1Pervasives(3) OCamldoc Pervasives(3)
2
6 Pervasives - The initially opened module.
7
9 Module Pervasives
10
12 Module Pervasives
13 : sig end
14 The initially opened module.
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 automatically opened at the beginning of each compila‐
23 tion. All components of this module can therefore be referred by their
24 short name, without prefixing them by Pervasives .
25 === Exceptions ===
33 val raise : exn -> 'a
36 Raise the given exception value
38 val raise_notrace : exn -> 'a
42 A faster version raise which does not record the backtrace.
44 Since 4.02.0
47 val invalid_arg : string -> 'a
51 Raise exception Invalid_argument with the given string.
53 val failwith : string -> 'a
57 Raise exception Failure with the given string.
59 exception Exit
63 The Exit exception is not raised by any library function. It is pro‐
66 vided for use in your programs.
67 === Comparisons ===
72 val (=) : 'a -> 'a -> bool
75 e1 = e2 tests for structural equality of e1 and e2 . Mutable struc‐
78 tures (e.g. references and arrays) are equal if and only if their cur‐
79 rent contents are structurally equal, even if the two mutable objects
80 are not the same physical object. Equality between functional values
81 raises Invalid_argument . Equality between cyclic data structures may
82 not terminate.
83 val (<>) : 'a -> 'a -> bool
87 Negation of Pervasives.(=) .
89 val (<) : 'a -> 'a -> bool
93 See Pervasives.(>=) .
95 val (>) : 'a -> 'a -> bool
99 See Pervasives.(>=) .
101 val (<=) : 'a -> 'a -> bool
105 See Pervasives.(>=) .
107 val (>=) : 'a -> 'a -> bool
111 Structural ordering functions. These functions coincide with the usual
113 orderings over integers, characters, strings, byte sequences and float‐
114 ing-point numbers, and extend them to a total ordering over all types.
115 The ordering is compatible with ( = ) . As in the case of ( = ) , muta‐
116 ble structures are compared by contents. Comparison between functional
117 values raises Invalid_argument . Comparison between cyclic structures
118 may not terminate.
119 val compare : 'a -> 'a -> int
123 compare x y returns 0 if x is equal to y , a negative integer if x is
126 less than y , and a positive integer if x is greater than y . The
127 ordering implemented by compare is compatible with the comparison pred‐
128 icates = , < and > defined above, with one difference on the treatment
129 of the float value Pervasives.nan . Namely, the comparison predicates
130 treat nan as different from any other float value, including itself;
131 while compare treats nan as equal to itself and less than any other
132 float value. This treatment of nan ensures that compare defines a
133 total ordering relation.
134 compare applied to functional values may raise Invalid_argument . com‐
137 pare applied to cyclic structures may not terminate.
138 The compare function can be used as the comparison function required by
140 the Set.Make and Map.Make functors, as well as the List.sort and
141 Array.sort functions.
142 val min : 'a -> 'a -> 'a
146 Return the smaller of the two arguments. The result is unspecified if
148 one of the arguments contains the float value nan .
149 val max : 'a -> 'a -> 'a
153 Return the greater of the two arguments. The result is unspecified if
155 one of the arguments contains the float value nan .
156 val (==) : 'a -> 'a -> bool
160 e1 == e2 tests for physical equality of e1 and e2 . On mutable types
163 such as references, arrays, byte sequences, records with mutable fields
164 and objects with mutable instance variables, e1 == e2 is true if and
165 only if physical modification of e1 also affects e2 . On non-mutable
166 types, the behavior of ( == ) is implementation-dependent; however, it
167 is guaranteed that e1 == e2 implies compare e1 e2 = 0 .
168 val (!=) : 'a -> 'a -> bool
172 Negation of Pervasives.(==) .
174 === Boolean operations ===
179 val not : bool -> bool
182 The boolean negation.
184 val (&&) : bool -> bool -> bool
188 The boolean 'and'. Evaluation is sequential, left-to-right: in e1 && e2
190 , e1 is evaluated first, and if it returns false , e2 is not evaluated
191 at all.
192 val (&) : bool -> bool -> bool
196 Deprecated.
198 Pervasives.(&&) should be used instead.
200 val (||) : bool -> bool -> bool
204 The boolean 'or'. Evaluation is sequential, left-to-right: in e1 || e2
206 , e1 is evaluated first, and if it returns true , e2 is not evaluated
207 at all.
208 val (or) : bool -> bool -> bool
212 Deprecated.
214 Pervasives.(||) should be used instead.
216 === Debugging ===
221 val __LOC__ : string
224 __LOC__ returns the location at which this expression appears in the
227 file currently being parsed by the compiler, with the standard error
228 format of OCaml: "File %S, line %d, characters %d-%d".
