Can we do something similar with functions? The answer is yes: we will represent a tree (or any other structure) with a function itself -- and mind: not with a data structure that is processed by a set of functions, and not either with an object with some methods, but by just a function. Furthermore, we will get a functional data structure, 100% immutable, which if updated produces a new copy of itself. And, we will do all this without using objects; rather, closures will provide the desired results.
How can this work? We shall be applying similar concepts as those we saw earlier in the chapter, so the function will act as a container, and it will produce, as its result, a mapping of its contained values. Let's walk ...
