Compilation error with a boost::spirit parser

Question

I have a strange problem with a calculator made using boost::spirit. This calculator is supposed to take a string as argument representing a series of arithmetical expressio

Answer 1

I'm pretty sure you might have been rearranging stuff in your rules. In fact, the %= auto-rule expression assignments won't work because the synthesized type of the parser expression doesn't resemble an int.

Basically, you'd change

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;

into

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 ];

I have fixed up some small issues and created a SSCCE of your post that works, as far as I can tell 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;
}

Output:

output: 13, 42

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¹ gcc 4.6.1, boost 1_48