax is provided: you can write a.{i1, i2, ..., iN}
<- v instead of Genarray.set a [|i1; ...; iN|] v. (The syntax a.{...} <-
v with one, two or three coordinates is reserved for updating one-, two-
and three-dimensional arrays as described below.)
<<
val sub_left :
('a, 'b, Bigarray.c_layout) t ->
int -> int -> ('a, 'b, Bigarray.c_layout) t
>>
Extract a sub-array of the given big array by restricting the first
(left-most) dimension. Genarray.sub_left a ofs len returns a big array
with the same number of dimensions as a, and the same dimensions as a,
except the first dimension, which corresponds to the interval [ofs ...
ofs + len - 1] of the first dimension of a. No copying of elements is
involved: the sub-array and the original array share the same storage
space. In other terms, the element at coordinates [|i1; ...; iN|] of the
sub-array is identical to the element at coordinates [|i1+ofs; ...; iN|]
of the original array a.
Genarray.sub_left applies only to big arrays in C layout. Raise
Invalid_arg if ofs and len do not designate a valid sub-array of a, that
is, if ofs < 0, or len < 0, or ofs + len > Genarray.nth_dim a 0.
<<
val sub_right :
('a, 'b, Bigarray.fortran_layout) t ->
int -> int -> ('a, 'b, Bigarray.fortran_layout) t
>>
Extract a sub-array of the given big array by restricting the last
(right-most) dimension. Genarray.sub_right a ofs len returns a big array
with the same number of dimensions as a, and the same dimensions as a,
except the last dimension, which corresponds to the interval [ofs ... ofs
+ len - 1] of the last dimension of a. No copying of elements is
involved: the sub-array and the original array share the same storage
space. In other terms, the element at coordinates [|i1; ...; iN|] of the
sub-array is identical to the element at coordinates [|i1; ...; iN+ofs|]
of the original array a.
Genarray.sub_right applies only to big arrays in Fortran layout. Raise
Invalid_arg if ofs and len do not designate a valid sub-array of a, that
is, if ofs < 1, or len < 0, or ofs + len > Genarray.nth_dim a
(Genarray.num_dims a - 1).
<<
val slice_left :
('a, 'b, Bigarray.c_layout) t ->
int array -> ('a, 'b, Bigarray.c_layout) t
>>
Extract a sub-array of lower dimension from the given big array by
fixing one or several of the first (left-most) coordinates.
Genarray.slice_left a [|i1; ... ; iM|] returns the "slice" of a obtained
by setting the first M coordinates to i1, ..., iM. If a has N dimensions,
the slice has dimension N - M, and the element at coordinates [|j1; ...;
j(N-M)|] in the slice is identical to the element at coordinates [|i1;
...; iM; j1; ...; j(N-M)|] in the original array a. No copying of
elements is involved: the slice and the original array share the same
storage space.
Genarray.slice_left applies only to big arrays in C layout. Raise
Invalid_arg if M >= N, or if [|i1; ... ; iM|] is outside the bounds of a.
<<
val slice_right :
('a, 'b, Bigarray.fortran_layout) t ->
int array -> ('a, 'b, Bigarray.fortran_layout) t
>>
Extract a sub-array of lower dimension from the given big array by
fixing one or several of the last (right-most) coordinates.
Genarray.slice_right a [|i1; ... ; iM|] returns the "slice" of a obtained
by setting the last M coordinates to i1, ..., iM. If a has N dimensions,
the slice has dimension N - M, and the element at coordinates [|j1; ...;
j(N-M)|] in the slice is identical to the element at coordinates [|j1;
...; j(N-M); i1; ...; iM|] in the original array a. No copying of
elements is involved: the slice and the original array share the same
storage space.
Genarray.slice_right applies only to big arrays in Fortran layout. Raise
Invalid_arg if M >= N, or if [|i1; ... ; iM|] is outside the bounds of a.
<<
val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
>>
Copy all elements of a big array in another big array. Genarray.blit src
dst copies all elements of src into dst. Both arrays src and dst must
have the same number of dimensions and equal dimensions. Copying a
sub-array of src to a sub-array of dst can be achieved by applying
Genarray.blit to sub-array or slices of src and dst.
<<
val fill : ('a, 'b, 'c) t -> 'a -> unit
>>
Set all elements of a big array to a given value. Genarray.fill a v
stores the value v in all elements of the big array a. Setting only some
elements of a to v can be achieved by applying Genarray.fill to a
sub-array or a slice of a.
<<
val map_file :
Unix.file_descr ->
?pos:int64 ->
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> bool -> int array -> ('a, 'b, 'c) t
>>
Memory mapping of a file as a big array. Genarray.map_file fd kind
layout shared dims returns a big array of kind kind, layout layout, and
dimensions as specified in dims. The data contained in this big array are
the contents of the file referred to by the file descriptor fd (as opened
previously with Unix.openfile, for example). The optional pos parameter
is the byte offset in the file of the data being mapped; it default to 0
(map from the beginning of the file).
If shared is true, all modifications performed on the array are reflected
in the file. This requires that fd be opened with write permissions. If
shared is false, modifications performed on the array are done in memory
only, using copy-on-write of the modified pages; the underlying file is
not affected.
Genarray.map_file is much more efficient than reading the whole file in a
big array, modifying that big array, and writing it afterwards.
To adjust automatically the dimensions of the big array to the actual
size of the file, the major dimension (that is, the first dimension for
an array with C layout, and the last dimension for an array with Fortran
layout) can be given as -1. Genarray.map_file then determines the major
dimension from the size of the file. The file must contain an integral
number of sub-arrays as determined by the non-major dimensions, otherwise
Failure is raised.
If all dimensions of the big array are given, the file size is matched
against the size of the big array. If the file is larger than the big
array, only the initial portion of the file is mapped to the big array.
If the file is smaller than the big array, the file is automatically
grown to the size of the big array. This requires write permissions on
fd.
end
One-dimensional arrays
======================
<<
module Array1 : >>
sig
<<
type ('a, 'b, 'c) t
>>
The type of one-dimensional big arrays whose elements have Caml type 'a,
representation kind 'b, and memory layout 'c.
<<
val create :
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> int -> ('a, 'b, 'c) t
>>
Array1.create kind layout dim returns a new bigarray of one dimension,
whose size is dim. kind and layout determine the array element kind and
the array layout as described for Genarray.create.
<<
val dim : ('a, 'b, 'c) t -> int
>>
Return the size (dimension) of the given one-dimensional big array.
<<
val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
>>
Return the kind of the given big array.
<<
val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
>>
Return the layout of the given big array.
<<
val get : ('a, 'b, 'c) t -> int -> 'a
>>
Array1.get a x, or alternatively a.{x}, returns the element of a at
index x. x must be greater or equal than 0 and strictly less than
Array1.dim a if a has C layout. If a has Fortran layout, x must be
greater or equal than 1 and less or equal than Array1.dim a. Otherwise,
Invalid_arg is raised.
<<
val set : ('a, 'b, 'c) t -> int -> 'a -> unit
>>
Array1.set a x v, also written a.{x} <- v, stores the value v at index x
in a. x must be inside the bounds of a as described in
Bigarray.Array1.get[29.1]; otherwise, Invalid_arg is raised.
<<
val sub : ('a, 'b, 'c) t ->
int -> int -> ('a, 'b, 'c) t
>>
Extract a sub-array of the given one-dimensional big array. See
Genarray.sub_left for more details.
<<
val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
>>
Copy the first big array to the second big array. See Genarray.blit for
more details.
<<
val fill : ('a, 'b, 'c) t -> 'a -> unit
>>
Fill the given big array with the given value. See Genarray.fill for
more details.
<<
val of_array :
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> 'a array -> ('a, 'b, 'c) t
>>
Build a one-dimensional big array initialized from the given array.
<<
val map_file :
Unix.file_descr ->
?pos:int64 ->
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> bool -> int -> ('a, 'b, 'c) t
>>
Memory mapping of a file as a one-dimensional big array. See
Bigarray.Genarray.map_file[29.1] for more details.
end
One-dimensional arrays. The Array1 structure provides operations similar to
those of Bigarray.Genarray[29.1], but specialized to the case of
one-dimensional arrays. (The Array2 and Array3 structures below provide
operations specialized for two- and three-dimensional arrays.) Statically
knowing the number of dimensions of the array allows faster operations, and
more precise static type-checking.
Two-dimensional arrays
======================
<<
module Array2 : >>
sig
<<
type ('a, 'b, 'c) t
>>
The type of two-dimensional big arrays whose elements have Caml type 'a,
representation kind 'b, and memory layout 'c.
