/* List properties. */
size_t list_size(const struct list *);
bool list_is_empty(const struct list *);
+bool list_is_singleton(const struct list *);
+bool list_is_short(const struct list *);
#define LIST_FOR_EACH(ITER, MEMBER, LIST) \
for (ASSIGN_CONTAINER(ITER, (LIST)->next, MEMBER); \