23 Containers library [containers]

The header <array> defines a class template for storing fixed-size sequences of objects. An array supports random access iterators. An instance of array<T, N> stores N elements of type T, so that size() == N is an invariant. The elements of an array are stored contiguously, meaning that if a is an array<T, N> then it obeys the identity &a[n] == &a[0] + n for all 0 <= n < N.

An array is an aggregate ([dcl.init.aggr]) that can be initialized with the syntax

array<T, N> a = { initializer-list };

where initializer-list is a comma-separated list of up to N elements whose types are convertible to T.

An array satisfies all of the requirements of a container and of a reversible container ([container.requirements]), except that a default constructed array object is not empty and that swap does not have constant complexity. An array satisfies some of the requirements of a sequence container ([sequence.reqmts]). Descriptions are provided here only for operations on array that are not described in one of these tables and for operations where there is additional semantic information.

namespace std {
  template <class T, size_t N>
  struct array {
    //  types:
    typedef T&                                    reference;
    typedef const T&                              const_reference;
    typedef implementation-defined                iterator;
    typedef implementation-defined                const_iterator;
    typedef size_t                                size_type;
    typedef ptrdiff_t                             difference_type;
    typedef T                                     value_type;
    typedef T*                                    pointer;
    typedef const T*                              const_pointer;
    typedef std::reverse_iterator<iterator>       reverse_iterator;
    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

    T       elems[N];           // exposition only

    // no explicit construct/copy/destroy for aggregate type

    void fill(const T& u);
    void swap(array&) noexcept(noexcept(swap(declval<T&>(), declval<T&>())));

    // 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:
    constexpr size_type size() const noexcept;
    constexpr size_type max_size() const noexcept;
    constexpr bool      empty() const noexcept;

    // element access:
    reference                 operator[](size_type n);
    constexpr const_reference operator[](size_type n) const;
    reference                 at(size_type n);
    constexpr const_reference at(size_type n) const;
    reference                 front();
    constexpr const_reference front() const;
    reference                 back();
    constexpr const_reference back() const;

    T *       data() noexcept;
    const T * data() const noexcept;
  };
}

[ Note: The member variable elems is shown for exposition only, to emphasize that array is a class aggregate. The name elems is not part of array's interface.  — end note ]

The conditions for an aggregate ([dcl.init.aggr]) shall be met. Class array relies on the implicitly-declared special member functions ([class.ctor], [class.dtor], and [class.copy]) to conform to the container requirements table in [container.requirements]. In addition to the requirements specified in the container requirements table, the implicit move constructor and move assignment operator for array require that T be MoveConstructible or MoveAssignable, respectively.

array shall provide support for the special case N == 0.

In the case that N == 0, begin() == end() == unique value. The return value of data() is unspecified.

The effect of calling front() or back() for a zero-sized array is undefined.

Member function swap() shall have a noexcept-specification which is equivalent to noexcept(true).

A deque is a sequence container that, like a vector ([vector]), supports random access iterators. 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. That is, a deque is especially optimized for pushing and popping elements at the beginning and end. As with vectors, storage management is handled automatically.

A deque satisfies all of the requirements of a container, of a reversible container (given in tables in [container.requirements]), of a sequence container, including the optional sequence container requirements ([sequence.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). Descriptions are provided here only for operations on deque that are not described in one of these tables or for operations where there is additional semantic information.

namespace std {
  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;       // See [container.requirements]
    typedef implementation-defined                const_iterator; // See [container.requirements]
    typedef implementation-defined                size_type;      // See [container.requirements]
    typedef implementation-defined                difference_type;// See [container.requirements]
    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;

    // [deque.cons], 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 InputIterator>
      deque(InputIterator first, InputIterator last, const Allocator& = Allocator());
    deque(const deque& x);
    deque(deque&&);
    deque(const deque&, const Allocator&);
    deque(deque&&, const Allocator&);
    deque(initializer_list<T>, const Allocator& = Allocator());

    ~deque();
    deque& operator=(const deque& x);
    deque& operator=(deque&& 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() const noexcept;
    const_iterator         cend() const noexcept;
    const_reverse_iterator crbegin() const noexcept;
    const_reverse_iterator crend() const noexcept;

    // [deque.capacity], 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;

    // [deque.modifiers], 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&);
    void     clear() noexcept;
  };

  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);

