Interesting. I am currently in the process of writing an interpreter for a similar stack based language. I already wrote a compiler for this language to x86 assembly that can be compiled to an ELF. The language is used as an intermediate language for a C compiler that I am writing. It is maybe less Forth-like than your language. For more information see: https://github.com/FransFaase/MES-replacement For the interpreter have a look at: stack_c_interpreter.c

At WHY2025, I gave a talk about the reasons why am working on this. See: https://www.youtube.com/watch?v=akzyyO5wvm0

Another thread on small forth interpreters from just 15 days ago:

https://news.ycombinator.com/item?id=45039301

Forth can be beautifully and efficiently implemented in portable c++ using the using continuation passing style via the clang musttail attribute.

Have a look at Tails (not my project):

[1] https://github.com/snej/tails

If you're interested in learning more about how FORTH works I, I can recommend two very old books.

Starting FORTH https://archive.org/details/LeoBrodieStartingFORTHIntroducti...

Threaded Interpretive Languages https://archive.org/details/R.G.LoeligerThreadedInterpretive...

The latter doesn't even mention FORTH, and describes some very archaic CPU architectures, but I found it fascinating because it builds things from the ground up.

1. You should add a URL when you you create a post on HN. You can indent code two spaces on HN, eg:

  Stack s;
  stack_init(&s);
  dict_init();
  exec(&s, "10 20 + ."); // Prints "30"
  exec(&s, "1 2 3 4 .s"); // Shows stack contents

2. Your readme mentions a repl but I don't see it in the source code.

3. I'm not an expert in C but I thought header files shouldn't have code in them. The code should be in a .c file

4. Maybe move the code from USAGE into its own .c file.

  #include "stacklib.h"
  
  int main() {
    Stack s;
    stack_init(&s);
    dict_init();
    exec(&s, "10 20 + .");
    printf("\n");
    return 0;
  }

Your experiment is certainly a good tool to grok stack mechanics, but that is only one element of what makes a Forth what it is. You're missing out on other crucial ingredients: colon definition and immediateness.

I wrote a series of articles that can help in that kind of discovery: http://tumbleforth.hardcoded.net/