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 de‐
92 notes a programming error and the code should be modified not to trig‐
93 ger 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 be‐
103 cause 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. (Not reliable for allocations on
120 the minor heap.)
121 exception Stack_overflow
125 Exception raised by the bytecode interpreter when the evaluation stack
128 reaches its maximal size. This often indicates infinite or excessively
129 deep recursion in the user's program.
130 Before 4.10, it was not fully implemented by the native-code compiler.
132 exception Sys_error of string
136 Exception raised by the input/output functions to report an operating
139 system error. The string is meant to give some information to the pro‐
140 grammer; you must not pattern match on the string literal because it
141 may change in future versions (use Sys_error _ instead).
142 exception End_of_file
146 Exception raised by input functions to signal that the end of file has
149 been reached.
150 exception Division_by_zero
154 Exception raised by integer division and remainder operations when
157 their second argument is zero.
158 exception Sys_blocked_io
162 A special case of Sys_error raised when no I/O is possible on a
165 non-blocking I/O channel.
166 exception Undefined_recursive_module of (string * int * int)
170 Exception raised when an ill-founded recursive module definition is
173 evaluated. The arguments are the location of the definition in the
174 source code (file name, line number, column number).
175 Comparisons
180 val (=) : 'a -> 'a -> bool
181 e1 = e2 tests for structural equality of e1 and e2 . Mutable struc‐
184 tures (e.g. references and arrays) are equal if and only if their cur‐
185 rent contents are structurally equal, even if the two mutable objects
186 are not the same physical object. Equality between functional values
187 raises Invalid_argument . Equality between cyclic data structures may
188 not terminate. Left-associative operator, see Ocaml_operators for more
189 information.
190 val (<>) : 'a -> 'a -> bool
194 Negation of (=) . Left-associative operator, see Ocaml_operators for
196 more information.
197 val (<) : 'a -> 'a -> bool
201 See (>=) . Left-associative operator, see Ocaml_operators for more in‐
203 formation.
204 val (>) : 'a -> 'a -> bool
208 See (>=) . Left-associative operator, see Ocaml_operators for more
210 information.
211 val (<=) : 'a -> 'a -> bool
215 See (>=) . Left-associative operator, see Ocaml_operators for more
217 information.
218 val (>=) : 'a -> 'a -> bool
222 Structural ordering functions. These functions coincide with the usual
224 orderings over integers, characters, strings, byte sequences and float‐
225 ing-point numbers, and extend them to a total ordering over all types.
226 The ordering is compatible with ( = ) . As in the case of ( = ) , muta‐
227 ble structures are compared by contents. Comparison between functional
228 values raises Invalid_argument . Comparison between cyclic structures
229 may not terminate. Left-associative operator, see Ocaml_operators for
230 more information.
231 val compare : 'a -> 'a -> int
235 compare x y returns 0 if x is equal to y , a negative integer if x is
238 less than y , and a positive integer if x is greater than y . The or‐
239 dering implemented by compare is compatible with the comparison predi‐
240 cates = , < and > defined above, with one difference on the treatment
241 of the float value nan . Namely, the comparison predicates treat nan
242 as different from any other float value, including itself; while com‐
243 pare treats nan as equal to itself and less than any other float value.
244 This treatment of nan ensures that compare defines a total ordering re‐
245 lation.
246 compare applied to functional values may raise Invalid_argument . com‐
249 pare applied to cyclic structures may not terminate.
250 The compare function can be used as the comparison function required by
252 the Set.Make and Map.Make functors, as well as the List.sort and Ar‐
253 ray.sort functions.
254 val min : 'a -> 'a -> 'a
258 Return the smaller of the two arguments. The result is unspecified if
260 one of the arguments contains the float value nan .
261 val max : 'a -> 'a -> 'a
265 Return the greater of the two arguments. The result is unspecified if
267 one of the arguments contains the float value nan .
268 val (==) : 'a -> 'a -> bool
272 e1 == e2 tests for physical equality of e1 and e2 . On mutable types
275 such as references, arrays, byte sequences, records with mutable fields
276 and objects with mutable instance variables, e1 == e2 is true if and
277 only if physical modification of e1 also affects e2 . On non-mutable
278 types, the behavior of ( == ) is implementation-dependent; however, it
279 is guaranteed that e1 == e2 implies compare e1 e2 = 0 . Left-associa‐
280 tive operator, see Ocaml_operators for more information.
281 val (!=) : 'a -> 'a -> bool
285 Negation of (==) . Left-associative operator, see Ocaml_operators for
287 more information.
288 Boolean operations
293 val not : bool -> bool
294 The boolean negation.
296 val (&&) : bool -> bool -> bool
300 The boolean 'and'. Evaluation is sequential, left-to-right: in e1 && e2
302 , e1 is evaluated first, and if it returns false , e2 is not evaluated
303 at all. Right-associative operator, see Ocaml_operators for more in‐
304 formation.
305 val (&) : bool -> bool -> bool
309 Deprecated.
311 (&&) should be used instead. Right-associative operator, see Ocaml_op‐
313 erators for more information.
314 val (||) : bool -> bool -> bool
318 The boolean 'or'. Evaluation is sequential, left-to-right: in e1 || e2
320 , e1 is evaluated first, and if it returns true , e2 is not evaluated
321 at all. Right-associative operator, see Ocaml_operators for more in‐
322 formation.
