23 Containers library [containers]

23.7 Views [views]

23.7.3 Multidimensional access [views.multidim]

23.7.3.7 submdspan [mdspan.sub]

23.7.3.7.7 Specializations of submdspan_mapping [mdspan.sub.map]

23.7.3.7.7.6 layout_left_padded specialization of submdspan_mapping [mdspan.sub.map.leftpad]

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template<class Extents> template<class... SliceSpecifiers> constexpr auto layout_left_padded::mapping<Extents>::submdspan-mapping-impl( SliceSpecifiers... slices) const -> see below;
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Returns:
  • (1.1)
    submdspan_mapping_result{*this, 0}, if Extents​::​rank() == 0 is true;
  • (1.2)
    otherwise, submdspan_mapping_result{layout_left​::​mapping(sub_ext), offset}, if rank_ == 1 is true or SubExtents​::​rank() == 0 is true;
  • (1.3)
    otherwise, submdspan_mapping_result{layout_left​::​mapping(sub_ext), offset}, if
    • (1.3.1)
      SubExtents​::​rank() == 1 is true and
    • (1.3.2)
      SliceSpecifiers...[0] is a unit-stride slice type;
  • (1.4)
    otherwise, submdspan_mapping_result{layout_left_padded<S_static>::mapping(sub_ext, stride(u + 1)), offset} if for a value u for which u + 1 is the smallest value p larger than zero for which SliceSpecifiers​...[​p] is a unit-stride slice type, the following conditions are met:
    • (1.4.1)
      SliceSpecifiers...[0] is a unit-stride slice type; and
    • (1.4.2)
      for each k in the range [u + 1, u + SubExtents​::​rank() - 1), SliceSpecifiers...[k] denotes full_extent_t; and
    • (1.4.3)
      for k equal to u + SubExtents​::​rank() - 1, SliceSpecifiers...[k] is a unit-stride slice type;
    where S_static is:
    • (1.4.4)
      dynamic_extent, if static-padding-stride is dynamic_extent or static_extent(k) is dynamic_extent for any k in the range [1, u + 1),
    • (1.4.5)
      otherwise, the product of static-padding-stride and all values static_extent(k) for k in the range [1, u + 1);
  • (1.5)
    otherwise, submdspan_mapping_result{layout_stride::mapping(sub_ext, sub_strides), offset}