21 Containers library [containers]

21.7 Views [views]

21.7.3 Class template span [views.span]

21.7.3.2 Constructors, copy, and assignment [span.cons]

constexpr span() noexcept;

Ensures: size() == 0 && data() == nullptr.

Remarks: This constructor shall not participate in overload resolution unless Extent <= 0 is true.

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constexpr span(pointer ptr, index_type count);

Requires: [ptr, ptr + count) shall be a valid range.

If extent is not equal to dynamic_extent, then count shall be equal to extent.

Effects: Constructs a span that is a view over the range [ptr, ptr + count).

Ensures: size() == count && data() == ptr.

Throws: Nothing.

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constexpr span(pointer first, pointer last);

Requires: [first, last) shall be a valid range.

If extent is not equal to dynamic_extent, then last - first shall be equal to extent.

Effects: Constructs a span that is a view over the range [first, last).

Ensures: size() == last - first && data() == first.

Throws: Nothing.

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template<size_t N> constexpr span(element_type (&arr)[N]) noexcept;
template<size_t N> constexpr span(array<value_type, N>& arr) noexcept;
template<size_t N> constexpr span(const array<value_type, N>& arr) noexcept;

Effects: Constructs a span that is a view over the supplied array.

Ensures: size() == N && data() == data(arr).

Remarks: These constructors shall not participate in overload resolution unless:

(13.1)
extent == dynamic_extent || N == extent is true, and
(13.2)
remove_pointer_t<decltype(data(arr))>(*)[] is convertible to ElementType(*)[].

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template<class Container> constexpr span(Container& cont);
template<class Container> constexpr span(const Container& cont);

Requires: [data(cont), data(cont) + size(cont)) shall be a valid range.

If extent is not equal to dynamic_extent, then size(cont) shall be equal to extent.

Effects: Constructs a span that is a view over the range [data(cont), data(cont) + size(cont)).

Ensures: size() == size(cont) && data() == data(cont).

Throws: What and when data(cont) and size(cont) throw.

Remarks: These constructors shall not participate in overload resolution unless:

(18.1)
Container is not a specialization of span,
(18.2)
Container is not a specialization of array,
(18.3)
is_array_v<Container> is false,
(18.4)
data(cont) and size(cont) are both well-formed, and
(18.5)
remove_pointer_t<decltype(data(cont))>(*)[] is convertible to ElementType(*)[].

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constexpr span(const span& other) noexcept = default;

Ensures: other.size() == size() && other.data() == data().

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template<class OtherElementType, ptrdiff_t OtherExtent>
  constexpr span(const span<OtherElementType, OtherExtent>& s) noexcept;

Effects: Constructs a span that is a view over the range [s.data(), s.data() + s.size()).

Ensures: size() == s.size() && data() == s.data().

Remarks: This constructor shall not participate in overload resolution unless:

(22.1)
Extent == dynamic_extent || Extent == OtherExtent is true, and
(22.2)
OtherElementType(*)[] is convertible to ElementType(*)[].

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constexpr span& operator=(const span& other) noexcept = default;

Ensures: size() == other.size() && data() == other.data().