Example of crazy Num

crazy.hs

data Val = Val Int deriving( Show, Eq )

instance Num Val where
  (Val a) + (Val b) = Val $ max a b
  (Val a) * (Val b) = Val $ a + b
  abs a = a 
  signum _ = (Val 0)
  fromInteger = Val . fromInteger

test1 :: Val -> Bool
test1 a = abs a * signum a == a

val1 :: Val
val1 = fromIntegral 1

val2 :: Val
val2 = fromIntegral 2

test2 = val1 + val1 == val2


main = do
  print $ test1 (Val 2)
  print $ test1 (Val (-3))
  print $ test2