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Kent Dybvig also wrote Chez Scheme [1] which on most benchmarks is far-and-away the fastest [2] Scheme implementation.

Racket recently got rewritten to be based off of Chez [3] and I have it from the maintainer of Racket himself that it’s paid off well: better performance and a smaller, more maintainable codebase.

1: https://github.com/cisco/ChezScheme (also, pronounced “Shay Scheme”)

2: https://ecraven.github.io/r7rs-benchmarks/

3: https://m.youtube.com/watch?v=s3Q3M2wZ7rI&pp=0gcJCRsBo7VqN5t...

Since these seems to be turning into an opportunity to shout out for other Scheme implementations...

I was a happy use of VSCM by Matthias Blume, doing a bunch of my university assignments with it on my Linux PC in the early 90s.

Amazing, and you could see how this could be translated into perhaps a couple of thousand lines of assembly code to boostrap Scheme almost from the bare metal, similar to the early IBM 709 LISP.

A thought: I wonder if an LLM would be up to the job of writing the assembly code from this?

> note! repl implies there's a top-level but there isn't...

I'm a little confused. How could it not have a top-level environment? There are environments which are extended on function application by consing lists of variables and their values onto the old environment.

  void* extend(void* env, void* vars, void* vals) {
    return cons(cons(vars, vals), env);
  }

This implies a root environment whose cdr is nil.

No matter what I try, I always get:

heap-lisp: heap-lisp.c:99: cons: Assertion `istext(textptr)' failed.

I wonder if the ptr comparison in istext is actually UB?

Instead of representing atoms as string literals, you can represent them as global variables, eg

    const char conti[] = "conti";

Then you can use pointer comparison instead of strcmp().

I believe MIT Scheme compiled directly to C by intermingling switch statements and gotos to emulate its call stack. Problem was, as programs grew, compile times weren't linear. I gave it a shot once, it was a somewhat spiritual experience:

https://github.com/glouw/switch

How much faster or slower than 400 lines compiler? https://news.ycombinator.com/item?id=26191243

Shout out to Mr. Dybvig who taught our intro to CS course at IU Bloomington 20+ years ago! It was my first intro to recursion (of course the class was all scheme based) and gave me much more confidence in software development coming from a self taught background.

Can someone give more info on the relevance of this particular code?

Do Forth bootstrapping now

Have you tested this? Does it work?

What an utterly delightful itty bitty scheme. <3