1Pervasives(3) OCaml library Pervasives(3)
2
6 Pervasives - Pervasive operations.
7
9 Module Pervasives
10
12 Module Pervasives
13 : sig end
14 Pervasive operations.
17 This module provides the basic operations over the built-in types (num‐
19 bers, booleans, byte sequences, strings, exceptions, references, lists,
20 arrays, input-output channels, ...).
21 This module is included in the toplevel Stdlib module.
23 === Exceptions ===
31 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 === Comparisons ===
70 val (=) : 'a -> 'a -> bool
73 e1 = e2 tests for structural equality of e1 and e2 . Mutable struc‐
76 tures (e.g. references and arrays) are equal if and only if their cur‐
77 rent contents are structurally equal, even if the two mutable objects
78 are not the same physical object. Equality between functional values
79 raises Invalid_argument . Equality between cyclic data structures may
80 not terminate. Left-associative operator at precedence level 4/11.
81 val (<>) : 'a -> 'a -> bool
85 Negation of Pervasives.(=) . Left-associative operator at precedence
87 level 4/11.
88 val (<) : 'a -> 'a -> bool
92 See Pervasives.(>=) . Left-associative operator at precedence level
94 4/11.
95 val (>) : 'a -> 'a -> bool
99 See Pervasives.(>=) . Left-associative operator at precedence level
101 4/11.
102 val (<=) : 'a -> 'a -> bool
106 See Pervasives.(>=) . Left-associative operator at precedence level
108 4/11.
109 val (>=) : 'a -> 'a -> bool
113 Structural ordering functions. These functions coincide with the usual
115 orderings over integers, characters, strings, byte sequences and float‐
116 ing-point numbers, and extend them to a total ordering over all types.
117 The ordering is compatible with ( = ) . As in the case of ( = ) , muta‐
118 ble structures are compared by contents. Comparison between functional
119 values raises Invalid_argument . Comparison between cyclic structures
120 may not terminate. Left-associative operator at precedence level 4/11.
121 val compare : 'a -> 'a -> int
125 compare x y returns 0 if x is equal to y , a negative integer if x is
128 less than y , and a positive integer if x is greater than y . The
129 ordering implemented by compare is compatible with the comparison pred‐
130 icates = , < and > defined above, with one difference on the treatment
131 of the float value Pervasives.nan . Namely, the comparison predicates
132 treat nan as different from any other float value, including itself;
133 while compare treats nan as equal to itself and less than any other
134 float value. This treatment of nan ensures that compare defines a
135 total ordering relation.
136 compare applied to functional values may raise Invalid_argument . com‐
139 pare applied to cyclic structures may not terminate.
140 The compare function can be used as the comparison function required by
142 the Set.Make and Map.Make functors, as well as the List.sort and
143 Array.sort functions.
144 val min : 'a -> 'a -> 'a
148 Return the smaller of the two arguments. The result is unspecified if
150 one of the arguments contains the float value nan .
151 val max : 'a -> 'a -> 'a
155 Return the greater of the two arguments. The result is unspecified if
157 one of the arguments contains the float value nan .
158 val (==) : 'a -> 'a -> bool
162 e1 == e2 tests for physical equality of e1 and e2 . On mutable types
165 such as references, arrays, byte sequences, records with mutable fields
166 and objects with mutable instance variables, e1 == e2 is true if and
167 only if physical modification of e1 also affects e2 . On non-mutable
168 types, the behavior of ( == ) is implementation-dependent; however, it
169 is guaranteed that e1 == e2 implies compare e1 e2 = 0 . Left-associa‐
170 tive operator at precedence level 4/11.
171 val (!=) : 'a -> 'a -> bool
175 Negation of Pervasives.(==) . Left-associative operator at precedence
177 level 4/11.
178 === Boolean operations ===
183 val not : bool -> bool
186 The boolean negation.
188 val (&&) : bool -> bool -> bool
192 The boolean 'and'. Evaluation is sequential, left-to-right: in e1 && e2
194 , e1 is evaluated first, and if it returns false , e2 is not evaluated
195 at all. Right-associative operator at precedence level 3/11.
196 val (&) : bool -> bool -> bool
200 Deprecated.
202 Pervasives.(&&) should be used instead. Right-associative operator at
204 precedence level 3/11.
205 val (||) : bool -> bool -> bool
209 The boolean 'or'. Evaluation is sequential, left-to-right: in e1 || e2
211 , e1 is evaluated first, and if it returns true , e2 is not evaluated
212 at all. Right-associative operator at precedence level 2/11.
213 val (or) : bool -> bool -> bool
217 Deprecated.
219 Pervasives.(||) should be used instead. Right-associative operator at
221 precedence level 2/11.
222 === Debugging ===
227 val __LOC__ : string
230 __LOC__ returns the location at which this expression appears in the
233 file currently being parsed by the compiler, with the standard error
234 format of OCaml: "File %S, line %d, characters %d-%d".
