534: Mainline

Having rid yourself of display_capacity, you might like to take the next natural step: to rid yourself of display_short_name as well. Then, you could construct a for loop in which all the displaying is done explicitly:

for (n = 0; n < car_count; ++n) { 
  // Display short name and capacity and terminate the line:  
  cout << train[n] -> short_name ( ) 
       << "     " 
       << train[n] -> capacity ( ) 
       << endl; 
} 

To define short_name, using display_short_name as a model, you need to know what the return type should be:

// Definition in railroad_car 
virtual what type here? short_name ( ) {return "rrc";} 
// Definition in box_car 
virtual what type here? short_name ( ) {return "box";} 
...