Clojure has four founding ideas. Firstly, it was set up to be a functional language. It is not pure (as in purely functional), but emphasizes immutability. Secondly, it is a dialect of Lisp; Clojure is malleable enough that users can extend the language without waiting for the language implementers to add new features and constructs. Thirdly, it was built to leverage concurrency for the new generation challenges. Lastly, it was designed to be a hosted language. As of today, Clojure implementations exist for the JVM, CLR, JavaScript, Python, Ruby, and Scheme. Clojure blends seamlessly with its host language.

Clojure is rich in abstractions. Though the syntax itself is very minimal, the abstractions are finely grained, mostly composable, and designed to tackle a wide variety of concerns in the least complicated way. In this chapter, we will discuss the following topics: