45     constexpr circular_doubly_linked_list_with_sentinel() : count(0), head(&head, &head) {}  in circular_doubly_linked_list_with_sentinel()
52     inline base_node* front() const { return head.next; }  in front()
53     inline base_node* last() const { return head.prev; }  in last()
54     inline const base_node* end() const { return &head; }  in end()
59         n->prev = head.prev;  in add()
60         n->next = &head;  in add()
61         head.prev->next = n;  in add()
62         head.prev = n;  in add()
78             lst.head.next = head.next;  in flush_to()
79             lst.head.prev = head.prev;  in flush_to()
80             head.next->prev = &lst.head;  in flush_to()
81             head.prev->next = &lst.head;  in flush_to()
87         head.next = &head;  in clear()
88         head.prev = &head;  in clear()
93     base_node head;  variable