wisp

I also based my Zig Lisp interpreter on delimited continuations and had a great time implementing async, resumable exceptions, dynamically scoped variables, and so on, on top of that. The single-stepping continuation-shuffling evaluation paradigm also made it really easy to expose evaluations as objects and stepping as a function. A simple form like (set! e (run (+ 1 1)) stores an evaluation—whose continuation and lexical environment can both be inspected and serialized—and (step! e) does a single evaluation step. This lets you implement not just yield-based cooperative concurrency in "user space" but something like green threads with a preemptive scheduler. Here you can see how the delimited continuation control allows binding to JavaScript's Promise API in a way that lets you treat promises as blocking computations: https://gi