For me, it was writing my own Lisp. I'd strongly recommend giving it a try -- you'll learn about tokenization, parsing, garbage collection, and a bunch of little software development lessons.
Useful for getting started: https://github.com/kanaka/mal
For me, it was writing my own Lisp. I'd strongly recommend giving it a try -- you'll learn about tokenization, parsing, garbage collection, and a bunch of little software development lessons.