Boost精神調試枚舉類（C++ 11）編譯錯誤

Question

我想調試一個簡單的結構，它包含一個枚舉類與BOOST_SPIRIT_DEBUG_NODE，但我總是得到編譯錯誤「C：\ boost \ boost \ spirit \ home \ SUPPORT \ attributes.hpp：1226：錯誤：無法綁定 '的std :: basic_ostream' 左值到 '的std :: basic_ostream & &' 近 '了< < VAL;'」

我不知道爲什麼我得到這樣的右值錯誤，我試圖爲運算符< <增加一個手動超載，但是這也不起作用。

我使用boost 1.55，並嘗試在Windows 8.1 x64上使用MinGW 32位gcc 4.8進行編譯。

當我將enum類更改爲默認的C++枚舉時，它可以工作，但我想使用新的枚舉類進行適當的名稱空間處理。

Answer 1

I don't know why I get a rvalue error like that, I tried to to add a manual overload for the operator<< for the enum class but that didn't work either.

我認爲需要的代碼，因爲這確實工作：

1. 首先，用經典枚舉Live on Coliru

   #define BOOST_SPIRIT_DEBUG 
   #include <boost/spirit/include/qi.hpp> 
   #include <iostream> 
   
   namespace qi = boost::spirit::qi; 
   
   struct data_t 
   { 
       std::string label; 
       enum Choice { left, right, up, down } choice; 
   
       data_t(std::string label="default", Choice choice=left): label(std::move(label)), choice(choice) {} 
   
       friend std::ostream& operator<<(std::ostream& os, Choice const& v) { 
        switch(v) { 
         case left: return os << "left"; 
         case right:return os << "right"; 
         case up: return os << "up"; 
         case down: return os << "down"; 
         default: return os << "?"; 
        } 
       } 
       friend std::ostream& operator<<(std::ostream& os, data_t const& v) { 
        return os << "{label:" << v.label << ";choice:" << v.choice << "}"; 
       } 
   }; 
   
   
   template <typename It, typename Skipper = qi::space_type> 
       struct parser : qi::grammar<It, data_t(), Skipper> 
   { 
       parser() : parser::base_type(start) 
       { 
        using namespace qi; 
   
        choice_.add 
         ("left", data_t::left) 
         ("right", data_t::right) 
         ("up", data_t::up) 
         ("down", data_t::down); 
   
        start %= as_string[ lexeme[+graph] ] >> lexeme [choice_]; 
   
        BOOST_SPIRIT_DEBUG_NODE(start); 
       } 
   
   private: 
       qi::symbols<char, data_t::Choice> choice_; 
       qi::rule<It, data_t(), Skipper> start; 
   }; 
   
   bool doParse(const std::string& input) 
   { 
       typedef std::string::const_iterator It; 
       auto f(begin(input)), l(end(input)); 
   
       parser<It, qi::space_type> p; 
       data_t data; 
   
       try 
       { 
        bool ok = qi::phrase_parse(f,l,p,qi::space,data); 
        if (ok) 
        { 
         std::cout << "parse success\n"; 
         std::cout << "data: " << data << "\n"; 
        } 
        else  std::cerr << "parse failed: '" << std::string(f,l) << "'\n"; 
   
        if (f!=l) std::cerr << "trailing unparsed: '" << std::string(f,l) << "'\n"; 
        return ok; 
       } catch(const qi::expectation_failure<It>& e) 
       { 
        std::string frag(e.first, e.last); 
        std::cerr << e.what() << "'" << frag << "'\n"; 
       } 
   
       return false; 
   } 
   
   int main() 
   { 
       bool ok = doParse("label1 up"); 
       return ok? 0 : 255; 
   } 
   

2. 其次與枚舉類Live on Coliru

   #define BOOST_SPIRIT_DEBUG 
   #include <boost/spirit/include/qi.hpp> 
   #include <iostream> 
   
   namespace qi = boost::spirit::qi; 
   
   struct data_t 
   { 
       std::string label; 
       enum class Choice { left, right, up, down } choice; 
   
       data_t(std::string label="default", Choice choice=Choice::left): label(std::move(label)), choice(choice) {} 
   
       friend std::ostream& operator<<(std::ostream& os, Choice const& v) { 
        switch(v) { 
         case Choice::left: return os << "left"; 
         case Choice::right:return os << "right"; 
         case Choice::up: return os << "up"; 
         case Choice::down: return os << "down"; 
         default: return os << "?"; 
        } 
       } 
       friend std::ostream& operator<<(std::ostream& os, data_t const& v) { 
        return os << "{label:" << v.label << ";choice:" << v.choice << "}"; 
       } 
   }; 
   
   
   template <typename It, typename Skipper = qi::space_type> 
       struct parser : qi::grammar<It, data_t(), Skipper> 
   { 
       parser() : parser::base_type(start) 
       { 
        using namespace qi; 
   
        choice_.add 
         ("left", data_t::Choice::left) 
         ("right", data_t::Choice::right) 
         ("up", data_t::Choice::up) 
         ("down", data_t::Choice::down); 
   
        start %= as_string[ lexeme[+graph] ] >> lexeme [choice_]; 
   
        BOOST_SPIRIT_DEBUG_NODE(start); 
       } 
   
   private: 
       qi::symbols<char, data_t::Choice> choice_; 
       qi::rule<It, data_t(), Skipper> start; 
   }; 
   
   bool doParse(const std::string& input) 
   { 
       typedef std::string::const_iterator It; 
       auto f(begin(input)), l(end(input)); 
   
       parser<It, qi::space_type> p; 
       data_t data; 
   
       try 
       { 
        bool ok = qi::phrase_parse(f,l,p,qi::space,data); 
        if (ok) 
        { 
         std::cout << "parse success\n"; 
         std::cout << "data: " << data << "\n"; 
        } 
        else  std::cerr << "parse failed: '" << std::string(f,l) << "'\n"; 
   
        if (f!=l) std::cerr << "trailing unparsed: '" << std::string(f,l) << "'\n"; 
        return ok; 
       } catch(const qi::expectation_failure<It>& e) 
       { 
        std::string frag(e.first, e.last); 
        std::cerr << e.what() << "'" << frag << "'\n"; 
       } 
   
       return false; 
   } 
   
   int main() 
   { 
       bool ok = doParse("label1 up"); 
       return ok? 0 : 255; 
   } 
   

我的猜測是你忘了系列化添加到您的任何枚舉或你的結構。