  // specialized algorithms:
  template <class T, class Allocator>
    void swap(deque<T,Allocator>& x, deque<T,Allocator>& y);
}

A forward_list is a container that supports forward iterators and allows constant time insert and erase operations anywhere within the sequence, with storage management handled automatically. Fast random access to list elements is not supported. [ Note: It is intended that forward_list have zero space or time overhead relative to a hand-written C-style singly linked list. Features that would conflict with that goal have been omitted. — end note ]

A forward_list satisfies all of the requirements of a container (Table [tab:containers.container.requirements]), except that the size() member function is not provided and operator== has linear complexity. A forward_list also satisfies all of the requirements for an allocator-aware container (Table [tab:containers.allocatoraware]). In addition, a forward_list provides the assign member functions (Table [tab:containers.sequence.requirements]) and several of the optional container requirements (Table [tab:containers.sequence.optional]). Descriptions are provided here only for operations on forward_list that are not described in that table or for operations where there is additional semantic information.

[ Note: Modifying any list requires access to the element preceding the first element of interest, but in a forward_list there is no constant-time way to access a preceding element. For this reason, ranges that are modified, such as those supplied to erase and splice, must be open at the beginning.  — end note ]

namespace std {
  template <class T, class Allocator = allocator<T> >
  class forward_list {
  public:
    // types:
    typedef value_type&                                           reference;
    typedef const value_type&                                     const_reference;
    typedef implementation-defined iterator;       // See [container.requirements]
    typedef implementation-defined const_iterator; // See [container.requirements]
    typedef implementation-defined size_type;      // See [container.requirements]
    typedef implementation-defined difference_type;// See [container.requirements]
    typedef T value_type;
    typedef Allocator allocator_type;
    typedef typename allocator_traits<Allocator>::pointer         pointer;
    typedef typename allocator_traits<Allocator>::const_pointer   const_pointer;

    // [forwardlist.cons], construct/copy/destroy:
    forward_list() : forward_list(Allocator()) { }
    explicit forward_list(const Allocator&);
    explicit forward_list(size_type n, const Allocator& = Allocator());
    forward_list(size_type n, const T& value,
                 const Allocator& = Allocator());
    template <class InputIterator>
      forward_list(InputIterator first, InputIterator last,
                   const Allocator& = Allocator());
    forward_list(const forward_list& x);
    forward_list(forward_list&& x);
    forward_list(const forward_list& x, const Allocator&);
    forward_list(forward_list&& x, const Allocator&);
    forward_list(initializer_list<T>, const Allocator& = Allocator());
    ~forward_list();
    forward_list& operator=(const forward_list& x);
    forward_list& operator=(forward_list&& x);
    forward_list& 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;

    // [forwardlist.iter], iterators:
    iterator before_begin() noexcept;
    const_iterator before_begin() const noexcept;
    iterator begin() noexcept;
    const_iterator begin() const noexcept;
    iterator end() noexcept;
    const_iterator end() const noexcept;

    const_iterator cbegin() const noexcept;
    const_iterator cbefore_begin() const noexcept;
    const_iterator cend() const noexcept;

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

    // [forwardlist.access], element access:
    reference front();
    const_reference front() const;

    // [forwardlist.modifiers], modifiers:
    template <class... Args> void emplace_front(Args&&... args);
    void push_front(const T& x);
    void push_front(T&& x);
    void pop_front();

    template <class... Args> iterator emplace_after(const_iterator position, Args&&... args);
    iterator insert_after(const_iterator position, const T& x);
    iterator insert_after(const_iterator position, T&& x);

    iterator insert_after(const_iterator position, size_type n, const T& x);
    template <class InputIterator>
      iterator insert_after(const_iterator position, InputIterator first, InputIterator last);
    iterator insert_after(const_iterator position, initializer_list<T> il);

    iterator erase_after(const_iterator position);
    iterator erase_after(const_iterator position, const_iterator last);
    void swap(forward_list&);

    void resize(size_type sz);
    void resize(size_type sz, const value_type& c);
    void clear() noexcept;

