gistfile1.hs

{-# LANGUAGE OverloadedStrings #-}

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

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

parseIP :: Parser IP
parseIP = do
    d1 <- (check decimal)
    char '.'
    d2 <- (check decimal)
    char '.'
    d3 <- (check decimal)
    char '.'
    d4 <- (check decimal)
    endOfInput
    return (IP d1 d2 d3 d4)

check :: (Num a, Ord a) => Parser a -> Parser a
check p = p >>= check1 
    
check1 :: (Num a, Ord a) => a -> Parser a
check1 n
    | n < 256   = return (n)
    | otherwise = fail "what"


main :: IO ()
main = print $ parseOnly parseIP "256.123.123.123"