Hacker News Reader

Comment by natmaster | Hacker News Reader

What kind of licensing does this have?

It would be interesting to see if this could make it in Python 3.2 (It's supposed to include the Unladen Swallow stuff, so might as well take more awesomeness from Google.)

View on HN

The 3-clause BSD license...

http://github.com/axiak/pyre2/blob/master/LICENSE

It won't. It doesn't implement the entire regular expression language Python supports.

Could a regex library parse a regular expression and decide reasonably quickly which engine to use?

Probably, but python-core has no interest in maintaining multiple regular expression implementations: http://mail.python.org/pipermail/python-dev/2010-July/101606... (this thread starts talking about regex, which is a backwards compatible enhancement to re, but also covers re2)

Yes. That's precisely what pyre2 is doing. It's trying re2, and if it fails because it doesn't support the features, it tries the python re. Since compilation happens rarely, this is fast.

Please note that RE2 doesn't support backtracking.

if you're using backtracking, maybe "regular expressions" aren't the right tool.

What would be the right tool, then?

Grammars are a good start. Mix in parse-controlling predicates if that isn't powerful enough (C++).

note it depends upon cython: i suppose it's more likely it will make it into cython rather than python 3.2.

Like the libxml module which uses Cython, the compiled CPP module is distributed along with it, so you don't actually need Cython to install it or compile it. But you would need Cython to do any development on it.

BSD (as does the google RE2 C++ module)

Reply on news.ycombinator.com