ostringstream gives me Implicit instantiation error

Question

I'm trying the elegant solution provided in this answer but no matter what I try, I cannot get passed the error Implicit instantiation of undefined template for this line:

std::ostringstream strs;

What I need to do? I've included the following, which I'm sure is overkill. As a second question it seems hard to track down what exactly needs to be included for ostringstream:

#include <iostream>
#include <fstream>
#include <iosfwd>
#include <ios>

Answer 1

stringstream classes are defined in sstream header, so write

#include <sstream>

and all will be fine.