I'm attempting to match a floating point literal which can contain several optional tokens. Even though the rule succeeds, it doesn't return all the symbols which make up the token. Example Consider the following. Even though the parser succeeds, it returns only "Km" in the match string. Why is that? I expect "-666.0e-45km". std::string phrase = "-666.0e-45km"; std::string val; std::cout << "res: " << parse_number(phrase.begin(), phrase.end(), val) << std::endl; /* prints "1" */ std::cout << val << std::endl; /* prints "km" */ grammar Here is the grammar which I'm trying to express in Spirit. Notice how it is slightly different from the built-in rule "double_" <number> := <decimal> | "INF" | "-INF" | "NaN" <decimal> := ["-"] <digits> ["." <digits>] [<exp>] [<unit>] <exp> := ("e"|"E") ["+"|"-"] <digits> <digits> := <digit> (<digit> | "_")* <digit> := ('0' - '9') <unit> := <unitChar>* <unitChar> := <alpha> | "%" | "_" | "/" | "$" | any char > 128 // see sys::Unit Code namespace qi = boost::spirit::qi; namespace ascii = boost::spirit::ascii; namespace phoenix = boost::phoenix; template <typename Iterator> struct number_grammar : qi::grammar<Iterator, std::string(), ascii::space_type> { number_grammar() : number_grammar::base_type(number, "number") { using qi::lit; using ascii::char_; using qi::digit; using ascii::string; using qi::alpha; using qi::on_error; using qi::fail; using phoenix::construct; using phoenix::val; unitChar = alpha | char_('%') | char_('_') | char_('/') | char_('$') ; // | any char > 128 // see sys::Unit unit = *unitChar ; digits = digit > *( digit | lit('_') ) ; exp = ( char_('e') | char_('E') ) > -( char_('+') | char_('-') ) > digits ; decimal = -char_('-') > digits > -( char_('.') > digits ) > -exp > -unit ; number = string("INF") | string("-INF") | string("NaN") | decimal ; on_error<fail> ( number, std::cout << val("Error! Expecting ") << qi::_4 // what failed? << val(" here: \"") << construct<std::string>(qi::_3, qi::_2) // iterators to error-pos, end << val("\"") << std::endl ); } qi::rule< Iterator, std::string(), ascii::space_type > number; qi::rule< Iterator, std::string() > decimal; qi::rule< Iterator, std::string() > exp; qi::rule< Iterator, std::string() > digits; qi::rule< Iterator, std::string() > unit; qi::rule< Iterator, char() > unitChar; }; template <typename Iterator> bool parse_number(Iterator first, Iterator last, const std::string& val) { using qi::phrase_parse; using ascii::space; number_grammar<Iterator> grammar; bool r = phrase_parse ( first, /*< start iterator >*/ last, /*< end iterator >*/ grammar, /*< the parser >*/ space, /*< the skip-parser >*/ val ); std::cout << val << std::endl; if (first != last) // fail if we did not get a full match return false; return r; } -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-1-44-0-Problem-with-optional-matchi... Sent from the Boost - Dev mailing list archive at Nabble.com.