[Boost-users] [regex] using partial_match?

[boost 1.53.0] Hello, I'd like to find in a stream of text either "abcd" or "ab". The text is not bounded in size, so I think I should use partial_match. However I present it the following text: "hello abcd, how are you?" it reports to find "ab" and does not wait for the second block to be appended. #include "boost/regex.hpp" int main(int argc, char* argv[]) { boost::regex re ("abcd|ab"); std::string str ("hello abc"); boost::match_resultsstd::string::const_iterator results; bool found = boost::regex_search (str.cbegin(), str.cend(), results, re, boost::regex_constants::match_partial); if (!found || results[0].matched) printf("problem...\n"); return 0; } Am I doing something wrong? I see in the specification that "Specifies that if no match can be found, then ....", isn't this specification flowed? should not it be "if the regular expression engine needs to check past the end of the block of text, and the start matches partially, ...." ? I hope I am wrong and there are good flags to pass.... Regards Armel