if (filter ->next ) filter ->next->pre = filter ->pre; else list->tail = filter ->pre; if (filter ->pre) filter->pre->next = filter ->next; else list ->head = flter ->next; free (filter);
if (filter ->next ) filter ->next->pre = filter ->pre; else list->tail = filter ->pre; if (filter ->pre) filter->pre->next = filter ->next; else list ->head = flter ->next; free (filter);