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 __FUNCTION__ : string
397 __FUNCTION__ returns the name of the current function or method, in‐
400 cluding any enclosing modules or classes.
401 Since 4.12.0
404 val __LOC_OF__ : 'a -> string * 'a
408 __LOC_OF__ expr returns a pair (loc, expr) where loc is the location of
411 expr in the file currently being parsed by the compiler, with the stan‐
412 dard error format of OCaml: "File %S, line %d, characters %d-%d".
413 Since 4.02.0
416 val __LINE_OF__ : 'a -> int * 'a
420 __LINE_OF__ expr returns a pair (line, expr) , where line is the line
423 number at which the expression expr appears in the file currently being
424 parsed by the compiler.
425 Since 4.02.0
428 val __POS_OF__ : 'a -> (string * int * int * int) * 'a
432 __POS_OF__ expr returns a pair (loc,expr) , where loc is a tuple
435 (file,lnum,cnum,enum) corresponding to the location at which the ex‐
436 pression expr appears in the file currently being parsed by the com‐
437 piler. file is the current filename, lnum the line number, cnum the
438 character position in the line and enum the last character position in
439 the line.
440 Since 4.02.0
443 Composition operators
448 val (|>) : 'a -> ('a -> 'b) -> 'b
449 Reverse-application operator: x |> f |> g is exactly equivalent to g (f
451 (x)) . Left-associative operator, see Ocaml_operators for more infor‐
452 mation.
453 Since 4.01
456 val (@@) : ('a -> 'b) -> 'a -> 'b
460 Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
462 Right-associative operator, see Ocaml_operators for more information.
463 Since 4.01
466 Integer arithmetic
471 Integers are Sys.int_size bits wide. All operations are taken modulo
472 2^ Sys.int_size . They do not fail on overflow.
473 val (~-) : int -> int
475 Unary negation. You can also write - e instead of ~- e . Unary opera‐
477 tor, see Ocaml_operators for more information.
478 val (~+) : int -> int
482 Unary addition. You can also write + e instead of ~+ e . Unary opera‐
484 tor, see Ocaml_operators for more information.
485 Since 3.12.0
488 val succ : int -> int
492 succ x is x + 1 .
495 val pred : int -> int
499 pred x is x - 1 .
502 val (+) : int -> int -> int
506 Integer addition. Left-associative operator, see Ocaml_operators for
508 more information.
509 val (-) : int -> int -> int
513 Integer subtraction. Left-associative operator, , see Ocaml_operators
515 for more information.
516 val ( * ) : int -> int -> int
520 Integer multiplication. Left-associative operator, see Ocaml_operators
522 for more information.
523 val (/) : int -> int -> int
527 Integer division. Integer division rounds the real quotient of its ar‐
529 guments towards zero. More precisely, if x >= 0 and y > 0 , x / y is
530 the greatest integer less than or equal to the real quotient of x by y
531 . Moreover, (- x) / y = x / (- y) = - (x / y) . Left-associative op‐
532 erator, see Ocaml_operators for more information.
533 Raises Division_by_zero if the second argument is 0.
536 val (mod) : int -> int -> int
540 Integer remainder. If y is not zero, the result of x mod y satisfies
542 the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
543 abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
544 mod y is negative only if x < 0 . Left-associative operator, see
545 Ocaml_operators for more information.
546 Raises Division_by_zero if y is zero.
549 val abs : int -> int
553 Return the absolute value of the argument. Note that this may be nega‐
555 tive if the argument is min_int .
556 val max_int : int
560 The greatest representable integer.
562 val min_int : int
566 The smallest representable integer.
568 Bitwise operations
573 val (land) : int -> int -> int
574 Bitwise logical and. Left-associative operator, see Ocaml_operators
576 for more information.
577 val (lor) : int -> int -> int
581 Bitwise logical or. Left-associative operator, see Ocaml_operators for
583 more information.
584 val (lxor) : int -> int -> int
588 Bitwise logical exclusive or. Left-associative operator, see Ocaml_op‐
590 erators for more information.
591 val lnot : int -> int
595 Bitwise logical negation.
597 val (lsl) : int -> int -> int
601 n lsl m shifts n to the left by m bits. The result is unspecified if m
604 < 0 or m > Sys.int_size . Right-associative operator, see Ocaml_opera‐
605 tors for more information.
606 val (lsr) : int -> int -> int
610 n lsr m shifts n to the right by m bits. This is a logical shift: ze‐
613 roes are inserted regardless of the sign of n . The result is unspeci‐
614 fied if m < 0 or m > Sys.int_size . Right-associative operator, see
615 Ocaml_operators for more information.
616 val (asr) : int -> int -> int
620 n asr m shifts n to the right by m bits. This is an arithmetic shift:
623 the sign bit of n is replicated. The result is unspecified if m < 0 or
624 m > Sys.int_size . Right-associative operator, see Ocaml_operators for
625 more information.
