I'm trying 1.31.0rc2. unsigned int flags = boost::match_default; while(regex_search(start, end, what, re, flags)) { ../Test/PlotComplex.cc:36: error: invalid conversion from `unsigned int' to ` boost::regex_constants::_match_flags' But this is exactly what the example: boost_1_31_0_rc2/libs/regex/doc/regex_search.html shows. Need to update the doc?