235 Since 4.02.0
238 val __FILE__ : string
242 __FILE__ returns the name of the file currently being parsed by the
245 compiler.
246 Since 4.02.0
249 val __LINE__ : int
253 __LINE__ returns the line number at which this expression appears in
256 the file currently being parsed by the compiler.
257 Since 4.02.0
260 val __MODULE__ : string
264 __MODULE__ returns the module name of the file being parsed by the com‐
267 piler.
268 Since 4.02.0
271 val __POS__ : string * int * int * int
275 __POS__ returns a tuple (file,lnum,cnum,enum) , corresponding to the
278 location at which this expression appears in the file currently being
279 parsed by the compiler. file is the current filename, lnum the line
280 number, cnum the character position in the line and enum the last char‐
281 acter position in the line.
282 Since 4.02.0
285 val __LOC_OF__ : 'a -> string * 'a
289 __LOC_OF__ expr returns a pair (loc, expr) where loc is the location of
292 expr in the file currently being parsed by the compiler, with the stan‐
293 dard error format of OCaml: "File %S, line %d, characters %d-%d".
294 Since 4.02.0
297 val __LINE_OF__ : 'a -> int * 'a
301 __LINE_OF__ expr returns a pair (line, expr) , where line is the line
304 number at which the expression expr appears in the file currently being
305 parsed by the compiler.
306 Since 4.02.0
309 val __POS_OF__ : 'a -> (string * int * int * int) * 'a
313 __POS_OF__ expr returns a pair (loc,expr) , where loc is a tuple
316 (file,lnum,cnum,enum) corresponding to the location at which the
317 expression expr appears in the file currently being parsed by the com‐
318 piler. file is the current filename, lnum the line number, cnum the
319 character position in the line and enum the last character position in
320 the line.
321 Since 4.02.0
324 === Composition operators ===
329 val (|>) : 'a -> ('a -> 'b) -> 'b
332 Reverse-application operator: x |> f |> g is exactly equivalent to g (f
334 (x)) . Left-associative operator at precedence level 4/11.
335 Since 4.01
338 val (@@) : ('a -> 'b) -> 'a -> 'b
342 Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
344 Right-associative operator at precedence level 5/11.
345 Since 4.01
348 === Integer arithmetic ===
353 === Integers are Sys.int_size bits wide. All operations are taken mod‐
356 ulo 2^{Sys.int_size}. They do not fail on overflow. ===
357 val (~-) : int -> int
360 Unary negation. You can also write - e instead of ~- e . Unary opera‐
362 tor at precedence level 9/11 for - e and 11/11 for ~- e .
363 val (~+) : int -> int
367 Unary addition. You can also write + e instead of ~+ e . Unary opera‐
369 tor at precedence level 9/11 for + e and 11/11 for ~+ e .
370 Since 3.12.0
373 val succ : int -> int
377 succ x is x + 1 .
380 val pred : int -> int
384 pred x is x - 1 .
387 val (+) : int -> int -> int
391 Integer addition. Left-associative operator at precedence level 6/11.
393 val (-) : int -> int -> int
397 Integer subtraction. Left-associative operator at precedence level
399 6/11.
400 val ( * ) : int -> int -> int
404 Integer multiplication. Left-associative operator at precedence level
406 7/11.
407 val (/) : int -> int -> int
411 Integer division. Raise Division_by_zero if the second argument is 0.
413 Integer division rounds the real quotient of its arguments towards
414 zero. More precisely, if x >= 0 and y > 0 , x / y is the greatest
415 integer less than or equal to the real quotient of x by y . Moreover,
416 (- x) / y = x / (- y) = - (x / y) . Left-associative operator at
417 precedence level 7/11.
418 val (mod) : int -> int -> int
422 Integer remainder. If y is not zero, the result of x mod y satisfies
424 the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
425 abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
426 mod y is negative only if x < 0 . Raise Division_by_zero if y is zero.
427 Left-associative operator at precedence level 7/11.
428 val abs : int -> int
432 Return the absolute value of the argument. Note that this may be nega‐
434 tive if the argument is min_int .
435 val max_int : int
439 The greatest representable integer.
441 val min_int : int
445 The smallest representable integer.
447 === Bitwise operations ===
452 val (land) : int -> int -> int
455 Bitwise logical and. Left-associative operator at precedence level
457 7/11.
458 val (lor) : int -> int -> int
462 Bitwise logical or. Left-associative operator at precedence level
464 7/11.
465 val (lxor) : int -> int -> int
469 Bitwise logical exclusive or. Left-associative operator at precedence
471 level 7/11.
472 val lnot : int -> int
476 Bitwise logical negation.
478 val (lsl) : int -> int -> int
482 n lsl m shifts n to the left by m bits. The result is unspecified if m
485 < 0 or m > Sys.int_size . Right-associative operator at precedence
486 level 8/11.
