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std::extents<IndexType,Extents...>::extents - cppreference.com

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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

Example

See also