basic variable-sized lookbehind implementation#194
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keith-hall merged 6 commits intomainfrom Oct 31, 2025
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use regex-automata's DFA reverse search functionality to support variable (even unbounded) length lookbehinds without fancy features or capture groups
- also improve error handling for when it fails to build a DFA - add benchmarks - update docs to mention the feature flag
- which allows us to have a debug formatting implementation for use in the toy example and playground
…okbehind if it matches once, it doesn't matter whether it will match more times or not, the end result is unaffected
keith-hall
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Oct 17, 2025
robinst
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Oct 31, 2025
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LGTM, just one suggestion. Nice work!
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use regex-automata's DFA reverse search functionality to support variable (even unbounded) length lookbehinds without fancy features or capture groups. Partially fixes #74
Added benchmarks demonstrating that const-size lookbehinds are more efficient:
The variable-size implementation is about 3x slower but still very fast (sub-microsecond), confirming that the const-size optimization continues to work correctly and is worth keeping.
I created a feature flag for this, but I wasn't sure whether it should be part of the default features or not. Oniguruma does apparently support this, so I included it in the default features for now, but if someone has arguments for removing it, I'm happy to hear them.