323 val (or) : bool -> bool -> bool
327 Deprecated.
329 (||) should be used instead. Right-associative operator, see Ocaml_op‐
331 erators for more information.
332 Debugging
337 val __LOC__ : string
338 __LOC__ returns the location at which this expression appears in the
341 file currently being parsed by the compiler, with the standard error
342 format of OCaml: "File %S, line %d, characters %d-%d".
343 Since 4.02.0
346 val __FILE__ : string
350 __FILE__ returns the name of the file currently being parsed by the
353 compiler.
354 Since 4.02.0
357 val __LINE__ : int
361 __LINE__ returns the line number at which this expression appears in
364 the file currently being parsed by the compiler.
365 Since 4.02.0
368 val __MODULE__ : string
372 __MODULE__ returns the module name of the file being parsed by the com‐
375 piler.
376 Since 4.02.0
379 val __POS__ : string * int * int * int
383 __POS__ returns a tuple (file,lnum,cnum,enum) , corresponding to the
386 location at which this expression appears in the file currently being
387 parsed by the compiler. file is the current filename, lnum the line
388 number, cnum the character position in the line and enum the last char‐
389 acter position in the line.
390 Since 4.02.0
393 val __LOC_OF__ : 'a -> string * 'a
397 __LOC_OF__ expr returns a pair (loc, expr) where loc is the location of
400 expr in the file currently being parsed by the compiler, with the stan‐
401 dard error format of OCaml: "File %S, line %d, characters %d-%d".
402 Since 4.02.0
405 val __LINE_OF__ : 'a -> int * 'a
409 __LINE_OF__ expr returns a pair (line, expr) , where line is the line
412 number at which the expression expr appears in the file currently being
413 parsed by the compiler.
414 Since 4.02.0
417 val __POS_OF__ : 'a -> (string * int * int * int) * 'a
421 __POS_OF__ expr returns a pair (loc,expr) , where loc is a tuple
424 (file,lnum,cnum,enum) corresponding to the location at which the ex‐
425 pression expr appears in the file currently being parsed by the com‐
426 piler. file is the current filename, lnum the line number, cnum the
427 character position in the line and enum the last character position in
428 the line.
429 Since 4.02.0
432 Composition operators
437 val (|>) : 'a -> ('a -> 'b) -> 'b
438 Reverse-application operator: x |> f |> g is exactly equivalent to g (f
440 (x)) . Left-associative operator, see Ocaml_operators for more infor‐
441 mation.
442 Since 4.01
445 val (@@) : ('a -> 'b) -> 'a -> 'b
449 Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
451 Right-associative operator, see Ocaml_operators for more information.
452 Since 4.01
455 Integer arithmetic
460 Integers are Sys.int_size bits wide. All operations are taken modulo
461 2^ Sys.int_size . They do not fail on overflow.
462 val (~-) : int -> int
464 Unary negation. You can also write - e instead of ~- e . Unary opera‐
466 tor, see Ocaml_operators for more information.
467 val (~+) : int -> int
471 Unary addition. You can also write + e instead of ~+ e . Unary opera‐
473 tor, see Ocaml_operators for more information.
474 Since 3.12.0
477 val succ : int -> int
481 succ x is x + 1 .
484 val pred : int -> int
488 pred x is x - 1 .
491 val (+) : int -> int -> int
495 Integer addition. Left-associative operator, see Ocaml_operators for
497 more information.
498 val (-) : int -> int -> int
502 Integer subtraction. Left-associative operator, , see Ocaml_operators
504 for more information.
505 val ( * ) : int -> int -> int
509 Integer multiplication. Left-associative operator, see Ocaml_operators
511 for more information.
512 val (/) : int -> int -> int
516 Integer division. Integer division rounds the real quotient of its ar‐
518 guments towards zero. More precisely, if x >= 0 and y > 0 , x / y is
519 the greatest integer less than or equal to the real quotient of x by y
520 . Moreover, (- x) / y = x / (- y) = - (x / y) . Left-associative op‐
521 erator, see Ocaml_operators for more information.
522 Raises Division_by_zero if the second argument is 0.
525 val (mod) : int -> int -> int
529 Integer remainder. If y is not zero, the result of x mod y satisfies
531 the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
532 abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
533 mod y is negative only if x < 0 . Left-associative operator, see
534 Ocaml_operators for more information.
535 Raises Division_by_zero if y is zero.
538 val abs : int -> int
542 Return the absolute value of the argument. Note that this may be nega‐
544 tive if the argument is min_int .
545 val max_int : int
549 The greatest representable integer.
551 val min_int : int
555 The smallest representable integer.
557 Bitwise operations
562 val (land) : int -> int -> int
563 Bitwise logical and. Left-associative operator, see Ocaml_operators
565 for more information.
566 val (lor) : int -> int -> int
570 Bitwise logical or. Left-associative operator, see Ocaml_operators for
572 more information.
573 val (lxor) : int -> int -> int
577 Bitwise logical exclusive or. Left-associative operator, see Ocaml_op‐
579 erators for more information.
580 val lnot : int -> int
584 Bitwise logical negation.
586 val (lsl) : int -> int -> int
590 n lsl m shifts n to the left by m bits. The result is unspecified if m
593 < 0 or m > Sys.int_size . Right-associative operator, see Ocaml_opera‐
594 tors for more information.