487 val (lsr) : int -> int -> int
491 n lsr m shifts n to the right by m bits. This is a logical shift:
494 zeroes are inserted regardless of the sign of n . The result is
495 unspecified if m < 0 or m > Sys.int_size . Right-associative operator
496 at precedence level 8/11.
497 val (asr) : int -> int -> int
501 n asr m shifts n to the right by m bits. This is an arithmetic shift:
504 the sign bit of n is replicated. The result is unspecified if m < 0 or
505 m > Sys.int_size . Right-associative operator at precedence level
506 8/11.
507 === Floating-point arithmetic OCaml's floating-point numbers follow the
512 IEEE 754 standard, using double precision (64 bits) numbers. Float‐
513 ing-point operations never raise an exception on overflow, underflow,
514 division by zero, etc. Instead, special IEEE numbers are returned as
515 appropriate, such as infinity for 1.0 /. 0.0, neg_infinity for -1.0 /.
516 0.0, and nan ('not a number') for 0.0 /. 0.0. These special numbers
517 then propagate through floating-point computations as expected: for
518 instance, 1.0 /. infinity is 0.0, and any arithmetic operation with nan
519 as argument returns nan as result. ===
520 val (~-.) : float -> float
523 Unary negation. You can also write -. e instead of ~-. e . Unary oper‐
525 ator at precedence level 9/11 for -. e and 11/11 for ~-. e .
526 val (~+.) : float -> float
530 Unary addition. You can also write +. e instead of ~+. e . Unary oper‐
532 ator at precedence level 9/11 for +. e and 11/11 for ~+. e .
533 Since 3.12.0
536 val (+.) : float -> float -> float
540 Floating-point addition. Left-associative operator at precedence level
542 6/11.
543 val (-.) : float -> float -> float
547 Floating-point subtraction. Left-associative operator at precedence
549 level 6/11.
550 val ( *. ) : float -> float -> float
554 Floating-point multiplication. Left-associative operator at precedence
556 level 7/11.
557 val (/.) : float -> float -> float
561 Floating-point division. Left-associative operator at precedence level
563 7/11.
564 val ( ** ) : float -> float -> float
568 Exponentiation. Right-associative operator at precedence level 8/11.
570 val sqrt : float -> float
574 Square root.
576 val exp : float -> float
580 Exponential.
582 val log : float -> float
586 Natural logarithm.
588 val log10 : float -> float
592 Base 10 logarithm.
594 val expm1 : float -> float
598 expm1 x computes exp x -. 1.0 , giving numerically-accurate results
601 even if x is close to 0.0 .
602 Since 3.12.0
605 val log1p : float -> float
609 log1p x computes log(1.0 +. x) (natural logarithm), giving numeri‐
612 cally-accurate results even if x is close to 0.0 .
613 Since 3.12.0
616 val cos : float -> float
620 Cosine. Argument is in radians.
622 val sin : float -> float
626 Sine. Argument is in radians.
628 val tan : float -> float
632 Tangent. Argument is in radians.
634 val acos : float -> float
638 Arc cosine. The argument must fall within the range [-1.0, 1.0] .
640 Result is in radians and is between 0.0 and pi .
641 val asin : float -> float
645 Arc sine. The argument must fall within the range [-1.0, 1.0] .
647 Result is in radians and is between -pi/2 and pi/2 .
648 val atan : float -> float
652 Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
654 val atan2 : float -> float -> float
658 atan2 y x returns the arc tangent of y /. x . The signs of x and y are
661 used to determine the quadrant of the result. Result is in radians and
662 is between -pi and pi .
663 val hypot : float -> float -> float
667 hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
670 hypotenuse of a right-angled triangle with sides of length x and y ,
671 or, equivalently, the distance of the point (x,y) to origin. If one of
672 x or y is infinite, returns infinity even if the other is nan .
673 Since 4.00.0
676 val cosh : float -> float
680 Hyperbolic cosine. Argument is in radians.
682 val sinh : float -> float
686 Hyperbolic sine. Argument is in radians.
688 val tanh : float -> float
692 Hyperbolic tangent. Argument is in radians.
694 val ceil : float -> float
698 Round above to an integer value. ceil f returns the least integer
700 value greater than or equal to f . The result is returned as a float.
701 val floor : float -> float
705 Round below to an integer value. floor f returns the greatest integer
707 value less than or equal to f . The result is returned as a float.
708 val abs_float : float -> float
712 abs_float f returns the absolute value of f .
715 val copysign : float -> float -> float
719 copysign x y returns a float whose absolute value is that of x and
722 whose sign is that of y . If x is nan , returns nan . If y is nan ,
723 returns either x or -. x , but it is not specified which.