229 Since 4.02.0
232 val __FILE__ : string
236 __FILE__ returns the name of the file currently being parsed by the
239 compiler.
240 Since 4.02.0
243 val __LINE__ : int
247 __LINE__ returns the line number at which this expression appears in
250 the file currently being parsed by the compiler.
251 Since 4.02.0
254 val __MODULE__ : string
258 __MODULE__ returns the module name of the file being parsed by the com‐
261 piler.
262 Since 4.02.0
265 val __POS__ : string * int * int * int
269 __POS__ returns a tuple (file,lnum,cnum,enum) , corresponding to the
272 location at which this expression appears in the file currently being
273 parsed by the compiler. file is the current filename, lnum the line
274 number, cnum the character position in the line and enum the last char‐
275 acter position in the line.
276 Since 4.02.0
279 val __LOC_OF__ : 'a -> string * 'a
283 __LOC_OF__ expr returns a pair (loc, expr) where loc is the location of
286 expr in the file currently being parsed by the compiler, with the stan‐
287 dard error format of OCaml: "File %S, line %d, characters %d-%d".
288 Since 4.02.0
291 val __LINE_OF__ : 'a -> int * 'a
295 __LINE__ expr returns a pair (line, expr) , where line is the line num‐
298 ber at which the expression expr appears in the file currently being
299 parsed by the compiler.
300 Since 4.02.0
303 val __POS_OF__ : 'a -> (string * int * int * int) * 'a
307 __POS_OF__ expr returns a pair (loc,expr) , where loc is a tuple
310 (file,lnum,cnum,enum) corresponding to the location at which the
311 expression expr appears in the file currently being parsed by the com‐
312 piler. file is the current filename, lnum the line number, cnum the
313 character position in the line and enum the last character position in
314 the line.
315 Since 4.02.0
318 === Composition operators ===
323 val (|>) : 'a -> ('a -> 'b) -> 'b
326 Reverse-application operator: x |> f |> g is exactly equivalent to g (f
328 (x)) .
329 Since 4.01
332 val (@@) : ('a -> 'b) -> 'a -> 'b
336 Application operator: g @@ f @@ x is exactly equivalent to g (f (x)) .
338 Since 4.01
341 === Integer arithmetic ===
346 === Integers are 31 bits wide (or 63 bits on 64-bit processors). All
349 operations are taken modulo 2^{31} (or 2^{63}). They do not fail on
350 overflow. ===
351 val (~-) : int -> int
354 Unary negation. You can also write - e instead of ~- e .
356 val (~+) : int -> int
360 Unary addition. You can also write + e instead of ~+ e .
362 Since 3.12.0
365 val succ : int -> int
369 succ x is x + 1 .
372 val pred : int -> int
376 pred x is x - 1 .
379 val (+) : int -> int -> int
383 Integer addition.
385 val (-) : int -> int -> int
389 Integer subtraction.
391 val ( * ) : int -> int -> int
395 Integer multiplication.
397 val (/) : int -> int -> int
401 Integer division. Raise Division_by_zero if the second argument is 0.
403 Integer division rounds the real quotient of its arguments towards
404 zero. More precisely, if x >= 0 and y > 0 , x / y is the greatest
405 integer less than or equal to the real quotient of x by y . Moreover,
406 (- x) / y = x / (- y) = - (x / y) .
407 val (mod) : int -> int -> int
411 Integer remainder. If y is not zero, the result of x mod y satisfies
413 the following properties: x = (x / y) * y + x mod y and abs(x mod y) <=
414 abs(y) - 1 . If y = 0 , x mod y raises Division_by_zero . Note that x
415 mod y is negative only if x < 0 . Raise Division_by_zero if y is zero.
416 val abs : int -> int
420 Return the absolute value of the argument. Note that this may be nega‐
422 tive if the argument is min_int .
423 val max_int : int
427 The greatest representable integer.
429 val min_int : int
433 The smallest representable integer.
435 === Bitwise operations ===
440 val (land) : int -> int -> int
443 Bitwise logical and.
445 val (lor) : int -> int -> int
449 Bitwise logical or.
451 val (lxor) : int -> int -> int
455 Bitwise logical exclusive or.
457 val lnot : int -> int
461 Bitwise logical negation.
463 val (lsl) : int -> int -> int
467 n lsl m shifts n to the left by m bits. The result is unspecified if m
470 < 0 or m >= bitsize , where bitsize is 32 on a 32-bit platform and 64
471 on a 64-bit platform.
472 val (lsr) : int -> int -> int
476 n lsr m shifts n to the right by m bits. This is a logical shift:
479 zeroes are inserted regardless of the sign of n . The result is
480 unspecified if m < 0 or m >= bitsize .