595 val (lsr) : int -> int -> int
599 n lsr m shifts n to the right by m bits. This is a logical shift: ze‐
602 roes are inserted regardless of the sign of n . The result is unspeci‐
603 fied if m < 0 or m > Sys.int_size . Right-associative operator, see
604 Ocaml_operators for more information.
605 val (asr) : int -> int -> int
609 n asr m shifts n to the right by m bits. This is an arithmetic shift:
612 the sign bit of n is replicated. The result is unspecified if m < 0 or
613 m > Sys.int_size . Right-associative operator, see Ocaml_operators for
614 more information.
615 Floating-point arithmetic
620 OCaml's floating-point numbers follow the IEEE 754 standard, using dou‐
621 ble precision (64 bits) numbers. Floating-point operations never raise
622 an exception on overflow, underflow, division by zero, etc. Instead,
623 special IEEE numbers are returned as appropriate, such as infinity for
624 1.0 /. 0.0 , neg_infinity for -1.0 /. 0.0 , and nan ('not a number')
625 for 0.0 /. 0.0 . These special numbers then propagate through float‐
626 ing-point computations as expected: for instance, 1.0 /. infinity is
627 0.0 , and any arithmetic operation with nan as argument returns nan as
628 result.
629 val (~-.) : float -> float
631 Unary negation. You can also write -. e instead of ~-. e . Unary oper‐
633 ator, see Ocaml_operators for more information.
634 val (~+.) : float -> float
638 Unary addition. You can also write +. e instead of ~+. e . Unary oper‐
640 ator, see Ocaml_operators for more information.
641 Since 3.12.0
644 val (+.) : float -> float -> float
648 Floating-point addition. Left-associative operator, see Ocaml_opera‐
650 tors for more information.
651 val (-.) : float -> float -> float
655 Floating-point subtraction. Left-associative operator, see Ocaml_oper‐
657 ators for more information.
658 val ( *. ) : float -> float -> float
662 Floating-point multiplication. Left-associative operator, see
664 Ocaml_operators for more information.
665 val (/.) : float -> float -> float
669 Floating-point division. Left-associative operator, see Ocaml_opera‐
671 tors for more information.
672 val ( ** ) : float -> float -> float
676 Exponentiation. Right-associative operator, see Ocaml_operators for
678 more information.
679 val sqrt : float -> float
683 Square root.
685 val exp : float -> float
689 Exponential.
691 val log : float -> float
695 Natural logarithm.
697 val log10 : float -> float
701 Base 10 logarithm.
703 val expm1 : float -> float
707 expm1 x computes exp x -. 1.0 , giving numerically-accurate results
710 even if x is close to 0.0 .
711 Since 3.12.0
714 val log1p : float -> float
718 log1p x computes log(1.0 +. x) (natural logarithm), giving numeri‐
721 cally-accurate results even if x is close to 0.0 .
722 Since 3.12.0
725 val cos : float -> float
729 Cosine. Argument is in radians.
731 val sin : float -> float
735 Sine. Argument is in radians.
737 val tan : float -> float
741 Tangent. Argument is in radians.
743 val acos : float -> float
747 Arc cosine. The argument must fall within the range [-1.0, 1.0] . Re‐
749 sult is in radians and is between 0.0 and pi .
750 val asin : float -> float
754 Arc sine. The argument must fall within the range [-1.0, 1.0] . Re‐
756 sult is in radians and is between -pi/2 and pi/2 .
757 val atan : float -> float
761 Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
763 val atan2 : float -> float -> float
767 atan2 y x returns the arc tangent of y /. x . The signs of x and y are
770 used to determine the quadrant of the result. Result is in radians and
771 is between -pi and pi .
772 val hypot : float -> float -> float
776 hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
779 hypotenuse of a right-angled triangle with sides of length x and y ,
780 or, equivalently, the distance of the point (x,y) to origin. If one of
781 x or y is infinite, returns infinity even if the other is nan .
782 Since 4.00.0
785 val cosh : float -> float
789 Hyperbolic cosine. Argument is in radians.
791 val sinh : float -> float
795 Hyperbolic sine. Argument is in radians.
797 val tanh : float -> float
801 Hyperbolic tangent. Argument is in radians.
803 val ceil : float -> float
807 Round above to an integer value. ceil f returns the least integer
809 value greater than or equal to f . The result is returned as a float.
810 val floor : float -> float
814 Round below to an integer value. floor f returns the greatest integer
816 value less than or equal to f . The result is returned as a float.
817 val abs_float : float -> float
821 abs_float f returns the absolute value of f .
824 val copysign : float -> float -> float
828 copysign x y returns a float whose absolute value is that of x and
831 whose sign is that of y . If x is nan , returns nan . If y is nan ,
832 returns either x or -. x , but it is not specified which.
833 Since 4.00.0
836 val mod_float : float -> float -> float
840 mod_float a b returns the remainder of a with respect to b . The re‐
843 turned value is a -. n *. b , where n is the quotient a /. b rounded
844 towards zero to an integer.
845 val frexp : float -> float * int
849 frexp f returns the pair of the significant and the exponent of f .
852 When f is zero, the significant x and the exponent n of f are equal to
853 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
854 <= x < 1.0 .
