> spanLines :: String -> [String]
> spanLines "" = []
> spanLines s  = let (l, s') = span' s
>                in  l : case s' of
>                         []      -> []
>                         (_:s'') -> spanLines s''

> span' []            = ([],[])
> span' xs@(x:xs')
>          | '\n' /= x  =  (x:ys, zs)
>          | otherwise  =  ([],xs)
>                   where ~(ys,zs) = span' xs'

> main = interact (unlines . spanLines)