1Stdlib(3) OCaml library Stdlib(3)
2
6 Stdlib - The OCaml Standard library.
7
9 Module Stdlib
10
12 Module Stdlib
13 : sig end
14 The OCaml Standard library.
17 This module is automatically opened at the beginning of each compila‐
19 tion. All components of this module can therefore be referred by their
20 short name, without prefixing them by Stdlib .
21 It particular, it provides the basic operations over the built-in types
23 (numbers, booleans, byte sequences, strings, exceptions, references,
24 lists, arrays, input-output channels, ...) and the modules .
25 Exceptions
33 val raise : exn -> 'a
34 Raise the given exception value
36 val raise_notrace : exn -> 'a
40 A faster version raise which does not record the backtrace.
42 Since 4.02.0
45 val invalid_arg : string -> 'a
49 Raise exception Invalid_argument with the given string.
51 val failwith : string -> 'a
55 Raise exception Failure with the given string.
57 exception Exit
61 The Exit exception is not raised by any library function. It is pro‐
64 vided for use in your programs.
65 exception Match_failure of (string * int * int)
69 Exception raised when none of the cases of a pattern-matching apply.
72 The arguments are the location of the match keyword in the source code
73 (file name, line number, column number).
74 exception Assert_failure of (string * int * int)
78 Exception raised when an assertion fails. The arguments are the loca‐
81 tion of the assert keyword in the source code (file name, line number,
82 column number).
83 exception Invalid_argument of string
87 Exception raised by library functions to signal that the given argu‐
90 ments do not make sense. The string gives some information to the pro‐
91 grammer. As a general rule, this exception should not be caught, it
92 denotes a programming error and the code should be modified not to
93 trigger it.
94 exception Failure of string
98 Exception raised by library functions to signal that they are undefined
101 on the given arguments. The string is meant to give some information to
102 the programmer; you must not pattern match on the string literal
103 because it may change in future versions (use Failure _ instead).
104 exception Not_found
108 Exception raised by search functions when the desired object could not
111 be found.
112 exception Out_of_memory
116 Exception raised by the garbage collector when there is insufficient
119 memory to complete the computation.
120 exception Stack_overflow
124 Exception raised by the bytecode interpreter when the evaluation stack
127 reaches its maximal size. This often indicates infinite or excessively
128 deep recursion in the user's program. (Not fully implemented by the
129 native-code compiler.)
130 exception Sys_error of string
134 Exception raised by the input/output functions to report an operating
137 system error. The string is meant to give some information to the pro‐
138 grammer; you must not pattern match on the string literal because it
139 may change in future versions (use Sys_error _ instead).
140 exception End_of_file
144 Exception raised by input functions to signal that the end of file has
147 been reached.
148 exception Division_by_zero
152 Exception raised by integer division and remainder operations when
155 their second argument is zero.
156 exception Sys_blocked_io
160 A special case of Sys_error raised when no I/O is possible on a
163 non-blocking I/O channel.
164 exception Undefined_recursive_module of (string * int * int)
168 Exception raised when an ill-founded recursive module definition is
171 evaluated. The arguments are the location of the definition in the
172 source code (file name, line number, column number).
173 Comparisons
178 val (=) : 'a -> 'a -> bool
179 e1 = e2 tests for structural equality of e1 and e2 . Mutable struc‐
182 tures (e.g. references and arrays) are equal if and only if their cur‐
183 rent contents are structurally equal, even if the two mutable objects
184 are not the same physical object. Equality between functional values
185 raises Invalid_argument . Equality between cyclic data structures may
186 not terminate. Left-associative operator, see Ocaml_operators for more
187 information.
188 val (<>) : 'a -> 'a -> bool
192 Negation of (=) . Left-associative operator, see Ocaml_operators for
194 more information.
195 val (<) : 'a -> 'a -> bool
199 See (>=) . Left-associative operator, see Ocaml_operators for more
201 information.
202 val (>) : 'a -> 'a -> bool
206 See (>=) . Left-associative operator, see Ocaml_operators for more
208 information.
209 val (<=) : 'a -> 'a -> bool
213 See (>=) . Left-associative operator, see Ocaml_operators for more
215 information.
216 val (>=) : 'a -> 'a -> bool
220 Structural ordering functions. These functions coincide with the usual
222 orderings over integers, characters, strings, byte sequences and float‐
223 ing-point numbers, and extend them to a total ordering over all types.
224 The ordering is compatible with ( = ) . As in the case of ( = ) , muta‐
225 ble structures are compared by contents. Comparison between functional
226 values raises Invalid_argument . Comparison between cyclic structures
227 may not terminate. Left-associative operator, see Ocaml_operators for
228 more information.
229 val compare : 'a -> 'a -> int
233 compare x y returns 0 if x is equal to y , a negative integer if x is
236 less than y , and a positive integer if x is greater than y . The
237 ordering implemented by compare is compatible with the comparison pred‐
238 icates = , < and > defined above, with one difference on the treatment
239 of the float value nan . Namely, the comparison predicates treat nan
240 as different from any other float value, including itself; while com‐
241 pare treats nan as equal to itself and less than any other float value.
242 This treatment of nan ensures that compare defines a total ordering
243 relation.
244 compare applied to functional values may raise Invalid_argument . com‐
247 pare applied to cyclic structures may not terminate.
248 The compare function can be used as the comparison function required by
250 the Set.Make and Map.Make functors, as well as the List.sort and
251 Array.sort functions.
252 val min : 'a -> 'a -> 'a
256 Return the smaller of the two arguments. The result is unspecified if
258 one of the arguments contains the float value nan .