    // [forwardlist.ops], forward_list operations:
    void splice_after(const_iterator position, forward_list& x);
    void splice_after(const_iterator position, forward_list&& x);
    void splice_after(const_iterator position, forward_list& x,
                      const_iterator i);
    void splice_after(const_iterator position, forward_list&& x,
                      const_iterator i);
    void splice_after(const_iterator position, forward_list& x,
                      const_iterator first, const_iterator last);
    void splice_after(const_iterator position, forward_list&& x,
                      const_iterator first, const_iterator last);

    void remove(const T& value);
    template <class Predicate> void remove_if(Predicate pred);

    void unique();
    template <class BinaryPredicate> void unique(BinaryPredicate binary_pred);

    void merge(forward_list& x);
    void merge(forward_list&& x);
    template <class Compare> void merge(forward_list& x, Compare comp);
    template <class Compare> void merge(forward_list&& x, Compare comp);

    void sort();
    template <class Compare> void sort(Compare comp);

    void reverse() noexcept;
  };

  // Comparison operators
  template <class T, class Allocator>
    bool operator==(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator< (const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator> (const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);

  // [forwardlist.spec], specialized algorithms:
  template <class T, class Allocator>
    void swap(forward_list<T,Allocator>& x, forward_list<T,Allocator>& y);
}

None of the overloads of insert_after shall affect the validity of iterators and references, and erase_after shall invalidate only iterators and references to the erased elements. If an exception is thrown during insert_after there shall be no effect. Inserting n elements into a forward_list is linear in n, and the number of calls to the copy or move constructor of T is exactly equal to n. Erasing n elements from a forward_list is linear in n and the number of calls to the destructor of type T is exactly equal to n.

template <class... Args> void emplace_front(Args&&... args);

A list is a sequence container that supports bidirectional iterators and allows constant time insert and erase operations anywhere within the sequence, with storage management handled automatically. Unlike vectors ([vector]) and deques ([deque]), fast random access to list elements is not supported, but many algorithms only need sequential access anyway.

A list satisfies all of the requirements of a container, of a reversible container (given in two tables in [container.requirements]), of a sequence container, including most of the optional sequence container requirements ([sequence.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). The exceptions are the operator[] and at member functions, which are not provided.265 Descriptions are provided here only for operations on list that are not described in one of these tables or for operations where there is additional semantic information.

namespace std {
  template <class T, class Allocator = allocator<T> >
  class list {
  public:
    // types:
    typedef value_type&                                             reference;
    typedef const value_type&                                       const_reference;
    typedef implementation-defined                iterator;       // see [container.requirements]
    typedef implementation-defined                const_iterator; // see [container.requirements]
    typedef implementation-defined                size_type;      // see [container.requirements]
    typedef implementation-defined                difference_type;// see [container.requirements]
    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;

    // [list.cons], construct/copy/destroy:
    list() : list(Allocator()) { }
    explicit list(const Allocator&);
    explicit list(size_type n, const Allocator& = Allocator());
    list(size_type n, const T& value, const Allocator& = Allocator());
    template <class InputIterator>
      list(InputIterator first, InputIterator last, const Allocator& = Allocator());
    list(const list& x);
    list(list&& x);
    list(const list&, const Allocator&);
    list(list&&, const Allocator&);
    list(initializer_list<T>, const Allocator& = Allocator());
   ~list();
    list& operator=(const list& x);
    list& operator=(list&& x);
    list& 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() const noexcept;
    const_iterator         cend() const noexcept;
    const_reverse_iterator crbegin() const noexcept;
    const_reverse_iterator crend() const noexcept;

    // [list.capacity], 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);

    // element access:
    reference       front();
    const_reference front() const;
    reference       back();
    const_reference back() const;

    // [list.modifiers], modifiers:
    template <class... Args> void emplace_front(Args&&... args);
    void pop_front();
    template <class... Args> void emplace_back(Args&&... args);
    void push_front(const T& x);
    void push_front(T&& x);
    void push_back(const T& x);
    void push_back(T&& x);
    void pop_back();

    template <class... Args> iterator emplace(const_iterator position, Args&&... args);
    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> il);

    iterator erase(const_iterator position);
    iterator erase(const_iterator position, const_iterator last);
    void     swap(list&);
    void     clear() noexcept;