626 Floating-point arithmetic
631 OCaml's floating-point numbers follow the IEEE 754 standard, using dou‐
632 ble precision (64 bits) numbers. Floating-point operations never raise
633 an exception on overflow, underflow, division by zero, etc. Instead,
634 special IEEE numbers are returned as appropriate, such as infinity for
635 1.0 /. 0.0 , neg_infinity for -1.0 /. 0.0 , and nan ('not a number')
636 for 0.0 /. 0.0 . These special numbers then propagate through float‐
637 ing-point computations as expected: for instance, 1.0 /. infinity is
638 0.0 , basic arithmetic operations ( +. , -. , *. , /. ) with nan as
639 an argument return nan , ...
640 val (~-.) : float -> float
642 Unary negation. You can also write -. e instead of ~-. e . Unary oper‐
644 ator, see Ocaml_operators for more information.
645 val (~+.) : float -> float
649 Unary addition. You can also write +. e instead of ~+. e . Unary oper‐
651 ator, see Ocaml_operators for more information.
652 Since 3.12.0
655 val (+.) : float -> float -> float
659 Floating-point addition. Left-associative operator, see Ocaml_opera‐
661 tors for more information.
662 val (-.) : float -> float -> float
666 Floating-point subtraction. Left-associative operator, see Ocaml_oper‐
668 ators for more information.
669 val ( *. ) : float -> float -> float
673 Floating-point multiplication. Left-associative operator, see
675 Ocaml_operators for more information.
676 val (/.) : float -> float -> float
680 Floating-point division. Left-associative operator, see Ocaml_opera‐
682 tors for more information.
683 val ( ** ) : float -> float -> float
687 Exponentiation. Right-associative operator, see Ocaml_operators for
689 more information.
690 val sqrt : float -> float
694 Square root.
696 val exp : float -> float
700 Exponential.
702 val log : float -> float
706 Natural logarithm.
708 val log10 : float -> float
712 Base 10 logarithm.
714 val expm1 : float -> float
718 expm1 x computes exp x -. 1.0 , giving numerically-accurate results
721 even if x is close to 0.0 .
722 Since 3.12.0
725 val log1p : float -> float
729 log1p x computes log(1.0 +. x) (natural logarithm), giving numeri‐
732 cally-accurate results even if x is close to 0.0 .
733 Since 3.12.0
736 val cos : float -> float
740 Cosine. Argument is in radians.
742 val sin : float -> float
746 Sine. Argument is in radians.
748 val tan : float -> float
752 Tangent. Argument is in radians.
754 val acos : float -> float
758 Arc cosine. The argument must fall within the range [-1.0, 1.0] . Re‐
760 sult is in radians and is between 0.0 and pi .
761 val asin : float -> float
765 Arc sine. The argument must fall within the range [-1.0, 1.0] . Re‐
767 sult is in radians and is between -pi/2 and pi/2 .
768 val atan : float -> float
772 Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
774 val atan2 : float -> float -> float
778 atan2 y x returns the arc tangent of y /. x . The signs of x and y are
781 used to determine the quadrant of the result. Result is in radians and
782 is between -pi and pi .
783 val hypot : float -> float -> float
787 hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
790 hypotenuse of a right-angled triangle with sides of length x and y ,
791 or, equivalently, the distance of the point (x,y) to origin. If one of
792 x or y is infinite, returns infinity even if the other is nan .
793 Since 4.00.0
796 val cosh : float -> float
800 Hyperbolic cosine. Argument is in radians.
802 val sinh : float -> float
806 Hyperbolic sine. Argument is in radians.
808 val tanh : float -> float
812 Hyperbolic tangent. Argument is in radians.
814 val acosh : float -> float
818 Hyperbolic arc cosine. The argument must fall within the range [1.0,
820 inf] . Result is in radians and is between 0.0 and inf .
821 Since 4.13.0
824 val asinh : float -> float
828 Hyperbolic arc sine. The argument and result range over the entire
830 real line. Result is in radians.
831 Since 4.13.0
834 val atanh : float -> float
838 Hyperbolic arc tangent. The argument must fall within the range [-1.0,
840 1.0] . Result is in radians and ranges over the entire real line.
841 Since 4.13.0
844 val ceil : float -> float
848 Round above to an integer value. ceil f returns the least integer
850 value greater than or equal to f . The result is returned as a float.
851 val floor : float -> float
855 Round below to an integer value. floor f returns the greatest integer
857 value less than or equal to f . The result is returned as a float.
