anchor.diff:  		list = class
   		public
   			constructor create();
  -			destructor destroy();
  +			destructor destroy(); override;
   			
   			function get_begin(): list_iterator;
   			function get_end(): list_iterator;
  
positive.code: 			index := index - 1;
  		end;
  		at := it.get_data();
  	end;
  
  	function list.empty(): boolean;
  
negative.code: 			nextLink := p.getLink();
  			link^.setNext(nextLink);
  			nextLink^.setPrev(link);
  			m_begin.destroy();
  			m_begin := list_iterator.create(link);
  		end
  		else
  