|
|
|
|
|
|
|
The answer is that you use the volume function without an
explicit class argument, as in the following definition of
display_capacity:
virtual void display_capacity ( ) {cout << volume ( );}
By convention, because the class object argument and the class-member
operator are absent, the volume function is handed the same class-object
argument that was handed to display_capacity. Thus, volume
has an implicit argument.