# Standard library header <deque>

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This header is part of the containers library.

### Classes

deque | double-ended queue (class template)

### Functions

operator==operator!=operator<operator<=operator>operator>= | lexicographically compares the values in the deque (function template)
std::swap(std::deque) | specializes the std::swap algorithm (function template)

### Synopsis

    #include <initializer_list>

    namespace std {
        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>
            bool operator<(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
        template <class T, class Allocator>
            bool operator!=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
        template <class T, class Allocator>
            bool operator>(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
        template <class T, class Allocator>
            bool operator>=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
        template <class T, class Allocator>
            bool 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);
    }

### Class std::deque

    template <class T, class Allocator = allocator<T> >
    class deque {
    public:
        // types:
        typedef value_type&                                         reference;
        typedef const value_type&                                   const_reference;
        typedef /*implementation-defined*/                          iterator;
        typedef /*implementation-defined*/                          const_iterator;
        typedef /*implementation-defined*/                          size_type;
        typedef /*implementation-defined*/                          difference_type;
        typedef T                                                   value_type;
        typedef Allocator                                           allocator_type;
        typedef typename allocator_traits<Allocator>::pointer       pointer;
        typedef typename allocator_traits<Allocator>::const_pointer const_pointer;
        typedef std::reverse_iterator<iterator>                     reverse_iterator;
        typedef std::reverse_iterator<const_iterator>               const_reverse_iterator;

        // construct/copy/destroy:
        explicit deque(const Allocator& = Allocator());
        explicit deque(size_type n);
        deque(size_type n, const T& value,const Allocator& = Allocator());
        template <class InputIterator>
            deque(InputIterator first, InputIterator last,const Allocator& = Allocator());
        deque(const deque<T,Allocator>& x);
        deque(deque&&);
        deque(const deque&, const Allocator&);
        deque(deque&&, const Allocator&);
        deque(initializer_list<T>, const Allocator& = Allocator());

        ~deque();
        deque<T,Allocator>& operator=(const deque<T,Allocator>& x);
        deque<T,Allocator>& operator=(deque<T,Allocator>&& x);
        deque& operator=(initializer_list<T>);
        template <class InputIterator>
        void assign(InputIterator first, InputIterator last);
        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() noexcept;
        const_iterator          cend() noexcept;
        const_reverse_iterator  crbegin() const noexcept;
        const_reverse_iterator  crend() const noexcept;

        // capacity:
        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();
        bool      empty() const noexcept;

        // 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> void emplace_front(Args&&... args);
        template <class... Args> void 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);
        void push_back(const T& x);
        void push_back(T&& x);

        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 InputIterator>
            iterator insert (const_iterator position, InputIterator first,
                             InputIterator last);
        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<T,Allocator>&);
        void     clear() noexcept;
    };

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