package prelude

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include module type of struct include Stdlib end

Exceptions

val raise : exn -> 'a

Raise the given exception value

val raise_notrace : exn -> 'a

A faster version raise which does not record the backtrace.

  • since 4.02
exception Exit

The Exit exception is not raised by any library function. It is provided for use in your programs.

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. The string gives some information to the programmer. As a general rule, this exception should not be caught, it denotes a programming error and the code should be modified not to trigger it.

exception Failure of string

Exception raised by library functions to signal that they are undefined on the given arguments. The string is meant to give some information to the programmer; you must not pattern match on the string literal because it may change in future versions (use Failure _ instead).

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. (Not reliable for allocations on the minor heap.)

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.

Before 4.10, it was not fully implemented by the native-code compiler.

exception Sys_error of string

Exception raised by the input/output functions to report an operating system error. The string is meant to give some information to the programmer; you must not pattern match on the string literal because it may change in future versions (use Sys_error _ instead).

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 integer division and remainder operations when their second argument is zero.

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. The arguments are the location of the definition in the source code (file name, line number, column number).

Comparisons

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. Right-associative operator, see Ocaml_operators for more information.

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. Right-associative operator, see Ocaml_operators for more information.

Debugging

val __LOC__ : string

__LOC__ returns the location at which this expression appears in the file currently being parsed by the compiler, with the standard error format of OCaml: "File %S, line %d, characters %d-%d".

  • since 4.02
val __FILE__ : string

__FILE__ returns the name of the file currently being parsed by the compiler.

  • since 4.02
val __LINE__ : int

__LINE__ returns the line number at which this expression appears in the file currently being parsed by the compiler.

  • since 4.02
val __MODULE__ : string

__MODULE__ returns the module name of the file being parsed by the compiler.

  • since 4.02
val __POS__ : string * int * int * int

__POS__ returns a tuple (file,lnum,cnum,enum), corresponding to the location at which this expression appears in the file currently being parsed by the compiler. file is the current filename, lnum the line number, cnum the character position in the line and enum the last character position in the line.

  • since 4.02
val __FUNCTION__ : string

__FUNCTION__ returns the name of the current function or method, including any enclosing modules or classes.

  • since 4.12
val __LOC_OF__ : 'a -> string * 'a

__LOC_OF__ expr returns a pair (loc, expr) where loc is the location of expr in the file currently being parsed by the compiler, with the standard error format of OCaml: "File %S, line %d, characters %d-%d".

  • since 4.02
val __LINE_OF__ : 'a -> int * 'a

__LINE_OF__ expr returns a pair (line, expr), where line is the line number at which the expression expr appears in the file currently being parsed by the compiler.

  • since 4.02
val __POS_OF__ : 'a -> (string * int * int * int) * 'a

__POS_OF__ expr returns a pair (loc,expr), where loc is a tuple (file,lnum,cnum,enum) corresponding to the location at which the expression expr appears in the file currently being parsed by the compiler. file is the current filename, lnum the line number, cnum the character position in the line and enum the last character position in the line.

  • since 4.02

Composition operators

val (|>) : 'a -> ('a -> 'b) -> 'b

Reverse-application operator: x |> f |> g is exactly equivalent to g (f (x)). Left-associative operator, see Ocaml_operators for more information.

  • since 4.01
val (@@) : ('a -> 'b) -> 'a -> 'b

Application operator: g @@ f @@ x is exactly equivalent to g (f (x)). Right-associative operator, see Ocaml_operators for more information.

  • since 4.01

Integer arithmetic

Integers are Sys.int_size bits wide. All operations are taken modulo 2Sys.int_size. They do not fail on overflow.

val (~-) : int -> int

Unary negation. You can also write - e instead of ~- e. Unary operator, see Ocaml_operators for more information.

val (~+) : int -> int

Unary addition. You can also write + e instead of ~+ e. Unary operator, see Ocaml_operators for more information.

  • since 3.12
val succ : int -> int

succ x is x + 1.

val pred : int -> int

pred x is x - 1.

val (+) : int -> int -> int

Integer addition. Left-associative operator, see Ocaml_operators for more information.

val (-) : int -> int -> int

Integer subtraction. Left-associative operator, , see Ocaml_operators for more information.

val (*) : int -> int -> int

Integer multiplication. Left-associative operator, see Ocaml_operators for more information.

val (/) : int -> int -> int

Integer division. 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). Left-associative operator, see Ocaml_operators for more information.