481 val (asr) : int -> int -> int
485 n asr m shifts n to the right by m bits. This is an arithmetic shift:
488 the sign bit of n is replicated. The result is unspecified if m < 0 or
489 m >= bitsize .
490 === Floating-point arithmetic OCaml's floating-point numbers follow the
495 IEEE 754 standard, using double precision (64 bits) numbers. Float‐
496 ing-point operations never raise an exception on overflow, underflow,
497 division by zero, etc. Instead, special IEEE numbers are returned as
498 appropriate, such as infinity for 1.0 /. 0.0, neg_infinity for -1.0 /.
499 0.0, and nan ('not a number') for 0.0 /. 0.0. These special numbers
500 then propagate through floating-point computations as expected: for
501 instance, 1.0 /. infinity is 0.0, and any arithmetic operation with nan
502 as argument returns nan as result. ===
503 val (~-.) : float -> float
506 Unary negation. You can also write -. e instead of ~-. e .
508 val (~+.) : float -> float
512 Unary addition. You can also write +. e instead of ~+. e .
514 Since 3.12.0
517 val (+.) : float -> float -> float
521 Floating-point addition
523 val (-.) : float -> float -> float
527 Floating-point subtraction
529 val ( *. ) : float -> float -> float
533 Floating-point multiplication
535 val (/.) : float -> float -> float
539 Floating-point division.
541 val ( ** ) : float -> float -> float
545 Exponentiation.
547 val sqrt : float -> float
551 Square root.
553 val exp : float -> float
557 Exponential.
559 val log : float -> float
563 Natural logarithm.
565 val log10 : float -> float
569 Base 10 logarithm.
571 val expm1 : float -> float
575 expm1 x computes exp x -. 1.0 , giving numerically-accurate results
578 even if x is close to 0.0 .
579 Since 3.12.0
582 val log1p : float -> float
586 log1p x computes log(1.0 +. x) (natural logarithm), giving numeri‐
589 cally-accurate results even if x is close to 0.0 .
590 Since 3.12.0
593 val cos : float -> float
597 Cosine. Argument is in radians.
599 val sin : float -> float
603 Sine. Argument is in radians.
605 val tan : float -> float
609 Tangent. Argument is in radians.
611 val acos : float -> float
615 Arc cosine. The argument must fall within the range [-1.0, 1.0] .
617 Result is in radians and is between 0.0 and pi .
618 val asin : float -> float
622 Arc sine. The argument must fall within the range [-1.0, 1.0] .
624 Result is in radians and is between -pi/2 and pi/2 .
625 val atan : float -> float
629 Arc tangent. Result is in radians and is between -pi/2 and pi/2 .
631 val atan2 : float -> float -> float
635 atan2 y x returns the arc tangent of y /. x . The signs of x and y are
638 used to determine the quadrant of the result. Result is in radians and
639 is between -pi and pi .
640 val hypot : float -> float -> float
644 hypot x y returns sqrt(x *. x + y *. y) , that is, the length of the
647 hypotenuse of a right-angled triangle with sides of length x and y ,
648 or, equivalently, the distance of the point (x,y) to origin. If one of
649 x or y is infinite, returns infinity even if the other is nan .
650 Since 4.00.0
653 val cosh : float -> float
657 Hyperbolic cosine. Argument is in radians.
659 val sinh : float -> float
663 Hyperbolic sine. Argument is in radians.
665 val tanh : float -> float
669 Hyperbolic tangent. Argument is in radians.
671 val ceil : float -> float
675 Round above to an integer value. ceil f returns the least integer
677 value greater than or equal to f . The result is returned as a float.
678 val floor : float -> float
682 Round below to an integer value. floor f returns the greatest integer
684 value less than or equal to f . The result is returned as a float.
685 val abs_float : float -> float
689 abs_float f returns the absolute value of f .
692 val copysign : float -> float -> float
696 copysign x y returns a float whose absolute value is that of x and
699 whose sign is that of y . If x is nan , returns nan . If y is nan ,
700 returns either x or -. x , but it is not specified which.
701 Since 4.00.0
704 val mod_float : float -> float -> float
708 mod_float a b returns the remainder of a with respect to b . The
711 returned value is a -. n *. b , where n is the quotient a /. b rounded
712 towards zero to an integer.
713 val frexp : float -> float * int
717 frexp f returns the pair of the significant and the exponent of f .
720 When f is zero, the significant x and the exponent n of f are equal to
721 zero. When f is non-zero, they are defined by f = x *. 2 ** n and 0.5
722 <= x < 1.0 .
723 val ldexp : float -> int -> float
727 ldexp x n returns x *. 2 ** n .
730 val modf : float -> float * float
734 modf f returns the pair of the fractional and integral part of f .
