Peteris Krumins calls attention to the classic confusion of names that topic maps address in On Functors.
From the post:
It’s interesting how the term “functor” means completely different things in various programming languages. Take C++ for example. Everyone who has mastered C++ knows that you call a class that implements
operator()a functor. Now take Standard ML. In ML functors are mappings from structures to structures. Now Haskell. In Haskell functors are just homomorphisms over containers. And in Prolog functor means the atom at the start of a structure. They all are different. Let’s take a closer look at each one.
Peter has said twice in the first paragraph that each of these “functors” is different. Don’t rush to his 2010 post to point out they are different. That was the point of the post. Yes?
Exercise: All of these uses of functor could be scoped by language. What properties of each “functor” would you use to distinguish them beside their language of origin?