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. (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
203 information.
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
239 ordering implemented by compare is compatible with the comparison pred‐
240 icates = , < 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
245 relation.
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
253 Array.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
304 information.
305 val (&) : bool -> bool -> bool
309 Deprecated.
311 (&&) should be used instead. Right-associative operator, see
313 Ocaml_operators 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
322 information.
323 val (or) : bool -> bool -> bool
327 Deprecated.
329 (||) should be used instead. Right-associative operator, see
331 Ocaml_operators 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
425 expression 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. Raise Division_by_zero if the second argument is 0.
518 Integer division rounds the real quotient of its arguments towards
519 zero. More precisely, if x >= 0 and y > 0 , x / y is the greatest
520 integer less than or equal to the real quotient of x by y . Moreover,
521 (- x) / y = x / (- y) = - (x / y) . Left-associative operator, see
522 Ocaml_operators for more information.
523 val (mod) : int -> int -> int
527 Integer remainder. If y is not zero, the result of x mod y satisfies
529 the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
530 abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
531 mod y is negative only if x < 0 . Raise Division_by_zero if y is zero.
532 Left-associative operator, see Ocaml_operators for more information.
533 val abs : int -> int
537 Return the absolute value of the argument. Note that this may be nega‐
539 tive if the argument is min_int .
540 val max_int : int
544 The greatest representable integer.
546 val min_int : int
550 The smallest representable integer.
552 Bitwise operations
557 val (land) : int -> int -> int
558 Bitwise logical and. Left-associative operator, see Ocaml_operators
560 for more information.
561 val (lor) : int -> int -> int
565 Bitwise logical or. Left-associative operator, see Ocaml_operators for
567 more information.
568 val (lxor) : int -> int -> int
572 Bitwise logical exclusive or. Left-associative operator, see
574 Ocaml_operators for more information.
575 val lnot : int -> int
579 Bitwise logical negation.
581 val (lsl) : int -> int -> int
585 n lsl m shifts n to the left by m bits. The result is unspecified if m
588 < 0 or m > Sys.int_size . Right-associative operator, see Ocaml_opera‐
589 tors for more information.
590 val (lsr) : int -> int -> int
594 n lsr m shifts n to the right by m bits. This is a logical shift:
597 zeroes are inserted regardless of the sign of n . The result is
598 unspecified if m < 0 or m > Sys.int_size . Right-associative operator,
599 see Ocaml_operators for more information.
600 val (asr) : int -> int -> int
604 n asr m shifts n to the right by m bits. This is an arithmetic shift:
607 the sign bit of n is replicated. The result is unspecified if m < 0 or
608 m > Sys.int_size . Right-associative operator, see Ocaml_operators for
609 more information.
610 Floating-point arithmetic
615 OCaml's floating-point numbers follow the IEEE 754 standard, using dou‐
616 ble precision (64 bits) numbers. Floating-point operations never raise
617 an exception on overflow, underflow, division by zero, etc. Instead,
618 special IEEE numbers are returned as appropriate, such as infinity for
619 1.0 /. 0.0 , neg_infinity for -1.0 /. 0.0 , and nan ('not a number')
620 for 0.0 /. 0.0 . These special numbers then propagate through float‐
621 ing-point computations as expected: for instance, 1.0 /. infinity is
622 0.0 , and any arithmetic operation with nan as argument returns nan as
623 result.
624 val (~-.) : float -> float
626 Unary negation. You can also write -. e instead of ~-. e . Unary oper‐
628 ator, see Ocaml_operators for more information.
629 val (~+.) : float -> float
633 Unary addition. You can also write +. e instead of ~+. e . Unary oper‐
635 ator, see Ocaml_operators for more information.
636 Since 3.12.0
639 val (+.) : float -> float -> float
643 Floating-point addition. Left-associative operator, see Ocaml_opera‐
645 tors for more information.
646 val (-.) : float -> float -> float
650 Floating-point subtraction. Left-associative operator, see Ocaml_oper‐
652 ators for more information.
653 val ( *. ) : float -> float -> float
657 Floating-point multiplication. Left-associative operator, see
659 Ocaml_operators for more information.
660 val (/.) : float -> float -> float
664 Floating-point division. Left-associative operator, see Ocaml_opera‐
666 tors for more information.
