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New issue for US 152-243: Rename submdspan_extents and submdspan_canonicalize_slices #537

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New issue for US 152-243: Rename submdspan_extents and submdspan_canonicalize_slices #537

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116 changes: 116 additions & 0 deletions xml/issue4487.xml
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<?xml version='1.0' encoding='utf-8' standalone='no'?>
<!DOCTYPE issue SYSTEM "lwg-issue.dtd">

<issue num="4487" status="New">
<title>Rename `submdspan_extents` and `submdspan_canonicalize_slices`</title>
<section><sref ref="[mdspan.sub]"/></section>
<submitter>Tomasz Kamiński</submitter>
<date>16 Dec 2025</date>
<priority>99</priority>

<discussion>
<b>Addresses <a href="https://github.com/cplusplus/nbballot/issues/815">US 152-243</a>
and <a href="https://github.com/cplusplus/nbballot/issues/817">PL-008</a>.</b>

<p>Rename `submdspan_extents` to `subextents` and `submdspan_canonicalize_slices` to `canonical_slices`.</p>
</discussion>

<resolution>
<p>
This wording is relative to <paper num="N5032"/>.
</p>

<ol>
<li><p>Modify <sref ref="[mdspan.syn]"/> as follows:</p>

<blockquote>
<pre>
// <sref ref="[mdspan.sub]"/>, submdspan creation
template&lt;class OffsetType, class LengthType, class StrideType&gt;
struct strided_slice;

template&lt;class LayoutMapping&gt;
struct submdspan_mapping_result;

struct full_extent_t { explicit full_extent_t() = default; };
inline constexpr full_extent_t full_extent{};

template&lt;class IndexType, size_t... Extents, class... SliceSpecifiers&gt;
constexpr auto sub<del>mdspan_</del>extents(const extents&lt;IndexType, Extents...&gt;&amp;, SliceSpecifiers...);

// <sref ref="[mdspan.sub.canonical]"/>, submdspan slice canonicalization
template&lt;class IndexType, size_t... Extents, class... Slices&gt;
constexpr auto <del>submdspan_canonicalize</del><ins>canonical</ins>_slices(const extents&lt;IndexType, Extents...&gt;&amp; src,
Slices... slices);
</pre>
</blockquote>
</li>

<li><p>Modify <sref ref="[mdspan.sub.canonical]"/> as follows:</p>

<blockquote>
<h4>`submdspan` slice canonicalization</h4>
<pre>
template&lt;class IndexType, size_t... Extents, class... Slices&gt;
constexpr auto <del>submdspan_canonicalize</del><ins>canonical</ins>_slices(const extents&lt;IndexType, Extents...&gt;&amp; src,
Slices... slices);
</pre>
</blockquote>
</li>

<li><p>Modify <sref ref="[mdspan.sub.extents]"/> as follows:</p>

<blockquote>
<h4><sref ref="[mdspan.sub.extents]"/> <tt>sub<del>mdspan_</del>extents</tt> function</h4>

<pre>
template&lt;class IndexType, size_t... Extents, class... SliceSpecifiers&gt;
constexpr auto sub<del>mdspan_</del>extents(const extents&lt;IndexType, Extents...&gt;&amp; src,
SliceSpecifiers... raw_slices);
</pre>
<blockquote>
<p>-1- Let `slices` be the pack introduced by the following declaration:
<pre>
auto [...slices] = <del>submdspan_canonicalize</del><ins>canonical</ins>_slices(src, raw_slices...)
</pre></p>
</blockquote>
</blockquote>
</li>

<li><p>Modify <sref ref="[mdspan.sub.map.sliceable]"/> as follows:</p>
<blockquote>
<blockquote>
<p>-5- <i>Returns</i>: An object `smr` of type `SMR` such that
<ul>
<li>-5.1- <tt>smr.mapping.extents() == sub<del>mdspan_</del>extents(m.extents(), valid_slices...)</tt> is `true`; and</li>
<li>-5.2- [&hellip;]</li>
</ul></p>
</blockquote>
</blockquote>
</li>

<li><p>Modify <sref ref="[mdspan.sub.map.common]"/> as follows:</p>
<blockquote>
<blockquote>
<p>-5- Let `sub_ext` be the result of <tt>sub<del>mdspan_</del>extents(extents(), slices...)</tt>
and let `SubExtents` be `decltype(sub_ext)`.</p>
</blockquote>
</blockquote>
</li>

<li><p>Modify <sref ref="[mdspan.sub.sub]"/> as follows:</p>
<blockquote>
<blockquote>
<p>-2- Let `slices` be the pack introduced by the following declaration:
<pre>
auto [...slices] = <del>submdspan_canonicalize</del><ins>canonical</ins>_slices(src, raw_slices...)
</pre></p>
</blockquote>
</blockquote>
</li>

</ol>

</resolution>

</issue>