> lines' :: String -> [String]
> lines' [] = []
> lines' (x:xs) = f x (lines' xs)

> f :: Char -> [String] -> [String]
> f '\n' xss = "" : xss
> f x xss = (x : head0 xss) : tail0 xss

> head0 [] = []
> head0 (ys:yss) = ys

> tail0 [] = []
> tail0 (ys:yss) = yss

> main = interact (unlines . lines')