259 val max : 'a -> 'a -> 'a
263 Return the greater of the two arguments. The result is unspecified if
265 one of the arguments contains the float value nan .
266 val (==) : 'a -> 'a -> bool
270 e1 == e2 tests for physical equality of e1 and e2 . On mutable types
273 such as references, arrays, byte sequences, records with mutable fields
274 and objects with mutable instance variables, e1 == e2 is true if and
275 only if physical modification of e1 also affects e2 . On non-mutable
276 types, the behavior of ( == ) is implementation-dependent; however, it
277 is guaranteed that e1 == e2 implies compare e1 e2 = 0 . Left-associa‐
278 tive operator, see Ocaml_operators for more information.
279 val (!=) : 'a -> 'a -> bool
283 Negation of (==) . Left-associative operator, see Ocaml_operators for
285 more information.
286 Boolean operations
291 val not : bool -> bool
292 The boolean negation.
294 val (&&) : bool -> bool -> bool
298 The boolean 'and'. Evaluation is sequential, left-to-right: in e1 && e2
300 , e1 is evaluated first, and if it returns false , e2 is not evaluated
301 at all. Right-associative operator, see Ocaml_operators for more
302 information.
303 val (&) : bool -> bool -> bool
307 Deprecated.
309 (&&) should be used instead. Right-associative operator, see
311 Ocaml_operators for more information.
312 val (||) : bool -> bool -> bool
316 The boolean 'or'. Evaluation is sequential, left-to-right: in e1 || e2
318 , e1 is evaluated first, and if it returns true , e2 is not evaluated
319 at all. Right-associative operator, see Ocaml_operators for more
320 information.
321 val (or) : bool -> bool -> bool
325 Deprecated.
327 (||) should be used instead. Right-associative operator, see
329 Ocaml_operators for more information.
330 Debugging
335 val __LOC__ : string
336 __LOC__ returns the location at which this expression appears in the
339 file currently being parsed by the compiler, with the standard error
340 format of OCaml: "File %S, line %d, characters %d-%d".
341 Since 4.02.0
344 val __FILE__ : string
348 __FILE__ returns the name of the file currently being parsed by the
351 compiler.
352 Since 4.02.0
355 val __LINE__ : int
359 __LINE__ returns the line number at which this expression appears in
362 the file currently being parsed by the compiler.
363 Since 4.02.0
366 val __MODULE__ : string
370 __MODULE__ returns the module name of the file being parsed by the com‐
373 piler.
374 Since 4.02.0
377 val __POS__ : string * int * int * int
381 __POS__ returns a tuple (file,lnum,cnum,enum) , corresponding to the
384 location at which this expression appears in the file currently being
385 parsed by the compiler. file is the current filename, lnum the line
386 number, cnum the character position in the line and enum the last char‐
387 acter position in the line.
388 Since 4.02.0
391 val __LOC_OF__ : 'a -> string * 'a
395 __LOC_OF__ expr returns a pair (loc, expr) where loc is the location of
398 expr in the file currently being parsed by the compiler, with the stan‐
399 dard error format of OCaml: "File %S, line %d, characters %d-%d".
400 Since 4.02.0
403 val __LINE_OF__ : 'a -> int * 'a
407 __LINE_OF__ expr returns a pair (line, expr) , where line is the line
410 number at which the expression expr appears in the file currently being
411 parsed by the compiler.
412 Since 4.02.0
415 val __POS_OF__ : 'a -> (string * int * int * int) * 'a
419 __POS_OF__ expr returns a pair (loc,expr) , where loc is a tuple
422 (file,lnum,cnum,enum) corresponding to the location at which the
423 expression expr appears in the file currently being parsed by the com‐
424 piler. file is the current filename, lnum the line number, cnum the
425 character position in the line and enum the last character position in
426 the line.
427 Since 4.02.0
430 Composition operators
435 val (|>) : 'a -> ('a -> 'b) -> 'b
436 Reverse-application operator: x |> f |> g is exactly equivalent to g (f
438 (x)) . Left-associative operator, see Ocaml_operators for more infor‐
439 mation.
440 Since 4.01
443 val (@@) : ('a -> 'b) -> 'a -> 'b
447 Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
449 Right-associative operator, see Ocaml_operators for more information.
450 Since 4.01
453 Integer arithmetic
458 Integers are Sys.int_size bits wide. All operations are taken modulo
459 2^ Sys.int_size . They do not fail on overflow.
460 val (~-) : int -> int
462 Unary negation. You can also write - e instead of ~- e . Unary opera‐
464 tor, see Ocaml_operators for more information.
465 val (~+) : int -> int
469 Unary addition. You can also write + e instead of ~+ e . Unary opera‐
471 tor, see Ocaml_operators for more information.
472 Since 3.12.0
475 val succ : int -> int
479 succ x is x + 1 .
482 val pred : int -> int
486 pred x is x - 1 .
489 val (+) : int -> int -> int
493 Integer addition. Left-associative operator, see Ocaml_operators for
495 more information.
496 val (-) : int -> int -> int
500 Integer subtraction. Left-associative operator, , see Ocaml_operators
502 for more information.
503 val ( * ) : int -> int -> int
507 Integer multiplication. Left-associative operator, see Ocaml_operators
509 for more information.