667 val ( ** ) : float -> float -> float
671 Exponentiation. Right-associative operator, see Ocaml_operators for
673 more information.
674 val sqrt : float -> float
678 Square root.
680 val exp : float -> float
684 Exponential.
686 val log : float -> float
690 Natural logarithm.
692 val log10 : float -> float
696 Base 10 logarithm.
698 val expm1 : float -> float
702 expm1 x computes exp x -. 1.0 , giving numerically-accurate results
705 even if x is close to 0.0 .
706 Since 3.12.0
709 val log1p : float -> float
713 log1p x computes log(1.0 +. x) (natural logarithm), giving numeri‐
716 cally-accurate results even if x is close to 0.0 .
717 Since 3.12.0
720 val cos : float -> float
724 Cosine. Argument is in radians.
726 val sin : float -> float
730 Sine. Argument is in radians.
732 val tan : float -> float
736 Tangent. Argument is in radians.
738 val acos : float -> float
742 Arc cosine. The argument must fall within the range [-1.0, 1.0] .
744 Result is in radians and is between 0.0 and pi .
745 val asin : float -> float
749 Arc sine. The argument must fall within the range [-1.0, 1.0] .
751 Result is in radians and is between -pi/2 and pi/2 .
752 val atan : float -> float
756 Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
758 val atan2 : float -> float -> float
762 atan2 y x returns the arc tangent of y /. x . The signs of x and y are
765 used to determine the quadrant of the result. Result is in radians and
766 is between -pi and pi .
767 val hypot : float -> float -> float
771 hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
774 hypotenuse of a right-angled triangle with sides of length x and y ,
775 or, equivalently, the distance of the point (x,y) to origin. If one of
776 x or y is infinite, returns infinity even if the other is nan .
777 Since 4.00.0
780 val cosh : float -> float
784 Hyperbolic cosine. Argument is in radians.
786 val sinh : float -> float
790 Hyperbolic sine. Argument is in radians.
792 val tanh : float -> float
796 Hyperbolic tangent. Argument is in radians.
798 val ceil : float -> float
802 Round above to an integer value. ceil f returns the least integer
804 value greater than or equal to f . The result is returned as a float.
805 val floor : float -> float
809 Round below to an integer value. floor f returns the greatest integer
811 value less than or equal to f . The result is returned as a float.
812 val abs_float : float -> float
816 abs_float f returns the absolute value of f .
819 val copysign : float -> float -> float
823 copysign x y returns a float whose absolute value is that of x and
826 whose sign is that of y . If x is nan , returns nan . If y is nan ,
827 returns either x or -. x , but it is not specified which.
828 Since 4.00.0
831 val mod_float : float -> float -> float
835 mod_float a b returns the remainder of a with respect to b . The
838 returned value is a -. n *. b , where n is the quotient a /. b rounded
839 towards zero to an integer.
840 val frexp : float -> float * int
844 frexp f returns the pair of the significant and the exponent of f .
847 When f is zero, the significant x and the exponent n of f are equal to
848 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
849 <= x < 1.0 .
850 val ldexp : float -> int -> float
854 ldexp x n returns x *. 2 ** n .
857 val modf : float -> float * float
861 modf f returns the pair of the fractional and integral part of f .
864 val float : int -> float
868 Same as float_of_int .
870 val float_of_int : int -> float
874 Convert an integer to floating-point.
876 val truncate : float -> int
880 Same as int_of_float .
882 val int_of_float : float -> int
886 Truncate the given floating-point number to an integer. The result is
888 unspecified if the argument is nan or falls outside the range of repre‐
889 sentable integers.
890 val infinity : float
894 Positive infinity.
896 val neg_infinity : float
900 Negative infinity.
902 val nan : float
906 A special floating-point value denoting the result of an undefined
908 operation such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
909 ing-point operation with nan as argument returns nan as result. As for
910 floating-point comparisons, = , < , <= , > and >= return false and <>
911 returns true if one or both of their arguments is nan .
912 val max_float : float
916 The largest positive finite value of type float .
918 val min_float : float
922 The smallest positive, non-zero, non-denormalized value of type float .
924 val epsilon_float : float
928 The difference between 1.0 and the smallest exactly representable
930 floating-point number greater than 1.0 .
