import Data.Char

fix f = let x = f x in x

z = fix $ \z -> \f -> \la -> \lb ->
  case (f, la, lb) of
    (f, [], _) -> []
    (f, _, []) -> []
    (f, x:xs, y:ys) -> f x y : z f xs ys

m = fix $ \m -> \f -> \la ->
  case (f, la) of
    (f, []) -> []
    (f, x:xs) -> f x : m f xs

fl = fix $ \fl -> \l ->
  case l of
    ([]) -> []
    (([]:ls)) -> fl ls
    ((x:xs):ls) -> x : fl (xs : ls)

tk = fix $ \tk -> \i -> \l ->
  case (i, l) of
    (0, _) -> []
    (x, []) -> []
    (x, l:ls) -> l : tk (x - 1) ls

rep = \x -> let e = x : rep x in e

u = m chr $ z (+) (
  m (abs . (3-)) $ m ord $ fl $ tk 2 $ rep "grrp")
  $ [5, -11, -11, 4, 0, -78, -78, -99]

-- @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
-- @ Georg, executed in ghci, what is `gutStr u` ??? @
-- @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
--
-- HINT: u :: [Char]
--
-- Rules:
--
-- Functions from libraries: {abs, ord, chr}
--   abs :: Num a => a -> a
--   Example: abs (-5) = 5
--
--   ord :: Char -> Int
--   Example: ord 'A' = 65
--
--   chr :: Int -> Char
--   Example: chr 65 = 'A'
--