Parser combinator library in C

Re:Parser combinator library in C by drostie on Tuesday August 07, 2012 @08:07AM (#4349657)

It's not bad, but the "0x" is part of the conversion into an integer, not part of the parsed address. That is, the more-complicated-looking combinator converts the string "03-c0" to `Address 3 192`, while it looks like yours converts the string "0x03-0xc0" to to `Address "0x03" "0xc0"`. (I'm not totally sure about that; I'm still very new to Haskell. Thanks for the heads-up on attoparsec though.)

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Re:Parser combinator library in C by tmhedberg on Tuesday August 07, 2012 @08:15AM (#4349672)

The (* >) operator [1] (the space in the middle is just to circumvent HN's rather dumb comment formatting) sequences its two arguments, ignoring the one on the left. So

    string "0x" *> takeWhile1 hexadecimal

parses a literal string "0x", then one or more hexadecimal digits, and the result is just the hexadecimal digits.

[1] http://hackage.haskell.org/packages/archive/base/latest/doc/...

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Re:Parser combinator library in C by dan00 on Tuesday August 07, 2012 @09:14AM (#4349901)

    {-# LANGUAGE OverloadedStrings #-}
    
    import Control.Applicative
    import qualified Data.Attoparsec.Text as P
    import qualified Data.Text as T
    
    data Address = Address {start :: Int, end :: Int} deriving Show
    
    address = Address <$> hexDigits <*> (dash *> hexDigits)
       where
          hexDigits = P.string "0x" *> P.hexadecimal
          dash      = P.char '-'
    
    parse parser str = P.feed (P.parse parser $ T.pack str) T.empty

Put the above into a file like 'parse.hs'.

    ~> ghci parse.hs

    *Main> parse address "0x1-0x1"
    Done "" Address {start = 1, end = 1}

You might need to install attoparsec beforehand:

    cabal install attoparsec

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