增强精神合成属性混乱

Boost Spirit synthesised attribute confusion

本文关键字：属性 混乱 增强      更新时间：2023-10-16

我正在尝试解析输入，其中有一个加号或减号字符，后跟一个X或Y字符，后跟一个无符号整数。

(char_('+') | char_('-')) >> char_("xyXY") >> uint_

根据我对文档的阅读，这将是tuple<vector<char>,unsigned int>的综合属性，因为替代解析器(char | char)将是char类型，char >> char("xyXY")将是vector<char>, vector<char> >> uint_将是类型的元组，因此tuple<vector<char>,unsigned int>。编译

失败
qidetailassign_to.hpp(152) : error C2440: 'static_cast' : cannot convert from 'const char' to 'boost::tuples::tuple<T0,T1>'
代码:

#include <iostream>
#include <string>
#include <vector>
#include <boost/fusion/include/tuple.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/tuple/tuple.hpp>
using namespace boost::spirit::qi;
int main()
{
    std::string input("-Y 512");
    typedef std::string::const_iterator Iterator;
    Iterator first = input.begin();
    Iterator last = input.end();
    boost::tuple<std::vector<char>,unsigned int> output;
    bool result = phrase_parse(first,last,(char_('+') | char_('-')) >> char_("xyXY") >> uint_,ascii::space,output);
    if(result && first == last)
        std::cout << "sign=" << boost::get<0>(output)[0] << ", xy=" << boost::get<0>(output)[1] << ", size=" << boost::get<1>(output) << 'n';
    else
        std::cerr << "Parse errorn";
}

然后我尝试将tuple<char,char,unsigned int>作为属性类型:

#include <iostream>
#include <string>
#include <vector>
#include <boost/fusion/include/tuple.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/tuple/tuple.hpp>
using namespace boost::spirit::qi;
int main()
{
    std::string input("-Y 512");
    typedef std::string::const_iterator Iterator;
    Iterator first = input.begin();
    Iterator last = input.end();
    boost::tuple<char,char,unsigned int> output;
    bool result = phrase_parse(first,last,(char_('+') | char_('-')) >> char_("xyXY") >> uint_,ascii::space,output);
    if(result && first == last)
        std::cout << "sign=" << boost::get<0>(output) << ", xy=" << boost::get<1>(output) << ", size=" << boost::get<2>(output) << 'n';
    else
        std::cerr << "Parse errorn";
}

可以编译，但输出不正确。输入的第一个标记被正确解析，但随后的标记没有被解析:

sign=-, xy= , size=0

我也试过as_string[]:

#include <iostream>
#include <string>
#include <vector>
#include <boost/fusion/include/tuple.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/tuple/tuple.hpp>
using namespace boost::spirit::qi;
int main()
{
    std::string input("-Y 512");
    typedef std::string::const_iterator Iterator;
    Iterator first = input.begin();
    Iterator last = input.end();
    boost::tuple<std::string,unsigned int> output;
    bool result = phrase_parse(first,last,as_string[(char_('+') | char_('-')) >> char_("xyXY")] >> uint_,ascii::space,output);
    if(result && first == last)
        std::cout << "sign=" << boost::get<0>(output)[0] << ", xy=" << boost::get<0>(output)[1] << ", size=" << boost::get<1>(output) << 'n';
    else
        std::cerr << "Parse errorn";
}

当x/y标记被解析时，这改进了事情，但不是第三个整数标记:

sign=-, xy=Y, size=0

请告诉我哪里错了。

我使用的是Spirit 2.5.2版本(从Boost 1.58.0开始)和Microsoft Visual Studio 2008.

Spirit库文档推荐使用Fusion tuple。我想我在某个地方看到(现在找不到)Boost tuple可能不完全兼容Spirit库。

这是你的固定示例:

#include <iostream>
#include <string>
#include <vector>
#include <boost/fusion/include/tuple.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/fusion/sequence.hpp>
namespace qi = boost::spirit::qi;
int main()
{
    std::string input("-Y 512");
    typedef std::string::const_iterator Iterator;
    Iterator first = input.begin();
    Iterator last = input.end();
    boost::fusion::tuple<char, char, unsigned int> output;
    bool result = qi::phrase_parse(first, last, (qi::char_('+') | qi::char_('-')) >> qi::char_("xyXY") >> qi::uint_, qi::ascii::space, output);
    if (result && first == last)
        std::cout << "sign=" << boost::fusion::get<0>(output) << ", xy=" << boost::fusion::get<1>(output) << ", size=" << boost::fusion::get<2>(output) << 'n';
    else
        std::cerr << "Parse errorn";
    return 0;
}

输出:sign=-, xy=Y, size=512

更新:实际上我发现这里可以使用boost::tuple，但需要包括不同的头:#include <boost/fusion/include/boost_tuple.hpp> .

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