737 val float : int -> float
741 Same as Pervasives.float_of_int .
743 val float_of_int : int -> float
747 Convert an integer to floating-point.
749 val truncate : float -> int
753 Same as Pervasives.int_of_float .
755 val int_of_float : float -> int
759 Truncate the given floating-point number to an integer. The result is
761 unspecified if the argument is nan or falls outside the range of repre‐
762 sentable integers.
763 val infinity : float
767 Positive infinity.
769 val neg_infinity : float
773 Negative infinity.
775 val nan : float
779 A special floating-point value denoting the result of an undefined
781 operation such as 0.0 /. 0.0 . Stands for 'not a number'. Any float‐
782 ing-point operation with nan as argument returns nan as result. As for
783 floating-point comparisons, = , < , <= , > and >= return false and <>
784 returns true if one or both of their arguments is nan .
785 val max_float : float
789 The largest positive finite value of type float .
791 val min_float : float
795 The smallest positive, non-zero, non-denormalized value of type float .
797 val epsilon_float : float
801 The difference between 1.0 and the smallest exactly representable
803 floating-point number greater than 1.0 .
804 type fpclass =
807 | FP_normal (* Normal number, none of the below
808 *)
809 | FP_subnormal (* Number very close to 0.0, has reduced precision
810 *)
811 | FP_zero (* Number is 0.0 or -0.0
812 *)
813 | FP_infinite (* Number is positive or negative infinity
814 *)
815 | FP_nan (* Not a number: result of an undefined operation
816 *)
817 The five classes of floating-point numbers, as determined by the Perva‐
820 sives.classify_float function.
821 val classify_float : float -> fpclass
825 Return the class of the given floating-point number: normal, subnormal,
827 zero, infinite, or not a number.
828 === String operations More string operations are provided in module
833 String. ===
834 val (^) : string -> string -> string
837 String concatenation.
839 === Character operations More character operations are provided in mod‐
844 ule Char. ===
845 val int_of_char : char -> int
848 Return the ASCII code of the argument.
850 val char_of_int : int -> char
854 Return the character with the given ASCII code. Raise Invalid_argument
856 char_of_int if the argument is outside the range 0--255.
857 === Unit operations ===
862 val ignore : 'a -> unit
865 Discard the value of its argument and return () . For instance,
867 ignore(f x) discards the result of the side-effecting function f . It
868 is equivalent to f x; () , except that the latter may generate a com‐
869 piler warning; writing ignore(f x) instead avoids the warning.
870 === String conversion functions ===
875 val string_of_bool : bool -> string
878 Return the string representation of a boolean. As the returned values
880 may be shared, the user should not modify them directly.
881 val bool_of_string : string -> bool
885 Convert the given string to a boolean. Raise Invalid_argument
887 bool_of_string if the string is not true or false .
888 val bool_of_string_opt : string -> bool option
892 Convert the given string to a boolean. Return None if the string is
894 not true or false .
895 Since 4.05
898 val string_of_int : int -> string
902 Return the string representation of an integer, in decimal.
904 val int_of_string : string -> int
908 Convert the given string to an integer. The string is read in decimal
910 (by default), in hexadecimal (if it begins with 0x or 0X ), in octal
911 (if it begins with 0o or 0O ), or in binary (if it begins with 0b or 0B
912 ). The _ (underscore) character can appear anywhere in the string and
913 is ignored. Raise Failure int_of_string if the given string is not a
914 valid representation of an integer, or if the integer represented
915 exceeds the range of integers representable in type int .
916 val int_of_string_opt : string -> int option
920 Same as int_of_string , but returs None instead of raising.
922 Since 4.05
925 val string_of_float : float -> string
929 Return the string representation of a floating-point number.
931 val float_of_string : string -> float
935 Convert the given string to a float. The string is read in decimal (by
937 default) or in hexadecimal (marked by 0x or 0X ). The format of deci‐
938 mal floating-point numbers is [-] dd.ddd (e|E) [+|-] dd , where d
939 stands for a decimal digit. The format of hexadecimal floating-point
940 numbers is [-] 0(x|X) hh.hhh (p|P) [+|-] dd , where h stands for an
941 hexadecimal digit and d for a decimal digit. In both cases, at least
942 one of the integer and fractional parts must be given; the exponent
943 part is optional. The _ (underscore) character can appear anywhere in
944 the string and is ignored. Depending on the execution platforms, other
945 representations of floating-point numbers can be accepted, but should
946 not be relied upon. Raise Failure float_of_string if the given string
947 is not a valid representation of a float.
948 val float_of_string_opt : string -> float option
952 Same as float_of_string , but returns None instead of raising.
954 Since 4.05
957 === Pair operations ===
962 val fst : 'a * 'b -> 'a
965 Return the first component of a pair.
967 val snd : 'a * 'b -> 'b
971 Return the second component of a pair.
973 === List operations More list operations are provided in module List.
