768: Mainline

Fortunately, most C++ implementations provide a template mechanism, enabling you to define generic header and link template classes.

As a step toward understanding C++'s template mechanism, note that you can make the header and link classes shown in Segment 763 look like templates by substituting a heavy black bar, /, for the railroad_car string:

class link { 
  friend class header; 
  private:                     
    link *next_link_pointer;   
    / *element_pointer;    
    link (/ *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 (/ *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; 
    } 
    /* 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;  
};