[mdspan.sub.sub]

🔗

template<class ElementType, class Extents, class LayoutPolicy,
         class AccessorPolicy, class. SliceSpecifiers>
  constexpr auto submdspan(
    const mdspan<ElementType, Extents, LayoutPolicy, AccessorPolicy>& src,
    SliceSpecifiers.. slices) -> see below;

Let slices be the pack introduced by the following declaration: auto [.slices] = submdspan_canonicalize_slices(src, raw_slices..);

Let sub_map_offset be the result of submdspan_mapping(src.mapping(), slices..).

[Note 1:

This invocation of submdspan_mapping selects a function call via overload resolution on a candidate set that includes the lookup set found by argument-dependent lookup ([basic.lookup.argdep]).

— end note]

Mandates: For each rank index k of src:

(5.1)
SliceSpecifiers..[k] is a submdspan slice type for index_type, and
(5.2)
decltype(slices..[k]) is a valid submdspan slice type for the ${k th extent of Extents .}^{th extent of Extents .}$

Preconditions: For each rank index k of src.extents(), slices..[k] is a valid submdspan slice for the

{k th extent of src . extents () .}^{th extent of src . extents () .}

Effects: Equivalent to: auto sub_map_result = submdspan_mapping(src.mapping(), slices..); return mdspan(src.accessor().offset(src.data_handle(), sub_map_result.offset), sub_map_result.mapping, typename AccessorPolicy::offset_policy(src.accessor();

[Example 1:

Given a rank-3 mdspan grid3d representing a three-dimensional grid of regularly spaced points in a rectangular prism, the function zero_surface sets all elements on the surface of the 3-dimensional shape to zero.

It does so by reusing a function zero_2d that takes a rank-2 mdspan.

/ zero out all elements in an mdspan template<class T, class E, class L, class A> void zero_2d(mdspan<T, E, L, A> a) { static_assert(a.rank() == 2); for (int i = 0; i < a.extent(0); i++) for (int j = 0; j < a.extent(1); j++) a[i, j] = 0; } / zero out just the surface template<class T, class E, class L, class A> void zero_surface(mdspan<T, E, L, A> grid3d) { static_assert(grid3d.rank() == 3); zero_2d(submdspan(grid3d, 0, full_extent, full_extent)); zero_2d(submdspan(grid3d, full_extent, 0, full_extent)); zero_2d(submdspan(grid3d, full_extent, full_extent, 0); zero_2d(submdspan(grid3d, grid3d.extent(0) - 1, full_extent, full_extent)); zero_2d(submdspan(grid3d, full_extent, grid3d.extent(1) - 1, full_extent)); zero_2d(submdspan(grid3d, full_extent, full_extent, grid3d.extent(2) - 1); } — end example]

23 Containers library [containers]

23.7 Views [views]

23.7.3 Multidimensional access [views.multidim]

23.7.3.7 submdspan [mdspan.sub]

23.7.3.7.8 submdspan function template [mdspan.sub.sub]