Printf − Formatted output functions.
Module Printf
Module
Printf
: sig end
Formatted output functions.
val fprintf : out_channel -> (’a, out_channel, unit) format -> ’a
fprintf outchan format arg1 ... argN formats the arguments arg1 to argN according to the format string format , and outputs the resulting string on the channel outchan .
The format string is a character string which contains two types of objects: plain characters, which are simply copied to the output channel, and conversion specifications, each of which causes conversion and printing of arguments.
Conversion specifications have the following form:
% [flags] [width] [.precision] type
In short, a conversion specification consists in the % character, followed by optional modifiers and a type which is made of one or two characters.
The types and their meanings are:
− d , i : convert an integer argument to signed decimal. The flag # adds underscores to large values for readability.
− u , n , l , L , or N : convert an integer argument to unsigned decimal. Warning: n , l , L , and N are used for scanf , and should not be used for printf . The flag # adds underscores to large values for readability.
− x : convert an integer argument to unsigned hexadecimal, using lowercase letters. The flag # adds a 0x prefix to non zero values.
− X : convert an integer argument to unsigned hexadecimal, using uppercase letters. The flag # adds a 0X prefix to non zero values.
− o : convert an integer argument to unsigned octal. The flag # adds a 0 prefix to non zero values.
− s : insert a string argument.
− S : convert a string argument to OCaml syntax (double quotes, escapes).
− c : insert a character argument.
− C : convert a character argument to OCaml syntax (single quotes, escapes).
− f : convert a floating−point argument to decimal notation, in the style dddd.ddd .
− F : convert a floating−point argument to OCaml syntax ( dddd. or dddd.ddd or d.ddd e+−dd ). Converts to hexadecimal with the # flag (see h ).
− e or E : convert a floating−point argument to decimal notation, in the style d.ddd e+−dd (mantissa and exponent).
− g or G : convert a floating−point argument to decimal notation, in style f or e , E (whichever is more compact). Moreover, any trailing zeros are removed from the fractional part of the result and the decimal−point character is removed if there is no fractional part remaining.
− h or H : convert a floating−point argument to hexadecimal notation, in the style 0xh.hhhh p+−dd (hexadecimal mantissa, exponent in decimal and denotes a power of 2).
− B : convert a boolean argument to the string true or false
− b : convert a boolean argument (deprecated; do not use in new programs).
− ld , li , lu , lx , lX , lo : convert an int32 argument to the format specified by the second letter (decimal, hexadecimal, etc).
− nd , ni , nu , nx , nX , no : convert a nativeint argument to the format specified by the second letter.
− Ld , Li , Lu , Lx , LX , Lo : convert an int64 argument to the format specified by the second letter.
− a : user−defined printer. Take two arguments and apply the first one to outchan (the current output channel) and to the second argument. The first argument must therefore have type out_channel −> ’b −> unit and the second ’b . The output produced by the function is inserted in the output of fprintf at the current point.
− t : same as %a , but take only one argument (with type out_channel −> unit ) and apply it to outchan .
− { fmt %} : convert a format string argument to its type digest. The argument must have the same type as the internal format string fmt .
− ( fmt %) : format string substitution. Take a format string argument and substitute it to the internal format string fmt to print following arguments. The argument must have the same type as the internal format string fmt .
− ! : take no argument and flush the output.
− % : take no argument and output one % character.
− @ : take no argument and output one @ character.
− , : take no argument and output nothing: a no−op delimiter for conversion specifications.
The optional flags are:
− − : left−justify the output (default is right justification).
− 0 : for numerical conversions, pad with zeroes instead of spaces.
− + : for signed numerical conversions, prefix number with a + sign if positive.
−space: for signed numerical conversions, prefix number with a space if positive.
− # : request an alternate formatting style for the integer types and the floating−point type F .
The optional width is an integer indicating the minimal width of the result. For instance, %6d prints an integer, prefixing it with spaces to fill at least 6 characters.
The optional precision is a dot . followed by an integer indicating how many digits follow the decimal point in the %f , %e , %E , %h , and %H conversions or the maximum number of significant digits to appear for the %F , %g and %G conversions. For instance, %.4f prints a float with 4 fractional digits.
The integer in a width or precision can also be specified as * , in which case an extra integer argument is taken to specify the corresponding width or precision . This integer argument precedes immediately the argument to print. For instance, %.*f prints a float with as many fractional digits as the value of the argument given before the float.
val printf : (’a, out_channel, unit) format -> ’a
Same as Printf.fprintf , but output on stdout .
val eprintf : (’a, out_channel, unit) format -> ’a
Same as Printf.fprintf , but output on stderr .
val sprintf : (’a, unit, string) format -> ’a
Same as Printf.fprintf , but instead of printing on an output channel, return a string containing the result of formatting the arguments.
val bprintf : Buffer.t -> (’a, Buffer.t, unit) format -> ’a
Same as Printf.fprintf , but instead of printing on an output channel, append the formatted arguments to the given extensible buffer (see module Buffer ).
val ifprintf : ’b -> (’a, ’b, ’c, unit) format4 -> ’a
Same as Printf.fprintf , but does not print anything. Useful to ignore some material when conditionally printing.
Since 3.10.0
val ibprintf : Buffer.t -> (’a, Buffer.t, unit) format -> ’a
Same as Printf.bprintf , but does not print anything. Useful to ignore some material when conditionally printing.
Since 4.11.0
Formatted output functions with continuations.
val kfprintf : (out_channel -> ’d) -> out_channel -> (’a, out_channel, unit, ’d) format4 -> ’a
Same as fprintf , but instead of returning immediately, passes the out channel to its first argument at the end of printing.
Since 3.09.0
val ikfprintf : (’b -> ’d) -> ’b -> (’a, ’b, ’c, ’d) format4 -> ’a
Same as kfprintf above, but does not print anything. Useful to ignore some material when conditionally printing.
Since 4.01.0
val ksprintf : (string -> ’d) -> (’a, unit, string, ’d) format4 -> ’a
Same as sprintf above, but instead of returning the string, passes it to the first argument.
Since 3.09.0
val kbprintf : (Buffer.t -> ’d) -> Buffer.t -> (’a, Buffer.t, unit, ’d) format4 -> ’a
Same as bprintf , but instead of returning immediately, passes the buffer to its first argument at the end of printing.
Since 3.10.0
val ikbprintf : (Buffer.t -> ’d) -> Buffer.t -> (’a, Buffer.t, unit, ’d) format4 -> ’a
Same as kbprintf above, but does not print anything. Useful to ignore some material when conditionally printing.
Since 4.11.0
Deprecated
val kprintf : (string -> ’b) -> (’a, unit, string, ’b) format4 -> ’a
A deprecated synonym for ksprintf .