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. Note that x mod y is negative only if x < 0. Left-associative operator, see Ocaml_operators for more information.

val abs : int -> int

abs x is the absolute value of x. On min_int this is min_int itself and thus remains negative.

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. Left-associative operator, see Ocaml_operators for more information.

val (lor) : int -> int -> int

Bitwise logical or. Left-associative operator, see Ocaml_operators for more information.

val (lxor) : int -> int -> int

Bitwise logical exclusive or. Left-associative operator, see Ocaml_operators for more information.

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 > Sys.int_size. Right-associative operator, see Ocaml_operators for more information.

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 > Sys.int_size. Right-associative operator, see Ocaml_operators for more information.

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 > Sys.int_size. Right-associative operator, see Ocaml_operators for more information.

Floating-point arithmetic

OCaml'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, basic arithmetic operations (+., -., *., /.) with nan as an argument return nan, ...

val (~-.) : float -> float

Unary negation. You can also write -. e instead of ~-. e. Unary operator, see Ocaml_operators for more information.

val (~+.) : float -> float

Unary addition. You can also write +. e instead of ~+. e. Unary operator, see Ocaml_operators for more information.

  • since 3.12
val (+.) : float -> float -> float

Floating-point addition. Left-associative operator, see Ocaml_operators for more information.

val (-.) : float -> float -> float

Floating-point subtraction. Left-associative operator, see Ocaml_operators for more information.

val (*.) : float -> float -> float

Floating-point multiplication. Left-associative operator, see Ocaml_operators for more information.

val (/.) : float -> float -> float

Floating-point division. Left-associative operator, see Ocaml_operators for more information.

val (**) : float -> float -> float

Exponentiation. Right-associative operator, see Ocaml_operators for more information.

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 expm1 : float -> float

expm1 x computes exp x -. 1.0, giving numerically-accurate results even if x is close to 0.0.

  • since 3.12
val log1p : float -> float

log1p x computes log(1.0 +. x) (natural logarithm), giving numerically-accurate results even if x is close to 0.0.

  • since 3.12
val cos : float -> float

Cosine. Argument is in radians.

val sin : float -> float

Sine. Argument is in radians.

val tan : float -> float

Tangent. Argument is in radians.

val acos : float -> float

Arc cosine. The argument must fall within the range [-1.0, 1.0]. Result is in radians and is between 0.0 and pi.

val asin : float -> float

Arc sine. The argument must fall within the range [-1.0, 1.0]. Result is in radians and is between -pi/2 and pi/2.

val atan : float -> float

Arc tangent. Result is in radians and is between -pi/2 and pi/2.

val atan2 : float -> float -> float

atan2 y x returns the arc tangent of y /. x. The signs of x and y are used to determine the quadrant of the result. Result is in radians and is between -pi and pi.

val hypot : float -> float -> float

hypot x y returns sqrt(x *. x + y *. y), that is, the length of the hypotenuse of a right-angled triangle with sides of length x and y, or, equivalently, the distance of the point (x,y) to origin. If one of x or y is infinite, returns infinity even if the other is nan.

  • since 4.00
val cosh : float -> float

Hyperbolic cosine. Argument is in radians.

val sinh : float -> float

Hyperbolic sine. Argument is in radians.

val tanh : float -> float

Hyperbolic tangent. Argument is in radians.

val acosh : float -> float

Hyperbolic arc cosine. The argument must fall within the range [1.0, inf]. Result is in radians and is between 0.0 and inf.

  • since 4.13
val asinh : float -> float

Hyperbolic arc sine. The argument and result range over the entire real line. Result is in radians.

  • since 4.13
val atanh : float -> float

Hyperbolic arc tangent. The argument must fall within the range [-1.0, 1.0]. Result is in radians and ranges over the entire real line.

  • since 4.13
val ceil : float -> float

Round above to an integer value. ceil f returns the least integer value greater than or equal to f. The result is returned as a float.

val floor : float -> float

Round below to an integer value. floor f returns the greatest integer value less than or equal to f. The result is returned as a float.

val abs_float : float -> float

abs_float f returns the absolute value of f.

val copysign : float -> float -> float

copysign x y returns a float whose absolute value is that of x and whose sign is that of y. If x is nan, returns nan. If y is nan, returns either x or -. x, but it is not specified which.

