{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE FlexibleInstances #-}

module DataTypePractices where

class TooMany a where
  tooMany :: a -> Bool

instance TooMany Int where
  tooMany n = n > 42

instance TooMany (Int, Int) where
  tooMany (n, m) = n + m > 42

newtype Goats =
  Goats Int deriving (Eq, Show, TooMany)

works1 = tooMany (42 :: Int)
works2 = tooMany (43 :: Int)
works3 = tooMany (Goats 42)
works4 = tooMany (Goats 43)

-- does not work
doesNotCompile ((Goats 22), (Goats 22))