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This is a very cool too but I feel like I'm missing something. This looks like any other PEG parser generator. The only difference I see is that it will automatically handle the case where a valid match starts somewhere other than at the start of the stream. I'm not sure that this constitutes calling it a whole language unto itself.

What separates this from tools like PEG.js[1] or pest[2]?

[1]: https://pegjs.org/ [2]: https://github.com/pest-parser/pest

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For the sake of discussion, here's what the author says: http://rosie-lang.org/blog/2018/02/25/why-rpl.html#why-not-u...

I guess pest is comparable then, but wasn't mature when the author started work on Rosie?

(I'd be curious for a proper comparison, but I'm not really knowledgeable in this area -- I had no idea there were so many alternatives to regex: https://en.wikipedia.org/wiki/Comparison_of_parser_generator...)

Yeah.. that got me thinking too. I would not have called it "new".

As of version 5.10, Perl regex engine implements a complete recursive-descent parsing. Allowing things like Regexp::Grammars[0] to exist. Perl also has a nice PEG parser framework called Pegex[1]

-- [0] - https://metacpan.org/pod/Regexp::Grammars [1] - https://metacpan.org/pod/Pegex

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