858 val abs_float : float -> float
862 abs_float f returns the absolute value of f .
865 val copysign : float -> float -> float
869 copysign x y returns a float whose absolute value is that of x and
872 whose sign is that of y . If x is nan , returns nan . If y is nan ,
873 returns either x or -. x , but it is not specified which.
874 Since 4.00.0
877 val mod_float : float -> float -> float
881 mod_float a b returns the remainder of a with respect to b . The re‐
884 turned value is a -. n *. b , where n is the quotient a /. b rounded
885 towards zero to an integer.
886 val frexp : float -> float * int
890 frexp f returns the pair of the significant and the exponent of f .
893 When f is zero, the significant x and the exponent n of f are equal to
894 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
895 <= x < 1.0 .
896 val ldexp : float -> int -> float
900 ldexp x n returns x *. 2 ** n .
903 val modf : float -> float * float
907 modf f returns the pair of the fractional and integral part of f .
910 val float : int -> float
914 Same as float_of_int .
916 val float_of_int : int -> float
920 Convert an integer to floating-point.
922 val truncate : float -> int
926 Same as int_of_float .
928 val int_of_float : float -> int
932 Truncate the given floating-point number to an integer. The result is
934 unspecified if the argument is nan or falls outside the range of repre‐
935 sentable integers.
936 val infinity : float
940 Positive infinity.
942 val neg_infinity : float
946 Negative infinity.
948 val nan : float
952 A special floating-point value denoting the result of an undefined op‐
954 eration such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
955 ing-point operation with nan as argument returns nan as result. As for
956 floating-point comparisons, = , < , <= , > and >= return false and <>
957 returns true if one or both of their arguments is nan .
958 val max_float : float
962 The largest positive finite value of type float .
964 val min_float : float
968 The smallest positive, non-zero, non-denormalized value of type float .
970 val epsilon_float : float
974 The difference between 1.0 and the smallest exactly representable
976 floating-point number greater than 1.0 .
977 type fpclass =
980 | FP_normal (* Normal number, none of the below
981 *)
982 | FP_subnormal (* Number very close to 0.0, has reduced precision
983 *)
984 | FP_zero (* Number is 0.0 or -0.0
985 *)
986 | FP_infinite (* Number is positive or negative infinity
987 *)
988 | FP_nan (* Not a number: result of an undefined operation
989 *)
990 The five classes of floating-point numbers, as determined by the clas‐
993 sify_float function.
994 val classify_float : float -> fpclass
998 Return the class of the given floating-point number: normal, subnormal,
1000 zero, infinite, or not a number.
1001 String operations
1006 More string operations are provided in module String .
1007 val (^) : string -> string -> string
1009 String concatenation. Right-associative operator, see Ocaml_operators
1011 for more information.
1012 Raises Invalid_argument if the result is longer then than
1015 Sys.max_string_length bytes.
1016 Character operations
1021 More character operations are provided in module Char .
1022 val int_of_char : char -> int
1024 Return the ASCII code of the argument.
1026 val char_of_int : int -> char
1030 Return the character with the given ASCII code.
1032 Raises Invalid_argument if the argument is outside the range 0--255.
1035 Unit operations
1040 val ignore : 'a -> unit
1041 Discard the value of its argument and return () . For instance, ig‐
1043 nore(f x) discards the result of the side-effecting function f . It is
1044 equivalent to f x; () , except that the latter may generate a compiler
1045 warning; writing ignore(f x) instead avoids the warning.
1046 String conversion functions
1051 val string_of_bool : bool -> string
1052 Return the string representation of a boolean. As the returned values
1054 may be shared, the user should not modify them directly.
1055 val bool_of_string_opt : string -> bool option
1059 Convert the given string to a boolean.
1061 Return None if the string is not "true" or "false" .
1063 Since 4.05
1066 val bool_of_string : string -> bool
1070 Same as bool_of_string_opt , but raise Invalid_argument
1072 "bool_of_string" instead of returning None .
1073 val string_of_int : int -> string
1077 Return the string representation of an integer, in decimal.
1079 val int_of_string_opt : string -> int option
1083 Convert the given string to an integer. The string is read in decimal
1085 (by default, or if the string begins with 0u ), in hexadecimal (if it
1086 begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
1087 binary (if it begins with 0b or 0B ).
1088 The 0u prefix reads the input as an unsigned integer in the range [0,
1090 2*max_int+1] . If the input exceeds max_int it is converted to the
1091 signed integer min_int + input - max_int - 1 .
1092 The _ (underscore) character can appear anywhere in the string and is
1094 ignored.
1095 Return None if the given string is not a valid representation of an in‐
1097 teger, or if the integer represented exceeds the range of integers rep‐
1098 resentable in type int .
