`<deque>`

Include the STL standard header <deque> to define the container template class deque and several supporting templates.

namespace std {
template<class Ty, class Alloc>
    class deque;

        // TEMPLATE FUNCTIONS
template<class Ty, class Alloc>
    bool operator==(
        const deque<Ty, Alloc>& left,
        const deque<Ty, Alloc>& right);
template<class Ty, class Alloc>
    bool operator!=(
        const deque<Ty, Alloc>& left,
        const deque<Ty, Alloc>& right);
template<class Ty, class Alloc>
    bool operator<(
        const deque<Ty, Alloc>& left,
        const deque<Ty, Alloc>& right);
template<class Ty, class Alloc>
    bool operator>(
        const deque<Ty, Alloc>& left,
        const deque<Ty, Alloc>& right);
template<class Ty, class Alloc>
    bool operator<=(
        const deque<Ty, Alloc>& left,
        const deque<Ty, Alloc>& right);
template<class Ty, class Alloc>
    bool operator>=(
        const deque<Ty, Alloc>& left,
        const deque<Ty, Alloc>& right);

template<class Ty, class Alloc>
    void swap(
        deque<Ty, Alloc>& left,
        deque<Ty, Alloc>& right);
}  // namespace std

`deque`

allocator_type · assign · at · back · begin · cbegin · cend · clear · const_iterator · const_pointer · const_reference · const_reverse_iterator · crbegin · crend · deque · difference_type · emplace · emplace_back · emplace_front · empty · end · erase · front · get_allocator · insert · iterator · max_size · operator= · operator[] · pointer · pop_back · pop_front · push_back · push_front · rbegin · reference · rend · resize · reverse_iterator · shrink_to_fit · size · size_type · swap · value_type

template<class Ty, class Alloc = allocator<Ty> >
    class deque {
public:
    typedef Alloc allocator_type;
    typedef typename Alloc::pointer pointer;
    typedef typename Alloc::const_pointer const_pointer;
    typedef typename Alloc::reference reference;
    typedef typename Alloc::const_reference const_reference;
    typedef typename Alloc::value_type value_type;
    typedef typename Alloc::size_type size_type;
    typedef typename Alloc::difference_type difference_type;

    typedef T0 iterator;
    typedef T1 const_iterator;
    typedef reverse_iterator<const_iterator>
        const_reverse_iterator;
    typedef reverse_iterator<iterator>
        reverse_iterator;

    deque();
    explicit deque(const Alloc& al);

    explicit deque(size_type count);
    deque(size_type count, const Ty& val);
    deque(size_type count, const Ty& val,
        const Alloc& al);

    deque(const deque& right);
    deque(const deque& right,
        const Alloc& al); [added with C++11]
    deque(deque&& right); [added with C++11]
    deque(deque&& right,
        const Alloc& al); [added with C++11]

    template<class InIt>
        deque(InIt first, InIt last);
    template<class InIt>
        deque(InIt first, InIt last, const Alloc& al);

    deque(initializer_list<Ty> init) [added with C++11]
    deque(initializer_list<Ty> init,
        const Alloc& al); [added with C++11]

    deque& operator=(const deque& right);
    deque& operator=(initializer_list<Ty> init) [added with C++11]
    deque& operator=(deque&& right); [added with C++11]

    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; [added with C++11]
    const_iterator cend() const noexcept; [added with C++11]
    const_reverse_iterator crbegin() const noexcept; [added with C++11]
    const_reverse_iterator crend() const noexcept; [added with C++11]

    void shrink_to_fit(); [added with C++11]
    void resize(size_type newsize);
    void resize(size_type newsize, const Ty& val);
    size_type size() const noexcept;
    size_type max_size() const noexcept;
    bool empty() const noexcept;