<<
val create :
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> int -> int -> ('a, 'b, 'c) t
>>
Array2.create kind layout dim1 dim2 returns a new bigarray of two
dimension, whose size is dim1 in the first dimension and dim2 in the
second dimension. kind and layout determine the array element kind and
the array layout as described for Bigarray.Genarray.create[29.1].
<<
val dim1 : ('a, 'b, 'c) t -> int
>>
Return the first dimension of the given two-dimensional big array.
<<
val dim2 : ('a, 'b, 'c) t -> int
>>
Return the second dimension of the given two-dimensional big array.
<<
val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
>>
Return the kind of the given big array.
<<
val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
>>
Return the layout of the given big array.
<<
val get : ('a, 'b, 'c) t -> int -> int -> 'a
>>
Array2.get a x y, also written a.{x,y}, returns the element of a at
coordinates (x, y). x and y must be within the bounds of a, as described
for Bigarray.Genarray.get[29.1]; otherwise, Invalid_arg is raised.
<<
val set : ('a, 'b, 'c) t -> int -> int -> 'a -> unit
>>
Array2.set a x y v, or alternatively a.{x,y} <- v, stores the value v at
coordinates (x, y) in a. x and y must be within the bounds of a, as
described for Bigarray.Genarray.set[29.1]; otherwise, Invalid_arg is
raised.
<<
val sub_left :
('a, 'b, Bigarray.c_layout) t ->
int -> int -> ('a, 'b, Bigarray.c_layout) t
>>
Extract a two-dimensional sub-array of the given two-dimensional big
array by restricting the first dimension. See
Bigarray.Genarray.sub_left[29.1] for more details. Array2.sub_left
applies only to arrays with C layout.
<<
val sub_right :
('a, 'b, Bigarray.fortran_layout) t ->
int -> int -> ('a, 'b, Bigarray.fortran_layout) t
>>
Extract a two-dimensional sub-array of the given two-dimensional big
array by restricting the second dimension. See
Bigarray.Genarray.sub_right[29.1] for more details. Array2.sub_right
applies only to arrays with Fortran layout.
<<
val slice_left :
('a, 'b, Bigarray.c_layout) t ->
int -> ('a, 'b, Bigarray.c_layout) Bigarray.Array1.t
>>
Extract a row (one-dimensional slice) of the given two-dimensional big
array. The integer parameter is the index of the row to extract. See
Bigarray.Genarray.slice_left[29.1] for more details. Array2.slice_left
applies only to arrays with C layout.
<<
val slice_right :
('a, 'b, Bigarray.fortran_layout) t ->
int -> ('a, 'b, Bigarray.fortran_layout) Bigarray.Array1.t
>>
Extract a column (one-dimensional slice) of the given two-dimensional
big array. The integer parameter is the index of the column to extract.
See Bigarray.Genarray.slice_right[29.1] for more details.
Array2.slice_right applies only to arrays with Fortran layout.
<<
val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
>>
Copy the first big array to the second big array. See
Bigarray.Genarray.blit[29.1] for more details.
<<
val fill : ('a, 'b, 'c) t -> 'a -> unit
>>
Fill the given big array with the given value. See
Bigarray.Genarray.fill[29.1] for more details.
<<
val of_array :
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> 'a array array -> ('a, 'b, 'c) t
>>
Build a two-dimensional big array initialized from the given array of
arrays.
<<
val map_file :
Unix.file_descr ->
?pos:int64 ->
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> bool -> int -> int -> ('a, 'b, 'c) t
>>
Memory mapping of a file as a two-dimensional big array. See
Bigarray.Genarray.map_file[29.1] for more details.
end
Two-dimensional arrays. The Array2 structure provides operations similar to
those of Bigarray.Genarray[29.1], but specialized to the case of
two-dimensional arrays.
Three-dimensional arrays
========================
<<
module Array3 : >>
sig
<<
type ('a, 'b, 'c) t
>>
The type of three-dimensional big arrays whose elements have Caml type
'a, representation kind 'b, and memory layout 'c.
<<
val create :
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> int -> int -> int -> ('a, 'b, 'c) t
>>
Array3.create kind layout dim1 dim2 dim3 returns a new bigarray of three
dimension, whose size is dim1 in the first dimension, dim2 in the second
dimension, and dim3 in the third. kind and layout determine the array
element kind and the array layout as described for
Bigarray.Genarray.create[29.1].
<<
val dim1 : ('a, 'b, 'c) t -> int
>>
Return the first dimension of the given three-dimensional big array.
<<
val dim2 : ('a, 'b, 'c) t -> int
>>
Return the second dimension of the given three-dimensional big array.
<<
val dim3 : ('a, 'b, 'c) t -> int
>>
Return the third dimension of the given three-dimensional big array.
<<
val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
>>
Return the kind of the given big array.
<<
val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
>>
Return the layout of the given big array.
<<
val get : ('a, 'b, 'c) t -> int -> int -> int -> 'a
>>
Array3.get a x y z, also written a.{x,y,z}, returns the element of a at
coordinates (x, y, z). x, y and z must be within the bounds of a, as
described for Bigarray.Genarray.get[29.1]; otherwise, Invalid_arg is
raised.
<<
val set : ('a, 'b, 'c) t -> int -> int -> int -> 'a -> unit
>>
Array3.set a x y v, or alternatively a.{x,y,z} <- v, stores the value v
at coordinates (x, y, z) in a. x, y and z must be within the bounds of a,
as described for Bigarray.Genarray.set[29.1]; otherwise, Invalid_arg is
raised.
<<
val sub_left :
('a, 'b, Bigarray.c_layout) t ->
int -> int -> ('a, 'b, Bigarray.c_layout) t
>>
Extract a three-dimensional sub-array of the given three-dimensional big
array by restricting the first dimension. See
Bigarray.Genarray.sub_left[29.1] for more details. Array3.sub_left
applies only to arrays with C layout.
<<
val sub_right :
('a, 'b, Bigarray.fortran_layout) t ->
int -> int -> ('a, 'b, Bigarray.fortran_layout) t
>>
Extract a three-dimensional sub-array of the given three-dimensional big
array by restricting the second dimension. See
Bigarray.Genarray.sub_right[29.1] for more details. Array3.sub_right
applies only to arrays with Fortran layout.
<<
val slice_left_1 :
('a, 'b, Bigarray.c_layout) t ->
int -> int -> ('a, 'b, Bigarray.c_layout) Bigarray.Array1.t
>>
Extract a one-dimensional slice of the given three-dimensional big array
by fixing the first two coordinates. The integer parameters are the
coordinates of the slice to extract. See
Bigarray.Genarray.slice_left[29.1] for more details. Array3.slice_left_1
applies only to arrays with C layout.
<<
val slice_right_1 :
('a, 'b, Bigarray.fortran_layout) t ->
int -> int -> ('a, 'b, Bigarray.fortran_layout) Bigarray.Array1.t
>>
Extract a one-dimensional slice of the given three-dimensional big array
by fixing the last two coordinates. The integer parameters are the
coordinates of the slice to extract. See
Bigarray.Genarray.slice_right[29.1] for more details.
Array3.slice_right_1 applies only to arrays with Fortran layout.
<<
val slice_left_2 :
('a, 'b, Bigarray.c_layout) t ->
int -> ('a, 'b, Bigarray.c_layout) Bigarray.Array2.t
>>
Extract a two-dimensional slice of the given three-dimensional big array
by fixing the first coordinate. The integer parameter is the first
coordinate of the slice to extract. See
Bigarray.Genarray.slice_left[29.1] for more details. Array3.slice_left_2
applies only to arrays with C layout.
<<
val slice_right_2 :
('a, 'b, Bigarray.fortran_layout) t ->
int -> ('a, 'b, Bigarray.fortran_layout) Bigarray.Array2.t
>>
Extract a two-dimensional slice of the given three-dimensional big array
by fixing the last coordinate. The integer parameter is the coordinate of
the slice to extract. See Bigarray.Genarray.slice_right[29.1] for more
details. Array3.slice_right_2 applies only to arrays with Fortran layout.
<<
val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
>>
Copy the first big array to the second big array. See
Bigarray.Genarray.blit[29.1] for more details.
<<
val fill : ('a, 'b, 'c) t -> 'a -> unit
>>
Fill the given big array with the given value. See
Bigarray.Genarray.fill[29.1] for more details.
<<
val of_array :
('a, 'b) Bigarray.kind ->
'c Bigarray.layout -> 'a array array array -> ('a, 'b, 'c) t
>>
Build a three-dimensional big array initialized from the given array of
arrays of arrays.