510 val (/) : int -> int -> int
514 Integer division. Raise Division_by_zero if the second argument is 0.
516 Integer division rounds the real quotient of its arguments towards
517 zero. More precisely, if x >= 0 and y > 0 , x / y is the greatest
518 integer less than or equal to the real quotient of x by y . Moreover,
519 (- x) / y = x / (- y) = - (x / y) . Left-associative operator, see
520 Ocaml_operators for more information.
521 val (mod) : int -> int -> int
525 Integer remainder. If y is not zero, the result of x mod y satisfies
527 the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
528 abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
529 mod y is negative only if x < 0 . Raise Division_by_zero if y is zero.
530 Left-associative operator, see Ocaml_operators for more information.
531 val abs : int -> int
535 Return the absolute value of the argument. Note that this may be nega‐
537 tive if the argument is min_int .
538 val max_int : int
542 The greatest representable integer.
544 val min_int : int
548 The smallest representable integer.
550 Bitwise operations
555 val (land) : int -> int -> int
556 Bitwise logical and. Left-associative operator, see Ocaml_operators
558 for more information.
559 val (lor) : int -> int -> int
563 Bitwise logical or. Left-associative operator, see Ocaml_operators for
565 more information.
566 val (lxor) : int -> int -> int
570 Bitwise logical exclusive or. Left-associative operator, see
572 Ocaml_operators for more information.
573 val lnot : int -> int
577 Bitwise logical negation.
579 val (lsl) : int -> int -> int
583 n lsl m shifts n to the left by m bits. The result is unspecified if m
586 < 0 or m > Sys.int_size . Right-associative operator, see Ocaml_opera‐
587 tors for more information.
588 val (lsr) : int -> int -> int
592 n lsr m shifts n to the right by m bits. This is a logical shift:
595 zeroes are inserted regardless of the sign of n . The result is
596 unspecified if m < 0 or m > Sys.int_size . Right-associative operator,
597 see Ocaml_operators for more information.
598 val (asr) : int -> int -> int
602 n asr m shifts n to the right by m bits. This is an arithmetic shift:
605 the sign bit of n is replicated. The result is unspecified if m < 0 or
606 m > Sys.int_size . Right-associative operator, see Ocaml_operators for
607 more information.
608 Floating-point arithmetic
613 OCaml's floating-point numbers follow the IEEE 754 standard, using dou‐
614 ble precision (64 bits) numbers. Floating-point operations never raise
615 an exception on overflow, underflow, division by zero, etc. Instead,
616 special IEEE numbers are returned as appropriate, such as infinity for
617 1.0 /. 0.0 , neg_infinity for -1.0 /. 0.0 , and nan ('not a number')
618 for 0.0 /. 0.0 . These special numbers then propagate through float‐
619 ing-point computations as expected: for instance, 1.0 /. infinity is
620 0.0 , and any arithmetic operation with nan as argument returns nan as
621 result.
622 val (~-.) : float -> float
624 Unary negation. You can also write -. e instead of ~-. e . Unary oper‐
626 ator, see Ocaml_operators for more information.
627 val (~+.) : float -> float
631 Unary addition. You can also write +. e instead of ~+. e . Unary oper‐
633 ator, see Ocaml_operators for more information.
634 Since 3.12.0
637 val (+.) : float -> float -> float
641 Floating-point addition. Left-associative operator, see Ocaml_opera‐
643 tors for more information.
644 val (-.) : float -> float -> float
648 Floating-point subtraction. Left-associative operator, see Ocaml_oper‐
650 ators for more information.
651 val ( *. ) : float -> float -> float
655 Floating-point multiplication. Left-associative operator, see
657 Ocaml_operators for more information.
658 val (/.) : float -> float -> float
662 Floating-point division. Left-associative operator, see Ocaml_opera‐
664 tors for more information.
665 val ( ** ) : float -> float -> float
669 Exponentiation. Right-associative operator, see Ocaml_operators for
671 more information.
672 val sqrt : float -> float
676 Square root.
678 val exp : float -> float
682 Exponential.
684 val log : float -> float
688 Natural logarithm.
690 val log10 : float -> float
694 Base 10 logarithm.
696 val expm1 : float -> float
700 expm1 x computes exp x -. 1.0 , giving numerically-accurate results
703 even if x is close to 0.0 .
704 Since 3.12.0
707 val log1p : float -> float
711 log1p x computes log(1.0 +. x) (natural logarithm), giving numeri‐
714 cally-accurate results even if x is close to 0.0 .
715 Since 3.12.0
718 val cos : float -> float
722 Cosine. Argument is in radians.
724 val sin : float -> float
728 Sine. Argument is in radians.
730 val tan : float -> float
734 Tangent. Argument is in radians.
736 val acos : float -> float
740 Arc cosine. The argument must fall within the range [-1.0, 1.0] .
742 Result is in radians and is between 0.0 and pi .
743 val asin : float -> float
747 Arc sine. The argument must fall within the range [-1.0, 1.0] .
749 Result is in radians and is between -pi/2 and pi/2 .
750 val atan : float -> float
754 Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
756 val atan2 : float -> float -> float
760 atan2 y x returns the arc tangent of y /. x . The signs of x and y are
763 used to determine the quadrant of the result. Result is in radians and
764 is between -pi and pi .
765 val hypot : float -> float -> float
769 hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
772 hypotenuse of a right-angled triangle with sides of length x and y ,
773 or, equivalently, the distance of the point (x,y) to origin. If one of
774 x or y is infinite, returns infinity even if the other is nan .
