monoid.hs

import Data.Monoid
-- class Monoid m where
--   mempty :: m
--   mappend :: m -> m -> m
--   mconcat = foldr mappend mempty

-- instance Monoid [a] where
--   mepmty = []
--   mappend = (++)


lengthCompare :: String -> String -> Ordering
-- lengthCompare x y = let a = length x `compare` length y
--                         b = x `compare` y
--                     in if a == EQ then b else a
lengthCompare x y =
  (length x `compare` length y) `mappend`
  (vowels x `compare` vowels) `mappend`
  (x `compare` y)
  where vowels x = length . filter (`elem` "aiueo")