23 Containers library [containers]

23.7 Views [views]

23.7.3 Multidimensional access [views.multidim]

23.7.3.7 submdspan [mdspan.sub]

23.7.3.7.6 Specializations of submdspan_mapping [mdspan.sub.map]

23.7.3.7.6.1 Common [mdspan.sub.map.common]

1
#
The following elements apply to all functions in [mdspan.sub.map].
2
#
Constraints: sizeof...(slices) equals extents_type​::​rank().
3
#
Mandates: For each rank index k of extents(), exactly one of the following is true:
4
#
Preconditions: For each rank index k of extents(), all of the following are true:
  • (4.1)
    if is a specialization of strided_slice, .extent is equal to zero or .stride is greater than zero; and
  • (4.2)
    0  ≤ first_<index_type, k>(slices...)
    0  ≤ last_<k>(extents(), slices...)
    0  ≤ extents().extent(k)
5
#
Let sub_ext be the result of submdspan_extents(extents(), slices...) and let SubExtents be decltype(sub_ext).
6
#
Let sub_strides be an array<SubExtents​::​index_type, SubExtents​::​rank()> such that for each rank index k of extents() for which map-rank[k] is not dynamic_extent, sub_strides[map-rank[k]] equals:
  • (6.1)
    stride(k) * de-ice(.stride) if is a specialization of strided_slice and .stride < .extent is true;
  • (6.2)
    otherwise, stride(k).
7
#
Let P be a parameter pack such that is_same_v<make_index_sequence<rank()>, index_sequence<P...>> is true.
8
#
If first_<index_type, k>(slices...) equals extents().extent(k) for any rank index k of extents(), then let offset be a value of type size_t equal to (*this).required_span_size().
Otherwise, let offset be a value of type size_t equal to (*this)(first_<index_type, P>(slices...)...).
9
#
Given a layout mapping type M, a type S is a unit-stride slice for M if