    Alloc get_allocator() const noexcept;

    reference at(size_type pos);
    const_reference at(size_type pos) const;
    reference operator[](size_type pos);
    const_reference operator[](size_type pos) const;
    reference front();
    const_reference front() const;
    reference back();
    const_reference back() const;

    void push_front(const Ty& val);
    void push_front(Ty&& val); [added with C++11]
    template<class... Valty>
        void emplace_front(Ty&&... val); [added with C++11]
    void pop_front();

    void push_back(const Ty& val);
    void push_back(Ty&& val); [added with C++11]
    template<class... Valty>
        void emplace_back(Ty&&... val); [added with C++11]
    void pop_back();

    template<class InIt>
        void assign(InIt first, InIt last);
    void assign(size_type count, const Ty& val);
    void assign(initializer_list<Ty> init) [added with C++11]

    iterator insert(const_iterator where, const Ty& val);
    iterator insert(const_iterator where, size_type count, const Ty& val);
    template<class InIt>
        iterator insert(const_iterator where, InIt first, InIt last);
    iterator insert(const iterator where,
        initializer_list<Ty> init) [added with C++11]
    iterator insert(const_iterator where, Ty&& val); [added with C++11]

    template<class... Valty>
        iterator emplace(const_iterator where, Ty&&... val); [added with C++11]

    iterator erase(const_iterator where);
    iterator erase(const_iterator first, const_iterator last);
    void clear() noexcept;

    void swap(deque& right);
    };

The template class describes an object that controls a varying-length sequence of elements of type Ty. The sequence is represented in a way that permits insertion and removal of an element at either end with a single element copy (constant time). Such operations in the middle of the sequence require element copies and assignments proportional to the number of elements in the sequence (linear time).

The object allocates and frees storage for the sequence it controls through a stored allocator object of class Alloc. Such an allocator object must have the same external interface as an object of template class allocator.

Deque reallocation occurs when a member function must insert or erase elements of the controlled sequence:

If an element is inserted into an empty sequence, or if an element is erased to leave an empty sequence, then iterators earlier returned by begin() and end() become invalid.
If an element is inserted at begin() or at end(), then all iterators become invalid, but no references that designate existing elements become invalid.
If an element is erased at begin() or at end(), then only iterators and references that designate the erased element become invalid.
Otherwise, inserting or erasing an element invalidates all iterators and references.

`deque::allocator_type`

typedef Alloc allocator_type;

The type is a synonym for the template parameter Alloc.

`deque::assign`

template<class InIt>
    void assign(InIt first, InIt last);
void assign(size_type count, const Ty& val);
void assign(initializer_list<Ty> init) [added with C++11]

If InIt is an integer type, the first member function behaves the same as assign((size_type)first, (Ty)last). Otherwise, the first member function replaces the sequence controlled by *this with the sequence [first, last), which must not overlap the initial controlled sequence. The second member function replaces the sequence controlled by *this with a repetition of count elements of value val.

The third member function replaces the controlled sequence from an object of class initializer_list<Ty>.

`deque::at`

const_reference at(size_type pos) const;
reference at(size_type pos);

The member function returns a reference to the element of the controlled sequence at position pos. If that position is invalid, the function throws an object of class out_of_range.

`deque::back`

reference back();
const_reference back() const;

The member function returns a reference to the last element of the controlled sequence, which must be non-empty.

`deque::begin`

const_iterator begin() const noexcept;
iterator begin() noexcept;

The member function returns a random-access iterator that points at the first element of the sequence (or just beyond the end of an empty sequence).

`deque::cbegin`

const_iterator cbegin() const noexcept; [added with C++11]

The member functions return a random-access iterator that points at the first element of the sequence (or just beyond the end of an empty sequence).

`deque::cend`

const_reference cend() const noexcept; [added with C++11]

The member functions return a random-access iterator that points just beyond the end of the sequence.

`deque::clear`

void clear() noexcept;

The member function calls erase( begin(), end()).

`deque::const_iterator`

typedef T1 const_iterator;

The type describes an object that can serve as a constant random-access iterator for the controlled sequence. It is described here as a synonym for the implementation-defined type T1.

