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One step that is easy to take is to convert the display_capacity
function, which displays but returns nothing, into capacity, a
function that displays nothing but returns a capacity. Recall that
display_capacity is defined as follows in the railroad_car
class definition:
virtual void display_capacity ( ) { }
Further recall that display_capacity is defined as follows in the
box_car and tank_car class definitions:
virtual void display_capacity ( ) {cout << volume ( );}
Using those definitions as a model, you might define
capacity in the railroad_car class
definition as follows:
virtual double capacity ( ) {return 0.0;}
And you might define capacity this way in the
box_car and tank_car class definitions:
virtual double capacity ( ) {return volume ( );}