    // [list.ops], list operations:
    void splice(const_iterator position, list& x);
    void splice(const_iterator position, list&& x);
    void splice(const_iterator position, list& x, const_iterator i);
    void splice(const_iterator position, list&& x, const_iterator i);
    void splice(const_iterator position, list& x,
                const_iterator first, const_iterator last);
    void splice(const_iterator position, list&& x,
                const_iterator first, const_iterator last);

    void remove(const T& value);
    template <class Predicate> void remove_if(Predicate pred);

    void unique();
    template <class BinaryPredicate>
      void unique(BinaryPredicate binary_pred);

    void merge(list& x);
    void merge(list&& x);
    template <class Compare> void merge(list& x, Compare comp);
    template <class Compare> void merge(list&& x, Compare comp);

    void sort();
    template <class Compare> void sort(Compare comp);

    void reverse() noexcept;
  };

  template <class T, class Allocator>
    bool operator==(const list<T,Allocator>& x, const list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator< (const list<T,Allocator>& x, const list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const list<T,Allocator>& x, const list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator> (const list<T,Allocator>& x, const list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const list<T,Allocator>& x, const list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const list<T,Allocator>& x, const list<T,Allocator>& y);

  // specialized algorithms:
  template <class T, class Allocator>
    void swap(list<T,Allocator>& x, list<T,Allocator>& y);
}

Since lists allow fast insertion and erasing from the middle of a list, certain operations are provided specifically for them.266

list provides three splice operations that destructively move elements from one list to another. The behavior of splice operations is undefined if get_allocator() != x.get_allocator().

void splice(const_iterator position, list& x); void splice(const_iterator position, list&& x);

A vector is a sequence container that supports random access iterators. In addition, it supports (amortized) constant time insert and erase operations at the end; insert and erase in the middle take linear time. Storage management is handled automatically, though hints can be given to improve efficiency. The elements of a vector are stored contiguously, meaning that if v is a vector<T, Allocator> where T is some type other than bool, then it obeys the identity &v[n] == &v[0] + n for all 0 <= n < v.size().

A vector satisfies all of the requirements of a container and of a reversible container (given in two tables in [container.requirements]), of a sequence container, including most of the optional sequence container requirements ([sequence.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). The exceptions are the push_front, pop_front, and emplace_front member functions, which are not provided. Descriptions are provided here only for operations on vector that are not described in one of these tables or for operations where there is additional semantic information.

namespace std {
  template <class T, class Allocator = allocator<T> >
  class vector {
  public:
    // types:
    typedef value_type&                           reference;
    typedef const value_type&                     const_reference;
    typedef implementation-defined                iterator;       // see [container.requirements]
    typedef implementation-defined                const_iterator; // see [container.requirements]
    typedef implementation-defined                size_type;      // see [container.requirements]
    typedef implementation-defined                difference_type;// see [container.requirements]
    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;

    // [vector.cons], construct/copy/destroy:
    vector() : vector(Allocator()) { }
    explicit vector(const Allocator&);
    explicit vector(size_type n, const Allocator& = Allocator());
    vector(size_type n, const T& value, const Allocator& = Allocator());
    template <class InputIterator>
      vector(InputIterator first, InputIterator last,
             const Allocator& = Allocator());
    vector(const vector& x);
    vector(vector&&);
    vector(const vector&, const Allocator&);
    vector(vector&&, const Allocator&);
    vector(initializer_list<T>, const Allocator& = Allocator());
   ~vector();
    vector& operator=(const vector& x);
    vector& operator=(vector&& x);
    vector& operator=(initializer_list<T>);
    template <class InputIterator>
      void assign(InputIterator first, InputIterator last);
    void assign(size_type n, const T& u);
    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;

    // [vector.capacity], 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);
    size_type capacity() const noexcept;
    bool      empty() const noexcept;
    void      reserve(size_type n);
    void      shrink_to_fit();

    // element access:
    reference       operator[](size_type n);
    const_reference operator[](size_type n) const;
    const_reference at(size_type n) const;
    reference       at(size_type n);
    reference       front();
    const_reference front() const;
    reference       back();
    const_reference back() const;

    // [vector.data], data access
    T*         data() noexcept;
    const T*  data() const noexcept;

    // [vector.modifiers], modifiers:
    template <class... Args> void emplace_back(Args&&... args);
    void push_back(const T& x);
    void push_back(T&& x);
    void pop_back();

    template <class... Args> iterator emplace(const_iterator position, Args&&... args);
    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> il);
    iterator erase(const_iterator position);
    iterator erase(const_iterator first, const_iterator last);
    void     swap(vector&);
    void     clear() noexcept;
  };

  template <class T, class Allocator>
    bool operator==(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator< (const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator> (const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);

  // [vector.special], specialized algorithms:
  template <class T, class Allocator>
    void swap(vector<T,Allocator>& x, vector<T,Allocator>& y);
}