23 Containers library [containers]

23.7 Views [views]

23.7.2 Contiguous access [views.contiguous]

23.7.2.2 Class template span [views.span]

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

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constexpr span() noexcept;
1
#
Constraints: Extent == dynamic_extent || Extent == 0 is true.
2
#
Postconditions: size() == 0 && data() == nullptr.
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template<class It> constexpr explicit(extent != dynamic_extent) span(It first, size_type count);
3
#
Constraints: Let U be remove_reference_t<iter_reference_t<It>>.
  • (3.1)
  • (3.2)
    is_convertible_v<U(*)[], element_type(*)[]> is true.
    [Note 1: 
    The intent is to allow only qualification conversions of the iterator reference type to element_type.
    — end note]
4
#
Preconditions:
5
#
Effects: Initializes data_ with to_address(first) and size_ with count.
6
#
Throws: Nothing.
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template<class It, class End> constexpr explicit(extent != dynamic_extent) span(It first, End last);
7
#
Constraints: Let U be remove_reference_t<iter_reference_t<It>>.
  • (7.1)
    is_convertible_v<U(*)[], element_type(*)[]> is true.
    [Note 2: 
    The intent is to allow only qualification conversions of the iterator reference type to element_type.
    — end note]
  • (7.2)
  • (7.3)
    End satisfies sized_sentinel_for<It>.
  • (7.4)
    is_convertible_v<End, size_t> is false.
8
#
Preconditions:
9
#
Effects: Initializes data_ with to_address(first) and size_ with last - first.
10
#
Throws: When and what last - first throws.
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template<size_t N> constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept; template<class T, size_t N> constexpr span(array<T, N>& arr) noexcept; template<class T, size_t N> constexpr span(const array<T, N>& arr) noexcept;
11
#
Constraints: Let U be remove_pointer_t<decltype(std​::​data(arr))>.
  • (11.1)
    extent == dynamic_extent || N == extent is true, and
  • (11.2)
    is_convertible_v<U(*)[], element_type(*)[]> is true.
    [Note 3: 
    The intent is to allow only qualification conversions of the array element type to element_type.
    — end note]
12
#
Effects: Constructs a span that is a view over the supplied array.
[Note 4: 
type_identity_t affects class template argument deduction.
— end note]
13
#
Postconditions: size() == N && data() == std​::​data(arr) is true.
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template<class R> constexpr explicit(extent != dynamic_extent) span(R&& r);
14
#
Constraints: Let U be remove_reference_t<ranges​::​range_reference_t<R>>.
  • (14.1)
    R satisfies ranges​::​contiguous_range and ranges​::​sized_range.
  • (14.2)
    Either R satisfies ranges​::​borrowed_range or is_const_v<element_type> is true.
  • (14.3)
    remove_cvref_t<R> is not a specialization of span.
  • (14.4)
    remove_cvref_t<R> is not a specialization of array.
  • (14.5)
    is_array_v<remove_cvref_t<R>> is false.
  • (14.6)
    is_convertible_v<U(*)[], element_type(*)[]> is true.
    [Note 5: 
    The intent is to allow only qualification conversions of the range reference type to element_type.
    — end note]
15
#
Preconditions:
16
#
Effects: Initializes data_ with ranges​::​data(r) and size_ with ranges​::​size(r).
17
#
Throws: What and when ranges​::​data(r) and ranges​::​size(r) throw.
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constexpr explicit(extent != dynamic_extent) span(std::initializer_list<value_type> il);
18
#
Constraints: is_const_v<element_type> is true.
19
#
Preconditions: If extent is not equal to dynamic_extent, then il.size() is equal to extent.
20
#
Effects: Initializes data_ with il.begin() and size_ with il.size().
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constexpr span(const span& other) noexcept = default;
21
#
Postconditions: other.size() == size() && other.data() == data().
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template<class OtherElementType, size_t OtherExtent> constexpr explicit(see below) span(const span<OtherElementType, OtherExtent>& s) noexcept;
22
#
Constraints:
  • (22.1)
    extent == dynamic_extent || OtherExtent == dynamic_extent || extent == OtherExtent is true, and
  • (22.2)
    is_convertible_v<OtherElementType(*)[], element_type(*)[]> is true.
    [Note 6: 
    The intent is to allow only qualification conversions of the OtherElementType to element_type.
    — end note]
23
#
Preconditions: If extent is not equal to dynamic_extent, then s.size() is equal to extent.
24
#
Effects: Constructs a span that is a view over the range [s.data(), s.data() + s.size()).
25
#
Postconditions: size() == s.size() && data() == s.data().
26
#
Remarks: The expression inside explicit is equivalent to: extent != dynamic_extent && OtherExtent == dynamic_extent
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constexpr span& operator=(const span& other) noexcept = default;
27
#
Postconditions: size() == other.size() && data() == other.data().
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