C++ Primer Plus

Overloading the << Operator

To redefine the << operator so that you use it with cout to display an object’s contents, you define a friend operator function that has the following form:

ostream & operator<<(ostream & os, const c_name & obj){    os << ... ;  // display object contents    return os;}

Here c_name represents the name of the class. If the class provides public methods that return the required contents, you can use those methods in the operator function and dispense with the friend status.