#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/karma.hpp>
#include <boost/spirit/include/karma_real.hpp>

#include <iostream>
#include <string>
#include <iterator>

namespace karma = boost::spirit::karma;

// define a new real number formatting policy
template <typename Num>
struct scientific_policy : karma::real_policies<Num>
{
  // we want the numbers always to be in scientific format
  static int floatfield(Num n) { return std::ios_base::scientific; }
};

int main( ) {
  // define a new generator type based on the new policy
  typedef 
    karma::real_generator<double, scientific_policy<double> > science_type;
  science_type const scientific = science_type();
  
  std::string output;
  typedef std::back_insert_iterator<std::string> output_iterator;
  output_iterator sink( output );
  
  // should output: 1.0e-01, but will output: 10.0e-02
  karma::generate(sink, scientific, 0.1);      
  
  std::cout  << output << std::endl;
};