931 type fpclass =
934 | FP_normal (* Normal number, none of the below
935 *)
936 | FP_subnormal (* Number very close to 0.0, has reduced precision
937 *)
938 | FP_zero (* Number is 0.0 or -0.0
939 *)
940 | FP_infinite (* Number is positive or negative infinity
941 *)
942 | FP_nan (* Not a number: result of an undefined operation
943 *)
944 The five classes of floating-point numbers, as determined by the clas‐
947 sify_float function.
948 val classify_float : float -> fpclass
952 Return the class of the given floating-point number: normal, subnormal,
954 zero, infinite, or not a number.
955 String operations
960 More string operations are provided in module String .
961 val (^) : string -> string -> string
963 String concatenation. Right-associative operator, see Ocaml_operators
965 for more information.
966 Character operations
971 More character operations are provided in module Char .
972 val int_of_char : char -> int
974 Return the ASCII code of the argument.
976 val char_of_int : int -> char
980 Return the character with the given ASCII code. Raise Invalid_argument
982 "char_of_int" if the argument is outside the range 0--255.
983 Unit operations
988 val ignore : 'a -> unit
989 Discard the value of its argument and return () . For instance,
991 ignore(f x) discards the result of the side-effecting function f . It
992 is equivalent to f x; () , except that the latter may generate a com‐
993 piler warning; writing ignore(f x) instead avoids the warning.
994 String conversion functions
999 val string_of_bool : bool -> string
1000 Return the string representation of a boolean. As the returned values
1002 may be shared, the user should not modify them directly.
1003 val bool_of_string_opt : string -> bool option
1007 Convert the given string to a boolean.
1009 Return None if the string is not "true" or "false" .
1011 Since 4.05
1014 val bool_of_string : string -> bool
1018 Same as bool_of_string_opt , but raise Invalid_argument
1020 "bool_of_string" instead of returning None .
1021 val string_of_int : int -> string
1025 Return the string representation of an integer, in decimal.
1027 val int_of_string_opt : string -> int option
1031 Convert the given string to an integer. The string is read in decimal
1033 (by default, or if the string begins with 0u ), in hexadecimal (if it
1034 begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
1035 binary (if it begins with 0b or 0B ).
1036 The 0u prefix reads the input as an unsigned integer in the range [0,
1038 2*max_int+1] . If the input exceeds max_int it is converted to the
1039 signed integer min_int + input - max_int - 1 .
1040 The _ (underscore) character can appear anywhere in the string and is
1042 ignored.
1043 Return None if the given string is not a valid representation of an
1045 integer, or if the integer represented exceeds the range of integers
1046 representable in type int .
1047 Since 4.05
1050 val int_of_string : string -> int
1054 Same as int_of_string_opt , but raise Failure "int_of_string" instead
1056 of returning None .
1057 val string_of_float : float -> string
1061 Return the string representation of a floating-point number.
1063 val float_of_string_opt : string -> float option
1067 Convert the given string to a float. The string is read in decimal (by
1069 default) or in hexadecimal (marked by 0x or 0X ).
1070 The format of decimal floating-point numbers is [-] dd.ddd (e|E) [+|-]
1072 dd , where d stands for a decimal digit.
1073 The format of hexadecimal floating-point numbers is [-] 0(x|X) hh.hhh
1075 (p|P) [+|-] dd , where h stands for an hexadecimal digit and d for a
1076 decimal digit.
1077 In both cases, at least one of the integer and fractional parts must be
1079 given; the exponent part is optional.
1080 The _ (underscore) character can appear anywhere in the string and is
1082 ignored.
1083 Depending on the execution platforms, other representations of float‐
1085 ing-point numbers can be accepted, but should not be relied upon.
1086 Return None if the given string is not a valid representation of a
1088 float.
1089 Since 4.05
1092 val float_of_string : string -> float
1096 Same as float_of_string_opt , but raise Failure "float_of_string"
1098 instead of returning None .
