[mdspan.layout.left.overview] (original) (raw)

23 Containers library [containers]

23.7 Views [views]

23.7.3 Multidimensional access [views.multidim]

23.7.3.4 Layout mapping [mdspan.layout]

23.7.3.4.5 Class template layout_left​::​mapping [mdspan.layout.left]

23.7.3.4.5.1 Overview [mdspan.layout.left.overview]

layout_left provides a layout mapping where the leftmost extent has stride 1, and strides increase left-to-right as the product of extents.

namespace std { template<class Extents> class layout_left::mapping { public: 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_left;constexpr mapping() noexcept = default;constexpr mapping(const mapping&) noexcept = default;constexpr mapping(const extents_type&) noexcept;template<class OtherExtents> constexpr explicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const mapping<OtherExtents>&) noexcept;template<class OtherExtents> constexpr explicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const layout_right::mapping<OtherExtents>&) noexcept;template<class LayoutLeftPaddedMapping> constexpr explicit(!is_convertible_v<typename LayoutLeftPaddedMapping::extents_type, extents_type>) mapping(const LayoutLeftPaddedMapping&) noexcept;template<class OtherExtents> constexpr explicit(see below) mapping(const layout_stride::mapping<OtherExtents>&);constexpr mapping& operator=(const mapping&) noexcept = default;constexpr const extents_type& extents() const noexcept { return extents_; } 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 { return true; } static constexpr bool is_always_strided() noexcept { return true; } static constexpr bool is_unique() noexcept { return true; } static constexpr bool is_exhaustive() noexcept { return true; } static constexpr bool is_strided() noexcept { return true; } constexpr index_type stride(rank_type) const noexcept;template<class OtherExtents> friend constexpr bool operator==(const mapping&, const mapping<OtherExtents>&) noexcept;private: extents_type extents_{}; template<class... SliceSpecifiers> constexpr auto submdspan-mapping-impl(SliceSpecifiers...) const -> 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_left​::​mapping<E> is a trivially copyable type that models regular for each E.

Mandates: If Extents​::​rank_dynamic() == 0 is true, then the size of the multidimensional index space Extents()is representable as a value of type typename Extents​::​index_type.