From: boost-users-bounces@lists.boost.org on behalf of TONGARI Sent: Wed 11/24/2010 7:49 AM To: boost-users@lists.boost.org Subject: Re: [Boost-users] [Spirit]Kleene star with arguments havingoptional attributes.
2010/11/24, Paul Graphov <graphov@gmail.com>: 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.
The following works as expected:
std::vector<boost::optional<char> > vec; bool r = qi::parse(begin, end, *('p' | qi::char_), vec);
Why std::string does not? I have no idea, either.
If you can in the future providing a stand alone example describing a problem is very helpful in giving you a good answer. What I see from the simple grammar is that you are looking for a sequence of characters. The 'qi::char_' will parse any single character (see http://www.boost.org/doc/libs/1_45_0/libs/spirit/doc/html/spirit/qi/referenc...). The 'p' is a qi literal which is not meant to be parsed into the output string. I found in a simple example I used below that the 'p' character was placed in the output. I think the | operator used the qi::char_ to parse the 'p' character. Here is my example which places the parsed input string into a std::string. What is happening beneath the code is that the sequence of zero or more characters is that is being placed into a std::vector<char> which happens to be automatically promoted into a std::string. Since I did not have the original email does this solve your problem? Stephen ------------------- #include <boost/spirit/home/qi.hpp> #include <iostream> int main (int, char**) { std::string input = "apapa"; std::string::const_iterator begin = input.begin(); std::string::const_iterator end = input.end(); std::string output; bool r = boost::spirit::qi::parse ( begin, end, *(boost::spirit::qi::lit('p')|boost::spirit::qi::char_), output ); if ( r ) { std::cout << "Success: found - " << output << std::endl; } else { std::cout << "Failed to parse string" << std::endl; } return 0; }