855 val ldexp : float -> int -> float
859 ldexp x n returns x *. 2 ** n .
862 val modf : float -> float * float
866 modf f returns the pair of the fractional and integral part of f .
869 val float : int -> float
873 Same as float_of_int .
875 val float_of_int : int -> float
879 Convert an integer to floating-point.
881 val truncate : float -> int
885 Same as int_of_float .
887 val int_of_float : float -> int
891 Truncate the given floating-point number to an integer. The result is
893 unspecified if the argument is nan or falls outside the range of repre‐
894 sentable integers.
895 val infinity : float
899 Positive infinity.
901 val neg_infinity : float
905 Negative infinity.
907 val nan : float
911 A special floating-point value denoting the result of an undefined op‐
913 eration such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
914 ing-point operation with nan as argument returns nan as result. As for
915 floating-point comparisons, = , < , <= , > and >= return false and <>
916 returns true if one or both of their arguments is nan .
917 val max_float : float
921 The largest positive finite value of type float .
923 val min_float : float
927 The smallest positive, non-zero, non-denormalized value of type float .
929 val epsilon_float : float
933 The difference between 1.0 and the smallest exactly representable
935 floating-point number greater than 1.0 .
936 type fpclass =
939 | FP_normal (* Normal number, none of the below
940 *)
941 | FP_subnormal (* Number very close to 0.0, has reduced precision
942 *)
943 | FP_zero (* Number is 0.0 or -0.0
944 *)
945 | FP_infinite (* Number is positive or negative infinity
946 *)
947 | FP_nan (* Not a number: result of an undefined operation
948 *)
949 The five classes of floating-point numbers, as determined by the clas‐
952 sify_float function.
953 val classify_float : float -> fpclass
957 Return the class of the given floating-point number: normal, subnormal,
959 zero, infinite, or not a number.
960 String operations
965 More string operations are provided in module String .
966 val (^) : string -> string -> string
968 String concatenation. Right-associative operator, see Ocaml_operators
970 for more information.
971 Character operations
976 More character operations are provided in module Char .
977 val int_of_char : char -> int
979 Return the ASCII code of the argument.
981 val char_of_int : int -> char
985 Return the character with the given ASCII code.
987 Raises Invalid_argument if the argument is outside the range 0--255.
990 Unit operations
995 val ignore : 'a -> unit
996 Discard the value of its argument and return () . For instance, ig‐
998 nore(f x) discards the result of the side-effecting function f . It is
999 equivalent to f x; () , except that the latter may generate a compiler
1000 warning; writing ignore(f x) instead avoids the warning.
1001 String conversion functions
1006 val string_of_bool : bool -> string
1007 Return the string representation of a boolean. As the returned values
1009 may be shared, the user should not modify them directly.
1010 val bool_of_string_opt : string -> bool option
1014 Convert the given string to a boolean.
1016 Return None if the string is not "true" or "false" .
1018 Since 4.05
1021 val bool_of_string : string -> bool
1025 Same as bool_of_string_opt , but raise Invalid_argument
1027 "bool_of_string" instead of returning None .
1028 val string_of_int : int -> string
1032 Return the string representation of an integer, in decimal.
1034 val int_of_string_opt : string -> int option
1038 Convert the given string to an integer. The string is read in decimal
1040 (by default, or if the string begins with 0u ), in hexadecimal (if it
1041 begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
1042 binary (if it begins with 0b or 0B ).
1043 The 0u prefix reads the input as an unsigned integer in the range [0,
1045 2*max_int+1] . If the input exceeds max_int it is converted to the
1046 signed integer min_int + input - max_int - 1 .
1047 The _ (underscore) character can appear anywhere in the string and is
1049 ignored.
1050 Return None if the given string is not a valid representation of an in‐
1052 teger, or if the integer represented exceeds the range of integers rep‐
1053 resentable in type int .
1054 Since 4.05
1057 val int_of_string : string -> int
1061 Same as int_of_string_opt , but raise Failure "int_of_string" instead
1063 of returning None .
1064 val string_of_float : float -> string
1068 Return the string representation of a floating-point number.
1070 val float_of_string_opt : string -> float option
1074 Convert the given string to a float. The string is read in decimal (by
1076 default) or in hexadecimal (marked by 0x or 0X ).
1077 The format of decimal floating-point numbers is [-] dd.ddd (e|E) [+|-]
1079 dd , where d stands for a decimal digit.
1080 The format of hexadecimal floating-point numbers is [-] 0(x|X) hh.hhh
1082 (p|P) [+|-] dd , where h stands for an hexadecimal digit and d for a
1083 decimal digit.
1084 In both cases, at least one of the integer and fractional parts must be
1086 given; the exponent part is optional.
1087 The _ (underscore) character can appear anywhere in the string and is
1089 ignored.
1090 Depending on the execution platforms, other representations of float‐
1092 ing-point numbers can be accepted, but should not be relied upon.
1093 Return None if the given string is not a valid representation of a
1095 float.
1096 Since 4.05
1099 val float_of_string : string -> float
1103 Same as float_of_string_opt , but raise Failure "float_of_string" in‐
1105 stead of returning None .
