regex-automata VS regexp2

I believe you're the second person to tell me they were confused by this, so there are probably several others confused but didn't say anything. I've added a warning to the top of regex-automata's README.

For anyone following along at home, we're having a very helpful discussion about the implementation I posted in my sibling comment here: https://github.com/BurntSushi/regex-automata/issues/30

My current technique only gets applied to alternations of simple literals. But the idea is generalizeable and I speculate that it is actually impactful to generalize it.

(I could use '_ => {}' instead of 'None' to save a few more.)

I do find the 'if let' variant to be a bit easier to read. It's optimizing for a particular and somewhat common case, so it does of course overlap with 'match'. But I don't find this particular overlap to be too bad. It's usually pretty clear when to use one vs the other.

But like I said, I could live without 'if let'. It is not a major quality of life enhancement to me. Neither will its impending extensions. i.e., 'if let pattern = foo && some_booolean_condition {'.

[1]: https://github.com/BurntSushi/regex-automata/blob/fbae906823...

[2]: https://github.com/BurntSushi/regex-automata/blob/fbae906823...

(The work on regex-automata 0.2 has been underway for over a year now.](https://github.com/BurntSushi/regex-automata/tree/ag/work) There's a lot done, but still a lot more to go. Once that's done, regex proper should be pretty close to a thin layer that glues regex-syntax, regex-automata, memchr and aho-corasick together. I don't currently expect regex to grow any more dependencies than that. And as it is, aho-corasick and memchr are both optional dependencies. Right now, regex-syntax is the only required dependency, but regex-automata will be added to that list.

regexp2 (1.10.0) - a feature-rich regexp engine for Go. It does not have runtime guarantees like the built-in regexp package, but is compatible with Perl5 and .NET;

https://github.com/dlclark/regexp2 I am going to use .NET engine until I find a workaround for stdlib :(

It's also very useful if you're writing an interpreter which intends to be compatible with something that already needs PCRE support. For example, goja (a JS interpreter) uses regexp2 to support JS's regexp syntax, since JS is not limited to re2.

Compare https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Cheatsheet with https://github.com/dlclark/regexp2 - maybe github.com/dlclark/regexp2 is (almost) what you need.