Asynchronous operations in Stak Scheme

@raviqqe

May 10, 2025

Contents

• Stak Scheme
• Progress
  • Rust error handling in Scheme
  • The self-embedding compiler
  • Asynchronous operations in virtual machines
• Future work

Stak Scheme

• A bytecode compiler and virtual machine (VM) for Scheme
  • The compiler is written in Scheme.
  • The VM is written in Rust.
• It aims to support the R7RS-small standard.
• Forked from Ribbit Scheme

References

• GitHub
• Website

Progress

• Rust error handling in Scheme
• The self-embedding compiler
• Asynchronous operations in virtual machines

Rust error handling in Scheme

• Stak Scheme could handle errors from Rust in a limited way.
  • Rust primitives return error values.
  • If we check returned values and they are error values, we throw the errors in Scheme.
• In the new implementation of error handling, Rust primitives return Result<V, E> where E is an arbitrary error type.
  • The virtual machine captures such errors if error handlers are assigned in the Scheme side.
  • Then, it continues execution from the points of the error handlers.

Rust error handling in Scheme

• VM implementation in Rust
• Error handler implementation in Scheme

The self-embedding compiler

• The Stak Scheme compiler compiles itself to embed it into the (scheme eval) library while compiling given source codes.
• The article about it

Asynchronous operations in virtual machines

• The Stak Scheme virtual machine now handles asynchronous operations.
• Functions asynchronous potentially are marked with the winter-maybe-async crate.
• The current limitation is that it cannot make asynchronous and synchronous APIs coexist...
  • Feature unification | The Cargo book

Demo

• The REPL on browser thing

Future work

• Synchronous and asynchronous APIs in the same crate
• Unicode support
• Tree shaking
• case-lambda syntax
• define-library syntax in the command line interpreter
• include syntax

Summary

• Building Scheme is fun!