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Comment by brundolf | Hacker News Reader

Plug: for fun I made a (less ambitious) version of this kind of thing for Rust which I ended up being pretty happy with

https://github.com/brundonsmith/rust_lisp

Similarly, Fennel [1] is a Lisp which compiles to Lua, and Lua is well supported in both C++ [2] and Rust [3]. Fennel’s a very reasonable option for delivering S-expression based user interactivity — e.g. REPLs and scriptable config [4].

[1]: https://fennel-lang.org/

[2]: https://github.com/ThePhD/sol2

[3]: https://github.com/amethyst/rlua

[4]: https://git.sr.ht/~ioiojo/include-fnl

This year I experimented a little with a Lisp transpiling to Lua and it was really surprising to me how well Lua fits this purpose. It can treat e.g. if statements as expressions and supports higher order functions as well as tail call optimisation, so mostly you can just map S-Expressions and a couple other basic features 1:1 to Lua code, and while it might not be super readable it will just work.

Fennel combines the simplest general programming language (Lua) with the simplest syntax (homoiconicity). The result is like a Lisp without all the esoterica.

Embedding Fennel in Rust allows you to ship user-facing macros written in Fennel without users having to setup a Lua environment beforehand (e.g. [1]).

[1]: https://git.sr.ht/~ioiojo/kiwi/tree/master/item/tests/data/c...

Lua is very Scheme-like in its compactness and cohesion, but with the table as the fundamental compound data type instead of pairs and vectors. It's also a statement/expression language like Python, rather than just an expression language like a Lisp would be.

The break loop example in the article (^C and continue etc.) probably won't work with these minor also-Lisps.

Finally! Tail calls in rust!

Note that it's probably a very crude implementation of tail-calls - it's the first attempt I've ever made - but I can at least verify that it accomplishes the goal of being able to recurse an arbitrary number of times without blowing the stack

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