[mdspan.sub.sub] Fix submdspan slice canonicalization#8996
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tkoeppe merged 1 commit intoMay 12, 2026
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Two integration errors in the Let clause introduced by P3663R3: - the function parameter pack is named "slices", but the Let clause references an undefined "raw_slices"; rename the parameter to match subextents (mdspan.sub.extents); - src is an mdspan but canonical_slices takes an extents object; pass src.extents() instead of src.
eisenwave
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jwakely
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May 12, 2026
| constexpr auto submdspan( | ||
| const mdspan<ElementType, Extents, LayoutPolicy, AccessorPolicy>& src, | ||
| SliceSpecifiers... slices) -> @\seebelow@; | ||
| SliceSpecifiers... raw_slices) -> @\seebelow@; |
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This was just a misapplication of the paper. https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p3663r3.html#change-mdspan.sub.sub-submdspan-function-template said to change this.
| constexpr auto submdspan( | ||
| const mdspan<ElementType, Extents, LayoutPolicy, AccessorPolicy>& src, | ||
| SliceSpecifiers... slices) -> @\seebelow@; | ||
| SliceSpecifiers... raw_slices) -> @\seebelow@; |
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This should have been changed by the paper, to match the change to [mdspan.sub.sub] in the paper.
| Let \tcode{slices} be the pack introduced by the following declaration: | ||
| \begin{codeblock} | ||
| auto [...slices] = canonical_slices(src, raw_slices...); | ||
| auto [...slices] = canonical_slices(src.extents(), raw_slices...); |
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Two integration errors in
submdspan's slice canonicalization Let clause introduced by P3663R3:slices, but the Let clause references an undefinedraw_slices; rename the parameter to matchsubextents([mdspan.sub.extents]).srcis anmdspanbutcanonical_slicestakes anextentsobject ([mdspan.sub.canonical]); passsrc.extents()instead ofsrc.