std::extents<IndexType,Extents...>::extents

`constexpr extents() = default;`	(1)	(since C++23)
`template< class OtherIndexType, std::size_t... OtherExtents > constexpr explicit(/see below/) extents( const std::extents<OtherIndexType, OtherExtents...>& other ) noexcept;`	(2)	(since C++23)
`template< class... OtherIndexTypes > constexpr explicit extents( OtherIndexTypes... exts ) noexcept;`	(3)	(since C++23)
`template< class OtherIndexType, std::size_t N > constexpr explicit(N != rank_dynamic()) extents( std::span<OtherIndexType, N> exts ) noexcept;`	(4)	(since C++23)
`template< class OtherIndexType, std::size_t N > constexpr explicit(N != rank_dynamic()) extents( const std::array<OtherIndexType, N>& exts ) noexcept;`	(5)	(since C++23)

Construct an extents. One can construct extents from just dynamic extents, which are all the values getting stored, or from all the extents with a precondition.

1) Default constructor. Initializes all dynamic extents to zero.

2) Conversion from another extents object. After construction, *this == other is true.

The behavior is undefined if

other.extent(r) != static_extent(r) for any r for which static_extent(r) represents a static extent, or
other.extent(r) is not representable as a value of type IndexType for any rank value r in other.

This overload participates in overload resolution only if

sizeof...(OtherExtents) == rank() is true, and
((OtherExtents == std::dynamic_extent || Extents == std::dynamic_extent || OtherExtents == Extents) && ...) is true.

This constructor is explicit if

((Extents != std::dynamic_extent && OtherExtents == std::dynamic_extent) || ...) is true, or
std::numeric_limits<IndexType>::max() < std::numeric_limits<OtherIndexType>::max() is true.

3) Let N be sizeof...(exts) and exts_arr be std::array<IndexType, N>{static_cast<IndexType>(std::move(exts))...}, equivalent to extents(exts_arr).

This overload participates in overload resolution only if

(std::is_convertible_v<OtherIndexTypes, IndexType> && ...) is true,
(std::is_nothrow_constructible_v<IndexType, OtherIndexTypes> && ...) is true, and
N == rank_dynamic() || N == rank() is true.

The behavior is undefined if

N != rank_dynamic() and exts_arr[r] is not equal to static_extent(r) for any r for which static_extent(r) represents a static extent, or
an element in exts is negative or not representable as a value of type IndexType.

4,5) If N equals rank_dynamic(), for all d in [0, rank_dynamic()), direct-non-list-initializes dynamic-extents[d] with std::as_const(exts[d]). Otherwise, for all d in [0, rank_dynamic()), direct-non-list-initializes dynamic-extents[d] with std::as_const(exts[dynamic-index-inv(d)]).

This overload participates in overload resolution only if

(std::is_convertible_v<const OtherIndexType&, IndexType> && ...) is true,
(std::is_nothrow_constructible_v<IndexType, const OtherIndexType&> && ...) is true, and
N == rank_dynamic() || N == rank() is true.

The behavior is undefined if

N != rank_dynamic() and exts[r] is not equal to static_extent(r) for any r for which static_extent(r) represents a static extent, or
exts[r] is negative or not representable as a value of type IndexType for any rank index r.

Parameters

other	-	another `extents` to convert from
exts	-	represents the extents

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std::extents<IndexType,Extents...>::extents

Parameters

Example

See also