1099 Pair operations
1104 val fst : 'a * 'b -> 'a
1105 Return the first component of a pair.
1107 val snd : 'a * 'b -> 'b
1111 Return the second component of a pair.
1113 List operations
1118 More list operations are provided in module List .
1119 val (@) : 'a list -> 'a list -> 'a list
1121 List concatenation. Not tail-recursive (length of the first argument).
1123 Right-associative operator, see Ocaml_operators for more information.
1124 Input/output
1129 Note: all input/output functions can raise Sys_error when the system
1130 calls they invoke fail.
1131 type in_channel
1133 The type of input channel.
1136 type out_channel
1139 The type of output channel.
1142 val stdin : in_channel
1146 The standard input for the process.
1148 val stdout : out_channel
1152 The standard output for the process.
1154 val stderr : out_channel
1158 The standard error output for the process.
1160 Output functions on standard output
1165 val print_char : char -> unit
1166 Print a character on standard output.
1168 val print_string : string -> unit
1172 Print a string on standard output.
1174 val print_bytes : bytes -> unit
1178 Print a byte sequence on standard output.
1180 Since 4.02.0
1183 val print_int : int -> unit
1187 Print an integer, in decimal, on standard output.
1189 val print_float : float -> unit
1193 Print a floating-point number, in decimal, on standard output.
1195 val print_endline : string -> unit
1199 Print a string, followed by a newline character, on standard output and
1201 flush standard output.
1202 val print_newline : unit -> unit
1206 Print a newline character on standard output, and flush standard out‐
1208 put. This can be used to simulate line buffering of standard output.
1209 Output functions on standard error
1214 val prerr_char : char -> unit
1215 Print a character on standard error.
1217 val prerr_string : string -> unit
1221 Print a string on standard error.
1223 val prerr_bytes : bytes -> unit
1227 Print a byte sequence on standard error.
1229 Since 4.02.0
1232 val prerr_int : int -> unit
1236 Print an integer, in decimal, on standard error.
1238 val prerr_float : float -> unit
1242 Print a floating-point number, in decimal, on standard error.
1244 val prerr_endline : string -> unit
1248 Print a string, followed by a newline character on standard error and
1250 flush standard error.
1251 val prerr_newline : unit -> unit
1255 Print a newline character on standard error, and flush standard error.
1257 Input functions on standard input
1262 val read_line : unit -> string
1263 Flush standard output, then read characters from standard input until a
1265 newline character is encountered. Return the string of all characters
1266 read, without the newline character at the end.
1267 val read_int_opt : unit -> int option
1271 Flush standard output, then read one line from standard input and con‐
1273 vert it to an integer.
1274 Return None if the line read is not a valid representation of an inte‐
1276 ger.
1277 Since 4.05
1280 val read_int : unit -> int
1284 Same as read_int_opt , but raise Failure "int_of_string" instead of
1286 returning None .
1287 val read_float_opt : unit -> float option
1291 Flush standard output, then read one line from standard input and con‐
1293 vert it to a floating-point number.
1294 Return None if the line read is not a valid representation of a float‐
1296 ing-point number.
1297 Since 4.05.0
1300 val read_float : unit -> float
1304 Same as read_float_opt , but raise Failure "float_of_string" instead of
1306 returning None .
1307 General output functions
1312 type open_flag =
1313 | Open_rdonly (* open for reading.
1314 *)
1315 | Open_wronly (* open for writing.
1316 *)
1317 | Open_append (* open for appending: always write at end of file.
1318 *)
1319 | Open_creat (* create the file if it does not exist.
1320 *)
1321 | Open_trunc (* empty the file if it already exists.
1322 *)
1323 | Open_excl (* fail if Open_creat and the file already exists.
1324 *)
1325 | Open_binary (* open in binary mode (no conversion).
1326 *)
1327 | Open_text (* open in text mode (may perform conversions).
1328 *)
1329 | Open_nonblock (* open in non-blocking mode.
1330 *)
1331 Opening modes for open_out_gen and open_in_gen .
1334 val open_out : string -> out_channel
1338 Open the named file for writing, and return a new output channel on
1340 that file, positioned at the beginning of the file. The file is trun‐
1341 cated to zero length if it already exists. It is created if it does not
1342 already exists.
1343 val open_out_bin : string -> out_channel
1347 Same as open_out , but the file is opened in binary mode, so that no
1349 translation takes place during writes. On operating systems that do not
1350 distinguish between text mode and binary mode, this function behaves
1351 like open_out .
