Implementing a programming language is an experience no programmer should go without; the process fosters a deep understanding of computation, and it's fun! In this article, I've boiled the entire process down to its essence: a 7-line interpreter for a functional (Turing-equivalent) programming language. It takes about 3 minutes to implement. This 7-line interpreter showcases a scalable architecture found in many interpreters--the eval/apply design pattern of Structure and Interpretation of Comp...