`deque::const_pointer`

typedef typename Alloc::const_pointer const_pointer;

The type describes an object that can serve as a constant pointer to an element of the controlled sequence.

`deque::const_reference`

typedef typename Alloc::const_reference const_reference;

The type describes an object that can serve as a constant reference to an element of the controlled sequence.

`deque::const_reverse_iterator`

typedef reverse_iterator<const_iterator>
    const_reverse_iterator;

The type describes an object that can serve as a constant reverse random-access iterator for the controlled sequence.

`deque::crbegin`

const_reverse_iterator crbegin() const noexcept; [added with C++11]

The member functions return a reverse iterator that points just beyond the end of the controlled sequence. Hence, it designates the beginning of the reverse sequence.

`deque::crend`

const_reverse_iterator crend() const noexcept; [added with C++11]

The member functions return a reverse iterator that points at the first element of the sequence (or just beyond the end of an empty sequence)). Hence, it designates the end of the reverse sequence.

`deque::deque`

deque();
explicit deque(const Alloc& al);

explicit deque(size_type count);
deque(size_type count, const Ty& val);
deque(size_type count, const Ty& val,
    const Alloc& al);

deque(const deque& right);
deque(const deque& right,
    const Alloc& al); [added with C++11]
deque(deque&& right); [added with C++11]
deque(deque&& right,
    const Alloc& al); [added with C++11]

template<class InIt>
    deque(InIt first, InIt last);
template<class InIt>
    deque(InIt first, InIt last, const Alloc& al);

deque(initializer_list<Ty> init) [added with C++11]
deque(initializer_list<Ty> init,
    const Alloc& al); [added with C++11]

All constructors store an allocator object and initialize the controlled sequence. The allocator object is the argument al, if present. Otherwise, for the copy and move constructors, it is right.get_allocator(). Otherwise, it is Alloc().

The first two constructors specify an empty initial controlled sequence.

The next three constructors specify a repetition of count elements of value val, if specified. Otherwise the repeated value is Ty().

The next four constructors specify a copy of the sequence controlled by right. The last two of these constructors are the same as the first two, but with an rvalue reference.

The next two constructors specify the sequence [first, last).

The last two constructors specify the initial controlled sequence with an object of class initializer_list<Ty>.

`deque::difference_type`

typedef typename Alloc::difference_type difference_type;

The signed integer type describes an object that can represent the difference between the addresses of any two elements in the controlled sequence.

`deque::emplace`

template<class... Valty>
    iterator emplace(const_iterator where, Valty&&... val); [added with C++11]

The member function effectively returns insert(where, value_type(forward<Valty>(val)...)), except that the element value is constructed in place.

The member function is a variadic template using rvalue references. It inserts an element with the constructor arguments val... before the element pointed to by where in the controlled sequence. It returns an iterator that designates the newly inserted element. Its behavior is otherwise the same as insert.

`deque::emplace_back`

template<class... Valty>
    void emplace_back(Ty&&... val); [added with C++11]

The member function effectively returns insert(end(), value_type(forward<Valty>(val)...)), except that the element value is constructed in place.

Inserting the element invalidates all iterators, but no references, to existing elements.

If an exception is thrown, the container is left unaltered and the exception is rethrown.

`deque::emplace_front`

template<class... Valty>
    void emplace_front(Ty&&... val); [added with C++11]

The member function effectively returns insert(begin(), value_type(forward<Valty>(val)...)), except that the element value is constructed in place.

Inserting the element invalidates all iterators, but no references, to existing elements.

If an exception is thrown, the container is left unaltered and the exception is rethrown.

`deque::empty`

bool empty() const noexcept;

The member function returns true for an empty controlled sequence.

`deque::end`

const_iterator end() const noexcept;
iterator end() noexcept;

The member function returns a random-access iterator that points just beyond the end of the sequence.

`deque::erase`

iterator erase(const_iterator where);
iterator erase(const_iterator first, const_iterator last);

The first member function removes the element of the controlled sequence pointed to by where. The second member function removes the elements of the controlled sequence in the range [first, last). Both return an iterator that designates the first element remaining beyond any elements removed, or end() if no such element exists.