1352 val open_out_gen : open_flag list -> int -> string -> out_channel
1356 open_out_gen mode perm filename opens the named file for writing, as
1359 described above. The extra argument mode specifies the opening mode.
1360 The extra argument perm specifies the file permissions, in case the
1361 file must be created. open_out and open_out_bin are special cases of
1362 this function.
1363 val flush : out_channel -> unit
1367 Flush the buffer associated with the given output channel, performing
1369 all pending writes on that channel. Interactive programs must be care‐
1370 ful about flushing standard output and standard error at the right
1371 time.
1372 val flush_all : unit -> unit
1376 Flush all open output channels; ignore errors.
1378 val output_char : out_channel -> char -> unit
1382 Write the character on the given output channel.
1384 val output_string : out_channel -> string -> unit
1388 Write the string on the given output channel.
1390 val output_bytes : out_channel -> bytes -> unit
1394 Write the byte sequence on the given output channel.
1396 Since 4.02.0
1399 val output : out_channel -> bytes -> int -> int -> unit
1403 output oc buf pos len writes len characters from byte sequence buf ,
1406 starting at offset pos , to the given output channel oc . Raise
1407 Invalid_argument "output" if pos and len do not designate a valid range
1408 of buf .
1409 val output_substring : out_channel -> string -> int -> int -> unit
1413 Same as output but take a string as argument instead of a byte
1415 sequence.
1416 Since 4.02.0
1419 val output_byte : out_channel -> int -> unit
1423 Write one 8-bit integer (as the single character with that code) on the
1425 given output channel. The given integer is taken modulo 256.
1426 val output_binary_int : out_channel -> int -> unit
1430 Write one integer in binary format (4 bytes, big-endian) on the given
1432 output channel. The given integer is taken modulo 2^32. The only
1433 reliable way to read it back is through the input_binary_int function.
1434 The format is compatible across all machines for a given version of
1435 OCaml.
1436 val output_value : out_channel -> 'a -> unit
1440 Write the representation of a structured value of any type to a chan‐
1442 nel. Circularities and sharing inside the value are detected and pre‐
1443 served. The object can be read back, by the function input_value . See
1444 the description of module Marshal for more information. output_value
1445 is equivalent to Marshal.to_channel with an empty list of flags.
1446 val seek_out : out_channel -> int -> unit
1450 seek_out chan pos sets the current writing position to pos for channel
1453 chan . This works only for regular files. On files of other kinds (such
1454 as terminals, pipes and sockets), the behavior is unspecified.
1455 val pos_out : out_channel -> int
1459 Return the current writing position for the given channel. Does not
1461 work on channels opened with the Open_append flag (returns unspecified
1462 results).
1463 val out_channel_length : out_channel -> int
1467 Return the size (number of characters) of the regular file on which the
1469 given channel is opened. If the channel is opened on a file that is
1470 not a regular file, the result is meaningless.
1471 val close_out : out_channel -> unit
1475 Close the given channel, flushing all buffered write operations. Out‐
1477 put functions raise a Sys_error exception when they are applied to a
1478 closed output channel, except close_out and flush , which do nothing
1479 when applied to an already closed channel. Note that close_out may
1480 raise Sys_error if the operating system signals an error when flushing
1481 or closing.
1482 val close_out_noerr : out_channel -> unit
1486 Same as close_out , but ignore all errors.
1488 val set_binary_mode_out : out_channel -> bool -> unit
1492 set_binary_mode_out oc true sets the channel oc to binary mode: no
1495 translations take place during output. set_binary_mode_out oc false
1496 sets the channel oc to text mode: depending on the operating system,
1497 some translations may take place during output. For instance, under
1498 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1499 tion has no effect under operating systems that do not distinguish
1500 between text mode and binary mode.
1501 General input functions
1506 val open_in : string -> in_channel
1507 Open the named file for reading, and return a new input channel on that
1509 file, positioned at the beginning of the file.
1510 val open_in_bin : string -> in_channel
1514 Same as open_in , but the file is opened in binary mode, so that no
1516 translation takes place during reads. On operating systems that do not
1517 distinguish between text mode and binary mode, this function behaves
1518 like open_in .