724 Since 4.00.0
727 val mod_float : float -> float -> float
731 mod_float a b returns the remainder of a with respect to b . The
734 returned value is a -. n *. b , where n is the quotient a /. b rounded
735 towards zero to an integer.
736 val frexp : float -> float * int
740 frexp f returns the pair of the significant and the exponent of f .
743 When f is zero, the significant x and the exponent n of f are equal to
744 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
745 <= x < 1.0 .
746 val ldexp : float -> int -> float
750 ldexp x n returns x *. 2 ** n .
753 val modf : float -> float * float
757 modf f returns the pair of the fractional and integral part of f .
760 val float : int -> float
764 Same as Pervasives.float_of_int .
766 val float_of_int : int -> float
770 Convert an integer to floating-point.
772 val truncate : float -> int
776 Same as Pervasives.int_of_float .
778 val int_of_float : float -> int
782 Truncate the given floating-point number to an integer. The result is
784 unspecified if the argument is nan or falls outside the range of repre‐
785 sentable integers.
786 val infinity : float
790 Positive infinity.
792 val neg_infinity : float
796 Negative infinity.
798 val nan : float
802 A special floating-point value denoting the result of an undefined
804 operation such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
805 ing-point operation with nan as argument returns nan as result. As for
806 floating-point comparisons, = , < , <= , > and >= return false and <>
807 returns true if one or both of their arguments is nan .
808 val max_float : float
812 The largest positive finite value of type float .
814 val min_float : float
818 The smallest positive, non-zero, non-denormalized value of type float .
820 val epsilon_float : float
824 The difference between 1.0 and the smallest exactly representable
826 floating-point number greater than 1.0 .
827 type fpclass =
830 | FP_normal (* Normal number, none of the below
831 *)
832 | FP_subnormal (* Number very close to 0.0, has reduced precision
833 *)
834 | FP_zero (* Number is 0.0 or -0.0
835 *)
836 | FP_infinite (* Number is positive or negative infinity
837 *)
838 | FP_nan (* Not a number: result of an undefined operation
839 *)
840 The five classes of floating-point numbers, as determined by the Perva‐
843 sives.classify_float function.
844 val classify_float : float -> fpclass
848 Return the class of the given floating-point number: normal, subnormal,
850 zero, infinite, or not a number.
851 === String operations More string operations are provided in module
856 String. ===
857 val (^) : string -> string -> string
860 String concatenation. Right-associative operator at precedence level
862 5/11.
863 === Character operations More character operations are provided in mod‐
868 ule Char. ===
869 val int_of_char : char -> int
872 Return the ASCII code of the argument.
874 val char_of_int : int -> char
878 Return the character with the given ASCII code. Raise Invalid_argument
880 char_of_int if the argument is outside the range 0--255.
881 === Unit operations ===
886 val ignore : 'a -> unit
889 Discard the value of its argument and return () . For instance,
891 ignore(f x) discards the result of the side-effecting function f . It
892 is equivalent to f x; () , except that the latter may generate a com‐
893 piler warning; writing ignore(f x) instead avoids the warning.
894 === String conversion functions ===
899 val string_of_bool : bool -> string
902 Return the string representation of a boolean. As the returned values
904 may be shared, the user should not modify them directly.
905 val bool_of_string : string -> bool
909 Convert the given string to a boolean. Raise Invalid_argument
911 bool_of_string if the string is not true or false .
912 val bool_of_string_opt : string -> bool option
916 Convert the given string to a boolean. Return None if the string is
918 not true or false .
919 Since 4.05
922 val string_of_int : int -> string
926 Return the string representation of an integer, in decimal.
928 val int_of_string : string -> int
932 Convert the given string to an integer. The string is read in decimal
934 (by default, or if the string begins with 0u ), in hexadecimal (if it
935 begins with 0x or 0X ), in octal (if it begins with 0o or 0O ), or in
936 binary (if it begins with 0b or 0B ).
937 The 0u prefix reads the input as an unsigned integer in the range [0,
939 2*max_int+1] . If the input exceeds Pervasives.max_int it is converted
940 to the signed integer min_int + input - max_int - 1 .
941 The _ (underscore) character can appear anywhere in the string and is
943 ignored. Raise Failure int_of_string if the given string is not a
944 valid representation of an integer, or if the integer represented
945 exceeds the range of integers representable in type int .
