86     LinkedListEntry<T>* head;  member
109     return header_ == nullptr || header_->head == nullptr;  in empty()
115     new_entry->next = header_->head;  in push_front()
117     header_->head = new_entry;  in push_front()
129       header_->tail = header_->head = new_entry;  in push_back()
139     LinkedListEntry<T>* entry = header_->head;  in pop_front()
141     header_->head = entry->next;  in pop_front()
144     if (header_->head == nullptr) {  in pop_front()
152     return empty() ? nullptr : header_->head->element;  in front()
158     while (header_->head != nullptr) {  in clear()
159       LinkedListEntry<T>* p = header_->head;  in clear()
160       header_->head = header_->head->next;  in clear()
177     for (LinkedListEntry<T>* e = head(); e != nullptr; e = e->next) {  in visit()
188     for (LinkedListEntry<T>* e = header_->head, *p = nullptr; e != nullptr;) {  in remove_if()
192           header_->head = next;  in remove_if()
219     for (LinkedListEntry<T>* e = head(); e != nullptr; e = e->next) {  in find_if()
229     return iterator(head());  in begin()
237     for (LinkedListEntry<T>* e = head(); e != nullptr; e = e->next) {  in find()
248     for (LinkedListEntry<T>* e = head(); sz < array_length && e != nullptr; e = e->next) {  in copy_to_array()
256     for (LinkedListEntry<T>* e = head(); e != nullptr; e = e->next) {  in contains()
280       header_->head = header_->tail = nullptr;  in alloc_header()
284   LinkedListEntry<T>* head() const {  in head()  function
285     return header_ != nullptr ? header_->head : nullptr;  in head()