[mdspan.sub.map.common]

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

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

Let sub_ext be the result of submdspan_extents(), slices..) and let SubExtents be decltype(sub_ext).

Let sub_strides be an array<SubExtents::index_type, SubExtents::rank()> such that for each rank index k of extents() for which the type of slices..[k] is not a collapsing slice type, sub_strides[MAP_RANK(slices,k)] equals:

(6.1)
stride(k) * s.stride if the type of s is a specialization of strided_slice and s.stride < s.extent is true, where s is slices..[k];
(6.2)
otherwise, stride(k).

Let ls be a pack of values of index_type, where the

ρ {th element equals the lower bound of the submdspan slice range of slices . . [ρ] for extent ρ of extents () .}^{th element equals the lower bound of the submdspan slice range of slices . . [ρ] for extent ρ of extents () .}

If ls..[k] equals extents().extent(k) for any rank index k of extents(), then let offset be a value of type size_t equal to required_span_size().

Otherwise, let offset be a value of type size_t equal to operator()(ls..).