619: Mainline

The right place to create the new character buffer—and assign it to the serial_number pointer—is inside a one-argument constructor. The following engine class definition exhibits such a constructor:

class engine { 
  public: engine ( ) { } 
          // New constructor: 
          engine (char *input_buffer) { 
            // Create new array just long enough: 
            serial_number = new char[strlen(input_buffer) + 1]; 
            ... 
          } 
          virtual char* short_name ( ) {return "eng";} 
}; 

Thus, the new engine constructor arranges for the serial_number member variable, declared in the railroad_car class, to point to the first character in a new character array.