{-# LANGUAGE MultiParamTypeClasses #-}
import Control.Monad

class Collide a b where
    collide :: a -> b -> String
    collide _ _ = ""

data Spaceship = Spaceship
data Asteroid = Asteroid String

instance Show Asteroid where
    show (Asteroid str) = str ++ " asteroid"

instance Collide Spaceship Spaceship where
    collide _ _ = "Space catastrophy"

instance Collide Spaceship Asteroid where
    collide _ a = "Impact with " ++ show a

data Object = Spaceship2 | Asteroid2 String

instance Show Object where
    show Spaceship2 = "Spaceship"
    show (Asteroid2 str) = str ++ " asteroid"

collide2 Spaceship2 Spaceship2 = "Space catastrophy"
collide2 Spaceship2 a@(Asteroid2 _) = "Impact with " ++ show a
collide2 _ _ = ""

main = do  forM_ [collide Spaceship Spaceship,
              collide Spaceship (Asteroid "Big"),
              collide Spaceship (Asteroid "Small")]
             putStrLn
           forM_ [collide2 Spaceship2 Spaceship2,
                  collide2 Spaceship2 (Asteroid2 "Big"),
                  collide2 Spaceship2 (Asteroid2 "Small"),
                  collide2 (Asteroid2 "") (Asteroid2 "")]
             putStrLn