Duck.hs

module Duck where

class Duck a where
  quack :: a -> String
  feathers :: a -> String


data Person = Person deriving(Show)
data DomesticDuck = DomesticDuck deriving(Show)

instance Duck Person where
  quack _ = "The person imitates a duck."
  feathers _ = "The person takes a feather from the ground and shows it."

instance Duck DomesticDuck where
  quack _ = "Quaaaaaack !"
  feathers _ = "The duck has white and gray feathers."

inTheForest :: (Duck a) => a -> IO ()
inTheForest d = do
  putStrLn $ quack d
  putStrLn $ feathers d
  return ()

main :: IO ()
main = do
  inTheForest Person
  inTheForest DomesticDuck
  return ()