1106 Pair operations
1111 val fst : 'a * 'b -> 'a
1112 Return the first component of a pair.
1114 val snd : 'a * 'b -> 'b
1118 Return the second component of a pair.
1120 List operations
1125 More list operations are provided in module List .
1126 val (@) : 'a list -> 'a list -> 'a list
1128 List concatenation. Not tail-recursive (length of the first argument).
1130 Right-associative operator, see Ocaml_operators for more information.
1131 Input/output
1136 Note: all input/output functions can raise Sys_error when the system
1137 calls they invoke fail.
1138 type in_channel
1140 The type of input channel.
1143 type out_channel
1146 The type of output channel.
1149 val stdin : in_channel
1153 The standard input for the process.
1155 val stdout : out_channel
1159 The standard output for the process.
1161 val stderr : out_channel
1165 The standard error output for the process.
1167 Output functions on standard output
1172 val print_char : char -> unit
1173 Print a character on standard output.
1175 val print_string : string -> unit
1179 Print a string on standard output.
1181 val print_bytes : bytes -> unit
1185 Print a byte sequence on standard output.
1187 Since 4.02.0
1190 val print_int : int -> unit
1194 Print an integer, in decimal, on standard output.
1196 val print_float : float -> unit
1200 Print a floating-point number, in decimal, on standard output.
1202 val print_endline : string -> unit
1206 Print a string, followed by a newline character, on standard output and
1208 flush standard output.
1209 val print_newline : unit -> unit
1213 Print a newline character on standard output, and flush standard out‐
1215 put. This can be used to simulate line buffering of standard output.
1216 Output functions on standard error
1221 val prerr_char : char -> unit
1222 Print a character on standard error.
1224 val prerr_string : string -> unit
1228 Print a string on standard error.
1230 val prerr_bytes : bytes -> unit
1234 Print a byte sequence on standard error.
1236 Since 4.02.0
1239 val prerr_int : int -> unit
1243 Print an integer, in decimal, on standard error.
1245 val prerr_float : float -> unit
1249 Print a floating-point number, in decimal, on standard error.
1251 val prerr_endline : string -> unit
1255 Print a string, followed by a newline character on standard error and
1257 flush standard error.
1258 val prerr_newline : unit -> unit
1262 Print a newline character on standard error, and flush standard error.
1264 Input functions on standard input
1269 val read_line : unit -> string
1270 Flush standard output, then read characters from standard input until a
1272 newline character is encountered. Return the string of all characters
1273 read, without the newline character at the end.
1274 val read_int_opt : unit -> int option
1278 Flush standard output, then read one line from standard input and con‐
1280 vert it to an integer.
1281 Return None if the line read is not a valid representation of an inte‐
1283 ger.
1284 Since 4.05
1287 val read_int : unit -> int
1291 Same as read_int_opt , but raise Failure "int_of_string" instead of re‐
1293 turning None .
1294 val read_float_opt : unit -> float option
1298 Flush standard output, then read one line from standard input and con‐
1300 vert it to a floating-point number.
1301 Return None if the line read is not a valid representation of a float‐
1303 ing-point number.
1304 Since 4.05.0
1307 val read_float : unit -> float
1311 Same as read_float_opt , but raise Failure "float_of_string" instead of
1313 returning None .
1314 General output functions
1319 type open_flag =
1320 | Open_rdonly (* open for reading.
1321 *)
1322 | Open_wronly (* open for writing.
1323 *)
1324 | Open_append (* open for appending: always write at end of file.
1325 *)
1326 | Open_creat (* create the file if it does not exist.
1327 *)
1328 | Open_trunc (* empty the file if it already exists.
1329 *)
1330 | Open_excl (* fail if Open_creat and the file already exists.
1331 *)
1332 | Open_binary (* open in binary mode (no conversion).
1333 *)
1334 | Open_text (* open in text mode (may perform conversions).
1335 *)
1336 | Open_nonblock (* open in non-blocking mode.
1337 *)
1338 Opening modes for open_out_gen and open_in_gen .
1341 val open_out : string -> out_channel
1345 Open the named file for writing, and return a new output channel on
1347 that file, positioned at the beginning of the file. The file is trun‐
1348 cated to zero length if it already exists. It is created if it does not
1349 already exists.
1350 val open_out_bin : string -> out_channel
1354 Same as open_out , but the file is opened in binary mode, so that no
1356 translation takes place during writes. On operating systems that do not
1357 distinguish between text mode and binary mode, this function behaves
1358 like open_out .
1359 val open_out_gen : open_flag list -> int -> string -> out_channel
1363 open_out_gen mode perm filename opens the named file for writing, as
1366 described above. The extra argument mode specifies the opening mode.
1367 The extra argument perm specifies the file permissions, in case the
1368 file must be created. open_out and open_out_bin are special cases of
1369 this function.
1370 val flush : out_channel -> unit
1374 Flush the buffer associated with the given output channel, performing
1376 all pending writes on that channel. Interactive programs must be care‐
1377 ful about flushing standard output and standard error at the right
1378 time.
1379 val flush_all : unit -> unit
1383 Flush all open output channels; ignore errors.
1385 val output_char : out_channel -> char -> unit
1389 Write the character on the given output channel.
1391 val output_string : out_channel -> string -> unit
1395 Write the string on the given output channel.
1397 val output_bytes : out_channel -> bytes -> unit
1401 Write the byte sequence on the given output channel.
1403 Since 4.02.0
1406 val output : out_channel -> bytes -> int -> int -> unit
1410 output oc buf pos len writes len characters from byte sequence buf ,
1413 starting at offset pos , to the given output channel oc .