1099 Since 4.05
1102 val int_of_string : string -> int
1106 Same as int_of_string_opt , but raise Failure "int_of_string" instead
1108 of returning None .
1109 val string_of_float : float -> string
1113 Return the string representation of a floating-point number.
1115 val float_of_string_opt : string -> float option
1119 Convert the given string to a float. The string is read in decimal (by
1121 default) or in hexadecimal (marked by 0x or 0X ).
1122 The format of decimal floating-point numbers is [-] dd.ddd (e|E) [+|-]
1124 dd , where d stands for a decimal digit.
1125 The format of hexadecimal floating-point numbers is [-] 0(x|X) hh.hhh
1127 (p|P) [+|-] dd , where h stands for an hexadecimal digit and d for a
1128 decimal digit.
1129 In both cases, at least one of the integer and fractional parts must be
1131 given; the exponent part is optional.
1132 The _ (underscore) character can appear anywhere in the string and is
1134 ignored.
1135 Depending on the execution platforms, other representations of float‐
1137 ing-point numbers can be accepted, but should not be relied upon.
1138 Return None if the given string is not a valid representation of a
1140 float.
1141 Since 4.05
1144 val float_of_string : string -> float
1148 Same as float_of_string_opt , but raise Failure "float_of_string" in‐
1150 stead of returning None .
1151 Pair operations
1156 val fst : 'a * 'b -> 'a
1157 Return the first component of a pair.
1159 val snd : 'a * 'b -> 'b
1163 Return the second component of a pair.
1165 List operations
1170 More list operations are provided in module List .
1171 val (@) : 'a list -> 'a list -> 'a list
1173 List concatenation. Not tail-recursive (length of the first argument).
1175 Right-associative operator, see Ocaml_operators for more information.
1176 Input/output
1181 Note: all input/output functions can raise Sys_error when the system
1182 calls they invoke fail.
1183 type in_channel
1185 The type of input channel.
1188 type out_channel
1191 The type of output channel.
1194 val stdin : in_channel
1198 The standard input for the process.
1200 val stdout : out_channel
1204 The standard output for the process.
1206 val stderr : out_channel
1210 The standard error output for the process.
1212 Output functions on standard output
1217 val print_char : char -> unit
1218 Print a character on standard output.
1220 val print_string : string -> unit
1224 Print a string on standard output.
1226 val print_bytes : bytes -> unit
1230 Print a byte sequence on standard output.
1232 Since 4.02.0
1235 val print_int : int -> unit
1239 Print an integer, in decimal, on standard output.
1241 val print_float : float -> unit
1245 Print a floating-point number, in decimal, on standard output.
1247 val print_endline : string -> unit
1251 Print a string, followed by a newline character, on standard output and
1253 flush standard output.
1254 val print_newline : unit -> unit
1258 Print a newline character on standard output, and flush standard out‐
1260 put. This can be used to simulate line buffering of standard output.
1261 Output functions on standard error
1266 val prerr_char : char -> unit
1267 Print a character on standard error.
1269 val prerr_string : string -> unit
1273 Print a string on standard error.
1275 val prerr_bytes : bytes -> unit
1279 Print a byte sequence on standard error.
1281 Since 4.02.0
1284 val prerr_int : int -> unit
1288 Print an integer, in decimal, on standard error.
1290 val prerr_float : float -> unit
1294 Print a floating-point number, in decimal, on standard error.
1296 val prerr_endline : string -> unit
1300 Print a string, followed by a newline character on standard error and
1302 flush standard error.
1303 val prerr_newline : unit -> unit
1307 Print a newline character on standard error, and flush standard error.
1309 Input functions on standard input
1314 val read_line : unit -> string
1315 Flush standard output, then read characters from standard input until a
1317 newline character is encountered. Return the string of all characters
1318 read, without the newline character at the end.
1319 val read_int_opt : unit -> int option
1323 Flush standard output, then read one line from standard input and con‐
1325 vert it to an integer.
1326 Return None if the line read is not a valid representation of an inte‐
1328 ger.
1329 Since 4.05
1332 val read_int : unit -> int
1336 Same as read_int_opt , but raise Failure "int_of_string" instead of re‐
1338 turning None .
1339 val read_float_opt : unit -> float option
1343 Flush standard output, then read one line from standard input and con‐
1345 vert it to a floating-point number.
1346 Return None if the line read is not a valid representation of a float‐
1348 ing-point number.
1349 Since 4.05.0
1352 val read_float : unit -> float
1356 Same as read_float_opt , but raise Failure "float_of_string" instead of
1358 returning None .
1359 General output functions
1364 type open_flag =
1365 | Open_rdonly (* open for reading.
