Transpose a chunk of text in Haskell

transposeText.hs

-- transpose a chunk of text separated by '\n'

transposeText :: String -> String
transposeText text = unlines (transpose' (lines text))

transpose' :: [String] -> [String]
transpose' sentences
    | not (all null sentences) = currentLine : (transpose' (map tail nonEmptySts))
    | otherwise = []
    where   currentLine = [x | x:_ <- nonEmptySts]
            nonEmptySts = filter (not.null) sentences