Roadmap

[TotalVerb]

Meta

• [x] Register the SExpressions.jl package

Dependencies

• [ ] Sever FunctionalCollections dependency (use append from a lightweight vocabulary package)

Lisp Parser

• [x] Parse . properly
• [ ] Unquote splicing
• [ ] Add a test suite to check Racket compliance
• [ ] 50% compliance with Racket parsing rules
• [ ] 70% compliance with Racket parsing rules
• [ ] 80% compliance with Racket parsing rules
• [ ] 90% compliance with Racket parsing rules
• [ ] 95% compliance with Racket parsing rules
• [x] Improve the performance of the lisp parser
• [ ] Improve the error messages generated by the lisp parser
• [ ] Keep more syntactic information in the lisp parser

Printing of s-expressions

• [ ] Print improper lists reasonably
• [ ] Improve performance of show (especially multiline)
• [ ] Improve heuristics for multiline show

[mlhetland]

I'm thinking of using I-Expressions for a project (i.e., adding indentation as an optional alternative to parentheses). Is that something that would be of interest as a feature in SExpressions.jl? (If so, I guess this is a “feature request,” but I could also volunteer some effort toward implementing the feature, if need be.)

[mlhetland]

(I'd be fine with a subset of the I-Expression specification; for example, it might make sense to require DEDENTs to match some earlier level of indentation, as in, e.g., Python – but I guess one could issue a warning if this isn't the case.)

[TotalVerb]

@mlhetland I haven't had the time to maintain this package in some time, and don't know if I will have time in the future. So I'd recommend making a new package for what you need.

[c42f]

What's the status of this package, it looks like it is still largely dormant? There's been some talk of having a stdlib for parsing S-Expressions as a utility for testing the julia lowering passes over at https://github.com/JuliaLang/julia/pull/32201.

I think SExpressions could be a starting point for those purposes; would you be happy if we took some code / inspiration from this repository and adapted it to the needs of a stdlib? I think a stdlib might strive to be even more lightweight than what you've got here but I do like what I've seen so far :-)

[TotalVerb]

Hi @c42f, sorry for the late response. I don't think I will necessarily have time to maintain this package in the future. Feel free to take any parts that are correct, lightweight, or helpful, if those parts do exist :smile:.

[c42f]

Awesome, many thanks :-) I'm sure those parts do exist.

[mlhetland]

I have some very lightweight S-expression functionality in Tody. The relevant file is here: expr.jl. Not saying it's a better alternative, but it's very lightweight and reasonably standalone :-). (I use the Call type there, which I define in the Tody.jl file, but it's a trivial wrapper around a vector.)

[c42f]

Thanks, it looks neat.

It turns out that with a few tweaks to make it easier to enter arbitrary Expr heads, I was able to support the needs of Base using normal Julia ASTs. So I probably won't be pursuing a stdlib for this after all.