提升精神规则 - 规则连接

Question

我有一个字符串规则对的映射，我想以某种方式创建它们的“联合规则”（rule_t joint_rule;）。如果我这样做：

joint_rule = convert_logformat["%h"] >> convert_logformat["%t"];

与parse_phrase的联合规则匹配字符串

std::string entry = "127.0.0.1 [16/Aug/2012:01:50:02 +0000]";

但如果我以这种方式创建联合规则：

for (it = convert_logformat.begin(); it != convert_logformat.end(); it++)
{
   joint_rule = joint_rule.copy() >> (*it).second.copy();
}

它与相同的字符串不匹配。为什么？我怎样才能获得类似后者的东西？

---

相关代码：

    template <typename Iterator>
bool parse_logentry(Iterator first, Iterator last, std::vector<char>& ip, std::vector<char>& timestamp, std::vector<char>& req, unsigned int& status, unsigned int& transferred_bytes, std::vector<char>& referer, std::vector<char>& ua)
{
    using boost::spirit::qi::char_;
    using boost::spirit::qi::int_;
    using boost::spirit::qi::uint_;
    using boost::spirit::qi::phrase_parse;
    using boost::spirit::ascii::space;
    using boost::spirit::ascii::space_type;
    using boost::phoenix::ref;
    using boost::phoenix::push_back;
    using boost::spirit::qi::_1;
    using boost::spirit::qi::lexeme;
    using boost::spirit::qi::rule;

    typedef boost::spirit::qi::rule<Iterator, std::string(), space_type> rule_t;
    rule_t ip_rule, timestamp_rule, user_rule, req_rule, ref_rule, ua_rule, bytes_rule, status_rule;
    ip_rule %= lexeme[(+char_("0-9."))[ref(ip) = _1]];
    timestamp_rule %= lexeme[('[' >> +(~char_(']')) >> ']')[ref(timestamp) = _1]];
    user_rule %= lexeme[(+~char_(" "))];
    req_rule %= lexeme[('"' >> +(~char_('"')) >> '"')[ref(req) = _1]];
    ref_rule %= lexeme[('"' >> +(~char_('"')) >> '"')[ref(referer) = _1]];
    ua_rule %= lexeme[('"' >> +(~char_('"')) >> '"')[ref(ua) = _1]];
    bytes_rule %= uint_[ref(transferred_bytes) = _1];
    status_rule %= uint_[ref(status) = _1];
    std::map<std::string, rule_t> convert_logformat;
    typename std::map<std::string, rule_t>::iterator it;

    convert_logformat.insert(std::pair<std::string, rule_t>("%h", ip_rule));
    convert_logformat.insert(std::pair<std::string, rule_t>("%t", timestamp_rule));
    //convert_logformat.insert(std::pair<std::string, rule_t>("%r", req_rule));
    //convert_logformat.insert(std::pair<std::string, rule_t>("%>s", status_rule));
    //convert_logformat.insert(std::pair<std::string, rule_t>("%b", bytes_rule));
    //convert_logformat.insert(std::pair<std::string, rule_t>("%u", user_rule));
    //convert_logformat.insert(std::pair<std::string, rule_t>("%{User-agent}i", ua_rule));
    //convert_logformat.insert(std::pair<std::string, rule_t>("%{Referer}i", ref_rule));

    rule_t joint_rule;

    //joint_rule = convert_logformat["%h"] >> convert_logformat["%t"];

    for (it = convert_logformat.begin(); it != convert_logformat.end(); it++)
    {
        joint_rule = joint_rule.copy() >> (*it).second.copy();
        std::cout << (*it).first << ": " << typeid((*it).second).name() << "\n";
    }

    std::cout << "convert_logformath: " << typeid(convert_logformat["%h"]).name() << "\n";

    bool r = phrase_parse(first, last, joint_rule, space);
    if (first != last)
        return false;
    return r;
}