#include <iostream>

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

namespace karma = boost::spirit::karma;

template <typename T>
struct my_policy : karma::real_policies<T>
{
    static unsigned int precision(T){return 3;}
    static int floatfield(T){return std::ios_base::scientific;}
};

int main()
{
    karma::real_generator<float, my_policy<float> > my_real;
    
    // Expected output is "1.0e01 1.0e-02 1.0e04" or "1.0e+01 1.0e-02 1.0e+04",
    // but result is "10.0e00 10.0e-03 10.0e03"
    std::cout << karma::format(my_real << " " << my_real << " " << my_real, 9.9999, 9.9996e-3, 9.99951e+3) << std::endl;
}