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<title>Issue 2922: The *_constant&lt;&gt; templates do not make use of template&lt;auto&gt;</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#LEWG">LEWG</a> status.</em></p>
<h3 id="2922"><a href="lwg-active.html#2922">2922</a>. The <code>*_constant&lt;&gt;</code> templates do not make use of <code>template&lt;auto&gt;</code></h3>
<p><b>Section:</b> 21.3.3 <a href="https://wg21.link/meta.type.synop">[meta.type.synop]</a> <b>Status:</b> <a href="lwg-active.html#LEWG">LEWG</a>
 <b>Submitter:</b> United States <b>Opened:</b> 2017-02-03 <b>Last modified:</b> 2017-07-15</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#meta.type.synop">active issues</a> in [meta.type.synop].</p>
<p><b>View all other</b> <a href="lwg-index.html#meta.type.synop">issues</a> in [meta.type.synop].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#LEWG">LEWG</a> status.</p>
<p><b>Discussion:</b></p>
<b>Addresses US 171</b>

<p>The <code>*_constant&lt;&gt;</code> templates (including the proposed addition, <code>bool_constant&lt;&gt;</code>) do 
not make use of the new <code>template&lt;auto&gt;</code> feature.</p>

<p>Proposed change: Add a <code>constant&lt;&gt;</code> (subject to bikeshedding) template which uses <code>template&lt;auto&gt;</code>. </p>
<p>Define <code>integral_constant&lt;&gt;</code> as <code>using integral_constant&lt;T, V&gt; = constant&lt;T(V)&gt;</code> or <code>integral_constant&lt;T, V&gt; = constant&lt;V&gt;</code>.</p>
<p>Either remove <code>bool_constant</code>, define it as using <code>bool_constant = constant&lt;bool(B)&gt;</code> or 
<code>using bool_constant = constant&lt;B&gt;</code>.</p>

<p><i>[2017-03-03, Kona, LEWG]</i></p>

<p>
Straw polls:
</p>
<table border="1">
<caption>Name:</caption>
<tr style="text-align: left">
<td style="width:70%"><code>constant</code></td><td style="width:10%">3</td></tr>
<tr style="text-align: left">
<td><code>numeric_constant</code></td><td>8</td></tr>
<tr style="text-align: left">
<td><code>static_constant</code></td><td>1</td></tr>
<tr style="text-align: left">
<td><code>scalar_constant</code></td><td>7</td></tr>
<tr style="text-align: left">
<td><code>integer_constant</code> (Over LWG's dead body)</td><td>1</td></tr>
<tr style="text-align: left">
<td><code>auto_constant</code></td><td>4</td></tr>
<tr style="text-align: left">
<td><code>integral_c</code></td><td>7</td></tr>
<tr style="text-align: left">
<td><code>int_</code></td><td>0</td></tr>
<tr style="text-align: left">
<td colspan="2"><code>&#x200b;</code></td></tr>
<tr style="text-align: left">
<td><code>scalar_constant</code></td><td>6</td></tr>
<tr style="text-align: left">
<td><code>numeric_constant</code></td><td>3</td></tr>
<tr style="text-align: left">
<td><code>integral_c</code></td><td>5</td></tr>
</table>

<p>
Accept P0377 with "<code>scalar_constant</code>" for C++17 to address LWG 2922 and US 171:
<p/>
SF | F | N | A | SA
<p/>
0  | 1 | 3 | 7 | 5
</p>

<p><i>[2017-07 Toronto Thurs Issue Prioritization]</i></p>

<p>Status LEWG with P0377</p>


<p id="res-2922"><b>Proposed resolution:</b></p>
<p>
</p>








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