Hello Boost Users, I'm now building configuration file parser with Boost.Spirit. I have a little trouble understanding how this parser builds attribute: It was supposed to parse strings throwing 'p' letter away. *((qi::char_ - 'p') | qi::lit('p')) attribute of qi::lit is Unused. attribute of (qi::char_ - 'p') is char. so attribute of ((qi::char_ - 'p') | qi::lit('p')) should be optional<char> that is uninitialized optional value when matched against character 'p' After applying Kleene star it should became vector<optional<char> >. It seems to be compatible with string (at least it compiles). But 'p' letters are not thrown away. The full example is here: http://pastebin.com/tCMw22Zy The output of that example is: Full parsing Result: "abcpppdef" Is it possible to make such a parser without using semantic actions like [bind(&string::append, res, _1)] or something like that, which seem to be less elegant solution. Thanks!