| Portability | portable |
|---|---|
| Stability | provisional |
| Maintainer | lennart@augustsson.net |
| Safe Haskell | Safe |
Text.Printf
Description
A C printf like formatter.
Synopsis
- printf :: PrintfType r => String -> r
- hPrintf :: HPrintfType r => Handle -> String -> r
- class PrintfType t
- class HPrintfType t
- class PrintfArg a
- class IsChar c
Documentation
printf :: PrintfType r => String -> rSource
Format a variable number of arguments with the C-style formatting string.
The return value is either String or (.
IO a)
The format string consists of ordinary characters and /conversion
specifications/, which specify how to format one of the arguments
to printf in the output string. A conversion specification begins with the
character %, followed by one or more of the following flags:
- left adjust (default is right adjust) + always use a sign (+ or -) for signed conversions 0 pad with zeroes rather than spaces
followed optionally by a field width:
num field width * as num, but taken from argument list
followed optionally by a precision:
.num precision (number of decimal places)
and finally, a format character:
c character Char, Int, Integer, ... d decimal Char, Int, Integer, ... o octal Char, Int, Integer, ... x hexadecimal Char, Int, Integer, ... X hexadecimal Char, Int, Integer, ... u unsigned decimal Char, Int, Integer, ... f floating point Float, Double g general format float Float, Double G general format float Float, Double e exponent format float Float, Double E exponent format float Float, Double s string String
Mismatch between the argument types and the format string will cause an exception to be thrown at runtime.
Examples:
> printf "%d\n" (23::Int) 23 > printf "%s %s\n" "Hello" "World" Hello World > printf "%.2f\n" pi 3.14
hPrintf :: HPrintfType r => Handle -> String -> rSource
class PrintfType t Source
The PrintfType class provides the variable argument magic for
printf . Its implementation is intentionally not visible from
this module. If you attempt to pass an argument of a type which
is not an instance of this class to printf or hPrintf , then
the compiler will report it as a missing instance of PrintfArg .
Instances
class HPrintfType t Source
The HPrintfType class provides the variable argument magic for
hPrintf . Its implementation is intentionally not visible from
this module.
Instances