1414 Raises Invalid_argument if pos and len do not designate a valid range
1417 of buf .
1418 val output_substring : out_channel -> string -> int -> int -> unit
1422 Same as output but take a string as argument instead of a byte se‐
1424 quence.
1425 Since 4.02.0
1428 val output_byte : out_channel -> int -> unit
1432 Write one 8-bit integer (as the single character with that code) on the
1434 given output channel. The given integer is taken modulo 256.
1435 val output_binary_int : out_channel -> int -> unit
1439 Write one integer in binary format (4 bytes, big-endian) on the given
1441 output channel. The given integer is taken modulo 2^32. The only re‐
1442 liable way to read it back is through the input_binary_int function.
1443 The format is compatible across all machines for a given version of
1444 OCaml.
1445 val output_value : out_channel -> 'a -> unit
1449 Write the representation of a structured value of any type to a chan‐
1451 nel. Circularities and sharing inside the value are detected and pre‐
1452 served. The object can be read back, by the function input_value . See
1453 the description of module Marshal for more information. output_value
1454 is equivalent to Marshal.to_channel with an empty list of flags.
1455 val seek_out : out_channel -> int -> unit
1459 seek_out chan pos sets the current writing position to pos for channel
1462 chan . This works only for regular files. On files of other kinds (such
1463 as terminals, pipes and sockets), the behavior is unspecified.
1464 val pos_out : out_channel -> int
1468 Return the current writing position for the given channel. Does not
1470 work on channels opened with the Open_append flag (returns unspecified
1471 results).
1472 val out_channel_length : out_channel -> int
1476 Return the size (number of characters) of the regular file on which the
1478 given channel is opened. If the channel is opened on a file that is
1479 not a regular file, the result is meaningless.
1480 val close_out : out_channel -> unit
1484 Close the given channel, flushing all buffered write operations. Out‐
1486 put functions raise a Sys_error exception when they are applied to a
1487 closed output channel, except close_out and flush , which do nothing
1488 when applied to an already closed channel. Note that close_out may
1489 raise Sys_error if the operating system signals an error when flushing
1490 or closing.
1491 val close_out_noerr : out_channel -> unit
1495 Same as close_out , but ignore all errors.
1497 val set_binary_mode_out : out_channel -> bool -> unit
1501 set_binary_mode_out oc true sets the channel oc to binary mode: no
1504 translations take place during output. set_binary_mode_out oc false
1505 sets the channel oc to text mode: depending on the operating system,
1506 some translations may take place during output. For instance, under
1507 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1508 tion has no effect under operating systems that do not distinguish be‐
1509 tween text mode and binary mode.
1510 General input functions
1515 val open_in : string -> in_channel
1516 Open the named file for reading, and return a new input channel on that
1518 file, positioned at the beginning of the file.
1519 val open_in_bin : string -> in_channel
1523 Same as open_in , but the file is opened in binary mode, so that no
1525 translation takes place during reads. On operating systems that do not
1526 distinguish between text mode and binary mode, this function behaves
1527 like open_in .
1528 val open_in_gen : open_flag list -> int -> string -> in_channel
1532 open_in_gen mode perm filename opens the named file for reading, as de‐
1535 scribed above. The extra arguments mode and perm specify the opening
1536 mode and file permissions. open_in and open_in_bin are special cases
1537 of this function.
1538 val input_char : in_channel -> char
1542 Read one character from the given input channel.
1544 Raises End_of_file if there are no more characters to read.
1547 val input_line : in_channel -> string
1551 Read characters from the given input channel, until a newline character
1553 is encountered. Return the string of all characters read, without the
1554 newline character at the end.
1555 Raises End_of_file if the end of the file is reached at the beginning
1558 of line.
1559 val input : in_channel -> bytes -> int -> int -> int
1563 input ic buf pos len reads up to len characters from the given channel
1566 ic , storing them in byte sequence buf , starting at character number
1567 pos . It returns the actual number of characters read, between 0 and
1568 len (inclusive). A return value of 0 means that the end of file was
1569 reached. A return value between 0 and len exclusive means that not all
1570 requested len characters were read, either because no more characters
1571 were available at that time, or because the implementation found it
1572 convenient to do a partial read; input must be called again to read the
1573 remaining characters, if desired. (See also really_input for reading
1574 exactly len characters.) Exception Invalid_argument "input" is raised
1575 if pos and len do not designate a valid range of buf .
1576 val really_input : in_channel -> bytes -> int -> int -> unit
1580 really_input ic buf pos len reads len characters from channel ic ,
1583 storing them in byte sequence buf , starting at character number pos .
1584 Raises End_of_file if the end of file is reached before len characters
1587 have been read.
1588 Raises Invalid_argument if pos and len do not designate a valid range
1591 of buf .
1592 val really_input_string : in_channel -> int -> string
1596 really_input_string ic len reads len characters from channel ic and re‐
1599 turns them in a new string.
1600 Since 4.02.0
1603 Raises End_of_file if the end of file is reached before len characters
1606 have been read.
1607 val input_byte : in_channel -> int
1611 Same as input_char , but return the 8-bit integer representing the
1613 character.
