entity next = it.(il_next);
entity prev = it.(il_prev);
entity ohead = this.il_head;
entity otail = this.il_tail;
next ? next.(il_prev) = prev : this.il_tail = prev;
prev ? prev.(il_next) = next : this.il_head = next;
entity next = it.(il_next);
entity prev = it.(il_prev);
entity ohead = this.il_head;
entity otail = this.il_tail;
next ? next.(il_prev) = prev : this.il_tail = prev;
prev ? prev.(il_next) = next : this.il_head = next;