<<
val map_file :
Unix.file_descr ->
?pos:int64 ->
('a, 'b) Bigarray.kind ->
'c Bigarray.layout ->
bool -> int -> int -> int -> ('a, 'b, 'c) t
>>
Memory mapping of a file as a three-dimensional big array. See
Bigarray.Genarray.map_file[29.1] for more details.
end
Three-dimensional arrays. The Array3 structure provides operations similar
to those of Bigarray.Genarray[29.1], but specialized to the case of
three-dimensional arrays.
Coercions between generic big arrays and fixed-dimension big arrays
===================================================================
<<
val genarray_of_array1 : ('a, 'b, 'c) Array1.t -> ('a, 'b, 'c) Genarray.t
>>
Return the generic big array corresponding to the given one-dimensional big
array.
<<
val genarray_of_array2 : ('a, 'b, 'c) Array2.t -> ('a, 'b, 'c) Genarray.t
>>
Return the generic big array corresponding to the given two-dimensional big
array.
<<
val genarray_of_array3 : ('a, 'b, 'c) Array3.t -> ('a, 'b, 'c) Genarray.t
>>
Return the generic big array corresponding to the given three-dimensional
big array.
<<
val array1_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array1.t
>>
Return the one-dimensional big array corresponding to the given generic big
array. Raise Invalid_arg if the generic big array does not have exactly one
dimension.
<<
val array2_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array2.t
>>
Return the two-dimensional big array corresponding to the given generic big
array. Raise Invalid_arg if the generic big array does not have exactly two
dimensions.
<<
val array3_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array3.t
>>
Return the three-dimensional big array corresponding to the given generic
big array. Raise Invalid_arg if the generic big array does not have exactly
three dimensions.
Re-shaping big arrays
=====================
<<
val reshape :
('a, 'b, 'c) Genarray.t ->
int array -> ('a, 'b, 'c) Genarray.t
>>
reshape b [|d1;...;dN|] converts the big array b to a N-dimensional array
of dimensions d1...dN. The returned array and the original array b share
their data and have the same layout. For instance, assuming that b is a
one-dimensional array of dimension 12, reshape b [|3;4|] returns a
two-dimensional array b' of dimensions 3 and 4. If b has C layout, the
element (x,y) of b' corresponds to the element x * 3 + y of b. If b has
Fortran layout, the element (x,y) of b' corresponds to the element x + (y -
1) * 4 of b. The returned big array must have exactly the same number of
elements as the original big array b. That is, the product of the dimensions
of b must be equal to i1 * ... * iN. Otherwise, Invalid_arg is raised.
<<
val reshape_1 : ('a, 'b, 'c) Genarray.t -> int -> ('a, 'b, 'c) Array1.t
>>
Specialized version of Bigarray.reshape[29.1] for reshaping to
one-dimensional arrays.
<<
val reshape_2 :
('a, 'b, 'c) Genarray.t ->
int -> int -> ('a, 'b, 'c) Array2.t
>>
Specialized version of Bigarray.reshape[29.1] for reshaping to
two-dimensional arrays.
<<
val reshape_3 :
('a, 'b, 'c) Genarray.t ->
int -> int -> int -> ('a, 'b, 'c) Array3.t
>>
Specialized version of Bigarray.reshape[29.1] for reshaping to
three-dimensional arrays.
29.2 Big arrays in the Caml-C interface
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
C stub code that interface C or Fortran code with Caml code, as described in
chapter 18, can exploit big arrays as follows.
29.2.1 Include file
====================
The include file <caml/bigarray.h> must be included in the C stub file. It
declares the functions, constants and macros discussed below.
29.2.2 Accessing a Caml bigarray from C or Fortran
===================================================
If v is a Caml value representing a big array, the expression
Data_bigarray_val(v) returns a pointer to the data part of the array. This
pointer is of type void * and can be cast to the appropriate C type for the
array (e.g. double [], char [][10], etc).
Various characteristics of the Caml big array can be consulted from C as
follows:
--------------------------------------------------------------------
| C expression | Returns |
--------------------------------------------------------------------
| Bigarray_val(v)->num_dims |number of dimensions |
|Bigarray_val(v)->dim[i] |i-th dimension |
|Bigarray_val(v)->flags & BIGARRAY_KIND_MASK|kind of array elements|
--------------------------------------------------------------------
The kind of array elements is one of the following constants:
--------------------------------------------------------------
| Constant | Element kind |
--------------------------------------------------------------
| BIGARRAY_FLOAT32 |32-bit single-precision floats |
|BIGARRAY_FLOAT64 |64-bit double-precision floats |
|BIGARRAY_SINT8 |8-bit signed integers |
|BIGARRAY_UINT8 |8-bit unsigned integers |
|BIGARRAY_SINT16 |16-bit signed integers |
|BIGARRAY_UINT16 |16-bit unsigned integers |
|BIGARRAY_INT32 |32-bit signed integers |
|BIGARRAY_INT64 |64-bit signed integers |
|BIGARRAY_CAML_INT |31- or 63-bit signed integers |
|BIGARRAY_NATIVE_INT|32- or 64-bit (platform-native) integers|
--------------------------------------------------------------
The following example shows the passing of a two-dimensional big array to a
C function and a Fortran function.
<< extern void my_c_function(double * data, int dimx, int dimy);
extern void my_fortran_function_(double * data, int * dimx, int * dimy);
value caml_stub(value bigarray)
{
int dimx = Bigarray_val(bigarray)->dim[0];
int dimy = Bigarray_val(bigarray)->dim[1];
/* C passes scalar parameters by value */
my_c_function(Data_bigarray_val(bigarray), dimx, dimy);
/* Fortran passes all parameters by reference */
my_fortran_function_(Data_bigarray_val(bigarray), &dimx, &dimy);
return Val_unit;
}
>>
29.2.3 Wrapping a C or Fortran array as a Caml big array
=========================================================
A pointer p to an already-allocated C or Fortran array can be wrapped and
returned to Caml as a big array using the alloc_bigarray or alloc_bigarray_dims
functions.
- alloc_bigarray(kind | layout, numdims, p, dims)
Return a Caml big array wrapping the data pointed to by p. kind is the kind of
array elements (one of the BIGARRAY_ kind constants above). layout is
BIGARRAY_C_LAYOUT for an array with C layout and BIGARRAY_FORTRAN_LAYOUT for
an array with Fortran layout. numdims is the number of dimensions in the
array. dims is an array of numdims long integers, giving the sizes of the
array in each dimension.
- alloc_bigarray_dims(kind | layout, numdims, p, (long) dim_1, (long) dim_2,
..., (long) dim_numdims)
Same as alloc_bigarray, but the sizes of the array in each dimension are
listed as extra arguments in the function call, rather than being passed as
an array.
The following example illustrates how statically-allocated C and Fortran
arrays can be made available to Caml.