775 Since 4.00.0
778 val cosh : float -> float
782 Hyperbolic cosine. Argument is in radians.
784 val sinh : float -> float
788 Hyperbolic sine. Argument is in radians.
790 val tanh : float -> float
794 Hyperbolic tangent. Argument is in radians.
796 val ceil : float -> float
800 Round above to an integer value. ceil f returns the least integer
802 value greater than or equal to f . The result is returned as a float.
803 val floor : float -> float
807 Round below to an integer value. floor f returns the greatest integer
809 value less than or equal to f . The result is returned as a float.
810 val abs_float : float -> float
814 abs_float f returns the absolute value of f .
817 val copysign : float -> float -> float
821 copysign x y returns a float whose absolute value is that of x and
824 whose sign is that of y . If x is nan , returns nan . If y is nan ,
825 returns either x or -. x , but it is not specified which.
826 Since 4.00.0
829 val mod_float : float -> float -> float
833 mod_float a b returns the remainder of a with respect to b . The
836 returned value is a -. n *. b , where n is the quotient a /. b rounded
837 towards zero to an integer.
838 val frexp : float -> float * int
842 frexp f returns the pair of the significant and the exponent of f .
845 When f is zero, the significant x and the exponent n of f are equal to
846 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
847 <= x < 1.0 .
848 val ldexp : float -> int -> float
852 ldexp x n returns x *. 2 ** n .
855 val modf : float -> float * float
859 modf f returns the pair of the fractional and integral part of f .
862 val float : int -> float
866 Same as float_of_int .
868 val float_of_int : int -> float
872 Convert an integer to floating-point.
874 val truncate : float -> int
878 Same as int_of_float .
880 val int_of_float : float -> int
884 Truncate the given floating-point number to an integer. The result is
886 unspecified if the argument is nan or falls outside the range of repre‐
887 sentable integers.
888 val infinity : float
892 Positive infinity.
894 val neg_infinity : float
898 Negative infinity.
900 val nan : float
904 A special floating-point value denoting the result of an undefined
906 operation such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
907 ing-point operation with nan as argument returns nan as result. As for
908 floating-point comparisons, = , < , <= , > and >= return false and <>
909 returns true if one or both of their arguments is nan .
910 val max_float : float
914 The largest positive finite value of type float .
916 val min_float : float
920 The smallest positive, non-zero, non-denormalized value of type float .
922 val epsilon_float : float
926 The difference between 1.0 and the smallest exactly representable
928 floating-point number greater than 1.0 .
929 type fpclass =
932 | FP_normal (* Normal number, none of the below
933 *)
934 | FP_subnormal (* Number very close to 0.0, has reduced precision
935 *)
936 | FP_zero (* Number is 0.0 or -0.0
937 *)
938 | FP_infinite (* Number is positive or negative infinity
939 *)
940 | FP_nan (* Not a number: result of an undefined operation
941 *)
942 The five classes of floating-point numbers, as determined by the clas‐
945 sify_float function.
946 val classify_float : float -> fpclass
950 Return the class of the given floating-point number: normal, subnormal,
952 zero, infinite, or not a number.
953 String operations
958 More string operations are provided in module String .
959 val (^) : string -> string -> string
961 String concatenation. Right-associative operator, see Ocaml_operators
963 for more information.
964 Character operations
969 More character operations are provided in module Char .
970 val int_of_char : char -> int
972 Return the ASCII code of the argument.
974 val char_of_int : int -> char
978 Return the character with the given ASCII code. Raise Invalid_argument
980 char_of_int if the argument is outside the range 0--255.
981 Unit operations
986 val ignore : 'a -> unit
987 Discard the value of its argument and return () . For instance,
989 ignore(f x) discards the result of the side-effecting function f . It
990 is equivalent to f x; () , except that the latter may generate a com‐
991 piler warning; writing ignore(f x) instead avoids the warning.
992 String conversion functions
997 val string_of_bool : bool -> string
998 Return the string representation of a boolean. As the returned values
1000 may be shared, the user should not modify them directly.
1001 val bool_of_string_opt : string -> bool option
1005 Convert the given string to a boolean.
1007 Return None if the string is not true or false .
1009 Since 4.05
1012 val bool_of_string : string -> bool
1016 Same as bool_of_string_opt , but raise Invalid_argument bool_of_string
1018 instead of returning None .
1019 val string_of_int : int -> string
1023 Return the string representation of an integer, in decimal.
1025 val int_of_string_opt : string -> int option
1029 Convert the given string to an integer. The string is read in decimal
1031 (by default, or if the string begins with 0u ), in hexadecimal (if it
1032 begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
1033 binary (if it begins with 0b or 0B ).
1034 The 0u prefix reads the input as an unsigned integer in the range [0,
1036 2*max_int+1] . If the input exceeds max_int it is converted to the
1037 signed integer min_int + input - max_int - 1 .
1038 The _ (underscore) character can appear anywhere in the string and is
1040 ignored.
1041 Return None if the given string is not a valid representation of an
1043 integer, or if the integer represented exceeds the range of integers
1044 representable in type int .
1045 Since 4.05
1048 val int_of_string : string -> int
1052 Same as int_of_string_opt , but raise Failure int_of_string instead of
1054 returning None .
1055 val string_of_float : float -> string
1059 Return the string representation of a floating-point number.
1061 val float_of_string_opt : string -> float option
1065 Convert the given string to a float. The string is read in decimal (by
1067 default) or in hexadecimal (marked by 0x or 0X ).
