For anyone wanting to try something similar yourself, I highly recommend MAL. It's a Lisp dialect designed to be a learning tool: there's a nice guide for implementing the interpreter. It doesn't take much away from the learning, but it really lessens the possible frustration a lot. https://github.com/kanaka/mal/blob/master/process/guide.md

Just in case anyone is interested, here's my implementation in Python 3.5+. I'm guessing it took me about 15 hours to write. https://github.com/dancek/mal/tree/python3-dancek/python3-da...

Of course, Peter Norvig's followup to the linked article may also interest anyone who read this far: http://norvig.com/lispy2.html