<< extern long my_c_array[100][200];
extern float my_fortran_array_[300][400];
value caml_get_c_array(value unit)
{
long dims[2];
dims[0] = 100; dims[1] = 200;
return alloc_bigarray(BIGARRAY_NATIVE_INT | BIGARRAY_C_LAYOUT,
2, my_c_array, dims);
}
value caml_get_fortran_array(value unit)
{
return alloc_bigarray_dims(BIGARRAY_FLOAT32 | BIGARRAY_FORTRAN_LAYOUT,
2, my_fortran_array_, 300L, 400L);
}
>>
Part: V
*******
Appendix
********
Chapter 30 Index to the library
**********************************
- `(&)', 19.2
- `(&&)', 19.2
- `(@)', 19.2
- `(!)', 19.2
- `(!=)', 19.2
- `(:=)', 19.2
- `(=)', 19.2
- `(==)', 19.2
- `(=/)', 22.1
- `(^)', 19.2
- `(^^)', 19.2
- `(>)', 19.2
- `(>=)', 19.2
- `(>=/)', 22.1
- `(>/)', 22.1
- `(<)', 19.2
- `(<=)', 19.2
- `(<=/)', 22.1
- `(<>)', 19.2
- `(<>/)', 22.1
- `(</)', 22.1
- `(-)', 19.2
- `(-/)', 22.1
- `(-.)', 19.2
- `(||)', 19.2
- `(+)', 19.2
- `(+/)', 22.1
- `(+.)', 19.2
- `(/)', 19.2
- `(//)', 22.1
- `(/.)', 19.2
- `(*)', 19.2
- `(*/)', 22.1
- `(**)', 19.2
- `(**/)', 22.1
- `(*.)', 19.2
- `(~-)', 19.2
- `(~-.)', 19.2
- `Arg', 20.1
- `Arith_status', 22.3
- `Array', 20.2, 20.31
- `Array1', 29.1
- `Array2', 29.1
- `Array3', 29.1
- `Assert_failure', 7.5, 19.1
- `abs', 19.2, 20.13, 20.14, 20.20
- `abs_big_int', 22.2
- `abs_float', 19.2
- `abs_num', 22.1
- `accept', 21.1, 24.5
- `access', 21.1
- `access_permission', 21.1
- `acos', 19.2
- `add', 20.6, 20.12, 20.12, 20.13, 20.14, 20.18, 20.20, 20.25, 20.28, 20.35,
26.1
- `add_available_units', 27.1
- `add_big_int', 22.2
- `add_buffer', 20.3
- `add_channel', 20.3
- `add_char', 20.3
- `add_int_big_int', 22.2
- `add_interfaces', 27.1
- `add_num', 22.1
- `add_string', 20.3
- `add_substitute', 20.3
- `add_substring', 20.3
- `addr_info', 21.1
- `alarm', 20.10, 21.1
- `align', 20.1
- `allocated_bytes', 20.10
- `allow_only', 27.1
- `allow_unsafe_modules', 27.1
- `always', 24.4
- `anchor', 28.1
- `anon_fun', 20.1
- `append', 20.2, 20.17, 20.31, 20.31
- `appname_get', 28.1
- `appname_set', 28.1
- `approx_num_exp', 22.1
- `approx_num_fix', 22.1
- `arg', 20.6
- `argv', 20.34
- `arith_status', 22.3
- `array', 19.1, 20.29
- `array1_of_genarray', 29.1
- `array2_of_genarray', 29.1
- `array3_of_genarray', 29.1
- `asin', 19.2
- `asr', 19.2
- `assoc', 20.17, 20.31
- `assq', 20.17, 20.31
- `at_exit', 19.2
- `atan', 19.2
- `atan2', 19.2
- `auto_synchronize', 25.1
- `Bad', 20.1
- `Big_int', 22.2
- `Bigarray', 29.1
- `Break', 20.34
- `Buffer', 20.3
- `background', 25.1
- `basename', 20.8
- `beginning_of_input', 20.27
- `big_int', 22.2
- `big_int_of_int', 22.2
- `big_int_of_num', 22.1
- `big_int_of_string', 22.2
- `bind', 21.1, 28.1
- `bind_class', 28.1
- `bind_tag', 28.1
- `bits', 20.26, 20.26
- `bits_of_float', 20.13, 20.14
- `black', 25.1
- `blit', 20.2, 20.31, 20.31, 20.33, 20.35, 29.1, 29.1, 29.1, 29.1
- `blit_image', 25.1
- `blue', 25.1
- `bool', 19.1, 20.26, 20.26
- `bool_of_string', 19.2
- `borderMode', 28.1
- `bounded_full_split', 23.1
- `bounded_split', 23.1
- `bounded_split_delim', 23.1
- `bprintf', 20.9, 20.24
- `break', 28.1
- `broadcast', 24.3
- `bscanf', 20.27
- `bscanf_format', 20.27
- `button_down', 25.1
- `Callback', 20.4
- `Char', 20.5
- `Complex', 20.6
- `Condition', 24.3
- `c_layout', 29.1, 29.1
- `capitalize', 20.31, 20.33
- `cardinal', 20.28
- `catch', 20.23
- `catch_break', 20.34
- `ceil', 19.2
- `ceiling_num', 22.1
- `channel', 20.7, 24.4
- `char', 19.1, 29.1
- `char_of_int', 19.2
- `chdir', 20.34, 21.1
- `check', 20.35
- `check_suffix', 20.8
- `chmod', 21.1
- `choose', 20.28, 24.4
- `chop_extension', 20.8
- `chop_suffix', 20.8
- `chown', 21.1
- `chr', 20.5
- `chroot', 21.1
- `classify_float', 19.2
- `clear', 20.3, 20.12, 20.12, 20.25, 20.30, 20.35
- `clear_available_units', 27.1
- `clear_close_on_exec', 21.1
- `clear_graph', 25.1
- `clear_nonblock', 21.1
- `clear_parser', 20.22
- `close', 21.1, 26.1
- `close_box', 20.9
- `close_graph', 25.1
- `close_in', 19.2
- `close_in_noerr', 19.2
- `close_out', 19.2
- `close_out_noerr', 19.2
- `close_process', 21.1
- `close_process_full', 21.1
- `close_process_in', 21.1
- `close_process_out', 21.1
- `close_tag', 20.9
- `close_tbox', 20.9
- `closedir', 21.1
- `closeTk', 28.1
- `code', 20.5
- `color', 25.1
- `combine', 20.17, 20.31
- `command', 20.34
- `compact', 20.10
- `compare', 19.2, 20.5, 20.13, 20.14, 20.18, 20.18, 20.20, 20.28, 20.28,
20.31, 20.33
- `compare_big_int', 22.2
- `compare_num', 22.1
- `complex32', 29.1
- `complex32_elt', 29.1
- `complex64', 29.1
- `complex64_elt', 29.1
- `concat', 20.2, 20.8, 20.17, 20.31, 20.31, 20.31, 20.33
- `conj', 20.6
- `connect', 21.1, 24.5
- `contains', 20.31, 20.33
- `contains_from', 20.31, 20.33
- `contents', 20.3
- `control', 20.10
- `copy', 20.2, 20.12, 20.12, 20.21, 20.25, 20.26, 20.30, 20.31, 20.31, 20.33
- `cos', 19.2
- `cosh', 19.2
- `count', 20.32, 20.35
- `counters', 20.10
- `create', 20.2, 20.3, 20.12, 20.12, 20.25, 20.30, 20.31, 20.31, 20.33,
20.35, 20.35, 24.1, 24.2, 24.3, 29.1, 29.1, 29.1, 29.1
- `create_alarm', 20.10
- `create_image', 25.1
- `create_matrix', 20.2, 20.31
- `create_process', 21.1
- `create_process_env', 21.1
- `current', 20.1
- `current_dir_name', 20.8
- `current_point', 25.1
- `current_x', 25.1
- `current_y', 25.1
- `curveto', 25.1
- `cyan', 25.1
- `Dbm', 26.1
- `Dbm_error', 26.1
- `Digest', 20.7
- `Division_by_zero', 19.1
- `Dynlink', 27.1
- `data', 20.35
- `data_size', 20.19
- `decr', 19.2
- `decr_num', 22.1
- `default_available_units', 27.1
- `delay', 24.1
- `delete_alarm', 20.10
- `descr_of_in_channel', 21.1
- `descr_of_out_channel', 21.1
- `destroy', 28.1
- `diff', 20.28
- `dim', 29.1
- `dim1', 29.1, 29.1
- `dim2', 29.1, 29.1
- `dim3', 29.1
- `dims', 29.1
- `dir_handle', 21.1
- `dirname', 20.8
- `display_mode', 25.1
- `div', 20.6, 20.13, 20.14, 20.20
- `div_big_int', 22.2
- `div_num', 22.1
- `doc', 20.1
- `domain_of_sockaddr', 21.1
- `draw_arc', 25.1
- `draw_char', 25.1
- `draw_circle', 25.1
- `draw_ellipse', 25.1
- `draw_image', 25.1
- `draw_poly', 25.1
- `draw_poly_line', 25.1