1068 The format of decimal floating-point numbers is [-] dd.ddd (e|E) [+|-]
1070 dd , where d stands for a decimal digit.
1071 The format of hexadecimal floating-point numbers is [-] 0(x|X) hh.hhh
1073 (p|P) [+|-] dd , where h stands for an hexadecimal digit and d for a
1074 decimal digit.
1075 In both cases, at least one of the integer and fractional parts must be
1077 given; the exponent part is optional.
1078 The _ (underscore) character can appear anywhere in the string and is
1080 ignored.
1081 Depending on the execution platforms, other representations of float‐
1083 ing-point numbers can be accepted, but should not be relied upon.
1084 Return None if the given string is not a valid representation of a
1086 float.
1087 Since 4.05
1090 val float_of_string : string -> float
1094 Same as float_of_string_opt , but raise Failure float_of_string instead
1096 of returning None .
1097 Pair operations
1102 val fst : 'a * 'b -> 'a
1103 Return the first component of a pair.
1105 val snd : 'a * 'b -> 'b
1109 Return the second component of a pair.
1111 List operations
1116 More list operations are provided in module List .
1117 val (@) : 'a list -> 'a list -> 'a list
1119 List concatenation. Not tail-recursive (length of the first argument).
1121 Right-associative operator, see Ocaml_operators for more information.
1122 Input/output
1127 Note: all input/output functions can raise Sys_error when the system
1128 calls they invoke fail.
1129 type in_channel
1131 The type of input channel.
1134 type out_channel
1137 The type of output channel.
1140 val stdin : in_channel
1144 The standard input for the process.
1146 val stdout : out_channel
1150 The standard output for the process.
1152 val stderr : out_channel
1156 The standard error output for the process.
1158 Output functions on standard output
1163 val print_char : char -> unit
1164 Print a character on standard output.
1166 val print_string : string -> unit
1170 Print a string on standard output.
1172 val print_bytes : bytes -> unit
1176 Print a byte sequence on standard output.
1178 Since 4.02.0
1181 val print_int : int -> unit
1185 Print an integer, in decimal, on standard output.
1187 val print_float : float -> unit
1191 Print a floating-point number, in decimal, on standard output.
1193 val print_endline : string -> unit
1197 Print a string, followed by a newline character, on standard output and
1199 flush standard output.
1200 val print_newline : unit -> unit
1204 Print a newline character on standard output, and flush standard out‐
1206 put. This can be used to simulate line buffering of standard output.
1207 Output functions on standard error
1212 val prerr_char : char -> unit
1213 Print a character on standard error.
1215 val prerr_string : string -> unit
1219 Print a string on standard error.
1221 val prerr_bytes : bytes -> unit
1225 Print a byte sequence on standard error.
1227 Since 4.02.0
1230 val prerr_int : int -> unit
1234 Print an integer, in decimal, on standard error.
1236 val prerr_float : float -> unit
1240 Print a floating-point number, in decimal, on standard error.
1242 val prerr_endline : string -> unit
1246 Print a string, followed by a newline character on standard error and
1248 flush standard error.
1249 val prerr_newline : unit -> unit
1253 Print a newline character on standard error, and flush standard error.
1255 Input functions on standard input
1260 val read_line : unit -> string
1261 Flush standard output, then read characters from standard input until a
1263 newline character is encountered. Return the string of all characters
1264 read, without the newline character at the end.
1265 val read_int_opt : unit -> int option
1269 Flush standard output, then read one line from standard input and con‐
1271 vert it to an integer.
1272 Return None if the line read is not a valid representation of an inte‐
1274 ger.
1275 Since 4.05
1278 val read_int : unit -> int
1282 Same as read_int_opt , but raise Failure int_of_string instead of
1284 returning None .
1285 val read_float_opt : unit -> float option
1289 Flush standard output, then read one line from standard input and con‐
1291 vert it to a floating-point number.
1292 Return None if the line read is not a valid representation of a float‐
1294 ing-point number.
1295 Since 4.05.0
1298 val read_float : unit -> float
1302 Same as read_float_opt , but raise Failure float_of_string instead of
1304 returning None .
1305 General output functions
1310 type open_flag =
1311 | Open_rdonly (* open for reading.
1312 *)
1313 | Open_wronly (* open for writing.
1314 *)
1315 | Open_append (* open for appending: always write at end of file.
1316 *)
1317 | Open_creat (* create the file if it does not exist.
1318 *)
1319 | Open_trunc (* empty the file if it already exists.
1320 *)
1321 | Open_excl (* fail if Open_creat and the file already exists.
1322 *)
1323 | Open_binary (* open in binary mode (no conversion).
1324 *)
1325 | Open_text (* open in text mode (may perform conversions).
1326 *)
1327 | Open_nonblock (* open in non-blocking mode.
1328 *)
1329 Opening modes for open_out_gen and open_in_gen .
1332 val open_out : string -> out_channel
1336 Open the named file for writing, and return a new output channel on
1338 that file, positioned at the beginning of the file. The file is trun‐
1339 cated to zero length if it already exists. It is created if it does not
1340 already exists.
1341 val open_out_bin : string -> out_channel
1345 Same as open_out , but the file is opened in binary mode, so that no
1347 translation takes place during writes. On operating systems that do not
1348 distinguish between text mode and binary mode, this function behaves
1349 like open_out .
1350 val open_out_gen : open_flag list -> int -> string -> out_channel
1354 open_out_gen mode perm filename opens the named file for writing, as
1357 described above. The extra argument mode specifies the opening mode.