1519 val open_in_gen : open_flag list -> int -> string -> in_channel
1523 open_in_gen mode perm filename opens the named file for reading, as
1526 described above. The extra arguments mode and perm specify the opening
1527 mode and file permissions. open_in and open_in_bin are special cases
1528 of this function.
1529 val input_char : in_channel -> char
1533 Read one character from the given input channel. Raise End_of_file if
1535 there are no more characters to read.
1536 val input_line : in_channel -> string
1540 Read characters from the given input channel, until a newline character
1542 is encountered. Return the string of all characters read, without the
1543 newline character at the end. Raise End_of_file if the end of the file
1544 is reached at the beginning of line.
1545 val input : in_channel -> bytes -> int -> int -> int
1549 input ic buf pos len reads up to len characters from the given channel
1552 ic , storing them in byte sequence buf , starting at character number
1553 pos . It returns the actual number of characters read, between 0 and
1554 len (inclusive). A return value of 0 means that the end of file was
1555 reached. A return value between 0 and len exclusive means that not all
1556 requested len characters were read, either because no more characters
1557 were available at that time, or because the implementation found it
1558 convenient to do a partial read; input must be called again to read the
1559 remaining characters, if desired. (See also really_input for reading
1560 exactly len characters.) Exception Invalid_argument "input" is raised
1561 if pos and len do not designate a valid range of buf .
1562 val really_input : in_channel -> bytes -> int -> int -> unit
1566 really_input ic buf pos len reads len characters from channel ic ,
1569 storing them in byte sequence buf , starting at character number pos .
1570 Raise End_of_file if the end of file is reached before len characters
1571 have been read. Raise Invalid_argument "really_input" if pos and len
1572 do not designate a valid range of buf .
1573 val really_input_string : in_channel -> int -> string
1577 really_input_string ic len reads len characters from channel ic and
1580 returns them in a new string. Raise End_of_file if the end of file is
1581 reached before len characters have been read.
1582 Since 4.02.0
1585 val input_byte : in_channel -> int
1589 Same as input_char , but return the 8-bit integer representing the
1591 character. Raise End_of_file if an end of file was reached.
1592 val input_binary_int : in_channel -> int
1596 Read an integer encoded in binary format (4 bytes, big-endian) from the
1598 given input channel. See output_binary_int . Raise End_of_file if an
1599 end of file was reached while reading the integer.
1600 val input_value : in_channel -> 'a
1604 Read the representation of a structured value, as produced by out‐
1606 put_value , and return the corresponding value. This function is iden‐
1607 tical to Marshal.from_channel ; see the description of module Marshal
1608 for more information, in particular concerning the lack of type safety.
1609 val seek_in : in_channel -> int -> unit
1613 seek_in chan pos sets the current reading position to pos for channel
1616 chan . This works only for regular files. On files of other kinds, the
1617 behavior is unspecified.
1618 val pos_in : in_channel -> int
1622 Return the current reading position for the given channel.
1624 val in_channel_length : in_channel -> int
1628 Return the size (number of characters) of the regular file on which the
1630 given channel is opened. If the channel is opened on a file that is
1631 not a regular file, the result is meaningless. The returned size does
1632 not take into account the end-of-line translations that can be per‐
1633 formed when reading from a channel opened in text mode.
1634 val close_in : in_channel -> unit
1638 Close the given channel. Input functions raise a Sys_error exception
1640 when they are applied to a closed input channel, except close_in ,
1641 which does nothing when applied to an already closed channel.
1642 val close_in_noerr : in_channel -> unit
1646 Same as close_in , but ignore all errors.
1648 val set_binary_mode_in : in_channel -> bool -> unit
1652 set_binary_mode_in ic true sets the channel ic to binary mode: no
1655 translations take place during input. set_binary_mode_out ic false
1656 sets the channel ic to text mode: depending on the operating system,
1657 some translations may take place during input. For instance, under
1658 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1659 tion has no effect under operating systems that do not distinguish
1660 between text mode and binary mode.
1661 Operations on large files
1666 module LargeFile : sig end
1667 Operations on large files. This sub-module provides 64-bit variants of
1670 the channel functions that manipulate file positions and file sizes.
