23 Containers library [containers]

23.7 Views [views]

23.7.3 Multidimensional access [views.multidim]

23.7.3.6 Class template mdspan [mdspan.mdspan]

23.7.3.6.2 Constructors [mdspan.mdspan.cons]

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constexpr mdspan();
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Constraints:
  • (1.1)
    rank_dynamic() > 0 is true.
  • (1.2)
    is_default_constructible_v<data_handle_type> is true.
  • (1.3)
    is_default_constructible_v<mapping_type> is true.
  • (1.4)
    is_default_constructible_v<accessor_type> is true.
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Preconditions: [0, map_.required_span_size()) is an accessible range of ptr_ and acc_ for the values of map_ and acc_ after the invocation of this constructor.
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Effects: Value-initializes ptr_, map_, and acc_.
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template<class... OtherIndexTypes> constexpr explicit mdspan(data_handle_type p, OtherIndexTypes... exts);
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Let N be sizeof...(OtherIndexTypes).
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Constraints:
  • (5.1)
    (is_convertible_v<OtherIndexTypes, index_type> && ...) is true,
  • (5.2)
    (is_nothrow_constructible<index_type, OtherIndexTypes> && ...) is true,
  • (5.3)
    N == rank() || N == rank_dynamic() is true,
  • (5.4)
    is_constructible_v<mapping_type, extents_type> is true, and
  • (5.5)
    is_default_constructible_v<accessor_type> is true.
6
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Preconditions: [0, map_.required_span_size()) is an accessible range of p and acc_ for the values of map_ and acc_ after the invocation of this constructor.
7
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Effects:
  • (7.1)
    Direct-non-list-initializes ptr_ with std​::​move(p),
  • (7.2)
    direct-non-list-initializes map_ with extents_type(static_cast<index_type>(std​::​move(exts​))...), and
  • (7.3)
    value-initializes acc_.
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template<class OtherIndexType, size_t N> constexpr explicit(N != rank_dynamic()) mdspan(data_handle_type p, span<OtherIndexType, N> exts); template<class OtherIndexType, size_t N> constexpr explicit(N != rank_dynamic()) mdspan(data_handle_type p, const array<OtherIndexType, N>& exts);
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Constraints:
  • (8.1)
    is_convertible_v<const OtherIndexType&, index_type> is true,
  • (8.2)
    is_nothrow_constructible_v<index_type, const OtherIndexType&> is true,
  • (8.3)
    N == rank() || N == rank_dynamic() is true,
  • (8.4)
    is_constructible_v<mapping_type, extents_type> is true, and
  • (8.5)
    is_default_constructible_v<accessor_type> is true.
9
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Preconditions: [0, map_.required_span_size()) is an accessible range of p and acc_ for the values of map_ and acc_ after the invocation of this constructor.
10
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Effects:
  • (10.1)
    Direct-non-list-initializes ptr_ with std​::​move(p),
  • (10.2)
    direct-non-list-initializes map_ with extents_type(exts), and
  • (10.3)
    value-initializes acc_.
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constexpr mdspan(data_handle_type p, const extents_type& ext);
11
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Constraints:
  • (11.1)
    is_constructible_v<mapping_type, const extents_type&> is true, and
  • (11.2)
    is_default_constructible_v<accessor_type> is true.
12
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Preconditions: [0, map_.required_span_size()) is an accessible range of p and acc_ for the values of map_ and acc_ after the invocation of this constructor.
13
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Effects:
  • (13.1)
    Direct-non-list-initializes ptr_ with std​::​move(p),
  • (13.2)
    direct-non-list-initializes map_ with ext, and
  • (13.3)
    value-initializes acc_.
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constexpr mdspan(data_handle_type p, const mapping_type& m);
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Constraints: is_default_constructible_v<accessor_type> is true.
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Preconditions: [0, m.required_span_size()) is an accessible range of p and acc_ for the value of acc_ after the invocation of this constructor.
16
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Effects:
  • (16.1)
    Direct-non-list-initializes ptr_ with std​::​move(p),
  • (16.2)
    direct-non-list-initializes map_ with m, and
  • (16.3)
    value-initializes acc_.
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constexpr mdspan(data_handle_type p, const mapping_type& m, const accessor_type& a);
17
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Preconditions: [0, m.required_span_size()) is an accessible range of p and a.
18
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Effects:
  • (18.1)
    Direct-non-list-initializes ptr_ with std​::​move(p),
  • (18.2)
    direct-non-list-initializes map_ with m, and
  • (18.3)
    direct-non-list-initializes acc_ with a.
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template<class OtherElementType, class OtherExtents, class OtherLayoutPolicy, class OtherAccessor> constexpr explicit(see below) mdspan(const mdspan<OtherElementType, OtherExtents, OtherLayoutPolicy, OtherAccessor>& other);
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Constraints:
  • (19.1)
    is_constructible_v<mapping_type, const OtherLayoutPolicy​::​template mapping<Oth-
    erExtents>&>     is true, and
  • (19.2)
    is_constructible_v<accessor_type, const OtherAccessor&> is true.
20
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Mandates:
  • (20.1)
    is_constructible_v<data_handle_type, const OtherAccessor​::​data_handle_type&> is
    true, and
  • (20.2)
    is_constructible_v<extents_type, OtherExtents> is true.
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Preconditions:
  • (21.1)
    For each rank index r of extents_type, static_extent(r) == dynamic_extent || static_extent(r) == other.extent(r) is true.
  • (21.2)
    [0, map_.required_span_size()) is an accessible range of ptr_ and acc_ for values of ptr_, map_, and acc_ after the invocation of this constructor.
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Effects:
  • (22.1)
    Direct-non-list-initializes ptr_ with other.ptr_,
  • (22.2)
    direct-non-list-initializes map_ with other.map_, and
  • (22.3)
    direct-non-list-initializes acc_ with other.acc_.
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Remarks: The expression inside explicit is equivalent to: !is_convertible_v<const OtherLayoutPolicy::template mapping<OtherExtents>&, mapping_type> || !is_convertible_v<const OtherAccessor&, accessor_type>