[mdspan.layout.leftpad.obs] (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]

23.7.3.4.8 Class template layout_left_padded​::​mapping [mdspan.layout.leftpad]

23.7.3.4.8.4 Observers [mdspan.layout.leftpad.obs]

constexpr array<index_type, _rank_> strides() const noexcept;

Returns: array<index_type, _rank__>({stride(P_rank)...}).

constexpr index_type required_span_size() const noexcept;

Returns:

• 0 if the multidimensional index space extents_ is empty,
• otherwise, (*this)(extents_.extent(P_rank) - index_type(1)...) + 1.

template<class... Indices> constexpr size_t operator()(Indices... idxs) const noexcept;

Constraints:

• sizeof...(Indices) == rank_ is true.
• (is_convertible_v<Indices, index_type> && ...) is true.
• (is_nothrow_constructible_v<index_type, Indices> && ...) is true.

Preconditions: extents_type​::​index-cast(idxs) is a multidimensional index in extents() ([mdspan.overview]).

Returns: ((static_cast<index_type>(idxs) * stride(P_rank)) + ... + 0).

static constexpr bool is_always_exhaustive() noexcept;

Returns:

• If rank_ equals zero or one, then true;
• otherwise, if neither static-padding-stride nor _first-static-extent_equal dynamic_extent, then static-padding-stride == first-static-extent;
• otherwise, false.

constexpr bool is_exhaustive() const noexcept;

Returns: true if rank_ equals zero or one; otherwise, extents_.extent(0) == stride(1).

constexpr index_type stride(rank_type r) const noexcept;

Preconditions: r is smaller than rank_.

Returns:

• If r equals zero: 1;
• otherwise, if r equals one: stride-1;
• otherwise, the product of stride-1 and all values extents_.extent(k) with k in the range [1, r).

template<class LayoutLeftPaddedMapping> friend constexpr bool operator==(const mapping& x, const LayoutLeftPaddedMapping& y) noexcept;

Constraints:

• is-layout-left-padded-mapping-of<LayoutLeftPaddedMapping>is true.
• LayoutLeftPaddedMapping​::​extents_type​::​rank() == rank_ is true.

Returns: true if x.extents() == y.extents() is true and_rank__ < 2 || x.stride(1) == y.
stride(1) is true.

Otherwise, false.