gistfile1.hs

{-# LANGUAGE OverloadedStrings #-}

import Data.Attoparsec.Char8
import Data.Attoparsec.ByteString.Char8
import Data.Word
import Control.Applicative

data IP = IP Int Int Int Int deriving (Show)

parseIP :: Parser IP
parseIP = 
    num8 >>= \d1 -> 
    char '.' >>
    num8 >>= \d2 -> 
    char '.' >>
    num8 >>= \d3 -> 
    char '.' >>
    num8 >>= \d4 -> 
    endOfInput >> (return (IP d1 d2 d3 d4))

num8 :: Integral a => Parser a
num8 = decimal >>= check

check :: (Num a, Ord a) => a -> Parser a
check n
    | n < 256   = return (n)
    | otherwise = fail "what"

main :: IO ()
main = print $ parseOnly parseIP "0.123.123.67"