Removing N elements causes N destructor calls and an assignment for each of the elements between the insertion point and the nearer end of the sequence. Removing an element at either end invalidates only iterators and references that designate the erased elements. Otherwise, erasing an element invalidates all iterators and references.

The member functions throw an exception only if a copy operation throws an exception.

`deque::front`

reference front();
const_reference front() const;

The member function returns a reference to the first element of the controlled sequence, which must be non-empty.

`deque::get_allocator`

Alloc get_allocator() const noexcept;

The member function returns the stored allocator object.

`deque::insert`

iterator insert(const_iterator where, const Ty& val);
void insert(const_iterator where, size_type count, const Ty& val);
template<class InIt>
    void insert(const_iterator where, InIt first, InIt last);
void insert(const iterator where,
    initializer_list<Ty> init) [added with C++11]
iterator insert(const_iterator where, Ty&& val); [added with C++11]

Each of the member functions inserts, before the element pointed to by where in the controlled sequence, a sequence specified by the remaining operands. It then returns an iterator designating the first element in the inserted sequence, or where if the inserted sequence is empty.

The first member function inserts a single element with value val and returns an iterator that designates the newly inserted element. The second member function inserts a repetition of count elements of value val.

If InIt is an integer type, the third member function behaves the same as insert(where, (size_type)first, (Ty)last). Otherwise, the third member function inserts the sequence [first, last), which must not overlap the initial controlled sequence.

The fourth member function inserts the sequence specified by an object of class initializer_list<Ty>.

The last member function is the same as the first, but with an rvalue reference.

When inserting a single element, the number of element copies is linear in the number of elements between the insertion point and the nearer end of the sequence. When inserting a single element at either end of the sequence, the amortized number of element copies is constant. When inserting N elements, the number of element copies is linear in N plus the number of elements between the insertion point and the nearer end of the sequence -- except when the template member is specialized for InIt an input or forward iterator, which behaves like N single insertions. Inserting an element at either end invalidates all iterators, but no references, that designate existing elements. Otherwise, inserting an element invalidates all iterators and references.

If an exception is thrown during the insertion of one or more elements, and the exception is not thrown while copying an element, the container is left unaltered and the exception is rethrown.

`deque::iterator`

typedef T0 iterator;

The type describes an object that can serve as a random-access iterator for the controlled sequence. It is described here as a synonym for the implementation-defined type T0.

`deque::max_size`

size_type max_size() const noexcept;

The member function returns the length of the longest sequence that the object can control.

`deque::operator=`

deque& operator=(const deque& right);
deque& operator=(initializer_list<Ty> init) [added with C++11]
deque& operator=(deque&& right); [added with C++11]

The first member operator replaces the controlled sequence with a copy of the sequence controlled by right.

The second member operator replaces the controlled sequence from an object of class initializer_list<Ty>.

The third member operator is the same as the first, but with an rvalue reference.

`deque::operator[]`

const_reference operator[](size_type pos) const;
reference operator[](size_type pos);

The member function returns a reference to the element of the controlled sequence at position pos. If that position is invalid, the behavior is undefined.

`deque::pointer`

typedef typename Alloc::pointer pointer;

The type describes an object that can serve as a pointer to an element of the controlled sequence.

`deque::pop_back`

void pop_back();

The member function removes the last element of the controlled sequence, which must be non-empty. Removing the element invalidates only iterators and references that designate the erased element.

The member function never throws an exception.

`deque::pop_front`

void pop_front();

The member function removes the first element of the controlled sequence, which must be non-empty. Removing the element invalidates only iterators and references that designate the erased element.

The member function never throws an exception.

`deque::push_back`

void push_back(const Ty& val);
void push_back(Ty&& val); [added with C++11]

The member function inserts an element with value val at the end of the controlled sequence.

Inserting the element invalidates all iterators, but no references, to existing elements.