946 val int_of_string_opt : string -> int option
950 Same as int_of_string , but returns None instead of raising.
952 Since 4.05
955 val string_of_float : float -> string
959 Return the string representation of a floating-point number.
961 val float_of_string : string -> float
965 Convert the given string to a float. The string is read in decimal (by
967 default) or in hexadecimal (marked by 0x or 0X ). The format of deci‐
968 mal floating-point numbers is [-] dd.ddd (e|E) [+|-] dd , where d
969 stands for a decimal digit. The format of hexadecimal floating-point
970 numbers is [-] 0(x|X) hh.hhh (p|P) [+|-] dd , where h stands for an
971 hexadecimal digit and d for a decimal digit. In both cases, at least
972 one of the integer and fractional parts must be given; the exponent
973 part is optional. The _ (underscore) character can appear anywhere in
974 the string and is ignored. Depending on the execution platforms, other
975 representations of floating-point numbers can be accepted, but should
976 not be relied upon. Raise Failure float_of_string if the given string
977 is not a valid representation of a float.
978 val float_of_string_opt : string -> float option
982 Same as float_of_string , but returns None instead of raising.
984 Since 4.05
987 === Pair operations ===
992 val fst : 'a * 'b -> 'a
995 Return the first component of a pair.
997 val snd : 'a * 'b -> 'b
1001 Return the second component of a pair.
1003 === List operations More list operations are provided in module List.
1008 ===
1009 val (@) : 'a list -> 'a list -> 'a list
1012 List concatenation. Not tail-recursive (length of the first argument).
1014 Right-associative operator at precedence level 5/11.
1015 === Input/output Note: all input/output functions can raise Sys_error
1020 when the system calls they invoke fail. ===
1021 type in_channel
1024 The type of input channel.
1027 type out_channel
1030 The type of output channel.
1033 val stdin : in_channel
1037 The standard input for the process.
1039 val stdout : out_channel
1043 The standard output for the process.
1045 val stderr : out_channel
1049 The standard error output for the process.
1051 === Output functions on standard output ===
1056 val print_char : char -> unit
1059 Print a character on standard output.
1061 val print_string : string -> unit
1065 Print a string on standard output.
1067 val print_bytes : bytes -> unit
1071 Print a byte sequence on standard output.
1073 Since 4.02.0
1076 val print_int : int -> unit
1080 Print an integer, in decimal, on standard output.
1082 val print_float : float -> unit
1086 Print a floating-point number, in decimal, on standard output.
1088 val print_endline : string -> unit
1092 Print a string, followed by a newline character, on standard output and
1094 flush standard output.
1095 val print_newline : unit -> unit
1099 Print a newline character on standard output, and flush standard out‐
1101 put. This can be used to simulate line buffering of standard output.
1102 === Output functions on standard error ===
1107 val prerr_char : char -> unit
1110 Print a character on standard error.
1112 val prerr_string : string -> unit
1116 Print a string on standard error.
1118 val prerr_bytes : bytes -> unit
1122 Print a byte sequence on standard error.
1124 Since 4.02.0
1127 val prerr_int : int -> unit
1131 Print an integer, in decimal, on standard error.
1133 val prerr_float : float -> unit
1137 Print a floating-point number, in decimal, on standard error.
1139 val prerr_endline : string -> unit
1143 Print a string, followed by a newline character on standard error and
1145 flush standard error.
1146 val prerr_newline : unit -> unit
1150 Print a newline character on standard error, and flush standard error.
1152 === Input functions on standard input ===
1157 val read_line : unit -> string
1160 Flush standard output, then read characters from standard input until a
1162 newline character is encountered. Return the string of all characters
1163 read, without the newline character at the end.
1164 val read_int : unit -> int
1168 Flush standard output, then read one line from standard input and con‐
1170 vert it to an integer. Raise Failure int_of_string if the line read is
1171 not a valid representation of an integer.
1172 val read_int_opt : unit -> int option
1176 Same as read_int_opt , but returns None instead of raising.
1178 Since 4.05
1181 val read_float : unit -> float
1185 Flush standard output, then read one line from standard input and con‐
1187 vert it to a floating-point number. The result is unspecified if the
1188 line read is not a valid representation of a floating-point number.
1189 val read_float_opt : unit -> float option
1193 Flush standard output, then read one line from standard input and con‐
1195 vert it to a floating-point number. Returns None if the line read is
1196 not a valid representation of a floating-point number.
1197 Since 4.05.0
1200 === General output functions ===
1205 type open_flag =
1208 | Open_rdonly (* open for reading.
1209 *)
1210 | Open_wronly (* open for writing.
1211 *)
1212 | Open_append (* open for appending: always write at end of file.
1213 *)
1214 | Open_creat (* create the file if it does not exist.
1215 *)
1216 | Open_trunc (* empty the file if it already exists.
1217 *)
1218 | Open_excl (* fail if Open_creat and the file already exists.
1219 *)
1220 | Open_binary (* open in binary mode (no conversion).
1221 *)
1222 | Open_text (* open in text mode (may perform conversions).
1223 *)
1224 | Open_nonblock (* open in non-blocking mode.
1225 *)
1226 Opening modes for Pervasives.open_out_gen and Pervasives.open_in_gen .
1229 val open_out : string -> out_channel
1233 Open the named file for writing, and return a new output channel on
1235 that file, positioned at the beginning of the file. The file is trun‐
1236 cated to zero length if it already exists. It is created if it does not
1237 already exists.
