[queue.defn]

# 23 Containers library [[containers]](./#containers)

## 23.6 Container adaptors [[container.adaptors]](container.adaptors#queue.defn)

### 23.6.3 Class template queue [[queue]](queue#defn)

#### 23.6.3.1 Definition [queue.defn]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L15635)

Any sequence container supporting operationsfront(),back(),push_back() andpop_front() can be used to instantiatequeue[.](#1.sentence-1)

In particular,<list> and<deque> can be used[.](#1.sentence-2)

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:constexpr queue() : queue(Container()) {}constexpr explicit queue(const Container&); constexpr explicit queue(Container&&); template<class InputIterator> constexpr queue(InputIterator first, InputIterator last); template<[*container-compatible-range*](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R> constexpr queue(from_range_t, R&& rg); template<class Alloc> constexpr explicit queue(const Alloc&); template<class Alloc> constexpr queue(const Container&, const Alloc&); template<class Alloc> constexpr queue(Container&&, const Alloc&); template<class Alloc> constexpr queue(const queue&, const Alloc&); template<class Alloc> constexpr queue(queue&&, const Alloc&); template<class InputIterator, class Alloc>constexpr queue(InputIterator first, InputIterator last, const Alloc&); template<[*container-compatible-range*](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R, class Alloc>constexpr queue(from_range_t, R&& rg, const Alloc&); constexpr bool empty() const { return c.empty(); }constexpr size_type size() const { return c.size(); }constexpr reference front() { return c.front(); }constexpr const_reference front() const { return c.front(); }constexpr reference back() { return c.back(); }constexpr const_reference back() const { return c.back(); }constexpr void push(const value_type& x) { c.push_back(x); }constexpr void push(value_type&& x) { c.push_back(std::move(x)); }template<[*container-compatible-range*](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R> constexpr void push_range(R&& rg); template<class... Args>constexpr decltype(auto) emplace(Args&&... args){ return c.emplace_back(std::forward<Args>(args)...); }constexpr void pop() { c.pop_front(); }constexpr 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 InputIterator> queue(InputIterator, InputIterator) -> queue<*iter-value-type*<InputIterator>>; template<ranges::[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R> queue(from_range_t, R&&) -> queue<ranges::range_value_t<R>>; template<class Container, class Allocator> queue(Container, Allocator) -> queue<typename Container::value_type, Container>; template<class InputIterator, class Allocator> queue(InputIterator, InputIterator, Allocator)-> queue<*iter-value-type*<InputIterator>, deque<*iter-value-type*<InputIterator>,
 Allocator>>; template<ranges::[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Allocator> queue(from_range_t, R&&, Allocator)-> queue<ranges::range_value_t<R>, deque<ranges::range_value_t<R>, Allocator>>; template<class T, class Container, class Alloc>struct uses_allocator<queue<T, Container>, Alloc>: uses_allocator<Container, Alloc>::type { };}