module Data.Caesar where

type Caesar = Char

next :: Char -> Char
next c =
  case c of
     '.' -> '.'
     ' ' -> ' '
     'ö' -> 'ä'
     'ä' -> 'å'
     'å' -> 'z'
     'a' -> 'ö'
     x   -> pred x

caesar :: Int -> Caesar -> Caesar
caesar n x = foldr ($) x (replicate n next)