Advanced C++ Topics

Overloading Operators

For many classes, you want to print the object with the familiar << notation.

The output operator takes a parameter of type ostream& (because printing modifies the stream) and the object to be printed.

ostream& operator<<(ostream& out, Time a)
{
   out << a.get_hours() << ":";
   if (a.get_minutes() < 10) out << "0";
   out << a.get_minutes() << ":";
   if (a.get_seconds() < 10) out << "0";
   out << a.get_seconds();
   return out;
}

The << operator returns the out stream to enable chaining of the << operator.
```
cout << now << "\n";
```
really means
```
(cout << not) << "\n";
```
that is
```
operator(cout, now) << "\n";
```
The call to operator(cout, now) returns cout, then cout << "\n" prints a new line.

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