Functional programmers often use the term “reason about code”. It’s not very well defined generally, but I use it myself to refer to our ability to use our real-world intuition in our own code.
Learning to write map is a good lesson because it has recursion, list building, and higher order functions. It’s everything that makes Lisp great.
map is one of the staples of functional programming. It’s totally useful and also surprisingly simple. Let’s look at some examples and annotated code.