Standard library header <deque>

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C++
 
Standard library headers
 

This header is part of the containers library.

Includes

(C++20)
 Three-way comparison operator support
(C++11)
 std::initializer_list class template

Classes

 double-ended queue
(class template)

Functions

(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20)
 lexicographically compares the values of two deques
(function template)
specializes the std::swap algorithm
(function template)
(C++20)
 erases all elements satisfying specific criteria
(function template)
Range access
(C++11)(C++14)
 returns an iterator to the beginning of a container or array
(function template)
(C++11)(C++14)
 returns an iterator to the end of a container or array
(function template)
(C++14)
 returns a reverse iterator to the beginning of a container or array
(function template)
(C++14)
 returns a reverse end iterator for a container or array
(function template)
(C++17)(C++20)
 returns the size of a container or array
(function template)
(C++17)
 checks whether the container is empty
(function template)
(C++17)
 obtains the pointer to the underlying array
(function template)

Synopsis

#include <compare>
#include <initializer_list>
 
namespace std {
  // class template deque
  template<class T, class Allocator = allocator<T>>
  class deque;
 
  template<class T, class Allocator>
  bool operator==(const deque<T, Allocator>& x, const deque<T, Allocator>& y);
  template<class T, class Allocator>
  /*synth-three-way-result*/<T> operator<=>(const deque<T, Allocator>& x,
                                            const deque<T, Allocator>& y);
 
  template<class T, class Allocator>
  void swap(deque<T, Allocator>& x, deque<T, Allocator>& y) noexcept(noexcept(x.swap(y)));
 
  // erasure
  template<class T, class Allocator, class U = T>
  typename deque<T, Allocator>::size_type erase(deque<T, Allocator>& c, const U& value);
  template<class T, class Allocator, class Predicate>
  typename deque<T, Allocator>::size_type erase_if(deque<T, Allocator>& c,
                                                   Predicate pred);
 
  namespace pmr {
    template<class T>
    using deque = std::deque<T, polymorphic_allocator<T>>;
  }
}

Class template std::deque

namespace std {
  template<class T, class Allocator = allocator<T>>
  class deque
  {
  public:
    // types
    using 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 */;
    using difference_type        = /* implementation-defined */;
    using iterator               = /* implementation-defined */;
    using const_iterator         = /* implementation-defined */;
    using reverse_iterator       = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
    // construct/copy/destroy
    deque()
      : deque(Allocator())
    {
    }
    explicit deque(const Allocator&);
    explicit deque(size_type n, const Allocator& = Allocator());
    deque(size_type n, const T& value, const Allocator& = Allocator());
    template<class InputIter>
    deque(InputIter first, InputIter last, const Allocator& = Allocator());
    template<container-compatible-range<T> R>
    deque(from_range_t, R&& rg, const Allocator& = Allocator());
    deque(const deque& x);
    deque(deque&&);
    deque(const deque&, const type_identity_t<Allocator>&);
    deque(deque&&, const type_identity_t<Allocator>&);
    deque(initializer_list<T>, const Allocator& = Allocator());
 
    ~deque();
    deque& operator=(const deque& x);
    deque& operator=(deque&& x) noexcept(
      allocator_traits<Allocator>::is_always_equal::value);
    deque& operator=(initializer_list<T>);
    template<class InputIter>
    void assign(InputIter first, InputIter last);
    template<container-compatible-range<T> R>
    void assign_range(R&& rg);
    void assign(size_type n, const T& t);
    void assign(initializer_list<T>);
    allocator_type get_allocator() const noexcept;
 
    // iterators
    iterator begin() noexcept;
    const_iterator begin() const noexcept;
    iterator end() noexcept;
    const_iterator end() const noexcept;
    reverse_iterator rbegin() noexcept;
    const_reverse_iterator rbegin() const noexcept;
    reverse_iterator rend() noexcept;
    const_reverse_iterator rend() const noexcept;
 
    const_iterator cbegin() const noexcept;
    const_iterator cend() const noexcept;
    const_reverse_iterator crbegin() const noexcept;
    const_reverse_iterator crend() const noexcept;
 
    // capacity
    bool empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() const noexcept;
    void resize(size_type sz);
    void resize(size_type sz, const T& c);
    void shrink_to_fit();
 
    // element access
    reference operator[](size_type n);
    const_reference operator[](size_type n) const;
    reference at(size_type n);
    const_reference at(size_type n) const;
    reference front();
    const_reference front() const;
    reference back();
    const_reference back() const;
 
    // modifiers
    template<class... Args>
    reference emplace_front(Args&&... args);
    template<class... Args>
    reference emplace_back(Args&&... args);
    template<class... Args>
    iterator emplace(const_iterator position, Args&&... args);
 
    void push_front(const T& x);
    void push_front(T&& x);
    template<container-compatible-range<T> R>
    void prepend_range(R&& rg);
    void push_back(const T& x);
    void push_back(T&& x);
    template<container-compatible-range<T> R>
    void append_range(R&& rg);
 
    iterator insert(const_iterator position, const T& x);
    iterator insert(const_iterator position, T&& x);
    iterator insert(const_iterator position, size_type n, const T& x);
    template<class InputIter>
    iterator insert(const_iterator position, InputIter first, InputIter last);
    template<container-compatible-range<T> R>
    iterator insert_range(const_iterator position, R&& rg);
    iterator insert(const_iterator position, initializer_list<T>);
 
    void pop_front();
    void pop_back();
 
    iterator erase(const_iterator position);
    iterator erase(const_iterator first, const_iterator last);
    void swap(deque&) noexcept(allocator_traits<Allocator>::is_always_equal::value);
    void clear() noexcept;
  };
 
  template<class InputIter, class Allocator = allocator</*iter-value-type*/<InputIter>>>
  deque(InputIter, InputIter, Allocator = Allocator())
    -> deque</*iter-value-type*/<InputIter>, Allocator>;
 
  template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>>
  deque(from_range_t, R&&, Allocator = Allocator())
    -> deque<ranges::range_value_t<R>, Allocator>;
}
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