978 ===
979 val (@) : 'a list -> 'a list -> 'a list
982 List concatenation. Not tail-recursive (length of the first argument).
984 === Input/output Note: all input/output functions can raise Sys_error
989 when the system calls they invoke fail. ===
990 type in_channel
993 The type of input channel.
996 type out_channel
999 The type of output channel.
1002 val stdin : in_channel
1006 The standard input for the process.
1008 val stdout : out_channel
1012 The standard output for the process.
1014 val stderr : out_channel
1018 The standard error output for the process.
1020 === Output functions on standard output ===
1025 val print_char : char -> unit
1028 Print a character on standard output.
1030 val print_string : string -> unit
1034 Print a string on standard output.
1036 val print_bytes : bytes -> unit
1040 Print a byte sequence on standard output.
1042 Since 4.02.0
1045 val print_int : int -> unit
1049 Print an integer, in decimal, on standard output.
1051 val print_float : float -> unit
1055 Print a floating-point number, in decimal, on standard output.
1057 val print_endline : string -> unit
1061 Print a string, followed by a newline character, on standard output and
1063 flush standard output.
1064 val print_newline : unit -> unit
1068 Print a newline character on standard output, and flush standard out‐
1070 put. This can be used to simulate line buffering of standard output.
1071 === Output functions on standard error ===
1076 val prerr_char : char -> unit
1079 Print a character on standard error.
1081 val prerr_string : string -> unit
1085 Print a string on standard error.
1087 val prerr_bytes : bytes -> unit
1091 Print a byte sequence on standard error.
1093 Since 4.02.0
1096 val prerr_int : int -> unit
1100 Print an integer, in decimal, on standard error.
1102 val prerr_float : float -> unit
1106 Print a floating-point number, in decimal, on standard error.
1108 val prerr_endline : string -> unit
1112 Print a string, followed by a newline character on standard error and
1114 flush standard error.
1115 val prerr_newline : unit -> unit
1119 Print a newline character on standard error, and flush standard error.
1121 === Input functions on standard input ===
1126 val read_line : unit -> string
1129 Flush standard output, then read characters from standard input until a
1131 newline character is encountered. Return the string of all characters
1132 read, without the newline character at the end.
1133 val read_int : unit -> int
1137 Flush standard output, then read one line from standard input and con‐
1139 vert it to an integer. Raise Failure int_of_string if the line read is
1140 not a valid representation of an integer.
1141 val read_int_opt : unit -> int option
1145 Same as read_int_opt , but returs None instead of raising.
1147 Since 4.05
1150 val read_float : unit -> float
1154 Flush standard output, then read one line from standard input and con‐
1156 vert it to a floating-point number. The result is unspecified if the
1157 line read is not a valid representation of a floating-point number.
1158 val read_float_opt : unit -> float option
1162 Flush standard output, then read one line from standard input and con‐
1164 vert it to a floating-point number. Returns None if the line read is
1165 not a valid representation of a floating-point number.
1166 Since 4.05.0
1169 === General output functions ===
1174 type open_flag =
1177 | Open_rdonly (* open for reading.
1178 *)
1179 | Open_wronly (* open for writing.
1180 *)
1181 | Open_append (* open for appending: always write at end of file.
1182 *)
1183 | Open_creat (* create the file if it does not exist.
1184 *)
1185 | Open_trunc (* empty the file if it already exists.
1186 *)
1187 | Open_excl (* fail if Open_creat and the file already exists.
1188 *)
1189 | Open_binary (* open in binary mode (no conversion).
1190 *)
1191 | Open_text (* open in text mode (may perform conversions).
1192 *)
1193 | Open_nonblock (* open in non-blocking mode.
1194 *)
1195 Opening modes for Pervasives.open_out_gen and Pervasives.open_in_gen .
1198 val open_out : string -> out_channel
1202 Open the named file for writing, and return a new output channel on
1204 that file, positioned at the beginning of the file. The file is trun‐
1205 cated to zero length if it already exists. It is created if it does not
1206 already exists.
1207 val open_out_bin : string -> out_channel
1211 Same as Pervasives.open_out , but the file is opened in binary mode, so
1213 that no translation takes place during writes. On operating systems
1214 that do not distinguish between text mode and binary mode, this func‐
1215 tion behaves like Pervasives.open_out .
1216 val open_out_gen : open_flag list -> int -> string -> out_channel
1220 open_out_gen mode perm filename opens the named file for writing, as
1223 described above. The extra argument mode specifies the opening mode.
1224 The extra argument perm specifies the file permissions, in case the
1225 file must be created. Pervasives.open_out and Pervasives.open_out_bin
1226 are special cases of this function.
