491: Mainline

In Chapter 15, you learned about box and box_car classes defined such that the box class contains the height, width, and length member variables that are initialized by the default constructor contained in the box_car class:

class box : public container { 
  public: double height, width, length; 
          // Default constructor: 
          box ( ) { } 
          // Other member function: 
          double volume ( ) {return height * width * length;} 
}; 
... 
class box_car : public railroad_car, public box { 
  public: // Default constructor: 
          box_car ( ) { 
            height = 10.5; width = 9.2; length = 40.0;} 
}; 

The box class, however, can have its own constructor for initializing its own member variables:

class box : public container {
  public: double height, width, length;
          // Default constructor:
          box ( ) { }
          // Argument-bearing constructor:      
          box (double h, double w, double l) {  
            height = h; width = w; length = l;  
          }                                     
          // Other member function: 
          double volume ( ) {return height * width * length;} 
}; 

Given such an argument-bearing constructor in the box class, naturally you would like to have a way to make use of it in the definition of the default constructor defined in the box_car class.