anchor.diff:  		m_link := l;
   	end;
   
  +	destructor iterator.destroy();
  +	begin
  +		m_link := nil;
  +	end;
  +	
   	procedure iterator.next();
   	begin
   		m_link := m_link.m_next;
  
positive.code: 		iterator = class
  		public
  			constructor create(l: link);
  			
  			procedure next();
  			procedure prev();
  			
  
negative.code: 		m_prev := nil;
  	end;
  
  	destructor link.destroy();
  	begin
  		m_next := nil;
  		m_prev := nil;
  	end;
  	
  	procedure link.set_next(pLink: link);
  	begin
  		m_next := pLink;
  	end;
  
  	procedure link.set_prev(pLink: link);
  	begin
  		m_prev := pLink;
  	end;
  
  	constructor iterator.create(l: link);
  