[deque.overview]

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

## 23.3 Sequence containers [[sequences]](sequences#deque.overview)

### 23.3.5 Class template deque [[deque]](deque#overview)

#### 23.3.5.1 Overview [deque.overview]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6466)

Adeque is a sequence container that supports [random access iterators](random.access.iterators "24.3.5.7 Random access iterators [random.access.iterators]")[.](#1.sentence-1)

In addition, it supports constant time insert and erase operations at the beginning or the end;
insert and erase in the middle take linear time[.](#1.sentence-2)

That is, a deque is especially optimized for pushing and popping elements at the beginning and end[.](#1.sentence-3)

Storage management is handled automatically[.](#1.sentence-4)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6476)

A deque meets all of the requirements
of a container ([[container.reqmts]](container.reqmts "23.2.2.2 Container requirements")),
of a reversible container ([[container.rev.reqmts]](container.rev.reqmts "23.2.2.3 Reversible container requirements")),
of an allocator-aware container ([[container.alloc.reqmts]](container.alloc.reqmts "23.2.2.5 Allocator-aware containers")), and
of a sequence container,
including the optional sequence container requirements ([[sequence.reqmts]](sequence.reqmts "23.2.4 Sequence containers"))[.](#2.sentence-1)

Descriptions are provided here only for operations ondeque that are not described in one of these tables
or for operations where there is additional semantic information[.](#2.sentence-2)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/containers.tex#L6488)

The types iterator and const_iterator meet
the constexpr iterator requirements ([[iterator.requirements.general]](iterator.requirements.general "24.3.1 General"))[.](#3.sentence-1)

namespace std {template<class T, class Allocator = allocator<T>>class deque {public:// typesusing value_type = T; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = *implementation-defined*; // see [[container.requirements]](container.requirements "23.2 Requirements")using difference_type = *implementation-defined*; // see [[container.requirements]](container.requirements "23.2 Requirements")using iterator = *implementation-defined*; // see [[container.requirements]](container.requirements "23.2 Requirements")using const_iterator = *implementation-defined*; // see [[container.requirements]](container.requirements "23.2 Requirements")using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; // [[deque.cons]](deque.cons "23.3.5.2 Constructors, copy, and assignment"), construct/copy/destroyconstexpr deque() : deque(Allocator()) { }constexpr explicit deque(const Allocator&); constexpr explicit deque(size_type n, const Allocator& = Allocator()); constexpr deque(size_type n, const T& value, const Allocator& = Allocator()); template<class InputIterator>constexpr deque(InputIterator first, InputIterator last, const Allocator& = Allocator()); template<[*container-compatible-range*](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R>constexpr deque(from_range_t, R&& rg, const Allocator& = Allocator()); constexpr deque(const deque& x); constexpr deque(deque&&); constexpr deque(const deque&, const type_identity_t<Allocator>&); constexpr deque(deque&&, const type_identity_t<Allocator>&); constexpr deque(initializer_list<T>, const Allocator& = Allocator()); constexpr ~deque(); constexpr deque& operator=(const deque& x); constexpr deque& operator=(deque&& x)noexcept(allocator_traits<Allocator>::is_always_equal::value); constexpr deque& operator=(initializer_list<T>); template<class InputIterator>constexpr void assign(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 void assign_range(R&& rg); constexpr void assign(size_type n, const T& t); constexpr void assign(initializer_list<T>); constexpr allocator_type get_allocator() const noexcept; // iteratorsconstexpr iterator begin() noexcept; constexpr const_iterator begin() const noexcept; constexpr iterator end() noexcept; constexpr const_iterator end() const noexcept; constexpr reverse_iterator rbegin() noexcept; constexpr const_reverse_iterator rbegin() const noexcept; constexpr reverse_iterator rend() noexcept; constexpr const_reverse_iterator rend() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cend() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept; constexpr const_reverse_iterator crend() const noexcept; // [[deque.capacity]](deque.capacity "23.3.5.3 Capacity"), capacityconstexpr bool empty() const noexcept; constexpr size_type size() const noexcept; constexpr size_type max_size() const noexcept; constexpr void resize(size_type sz); constexpr void resize(size_type sz, const T& c); constexpr void shrink_to_fit(); // element accessconstexpr reference operator[](size_type n); constexpr const_reference operator[](size_type n) const; constexpr reference at(size_type n); constexpr const_reference at(size_type n) const; constexpr reference front(); constexpr const_reference front() const; constexpr reference back(); constexpr const_reference back() const; // [[deque.modifiers]](deque.modifiers "23.3.5.4 Modifiers"), modifierstemplate<class... Args> constexpr reference emplace_front(Args&&... args); template<class... Args> constexpr reference emplace_back(Args&&... args); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); constexpr void push_front(const T& x); constexpr void push_front(T&& x); template<[*container-compatible-range*](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R>constexpr void prepend_range(R&& rg); constexpr void push_back(const T& x); constexpr void push_back(T&& x); template<[*container-compatible-range*](container.intro.reqmts#concept:container-compatible-range "23.2.2.1 Introduction [container.intro.reqmts]")<T> R>constexpr void append_range(R&& rg); constexpr iterator insert(const_iterator position, const T& x); constexpr iterator insert(const_iterator position, T&& x); constexpr iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator>constexpr iterator insert(const_iterator position,
 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 iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<T>); constexpr void pop_front(); constexpr void pop_back(); constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void swap(deque&)noexcept(allocator_traits<Allocator>::is_always_equal::value); constexpr void clear() noexcept; }; template<class InputIterator, class Allocator = allocator<*iter-value-type*<InputIterator>>> deque(InputIterator, InputIterator, Allocator = Allocator())-> 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 = allocator<ranges::range_value_t<R>>> deque(from_range_t, R&&, Allocator = Allocator())-> deque<ranges::range_value_t<R>, Allocator>;}