1227 val flush : out_channel -> unit
1231 Flush the buffer associated with the given output channel, performing
1233 all pending writes on that channel. Interactive programs must be care‐
1234 ful about flushing standard output and standard error at the right
1235 time.
1236 val flush_all : unit -> unit
1240 Flush all open output channels; ignore errors.
1242 val output_char : out_channel -> char -> unit
1246 Write the character on the given output channel.
1248 val output_string : out_channel -> string -> unit
1252 Write the string on the given output channel.
1254 val output_bytes : out_channel -> bytes -> unit
1258 Write the byte sequence on the given output channel.
1260 Since 4.02.0
1263 val output : out_channel -> bytes -> int -> int -> unit
1267 output oc buf pos len writes len characters from byte sequence buf ,
1270 starting at offset pos , to the given output channel oc . Raise
1271 Invalid_argument output if pos and len do not designate a valid range
1272 of buf .
1273 val output_substring : out_channel -> string -> int -> int -> unit
1277 Same as output but take a string as argument instead of a byte
1279 sequence.
1280 Since 4.02.0
1283 val output_byte : out_channel -> int -> unit
1287 Write one 8-bit integer (as the single character with that code) on the
1289 given output channel. The given integer is taken modulo 256.
1290 val output_binary_int : out_channel -> int -> unit
1294 Write one integer in binary format (4 bytes, big-endian) on the given
1296 output channel. The given integer is taken modulo 2^{32. The only
1297 reliable way to read it back is through the Pervasives.input_binary_int
1298 function. The format is compatible across all machines for a given ver‐
1299 sion of OCaml.
1300 val output_value : out_channel -> 'a -> unit
1304 Write the representation of a structured value of any type to a chan‐
1306 nel. Circularities and sharing inside the value are detected and pre‐
1307 served. The object can be read back, by the function Perva‐
1308 sives.input_value . See the description of module Marshal for more
1309 information. Pervasives.output_value is equivalent to Marshal.to_chan‐
1310 nel with an empty list of flags.
1311 val seek_out : out_channel -> int -> unit
1315 seek_out chan pos sets the current writing position to pos for channel
1318 chan . This works only for regular files. On files of other kinds (such
1319 as terminals, pipes and sockets), the behavior is unspecified.
1320 val pos_out : out_channel -> int
1324 Return the current writing position for the given channel. Does not
1326 work on channels opened with the Open_append flag (returns unspecified
1327 results).
1328 val out_channel_length : out_channel -> int
1332 Return the size (number of characters) of the regular file on which the
1334 given channel is opened. If the channel is opened on a file that is
1335 not a regular file, the result is meaningless.
1336 val close_out : out_channel -> unit
1340 Close the given channel, flushing all buffered write operations. Out‐
1342 put functions raise a Sys_error exception when they are applied to a
1343 closed output channel, except close_out and flush , which do nothing
1344 when applied to an already closed channel. Note that close_out may
1345 raise Sys_error if the operating system signals an error when flushing
1346 or closing.
1347 val close_out_noerr : out_channel -> unit
1351 Same as close_out , but ignore all errors.
1353 val set_binary_mode_out : out_channel -> bool -> unit
1357 set_binary_mode_out oc true sets the channel oc to binary mode: no
1360 translations take place during output. set_binary_mode_out oc false
1361 sets the channel oc to text mode: depending on the operating system,
1362 some translations may take place during output. For instance, under
1363 Windows, end-of-lines will be translated from \n to \r\n . This func‐
1364 tion has no effect under operating systems that do not distinguish
1365 between text mode and binary mode.
1366 === General input functions ===
1371 val open_in : string -> in_channel
1374 Open the named file for reading, and return a new input channel on that
1376 file, positioned at the beginning of the file.
1377 val open_in_bin : string -> in_channel
1381 Same as Pervasives.open_in , but the file is opened in binary mode, so
1383 that no translation takes place during reads. On operating systems that
1384 do not distinguish between text mode and binary mode, this function
1385 behaves like Pervasives.open_in .
1386 val open_in_gen : open_flag list -> int -> string -> in_channel
1390 open_in_gen mode perm filename opens the named file for reading, as
1393 described above. The extra arguments mode and perm specify the opening
1394 mode and file permissions. Pervasives.open_in and Perva‐
1395 sives.open_in_bin are special cases of this function.
1396 val input_char : in_channel -> char
1400 Read one character from the given input channel. Raise End_of_file if
1402 there are no more characters to read.
1403 val input_line : in_channel -> string
1407 Read characters from the given input channel, until a newline character
1409 is encountered. Return the string of all characters read, without the
1410 newline character at the end. Raise End_of_file if the end of the file
1411 is reached at the beginning of line.
