c++ - boost::spirit 解析器出现编译错误

Question

我在使用 boost::spirit 制作的计算器时遇到了一个奇怪的问题。该计算器应该采用一个字符串作为参数，表示一系列用逗号分隔的算术表达式，例如“a+4*5,77,(b-c)*4”。它还允许字符串“？”并在本例中返回包含 -1 的数组。计算器使用 SymTable 进行初始化，SymTable 是一个模板类参数，用于描述任何提供 [string] -> int 运算符(例如:映射)的类，以解析变量的值。

以下代码适用于我的 Ubuntu 10.4，其中包含 gcc 4.6.2 和 gcc 4.4，以及 boost 1.47 和 1.48。过去它也可以在带有 gcc 4.5.3 和 boost 1.47 的 Cray Linux 机器上运行。

#include <boost/bind.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>

namespace sp = boost::spirit;
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;

namespace Damaris {

template <typename Iterator, typename SymTable>
struct Calc : qi::grammar<Iterator, std::vector<int>(), ascii::space_type>
{
        qi::rule<Iterator, std::vector<int>(), ascii::space_type> start;
        qi::rule<Iterator, int(), ascii::space_type> expr;
        qi::rule<Iterator, int(), ascii::space_type> qmark;
        qi::rule<Iterator, int(), ascii::space_type> factor;
        qi::rule<Iterator, int(), ascii::space_type> simple;
        qi::rule<Iterator, std::string(), ascii::space_type> identifier;
        qi::rule<Iterator, int(SymTable), ascii::space_type> value;

        /**
         * \brief Constructor.
         * \param[in] sym : table of symboles.
         */
        Calc(SymTable &sym) : Calc::base_type(start)
        {
                identifier = qi::lexeme[( qi::alpha | '_') >> *( qi::alnum | '_')];

                value   = identifier[qi::_val = qi::labels::_r1[qi::_1]];

                simple  = ('(' >> expr >> ')')
                        | qi::int_
                        | value(boost::phoenix::ref(sym));

                factor  %= (simple >> '*' >> factor)[qi::_val = qi::_1 * qi::_2]
                        |  (simple >> '/' >> factor)[qi::_val = qi::_1 / qi::_2]
                        |  (simple >> '%' >> factor)[qi::_val = qi::_1 % qi::_2]
                        |   simple;

                expr    %= (factor >> '+' >> expr)[qi::_val = qi::_1 + qi::_2]
                        |  (factor >> '-' >> expr)[qi::_val = qi::_1 - qi::_2]
                        |   factor;

                qmark   = qi::char_('?')[qi::_val = -1];

                start   = qmark
                        | (expr % ',');
        }
};

}

今天我再次尝试在 Cray 机器上编译相同的代码(我认为从那时起它已经升级了)，我尝试使用 gcc 4.6.2 和 gcc 4.5.2，并且都使用 boost 1.48 和 1.49，并且我总是得到我不明白的相同编译错误:

/nics/b/home/mdorier/damaris-0.4/common/Calc.hpp:74:3:   instantiated from 'Damaris::Calc<Iterator, SymTable>::Calc(SymTable&) [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >, SymTable = Damaris::ParameterSet]'
/nics/b/home/mdorier/damaris-0.4/common/MetadataManager.cpp:45:79:   instantiated from here
/nics/b/home/mdorier/deploy/include/boost/spirit/home/qi/detail/assign_to.hpp:123:13: error: invalid static_cast from type 'const boost::fusion::vector2<int, int>' to type 'int'

Calc.hpp 中的第 74 行对应于“factor = ...”行。 指示的实例化行 (MetadataManager.cpp:45) 如下:

layoutInterp = new Calc<std::string::const_iterator,ParameterSet>(*parameters);

layoutInterp 为 Calc* 类型，参数为 ParameterSet* 类型。

知道这个错误从何而来吗？谢谢

Answer 1

我很确定您可能已经重新安排了规则中的内容。事实上，%= 自动规则表达式赋值 不起作用，因为解析器表达式的合成类型与 int 不同.

