What are Macros?

Introduction

In the concept of homoiconicity, code is data and data is code. As in all other Lisp-like languages, this gives us access to the full extent of the language to write code-generation routines called macros. As if by magic, macros allow us to extend the language to suit our needs by creating exciting functionalities that can be seen as core functions. It’s also a way of doing metaprogramming in the language itself.

While this feature is available in other programming languages, it’s more commonly found and thoroughly integrated in homoiconic languages like Clojure. However, making use of this feature in other languages requires a deep understanding of all the language’s features, whereas in Clojure, it’s a common and integral aspect.

Compile-time vs. runtime

Clojure is a compiled language in which the compiler reads the source files, produces data structures, and then performs macro expansion, which is also transformed into data structures and compiled as bytecodes to the JVM. Those bytecodes are executed at runtime.

We know that this is a lot and a bit confusing, but it’s important to understand the lifecycle of the macro.

Creating macros