1412 val input : in_channel -> bytes -> int -> int -> int
1416 input ic buf pos len reads up to len characters from the given channel
1419 ic , storing them in byte sequence buf , starting at character number
1420 pos . It returns the actual number of characters read, between 0 and
1421 len (inclusive). A return value of 0 means that the end of file was
1422 reached. A return value between 0 and len exclusive means that not all
1423 requested len characters were read, either because no more characters
1424 were available at that time, or because the implementation found it
1425 convenient to do a partial read; input must be called again to read the
1426 remaining characters, if desired. (See also Pervasives.really_input
1427 for reading exactly len characters.) Exception Invalid_argument input
1428 is raised if pos and len do not designate a valid range of buf .
1429 val really_input : in_channel -> bytes -> int -> int -> unit
1433 really_input ic buf pos len reads len characters from channel ic ,
1436 storing them in byte sequence buf , starting at character number pos .
1437 Raise End_of_file if the end of file is reached before len characters
1438 have been read. Raise Invalid_argument really_input if pos and len do
1439 not designate a valid range of buf .
1440 val really_input_string : in_channel -> int -> string
1444 really_input_string ic len reads len characters from channel ic and
1447 returns them in a new string. Raise End_of_file if the end of file is
1448 reached before len characters have been read.
1449 Since 4.02.0
1452 val input_byte : in_channel -> int
1456 Same as Pervasives.input_char , but return the 8-bit integer represent‐
1458 ing the character. Raise End_of_file if an end of file was reached.
1459 val input_binary_int : in_channel -> int
1463 Read an integer encoded in binary format (4 bytes, big-endian) from the
1465 given input channel. See Pervasives.output_binary_int . Raise
1466 End_of_file if an end of file was reached while reading the integer.
1467 val input_value : in_channel -> 'a
1471 Read the representation of a structured value, as produced by Perva‐
1473 sives.output_value , and return the corresponding value. This function
1474 is identical to Marshal.from_channel ; see the description of module
1475 Marshal for more information, in particular concerning the lack of type
1476 safety.
1477 val seek_in : in_channel -> int -> unit
1481 seek_in chan pos sets the current reading position to pos for channel
1484 chan . This works only for regular files. On files of other kinds, the
1485 behavior is unspecified.
1486 val pos_in : in_channel -> int
1490 Return the current reading position for the given channel.
1492 val in_channel_length : in_channel -> int
1496 Return the size (number of characters) of the regular file on which the
1498 given channel is opened. If the channel is opened on a file that is
1499 not a regular file, the result is meaningless. The returned size does
1500 not take into account the end-of-line translations that can be per‐
1501 formed when reading from a channel opened in text mode.
1502 val close_in : in_channel -> unit
1506 Close the given channel. Input functions raise a Sys_error exception
1508 when they are applied to a closed input channel, except close_in ,
1509 which does nothing when applied to an already closed channel.
1510 val close_in_noerr : in_channel -> unit
1514 Same as close_in , but ignore all errors.
1516 val set_binary_mode_in : in_channel -> bool -> unit
1520 set_binary_mode_in ic true sets the channel ic to binary mode: no
1523 translations take place during input. set_binary_mode_out ic false
1524 sets the channel ic to text mode: depending on the operating system,
1525 some translations may take place during input. For instance, under
1526 Windows, end-of-lines will be translated from \r\n to \n . This func‐
1527 tion has no effect under operating systems that do not distinguish
1528 between text mode and binary mode.
1529 === Operations on large files ===
1534 module LargeFile : sig end
1537 Operations on large files. This sub-module provides 64-bit variants of
1540 the channel functions that manipulate file positions and file sizes.
1541 By representing positions and sizes by 64-bit integers (type int64 )
1542 instead of regular integers (type int ), these alternate functions
1543 allow operating on files whose sizes are greater than max_int .
1544 === References ===
1549 type 'a ref = {
1552 mutable contents : 'a ;
1554 }
1555 The type of references (mutable indirection cells) containing a value
1558 of type 'a .
1559 val ref : 'a -> 'a ref
1563 Return a fresh reference containing the given value.
1565 val (!) : 'a ref -> 'a
1569 !r returns the current contents of reference r . Equivalent to fun r
1572 -> r.contents .
1573 val (:=) : 'a ref -> 'a -> unit
1577 r := a stores the value of a in reference r . Equivalent to fun r v ->
1580 r.contents <- v .
1581 val incr : int ref -> unit
1585 Increment the integer contained in the given reference. Equivalent to
1587 fun r -> r := succ !r .
1588 val decr : int ref -> unit
1592 Decrement the integer contained in the given reference. Equivalent to
1594 fun r -> r := pred !r .