1366 *)
1367 | Open_wronly (* open for writing.
1368 *)
1369 | Open_append (* open for appending: always write at end of file.
1370 *)
1371 | Open_creat (* create the file if it does not exist.
1372 *)
1373 | Open_trunc (* empty the file if it already exists.
1374 *)
1375 | Open_excl (* fail if Open_creat and the file already exists.
1376 *)
1377 | Open_binary (* open in binary mode (no conversion).
1378 *)
1379 | Open_text (* open in text mode (may perform conversions).
1380 *)
1381 | Open_nonblock (* open in non-blocking mode.
1382 *)
1383 Opening modes for open_out_gen and open_in_gen .
1386 val open_out : string -> out_channel
1390 Open the named file for writing, and return a new output channel on
1392 that file, positioned at the beginning of the file. The file is trun‐
1393 cated to zero length if it already exists. It is created if it does not
1394 already exists.
1395 val open_out_bin : string -> out_channel
1399 Same as open_out , but the file is opened in binary mode, so that no
1401 translation takes place during writes. On operating systems that do not
1402 distinguish between text mode and binary mode, this function behaves
1403 like open_out .
1404 val open_out_gen : open_flag list -> int -> string -> out_channel
1408 open_out_gen mode perm filename opens the named file for writing, as
1411 described above. The extra argument mode specifies the opening mode.
1412 The extra argument perm specifies the file permissions, in case the
1413 file must be created. open_out and open_out_bin are special cases of
1414 this function.
1415 val flush : out_channel -> unit
1419 Flush the buffer associated with the given output channel, performing
1421 all pending writes on that channel. Interactive programs must be care‐
1422 ful about flushing standard output and standard error at the right
1423 time.
1424 val flush_all : unit -> unit
1428 Flush all open output channels; ignore errors.
1430 val output_char : out_channel -> char -> unit
1434 Write the character on the given output channel.
1436 val output_string : out_channel -> string -> unit
1440 Write the string on the given output channel.
1442 val output_bytes : out_channel -> bytes -> unit
1446 Write the byte sequence on the given output channel.
1448 Since 4.02.0
1451 val output : out_channel -> bytes -> int -> int -> unit
1455 output oc buf pos len writes len characters from byte sequence buf ,
1458 starting at offset pos , to the given output channel oc .
1459 Raises Invalid_argument if pos and len do not designate a valid range
1462 of buf .
1463 val output_substring : out_channel -> string -> int -> int -> unit
1467 Same as output but take a string as argument instead of a byte se‐
1469 quence.
1470 Since 4.02.0
1473 val output_byte : out_channel -> int -> unit
1477 Write one 8-bit integer (as the single character with that code) on the
1479 given output channel. The given integer is taken modulo 256.
1480 val output_binary_int : out_channel -> int -> unit
1484 Write one integer in binary format (4 bytes, big-endian) on the given
1486 output channel. The given integer is taken modulo 2^32. The only re‐
1487 liable way to read it back is through the input_binary_int function.
1488 The format is compatible across all machines for a given version of
1489 OCaml.
1490 val output_value : out_channel -> 'a -> unit
1494 Write the representation of a structured value of any type to a chan‐
1496 nel. Circularities and sharing inside the value are detected and pre‐
1497 served. The object can be read back, by the function input_value . See
1498 the description of module Marshal for more information. output_value
1499 is equivalent to Marshal.to_channel with an empty list of flags.
1500 val seek_out : out_channel -> int -> unit
1504 seek_out chan pos sets the current writing position to pos for channel
1507 chan . This works only for regular files. On files of other kinds (such
1508 as terminals, pipes and sockets), the behavior is unspecified.
1509 val pos_out : out_channel -> int
1513 Return the current writing position for the given channel. Does not
1515 work on channels opened with the Open_append flag (returns unspecified
1516 results). For files opened in text mode under Windows, the returned
1517 position is approximate (owing to end-of-line conversion); in particu‐
1518 lar, saving the current position with pos_out , then going back to this
1519 position using seek_out will not work. For this programming idiom to
1520 work reliably and portably, the file must be opened in binary mode.
1521 val out_channel_length : out_channel -> int
1525 Return the size (number of characters) of the regular file on which the
1527 given channel is opened. If the channel is opened on a file that is
1528 not a regular file, the result is meaningless.
1529 val close_out : out_channel -> unit
1533 Close the given channel, flushing all buffered write operations. Out‐
1535 put functions raise a Sys_error exception when they are applied to a
1536 closed output channel, except close_out and flush , which do nothing
1537 when applied to an already closed channel. Note that close_out may
1538 raise Sys_error if the operating system signals an error when flushing
1539 or closing.