1614 Raises End_of_file if an end of file was reached.
1617 val input_binary_int : in_channel -> int
1621 Read an integer encoded in binary format (4 bytes, big-endian) from the
1623 given input channel. See output_binary_int .
1624 Raises End_of_file if an end of file was reached while reading the in‐
1627 teger.
1628 val input_value : in_channel -> 'a
1632 Read the representation of a structured value, as produced by out‐
1634 put_value , and return the corresponding value. This function is iden‐
1635 tical to Marshal.from_channel ; see the description of module Marshal
1636 for more information, in particular concerning the lack of type safety.
1637 val seek_in : in_channel -> int -> unit
1641 seek_in chan pos sets the current reading position to pos for channel
1644 chan . This works only for regular files. On files of other kinds, the
1645 behavior is unspecified.
1646 val pos_in : in_channel -> int
1650 Return the current reading position for the given channel.
1652 val in_channel_length : in_channel -> int
1656 Return the size (number of characters) of the regular file on which the
1658 given channel is opened. If the channel is opened on a file that is
1659 not a regular file, the result is meaningless. The returned size does
1660 not take into account the end-of-line translations that can be per‐
1661 formed when reading from a channel opened in text mode.
1662 val close_in : in_channel -> unit
1666 Close the given channel. Input functions raise a Sys_error exception
1668 when they are applied to a closed input channel, except close_in ,
1669 which does nothing when applied to an already closed channel.
1670 val close_in_noerr : in_channel -> unit
1674 Same as close_in , but ignore all errors.
1676 val set_binary_mode_in : in_channel -> bool -> unit
1680 set_binary_mode_in ic true sets the channel ic to binary mode: no
1683 translations take place during input. set_binary_mode_out ic false
1684 sets the channel ic to text mode: depending on the operating system,
1685 some translations may take place during input. For instance, under
1686 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1687 tion has no effect under operating systems that do not distinguish be‐
1688 tween text mode and binary mode.
1689 Operations on large files
1694 module LargeFile : sig end
1695 Operations on large files. This sub-module provides 64-bit variants of
1698 the channel functions that manipulate file positions and file sizes.
1699 By representing positions and sizes by 64-bit integers (type int64 )
1700 instead of regular integers (type int ), these alternate functions al‐
1701 low operating on files whose sizes are greater than max_int .
1702 References
1707 type 'a ref = {
1708 mutable contents : 'a ;
1710 }
1711 The type of references (mutable indirection cells) containing a value
1714 of type 'a .
1715 val ref : 'a -> 'a ref
1719 Return a fresh reference containing the given value.
1721 val (!) : 'a ref -> 'a
1725 !r returns the current contents of reference r . Equivalent to fun r
1728 -> r.contents . Unary operator, see Ocaml_operators for more informa‐
1729 tion.
1730 val (:=) : 'a ref -> 'a -> unit
1734 r := a stores the value of a in reference r . Equivalent to fun r v ->
1737 r.contents <- v . Right-associative operator, see Ocaml_operators for
1738 more information.
1739 val incr : int ref -> unit
1743 Increment the integer contained in the given reference. Equivalent to
1745 fun r -> r := succ !r .
1746 val decr : int ref -> unit
1750 Decrement the integer contained in the given reference. Equivalent to
1752 fun r -> r := pred !r .
1753 Result type
1758 type ('a, 'b) result =
1759 | Ok of 'a
1760 | Error of 'b
1761 Since 4.03.0
1764 Operations on format strings
1769 Format strings are character strings with special lexical conventions
1770 that defines the functionality of formatted input/output functions.
1771 Format strings are used to read data with formatted input functions
1772 from module Scanf and to print data with formatted output functions
1773 from modules Printf and Format .
1774 Format strings are made of three kinds of entities:
1776 -conversions specifications, introduced by the special character '%'
1778 followed by one or more characters specifying what kind of argument to
1779 read or print,
1780 -formatting indications, introduced by the special character '@' fol‐
1782 lowed by one or more characters specifying how to read or print the ar‐
1783 gument,
1784 -plain characters that are regular characters with usual lexical con‐
1786 ventions. Plain characters specify string literals to be read in the
1787 input or printed in the output.
1788 There is an additional lexical rule to escape the special characters
1790 '%' and '@' in format strings: if a special character follows a '%'
1791 character, it is treated as a plain character. In other words, "%%" is
1792 considered as a plain '%' and "%@" as a plain '@' .
1793 For more information about conversion specifications and formatting in‐
1795 dications available, read the documentation of modules Scanf , Printf
1796 and Format .
1797 Format strings have a general and highly polymorphic type ('a, 'b, 'c,
1799 'd, 'e, 'f) format6 . The two simplified types, format and format4 be‐
1800 low are included for backward compatibility with earlier releases of
1801 OCaml.
1802 The meaning of format string type parameters is as follows:
1804 - 'a is the type of the parameters of the format for formatted output
1807 functions ( printf -style functions); 'a is the type of the values read
1808 by the format for formatted input functions ( scanf -style functions).
1809 - 'b is the type of input source for formatted input functions and the
1812 type of output target for formatted output functions. For printf
1813 -style functions from module Printf , 'b is typically out_channel ; for
1814 printf -style functions from module Format , 'b is typically For‐
1815 mat.formatter ; for scanf -style functions from module Scanf , 'b is
1816 typically Scanf.Scanning.in_channel .
