uri parser

typedef std::map<std::string, std::string> TQuery;
struct Uri
{
    std::string scheme;
    std::string host;
    std::string path;
    TQuery query;
};
BOOST_FUSION_ADAPT_STRUCT(
        Uri,
        (std::string, scheme)
        (std::string, host)
        (std::string, path)
        (TQuery, query)
)


template<class Iterator>
struct UriGrammar : public boost::spirit::qi::grammar<Iterator, Uri()> {



    UriGrammar() :UriGrammar::base_type(uri)
    {
        namespace qi = boost::spirit::qi;
        typedef qi::rule<Iterator, std::string()> StringArgRule;
        typedef qi::rule<Iterator, std::map<std::string, std::string>()> MapArgRule;
        typedef qi::rule<Iterator, std::pair<std::string, std::string>()> PairArgRule;

        StringArgRule scheme = *qi::alnum >> "://";
        StringArgRule host = qi::alnum >> *(qi::alnum | qi::char_("."));

        StringArgRule path = qi::char_('/') >> *(qi::alnum | qi::char_("/."));

        StringArgRule queryParamName = *qi::alnum;
        StringArgRule    queryParamValue = *(qi::alnum |qi::char_('%') );

        PairArgRule queryPair = queryParamName >> '=' >> queryParamValue;
        MapArgRule query = qi::lit('?') >> (queryPair % '&');
        uri = scheme >> host >> path >> query;
    }

    boost::spirit::qi::rule<Iterator, Uri()> uri;
};
int main()
{

    Uri uriStruct;

    bool parsed = qi::parse(uri.begin(), uri.end(), UriGrammar<std::string::iterator>(), uriStruct);

    std::cout << uriStruct.host << std::endl;
}