If an exception is thrown, the container is left unaltered and the exception is rethrown.

`deque::push_front`

void push_front(const Ty& val);
void push_front(Ty&& val); [added with C++11]

The member function inserts an element with value val at the beginning of the controlled sequence.

Inserting the element invalidates all iterators, but no references, to existing elements.

If an exception is thrown, the container is left unaltered and the exception is rethrown.

`deque::rbegin`

const_reverse_iterator rbegin() const noexcept;
reverse_iterator rbegin() noexcept;

The member function returns a reverse iterator that points just beyond the end of the controlled sequence. Hence, it designates the beginning of the reverse sequence.

`deque::reference`

typedef typename Alloc::reference reference;

The type describes an object that can serve as a reference to an element of the controlled sequence.

`deque::rend`

const_reverse_iterator rend() const noexcept;
reverse_iterator rend() noexcept;

The member function returns a reverse iterator that points at the first element of the sequence (or just beyond the end of an empty sequence). Hence, it designates the end of the reverse sequence.

`deque::resize`

void resize(size_type newsize);
void resize(size_type newsize, const Ty& val);

The member functions both ensure that size() henceforth returns newsize. If it must make the controlled sequence longer, the first member function appends elements with value Ty(), while the second member function appends elements with value val. To make the controlled sequence shorter, both member functions call erase(begin() + newsize, end()).

`deque::reverse_iterator`

typedef reverse_iterator<iterator>
    reverse_iterator;

The type describes an object that can serve as a reverse random-access iterator for the controlled sequence.

`deque::shrink_to_fit`

void shrink_to_fit();

The member function eliminates any unneeded storage in the container.

`deque::size`

size_type size() const noexcept;

The member function returns the length of the controlled sequence.

`deque::size_type`

typedef typename Alloc::size_type size_type;

The unsigned integer type describes an object that can represent the length of any controlled sequence.

`deque::swap`

void swap(deque& right);

The member function swaps the controlled sequences between *this and right. If get_allocator() == right.get_allocator(), it does so in constant time, it throws no exceptions, and it invalidates no references, pointers, or iterators that designate elements in the two controlled sequences. Otherwise, it performs a number of element assignments and constructor calls proportional to the number of elements in the two controlled sequences.

`deque::value_type`

typedef typename Alloc::value_type value_type;

The type is a synonym for the template parameter Ty.

`operator!=`

template<class Ty, class Alloc>
    bool operator!=(
        const deque <Ty, Alloc>& left,
        const deque <Ty, Alloc>& right);

The template function returns !(left == right).

`operator==`

template<class Ty, class Alloc>
    bool operator==(
        const deque <Ty, Alloc>& left,
        const deque <Ty, Alloc>& right);

The template function overloads operator== to compare two objects of template class deque. The function returns left.size() == right.size() && equal(left. begin(), left. end(), right.begin()).

`operator<`

template<class Ty, class Alloc>
    bool operator<(
        const deque <Ty, Alloc>& left,
        const deque <Ty, Alloc>& right);

The template function overloads operator< to compare two objects of template class deque. The function returns lexicographical_compare(left. begin(), left. end(), right.begin(), right.end()).

`operator<=`

template<class Ty, class Alloc>
    bool operator<=(
        const deque <Ty, Alloc>& left,
        const deque <Ty, Alloc>& right);

The template function returns !(right < left).

`operator>`

template<class Ty, class Alloc>
    bool operator>(
        const deque <Ty, Alloc>& left,
        const deque <Ty, Alloc>& right);

The template function returns right < left.

`operator>=`

template<class Ty, class Alloc>
    bool operator>=(
        const deque <Ty, Alloc>& left,
        const deque <Ty, Alloc>& right);

The template function returns !(left < right).

`swap`

template<class Ty, class Alloc>
    void swap(
        deque <Ty, Alloc>& left,
        deque <Ty, Alloc>& right);

The template function executes left.swap(right).

See also the Table of Contents and the Index.