Advent of code has come and passed, what should I do now with so much free time? Fear not! The JIT calculator challenge is here. 1. The challenge Back when Rust was in its infancy, the official website featured an example program to showcase the language’s syntax. It was a toy calculator, implemented as an interpreter in 20 lines of code. Why talk about website archaeology, though? We are not here for nostalgia’s sake, are we?