#include <string>
#include <sstream>
#include <iostream>

template <class T>
std::string to_string(T t, std::ios_base & (*f)(std::ios_base&))
{
  std::ostringstream oss;
  oss << f << t;
  return oss.str();
}

int main()
{
  // the second parameter of to_string() should be one of 
  // std::hex, std::dec or std::oct
  std::cout<<to_string<long>(123456, std::hex)<<std::endl;
  std::cout<<to_string<long>(123456, std::oct)<<std::endl;
  return 0;
} 

/* output:
1e240
361100
*/

Convert numeric type to String

C++