It is pretty hilarious. Map is such a common place concept, people are familiar with map and filter over arrays, but OP makes the exact same mistake 90% of people explaining this stuff do. He used Haskell / Idris syntax.
If someone already can intuitively/naturally read Haskell syntax, they've likely already looked at a bunch of these tutorials and read about functor/map.
For those that you're targeting that don't read haskell syntax naturally, explaining something to someone in a language they don't speak is if zero use to them.
The above comment managed to make something people already know confusing.
Monoids are nothing but a design pattern generalizing string append and the empty string.
Functors are simply a design pattern generalizing "map()" over arrays.
Monads are simply a design pattern generalizing "SelectMany()" over arrays.
It turns out that these patterns are significantly more powerful than most programmers realize, and by learning the underlying design pattern you'll be able to recognize novel situations where you can apply them and write much better/simpler code and APIs.