1595 === Result type ===
1600 type ('a, 'b) result =
1603 | Ok of 'a
1604 | Error of 'b
1605 Since 4.03.0
1608 === Operations on format strings ===
1613 === Format strings are character strings with special lexical conven‐
1616 tions that defines the functionality of formatted input/output func‐
1617 tions. Format strings are used to read data with formatted input func‐
1618 tions from module Scanf and to print data with formatted output func‐
1619 tions from modules Printf and Format. Format strings are made of three
1620 kinds of entities: - conversions specifications, introduced by the spe‐
1621 cial character '%' followed by one or more characters specifying what
1622 kind of argument to read or print, - formatting indications, introduced
1623 by the special character '@' followed by one or more characters speci‐
1624 fying how to read or print the argument, - plain characters that are
1625 regular characters with usual lexical conventions. Plain characters
1626 specify string literals to be read in the input or printed in the out‐
1627 put. There is an additional lexical rule to escape the special charac‐
1628 ters '%' and '@' in format strings: if a special character follows a
1629 '%' character, it is treated as a plain character. In other words, %%
1630 is considered as a plain '%' and %@ as a plain '@'. For more informa‐
1631 tion about conversion specifications and formatting indications avail‐
1632 able, read the documentation of modules Scanf, Printf and Format. ===
1633 === Format strings have a general and highly polymorphic type ('a, 'b,
1636 'c, 'd, 'e, 'f) format6. The two simplified types, format and format4
1637 below are included for backward compatibility with earlier releases of
1638 OCaml. The meaning of format string type parameters is as follows: -
1639 'a is the type of the parameters of the format for formatted output
1640 functions (printf-style functions); 'a is the type of the values read
1641 by the format for formatted input functions (scanf-style functions). -
1642 'b is the type of input source for formatted input functions and the
1643 type of output target for formatted output functions. For printf-style
1644 functions from module Printf, 'b is typically out_channel; for
1645 printf-style functions from module Format, 'b is typically Format.for‐
1646 matter; for scanf-style functions from module Scanf, 'b is typically
1647 Scanf.Scanning.in_channel. Type argument 'b is also the type of the
1648 first argument given to user's defined printing functions for %a and %t
1649 conversions, and user's defined reading functions for %r conversion. -
1650 'c is the type of the result of the %a and %t printing functions, and
1651 also the type of the argument transmitted to the first argument of
1652 kprintf-style functions or to the kscanf-style functions. - 'd is the
1653 type of parameters for the scanf-style functions. - 'e is the type of
1654 the receiver function for the scanf-style functions. - 'f is the final
1655 result type of a formatted input/output function invocation: for the
1656 printf-style functions, it is typically unit; for the scanf-style func‐
1657 tions, it is typically the result type of the receiver function. ===
1658 type ('a, 'b, 'c, 'd, 'e, 'f) format6 = ('a, 'b, 'c, 'd, 'e, 'f) Cam‐
1661 linternalFormatBasics.format6
1662 type ('a, 'b, 'c, 'd) format4 = ('a, 'b, 'c, 'c, 'c, 'd) format6
1667 type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4
1672 val string_of_format : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> string
1678 Converts a format string into a string.
1680 val format_of_string : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c,
1684 'd, 'e, 'f) format6
1685 format_of_string s returns a format string read from the string literal
1688 s . Note: format_of_string can not convert a string argument that is
1689 not a literal. If you need this functionality, use the more general
1690 Scanf.format_from_string function.
1691 val (^^) : ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('f, 'b, 'c, 'e, 'g, 'h)
1695 format6 -> ('a, 'b, 'c, 'd, 'g, 'h) format6
1696 f1 ^^ f2 catenates format strings f1 and f2 . The result is a format
1699 string that behaves as the concatenation of format strings f1 and f2 :
1700 in case of formatted output, it accepts arguments from f1 , then argu‐
1701 ments from f2 ; in case of formatted input, it returns results from f1
1702 , then results from f2 .
1703 === Program termination ===
1708 val exit : int -> 'a
1711 Terminate the process, returning the given status code to the operating
1713 system: usually 0 to indicate no errors, and a small positive integer
1714 to indicate failure. All open output channels are flushed with
1715 flush_all . An implicit exit 0 is performed each time a program termi‐
1716 nates normally. An implicit exit 2 is performed if the program termi‐
1717 nates early because of an uncaught exception.
1718 val at_exit : (unit -> unit) -> unit
1722 Register the given function to be called at program termination time.
1724 The functions registered with at_exit will be called when the program
1725 executes Pervasives.exit , or terminates, either normally or because of
1726 an uncaught exception. The functions are called in 'last in, first
1727 out' order: the function most recently added with at_exit is called
1728 first.
17292018-04-14 source: Pervasives(3)