Summary

In this chapter, we've explored Clojure's macro system, as well as many of the issues surrounding macros. By now, you should have a grasp of the fundamental concepts of macros, starting with the difference between compile-time and runtime evaluation, and have a mental model that will allow you to move on to writing your own macros if necessary, or to understand macros that have been written by others. The problems of macro hygiene, variable capture, and double evaluation are at the heart of the macro writing process. Knowing all of this will help you write macros, read macros, and, most of all, decide when to write a macro and when not to.

Regardless of whether or not you go on to use macros to write your own Domain-Specific Languages (DSL) in Clojure, you'll already benefit from Clojure macros. The flexibility they provide allows Clojure to be extended by library authors in ways that would simply be impossible without macros. Many commonly used Clojure libraries...