There's a reference implementation in Java, with countless ports to other languages. I wanted to follow along with the book and actually write the interpreter as I read the chapters, and I arbitrarily chose Typescript as the language for my implementation. One convenient side-effect from that choice is that it's fairly trivial to run the interpreter in the browser, which makes for a fun demo!
If you're interested in reading the source code or running the project locally, you can find my repo here!
I'm still looking to finish the second half of the book, which will implement the same language as a VM, at which point I'd love to revisit the playground and make further improvements to the playground, like:
- Implementing more native functions for Web APIs.
- Making the interpreter async, to support continuously running Lox programs.
- Running the interpreter in a WebWorker.
But so far, I've had a lot of fun with the project! I also have lots of positive things I want to say about Crafting Interpreters that I'll spin off as a separate post, but the gist is that it's a fantastic book for anyone interested in programming language design and implementation!