1540 val close_out_noerr : out_channel -> unit
1544 Same as close_out , but ignore all errors.
1546 val set_binary_mode_out : out_channel -> bool -> unit
1550 set_binary_mode_out oc true sets the channel oc to binary mode: no
1553 translations take place during output. set_binary_mode_out oc false
1554 sets the channel oc to text mode: depending on the operating system,
1555 some translations may take place during output. For instance, under
1556 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1557 tion has no effect under operating systems that do not distinguish be‐
1558 tween text mode and binary mode.
1559 General input functions
1564 val open_in : string -> in_channel
1565 Open the named file for reading, and return a new input channel on that
1567 file, positioned at the beginning of the file.
1568 val open_in_bin : string -> in_channel
1572 Same as open_in , but the file is opened in binary mode, so that no
1574 translation takes place during reads. On operating systems that do not
1575 distinguish between text mode and binary mode, this function behaves
1576 like open_in .
1577 val open_in_gen : open_flag list -> int -> string -> in_channel
1581 open_in_gen mode perm filename opens the named file for reading, as de‐
1584 scribed above. The extra arguments mode and perm specify the opening
1585 mode and file permissions. open_in and open_in_bin are special cases
1586 of this function.
1587 val input_char : in_channel -> char
1591 Read one character from the given input channel.
1593 Raises End_of_file if there are no more characters to read.
1596 val input_line : in_channel -> string
1600 Read characters from the given input channel, until a newline character
1602 is encountered. Return the string of all characters read, without the
1603 newline character at the end.
1604 Raises End_of_file if the end of the file is reached at the beginning
1607 of line.
1608 val input : in_channel -> bytes -> int -> int -> int
1612 input ic buf pos len reads up to len characters from the given channel
1615 ic , storing them in byte sequence buf , starting at character number
1616 pos . It returns the actual number of characters read, between 0 and
1617 len (inclusive). A return value of 0 means that the end of file was
1618 reached. A return value between 0 and len exclusive means that not all
1619 requested len characters were read, either because no more characters
1620 were available at that time, or because the implementation found it
1621 convenient to do a partial read; input must be called again to read the
1622 remaining characters, if desired. (See also really_input for reading
1623 exactly len characters.) Exception Invalid_argument "input" is raised
1624 if pos and len do not designate a valid range of buf .
1625 val really_input : in_channel -> bytes -> int -> int -> unit
1629 really_input ic buf pos len reads len characters from channel ic ,
1632 storing them in byte sequence buf , starting at character number pos .
1633 Raises End_of_file if the end of file is reached before len characters
1636 have been read.
1637 Raises Invalid_argument if pos and len do not designate a valid range
1640 of buf .
1641 val really_input_string : in_channel -> int -> string
1645 really_input_string ic len reads len characters from channel ic and re‐
1648 turns them in a new string.
1649 Since 4.02.0
1652 Raises End_of_file if the end of file is reached before len characters
1655 have been read.
1656 val input_byte : in_channel -> int
1660 Same as input_char , but return the 8-bit integer representing the
1662 character.
1663 Raises End_of_file if an end of file was reached.
1666 val input_binary_int : in_channel -> int
1670 Read an integer encoded in binary format (4 bytes, big-endian) from the
1672 given input channel. See output_binary_int .
1673 Raises End_of_file if an end of file was reached while reading the in‐
1676 teger.
1677 val input_value : in_channel -> 'a
1681 Read the representation of a structured value, as produced by out‐
1683 put_value , and return the corresponding value. This function is iden‐
1684 tical to Marshal.from_channel ; see the description of module Marshal
1685 for more information, in particular concerning the lack of type safety.
1686 val seek_in : in_channel -> int -> unit
1690 seek_in chan pos sets the current reading position to pos for channel
1693 chan . This works only for regular files. On files of other kinds, the
1694 behavior is unspecified.
1695 val pos_in : in_channel -> int
1699 Return the current reading position for the given channel. For files
1701 opened in text mode under Windows, the returned position is approximate
1702 (owing to end-of-line conversion); in particular, saving the current
1703 position with pos_in , then going back to this position using seek_in
1704 will not work. For this programming idiom to work reliably and
1705 portably, the file must be opened in binary mode.
1706 val in_channel_length : in_channel -> int
1710 Return the size (number of characters) of the regular file on which the
1712 given channel is opened. If the channel is opened on a file that is
1713 not a regular file, the result is meaningless. The returned size does
1714 not take into account the end-of-line translations that can be per‐
1715 formed when reading from a channel opened in text mode.
1716 val close_in : in_channel -> unit
1720 Close the given channel. Input functions raise a Sys_error exception
1722 when they are applied to a closed input channel, except close_in ,
1723 which does nothing when applied to an already closed channel.
