Any-sexpr

This is an S-Expression parser and formatter with the following goals:

• Offering direct access to the tokenizer, anysexpr::parse, but also anysexpr::read to build an in-memory tree easily.

• Good error reporting (precise location information and messages).

• (Future) Make the data constructors for anysexpr::read parametrizable (generic), e.g. like in the sexpr_parser crate.

• Streaming: allow to read from and print to file handles lazily, for use e.g. in communications. This currently works by using anysexpr::parse directly for input, or creating tokens to print via a custom loop for output. Future: more possibilities, e.g. turn a tree into a token stream, or parameterize with a tree that's generated on demand while printing.

• (Future) Support various s-expression variants (R*RS, Guile, Clojure, Common Lisp, ..) via runtime (and compile-time?) settings.

• (Perhaps) be usable on microcontrollers (compilable small enough, no-std?).

This is an early alpha version. Even some basics are unfinished (inexact and complex numbers, quoting sugar, some comment styles, ..). The author is quite new to Rust. He is aware of the huge list of API guideline entries not currently being followed, and welcomes help in that area as well as others. The author is also quite invested in lisps and expects to support this library for a long time.

Usage

See examples/main.rs.

Todo

• string escape features on printing
• inexact and complex numbers
• chars: #\x..., #\u..., #\U...
• implement quote/quasiquote/unquote parsing
• handle #| |# and #; style comments
• Guile style keywords #:foo
• performance tuning?, perhaps do not use genawaiter?
• better error behaviour: parser should return errors but try to be able to continue?
• tests (large test corpora, round trip tests, fuzzing)
• handle Guile, Clojure and other syntax versions
• parametrization (generics) for tree generation / mapping (also/vs. Serde?)
• lazy features as mentioned above
• some level of support for pretty-printing

Orthogonally:

• examine the lexpr crate in more detail (missed when researching existing crates before starting this project)

Contact

Christian Jaeger ch@christianjaeger.ch