763: Mainline

Here, then, are the revised, fully protected, class definitions:

class link { 
  friend class header; 
  private: 
    link *next_link_pointer; 
    railroad_car *element_pointer; 
    link (railroad_car *e, link *l) { 
      element_pointer = e; 
      next_link_pointer = l; 
    } 
}; 
class header { 
  public: 
    header ( ) { 
      first_link_pointer = NULL; 
      current_link_pointer = first_link_pointer; 
    } 
    void add (railroad_car *new_element) { 
      first_link_pointer = new link (new_element, first_link_pointer); 
      current_link_pointer = first_link_pointer; 
    } 
    void advance ( ) { 
      current_link_pointer = current_link_pointer -> next_link_pointer; 
    } 
    railroad_car* access ( ) { 
      return current_link_pointer -> element_pointer; 
    } 
    int endp ( ) { 
      return ! current_link_pointer; 
    } 
    void reset ( ) { 
      current_link_pointer = first_link_pointer; 
    } 
  private: 
    link *first_link_pointer; 
    link *current_link_pointer; 
};