Транспонирование матрицы

transpose.hs

transpose :: [[a]] -> [[a]]
transpose xs | any (\ys -> length ys == 0) xs = []
             | otherwise = [h] ++ transpose t
  where (h, t) = (map head xs, map tail xs)
  
-- *Main> transpose [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
-- [[1,4,7],[2,5,8],[3,6,9]]