Text.PrintScan

http://okmij.org/ftp/typed-formatting/FPrintScan.html

The initial view to the typed sprintf and sscanf This code defines a simple domain-specific language of string patterns and demonstrates two interpreters of the language: for building strings (sprintf) and parsing strings (sscanf). This code thus solves the problem of typed printf/scanf sharing the same format string posed by Chung-chieh Shan.

Version: The current version is 1.1, Aug 31, 2008.

References

• The complete code with many examples. http://okmij.org/ftp/typed-formatting/PrintScan.hs
• The initial view on typed sprintf and sscanf http://okmij.org/ftp/typed-formatting/PrintScanI.txt
• The message with more explanations, posted on the Haskell mailing list on Sun, 31 Aug 2008 19:40:41 -0700 (PDT)

Documentation

data F a b where

Constructors

FLit :: String -> F a a

FInt :: F a (Int -> a)

FChr :: F a (Char -> a)

FPP :: PrinterParser b -> F a (b -> a)

:^ :: F b c -> F a b -> F a c

data PrinterParser a

Printerparsers (injectionprojection pairs)

Constructors

PrinterParser (a -> String) (String -> Maybe (a, String))

fmt :: (Show b, Read b) => b -> F a (b -> a)

a bit of syntactic sugar to avoid hitting the Shift key too many a time

intp :: F a b -> (String -> a) -> b

The interpreter for printf It implements Asai's accumulator-less alternative to Danvy's functional unparsing

ints :: F a b -> String -> b -> Maybe (a, String)

The interpreter for scanf

sprintf :: F String b -> b

sscanf :: String -> F a b -> b -> Maybe a

showread :: (Show a, Read a) => PrinterParser a

The format specification is first-class. One can build format specification incrementally This is not the case with OCaml's printf/scanf (where the format specification has a weird typing and is not first class).

Primitive Printer/parsers

prefix :: String -> String -> Maybe String

A better prefixOf function prefix patt str --> Just str' if the String patt is the prefix of String str. The result str' is str with patt removed Otherwise, the result is Nothing