[mdspan.extents.cons] (original) (raw)

23 Containers library [containers]

23.7 Views [views]

23.7.3 Multidimensional access [views.multidim]

23.7.3.3 Class template extents [mdspan.extents]

23.7.3.3.3 Constructors [mdspan.extents.cons]

template<class OtherIndexType, size_t... OtherExtents> constexpr explicit(_see below_) extents(const extents<OtherIndexType, OtherExtents...>& other) noexcept;

Constraints:

• sizeof...(OtherExtents) == rank() is true.
• ((OtherExtents == dynamic_extent || Extents == dynamic_extent || OtherExtents ==
  Extents) && ...) is true.

Preconditions:

• other.extent(r) equals for each r for which is a static extent, and
• either
  • sizeof...(OtherExtents) is zero, or
  • other.extent(r) is representable as a value of type index_type for every rank index r of other.

Postconditions: *this == other is true.

Remarks: The expression inside explicit is equivalent to:(((Extents != dynamic_extent) && (OtherExtents == dynamic_extent)) || ... ) || (numeric_limits<index_type>::max() < numeric_limits<OtherIndexType>::max())

template<class... OtherIndexTypes> constexpr explicit extents(OtherIndexTypes... exts) noexcept;

Let N be sizeof...(OtherIndexTypes), and let exts_arr bearray<index_type, N>{static_cast<
index_type>(std​::​move(exts))...}.

Constraints:

• (is_convertible_v<OtherIndexTypes, index_type> && ...) is true,
• (is_nothrow_constructible_v<index_type, OtherIndexTypes> && ...) is true, and
• N == rank_dynamic() || N == rank() is true.
  [Note 1:
  One can construct extents from just dynamic extents, which are all the values getting stored, or from all the extents with a precondition.
  — _end note_]

Preconditions:

• If N != rank_dynamic() is true,exts_arr[r] equals for each r for which is a static extent, and
• either
  • sizeof...(exts) == 0 is true, or
  • each element of exts is representable as a nonnegative value of type index_type.

Postconditions: *this == extents(exts_arr) is true.

template<class OtherIndexType, size_t N> constexpr explicit(N != rank_dynamic()) extents(span<OtherIndexType, N> exts) noexcept;template<class OtherIndexType, size_t N> constexpr explicit(N != rank_dynamic()) extents(const array<OtherIndexType, N>& exts) noexcept;

Constraints:

• is_convertible_v<const OtherIndexType&, index_type> is true,
• is_nothrow_constructible_v<index_type, const OtherIndexType&> is true, and
• N == rank_dynamic() || N == rank() is true.

Preconditions:

• If N != rank_dynamic() is true,exts[r] equals for each r for which is a static extent, and
• either
  • N is zero, or
  • exts[r] is representable as a nonnegative value of type index_type for every rank index r.

Effects:

• If N equals rank_dynamic(), for all d in the range [0, rank_dynamic()), direct-non-list-initializes _dynamic-extents_[d]with as_const(exts[d]).
• Otherwise, for all d in the range [0, rank_dynamic()), direct-non-list-initializes _dynamic-extents_[d]with as_const(exts[dynamic-index-inv(d)]).

template<class... Integrals> explicit extents(Integrals...) -> _see below_;

Constraints: (is_convertible_v<Integrals, size_t> && ...) is true.