Writing arbitrary

CustomArbitrary.hs

-- Functor for Company a b c

  data Company a b c = DeepBlue a c | Something b deriving (Eq, Show)

  instance Functor (Company a b) where
    fmap f (DeepBlue a c) = DeepBlue a (f c)
    fmap f (Something b) = Something b

  instance (Arbitrary a, Arbitrary b, Arbitrary c) => Arbitrary (Company a b c) where
    arbitrary = do
      x <- arbitrary
      y <- arbitrary
      z <- arbitrary
      elements [DeepBlue x z, Something y]