I'm a bit confused, and need someone to set me straight. Lets outline my current understanding:
Where E is an endofunctor, and A is some category:
E : A -> A.
Since all types and morphisms in Haskell are in the Hask category, is not any functor in Haskell also an endofunctor? F : Hask -> Hask.
I have a good feeling that I'm wrong, and oversimplifying this somehow, and I'd like someone to tell me what an idiot I am. Thanks.