procedure tlist.remove_item(p: ptitem);
var r: ptitem;
begin
  r := p^.prev;
  if r <> nil then r^.next := p^.next
  else first := p^.next;

  r := p^.next;
  if r <> nil then r^.prev := p^.prev
  else last := p^.prev;

  dispose(p);
  p := nil
end;