I'm trying to implement a Monad instance. As a simpler example, assume the following:
data Maybee a = Notheeng | Juust a
instance Monad Maybee where
return x = Juust x
Notheeng >>= f = Notheeng
Juust x >>= f = f x
fail _ = Notheeng
This should be the standard implementation of Maybe as far as I know. However, this doesn't compile, because the compiler complains:
No instance for (Applicative Maybee)
and similarly he wants a Functor instance once the Applicative is given.
So: Simple question: Must I always implement Functor and Applicative before I can implement a Monad?