It's not bad, but the "0x" is part of the conversion into an integer, not part o...

tmhedberg · on Aug 7, 2012

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/...

dan00 · on Aug 7, 2012

    {-# 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