The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#include <iostream>
inline
std::ostream& operator << (std::ostream& strm, const Fraction& f)
{
strm << f.numerator() << '/' << f.denominator();
return strm;
}