id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
12085,(a - b) === (!b >> a) does not hold in X3,mikhail.strelnikov@…,Joel de Guzman,"Following program checks that two grammars (GRAMMAR1 and GRAMMAR2) are giving the same result for x3 and qi. They don't. 

GRAMMAR1 is (!b >> a), GRAMMAR2 is (a - b).

When x3 is used (USE_X3==1) output is:

1 d[[BR]]
1 abcd[[BR]]


When qi is used (USE_X3==0) output is:

1 abcd[[BR]]
1 abcd[[BR]]

{{{
#define USE_X3 1

#if USE_X3 == 1
#include <boost/spirit/home/x3.hpp>
#else
#include <boost/spirit/include/qi.hpp>
#endif

#include <iostream>
#include <string>
#include <vector>

#define GRAMMAR1 !lexeme[keywords >> !(alnum | '_')] >> lexeme[(alpha | '_') >> *(alnum | '_')]
#define GRAMMAR2 lexeme[(alpha | '_') >> *(alnum | '_')] - lexeme[keywords >> !(alnum | '_')]

int main()
{
    std::string str = ""abcd"";

    auto   end  = str.end();
#if USE_X3 == 1
    {
        using namespace boost::spirit::x3;
        symbols<> keywords({""k1"", ""k2"", ""k3""});
        
        {
            std::string v;
            auto begin = str.begin();
            bool full = boost::spirit::x3::parse(begin, end, GRAMMAR1, v) && begin == end;
            std::cout << full << "" "" << v << std::endl;
        }
        
        {
            std::string v;
            auto begin = str.begin();
            bool full = boost::spirit::x3::parse(begin, end, GRAMMAR2, v) && begin == end;
            std::cout << full << "" "" << v << std::endl;
        }
    }
#else
    {
        using namespace boost::spirit::qi;
        symbols<> keywords; keywords = ""k1"", ""k2"", ""k3"";
        
        {
            std::string v;
            auto begin = str.begin();
            bool full = boost::spirit::qi::parse(begin, end, GRAMMAR1, v) && begin == end;
            std::cout << full << "" "" << v << std::endl;
        }
    
        {
            std::string v;
            auto begin = str.begin();
            bool full = boost::spirit::qi::parse(begin, end, GRAMMAR2, v) && begin == end;
            std::cout << full << "" "" << v << std::endl;
        }
    }
#endif
}

}}}
",Bugs,closed,To Be Determined,spirit,Boost 1.61.0,Problem,fixed,,