  • since 4.00
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 Stdlib.float_of_int.

val float_of_int : int -> float

Convert an integer to floating-point.

val truncate : float -> int

Same as Stdlib.int_of_float.

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, unless otherwise specified in IEEE 754 standard. As for floating-point comparisons, =, <, <=, > and >= return false and <> returns true if one or both of their arguments is nan.

nan is a quiet NaN since 5.1; it was a signaling NaN before.

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 difference between 1.0 and the smallest exactly representable floating-point number greater than 1.0.

type fpclass = fpclass =
  1. | FP_normal
    (*

    Normal number, none of the below

    *)
  2. | FP_subnormal
    (*

    Number very close to 0.0, has reduced precision

    *)
  3. | FP_zero
    (*

    Number is 0.0 or -0.0

    *)
  4. | FP_infinite
    (*

    Number is positive or negative infinity

    *)
  5. | FP_nan
    (*

    Not a number: result of an undefined operation

    *)

The five classes of floating-point numbers, as determined by the Stdlib.classify_float 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.

Character operations

More character operations are provided in module Char.

val int_of_char : char -> int

Return the ASCII code of the argument.

Unit operations

String conversion functions

val string_of_bool : bool -> string

Return the string representation of a boolean. As the returned values may be shared, the user should not modify them directly.

val string_of_int : int -> string

Return the string representation of an integer, in decimal.

val string_of_float : float -> string

Return a string representation of a floating-point number.

This conversion can involve a loss of precision. For greater control over the manner in which the number is printed, see Printf.

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.

val (@) : 'a list -> 'a list -> 'a list

l0 @ l1 appends l1 to l0. Same function as List.append. Right-associative operator, see Ocaml_operators for more information.

  • since 5.1 this function is tail-recursive.

Input/output

Note: all input/output functions can raise Sys_error when the system calls they invoke fail.

type in_channel = in_channel

The type of input channel.

type out_channel = 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 output for the process.

Output functions on standard output

Output functions on standard error

Input functions on standard input

General output functions

type open_flag = open_flag =
  1. | Open_rdonly
    (*

    open for reading.

    *)
  2. | Open_wronly
    (*

    open for writing.

    *)
  3. | Open_append
    (*

    open for appending: always write at end of file.

    *)
  4. | Open_creat
    (*

    create the file if it does not exist.

    *)
  5. | Open_trunc
    (*

    empty the file if it already exists.

    *)
  6. | Open_excl
    (*

    fail if Open_creat and the file already exists.

    *)
  7. | Open_binary
    (*

    open in binary mode (no conversion).

    *)
  8. | Open_text
    (*

    open in text mode (may perform conversions).

    *)
  9. | Open_nonblock
    (*

    open in non-blocking mode.

    *)

Opening modes for Stdlib.open_out_gen and Stdlib.open_in_gen.

General input functions

val pos_in : in_channel -> int

Return the current reading position for the given channel. For files opened in text mode under Windows, the returned position is approximate (owing to end-of-line conversion); in particular, saving the current position with pos_in, then going back to this position using seek_in will not work. For this programming idiom to work reliably and portably, the file must be opened in binary mode.

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.

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 = LargeFile

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 = 'a ref = {
  1. 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. Unary operator, see Ocaml_operators for more information.

val (:=) : 'a ref -> 'a -> unit

r := a stores the value of a in reference r. Equivalent to fun r v -> r.contents <- v. Right-associative operator, see Ocaml_operators for more information.

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.

Result type

type ('a, 'b) result = ('a, 'b) result =
  1. | Ok of 'a
  2. | Error of 'b
  • since 4.03

Operations on format strings

Format strings are character strings with special lexical conventions that defines the functionality of formatted input/output functions. Format strings are used to read data with formatted input functions from module Scanf and to print data with formatted output functions from modules Printf and Format.

Format strings are made of three kinds of entities:

  • conversions specifications, introduced by the special character '%' followed by one or more characters specifying what kind of argument to read or print,
  • formatting indications, introduced by the special character '@' followed by one or more characters specifying how to read or print the argument,
  • plain characters that are regular characters with usual lexical conventions. Plain characters specify string literals to be read in the input or printed in the output.

There is an additional lexical rule to escape the special characters '%' and '@' in format strings: if a special character follows a '%' character, it is treated as a plain character. In other words, "%%" is considered as a plain '%' and "%@" as a plain '@'.