1358 The extra argument perm specifies the file permissions, in case the
1359 file must be created. open_out and open_out_bin are special cases of
1360 this function.
1361 val flush : out_channel -> unit
1365 Flush the buffer associated with the given output channel, performing
1367 all pending writes on that channel. Interactive programs must be care‐
1368 ful about flushing standard output and standard error at the right
1369 time.
1370 val flush_all : unit -> unit
1374 Flush all open output channels; ignore errors.
1376 val output_char : out_channel -> char -> unit
1380 Write the character on the given output channel.
1382 val output_string : out_channel -> string -> unit
1386 Write the string on the given output channel.
1388 val output_bytes : out_channel -> bytes -> unit
1392 Write the byte sequence on the given output channel.
1394 Since 4.02.0
1397 val output : out_channel -> bytes -> int -> int -> unit
1401 output oc buf pos len writes len characters from byte sequence buf ,
1404 starting at offset pos , to the given output channel oc . Raise
1405 Invalid_argument output if pos and len do not designate a valid range
1406 of buf .
1407 val output_substring : out_channel -> string -> int -> int -> unit
1411 Same as output but take a string as argument instead of a byte
1413 sequence.
1414 Since 4.02.0
1417 val output_byte : out_channel -> int -> unit
1421 Write one 8-bit integer (as the single character with that code) on the
1423 given output channel. The given integer is taken modulo 256.
1424 val output_binary_int : out_channel -> int -> unit
1428 Write one integer in binary format (4 bytes, big-endian) on the given
1430 output channel. The given integer is taken modulo 2^32. The only
1431 reliable way to read it back is through the input_binary_int function.
1432 The format is compatible across all machines for a given version of
1433 OCaml.
1434 val output_value : out_channel -> 'a -> unit
1438 Write the representation of a structured value of any type to a chan‐
1440 nel. Circularities and sharing inside the value are detected and pre‐
1441 served. The object can be read back, by the function input_value . See
1442 the description of module Marshal for more information. output_value
1443 is equivalent to Marshal.to_channel with an empty list of flags.
1444 val seek_out : out_channel -> int -> unit
1448 seek_out chan pos sets the current writing position to pos for channel
1451 chan . This works only for regular files. On files of other kinds (such
1452 as terminals, pipes and sockets), the behavior is unspecified.
1453 val pos_out : out_channel -> int
1457 Return the current writing position for the given channel. Does not
1459 work on channels opened with the Open_append flag (returns unspecified
1460 results).
1461 val out_channel_length : out_channel -> int
1465 Return the size (number of characters) of the regular file on which the
1467 given channel is opened. If the channel is opened on a file that is
1468 not a regular file, the result is meaningless.
1469 val close_out : out_channel -> unit
1473 Close the given channel, flushing all buffered write operations. Out‐
1475 put functions raise a Sys_error exception when they are applied to a
1476 closed output channel, except close_out and flush , which do nothing
1477 when applied to an already closed channel. Note that close_out may
1478 raise Sys_error if the operating system signals an error when flushing
1479 or closing.
1480 val close_out_noerr : out_channel -> unit
1484 Same as close_out , but ignore all errors.
1486 val set_binary_mode_out : out_channel -> bool -> unit
1490 set_binary_mode_out oc true sets the channel oc to binary mode: no
1493 translations take place during output. set_binary_mode_out oc false
1494 sets the channel oc to text mode: depending on the operating system,
1495 some translations may take place during output. For instance, under
1496 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1497 tion has no effect under operating systems that do not distinguish
1498 between text mode and binary mode.
1499 General input functions
1504 val open_in : string -> in_channel
1505 Open the named file for reading, and return a new input channel on that
1507 file, positioned at the beginning of the file.
1508 val open_in_bin : string -> in_channel
1512 Same as open_in , but the file is opened in binary mode, so that no
1514 translation takes place during reads. On operating systems that do not
1515 distinguish between text mode and binary mode, this function behaves
1516 like open_in .
1517 val open_in_gen : open_flag list -> int -> string -> in_channel
1521 open_in_gen mode perm filename opens the named file for reading, as
1524 described above. The extra arguments mode and perm specify the opening
1525 mode and file permissions. open_in and open_in_bin are special cases
1526 of this function.
1527 val input_char : in_channel -> char
1531 Read one character from the given input channel. Raise End_of_file if
1533 there are no more characters to read.
1534 val input_line : in_channel -> string
1538 Read characters from the given input channel, until a newline character
1540 is encountered. Return the string of all characters read, without the
1541 newline character at the end. Raise End_of_file if the end of the file
1542 is reached at the beginning of line.
1543 val input : in_channel -> bytes -> int -> int -> int
1547 input ic buf pos len reads up to len characters from the given channel
1550 ic , storing them in byte sequence buf , starting at character number
1551 pos . It returns the actual number of characters read, between 0 and
1552 len (inclusive). A return value of 0 means that the end of file was
1553 reached. A return value between 0 and len exclusive means that not all
1554 requested len characters were read, either because no more characters
1555 were available at that time, or because the implementation found it
1556 convenient to do a partial read; input must be called again to read the
1557 remaining characters, if desired. (See also really_input for reading
1558 exactly len characters.) Exception Invalid_argument input is raised if
1559 pos and len do not designate a valid range of buf .
1560 val really_input : in_channel -> bytes -> int -> int -> unit
1564 really_input ic buf pos len reads len characters from channel ic ,
1567 storing them in byte sequence buf , starting at character number pos .
