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<title>Issue 3110: Contiguous Iterators should always be Random-Access</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#Resolved">Resolved</a> status.</em></p>
<h3 id="3110"><a href="lwg-defects.html#3110">3110</a>. Contiguous Iterators should always be Random-Access</h3>
<p><b>Section:</b> 24.3.1 <a href="https://wg21.link/iterator.requirements.general">[iterator.requirements.general]</a> <b>Status:</b> <a href="lwg-active.html#Resolved">Resolved</a>
 <b>Submitter:</b> Marc Aldorasi <b>Opened:</b> 2018-05-07 <b>Last modified:</b> 2020-09-06</p>
<p><b>Priority: </b>3
</p>
<p><b>View all other</b> <a href="lwg-index.html#iterator.requirements.general">issues</a> in [iterator.requirements.general].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Resolved">Resolved</a> status.</p>
<p><b>Discussion:</b></p>
<p>
In [iterator.requirements.general] paragraph 6, contiguous iterators are defined in terms of general iterators, 
not random-access iterators. Since the defining expressions require random-access and the original paper's 
introduction describes contiguous iterators as a refinement of random-access iterators, contiguous iterators 
should be defined in terms of random-access iterators.
</p>

<p><i>[2018-06-18 after reflector discussion]</i></p>

<p>Priority set to 3</p>

<p><strong>Previous resolution [SUPERSEDED]:</strong></p>
<blockquote class="note">
<p>
This wording is relative to <a href="https://wg21.link/n4741">N4741</a>.
</p>

<ol>
<li>
<p>Edit 24.3.1 <a href="https://wg21.link/iterator.requirements.general">[iterator.requirements.general]</a> as indicated:</p>
<blockquote>
<p>
-6- <ins>Random-access i</ins><del>I</del>terators that further satisfy the requirement that, for integral values 
<code>n</code> and dereferenceable iterator values <code>a</code> and <code>(a + n)</code>, <code>*(a + n)</code> is equivalent to 
<code>*(addressof(*a) + n)</code>, are called <i>contiguous iterators</i>. [<i>Note:</i> For example, the type "pointer to 
<code>int</code>" is a contiguous iterator, but <code>reverse_iterator&lt;int *&gt;</code> is not. For a valid iterator 
range <code>[a, b)</code> with dereferenceable a, the corresponding range denoted by pointers is <code>[addressof(*a), 
addressof(*a) + (b - a))</code>; <code>b</code> might not be dereferenceable. &mdash; <i>end note</i>] 
</p>
</blockquote>
</li>
</ol>
</blockquote>

<p><i>[2020-05-03 Reflector discussion]</i></p>

<p>
Resolved by <a href="https://wg21.link/p0894r4">P0894R4</a>.
</p>


<p><b>Rationale:</b></p>
Resolved by <a href="https://wg21.link/p0894r4">P0894R4</a>


<p id="res-3110"><b>Proposed resolution:</b></p>





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