What’s a functor?

Julia decided to use an analogy from Steve’s game to explain the concept of functors.

Julia: Imagine a functor as a special upgrade station in your tower defense game. This station can take any tower and enhance it, but it always outputs a tower - just an improved version.

Steve: That makes sense. So it’s like a consistent way to transform things without changing their core nature?

The term functor originates from category theory, a field of mathematics that deals with complex structures and mappings. In the world of programming, we adopt a simplified version of this concept to make it practical for data manipulation. In simple terms, functors are specialized containers that can hold data and have the ability to apply a function to every piece of data they hold, while keeping the overall structure intact. Imagine them as magic boxes that transform whatever is inside without altering the box itself.

However, not every data container...