- `draw_rect', 25.1
- `draw_segments', 25.1
- `draw_string', 25.1
- `dummy_pos', 20.16
- `dump_image', 25.1
- `dup', 21.1
- `dup2', 21.1
- `Empty', 20.25, 20.30
- `End_of_file', 19.1
- `Error', 20.32, 27.1
- `Event', 24.4
- `Exit', 19.2
- `elements', 20.28
- `elt', 20.28
- `empty', 20.18, 20.28, 20.32
- `end_of_input', 20.27
- `environment', 21.1
- `eprintf', 20.9, 20.24
- `epsilon_float', 19.2
- `eq_big_int', 22.2
- `eq_num', 22.1
- `equal', 20.12, 20.18, 20.28
- `err_formatter', 20.9
- `error', 21.1, 27.1
- `error_message', 21.1, 27.1
- `escaped', 20.5, 20.31, 20.33
- `establish_server', 21.1
- `event', 24.4, 25.1, 28.1
- `eventField', 28.1
- `eventInfo', 28.1
- `executable_name', 20.34
- `execv', 21.1, 24.5
- `execve', 21.1, 24.5
- `execvp', 21.1, 24.5
- `execvpe', 21.1
- `exists', 20.17, 20.28, 20.31
- `exists2', 20.17, 20.31
- `exit', 19.2, 24.1
- `exn', 19.1
- `exp', 19.2, 20.6
- `extern_flags', 20.19
- `Failure', 19.1, 20.32
- `Filename', 20.8
- `Format', 20.9
- `failwith', 19.2
- `fast_sort', 20.2, 20.17, 20.31, 20.31
- `fchmod', 21.1
- `fchown', 21.1
- `file', 20.7
- `file_descr', 21.1
- `file_exists', 20.34
- `file_kind', 21.1
- `file_perm', 21.1
- `fill', 20.2, 20.31, 20.31, 20.33, 20.35, 29.1, 29.1, 29.1, 29.1
- `fill_arc', 25.1
- `fill_circle', 25.1
- `fill_ellipse', 25.1
- `fill_poly', 25.1
- `fill_rect', 25.1
- `fillMode', 28.1
- `filter', 20.17, 20.28, 20.31
- `finalise', 20.10
- `finalise_release', 20.10
- `find', 20.12, 20.12, 20.17, 20.18, 20.31, 20.35, 26.1
- `find_all', 20.12, 20.12, 20.17, 20.31, 20.35
- `first_chars', 23.1
- `firstkey', 26.1
- `flatten', 20.17, 20.31
- `float', 19.1, 19.2, 20.26, 20.26
- `float_of_big_int', 22.2
- `float_of_bits', 20.13, 20.14
- `float_of_int', 19.2
- `float_of_num', 22.1
- `float_of_string', 19.2
- `float32', 29.1
- `float32_elt', 29.1
- `float64', 29.1
- `float64_elt', 29.1
- `floor', 19.2
- `floor_num', 22.1
- `flow_action', 21.1
- `flush', 19.2
- `flush_all', 19.2
- `flush_input', 20.16
- `flush_queue', 21.1
- `flush_str_formatter', 20.9
- `fold', 20.12, 20.12, 20.18, 20.25, 20.28, 20.35
- `fold_left', 20.2, 20.17, 20.31, 20.31
- `fold_left2', 20.17, 20.31
- `fold_right', 20.2, 20.17, 20.31, 20.31
- `fold_right2', 20.17, 20.31
- `for_all', 20.17, 20.28, 20.31
- `for_all2', 20.17, 20.31
- `force', 7.6, 20.15
- `force_newline', 20.9
- `force_val', 20.15
- `foreground', 25.1
- `fork', 21.1
- `format', 19.2
- `format_from_string', 20.27
- `format_of_string', 19.2
- `format4', 19.1, 19.2
- `formatter', 20.9
- `formatter_of_buffer', 20.9
- `formatter_of_out_channel', 20.9
- `formatter_tag_functions', 20.9
- `fortran_layout', 29.1, 29.1
- `fpclass', 19.2
- `fprintf', 20.9, 20.24
- `frexp', 19.2
- `from', 20.32
- `from_channel', 20.16, 20.19, 20.27
- `from_file', 20.27
- `from_file_bin', 20.27
- `from_function', 20.16, 20.27
- `from_string', 20.16, 20.19, 20.27
- `fscanf', 20.27
- `fst', 19.2
- `fstat', 21.1, 21.1
- `ftruncate', 21.1, 21.1
- `full_init', 20.26
- `full_major', 20.10
- `full_split', 23.1
- `Gc', 20.10
- `Genarray', 29.1
- `Genlex', 20.11
- `Graphic_failure', 25.1
- `Graphics', 25.1
- `gcd_big_int', 22.2
- `ge_big_int', 22.2
- `ge_num', 22.1
- `genarray_of_array1', 29.1
- `genarray_of_array2', 29.1
- `genarray_of_array3', 29.1
- `get', 20.2, 20.10, 20.31, 20.31, 20.33, 20.35, 29.1, 29.1, 29.1, 29.1
- `get_all_formatter_output_functions', 20.9
- `get_approx_printing', 22.3
- `get_copy', 20.35
- `get_ellipsis_text', 20.9
- `get_error_when_null_denominator', 22.3
- `get_floating_precision', 22.3
- `get_formatter_output_functions', 20.9
- `get_formatter_tag_functions', 20.9
- `get_image', 25.1
- `get_margin', 20.9
- `get_mark_tags', 20.9
- `get_max_boxes', 20.9
- `get_max_indent', 20.9
- `get_normalize_ratio', 22.3
- `get_normalize_ratio_when_printing', 22.3
- `get_print_tags', 20.9
- `get_state', 20.26
- `getaddrinfo', 21.1
- `getaddrinfo_option', 21.1
- `getcwd', 20.34, 21.1
- `getegid', 21.1
- `getenv', 20.34, 21.1
- `geteuid', 21.1
- `getgid', 21.1
- `getgrgid', 21.1
- `getgrnam', 21.1
- `getgroups', 21.1
- `gethostbyaddr', 21.1
- `gethostbyname', 21.1
- `gethostname', 21.1
- `getitimer', 21.1
- `getlogin', 21.1
- `getnameinfo', 21.1
- `getnameinfo_option', 21.1
- `getpeername', 21.1
- `getpid', 21.1
- `getppid', 21.1
- `getprotobyname', 21.1
- `getprotobynumber', 21.1
- `getpwnam', 21.1
- `getpwuid', 21.1
- `getservbyname', 21.1
- `getservbyport', 21.1
- `getsockname', 21.1
- `getsockopt', 21.1
- `getsockopt_float', 21.1
- `getsockopt_int', 21.1
- `getsockopt_optint', 21.1
- `gettimeofday', 21.1
- `getuid', 21.1
- `global_replace', 23.1
- `global_substitute', 23.1
- `gmtime', 21.1
- `green', 25.1
- `grid', 28.1
- `group_beginning', 23.1
- `group_end', 23.1
- `group_entry', 21.1
- `gt_big_int', 22.2
- `gt_num', 22.1
- `guard', 24.4
- `HashedType', 20.12
- `Hashtbl', 20.12
- `Help', 20.1
- `handle_unix_error', 21.1
- `hash', 20.12, 20.12
- `hash_param', 20.12
- `hd', 20.17, 20.31
- `header_size', 20.19
- `host_entry', 21.1
- `Int32', 20.13
- `Int64', 20.14
- `Invalid_argument', 19.1
- `i', 20.6
- `id', 20.21, 24.1
- `ifprintf', 20.9, 20.24
- `ignore', 19.2
- `image', 25.1
- `in_channel', 19.2
- `in_channel_length', 19.2, 19.2
- `in_channel_of_descr', 21.1
- `incr', 19.2
- `incr_num', 22.1
- `index', 20.31, 20.33
- `index_from', 20.31, 20.33
- `inet_addr', 21.1
- `inet_addr_any', 21.1
- `inet_addr_loopback', 21.1
- `inet_addr_of_string', 21.1
- `inet6_addr_any', 21.1
- `inet6_addr_loopback', 21.1
- `infinity', 19.2
- `init', 20.2, 20.26, 20.31, 27.1
- `input', 19.2, 20.7
- `input_binary_int', 19.2
- `input_byte', 19.2
- `input_char', 19.2
- `input_line', 19.2
- `input_value', 19.2
- `int', 19.1, 20.26, 20.26, 29.1
- `int_elt', 29.1
- `int_of_big_int', 22.2
- `int_of_char', 19.2
- `int_of_float', 19.2
- `int_of_num', 22.1
- `int_of_string', 19.2
- `int16_signed', 29.1
- `int16_signed_elt', 29.1
- `int16_unsigned', 29.1
- `int16_unsigned_elt', 29.1
- `int32', 7.1, 19.1, 20.26, 20.26, 29.1
