module Main where
  allEven :: [Integer] -> [Integer]
  allEven [] = []
  allEven (h:t) = if even h then h:allEven t else allEven t

  allEven2 :: [Integer] -> [Integer]
  allEven2 xs = [x | x <- xs, even x]

  allEven3 :: [Integer] -> [Integer]
  allEven3 = filter even

  -- >>> allEven [1, 2, 3, 4, 5, 6]
  -- [2,4,6]
  -- >>> allEven2 [1, 2, 3, 4, 5, 6]
  -- [2,4,6]
  -- >>> allEven3 [1, 2, 3, 4, 5, 6]
  -- [2,4,6]

  main :: IO()
  main =
    print "yes"