c++ - Boost Karma 对象方法调用

Question

作为我的问题和 answer from sehe 的扩展我想在生成输出时调用一个函数。

我添加了方法 bool isRoby() 并修改了 emp 规则。

   #include <boost/fusion/adapted.hpp>
    #include <boost/spirit/include/karma.hpp>
    #include <boost/spirit/include/phoenix.hpp>
    #include <map>

    namespace karma = boost::spirit::karma;
    namespace phx   = boost::phoenix;

    enum TYPEX { AUTHOR1, AUTHOR2, AUTHOR3, AUTHOR4 };

    std::map<TYPEX, std::string> author2name;
    struct Emp {
        std::string name;
        TYPEX author;

        bool isRoby()
        {
          return name == "roby";
        };
    };

    BOOST_FUSION_ADAPT_STRUCT(Emp, name, author) // boost 1_59
    //BOOST_FUSION_ADAPT_STRUCT(Emp, (std::string, name)(std::string, author)) // older boost

    int main() {
        using it = boost::spirit::ostream_iterator;

        karma::rule<it, std::string()> quote;
        karma::rule<it, TYPEX()> author;
        karma::rule<it, Emp()> emp;

        {
            using namespace karma;
            quote  %= '"' << string << '"';
            author  = quote [ _1 = phx::ref(author2name)[ _val ] ];

            emp    %= delimit('\t')[ quote << author << bool_[ BIND? ] ];

        }

        Emp x { "one", AUTHOR2 };
        author2name[AUTHOR2] = "TWO!";
        std::cout << karma::format(emp, x);
    }

我刚找到 Phoenix Lazy , 但似乎不匹配。

Answer 1

假设您将 isRoby 设为常量:

bool isRoby() const { return name == "roby"; };

您可以使用phx::bind:

bool_ [ _1 = phx::bind(&Emp::isRoby, _val) ]

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#include <boost/fusion/adapted.hpp>
#include <boost/spirit/include/karma.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <map>

namespace karma = boost::spirit::karma;
namespace phx = boost::phoenix;

enum TYPEX { AUTHOR1, AUTHOR2, AUTHOR3, AUTHOR4 };

std::map<TYPEX, std::string> author2name;
struct Emp {
    std::string name;
    TYPEX author;

    bool isRoby() const { return name == "roby"; };
};

BOOST_FUSION_ADAPT_STRUCT(Emp, name, author) // boost 1_59
// BOOST_FUSION_ADAPT_STRUCT(Emp, (std::string, name)(std::string, author)) // older boost

int main() {
    using it = boost::spirit::ostream_iterator;

    karma::rule<it, std::string()> quote;
    karma::rule<it, TYPEX()> author;
    karma::rule<it, Emp()> emp;

    {
        using namespace karma;
        quote %= '"' << string << '"';
        author = quote[_1 = phx::ref(author2name)[_val]];

        emp    %= delimit('\t')[ quote << author << bool_ [ _1 = phx::bind(&Emp::isRoby, _val) ] ];
    }

    Emp x{ "one", AUTHOR2 };
    author2name[AUTHOR2] = "TWO!";
    std::cout << karma::format(emp, x);
}