data Constant =
     IntConstant Int 
   | StringConstant String

instance Show Constant where
  show (IntConstant i)    = "int(" ++ show i ++ ")"
  show (StringConstant s) = "string(" ++ show s ++ ")"

main :: IO ()
main = do
  putStrLn $ show $ IntConstant 1337
  putStrLn $ show $ StringConstant "Hello, world!"