[Home] Module Microsoft.FSharp.Text.Printf


Extensible printf-style formatting for numbers and other datatypes

Format specifications are strings with "%" markers indicating format placeholders. Format placeholders consist of:

    %[flags][width][.precision][type]
  

where the type is interpreted as follows:

     %b:         bool, formatted as "true" or "false"
     %s:         string, formatted as its unescaped contents
     %d, %i:     any basic integer type formatted as a decimal integer, signed if the basic integer type is signed.
     %u:         any basic integer type formatted as an unsigned decimal integer
     %x, %X, %o: any basic integer type formatted as an unsigned hexadecimal 
                 (a-f)/Hexadecimal (A-F)/Octal integer
 
     %e, %E, %f, %F, %g, %G: 
                 any basic floating point type (float,float32) formatted
                 using a C-style floating point format specifications, i.e
 
     %e, %E: Signed value having the form [-]d.dddde[sign]ddd where 
                 d is a single decimal digit, dddd is one or more decimal
                 digits, ddd is exactly three decimal digits, and sign 
                 is + or -
 
     %f:     Signed value having the form [-]dddd.dddd, where dddd is one
                 or more decimal digits. The number of digits before the 
                 decimal point depends on the magnitude of the number, and 
                 the number of digits after the decimal point depends on 
                 the requested precision.
 
     %g, %G: Signed value printed in f or e format, whichever is 
                 more compact for the given value and precision.
 
 
    %M:      System.Decimal value
 
    %O:      Any value, printed by boxing the object and using it's ToString method(s)
 
    %A:      Any value, printed by using Microsoft.FSharp.Text.StructuredFormat.Display.any_to_string with the default layout settings 
 
    %a:      A general format specifier, requires two arguments:
                 (1) a function which accepts two arguments:
                     (a) a context parameter of the appropriate type for the
                         given formatting function (e.g. an #System.IO.TextWriter)
                     (b) a value to print
                         and which either outputs or returns appropriate text.
 
                 (2) the particular value to print
 
 
    %t:      A general format specifier, requires one argument:
                 (1) a function which accepts a context parameter of the
                     appropriate type for the given formatting function (e.g. 
                     an #System.IO.TextWriter)and which either outputs or returns 
                     appropriate text.

  Basic integer types are:
     byte,sbyte,int16,uint16,int32,uint32,int64,uint64,nativeint,unativeint
  Basic floating point types are:
     float, float32

 
 The following format patterns are accepted but a warning is printed:

     %h(d|u|x|X|o)
     %l(d|u|x|X|o)

  The following format patterns are now deprecated:

     %Ld, %Li, %Lu, %Lx, %LX, %Lo: same, but an int64
     %nd, %ni, %nu, %nx, %nX, %no: same, but a nativeint
     %Ud, %Ui, %Uu, %Ux, %UX, %Uo: same, but an unsigned int32 (uint32)
     %ULd, %ULi, %ULu, %ULx, %ULX, %ULo: same, but an unsigned int64 (uint64)
     %Und, %Uni, %Unu, %Unx, %UnX, %Uno: same, but an unsigned nativeint (unativeint)
 

Valid flags are:

     0: add zeros instead of spaces to make up the required width
     '-': left justify the result within the width specified
     '+': add a '+' character if the number is positive (to match a '-' sign 
          for negatives)
     ' ': add an extra space if the number is positive (to match a '-' 
              sign for negatives)
 

The printf '#' flag is invalid and a compile-time error will be reported if it is used.

   Printf.printf "Hello %s, %d = %d * %d" "World" 6 2 3;
   Printf.sprintf "Hello %s" "World";
   Printf.printf "Hello %a" output_string "World";
 

Type Definitions

TypeDescription
type BuilderFormat Note: an abbreviation for BuilderFormat<'a,unit>
type BuilderFormat Note: an abbreviation for Format<'a,StringBuilder,unit,'d>
type BuildStringFormat Note: an abbreviation for BuilderFormat<'a,string>
type StringFormat Note: an abbreviation for StringFormat<'a,string>
type StringFormat Note: an abbreviation for Format<'a,unit,string,'d>
type TextWriterFormat Note: an abbreviation for TextWriterFormat<'a,unit>
type TextWriterFormat Note: an abbreviation for Format<'a,TextWriter,unit,'d>