- `int32_elt', 29.1
- `int64', 7.1, 19.1, 20.26, 20.26, 29.1
- `int64_elt', 29.1
- `int8_signed', 29.1
- `int8_signed_elt', 29.1
- `int8_unsigned', 29.1
- `int8_unsigned_elt', 29.1
- `integer_num', 22.1
- `inter', 20.28
- `interactive', 20.34
- `interval_timer', 21.1
- `interval_timer_status', 21.1
- `inv', 20.6
- `invalid_arg', 19.2
- `is_directory', 20.34
- `is_empty', 20.18, 20.25, 20.28, 20.30
- `is_implicit', 20.8
- `is_int_big_int', 22.2
- `is_integer_num', 22.1
- `is_relative', 20.8
- `isatty', 21.1
- `iter', 20.2, 20.12, 20.12, 20.17, 20.18, 20.25, 20.28, 20.30, 20.31, 20.31,
20.31, 20.32, 20.33, 20.35, 26.1
- `iter2', 20.17, 20.31
- `iteri', 20.2, 20.31
- `join', 24.1
- `junk', 20.32
- `kbprintf', 20.24
- `key', 20.1, 20.12, 20.18
- `key_pressed', 25.1
- `kfprintf', 20.9, 20.24
- `kill', 21.1, 24.1
- `kind', 29.1, 29.1, 29.1, 29.1, 29.1
- `kprintf', 20.9, 20.24
- `kscanf', 20.27
- `ksprintf', 20.9, 20.24
- `LargeFile', 19.2, 21.1
- `Lazy', 20.15
- `Lazy' (module), 7.6
- `Lexing', 20.16
- `List', 20.17, 20.31
- `land', 19.2
- `last_chars', 23.1
- `layout', 29.1, 29.1, 29.1, 29.1, 29.1
- `lazy_from_fun', 20.15
- `lazy_from_val', 20.15
- `lazy_is_val', 20.15
- `lazy_t', 19.1
- `ldexp', 19.2
- `le_big_int', 22.2
- `le_num', 22.1
- `length', 20.2, 20.3, 20.12, 20.12, 20.17, 20.25, 20.30, 20.31, 20.31,
20.31, 20.33, 20.35
- `lexbuf', 20.16
- `lexeme', 20.16
- `lexeme_char', 20.16
- `lexeme_end', 20.16
- `lexeme_end_p', 20.16
- `lexeme_start', 20.16
- `lexeme_start_p', 20.16
- `lineto', 25.1
- `link', 21.1
- `linking_error', 27.1
- `list', 19.1, 20.29
- `listen', 21.1
- `lnot', 19.2
- `loadfile', 27.1
- `loadfile_private', 27.1
- `localtime', 21.1
- `lock', 24.2
- `lock_command', 21.1
- `lockf', 21.1
- `log', 19.2, 20.6
- `log10', 19.2
- `logand', 20.13, 20.14, 20.20
- `lognot', 20.13, 20.14, 20.20
- `logor', 20.13, 20.14, 20.20
- `logxor', 20.13, 20.14, 20.20
- `lor', 19.2
- `lower_window', 28.1
- `lowercase', 20.5, 20.31, 20.33
- `lseek', 21.1, 21.1
- `lsl', 19.2
- `lsr', 19.2
- `lstat', 21.1, 21.1
- `lt_big_int', 22.2
- `lt_num', 22.1
- `lxor', 19.2
- `Make', 20.12, 20.18, 20.28, 20.35
- `Map', 20.18
- `Marshal', 20.19
- `Match_failure', 6.7.1, 6.7.1, 6.7.2, 19.1
- `Mutex', 24.2
- `magenta', 25.1
- `mainLoop', 28.1
- `major', 20.10
- `major_slice', 20.10
- `make', 20.2, 20.26, 20.31, 20.31, 20.33
- `make_formatter', 20.9
- `make_image', 25.1
- `make_lexer', 20.11
- `make_matrix', 20.2, 20.31
- `make_self_init', 20.26
- `map', 20.2, 20.17, 20.18, 20.31, 20.31
- `map_file', 29.1, 29.1, 29.1, 29.1
- `map2', 20.17, 20.31
- `mapi', 20.2, 20.18, 20.31
- `match_beginning', 23.1
- `match_end', 23.1
- `matched_group', 23.1
- `matched_string', 23.1
- `max', 19.2
- `max_array_length', 20.34
- `max_big_int', 22.2
- `max_elt', 20.28
- `max_float', 19.2
- `max_int', 19.2, 20.13, 20.14, 20.20
- `max_num', 22.1
- `max_string_length', 20.34
- `mem', 20.12, 20.12, 20.17, 20.18, 20.28, 20.31, 20.35
- `mem_assoc', 20.17, 20.31
- `mem_assq', 20.17, 20.31
- `memq', 20.17, 20.31
- `merge', 20.17, 20.29, 20.31, 20.35
- `min', 19.2
- `min_big_int', 22.2
- `min_elt', 20.28
- `min_float', 19.2
- `min_int', 19.2, 20.13, 20.14, 20.20
- `min_num', 22.1
- `minor', 20.10
- `minus_big_int', 22.2
- `minus_num', 22.1
- `minus_one', 20.13, 20.14, 20.20
- `mkdir', 21.1
- `mkfifo', 21.1
- `mktime', 21.1
- `mod', 19.2
- `mod_big_int', 22.2
- `mod_float', 19.2
- `mod_num', 22.1
- `modf', 19.2
- `modifier', 28.1
- `mouse_pos', 25.1
- `moveto', 25.1
- `msg_flag', 21.1
- `mul', 20.6, 20.13, 20.14, 20.20
- `mult_big_int', 22.2
- `mult_int_big_int', 22.2
- `mult_num', 22.1
- `Nativeint', 20.20
- `Not_found', 19.1
- `Num', 22.1
- `name_info', 21.1
- `name_of_input', 20.27
- `nan', 19.2
- `nat_of_num', 22.1
- `nativeint', 7.1, 19.1, 20.26, 20.26, 29.1
- `nativeint_elt', 29.1
- `neg', 20.6, 20.13, 20.14, 20.20
- `neg_infinity', 19.2
- `new_channel', 24.4
- `next', 20.32
- `nextkey', 26.1
- `nice', 21.1
- `norm', 20.6
- `norm2', 20.6
- `not', 19.2
- `npeek', 20.32
- `nth', 20.3, 20.17, 20.31
- `nth_dim', 29.1
- `num', 22.1
- `num_digits_big_int', 22.2
- `num_dims', 29.1
- `num_of_big_int', 22.1
- `num_of_int', 22.1
- `num_of_nat', 22.1
- `num_of_ratio', 22.1
- `num_of_string', 22.1
- `Oo', 20.21
- `OrderedType', 20.18, 20.28
- `Out_of_memory', 19.1
- `ocaml_version', 20.34
- `of_array', 29.1, 29.1, 29.1
- `of_channel', 20.32
- `of_float', 20.13, 20.14, 20.20
- `of_int', 20.13, 20.14, 20.20
- `of_int32', 20.14, 20.20
- `of_list', 20.2, 20.31, 20.32
- `of_nativeint', 20.14
- `of_string', 20.13, 20.14, 20.20, 20.32
- `one', 20.6, 20.13, 20.14, 20.20
- `open_box', 20.9
- `open_connection', 21.1, 24.5
- `open_flag', 19.2, 21.1, 26.1
- `open_graph', 25.1
- `open_hbox', 20.9
- `open_hovbox', 20.9
- `open_hvbox', 20.9
- `open_in', 19.2
- `open_in_bin', 19.2
- `open_in_gen', 19.2
- `open_out', 19.2
- `open_out_bin', 19.2
- `open_out_gen', 19.2
- `open_process', 21.1, 24.5
- `open_process_full', 21.1
- `open_process_in', 21.1, 24.5
- `open_process_out', 21.1, 24.5
- `open_tag', 20.9
- `open_tbox', 20.9
- `open_temp_file', 20.8
- `open_vbox', 20.9
- `opendbm', 26.1
- `opendir', 21.1
- `openfile', 21.1
- `openTk', 28.1
- `option', 19.1
- `or', 19.2
- `os_type', 20.34
- `out_channel', 19.2
- `out_channel_length', 19.2, 19.2
- `out_channel_of_descr', 21.1
- `output', 19.2, 20.7
- `output_binary_int', 19.2
- `output_buffer', 20.3
- `output_byte', 19.2
- `output_char', 19.2
- `output_string', 19.2
- `output_value', 19.2
- `over_max_boxes', 20.9
- `Parse_error', 20.22
- `Parsing', 20.22
- `Pervasives', 19.2
- `Printexc', 20.23
- `Printf', 20.24
- `pack', 28.1
- `parent_dir_name', 20.8
- `parse', 20.1
- `parse_argv', 20.1
- `partition', 20.17, 20.28, 20.31
- `passwd_entry', 21.1
- `pause', 21.1
- `peek', 20.25, 20.32
- `pipe', 21.1, 24.5
- `pixels', 28.1
- `place', 28.1
- `plot', 25.1
- `plots', 25.1
- `point_color', 25.1
- `polar', 20.6
- `poll', 24.4
- `pop', 20.25, 20.30
- `pos_in', 19.2, 19.2
- `pos_out', 19.2, 19.2
