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<title>Issue 3711: Missing preconditions for slide_view constructor</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#C++23">C++23</a> status.</em></p>
<h3 id="3711"><a href="lwg-defects.html#3711">3711</a>. Missing preconditions for <code>slide_view</code> constructor</h3>
<p><b>Section:</b> 25.7.30.2 <a href="https://wg21.link/range.slide.view">[range.slide.view]</a> <b>Status:</b> <a href="lwg-active.html#C++23">C++23</a>
 <b>Submitter:</b> Hewill Kang <b>Opened:</b> 2022-06-10 <b>Last modified:</b> 2023-11-22</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#range.slide.view">issues</a> in [range.slide.view].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++23">C++23</a> status.</p>
<p><b>Discussion:</b></p>
<p>
It doesn't make sense for <code>slide_view</code> when <code>n</code> is not positive, 
we should therefore add a precondition for its constructor just like we did for 
<code>chunk_view</code>.
<p/>
<i>Daniel:</i>
<p/>
Indeed the accepted paper describes the intention in
<a href="https://wg21.link/p2442r1#slide">P2442R1 Section 4.2</a> by saying that 
"It is a precondition that <code>N</code> is positive" in the design wording
but omitted to add a normative precondition in the proposed wording.
</p>

<p><i>[2022-06-21; Reflector poll]</i></p>

<p>
Set status to Tentatively Ready after six votes in favour during reflector poll.
</p>

<p><i>[2022-07-15; LWG telecon: move to Ready]</i></p>


<p><i>[2022-07-25 Approved at July 2022 virtual plenary. Status changed: Ready &rarr; WP.]</i></p>



<p id="res-3711"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N4910" title=" Working Draft, Standard for Programming Language C++">N4910</a>.
</p>

<ol>
<li><p>Modify 25.7.30.2 <a href="https://wg21.link/range.slide.view">[range.slide.view]</a> as indicated:</p>

<blockquote>
<pre>
constexpr explicit slide_view(V base, range_difference_t&lt;V&gt; n);
</pre>
<blockquote>
<p>
<ins>-?- <i>Preconditions</i>: <code>n &gt; 0</code> is <code>true</code>.</ins>
<p/>
-1- <i>Effects</i>: Initializes <code><i>base_</i></code> with <code>std::move(base)</code> and <code><i>n_</i></code> with <code>n</code>.
</p>
</blockquote>
</blockquote>
</li>

</ol>





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