words.hs

import Data.List
import Data.Function
import Control.Arrow
import qualified Data.HashMap.Strict as M
import qualified Data.ByteString.Lazy.Char8 as BL
import qualified Data.ByteString.Char8 as BS
import Text.Printf

histo = M.toList . foldl' (\m x -> M.insertWith (+) x (1 :: Int) m) M.empty

count = sortBy (flip (compare `on` snd)) . histo . map BL.toStrict . BL.words

main  = BL.getContents >>= mapM_ print . count where
  print (s, n) = printf "- %s : %d\n" (BS.unpack s) n

--
-- ghc -O2 --make words.hs
--

Also.