I had an idea years ago when I still had the young man’s dream about writing a programming language. It came after I took over a J2ME project that was trying to do a great deal of functionality in an 85K jarfile.

That idea was that there should be a little language inside of each big language that is used to implement the self hosting aspects of the language, and then a small set of additional libraries would provide a usable embedded variant of the ecosystem, good for small places and things that have to start quickly.

I like this idea. I believe Rust does something somewhat similar (though not quite) for processing compile-time procedural macros. We see somewhat similar, but external approaches in the Clojure ecosystem with Babashka and Joker (and probably a few others).

In general, I like this, but not every language actually needs it. Like, what would that even be in Python for example?

Something for PyPy perhaps? JITs written in the host language are the original use case I was thinking of, but that’s not the sole domain where it applies.