I know you didn't actually mean it but here's an implementation of setf from GNU Emacs: https://gist.github.com/3116185#L1950 https://gist.github.com/3116185#L

I know you didn't actually mean it but here's an implementation of setf from GNU Emacs: https://gist.github.com/3116185#L1950 https://gist.github.com/3116185#L1950 It's actually not hard to understand if you know a bit of elisp. And of course the implementation of Macros is usually the hairiest bits of Lisp code. The thing about Macros is that you don't often want to write them, but when you do they allow you to do amazing things that simply wouldn't be possible without them.