In similar vein to tomp's comment: if someone's interested in the bonus project of implementing macros, I've implemented a simple lisp with first class macros (

In similar vein to tomp's comment: if someone's interested in the bonus project of implementing macros, I've implemented a simple lisp with first class macros (fexprs): http://github.com/akkartik/wart http://github.com/akkartik/wart. Moreover, you can write anonymous macros out of more primitive constructs. Over time it's accumulated other features: http://akkartik.name/post/wart http://akkartik.name/post/wart. But hopefully it's still easy to understand, because it has thorough unit tests. If you have a question about some line of code you can try changing it. Seeing what tests break is a great way to get feedback as you learn, in my experience.