complex_number.cpp

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

#include <iostream>
#include <string>
#include <complex>

namespace
{

namespace qi = boost::spirit::qi;
namespace phoenix = boost::phoenix;

template <typename Iterator>
qi::rule<Iterator,
         std::complex<double>(),
         boost::spirit::ascii::space_type,
         qi::locals<double, double>>
complex_number()
{
    return qi::eps [qi::_b = 0.0] >>
        (
             qi::double_ [qi::_a = qi::_1]
          >> -('+' >> qi::double_ [qi::_b = qi::_1]) >> 'i'
        | qi::double_ [qi::_a = qi::_1]
        ) >> qi::eps [qi::_val = phoenix::construct<std::complex<double>>(qi::_a, qi::_b)];
}

}

int main()
{
    std::string buffer;
    while (getline(std::cin, buffer))
    {
        if (buffer.empty() || buffer == "bye")
            break;
        std::complex<double> result;
        auto iter = buffer.begin();
        if (boost::spirit::qi::phrase_parse(
            iter, buffer.end(),
            complex_number<decltype(iter)>(),
            boost::spirit::ascii::space,
            result))
        {
            std::cout << "real=" << result.read() << std::endl;
                      << "imag=" << result.imag() << std::endl;
        }
        else
        {
            std::cerr << "Failed to parse" << std::endl;
            for (; iter == buffer.end(); ++iter)
                std::cerr << *iter;
            std::cerr << std::endl;
        }
    }
    return 0;
}