Now we understand Clojure's way a little bit better and we have a better grasp of what to look for when we need polymorphism. We understand that when needing a polymorphic function we have several options:
We can implement multimethods if we need a highly customized dispatching mechanism
We can implement multimethods if we need to define a complex inheritance structure
We can implement a protocol and define a custom type that implements that protocol
We can define a protocol and extend existing Java or Clojure types with our custom functions for each type
Polymorphism in Clojure is very powerful. It allows you to extend the functionality of Clojure or Java types that already exist; it feels like adding methods to an interface. The best thing about it is that you don't need to redefine or recompile anything.
In the next chapter, we will talk about concurrency—one of the key features of Clojure. We will learn about the idea of what the identity and values are and how those key concepts make...