This post was written for Day 8 of the Racket Advent Calendar. “#lang” is a Racket term referring to declaring the programming language in use, and this post uses Racket as a platform to discuss one approach to writing good programming languages. I’ve made an effort to explain the Racket-specific ideas as they are introduced, so if you are interested in language design but aren’t a Racketeer, I hope you’ll still read it and that you’ll find it interesting.