1671 By representing positions and sizes by 64-bit integers (type int64 )
1672 instead of regular integers (type int ), these alternate functions
1673 allow operating on files whose sizes are greater than max_int .
1674 References
1679 type 'a ref = {
1680 mutable contents : 'a ;
1682 }
1683 The type of references (mutable indirection cells) containing a value
1686 of type 'a .
1687 val ref : 'a -> 'a ref
1691 Return a fresh reference containing the given value.
1693 val (!) : 'a ref -> 'a
1697 !r returns the current contents of reference r . Equivalent to fun r
1700 -> r.contents . Unary operator, see Ocaml_operators for more informa‐
1701 tion.
1702 val (:=) : 'a ref -> 'a -> unit
1706 r := a stores the value of a in reference r . Equivalent to fun r v ->
1709 r.contents <- v . Right-associative operator, see Ocaml_operators for
1710 more information.
1711 val incr : int ref -> unit
1715 Increment the integer contained in the given reference. Equivalent to
1717 fun r -> r := succ !r .
1718 val decr : int ref -> unit
1722 Decrement the integer contained in the given reference. Equivalent to
1724 fun r -> r := pred !r .
1725 Result type
1730 type ('a, 'b) result =
1731 | Ok of 'a
1732 | Error of 'b
1733 Since 4.03.0
1736 Operations on format strings
1741 Format strings are character strings with special lexical conventions
1742 that defines the functionality of formatted input/output functions.
1743 Format strings are used to read data with formatted input functions
1744 from module Scanf and to print data with formatted output functions
1745 from modules Printf and Format .
1746 Format strings are made of three kinds of entities:
1748 -conversions specifications, introduced by the special character '%'
1750 followed by one or more characters specifying what kind of argument to
1751 read or print,
1752 -formatting indications, introduced by the special character '@' fol‐
1754 lowed by one or more characters specifying how to read or print the
1755 argument,
1756 -plain characters that are regular characters with usual lexical con‐
1758 ventions. Plain characters specify string literals to be read in the
1759 input or printed in the output.
1760 There is an additional lexical rule to escape the special characters
1762 '%' and '@' in format strings: if a special character follows a '%'
1763 character, it is treated as a plain character. In other words, "%%" is
1764 considered as a plain '%' and "%@" as a plain '@' .
1765 For more information about conversion specifications and formatting
1767 indications available, read the documentation of modules Scanf , Printf
1768 and Format .
1769 Format strings have a general and highly polymorphic type ('a, 'b, 'c,
1771 'd, 'e, 'f) format6 . The two simplified types, format and format4
1772 below are included for backward compatibility with earlier releases of
1773 OCaml.
1774 The meaning of format string type parameters is as follows:
1776 - 'a is the type of the parameters of the format for formatted output
1779 functions ( printf -style functions); 'a is the type of the values read
1780 by the format for formatted input functions ( scanf -style functions).
1781 - 'b is the type of input source for formatted input functions and the
1784 type of output target for formatted output functions. For printf
1785 -style functions from module Printf , 'b is typically out_channel ; for
1786 printf -style functions from module Format , 'b is typically For‐
1787 mat.formatter ; for scanf -style functions from module Scanf , 'b is
1788 typically Scanf.Scanning.in_channel .
1789 Type argument 'b is also the type of the first argument given to user's
1791 defined printing functions for %a and %t conversions, and user's
1792 defined reading functions for %r conversion.
1793 - 'c is the type of the result of the %a and %t printing functions, and
1796 also the type of the argument transmitted to the first argument of
1797 kprintf -style functions or to the kscanf -style functions.
1798 - 'd is the type of parameters for the scanf -style functions.
1801 - 'e is the type of the receiver function for the scanf -style func‐
1804 tions.
1805 - 'f is the final result type of a formatted input/output function
1808 invocation: for the printf -style functions, it is typically unit ; for
1809 the scanf -style functions, it is typically the result type of the
1810 receiver function.
1811 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1814 linternalFormatBasics.format6
1815 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1820 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1825 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1831 Converts a format string into a string.