1238 val open_out_bin : string -> out_channel
1242 Same as Pervasives.open_out , but the file is opened in binary mode, so
1244 that no translation takes place during writes. On operating systems
1245 that do not distinguish between text mode and binary mode, this func‐
1246 tion behaves like Pervasives.open_out .
1247 val open_out_gen : open_flag list -> int -> string -> out_channel
1251 open_out_gen mode perm filename opens the named file for writing, as
1254 described above. The extra argument mode specifies the opening mode.
1255 The extra argument perm specifies the file permissions, in case the
1256 file must be created. Pervasives.open_out and Pervasives.open_out_bin
1257 are special cases of this function.
1258 val flush : out_channel -> unit
1262 Flush the buffer associated with the given output channel, performing
1264 all pending writes on that channel. Interactive programs must be care‐
1265 ful about flushing standard output and standard error at the right
1266 time.
1267 val flush_all : unit -> unit
1271 Flush all open output channels; ignore errors.
1273 val output_char : out_channel -> char -> unit
1277 Write the character on the given output channel.
1279 val output_string : out_channel -> string -> unit
1283 Write the string on the given output channel.
1285 val output_bytes : out_channel -> bytes -> unit
1289 Write the byte sequence on the given output channel.
1291 Since 4.02.0
1294 val output : out_channel -> bytes -> int -> int -> unit
1298 output oc buf pos len writes len characters from byte sequence buf ,
1301 starting at offset pos , to the given output channel oc . Raise
1302 Invalid_argument output if pos and len do not designate a valid range
1303 of buf .
1304 val output_substring : out_channel -> string -> int -> int -> unit
1308 Same as output but take a string as argument instead of a byte
1310 sequence.
1311 Since 4.02.0
1314 val output_byte : out_channel -> int -> unit
1318 Write one 8-bit integer (as the single character with that code) on the
1320 given output channel. The given integer is taken modulo 256.
1321 val output_binary_int : out_channel -> int -> unit
1325 Write one integer in binary format (4 bytes, big-endian) on the given
1327 output channel. The given integer is taken modulo 2^32. The only
1328 reliable way to read it back is through the Pervasives.input_binary_int
1329 function. The format is compatible across all machines for a given ver‐
1330 sion of OCaml.
1331 val output_value : out_channel -> 'a -> unit
1335 Write the representation of a structured value of any type to a chan‐
1337 nel. Circularities and sharing inside the value are detected and pre‐
1338 served. The object can be read back, by the function Perva‐
1339 sives.input_value . See the description of module Marshal for more
1340 information. Pervasives.output_value is equivalent to Marshal.to_chan‐
1341 nel with an empty list of flags.
1342 val seek_out : out_channel -> int -> unit
1346 seek_out chan pos sets the current writing position to pos for channel
1349 chan . This works only for regular files. On files of other kinds (such
1350 as terminals, pipes and sockets), the behavior is unspecified.
1351 val pos_out : out_channel -> int
1355 Return the current writing position for the given channel. Does not
1357 work on channels opened with the Open_append flag (returns unspecified
1358 results).
1359 val out_channel_length : out_channel -> int
1363 Return the size (number of characters) of the regular file on which the
1365 given channel is opened. If the channel is opened on a file that is
1366 not a regular file, the result is meaningless.
1367 val close_out : out_channel -> unit
1371 Close the given channel, flushing all buffered write operations. Out‐
1373 put functions raise a Sys_error exception when they are applied to a
1374 closed output channel, except close_out and flush , which do nothing
1375 when applied to an already closed channel. Note that close_out may
1376 raise Sys_error if the operating system signals an error when flushing
1377 or closing.
1378 val close_out_noerr : out_channel -> unit
1382 Same as close_out , but ignore all errors.
1384 val set_binary_mode_out : out_channel -> bool -> unit
1388 set_binary_mode_out oc true sets the channel oc to binary mode: no
1391 translations take place during output. set_binary_mode_out oc false
1392 sets the channel oc to text mode: depending on the operating system,
1393 some translations may take place during output. For instance, under
1394 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1395 tion has no effect under operating systems that do not distinguish
1396 between text mode and binary mode.
1397 === General input functions ===
1402 val open_in : string -> in_channel
1405 Open the named file for reading, and return a new input channel on that
1407 file, positioned at the beginning of the file.
1408 val open_in_bin : string -> in_channel
1412 Same as Pervasives.open_in , but the file is opened in binary mode, so
1414 that no translation takes place during reads. On operating systems that
1415 do not distinguish between text mode and binary mode, this function
1416 behaves like Pervasives.open_in .
