找不到Boost.Spirit表达式的重载输出运算符

问题描述

这是的后续跟进。我现在有一个命名空间ast 中的几个数据结构，细分为两个子命名空间（代数和<$ c $

This is a follow-up on this Q&A. I now have several data structures in a namespace ast, subdivided over two sub-namespaces (algebraic and numeric) that correspond to the two different formats that the grammar recognizes.

namespace ast {    
    namespace algebraic {            
        struct occupance
        { 
            char pc; 
            char col;
            int row; 
        };

        using pieces = std::vector<occupance>;

        struct placement 
        { 
            char c; 
            boost::optional<pieces> p; 
        };        
    }

    namespace numeric {            
        struct occupance
        { 
            char pc; 
            int sq; 
        };

        struct range 
        { 
            occupance oc; 
            int sq; 
        };

        using pieces = std::vector<boost::variant<range, occupance>>;

        struct placement 
        { 
            char c; 
            boost::optional<pieces> p; 
        };            
    }

    struct fen 
    { 
        char c; 
        std::vector<boost::variant<numeric::placement, algebraic::placement>> p; 
    };
}        

工作解析器 适当的操作符不再被找到。

the appropriate operators are no longer being found.

In file included from main.cpp:4:
/usr/local/include/boost/optional/optional_io.hpp:47:21: error: invalid operands to binary expression ('basic_ostream<char, std::__1::char_traits<char> >' and 'const std::__1::vector<ast::algebraic::occupance, std::__1::allocator<ast::algebraic::occupance> >')
    else out << ' ' << *v ;
         ~~~~~~~~~~ ^  ~~
main.cpp:79:37: note: in instantiation of function template specialization 'boost::operator<<<char, std::__1::char_traits<char>, std::__1::vector<ast::algebraic::occupance, std::__1::allocator<ast::algebraic::occupance> > >' requested here
            return os << p.c << " " << p.p; 

问题：如何定义各种流运算符以正确打印匹配AST？

Question: how to define the various streaming operators to properly print the matched AST?

推荐答案

这是运行时的ADL。 （什么是参数依赖Lookup（又称为ADL或Koenig Lookup）？）

It's run-of-the-mill ADL. (What is "Argument-Dependent Lookup" (aka ADL, or "Koenig Lookup")?)

重复运算符<< 每个子地址空间或使用ADL钩子标签。

Either duplicate the operator<< for each subnamespace or use an ADL hook "tag".

#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/as_vector.hpp>
#include <boost/fusion/include/io.hpp>
#include <boost/optional/optional_io.hpp>
#include <boost/optional.hpp>
#include <boost/spirit/home/x3.hpp>
#include <boost/spirit/home/x3/support/ast/variant.hpp>
#include <boost/variant.hpp>
#include <iostream>
#include <vector>

namespace x3 = boost::spirit::x3;

namespace ast {
    struct adl_hook;

    template <typename T>
        std::ostream& operator<<(std::ostream& os, std::vector<T> const& v) {
            os << "{"; for (auto const& el : v) os << el << " "; return os << "}";
        }

    namespace algebraic {

        template <typename tag = adl_hook>
            struct occupance_t
        { 
            char pc; 
            char col;
            int row; 
        };

        using occupance = occupance_t<>;

        using pieces = std::vector<occupance>;

        template <typename tag = adl_hook>
        struct placement_t
        { 
            char c; 
            boost::optional<pieces> p; 
        };        

        using placement = placement_t<>;
    }

    namespace numeric {

        template <typename tag = adl_hook>
        struct occupance_t
        { 
            char pc; 
            int sq; 
        };

        using occupance = occupance_t<>;

        struct range 
        { 
            occupance oc; 
            int sq; 
        };

        using piece  = boost::variant<range, occupance>;
        using pieces = std::vector<piece>;

        template <typename tag = adl_hook>
        struct placement_t
        { 
            char c; 
            boost::optional<pieces> p; 
        };            

        using placement = placement_t<>;
    }

    struct fen 
    { 
        char c; 
        using placement = boost::variant<numeric::placement, algebraic::placement>;
        std::vector<placement> p; 
    };