基本上，你会改变

factor %= (simple >> '*' >> factor)[ _val = _1 * _2 ]
    |  (simple >> '/' >> factor)[ _val = _1 / _2 ]
    |  (simple >> '%' >> factor)[ _val = _1 % _2 ]
    |   simple;

expr   %= (factor >> '+' >> expr)[ _val = _1 + _2 ]
    |  (factor >> '-' >> expr)[ _val = _1 - _2 ]
    |   factor;

进入

factor  = (simple >> '*' >> factor)[ _val = _1 * _2 ]
        | (simple >> '/' >> factor)[ _val = _1 / _2 ]
        | (simple >> '%' >> factor)[ _val = _1 % _2 ]
        | (simple) [_val = _1 ];

expr    = (factor >> '+' >> expr)[ _val = _1 + _2 ]
        | (factor >> '-' >> expr)[ _val = _1 - _2 ]
        | (factor) [_val = _1 ];

据我所知，我已经解决了一些小问题，并为您的帖子创建了一个有效的 SSCCE ¹:

#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/karma.hpp>
#include <boost/spirit/include/phoenix.hpp>

namespace sp = boost::spirit;
namespace qi    = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace karma = boost::spirit::karma;
namespace phx   = boost::phoenix;

namespace Damaris {

    template <typename Iterator, typename SymTable>
    struct Calc : qi::grammar<Iterator, std::vector<int>(), ascii::space_type>
    {
        qi::rule<Iterator, std::vector<int>(), ascii::space_type> start;
        qi::rule<Iterator, int(), ascii::space_type> expr;
        qi::rule<Iterator, int(), ascii::space_type> qmark;
        qi::rule<Iterator, int(), ascii::space_type> factor;
        qi::rule<Iterator, int(), ascii::space_type> simple;
        qi::rule<Iterator, std::string(), ascii::space_type> identifier;
        qi::rule<Iterator, int(SymTable), ascii::space_type> value;

        Calc(SymTable &sym) : Calc::base_type(start)
        {
            using namespace qi;

            identifier = lexeme[( alpha | '_') >> *( alnum | '_')];

            value   = identifier[ _val = _r1[_1] ];

            simple  = ('(' >> expr >> ')')
                    | int_
                    | value(boost::phoenix::ref(sym));

            factor  = (simple >> '*' >> factor)[ _val = _1 * _2 ]
                    | (simple >> '/' >> factor)[ _val = _1 / _2 ]
                    | (simple >> '%' >> factor)[ _val = _1 % _2 ]
                    | (simple) [_val = _1 ];

            expr    = (factor >> '+' >> expr)[ _val = _1 + _2 ]
                    | (factor >> '-' >> expr)[ _val = _1 - _2 ]
                    | (factor) [_val = _1 ];

            qmark   = char_('?')[ _val = -1 ];

            start   = qmark 
                | (expr % ',');

            BOOST_SPIRIT_DEBUG_NODE(start);
            BOOST_SPIRIT_DEBUG_NODE(qmark);
            BOOST_SPIRIT_DEBUG_NODE(expr);
            BOOST_SPIRIT_DEBUG_NODE(factor);
            BOOST_SPIRIT_DEBUG_NODE(simple);
            BOOST_SPIRIT_DEBUG_NODE(value);
            BOOST_SPIRIT_DEBUG_NODE(identifier);
        }
    };

}

int main(int argc, const char *argv[])
{
    typedef std::map<std::string, int> SymTable;
    SymTable symbols;
    Damaris::Calc<std::string::const_iterator, SymTable> calc(symbols);

    symbols["TheAnswerToLifeUniverse"] = 100;
    symbols["Everything"] = -58;

    std::string input = "3*4+5/4, TheAnswerToLifeUniverse + Everything";
    std::string::const_iterator f(input.begin()), l(input.end());
    std::vector<int> data;

    if (qi::phrase_parse(f,l,calc,ascii::space,data))
        std::cout << "output: " << karma::format(karma::int_ % ", " << karma::eol, data);
    else
        std::cout << "problem: '" << std::string(f,l) << "'\n";

    return 0;
}

输出:

output: 13, 42

---

¹ gcc 4.6.1，增强 1_48