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<title>Issue 3134: [fund.ts.v3] LFTSv3 contains extraneous [meta] variable templates that should have been deleted by P09961</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="3134"><a href="lwg-defects.html#3134">3134</a>. [fund.ts.v3] LFTSv3 contains extraneous [meta] variable templates that should have been deleted by P09961</h3>
<p><b>Section:</b> 99 <a href="https://cplusplus.github.io/fundamentals-ts/v3.html#meta.type.synop">[fund.ts.v3::meta.type.synop]</a> <b>Status:</b> <a href="lwg-active.html#Resolved">Resolved</a>
 <b>Submitter:</b> Thomas K&ouml;ppe <b>Opened:</b> 2018-07-02 <b>Last modified:</b> 2020-09-06</p>
<p><b>Priority: </b>0
</p>
<p><b>View all other</b> <a href="lwg-index.html#fund.ts.v3::meta.type.synop">issues</a> in [fund.ts.v3::meta.type.synop].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Resolved">Resolved</a> status.</p>
<p><b>Discussion:</b></p>
<p><b>Addresses: fund.ts.v3</b></p>
<p>
The LFTSv3 prospective-working-paper <a href="https://wg21.link/n4758">N4758</a> lists a large number of type trait 
variable templates in [meta.type.synop] that are duplicates of corresponding ones in C++17. The paper 
<a href="https://wg21.link/P0996R1">P0996R1</a> that was meant to rebase the LFTS on C++17 appears to have missed them.
</p>

<p><i>[2018-07-20 Status to Tentatively Ready after five positive votes on the reflector.]</i></p>


<p><i>[2018-11-11 Resolved by <a href="https://wg21.link/P1210R0">P1210R0</a>, adopted in San Diego.]</i></p>



<p id="res-3134"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/n4758">N4758</a>.
</p>

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<p>
Delete from 99 <a href="https://cplusplus.github.io/fundamentals-ts/v3.html#meta.type.synop">[fund.ts.v3::meta.type.synop]</a> all variable templates starting at <code>is_void_v</code> up to and including 
<code>is_convertible_v</code> as indicated:
</p>
<blockquote>
<pre>
#include &lt;type_traits&gt;

namespace std::experimental {
inline namespace fundamentals_v3 {

  <del><i>// See C++17 &sect;23.15.4.1, primary type categories</i>
  template &lt;class T&gt; constexpr bool is_void_v
    = is_void&lt;T&gt;::value;
  [&hellip;]
  template &lt;class From, class To&gt; constexpr bool is_convertible_v
    = is_convertible&lt;From, To&gt;::value;</del>

  // 3.3.2, Other type transformations
  template &lt;class&gt; class invocation_type; // not defined
  [&hellip;]
} // inline namespace fundamentals_v3
} // namespace std::experimental
</pre>
</blockquote>
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