My advise: implement a simple DFA and use it only for patterns without captures (regex_constants::nosubs) or fancy assertions (eg. look-ahead). If you need captures and leftmost-biased semantics, just use the backtracking NFA.
My intention all along was to see what functionality I could get the DFA to achieve while still being very fast; I hadn't even intended to add look-ahead assertions unless time looked favorable. I'd certainly like to see if I can make captures fast, and from what I've seen, for common regexes without assertions, the DFA really is faster, often considerably. Could you send me the tests you performed? I'd be really interested in it.
Oh, and make the DFA so that I can use it in xpressive, too! :-)
I hadn't looked into xpressive (I'm fairly new to Boost), so I don't know what hurdles that will add, but I'd certainly like to make this functionality as widely available as possible, so thanks for pointing out xpressive. Regards, Hugh Wimberly On 4/12/07, Joel de Guzman <joel@boost-consulting.com> wrote:
Jeff Garland wrote:
Hi All -
I'm happy to announce that Boost will be mentoring 9 Google SoC
Eric Niebler wrote: projects this
year. They are: <snip>
Application to extend Boost regex with recursive matching, named sub-expressions, and automata-based matching Hugh Wimberly John Maddock <snip> [...]
My advise: implement a simple DFA and use it only for patterns without captures (regex_constants::nosubs) or fancy assertions (eg. look-ahead). If you need captures and leftmost-biased semantics, just use the backtracking NFA.
Oh, and make the DFA so that I can use it in xpressive, too! :-)
FWIW, Spirit2 uses lexertl -- a DFA engine by Ben Hanson. Hartmut Kaiser did some benchmarks and found it to be almost as fast as RE2C Hartmut integrated it with Spirit2 and we are very happy with it. There's room for a couple of DFA engines, I guess...
http://re2c.org/ http://www.benhanson.net/lexertl.html
Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net
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