[moomin]

As a supplement to this for non-Clojure users. You can make an amazingly composable system using pure functions. The point at which you can't is when you want to do something flash that involves a construct (called form) that isn't a function itself. For instance, a variable declaration isn't a function, nor is a type declaration.

To do the kind of magic Stathis has done here requires macros, but not many. I've been hacking Clojure for nearly two years without feeling the need to write one. (That changed two weeks ago.)