- `position', 20.16
- `pow', 20.6
- `power_big_int_positive_big_int', 22.2
- `power_big_int_positive_int', 22.2
- `power_int_positive_big_int', 22.2
- `power_int_positive_int', 22.2
- `power_num', 22.1
- `pp_close_box', 20.9
- `pp_close_tag', 20.9
- `pp_close_tbox', 20.9
- `pp_force_newline', 20.9
- `pp_get_all_formatter_output_functions', 20.9
- `pp_get_ellipsis_text', 20.9
- `pp_get_formatter_output_functions', 20.9
- `pp_get_formatter_tag_functions', 20.9
- `pp_get_margin', 20.9
- `pp_get_mark_tags', 20.9
- `pp_get_max_boxes', 20.9
- `pp_get_max_indent', 20.9
- `pp_get_print_tags', 20.9
- `pp_open_box', 20.9
- `pp_open_hbox', 20.9
- `pp_open_hovbox', 20.9
- `pp_open_hvbox', 20.9
- `pp_open_tag', 20.9
- `pp_open_tbox', 20.9
- `pp_open_vbox', 20.9
- `pp_over_max_boxes', 20.9
- `pp_print_as', 20.9
- `pp_print_bool', 20.9
- `pp_print_break', 20.9
- `pp_print_char', 20.9
- `pp_print_cut', 20.9
- `pp_print_float', 20.9
- `pp_print_flush', 20.9
- `pp_print_if_newline', 20.9
- `pp_print_int', 20.9
- `pp_print_newline', 20.9
- `pp_print_space', 20.9
- `pp_print_string', 20.9
- `pp_print_tab', 20.9
- `pp_print_tbreak', 20.9
- `pp_set_all_formatter_output_functions', 20.9
- `pp_set_ellipsis_text', 20.9
- `pp_set_formatter_out_channel', 20.9
- `pp_set_formatter_output_functions', 20.9
- `pp_set_formatter_tag_functions', 20.9
- `pp_set_margin', 20.9
- `pp_set_mark_tags', 20.9
- `pp_set_max_boxes', 20.9
- `pp_set_max_indent', 20.9
- `pp_set_print_tags', 20.9
- `pp_set_tab', 20.9
- `pp_set_tags', 20.9
- `pred', 19.2, 20.13, 20.14, 20.20
- `pred_big_int', 22.2
- `pred_num', 22.1
- `prerr_char', 19.2
- `prerr_endline', 19.2
- `prerr_float', 19.2
- `prerr_int', 19.2
- `prerr_newline', 19.2
- `prerr_string', 19.2
- `print', 20.23
- `print_as', 20.9
- `print_bool', 20.9
- `print_break', 20.9
- `print_char', 19.2, 20.9
- `print_cut', 20.9
- `print_endline', 19.2
- `print_float', 19.2, 20.9
- `print_flush', 20.9
- `print_if_newline', 20.9
- `print_int', 19.2, 20.9
- `print_newline', 19.2, 20.9
- `print_space', 20.9
- `print_stat', 20.10
- `print_string', 19.2, 20.9
- `print_tab', 20.9
- `print_tbreak', 20.9
- `printf', 20.9, 20.24
- `process_status', 21.1
- `process_times', 21.1
- `prohibit', 27.1
- `protocol_entry', 21.1
- `push', 20.25, 20.30
- `putenv', 21.1
- `Queue', 20.25
- `quick_stat', 20.10
- `quo_num', 22.1
- `quomod_big_int', 22.2
- `quote', 20.8, 23.1
- `Random', 20.26
- `raise', 19.2
- `raise_window', 28.1
- `ratio_of_num', 22.1
- `rcontains_from', 20.31, 20.33
- `read', 21.1, 24.5
- `read_float', 19.2
- `read_int', 19.2
- `read_key', 25.1
- `read_line', 19.2
- `readdir', 20.34, 21.1
- `readlink', 21.1
- `really_input', 19.2
- `receive', 24.4
- `recv', 21.1, 24.5
- `recvfrom', 21.1, 24.5
- `red', 25.1
- `ref', 19.2, 19.2
- `regexp', 23.1, 23.1
- `regexp_case_fold', 23.1
- `regexp_string', 23.1
- `regexp_string_case_fold', 23.1
- `register', 20.4
- `register_exception', 20.4
- `rem', 20.13, 20.14, 20.20
- `remember_mode', 25.1
- `remove', 20.12, 20.12, 20.18, 20.28, 20.34, 20.35, 26.1
- `remove_assoc', 20.17, 20.31
- `remove_assq', 20.17, 20.31
- `rename', 20.34, 21.1
- `replace', 20.12, 20.12, 26.1
- `replace_first', 23.1
- `replace_matched', 23.1
- `reset', 20.3
- `reshape', 29.1
- `reshape_1', 29.1
- `reshape_2', 29.1
- `reshape_3', 29.1
- `resize_window', 25.1
- `rev', 20.17, 20.31
- `rev_append', 20.17, 20.31
- `rev_map', 20.17, 20.31
- `rev_map2', 20.17, 20.31
- `rewinddir', 21.1
- `rgb', 25.1
- `rhs_end', 20.22
- `rhs_end_pos', 20.22
- `rhs_start', 20.22
- `rhs_start_pos', 20.22
- `rindex', 20.31, 20.33
- `rindex_from', 20.31, 20.33
- `rlineto', 25.1
- `rmdir', 21.1
- `rmoveto', 25.1
- `round_num', 22.1
- `S', 20.12, 20.18, 20.28, 20.35
- `Scan_failure', 20.27
- `Scanf', 20.27
- `Scanning', 20.27
- `Set', 20.28
- `Sort', 20.29
- `Stack', 20.30
- `Stack_overflow', 19.1
- `State', 20.26
- `StdLabels', 20.31
- `Str', 23.1
- `Stream', 20.32
- `String', 20.31, 20.33
- `Sys', 20.34
- `Sys_blocked_io', 19.1
- `Sys_error', 19.1
- `scanbuf', 20.27
- `scanf', 20.27
- `scanner', 20.27
- `search_backward', 23.1
- `search_forward', 23.1
- `seek_command', 21.1
- `seek_in', 19.2, 19.2
- `seek_out', 19.2, 19.2
- `select', 21.1, 24.1, 24.4, 24.5
- `self', 24.1
- `self_init', 20.26
- `send', 21.1, 24.4, 24.5
- `sendto', 21.1, 24.5
- `service_entry', 21.1
- `set', 20.2, 20.10, 20.31, 20.31, 20.33, 20.35, 29.1, 29.1, 29.1, 29.1
- `set_all_formatter_output_functions', 20.9
- `set_approx_printing', 22.3
- `set_binary_mode_in', 19.2
- `set_binary_mode_out', 19.2
- `set_close_on_exec', 21.1
- `set_color', 25.1
- `set_ellipsis_text', 20.9
- `set_error_when_null_denominator', 22.3
- `set_floating_precision', 22.3
- `set_font', 25.1
- `set_formatter_out_channel', 20.9
- `set_formatter_output_functions', 20.9
- `set_formatter_tag_functions', 20.9
- `set_line_width', 25.1
- `set_margin', 20.9
- `set_mark_tags', 20.9
- `set_max_boxes', 20.9
- `set_max_indent', 20.9
- `set_nonblock', 21.1
- `set_normalize_ratio', 22.3
- `set_normalize_ratio_when_printing', 22.3
- `set_print_tags', 20.9
- `set_signal', 20.34
- `set_state', 20.26
- `set_tab', 20.9
- `set_tags', 20.9
- `set_text_size', 25.1
- `set_window_title', 25.1
- `setattr_when', 21.1
- `setgid', 21.1
- `setitimer', 21.1
- `setsid', 21.1
- `setsockopt', 21.1
- `setsockopt_float', 21.1
- `setsockopt_int', 21.1
- `setsockopt_optint', 21.1
- `setuid', 21.1
- `shift_left', 20.13, 20.14, 20.20
- `shift_right', 20.13, 20.14, 20.20
- `shift_right_logical', 20.13, 20.14, 20.20
- `shutdown', 21.1
- `shutdown_command', 21.1
- `shutdown_connection', 21.1
- `side', 28.1
- `sigabrt', 20.34
- `sigalrm', 20.34
- `sigchld', 20.34
- `sigcont', 20.34
- `sigfpe', 20.34
- `sighup', 20.34
- `sigill', 20.34
- `sigint', 20.34
- `sigkill', 20.34
- `sigmask', 24.1
- `sign_big_int', 22.2
- `sign_num', 22.1
- `signal', 20.34, 24.3
- `signal_behavior', 20.34
- `sigpending', 21.1
- `sigpipe', 20.34
- `sigprocmask', 21.1
- `sigprocmask_command', 21.1
