[mdspan.layout.rightpad.overview]

namespace std { template<size_t PaddingValue> template<class Extents> class layout_right_padded<PaddingValue>::mapping { public: static constexpr size_t padding_value = PaddingValue; using extents_type = Extents; using index_type = extents_type::index_type; using size_type = extents_type::size_type; using rank_type = extents_type::rank_type; using layout_type = layout_right_padded<PaddingValue>; private: static constexpr size_t rank_ = extents_type::rank(); / exposition only static constexpr size_t last-static-extent = / exposition only extents_type::static_extent(rank_ - 1); / [mdspan.layout.rightpad.expo], exposition-only members static constexpr size_t static-padding-stride = see below; / exposition only public: / [mdspan.layout.rightpad.cons], constructors constexpr mapping() noexcept : mapping(extents_type{}) {} constexpr mapping(const mapping&) noexcept = default; constexpr mapping(const extents_type&); template<class OtherIndexType> constexpr mapping(const extents_type&, OtherIndexType); template<class OtherExtents> constexpr explicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const layout_right::mapping<OtherExtents>&); template<class OtherExtents> constexpr explicit(see below) mapping(const layout_stride::mapping<OtherExtents>&); template<class LayoutRightPaddedMapping> constexpr explicit(see below) mapping(const LayoutRightPaddedMapping&); template<class LayoutLeftPaddedMapping> constexpr explicit(see below) mapping(const LayoutLeftPaddedMapping&) noexcept; constexpr mapping& operator=(const mapping&) noexcept = default; / [mdspan.layout.rightpad.obs], observers constexpr const extents_type& extents() const noexcept { return extents_; } constexpr array<index_type, rank_> strides() const noexcept; constexpr index_type required_span_size() const noexcept; template<class. Indices> constexpr index_type operator()(Indices..) const noexcept; static constexpr bool is_always_unique() noexcept { return true; } static constexpr bool is_always_exhaustive() noexcept; static constexpr bool is_always_strided() noexcept { return true; } static constexpr bool is_unique() noexcept { return true; } constexpr bool is_exhaustive() const noexcept; static constexpr bool is_strided() noexcept { return true; } constexpr index_type stride(rank_type) const noexcept; template<class LayoutRightPaddedMapping> friend constexpr bool operator=(const mapping&, const LayoutRightPaddedMapping&) noexcept; private: / [mdspan.layout.rightpad.expo], exposition-only members index_type stride-rm2 = static-padding-stride; / exposition only extents_type extents_{}; / exposition only / [mdspan.sub.map], submdspan mapping specialization template<class. SliceSpecifiers> constexpr auto submdspan-mapping-impl(SliceSpecifiers..) const / exposition only -> see below; template<class. SliceSpecifiers> friend constexpr auto submdspan_mapping(const mapping& src, SliceSpecifiers.. slices) { return src.submdspan-mapping-impl(slices..); } }; }

If Extents is not a specialization of extents, then the program is ill-formed.

layout_right_padded::mapping<E> is a trivially copyable type that models regular for each E.

Throughout [mdspan.layout.rightpad], let P_rank be the following size rank_ parameter pack of size_t values:

(4.1)
the empty parameter pack, if rank_ equals zero;
(4.2)
otherwise, 0zu, if rank_ equals one;
(4.3)
otherwise, the parameter pack 0zu, 1zu, …, rank_- 1.

Mandates:

(5.1)
If rank_dynamic() == 0 is true, then the size of the multidimensional index space Extents() is representable as a value of type index_type.
(5.2)
If padding_value is not equal to dynamic_extent, then padding_value is representable as a value of type index_type.
(5.3)
If
- (5.3.1)
  rank_ is greater than one,
- (5.3.2)
  padding_value does not equal dynamic_extent, and
- (5.3.3)
  last-static-extent does not equal dynamic_extent,
then LEAST-MULTIPLE-AT-LEAST(padding_value, last-static-extent) is representable as a value of type size_t, and is representable as a value of type index_type.
(5.4)
If
- (5.4.1)
  rank_ is greater than one,
- (5.4.2)
  padding_value does not equal dynamic_extent, and
- (5.4.3)
  extents_type::static_extent(k) does not equal dynamic_extent for all k in the range [0, rank_),
then the product of LEAST-MULTIPLE-AT-LEAST(padding_value, ext.static_extent(rank_ - 1) and all values ext.static_extent(k) with k in the range of [0, rank_ - 1) is representable as a value of type size_t, and is representable as a value of type index_type.