1417 val open_in_gen : open_flag list -> int -> string -> in_channel
1421 open_in_gen mode perm filename opens the named file for reading, as
1424 described above. The extra arguments mode and perm specify the opening
1425 mode and file permissions. Pervasives.open_in and Perva‐
1426 sives.open_in_bin are special cases of this function.
1427 val input_char : in_channel -> char
1431 Read one character from the given input channel. Raise End_of_file if
1433 there are no more characters to read.
1434 val input_line : in_channel -> string
1438 Read characters from the given input channel, until a newline character
1440 is encountered. Return the string of all characters read, without the
1441 newline character at the end. Raise End_of_file if the end of the file
1442 is reached at the beginning of line.
1443 val input : in_channel -> bytes -> int -> int -> int
1447 input ic buf pos len reads up to len characters from the given channel
1450 ic , storing them in byte sequence buf , starting at character number
1451 pos . It returns the actual number of characters read, between 0 and
1452 len (inclusive). A return value of 0 means that the end of file was
1453 reached. A return value between 0 and len exclusive means that not all
1454 requested len characters were read, either because no more characters
1455 were available at that time, or because the implementation found it
1456 convenient to do a partial read; input must be called again to read the
1457 remaining characters, if desired. (See also Pervasives.really_input
1458 for reading exactly len characters.) Exception Invalid_argument input
1459 is raised if pos and len do not designate a valid range of buf .
1460 val really_input : in_channel -> bytes -> int -> int -> unit
1464 really_input ic buf pos len reads len characters from channel ic ,
1467 storing them in byte sequence buf , starting at character number pos .
1468 Raise End_of_file if the end of file is reached before len characters
1469 have been read. Raise Invalid_argument really_input if pos and len do
1470 not designate a valid range of buf .
1471 val really_input_string : in_channel -> int -> string
1475 really_input_string ic len reads len characters from channel ic and
1478 returns them in a new string. Raise End_of_file if the end of file is
1479 reached before len characters have been read.
1480 Since 4.02.0
1483 val input_byte : in_channel -> int
1487 Same as Pervasives.input_char , but return the 8-bit integer represent‐
1489 ing the character. Raise End_of_file if an end of file was reached.
1490 val input_binary_int : in_channel -> int
1494 Read an integer encoded in binary format (4 bytes, big-endian) from the
1496 given input channel. See Pervasives.output_binary_int . Raise
1497 End_of_file if an end of file was reached while reading the integer.
1498 val input_value : in_channel -> 'a
1502 Read the representation of a structured value, as produced by Perva‐
1504 sives.output_value , and return the corresponding value. This function
1505 is identical to Marshal.from_channel ; see the description of module
1506 Marshal for more information, in particular concerning the lack of type
1507 safety.
1508 val seek_in : in_channel -> int -> unit
1512 seek_in chan pos sets the current reading position to pos for channel
1515 chan . This works only for regular files. On files of other kinds, the
1516 behavior is unspecified.
1517 val pos_in : in_channel -> int
1521 Return the current reading position for the given channel.
1523 val in_channel_length : in_channel -> int
1527 Return the size (number of characters) of the regular file on which the
1529 given channel is opened. If the channel is opened on a file that is
1530 not a regular file, the result is meaningless. The returned size does
1531 not take into account the end-of-line translations that can be per‐
1532 formed when reading from a channel opened in text mode.
1533 val close_in : in_channel -> unit
1537 Close the given channel. Input functions raise a Sys_error exception
1539 when they are applied to a closed input channel, except close_in ,
1540 which does nothing when applied to an already closed channel.
1541 val close_in_noerr : in_channel -> unit
1545 Same as close_in , but ignore all errors.
1547 val set_binary_mode_in : in_channel -> bool -> unit
1551 set_binary_mode_in ic true sets the channel ic to binary mode: no
1554 translations take place during input. set_binary_mode_out ic false
1555 sets the channel ic to text mode: depending on the operating system,
1556 some translations may take place during input. For instance, under
1557 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1558 tion has no effect under operating systems that do not distinguish
1559 between text mode and binary mode.
1560 === Operations on large files ===
1565 module LargeFile : sig end
1568 Operations on large files. This sub-module provides 64-bit variants of
1571 the channel functions that manipulate file positions and file sizes.
1572 By representing positions and sizes by 64-bit integers (type int64 )
1573 instead of regular integers (type int ), these alternate functions
1574 allow operating on files whose sizes are greater than max_int .
1575 === References ===
1580 type 'a ref = {
1583 mutable contents : 'a ;
1585 }
1586 The type of references (mutable indirection cells) containing a value
1589 of type 'a .
1590 val ref : 'a -> 'a ref
1594 Return a fresh reference containing the given value.
1596 val (!) : 'a ref -> 'a
1600 !r returns the current contents of reference r . Equivalent to fun r
1603 -> r.contents . Unary operator at precedence level 11/11.
