23 Containers library [containers]

The following elements apply to all functions in [mdspan.sub.map].

Constraints: sizeof...(SpliceSpecifiers) equals extents_type​::​rank().

Mandates: For each rank index k of extents(), SliceSpecifiers...[k] is a valid submdspan slice type for the $k^{\text{th}}$ extent of Extents.

Preconditions: For each rank index k of extents(), slices...[k] is a valid slice for the $k^{\text{th}}$ extent of extents().

Let sub_ext be the result of submdspan_extents(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 $\rho {}^{\text{th}}$ 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...).