[array] (original) (raw)

23 Containers library [containers]

23.3 Sequence containers [sequences]

23.3.3 Class template array [array]

23.3.3.1 Overview [array.overview]

The header defines a class template for storing fixed-size sequences of objects.

An instance of array<T, N> stores N elements of type T, so that size() == N is an invariant.

An array is an aggregate that can be list-initialized with up to N elements whose types are convertible to T.

An array meets all of the requirements of a container ([container.reqmts]) and of a reversible container ([container.rev.reqmts]), except that a default constructed array object is not empty if .

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.

array<T, N> is a structural type ([temp.param]) ifT is a structural type.

Two values a1 and a2 of type array<T, N>are template-argument-equivalent if and only if each pair of corresponding elements in a1 and a2are template-argument-equivalent.

namespace std { template<class T, size_t N> struct array { using value_type = T;using pointer = T*;using const_pointer = const T*;using reference = T&;using const_reference = const T&;using size_type = size_t;using difference_type = ptrdiff_t;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>;constexpr void fill(const T& u);constexpr void swap(array&) noexcept(is_nothrow_swappable_v<T>);constexpr 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;constexpr bool empty() const noexcept;constexpr size_type size() const noexcept;constexpr size_type max_size() const noexcept;constexpr 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;constexpr T* data() noexcept;constexpr const T* data() const noexcept;};template<class T, class... U> array(T, U...) -> array<T, 1 + sizeof...(U)>;}

23.3.3.2 Constructors, copy, and assignment [array.cons]

In addition to the requirements specified in the container requirements table, the implicitly-declared move constructor and move assignment operator for arrayrequire that T be Cpp17MoveConstructible or Cpp17MoveAssignable, respectively.

template<class T, class... U> array(T, U...) -> array<T, 1 + sizeof...(U)>;

Mandates: (is_same_v<T, U> && ...) is true.

23.3.3.3 Member functions [array.members]

constexpr size_type size() const noexcept;

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

Returns: A pointer such that [data(), data() + size()) is a valid range.

For a non-empty array, data() == addressof(front()) is true.

constexpr void fill(const T& u);

Effects: As if by fill_n(begin(), N, u).

constexpr void swap(array& y) noexcept(is_nothrow_swappable_v<T>);

Effects: Equivalent to swap_ranges(begin(), end(), y.begin()).

[Note 1:

Unlike the swap function for other containers, array​::​swaptakes linear time, can exit via an exception, and does not cause iterators to become associated with the other container.

— _end note_]

23.3.3.4 Specialized algorithms [array.special]

template<class T, size_t N> constexpr void swap(array<T, N>& x, array<T, N>& y) noexcept(noexcept(x.swap(y)));

Constraints: N == 0 or is_swappable_v<T> is true.

Effects: As if by x.swap(y).

23.3.3.5 Zero-sized arrays [array.zero]

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 non-throwing exception specification.

23.3.3.6 Array creation functions [array.creation]

template<class T, size_t N> constexpr array<remove_cv_t<T>, N> to_array(T (&a)[N]);

Mandates: is_array_v<T> is false andis_constructible_v<remove_cv_t<T>, T&> is true.

Preconditions: T meets the Cpp17CopyConstructible requirements.

Returns: {{ a[0], …, a[N - 1] }}.

template<class T, size_t N> constexpr array<remove_cv_t<T>, N> to_array(T (&&a)[N]);

Mandates: is_array_v<T> is false andis_constructible_v<remove_cv_t<T>, T> is true.

Preconditions: T meets the Cpp17MoveConstructible requirements.

Returns: {{ std​::​move(a[0]), …, std​::​move(a[N - 1]) }}.

23.3.3.7 Tuple interface [array.tuple]

template<class T, size_t N> struct tuple_size<array<T, N>> : integral_constant<size_t, N> { };

template<size_t I, class T, size_t N> struct tuple_element<I, array<T, N>> { using type = T;};

template<size_t I, class T, size_t N> constexpr T& get(array<T, N>& a) noexcept;template<size_t I, class T, size_t N> constexpr T&& get(array<T, N>&& a) noexcept;template<size_t I, class T, size_t N> constexpr const T& get(const array<T, N>& a) noexcept;template<size_t I, class T, size_t N> constexpr const T&& get(const array<T, N>&& a) noexcept;

Returns: A reference to the element of a, where indexing is zero-based.