I noticed some surprising behavior with match_partial and regex_search. Consider: regex e("abc|b"); string str("ab"); smatch what; if(regex_search(str, what, e, match_default | match_partial)) { cout << (what[0].matched ? "full" : "partial") << '\n'; } This code displays "partial". Clearly, regex_search is bombing out just as soon as it finds a match, partial or otherwise. But in this case, if it kept looking, it would find a full match. My understanding is that full matches are always preferred to partial matches. I couldn't find any discussion about this case in the regex docs or the std proposal. Did I miss it? What's the intention here? Is the std proposal underspecified? -- Eric Niebler Boost Consulting www.boost-consulting.com