The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
#include <functional> // for std::cref()
#include <string>
#include <iostream>
void printString(std::string const& s)
{
std::cout << s << '\n';
}
template<typename T>
void printT (T arg)
{
printString(arg); // might convert arg back to std::string
}
int main()
{
std::string s = "hello";
printT(s); // print s passed by value
printT(std::cref(s)); // print s passed ``as if by reference''
}