Mask an ip address

IpAddress

import Control.Monad
import Data.Bits
import Data.List
import Data.List.Split
import Data.Word

createMask::Int -> [Word8]
createMask mask = take 4 $ gen mask ++ repeat 0
	where
		gen mask
			|mask >= 8 = 255 : gen (mask - 8)
			|mask < 0 || mask > 32 = error "The mask value must be between 0 and 32"
			|otherwise = [shiftL 255 (8 - mask)]
getIp::String->[Word8]
getIp = map read . splitOn "."

main = forever $ do
	putStrLn "Quel est votre ip?"
	ip <- fmap getIp getLine
	putStrLn "Quel est votre masque?"
	mask <- fmap (createMask . read) getLine
	putStrLn $ intercalate "." $ map show $ zipWith(.&.) mask ip
	putStrLn "-------------------------------------------------"