1833 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1837 'd, 'e, 'f) format6
1838 format_of_string s returns a format string read from the string literal
1841 s . Note: format_of_string can not convert a string argument that is
1842 not a literal. If you need this functionality, use the more general
1843 Scanf.format_from_string function.
1844 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1848 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1849 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1852 string that behaves as the concatenation of format strings f1 and f2 :
1853 in case of formatted output, it accepts arguments from f1 , then argu‐
1854 ments from f2 ; in case of formatted input, it returns results from f1
1855 , then results from f2 . Right-associative operator, see Ocaml_opera‐
1856 tors for more information.
1857 Program termination
1862 val exit : int -> 'a
1863 Terminate the process, returning the given status code to the operating
1865 system: usually 0 to indicate no errors, and a small positive integer
1866 to indicate failure. All open output channels are flushed with
1867 flush_all . An implicit exit 0 is performed each time a program termi‐
1868 nates normally. An implicit exit 2 is performed if the program termi‐
1869 nates early because of an uncaught exception.
1870 val at_exit : (unit -> unit) -> unit
1874 Register the given function to be called at program termination time.
1876 The functions registered with at_exit will be called when the program
1877 does any of the following:
1878 -executes exit
1880 -terminates, either normally or because of an uncaught exception
1883 -executes the C function caml_shutdown . The functions are called in
1885 'last in, first out' order: the function most recently added with
1886 at_exit is called first.
1887 Standard library modules
1893 module Arg : (module Stdlib__arg)
1894 module Array : (module Stdlib__array)
1899 module ArrayLabels : (module Stdlib__arrayLabels)
1904 module Bigarray : (module Stdlib__bigarray)
1909 module Bool : (module Stdlib__bool)
1914 module Buffer : (module Stdlib__buffer)
1919 module Bytes : (module Stdlib__bytes)
1924 module BytesLabels : (module Stdlib__bytesLabels)
1929 module Callback : (module Stdlib__callback)
1934 module Char : (module Stdlib__char)
1939 module Complex : (module Stdlib__complex)
1944 module Digest : (module Stdlib__digest)
1949 module Ephemeron : (module Stdlib__ephemeron)
1954 module Filename : (module Stdlib__filename)
1959 module Float : (module Stdlib__float)
1964 module Format : (module Stdlib__format)
1969 module Fun : (module Stdlib__fun)
1974 module Gc : (module Stdlib__gc)
1979 module Genlex : (module Stdlib__genlex)
1984 module Hashtbl : (module Stdlib__hashtbl)
1989 module Int : (module Stdlib__int)
1994 module Int32 : (module Stdlib__int32)
1999 module Int64 : (module Stdlib__int64)
2004 module Lazy : (module Stdlib__lazy)
2009 module Lexing : (module Stdlib__lexing)
2014 module List : (module Stdlib__list)
2019 module ListLabels : (module Stdlib__listLabels)
2024 module Map : (module Stdlib__map)
2029 module Marshal : (module Stdlib__marshal)
2034 module MoreLabels : (module Stdlib__moreLabels)
2039 module Nativeint : (module Stdlib__nativeint)
2044 module Obj : (module Stdlib__obj)
2049 module Oo : (module Stdlib__oo)
2054 module Option : (module Stdlib__option)
2059 module Parsing : (module Stdlib__parsing)
2064 module Pervasives : (module Stdlib__pervasives)
2069 module Printexc : (module Stdlib__printexc)
2074 module Printf : (module Stdlib__printf)
2079 module Queue : (module Stdlib__queue)
2084 module Random : (module Stdlib__random)
2089 module Result : (module Stdlib__result)
2094 module Scanf : (module Stdlib__scanf)
2099 module Seq : (module Stdlib__seq)
2104 module Set : (module Stdlib__set)
2109 module Spacetime : (module Stdlib__spacetime)
2114 module Stack : (module Stdlib__stack)
2119 module StdLabels : (module Stdlib__stdLabels)
2124 module Stream : (module Stdlib__stream)
2129 module String : (module Stdlib__string)
2134 module StringLabels : (module Stdlib__stringLabels)
2139 module Sys : (module Stdlib__sys)
2144 module Uchar : (module Stdlib__uchar)
2149 module Unit : (module Stdlib__unit)
2154 module Weak : (module Stdlib__weak)
2159OCamldoc 2020-02-27 Stdlib(3)