chaoxu

--ST Monad instead!
lcs :: (Eq a) => [a] -> [a] -> [a]
lcs s' t' = reverse $ build n m
  where
    a = runST $ do  
          b <- newArray ((0,0),(n,m)) 0
          mapM_ (f b) $ range ((0,0),(n,m))
          unsafeFreeze b
    n = length s'
    m = length t'