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

/** Custom policy for floating point number generators */ 
template<typename T> 
struct real_policy : boost::spirit::karma::real_policies<T> 
{ 
    static int floatfield(T) 
    { 
        return boost::spirit::karma::real_policies<T>::fmtflags::fixed; 
    } 

    static unsigned int precision(T) 
    { 
        return std::numeric_limits<T>::digits10 + 1; 
    } 

}; 

void write_double(std::back_insert_iterator<std::string> &sink, double &value)
{
    boost::spirit::karma::real_generator<double, real_policy<double> > generator; 
    boost::spirit::karma::generate(sink, generator, value); 
}

int main()
{
    std::string s;
    s.reserve(100);
    std::back_insert_iterator<std::string> sink(s);

    double value = 0.09999999999999987;
    write_double(sink, value); 
    std::cout << s << " != " << value << std::endl;
    return 0;
}