boost_karma3.cpp

#include <iostream>
#include <string>

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

int main()
{
    using namespace boost::spirit::karma;
    
    std::complex<double> c(3, -1);
    std::string result;
    
    generate(
             std::back_inserter(result),      // the output
             !double_(0.0) << '(' << double_ << ',' << double_ << ')' //
             |                                                        // the generator
             omit[double_] << double_,                                //
             c.imag(), c.real(), c.imag()     // the input
             );
    
    std::cout << result << "\n\n";
}