1724 val close_in_noerr : in_channel -> unit
1728 Same as close_in , but ignore all errors.
1730 val set_binary_mode_in : in_channel -> bool -> unit
1734 set_binary_mode_in ic true sets the channel ic to binary mode: no
1737 translations take place during input. set_binary_mode_out ic false
1738 sets the channel ic to text mode: depending on the operating system,
1739 some translations may take place during input. For instance, under
1740 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1741 tion has no effect under operating systems that do not distinguish be‐
1742 tween text mode and binary mode.
1743 Operations on large files
1748 module LargeFile : sig end
1749 Operations on large files. This sub-module provides 64-bit variants of
1752 the channel functions that manipulate file positions and file sizes.
1753 By representing positions and sizes by 64-bit integers (type int64 )
1754 instead of regular integers (type int ), these alternate functions al‐
1755 low operating on files whose sizes are greater than max_int .
1756 References
1761 type 'a ref = {
1762 mutable contents : 'a ;
1764 }
1765 The type of references (mutable indirection cells) containing a value
1768 of type 'a .
1769 val ref : 'a -> 'a ref
1773 Return a fresh reference containing the given value.
1775 val (!) : 'a ref -> 'a
1779 !r returns the current contents of reference r . Equivalent to fun r
1782 -> r.contents . Unary operator, see Ocaml_operators for more informa‐
1783 tion.
1784 val (:=) : 'a ref -> 'a -> unit
1788 r := a stores the value of a in reference r . Equivalent to fun r v ->
1791 r.contents <- v . Right-associative operator, see Ocaml_operators for
1792 more information.
1793 val incr : int ref -> unit
1797 Increment the integer contained in the given reference. Equivalent to
1799 fun r -> r := succ !r .
1800 val decr : int ref -> unit
1804 Decrement the integer contained in the given reference. Equivalent to
1806 fun r -> r := pred !r .
1807 Result type
1812 type ('a, 'b) result =
1813 | Ok of 'a
1814 | Error of 'b
1815 Since 4.03.0
1818 Operations on format strings
1823 Format strings are character strings with special lexical conventions
1824 that defines the functionality of formatted input/output functions.
1825 Format strings are used to read data with formatted input functions
1826 from module Scanf and to print data with formatted output functions
1827 from modules Printf and Format .
1828 Format strings are made of three kinds of entities:
1830 -conversions specifications, introduced by the special character '%'
1832 followed by one or more characters specifying what kind of argument to
1833 read or print,
1834 -formatting indications, introduced by the special character '@' fol‐
1836 lowed by one or more characters specifying how to read or print the ar‐
1837 gument,
1838 -plain characters that are regular characters with usual lexical con‐
1840 ventions. Plain characters specify string literals to be read in the
1841 input or printed in the output.
1842 There is an additional lexical rule to escape the special characters
1844 '%' and '@' in format strings: if a special character follows a '%'
1845 character, it is treated as a plain character. In other words, "%%" is
1846 considered as a plain '%' and "%@" as a plain '@' .
1847 For more information about conversion specifications and formatting in‐
1849 dications available, read the documentation of modules Scanf , Printf
1850 and Format .
1851 Format strings have a general and highly polymorphic type ('a, 'b, 'c,
1853 'd, 'e, 'f) format6 . The two simplified types, format and format4 be‐
1854 low are included for backward compatibility with earlier releases of
1855 OCaml.
1856 The meaning of format string type parameters is as follows:
1858 - 'a is the type of the parameters of the format for formatted output
1861 functions ( printf -style functions); 'a is the type of the values read
1862 by the format for formatted input functions ( scanf -style functions).
1863 - 'b is the type of input source for formatted input functions and the
1866 type of output target for formatted output functions. For printf
1867 -style functions from module Printf , 'b is typically out_channel ; for
1868 printf -style functions from module Format , 'b is typically For‐
1869 mat.formatter ; for scanf -style functions from module Scanf , 'b is
1870 typically Scanf.Scanning.in_channel .
1871 Type argument 'b is also the type of the first argument given to user's
1873 defined printing functions for %a and %t conversions, and user's de‐
1874 fined reading functions for %r conversion.
1875 - 'c is the type of the result of the %a and %t printing functions, and
1878 also the type of the argument transmitted to the first argument of
1879 kprintf -style functions or to the kscanf -style functions.
1880 - 'd is the type of parameters for the scanf -style functions.
1883 - 'e is the type of the receiver function for the scanf -style func‐
1886 tions.
1887 - 'f is the final result type of a formatted input/output function in‐
1890 vocation: for the printf -style functions, it is typically unit ; for
1891 the scanf -style functions, it is typically the result type of the re‐
1892 ceiver function.