    namespace algebraic {            
        std::ostream& operator<<(std::ostream& os, occupance const& oc)  
        { 
            return os << oc.pc << oc.col << oc.row; 
        }

        std::ostream& operator<<(std::ostream& os, placement const& p)     
        { 
            return os << p.c << " " << p.p; 
        }         
    }   // algebriac

    namespace numeric {
        std::ostream& operator<<(std::ostream& os, occupance const& oc)  
        { 
            return os << oc.pc << oc.sq; 
        }

        std::ostream& operator<<(std::ostream& os, range const& r) 
        { 
            for (auto sq = r.oc.sq; sq <= r.sq; ++sq)
                os << r.oc.pc << sq << " ";
            return os;
        }

        std::ostream& operator<<(std::ostream& os, placement const& p)     
        { 
            return os << p.c << " " << p.p; 
        }         
    }   // numeric
}   // ast

BOOST_FUSION_ADAPT_STRUCT(ast::algebraic::occupance, pc, col, row)
BOOST_FUSION_ADAPT_STRUCT(ast::algebraic::placement, c,  p )

BOOST_FUSION_ADAPT_STRUCT(ast::numeric::occupance, pc, sq)
BOOST_FUSION_ADAPT_STRUCT(ast::numeric::range,     oc, sq)
BOOST_FUSION_ADAPT_STRUCT(ast::numeric::placement, c,  p )

BOOST_FUSION_ADAPT_STRUCT(ast::fen, c,  p )

namespace grammar {        
    auto const colon = x3::lit(':');
    auto const comma = x3::lit(',');
    auto const dash  = x3::lit('-');
    auto const dot   = x3::lit('.');

    template<typename T>
    auto as_rule = [](auto p) { return x3::rule<struct _, T>{} = x3::as_parser(p); };

    auto const piece_type = x3::char_('K') | x3::attr('M');
    auto const color      = x3::char_("BW");

    namespace algebraic {        
        auto const square     = x3::lower >> x3::uint_;
        auto const occupance  = as_rule<ast::algebraic::occupance> ( piece_type >> square      ); 
        auto const pieces     = as_rule<ast::algebraic::pieces>    ( occupance % comma         ); 
        auto const placement  = as_rule<ast::algebraic::placement> ( colon >> color >> -pieces );
    }   // algebraic

    namespace numeric {        
        auto const square     = x3::uint_;
        auto const occupance  = as_rule<ast::numeric::occupance> ( piece_type >> square        ); 
        auto const range      = as_rule<ast::numeric::range>     ( occupance >> dash >> square ); 
        auto const pieces     = as_rule<ast::numeric::pieces>    ( (range | occupance) % comma ); 
        auto const placement  = as_rule<ast::numeric::placement> ( colon >> color >> -pieces   );
    }   // numeric

    auto const fen = as_rule<ast::fen> ( color >> (x3::repeat(2)[numeric::placement] | x3::repeat(2)[algebraic::placement]) >> -dot ); 
}   // grammar

int main() {
    for (std::string const t : {
        "W:Wa1,c1,e1,g1,b2,d2,f2,h2,a3,c3,e3,g3:Bb8,d8,f8,h8,a7,c7,e7,g7,b6,d6,f6,h6",
        "W:BKa1,Ka3:WKb8,Kd8",
        "B:W18,24,27,28,K10,K15:B12,16,20,K22,K25,K29",
        "B:W18,19,21,23,24,26,29,30,31,32:B1,2,3,4,6,7,9,10,11,12",
        "W:B1-20:W31-50",   // initial position
        "W:B:W",            // empty board
        "W:B1:W",           // only black pieces
        "W:B:W50"           // only white pieces
    }) {
        auto b = t.begin(), e = t.end();
        ast::fen data;
        bool ok = phrase_parse(b, e, grammar::fen, x3::space, data);

        std::cout << t << "\n";
        if (ok) {
            std::cout << "\t Parsed: \n" << boost::fusion::as_vector(data) << "\n";
        } else {
            std::cout << "Parse failed:\n";
            std::cout << "\t on input: " << t << "\n";
        }
        if (b != e)
            std::cout << "\t Remaining unparsed: '" << std::string(b, e) << '\n';
    }
}

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