Question

我尝试解析具有加号或减号字符，后跟X或Y字符，后跟无符号整数的输入。

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

根据我对文档的阅读，其合成属性为tuple<vector<char>,unsigned int>，因为替代解析器(char | char)的类型为char，char >> char("xyXY")将为vector<char>，vector<char> >> uint_将是类型的元组，因此tuple<vector<char>,unsigned int>。这无法编译

qi\detail\assign_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 error\n";
}

然后我尝试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 error\n";
}

这会编译，但输出不正确。输入的第一个标记被正确解析，但后续标记不是：

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 error\n";
}

在解析x / y令牌时改进了这一点，但不是第三个整数令牌：

sign=-, xy=Y, size=0

请告诉我哪里出错了。

我使用的是Spirit版本2.5.2（来自Boost 1.58.0）和Microsoft Visual Studio 2008。

Answer 1

Spirit图书馆文档建议使用Fusion tuple。我想我看到某处（现在找不到）Boost tuple可能与Spirit库不完全兼容。

以下是您的固定示例：

#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 error\n";

    return 0;
}

输出： sign=-, xy=Y, size=512

更新：实际上，我发现here可以使用boost::tuple，但需要包含不同的标头：#include <boost/fusion/include/boost_tuple.hpp>。

提升精神合成属性混乱

1 个答案: