monad.lam

class Monad m where {
  return : a -> m a;
  bind : m a -> (a -> m b) -> m b
}

liftM2 : forall a b c m. Monad m => (a -> b -> c) -> m a -> m b -> m c
liftM2 f ma mb = bind ma (\a. bind mb (\b. return (f a b)))

data Maybe a = Nothing | Just a

instance Monad Maybe where {
  return = Just;
  bind ma f = case ma of {
    Nothing -> Nothing;
    Just a -> f a
  }
}

and : Bool -> Bool -> Bool
and a b = case a of {
  true -> b;
  _ -> false
  }

asdf = liftM2 and (Just true) Nothing