The core idea is simple: do a type analysis on each expression you want to "compile" to a closure, and instantiate the correct closure for each type combination.

Here is a pseudocode example, adapted from gomacro sources:

https://gist.github.com/cosmos72/f971c172e71d08030f92a1fc5fa...

This works best for "compiling" statically typed languages, and while much faster than an AST interpreter, the "tree of closures" above is still ~10 times slower that natively compiled code. And it's usually also slower than JIT-compiled code

I put together this example after reading the article:

https://github.com/skx/simple-vm

Simpler than the full gomacro codebase, but perhaps helpful.

For optimal speed, you should move as much code as possible outside the closures.

In particular, you should do the `switch op` at https://github.com/skx/simple-vm/blob/b3917aef0bd6c4178eed0c... outside the closure, and create a different, specialised closure for each case. Otherwise the "fast interpreter" may be almost as slow as a vanilla AST walker.

That's fair, thanks for taking the time to look and giving the feedback.