sstephenson/s

Baby Scheme interpreter with tail calls and call/cc

{
  "createdAt": "2013-09-03T17:07:00Z",
  "defaultBranch": "master",
  "description": "Baby Scheme interpreter with tail calls and call/cc",
  "fullName": "sstephenson/s",
  "homepage": null,
  "language": "CoffeeScript",
  "name": "s",
  "pushedAt": "2013-09-03T17:11:09Z",
  "stargazersCount": 40,
  "topics": [],
  "updatedAt": "2024-01-28T01:56:06Z",
  "url": "https://github.com/sstephenson/s"
}

This is a baby Scheme interpreter in continuation-passing style with tail calls and call/cc. Written in CoffeeScript, compiled to JavaScript, runs in the browser.

REPL
[Source code]!(s.coffee)

The purpose of this exercise was to help me reach an intuitive understanding of continuations. My approach of structuring continuations as data structures rather than higher-order procedures is based on the ideas in Chapter 5 of Essentials of Programming Languages, 3rd ed.

The code here may be of interest to anyone else without a formal CS education but nonetheless curious about the nature of computing. It may also provide a good jumping-off point for anyone wishing to explore the following:

Graphical programming. Replace the parser with an HTML UI for composing source code and inspecting values.
Threading, concurrency, and scheduling. Adjust the interpreter’s run method to implement green threads, or spawn web workers for multiprocessing.
Macros. Implement quasiquote, unquote, and unquote-splicing. Go all the way with R6RS hygienic macros.
Safe code execution. Bridge a safe subset of JavaScript with Scheme and embed it in your web application for third-party extensions.