wordcount.hs

import System.IO (getContents)
import Data.Map (fromListWith, toList)
import Data.List (sortBy)
import Data.Ord (comparing)
import Data.Char (toLower, isLetter)

countedWords = toList . fromListWith (+) . map (flip (,) 1)
showTuple (item, count) = "word: " ++ item ++ " count: " ++ show count
normalized = map toLower . filter isLetter

main = getContents >>= mapM_ (putStrLn . showTuple)
                     . sortBy (flip (comparing snd))
                     . countedWords
                     . map normalized
                     . words