Haskell is not category theory
I&#x27;m confused by his argument that Haskell functors are only endofunctors because everything is Hask.<p>I thought that even if everything is part of one category, if the input is a different category that is a subset of the one category and transformed to another category, even if a subset of the same category, it could still be a regular functor instead of an endofunctor.<p>For example, lets say you had a function f(x) that takes unsigned ints and returns the signed int inverse (so f(1) = -1). -1 is not part of the unsigned category since it is below the Initial value of an unsigned number (0). I&#x27;m a total newbie to category theory so I&#x27;m not sure if he&#x27;s wrong or I&#x27;m missing a key detail here.