Welcome to the world of Clojure! If you are here, you probably know a little about Lisp or Clojure, but you don't really have an idea of how things work in this world.
We will get to know Clojure by comparing each feature to what you already know from Java. You will see that there are lists, maps and sets just like in Java, but they are immutable. To work with these kinds of collections, you need a different approach; a different paradigm.
This is what we will try to accomplish in this book, to give you a different way to approach problems. We hope you end up using Clojure in your every day life, but if you don't, we hope you use a new approach toward problem solving.
In this chapter, we will cover the following topics:
Getting to know Clojure
Installing Leiningen
Using a Read Eval Print Loop (REPL)
Installing and using Cursive Clojure
Clojure's simple syntax
Clojure's data types and their relationship to the JVM's data types
Special syntax for functions
Before getting started with Clojure, you should know some of its features and what it shares with Java.
Clojure is a programming language that inherits a lot of characteristics from Lisp. You might think of Lisp as that weird programming language with all the parentheses. You need to keep in mind that Clojure chooses to embrace functional programming. This makes it very different from current mainstream programming languages. You will get to know about immutable data structures and how to write programs without changing variable values.
You will also find that Clojure is a dynamic programming language, which makes it a little easier and faster to write programs than using statically typed languages. There is also the concept of using a REPL, a tool that allows you to connect to a program running environment and change code dynamically. It is a very powerful tool.
At last, you will find out that you can convert Clojure to anything you like. You can create or use a statically typed system and bend the language to become what you like. A good example of this is the core.typed library, which allows you to specify the type information without adding support to the compiler.