1604 val (:=) : 'a ref -> 'a -> unit
1608 r := a stores the value of a in reference r . Equivalent to fun r v ->
1611 r.contents <- v . Right-associative operator at precedence level 1/11.
1612 val incr : int ref -> unit
1616 Increment the integer contained in the given reference. Equivalent to
1618 fun r -> r := succ !r .
1619 val decr : int ref -> unit
1623 Decrement the integer contained in the given reference. Equivalent to
1625 fun r -> r := pred !r .
1626 === Result type ===
1631 type ('a, 'b) result =
1634 | Ok of 'a
1635 | Error of 'b
1636 Since 4.03.0
1639 === Operations on format strings ===
1644 === Format strings are character strings with special lexical conven‐
1647 tions that defines the functionality of formatted input/output func‐
1648 tions. Format strings are used to read data with formatted input func‐
1649 tions from module Scanf and to print data with formatted output func‐
1650 tions from modules Printf and Format. Format strings are made of three
1651 kinds of entities: - conversions specifications, introduced by the spe‐
1652 cial character '%' followed by one or more characters specifying what
1653 kind of argument to read or print, - formatting indications, introduced
1654 by the special character '@' followed by one or more characters speci‐
1655 fying how to read or print the argument, - plain characters that are
1656 regular characters with usual lexical conventions. Plain characters
1657 specify string literals to be read in the input or printed in the out‐
1658 put. There is an additional lexical rule to escape the special charac‐
1659 ters '%' and '@' in format strings: if a special character follows a
1660 '%' character, it is treated as a plain character. In other words, %%
1661 is considered as a plain '%' and %@ as a plain '@'. For more informa‐
1662 tion about conversion specifications and formatting indications avail‐
1663 able, read the documentation of modules Scanf, Printf and Format. ===
1664 === Format strings have a general and highly polymorphic type ('a, 'b,
1667 'c, 'd, 'e, 'f) format6. The two simplified types, format and format4
1668 below are included for backward compatibility with earlier releases of
1669 OCaml. The meaning of format string type parameters is as follows: -
1670 'a is the type of the parameters of the format for formatted output
1671 functions (printf-style functions); 'a is the type of the values read
1672 by the format for formatted input functions (scanf-style functions). -
1673 'b is the type of input source for formatted input functions and the
1674 type of output target for formatted output functions. For printf-style
1675 functions from module Printf, 'b is typically out_channel; for
1676 printf-style functions from module Format, 'b is typically Format.for‐
1677 matter; for scanf-style functions from module Scanf, 'b is typically
1678 Scanf.Scanning.in_channel. Type argument 'b is also the type of the
1679 first argument given to user's defined printing functions for %a and %t
1680 conversions, and user's defined reading functions for %r conversion. -
1681 'c is the type of the result of the %a and %t printing functions, and
1682 also the type of the argument transmitted to the first argument of
1683 kprintf-style functions or to the kscanf-style functions. - 'd is the
1684 type of parameters for the scanf-style functions. - 'e is the type of
1685 the receiver function for the scanf-style functions. - 'f is the final
1686 result type of a formatted input/output function invocation: for the
1687 printf-style functions, it is typically unit; for the scanf-style func‐
1688 tions, it is typically the result type of the receiver function. ===
1689 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1692 linternalFormatBasics.format6
1693 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1698 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1703 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1709 Converts a format string into a string.
1711 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1715 'd, 'e, 'f) format6
1716 format_of_string s returns a format string read from the string literal
1719 s . Note: format_of_string can not convert a string argument that is
1720 not a literal. If you need this functionality, use the more general
1721 Scanf.format_from_string function.
1722 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1726 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1727 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1730 string that behaves as the concatenation of format strings f1 and f2 :
1731 in case of formatted output, it accepts arguments from f1 , then argu‐
1732 ments from f2 ; in case of formatted input, it returns results from f1
1733 , then results from f2 . Right-associative operator at precedence
1734 level 5/11.
1735 === Program termination ===
1740 val exit : int -> 'a
1743 Terminate the process, returning the given status code to the operating
1745 system: usually 0 to indicate no errors, and a small positive integer
1746 to indicate failure. All open output channels are flushed with
1747 flush_all . An implicit exit 0 is performed each time a program termi‐
1748 nates normally. An implicit exit 2 is performed if the program termi‐
1749 nates early because of an uncaught exception.
1750 val at_exit : (unit -> unit) -> unit
1754 Register the given function to be called at program termination time.
1756 The functions registered with at_exit will be called when the program
1757 does any of the following:
1758 -executes Pervasives.exit
1760 -terminates, either normally or because of an uncaught exception
1763 -executes the C function caml_shutdown . The functions are called in
1765 'last in, first out' order: the function most recently added with
1766 at_exit is called first.
1767OCamldoc 2018-07-14 Pervasives(3)