Hi, I'm looking at (say): template <typename Iterator> struct employee_parser : qi::grammar<Iterator, employee(), ascii::space_type> { employee_parser() : employee_parser::base_type(start) { using qi::int_; using qi::lit; using qi::double_; using qi::lexeme; using ascii::char_; quoted_string %= lexeme['"' >> +(char_ - '"') >> '"']; start %= lit("employee") >> '{' >> int_ >> ',' >> quoted_string >> ',' >> quoted_string >> ',' >> double_ >> '}' ; } qi::rule<Iterator, std::string(), ascii::space_type> quoted_string; qi::rule<Iterator, employee(), ascii::space_type> start; }; From http://svn.boost.org/svn/boost/trunk/libs/spirit/doc/html/spirit/qi/tutorial... I can't find any information as to what "%=" does. I know that from previous examples int_ % "," parses a list of ints separated by commas, but there is no information as to what %= does. If I took a guess it seems to imply that: r = r % "," - is equivalent to - r %= "," Can someone point me to some documentation? Kind regards, Samuel