- `sigprof', 20.34
- `sigquit', 20.34
- `sigsegv', 20.34
- `sigstop', 20.34
- `sigsuspend', 21.1
- `sigterm', 20.34
- `sigtstp', 20.34
- `sigttin', 20.34
- `sigttou', 20.34
- `sigusr1', 20.34
- `sigusr2', 20.34
- `sigvtalrm', 20.34
- `sin', 19.2
- `single_write', 21.1
- `singleton', 20.28
- `sinh', 19.2
- `size', 20.20
- `size_x', 25.1
- `size_y', 25.1
- `sleep', 21.1, 24.5
- `slice_left', 29.1, 29.1
- `slice_left_1', 29.1
- `slice_left_2', 29.1
- `slice_right', 29.1, 29.1
- `slice_right_1', 29.1
- `slice_right_2', 29.1
- `snd', 19.2
- `sockaddr', 21.1
- `socket', 21.1, 24.5
- `socket_bool_option', 21.1
- `socket_domain', 21.1
- `socket_float_option', 21.1
- `socket_int_option', 21.1
- `socket_optint_option', 21.1
- `socket_type', 21.1
- `socketpair', 21.1
- `sort', 20.2, 20.17, 20.31, 20.31
- `sound', 25.1
- `spec', 20.1
- `split', 20.17, 20.28, 20.31, 23.1
- `split_delim', 23.1
- `split_result', 23.1
- `sprintf', 20.9, 20.24
- `sqrt', 19.2, 20.6
- `sqrt_big_int', 22.2
- `square_big_int', 22.2
- `square_num', 22.1
- `sscanf', 20.27
- `sscanf_format', 20.27
- `stable_sort', 20.2, 20.17, 20.31, 20.31
- `stat', 20.10, 20.10, 21.1, 21.1
- `stats', 20.35, 21.1, 21.1
- `status', 25.1
- `std_formatter', 20.9
- `stdbuf', 20.9
- `stderr', 19.2, 21.1
- `stdib', 20.27
- `stdin', 19.2, 21.1
- `stdout', 19.2, 21.1
- `str_formatter', 20.9
- `string', 19.1, 20.7
- `string_after', 23.1
- `string_before', 23.1
- `string_match', 23.1
- `string_of_big_int', 22.2
- `string_of_bool', 19.2
- `string_of_float', 19.2
- `string_of_format', 19.2
- `string_of_inet_addr', 21.1
- `string_of_int', 19.2
- `string_of_num', 22.1
- `string_partial_match', 23.1
- `sub', 20.2, 20.3, 20.6, 20.13, 20.14, 20.20, 20.31, 20.31, 20.33, 29.1
- `sub_big_int', 22.2
- `sub_left', 29.1, 29.1, 29.1
- `sub_num', 22.1
- `sub_right', 29.1, 29.1, 29.1
- `subset', 20.28
- `substitute_first', 23.1
- `substring', 20.7
- `succ', 19.2, 20.13, 20.14, 20.20
- `succ_big_int', 22.2
- `succ_num', 22.1
- `symbol_end', 20.22
- `symbol_end_pos', 20.22
- `symbol_start', 20.22
- `symbol_start_pos', 20.22
- `symlink', 21.1
- `sync', 24.4
- `synchronize', 25.1
- `system', 21.1, 24.5
- `Thread', 24.1
- `ThreadUnix', 24.5
- `Tk', 28.1
- `t', 20.3, 20.5, 20.6, 20.7, 20.12, 20.12, 20.12, 20.13, 20.14, 20.15,
20.18, 20.18, 20.20, 20.25, 20.26, 20.28, 20.28, 20.30, 20.31, 20.32, 20.33,
20.35, 20.35, 24.1, 24.2, 24.3, 26.1, 29.1, 29.1, 29.1, 29.1
- `tag', 20.9
- `take', 20.25
- `tan', 19.2
- `tanh', 19.2
- `tcdrain', 21.1
- `tcflow', 21.1
- `tcflush', 21.1
- `tcgetattr', 21.1
- `tcsendbreak', 21.1
- `tcsetattr', 21.1
- `temp_dir_name', 20.8
- `temp_file', 20.8
- `terminal_io', 21.1
- `text_size', 25.1
- `time', 20.34, 21.1
- `timed_read', 24.5
- `timed_write', 24.5
- `times', 21.1
- `tl', 20.17, 20.31
- `tm', 21.1
- `to_buffer', 20.19
- `to_channel', 20.19
- `to_float', 20.13, 20.14, 20.20
- `to_hex', 20.7
- `to_int', 20.13, 20.14, 20.20
- `to_int32', 20.14, 20.20
- `to_list', 20.2, 20.31
- `to_nativeint', 20.14
- `to_string', 20.13, 20.14, 20.19, 20.20, 20.23
- `token', 20.11
- `top', 20.25, 20.30
- `total_size', 20.19
- `transfer', 20.25
- `transp', 25.1
- `truncate', 19.2, 21.1, 21.1
- `try_lock', 24.2
- `Undefined', 20.15
- `Undefined_recursive_module', 19.1
- `Unix', 21.1
- `Unix_error', 21.1
- `UnixLabels' (module), 21.2
- `umask', 21.1
- `uncapitalize', 20.31, 20.33
- `union', 20.28
- `unit', 19.1
- `unit_big_int', 22.2
- `units', 28.1
- `unlink', 21.1
- `unlock', 24.2
- `unsafe_blit', 20.31
- `unsafe_fill', 20.31
- `unsafe_get', 20.31, 20.31
- `unsafe_set', 20.31, 20.31
- `update', 28.1
- `uppercase', 20.5, 20.31, 20.33
- `usage', 20.1
- `usage_msg', 20.1
- `utimes', 21.1
- `Weak', 20.35
- `wait', 21.1, 24.3, 24.5
- `wait_flag', 21.1
- `wait_next_event', 25.1
- `wait_pid', 24.1
- `wait_read', 24.1
- `wait_signal', 24.1
- `wait_timed_read', 24.1
- `wait_timed_write', 24.1
- `wait_write', 24.1
- `waitpid', 21.1, 24.5
- `white', 25.1
- `word_size', 20.34
- `wrap', 24.4
- `wrap_abort', 24.4
- `write', 21.1, 24.5
- `yellow', 25.1
- `yield', 24.1
- `zero', 20.6, 20.13, 20.14, 20.20
- `zero_big_int', 22.2
Chapter 31 Index of keywords
*******************************
- and, see let, type, class, 6.9.2, 6.9.3, 6.9.4, 6.9.5
- as, 6.4, 6.4, 6.4, 6.6, 6.6, 6.6, 6.9.2, 6.9.2
- assert, 7.5
- begin, 6.7, 6.7.1
- class, 6.9.3, 6.9.4, 6.9.5, 6.10, 6.10.2, 6.10.2, 6.11, 6.11.2, 6.11.2
- constraint, 6.8.1, 6.8.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2
- do, see while, for
- done, see while, for
- downto, see for
- else, see if
- end, 6.7, 6.7.1, 6.9.1, 6.9.2, 6.10, 6.10.2, 6.11, 6.11.2
- exception, 6.8.2, 6.10, 6.10.2, 6.11, 6.11.2
- external, 6.10, 6.10.2, 6.11, 6.11.2
- false, 6.3
- for, 6.7, 6.7.2
- fun, 6.7, 6.7, 6.7.1, 6.9.2
- function, 6.7, 6.7, 6.7.1
- functor, 6.10, 6.10.3, 6.11, 6.11.3
- if, 6.7, 6.7, 6.7.2
- in, see let, 6.9.2
- include, 6.10, 6.10.2, 6.11, 6.11.2
- inherit, 6.9.1, 6.9.1, 6.9.2, 6.9.2
- initializer, 6.9.2, 6.9.2
- lazy, 7.6
- let, 6.7, 6.7, 6.7.1, 6.9.2, 6.11, 6.11.2, 7.7
- match, 6.7, 6.7, 6.7.2
- method, 6.9.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.9.2
- module, 6.10, 6.10.2, 6.10.2, 6.11, 6.11.2, 6.11.2, 7.7, 7.9
- mutable, 6.8.1, 6.8.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.9.2
- new, 6.7, 6.7.5
- object, 6.7, 6.7.5, 6.9.1, 6.9.2
- of, see type, exception
- open, 6.10, 6.10.2, 6.11, 6.11.2
- or, 6.7, 6.7, 6.7.2
- private, 6.9.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.9.2, 7.8, 7.10
- rec, see let, 6.9.2, 7.9
- sig, 6.10, 6.10.2
- struct, 6.11, 6.11.2
- then, see if
- to, see for
- true, 6.3
- try, 6.7, 6.7, 6.7.2
- type, 6.8.1, 6.9.5, 6.10, 6.10.2, 6.10.2, 6.10.2, 6.11, 6.11.2, 6.11.2,
6.11.2
- val, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.9.2, 6.10, 6.10.2
- virtual, 6.9.1, 6.9.1, 6.9.1, 6.9.2, 6.9.2, 6.9.2, 6.9.3, 6.9.3, 6.9.4,
6.9.5
- when, 6.7, 6.7.1
- while, 6.7.2
- with, see match, try, 6.10, 6.10.4
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