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<title>Issue 3946: The definition of const_iterator_t should be reworked</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#WP">WP</a> status.</em></p>
<h3 id="3946"><a href="lwg-defects.html#3946">3946</a>. The definition of <code>const_iterator_t</code> should be reworked</h3>
<p><b>Section:</b> 25.2 <a href="https://wg21.link/ranges.syn">[ranges.syn]</a> <b>Status:</b> <a href="lwg-active.html#WP">WP</a>
 <b>Submitter:</b> Christopher Di Bella <b>Opened:</b> 2023-06-13 <b>Last modified:</b> 2023-11-22</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#ranges.syn">active issues</a> in [ranges.syn].</p>
<p><b>View all other</b> <a href="lwg-index.html#ranges.syn">issues</a> in [ranges.syn].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#WP">WP</a> status.</p>
<p><b>Discussion:</b></p>
<p>
During the reflector discussion of <a href="https://wg21.link/P2836" title=" std::basic_const_iterator should follow its underlying type's convertibility">P2836</a>, consensus was reached that <code>const_iterator_t&lt;R&gt;</code> 
doesn't necessarily provide the same type as <code>decltype(ranges::cbegin(r))</code>, and that it should be changed to 
the proposed resolution below so that they're consistent.
</p>

<p><i>[Varna 2023-06-14; Move to Ready]</i></p>

<p><i>[2023-11-11 Approved at November 2023 meeting in Kona. Status changed: Voting &rarr; WP.]</i></p>



<p id="res-3946"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N4950" title=" Working Draft, Standard for Programming Language C++">N4950</a>.
</p>

<ol>
<li><p>Modify 25.2 <a href="https://wg21.link/ranges.syn">[ranges.syn]</a>, header <code>&lt;ranges&gt;</code> synopsis, as indicated:</p>

<blockquote>
<pre>
[&hellip;]
template&lt;range R&gt;
  using const_iterator_t = <ins>decltype(ranges::cbegin(declval&lt;R&amp;&gt;()))</ins><del>const_iterator&lt;iterator_t&lt;R&gt;&gt;</del>; // <i>freestanding</i>
template&lt;range R&gt;
  using const_sentinel_t = <ins>decltype(ranges::cend(declval&lt;R&amp;&gt;()))</ins><del>const_sentinel&lt;sentinel_t&lt;R&gt;&gt;</del>;   // <i>freestanding</i>
[&hellip;]
</pre>
</blockquote>
</li>

</ol>





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