1568 Raise End_of_file if the end of file is reached before len characters
1569 have been read. Raise Invalid_argument really_input if pos and len do
1570 not designate a valid range of buf .
1571 val really_input_string : in_channel -> int -> string
1575 really_input_string ic len reads len characters from channel ic and
1578 returns them in a new string. Raise End_of_file if the end of file is
1579 reached before len characters have been read.
1580 Since 4.02.0
1583 val input_byte : in_channel -> int
1587 Same as input_char , but return the 8-bit integer representing the
1589 character. Raise End_of_file if an end of file was reached.
1590 val input_binary_int : in_channel -> int
1594 Read an integer encoded in binary format (4 bytes, big-endian) from the
1596 given input channel. See output_binary_int . Raise End_of_file if an
1597 end of file was reached while reading the integer.
1598 val input_value : in_channel -> 'a
1602 Read the representation of a structured value, as produced by out‐
1604 put_value , and return the corresponding value. This function is iden‐
1605 tical to Marshal.from_channel ; see the description of module Marshal
1606 for more information, in particular concerning the lack of type safety.
1607 val seek_in : in_channel -> int -> unit
1611 seek_in chan pos sets the current reading position to pos for channel
1614 chan . This works only for regular files. On files of other kinds, the
1615 behavior is unspecified.
1616 val pos_in : in_channel -> int
1620 Return the current reading position for the given channel.
1622 val in_channel_length : in_channel -> int
1626 Return the size (number of characters) of the regular file on which the
1628 given channel is opened. If the channel is opened on a file that is
1629 not a regular file, the result is meaningless. The returned size does
1630 not take into account the end-of-line translations that can be per‐
1631 formed when reading from a channel opened in text mode.
1632 val close_in : in_channel -> unit
1636 Close the given channel. Input functions raise a Sys_error exception
1638 when they are applied to a closed input channel, except close_in ,
1639 which does nothing when applied to an already closed channel.
1640 val close_in_noerr : in_channel -> unit
1644 Same as close_in , but ignore all errors.
1646 val set_binary_mode_in : in_channel -> bool -> unit
1650 set_binary_mode_in ic true sets the channel ic to binary mode: no
1653 translations take place during input. set_binary_mode_out ic false
1654 sets the channel ic to text mode: depending on the operating system,
1655 some translations may take place during input. For instance, under
1656 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1657 tion has no effect under operating systems that do not distinguish
1658 between text mode and binary mode.
1659 Operations on large files
1664 module LargeFile : sig end
1665 Operations on large files. This sub-module provides 64-bit variants of
1668 the channel functions that manipulate file positions and file sizes.
1669 By representing positions and sizes by 64-bit integers (type int64 )
1670 instead of regular integers (type int ), these alternate functions
1671 allow operating on files whose sizes are greater than max_int .
1672 References
1677 type 'a ref = {
1678 mutable contents : 'a ;
1680 }
1681 The type of references (mutable indirection cells) containing a value
1684 of type 'a .
1685 val ref : 'a -> 'a ref
1689 Return a fresh reference containing the given value.
1691 val (!) : 'a ref -> 'a
1695 !r returns the current contents of reference r . Equivalent to fun r
1698 -> r.contents . Unary operator, see Ocaml_operators for more informa‐
1699 tion.
1700 val (:=) : 'a ref -> 'a -> unit
1704 r := a stores the value of a in reference r . Equivalent to fun r v ->
1707 r.contents <- v . Right-associative operator, see Ocaml_operators for
1708 more information.
1709 val incr : int ref -> unit
1713 Increment the integer contained in the given reference. Equivalent to
1715 fun r -> r := succ !r .
1716 val decr : int ref -> unit
1720 Decrement the integer contained in the given reference. Equivalent to
1722 fun r -> r := pred !r .
1723 Result type
1728 type ('a, 'b) result =
1729 | Ok of 'a
1730 | Error of 'b
1731 Since 4.03.0
1734 Operations on format strings
1739 Format strings are character strings with special lexical conventions
1740 that defines the functionality of formatted input/output functions.
1741 Format strings are used to read data with formatted input functions
1742 from module Scanf and to print data with formatted output functions
1743 from modules Printf and Format .
1744 Format strings are made of three kinds of entities:
1746 -conversions specifications, introduced by the special character '%'
1748 followed by one or more characters specifying what kind of argument to
1749 read or print,
1750 -formatting indications, introduced by the special character '@' fol‐
1752 lowed by one or more characters specifying how to read or print the
1753 argument,
1754 -plain characters that are regular characters with usual lexical con‐
1756 ventions. Plain characters specify string literals to be read in the
1757 input or printed in the output.
1758 There is an additional lexical rule to escape the special characters
1760 '%' and '@' in format strings: if a special character follows a '%'
1761 character, it is treated as a plain character. In other words, %% is
1762 considered as a plain '%' and %@ as a plain '@' .
1763 For more information about conversion specifications and formatting
1765 indications available, read the documentation of modules Scanf , Printf
1766 and Format .
1767 Format strings have a general and highly polymorphic type ('a, 'b, 'c,
1769 'd, 'e, 'f) format6 . The two simplified types, format and format4
1770 below are included for backward compatibility with earlier releases of
1771 OCaml.
1772 The meaning of format string type parameters is as follows:
1774 - 'a is the type of the parameters of the format for formatted output
1777 functions ( printf -style functions); 'a is the type of the values read
1778 by the format for formatted input functions ( scanf -style functions).
