What should this program print? boost::regex r("(a)"); std::cout << r.mark_count(); My tests show "2". I think the answer should be "1". I see this resolution to TR1 issue 7.22:

7.53 Resolution to DR 7.22 was incomplete Submitter: John Maddock Status: TR The changes made to solve issue 7.22 were incomplete, specifically: p175 section 7.11.1, table 7.16: the entry for m.size() should read: 1 + e.mark_count() This was addressed in issue 7.22, but we missed the fact that this table also has to change to match the change for match_results::size().

If match_results::size() should return regex::mark_count() + 1, then that seems to suggest that regex::mark_count() should return the number of captures, *not including the 0th capture*. Is my reading correct? If so, Boost.Regex is not compliant. FWIW, xpressive reports that the regex "(a)" has a mark_count of 1. Inconsistency == bad. :-( -- Eric Niebler Boost Consulting www.boost-consulting.com