mymaybe.hs

mymaybe.hs

data MyMaybe a = MyNothing | MyJust a deriving (Show)

instance Functor MyMaybe where
  fmap f MyNothing = MyNothing
  fmap f (MyJust a) = MyJust (f a)

instance Applicative MyMaybe where
  pure x = MyJust x
  MyNothing <*> _ = MyNothing
  _ <*> MyNothing = MyNothing
  MyJust f <*> MyJust a = MyJust (f a)

instance Monad MyMaybe where
  return = pure
  MyNothing >>= _ = MyNothing
  MyJust x >>= f = f x