1817 Type argument 'b is also the type of the first argument given to user's
1819 defined printing functions for %a and %t conversions, and user's de‐
1820 fined reading functions for %r conversion.
1821 - 'c is the type of the result of the %a and %t printing functions, and
1824 also the type of the argument transmitted to the first argument of
1825 kprintf -style functions or to the kscanf -style functions.
1826 - 'd is the type of parameters for the scanf -style functions.
1829 - 'e is the type of the receiver function for the scanf -style func‐
1832 tions.
1833 - 'f is the final result type of a formatted input/output function in‐
1836 vocation: for the printf -style functions, it is typically unit ; for
1837 the scanf -style functions, it is typically the result type of the re‐
1838 ceiver function.
1839 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1842 linternalFormatBasics.format6
1843 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1848 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1853 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1859 Converts a format string into a string.
1861 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1865 'd, 'e, 'f) format6
1866 format_of_string s returns a format string read from the string literal
1869 s . Note: format_of_string can not convert a string argument that is
1870 not a literal. If you need this functionality, use the more general
1871 Scanf.format_from_string function.
1872 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1876 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1877 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1880 string that behaves as the concatenation of format strings f1 and f2 :
1881 in case of formatted output, it accepts arguments from f1 , then argu‐
1882 ments from f2 ; in case of formatted input, it returns results from f1
1883 , then results from f2 . Right-associative operator, see Ocaml_opera‐
1884 tors for more information.
1885 Program termination
1890 val exit : int -> 'a
1891 Terminate the process, returning the given status code to the operating
1893 system: usually 0 to indicate no errors, and a small positive integer
1894 to indicate failure. All open output channels are flushed with
1895 flush_all . An implicit exit 0 is performed each time a program termi‐
1896 nates normally. An implicit exit 2 is performed if the program termi‐
1897 nates early because of an uncaught exception.
1898 val at_exit : (unit -> unit) -> unit
1902 Register the given function to be called at program termination time.
1904 The functions registered with at_exit will be called when the program
1905 does any of the following:
1906 -executes exit
1908 -terminates, either normally or because of an uncaught exception
1911 -executes the C function caml_shutdown . The functions are called in
1913 'last in, first out' order: the function most recently added with
1914 at_exit is called first.
1915 Standard library modules
1921 module Arg : (module Stdlib__arg)
1922 module Array : (module Stdlib__array)
1927 module ArrayLabels : (module Stdlib__arrayLabels)
1932 module Bigarray : (module Stdlib__bigarray)
1937 module Bool : (module Stdlib__bool)
1942 module Buffer : (module Stdlib__buffer)
1947 module Bytes : (module Stdlib__bytes)
1952 module BytesLabels : (module Stdlib__bytesLabels)
1957 module Callback : (module Stdlib__callback)
1962 module Char : (module Stdlib__char)
1967 module Complex : (module Stdlib__complex)
1972 module Digest : (module Stdlib__digest)
1977 module Ephemeron : (module Stdlib__ephemeron)
1982 module Filename : (module Stdlib__filename)
1987 module Float : (module Stdlib__float)
1992 module Format : (module Stdlib__format)
1997 module Fun : (module Stdlib__fun)
2002 module Gc : (module Stdlib__gc)
2007 module Genlex : (module Stdlib__genlex)
2012 module Hashtbl : (module Stdlib__hashtbl)
2017 module Int : (module Stdlib__int)
2022 module Int32 : (module Stdlib__int32)
2027 module Int64 : (module Stdlib__int64)
2032 module Lazy : (module Stdlib__lazy)
2037 module Lexing : (module Stdlib__lexing)
2042 module List : (module Stdlib__list)
2047 module ListLabels : (module Stdlib__listLabels)
2052 module Map : (module Stdlib__map)
2057 module Marshal : (module Stdlib__marshal)
2062 module MoreLabels : (module Stdlib__moreLabels)
2067 module Nativeint : (module Stdlib__nativeint)
2072 module Obj : (module Stdlib__obj)
2077 module Oo : (module Stdlib__oo)
2082 module Option : (module Stdlib__option)
2087 module Parsing : (module Stdlib__parsing)
2092 module Pervasives : (module Stdlib__pervasives)
2097 module Printexc : (module Stdlib__printexc)
2102 module Printf : (module Stdlib__printf)
2107 module Queue : (module Stdlib__queue)
2112 module Random : (module Stdlib__random)
2117 module Result : (module Stdlib__result)
2122 module Scanf : (module Stdlib__scanf)
2127 module Seq : (module Stdlib__seq)
2132 module Set : (module Stdlib__set)
2137 module Spacetime : (module Stdlib__spacetime)
2142 module Stack : (module Stdlib__stack)
2147 module StdLabels : (module Stdlib__stdLabels)
2152 module Stream : (module Stdlib__stream)
2157 module String : (module Stdlib__string)
2162 module StringLabels : (module Stdlib__stringLabels)
2167 module Sys : (module Stdlib__sys)
2172 module Uchar : (module Stdlib__uchar)
2177 module Unit : (module Stdlib__unit)
2182 module Weak : (module Stdlib__weak)
2187OCamldoc 2021-01-26 Stdlib(3)