1893 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1896 linternalFormatBasics.format6
1897 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1902 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1907 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1913 Converts a format string into a string.
1915 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1919 'd, 'e, 'f) format6
1920 format_of_string s returns a format string read from the string literal
1923 s . Note: format_of_string can not convert a string argument that is
1924 not a literal. If you need this functionality, use the more general
1925 Scanf.format_from_string function.
1926 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1930 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1931 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1934 string that behaves as the concatenation of format strings f1 and f2 :
1935 in case of formatted output, it accepts arguments from f1 , then argu‐
1936 ments from f2 ; in case of formatted input, it returns results from f1
1937 , then results from f2 . Right-associative operator, see Ocaml_opera‐
1938 tors for more information.
1939 Program termination
1944 val exit : int -> 'a
1945 Terminate the process, returning the given status code to the operating
1947 system: usually 0 to indicate no errors, and a small positive integer
1948 to indicate failure. All open output channels are flushed with
1949 flush_all . An implicit exit 0 is performed each time a program termi‐
1950 nates normally. An implicit exit 2 is performed if the program termi‐
1951 nates early because of an uncaught exception.
1952 val at_exit : (unit -> unit) -> unit
1956 Register the given function to be called at program termination time.
1958 The functions registered with at_exit will be called when the program
1959 does any of the following:
1960 -executes exit
1962 -terminates, either normally or because of an uncaught exception
1965 -executes the C function caml_shutdown . The functions are called in
1967 'last in, first out' order: the function most recently added with
1968 at_exit is called first.
1969 Standard library modules
1975 module Arg : (module Stdlib__Arg)
1976 module Array : (module Stdlib__Array)
1981 module ArrayLabels : (module Stdlib__ArrayLabels)
1986 module Atomic : (module Stdlib__Atomic)
1991 module Bigarray : (module Stdlib__Bigarray)
1996 module Bool : (module Stdlib__Bool)
2001 module Buffer : (module Stdlib__Buffer)
2006 module Bytes : (module Stdlib__Bytes)
2011 module BytesLabels : (module Stdlib__BytesLabels)
2016 module Callback : (module Stdlib__Callback)
2021 module Char : (module Stdlib__Char)
2026 module Complex : (module Stdlib__Complex)
2031 module Digest : (module Stdlib__Digest)
2036 module Either : (module Stdlib__Either)
2041 module Ephemeron : (module Stdlib__Ephemeron)
2046 module Filename : (module Stdlib__Filename)
2051 module Float : (module Stdlib__Float)
2056 module Format : (module Stdlib__Format)
2061 module Fun : (module Stdlib__Fun)
2066 module Gc : (module Stdlib__Gc)
2071 module Genlex : (module Stdlib__Genlex)
2076 module Hashtbl : (module Stdlib__Hashtbl)
2081 module Int : (module Stdlib__Int)
2086 module Int32 : (module Stdlib__Int32)
2091 module Int64 : (module Stdlib__Int64)
2096 module Lazy : (module Stdlib__Lazy)
2101 module Lexing : (module Stdlib__Lexing)
2106 module List : (module Stdlib__List)
2111 module ListLabels : (module Stdlib__ListLabels)
2116 module Map : (module Stdlib__Map)
2121 module Marshal : (module Stdlib__Marshal)
2126 module MoreLabels : (module Stdlib__MoreLabels)
2131 module Nativeint : (module Stdlib__Nativeint)
2136 module Obj : (module Stdlib__Obj)
2141 module Oo : (module Stdlib__Oo)
2146 module Option : (module Stdlib__Option)
2151 module Parsing : (module Stdlib__Parsing)
2156 module Pervasives : (module Stdlib__Pervasives)
2161 module Printexc : (module Stdlib__Printexc)
2166 module Printf : (module Stdlib__Printf)
2171 module Queue : (module Stdlib__Queue)
2176 module Random : (module Stdlib__Random)
2181 module Result : (module Stdlib__Result)
2186 module Scanf : (module Stdlib__Scanf)
2191 module Seq : (module Stdlib__Seq)
2196 module Set : (module Stdlib__Set)
2201 module Stack : (module Stdlib__Stack)
2206 module StdLabels : (module Stdlib__StdLabels)
2211 module Stream : (module Stdlib__Stream)
2216 module String : (module Stdlib__String)
2221 module StringLabels : (module Stdlib__StringLabels)
2226 module Sys : (module Stdlib__Sys)
2231 module Uchar : (module Stdlib__Uchar)
2236 module Unit : (module Stdlib__Unit)
2241 module Weak : (module Stdlib__Weak)
2246OCamldoc 2022-02-04 Stdlib(3)