For more information about conversion specifications and formatting indications available, read the documentation of modules Scanf, Printf and Format.

Format strings have a general and highly polymorphic type ('a, 'b, 'c, 'd, 'e, 'f) format6. The two simplified types, format and format4 below are included for backward compatibility with earlier releases of OCaml.

The meaning of format string type parameters is as follows:

  • 'a is the type of the parameters of the format for formatted output functions (printf-style functions); 'a is the type of the values read by the format for formatted input functions (scanf-style functions).
  • 'b is the type of input source for formatted input functions and the type of output target for formatted output functions. For printf-style functions from module Printf, 'b is typically out_channel; for printf-style functions from module Format, 'b is typically Format.formatter; for scanf-style functions from module Scanf, 'b is typically Scanf.Scanning.in_channel.

Type argument 'b is also the type of the first argument given to user's defined printing functions for %a and %t conversions, and user's defined reading functions for %r conversion.

  • 'c is the type of the result of the %a and %t printing functions, and also the type of the argument transmitted to the first argument of kprintf-style functions or to the kscanf-style functions.
  • 'd is the type of parameters for the scanf-style functions.
  • 'e is the type of the receiver function for the scanf-style functions.
  • 'f is the final result type of a formatted input/output function invocation: for the printf-style functions, it is typically unit; for the scanf-style functions, it is typically the result type of the receiver function.
type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) CamlinternalFormatBasics.format6
type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
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. Note: format_of_string can not convert a string argument that is not a literal. If you need this functionality, use the more general Scanf.format_from_string function.

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 format strings f1 and f2. The result is a format string that behaves as the concatenation of format strings f1 and f2: in case of formatted output, it accepts arguments from f1, then arguments from f2; in case of formatted input, it returns results from f1, then results from f2. Right-associative operator, see Ocaml_operators for more information.

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. The callbacks registered with Domain.at_exit are called followed by those registered with Stdlib.at_exit.

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 does any of the following:

  • executes Stdlib.exit
  • terminates, either normally or because of an uncaught exception
  • executes the C function caml_shutdown. The functions are called in 'last in, first out' order: the function most recently added with at_exit is called first.

Standard library modules

module Array = Array
module Atomic = Atomic
module Bigarray = Bigarray
module Bool = Bool
module Buffer = Buffer
module Bytes = Bytes
module Callback = Callback
module Char = Char
module Complex = Complex
module Condition = Condition
module Digest = Digest
module Domain = Domain
module Effect = Effect
module Either = Either
module Ephemeron = Ephemeron
module Float = Float
module Fun = Fun
module Gc = Gc
module Hashtbl = Hashtbl
module In_channel = In_channel
module Int = Int
module Int32 = Int32
module Int64 = Int64
module Lazy = Lazy
module Lexing = Lexing
module List = List
module Map = Map
module Marshal = Marshal
module Mutex = Mutex
module Nativeint = Nativeint
module Obj = Obj
module Oo = Oo
module Option = Option
module Out_channel = Out_channel
module Printexc = Printexc
module Queue = Queue
module Random = Random
module Result = Result
module Scanf = Scanf
module Semaphore = Semaphore
module Seq = Seq
module Set = Set
module Stack = Stack
module String = String
module Type = Type
module Uchar = Uchar
module Unit = Unit
module Weak = Weak
module Empty : sig ... end
module Printf = Empty
module Fmt : sig ... end
module Format = Empty
module Arg = Empty
module Cmdliner = Cmdliner
module ArrayLabels = Empty
module BytesLabels = Empty
module ListLabels = Empty
module MoreLabels = Empty
module StdLabels = Empty
module StringLabels = Empty
module Filename = Empty
module Parsing = Empty
module Stdlib = Empty
module Sys : sig ... end
val (<>) : int -> int -> bool
val (=) : int -> int -> bool
val (<) : int -> int -> bool
val (>) : int -> int -> bool
val (<=) : int -> int -> bool
val (>=) : int -> int -> bool
val compare : int -> int -> int
val min : int -> int -> int
val max : int -> int -> int
val phys_equal : 'a -> 'a -> bool
val not_phys_equal : 'a -> 'a -> bool
val char_of_int : int -> char option
val bool_of_string : string -> bool option
val int_of_string : string -> int option
val float_of_string : string -> float option
type this_function_has_been_hidden_by_the_prelude_because_it_is_unwanted = |
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