std::string and format string

Question

I found the below code through Google. It almost does what I want it to do, except it doesn't provide a way to indicate the precision like '%.*f' does in C-type format strings. Also, it doesn't provide anything further than 5 decimal places. Am I going to have to stick with C strings and snprintf?

#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()
{
  std::cout<<to_string<double>(3.1415926535897931, std::dec)<<std::endl;
  return 0;
} 

Answer 1

You want to use the std::setprecision manipulator:

int main()
{
    std::cout << std::setprecision(9) << to_string<long>(3.1415926535897931, std::dec)
              << '\n';
    return 0;
}