OCaml library : Printf (original) (raw)

Module Printf

module Printf: sig .. end

Formatted output functions.

val fprintf : [out_channel](Stdlib.html#TYPEout%5Fchannel) -> ('a, [out_channel](Stdlib.html#TYPEout%5Fchannel), unit) [format](Stdlib.html#TYPEformat) -> 'a

fprintf outchan format arg1 ... argN formats the argumentsarg1 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 typeout_channel -> 'b -> unit and the second 'b. The output produced by the function is inserted in the output offprintf at the current point.
• t: same as %a, but take only one argument (with typeout_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 stringfmt.
• ( 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](Stdlib.html#TYPEout%5Fchannel), unit) [format](Stdlib.html#TYPEformat) -> 'a

val eprintf : ('a, [out_channel](Stdlib.html#TYPEout%5Fchannel), unit) [format](Stdlib.html#TYPEformat) -> 'a

val sprintf : ('a, unit, string) [format](Stdlib.html#TYPEformat) -> '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](Buffer.html#TYPEt) -> ('a, [Buffer.t](Buffer.html#TYPEt), unit) [format](Stdlib.html#TYPEformat) -> '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](Stdlib.html#TYPEformat4) -> 'a

Same as Printf.fprintf, but does not print anything. Useful to ignore some material when conditionally printing.

• Since 3.10

val ibprintf : [Buffer.t](Buffer.html#TYPEt) -> ('a, [Buffer.t](Buffer.html#TYPEt), unit) [format](Stdlib.html#TYPEformat) -> 'a

Same as Printf.bprintf, but does not print anything. Useful to ignore some material when conditionally printing.

• Since 4.11

Formatted output functions with continuations.

val kfprintf : ([out_channel](Stdlib.html#TYPEout%5Fchannel) -> 'd) -> [out_channel](Stdlib.html#TYPEout%5Fchannel) -> ('a, [out_channel](Stdlib.html#TYPEout%5Fchannel), unit, 'd) [format4](Stdlib.html#TYPEformat4) -> '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

val ikfprintf : ('b -> 'd) -> 'b -> ('a, 'b, 'c, 'd) [format4](Stdlib.html#TYPEformat4) -> 'a

Same as kfprintf above, but does not print anything. Useful to ignore some material when conditionally printing.

• Since 4.01

val ksprintf : (string -> 'd) -> ('a, unit, string, 'd) [format4](Stdlib.html#TYPEformat4) -> 'a

Same as sprintf above, but instead of returning the string, passes it to the first argument.

• Since 3.09

val kbprintf : ([Buffer.t](Buffer.html#TYPEt) -> 'd) -> [Buffer.t](Buffer.html#TYPEt) -> ('a, [Buffer.t](Buffer.html#TYPEt), unit, 'd) [format4](Stdlib.html#TYPEformat4) -> 'a

Same as bprintf, but instead of returning immediately, passes the buffer to its first argument at the end of printing.

• Since 3.10

val ikbprintf : ([Buffer.t](Buffer.html#TYPEt) -> 'd) -> [Buffer.t](Buffer.html#TYPEt) -> ('a, [Buffer.t](Buffer.html#TYPEt), unit, 'd) [format4](Stdlib.html#TYPEformat4) -> 'a

Same as kbprintf above, but does not print anything. Useful to ignore some material when conditionally printing.

• Since 4.11

Deprecated

val kprintf : (string -> 'b) -> ('a, unit, string, 'b) [format4](Stdlib.html#TYPEformat4) -> 'a

Deprecated. Use Printf.ksprintf instead.

A deprecated synonym for ksprintf.