1779 - 'b is the type of input source for formatted input functions and the
1782 type of output target for formatted output functions. For printf
1783 -style functions from module Printf , 'b is typically out_channel ; for
1784 printf -style functions from module Format , 'b is typically For‐
1785 mat.formatter ; for scanf -style functions from module Scanf , 'b is
1786 typically Scanf.Scanning.in_channel .
1787 Type argument 'b is also the type of the first argument given to user's
1789 defined printing functions for %a and %t conversions, and user's
1790 defined reading functions for %r conversion.
1791 - 'c is the type of the result of the %a and %t printing functions, and
1794 also the type of the argument transmitted to the first argument of
1795 kprintf -style functions or to the kscanf -style functions.
1796 - 'd is the type of parameters for the scanf -style functions.
1799 - 'e is the type of the receiver function for the scanf -style func‐
1802 tions.
1803 - 'f is the final result type of a formatted input/output function
1806 invocation: for the printf -style functions, it is typically unit ; for
1807 the scanf -style functions, it is typically the result type of the
1808 receiver function.
1809 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1812 linternalFormatBasics.format6
1813 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1818 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1823 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1829 Converts a format string into a string.
1831 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1835 'd, 'e, 'f) format6
1836 format_of_string s returns a format string read from the string literal
1839 s . Note: format_of_string can not convert a string argument that is
1840 not a literal. If you need this functionality, use the more general
1841 Scanf.format_from_string function.
1842 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1846 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1847 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1850 string that behaves as the concatenation of format strings f1 and f2 :
1851 in case of formatted output, it accepts arguments from f1 , then argu‐
1852 ments from f2 ; in case of formatted input, it returns results from f1
1853 , then results from f2 . Right-associative operator, see Ocaml_opera‐
1854 tors for more information.
1855 Program termination
1860 val exit : int -> 'a
1861 Terminate the process, returning the given status code to the operating
1863 system: usually 0 to indicate no errors, and a small positive integer
1864 to indicate failure. All open output channels are flushed with
1865 flush_all . An implicit exit 0 is performed each time a program termi‐
1866 nates normally. An implicit exit 2 is performed if the program termi‐
1867 nates early because of an uncaught exception.
1868 val at_exit : (unit -> unit) -> unit
1872 Register the given function to be called at program termination time.
1874 The functions registered with at_exit will be called when the program
1875 does any of the following:
1876 -executes exit
1878 -terminates, either normally or because of an uncaught exception
1881 -executes the C function caml_shutdown . The functions are called in
1883 'last in, first out' order: the function most recently added with
1884 at_exit is called first.
1885 Standard library modules
1891 module Arg : (module Stdlib__arg)
1892 module Array : (module Stdlib__array)
1897 module ArrayLabels : (module Stdlib__arrayLabels)
1902 module Bigarray : (module Stdlib__bigarray)
1907 module Bool : (module Stdlib__bool)
1912 module Buffer : (module Stdlib__buffer)
1917 module Bytes : (module Stdlib__bytes)
1922 module BytesLabels : (module Stdlib__bytesLabels)
1927 module Callback : (module Stdlib__callback)
1932 module Char : (module Stdlib__char)
1937 module Complex : (module Stdlib__complex)
1942 module Digest : (module Stdlib__digest)
1947 module Ephemeron : (module Stdlib__ephemeron)
1952 module Filename : (module Stdlib__filename)
1957 module Float : (module Stdlib__float)
1962 module Format : (module Stdlib__format)
1967 module Fun : (module Stdlib__fun)
1972 module Gc : (module Stdlib__gc)
1977 module Genlex : (module Stdlib__genlex)
1982 module Hashtbl : (module Stdlib__hashtbl)
1987 module Int : (module Stdlib__int)
1992 module Int32 : (module Stdlib__int32)
1997 module Int64 : (module Stdlib__int64)
2002 module Lazy : (module Stdlib__lazy)
2007 module Lexing : (module Stdlib__lexing)
2012 module List : (module Stdlib__list)
2017 module ListLabels : (module Stdlib__listLabels)
2022 module Map : (module Stdlib__map)
2027 module Marshal : (module Stdlib__marshal)
2032 module MoreLabels : (module Stdlib__moreLabels)
2037 module Nativeint : (module Stdlib__nativeint)
2042 module Obj : (module Stdlib__obj)
2047 module Oo : (module Stdlib__oo)
2052 module Option : (module Stdlib__option)
2057 module Parsing : (module Stdlib__parsing)
2062 module Pervasives : (module Stdlib__pervasives)
2067 module Printexc : (module Stdlib__printexc)
2072 module Printf : (module Stdlib__printf)
2077 module Queue : (module Stdlib__queue)
2082 module Random : (module Stdlib__random)
2087 module Result : (module Stdlib__result)
2092 module Scanf : (module Stdlib__scanf)
2097 module Seq : (module Stdlib__seq)
2102 module Set : (module Stdlib__set)
2107 module Spacetime : (module Stdlib__spacetime)
2112 module Stack : (module Stdlib__stack)
2117 module StdLabels : (module Stdlib__stdLabels)
2122 module Stream : (module Stdlib__stream)
2127 module String : (module Stdlib__string)
2132 module StringLabels : (module Stdlib__stringLabels)
2137 module Sys : (module Stdlib__sys)
2142 module Uchar : (module Stdlib__uchar)
2147 module Unit : (module Stdlib__unit)
2152 module Weak : (module Stdlib__weak)
2157OCamldoc 2019-07-30 Stdlib(3)