Lecture 19: Monad Transformers

*Exercise 19.1

Compared to the free Functor instance we saw in class, provide a direct implementation:

instance Functor m => Functor (MaybeT m) where ...

*Exercise 19.2

Compared to the free Applicative instance we saw in class, provide a direct implementation:

instance Monad m => Applicative (MaybeT m) where ...