c – 如何从精神语法中将原始输入捕获到合成输出中？

我正在研究一个boost :: spirit :: qi :: grammar,并希望将原始文本的一部分复制到语法的合成输出结构中(更具体地说,是匹配规则的一个组成部分的部分) ).语法最终将被用作更复杂语法的子语法,因此我实际上无法访问原始输入.

我猜这可以通过语义动作或语法上下文来完成,但是我无法找到一个没有访问原始解析()的例子.

这是我到目前为止所拥有的：

#include <iostream>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/fusion/include/adapt_struct.hpp>

namespace qi = boost::spirit::qi;

struct A
{
    std::string header;
    std::vector<int> ints;
    std::string inttext;
};

BOOST_FUSION_ADAPT_STRUCT(
    A,
    (std::string, header)
    (std::vector<int>, ints)
    //(std::string, inttext)
)

template <typename Iterator>
struct parser : qi::grammar< Iterator, A() >
{
    parser() : parser::base_type(start)
    {
        header %= qi::lexeme[ +qi::alpha ];
        ints %= qi::lexeme[ qi::int_ % qi::char_(",_") ]; // <---- capture the original text that matches this into inttext
        start %= header >> ' ' >> ints;
    }

    qi::rule<Iterator, std::string()> header;
    qi::rule<Iterator, std::vector<int>() > ints;
    qi::rule<Iterator, A()> start;
};

int main()
{
    A output;
    std::string input("out 1,2_3");
    auto iter = input.begin();
    parser<decltype(iter)> p;
    bool r = qi::parse(iter, input.end(), p, output);
    if( !r || iter != input.end() )
    {
        std::cout << "did not parse";
    }
    else
    {
        // would like output.inttext to be "1,2_3"
        std::cout << output.header << ": " << output.inttext << " -> [ ";
        for( auto & i: output.ints )
            std::cout << i << ' ';
        std::cout << ']' << std::endl;
    }
}

解决方法:

类似于您在不使用语义操作时提出的问题：

#include <iostream>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/spirit/repository/include/qi_iter_pos.hpp>

namespace qi = boost::spirit::qi;
using boost::spirit::repository::qi::iter_pos;

struct ints_type
{
   std::vector<int> data;
   std::string::const_iterator begin;
   std::string::const_iterator end;   
};

struct A
{
    std::string header;
    ints_type ints;
};

BOOST_FUSION_ADAPT_STRUCT(
    ints_type,
    (std::string::const_iterator, begin)
    (std::vector<int>, data)
    (std::string::const_iterator, end)
)

BOOST_FUSION_ADAPT_STRUCT(
     A,
     (std::string, header)
     (ints_type, ints)
)

template <typename Iterator>
struct parser : qi::grammar< Iterator, A() >
{
    parser() : parser::base_type(start)
    {
        header %= qi::lexeme[ +qi::alpha ];
        ints %= qi::lexeme[ iter_pos >> qi::int_ % qi::char_(",_") >> iter_pos ]; // <---- capture the original text that matches this into inttext
        start %= header >> ' ' >> ints;
    }

    qi::rule<Iterator, std::string()> header;
    qi::rule<Iterator, ints_type() > ints;
    qi::rule<Iterator, A()> start;
};

int main()
{
    A output;
    std::string input("out 1,2_3");
    auto iter = input.begin();
    parser<decltype(iter)> p;
    bool r = qi::parse(iter, input.end(), p, output);
    if( !r || iter != input.end() )
    {
        std::cout << "did not parse";
    }
    else
    {
        // would like output.inttext to be "1,2_3"
        std::cout << output.header << ": " << std::string(output.ints.begin,output.ints.end) << " -> [ ";
        for( auto & i: output.ints.data )
            std::cout << i << ' ';
        std::cout << ']' << std::endl;
    }
}

使用语义动作：

#include <iostream>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/spirit/repository/include/qi_iter_pos.hpp>

namespace qi = boost::spirit::qi;
namespace phx = boost::phoenix;
using boost::spirit::repository::qi::iter_pos;

struct ints_type
{
   std::vector<int> data;
   std::string inttext; 
};

struct A
{
    std::string header;
    ints_type ints;

};

BOOST_FUSION_ADAPT_STRUCT(
    ints_type,
    (std::vector<int>, data)
    (std::string, inttext)
)

BOOST_FUSION_ADAPT_STRUCT(
     A,
     (std::string, header)
     (ints_type, ints)
)

template <typename Iterator>
struct parser : qi::grammar< Iterator, A() >
{
    parser() : parser::base_type(start)
    {
        header %= qi::lexeme[ +qi::alpha ];
        ints = qi::lexeme[
                  (iter_pos >> qi::int_ % qi::char_(",_") >> iter_pos)
                     [phx::at_c<0>(qi::_val)=qi::_2,
                      phx::at_c<1>(qi::_val)=phx::construct<std::string>(qi::_1,qi::_3)] 
               ]; 
        start %= header >> ' ' >> ints;
    }

    qi::rule<Iterator, std::string()> header;
    qi::rule<Iterator, ints_type() > ints;
    qi::rule<Iterator, A()> start;
};

int main()
{
    A output;
    std::string input("out 1,2_3");
    auto iter = input.begin();
    parser<decltype(iter)> p;
    bool r = qi::parse(iter, input.end(), p, output);
    if( !r || iter != input.end() )
    {
        std::cout << "did not parse";
    }
    else
    {
        // would like output.inttext to be "1,2_3"
        std::cout << output.header << ": " << output.ints.inttext << " -> [ ";
        for( auto & i: output.ints.data )
            std::cout << i << ' ';
        std::cout << ']' << std::endl;
    }
}

标签：c,boost,boost-spirit
来源： https://codeday.me/bug/20190901/1780352.html