Values

ValueDescription
val bfailwithf : #BuilderFormat<'a,'d> -> 'a
Print to a string buffer and raise an exception with the given result. Helper printers must print to string buffers.
val bfprintf : TextWriter -> #BuilderFormat<'a> -> 'a
Print to a text writer or an OCaml-compatible channel, but intermediary printers write via a buffer, which is often the most convenient way to write intermediary printers. Useful if your primitive printing functions are defined to write to buffers, but you ultimately want to go to a file.
val bprintf : StringBuilder -> #BuilderFormat<'a> -> 'a
Print to a string buffer, which is a StringBuilder
val bsprintf : #BuildStringFormat<'a> -> 'a
Print to a string buffer, which is a StringBuilder. Return the result as a string. Helper printers must print to string buffers.
val btwprintf : #TextWriter -> #BuilderFormat<'a> -> 'a
Print to any subtype of TextWriter, but intermediary printers write via a buffer, which is often the most convenient way to write intermediary printers. Useful if your primitive printing functions are defined to write to buffers, but you ultimately want to go to a file.
val eprintf : #TextWriterFormat<'a> -> 'a
Formatted printing to stderr
val eprintfn : #TextWriterFormat<'a> -> 'a
Formatted printing to stderr, adding a newline
val failwithf : #StringFormat<'a,'d> -> 'a
Print to a string buffer and raise an exception with the given result. Helper printers must return strings.
val fprintf : TextWriter -> #TextWriterFormat<'a> -> 'a
Print to a text writer or an OCaml-compatible channel
val fprintfn : TextWriter -> #TextWriterFormat<'a> -> 'a
Print to a text writer or an OCaml-compatible channel, adding a newline
val kbprintf : (unit -> 'd) -> StringBuilder -> #BuilderFormat<'a,'d> -> 'a
bprintf, but call the given 'final' function to generate the result. See [[kprintf]].
val kbsprintf : (string -> 'd) -> #BuilderFormat<'a,'d> -> 'a
bsprintf, but call the given 'final' function to generate the result. See [[kprintf]].
val kfprintf : (unit -> 'd) -> TextWriter -> #TextWriterFormat<'a,'d> -> 'a
fprintf, but call the given 'final' function to generate the result. See [[kprintf]].
val kprintf : (string -> 'd) -> #StringFormat<'a,'d> -> 'a
printf, but call the given 'final' function to generate the result. For example, these let the printing force a flush after all output has been entered onto the channel, but not before.
val ksprintf : (string -> 'd) -> #StringFormat<'a,'d> -> 'a
sprintf, but call the given 'final' function to generate the result. See [[kprintf]].
val ktwprintf : (unit -> 'd) -> #TextWriter -> #TextWriterFormat<'a,'d> -> 'a
twprintf, but call the given 'final' function to generate the result. See [[kprintf]].
val printf : #TextWriterFormat<'a> -> 'a
Formatted printing to stdout
val printfn : #TextWriterFormat<'a> -> 'a
Formatted printing to stdout, adding a newline
val sprintf : #StringFormat<'a> -> 'a
Print to a string via an internal string buffer and return the result as a string. Helper printers must return strings.
val twprintf : #TextWriter -> #TextWriterFormat<'a> -> 'a
Print to any subtype of the .NET type System.IO.TextWriter
val twprintfn : #TextWriter -> #TextWriterFormat<'a> -> 'a
Print to any subtype of the .NET type System.IO.TextWriter, and add a newline

Deprecated/Unsafe Type Definitions

TypeDescription
type bstring_format

Note: This type has been renamed to BuildStringFormat

The type of formats accepted by printers that produce strings but print intermediate results to buffers Note: an abbreviation for ('a,string) kbuffer_format
type buffer_format

Note: This type has been renamed to BuilderFormat

The type of formats accepted by printers that write to buffers Note: an abbreviation for ('a,unit) kbuffer_format
type kbuffer_format

Note: This type has been renamed to BuilderFormat

The type of formats accepted by print-then-call printers that write to buffers Note: an abbreviation for ('a,StringBuilder,unit,'d) format4
type kstring_format

Note: This type has been renamed to StringFormat

The type of formats accepted by print-then-call printers that produce strings Note: an abbreviation for ('a,unit,string,'d) format4
type ktextwriter_format

Note: This type has been renamed to TextWriterFormat

The type of formats accepted by print-then-call printers that write to an instance of the .NET type System.IO.TextWriter Note: an abbreviation for ('a,TextWriter,unit,'d) format4
type string_format

Note: This type has been renamed to StringFormat

The type of formats accepted by printers that produce strings Note: an abbreviation for ('a,string) kstring_format
type textwriter_format

Note: This type has been renamed to TextWriterFormat

The type of formats accepted by printers that write to an instance of the .NET type System.IO.TextWriter Note: an abbreviation for ('a,unit) ktextwriter_format

See Also

Microsoft.FSharp.Text


Documentation for assembly FSharp.Core, version 1.9.4.19, generated using F# version 1.9.4.19