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>
#include <sstream>
template <typename charT, typename traits>
inline
std::basic_ostream<charT,traits>&
operator << (std::basic_ostream<charT,traits>& strm,
const Fraction& f)
{
// string stream
// - with same format
// - without special field width
std::basic_ostringstream<charT,traits> s;
s.copyfmt(strm);
s.width(0);
// fill string stream
s << f.numerator() << '/' << f.denominator();
// print string stream
strm << s.str();
return strm;
}