created_at2020-05-25 00:17:36.57285
updated_at2024-04-02 18:31:51.898623
descriptionA regular expression engine targeting EcmaScript syntax



# regress - REGex in Rust with EcmaScript Syntax oh no why ## Introduction regress is a backtracking regular expression engine implemented in Rust, which targets JavaScript regular expression syntax. See [the crate documentation]( for more. It's fast, Unicode-aware, has few dependencies, and has a big test suite. It makes fewer guarantees than the `regex` crate but it enables more syntactic features, such as backreferences and lookaround assertions. ### Fun Tools The `regress-tool` binary can be used for some fun. You can see how things get compiled with the `dump-phases` cli flag: > cargo run 'x{3,4}' 'i' --dump-phases You can run a little benchmark too, for example: > cargo run --release -- 'abcd' 'i' --bench ~/3200.txt ## Want to contribute? This was my first Rust program so no doubt there is room for improvement. There's lots of stuff still missing, maybe you want to contribute? ### Currently Missing Features - An API for replacing a string while substituting in capture groups (e.g. with `$1`) - An API for escaping a string to make it a literal - Implementing `std::str::pattern::Pattern` ### Missing Performance Optimizations - Anchored matches like `^abc` still perform a string search. We should compute whether the whole regex is anchored, and optimize matching if so. - Non-greedy loops like `.*?` will eagerly compute their maximum match. This doesn't affect correctness but it does mean they may match more than they should. - Pure literal searches should use Boyer-Moore or etc. - There are lots of vectorization opportunities.
Commit count: 132

cargo fmt