22 Containers library [containers]

22.6 Container adaptors [container.adaptors]

22.6.4 Class template queue [queue]

22.6.4.1 Definition [queue.defn]

Any sequence container supporting operations front(), back(), push_­back() and pop_­front() can be used to instantiate queue.
In particular, list and deque can be used.
namespace std { template<class T, class Container = deque<T>> class queue { public: using value_type = typename Container::value_type; using reference = typename Container::reference; using const_reference = typename Container::const_reference; using size_type = typename Container::size_type; using container_type = Container; protected: Container c; public: queue() : queue(Container()) {} explicit queue(const Container&); explicit queue(Container&&); template<class Alloc> explicit queue(const Alloc&); template<class Alloc> queue(const Container&, const Alloc&); template<class Alloc> queue(Container&&, const Alloc&); template<class Alloc> queue(const queue&, const Alloc&); template<class Alloc> queue(queue&&, const Alloc&); [[nodiscard]] bool empty() const { return c.empty(); } size_type size() const { return c.size(); } reference front() { return c.front(); } const_reference front() const { return c.front(); } reference back() { return c.back(); } const_reference back() const { return c.back(); } void push(const value_type& x) { c.push_back(x); } void push(value_type&& x) { c.push_back(std::move(x)); } template<class... Args> decltype(auto) emplace(Args&&... args) { return c.emplace_back(std::forward<Args>(args)...); } void pop() { c.pop_front(); } void swap(queue& q) noexcept(is_nothrow_swappable_v<Container>) { using std::swap; swap(c, q.c); } }; template<class Container> queue(Container) -> queue<typename Container::value_type, Container>; template<class Container, class Allocator> queue(Container, Allocator) -> queue<typename Container::value_type, Container>; template<class T, class Container, class Alloc> struct uses_allocator<queue<T, Container>, Alloc> : uses_allocator<Container, Alloc>::type { }; }