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<div class="document" id="wording-for-decay-make-pair-and-make-tuple">
<h1 class="title">Wording for decay, make_pair and make_tuple</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
<col class="docinfo-content" />
<tbody valign="top">
<tr><th class="docinfo-name">Author:</th>
<td>Thorsten Ottosen</td></tr>
<tr><th class="docinfo-name">Contact:</th>
<td><a class="first last reference" href="mailto:thorsten.ottosen&#64;dezide.com">thorsten.ottosen&#64;dezide.com</a></td></tr>
<tr class="field"><th class="docinfo-name">organizations:</th><td class="field-body">Dezide Aps</td>
</tr>
<tr><th class="docinfo-name">Date:</th>
<td>2006-04-18</td></tr>
<tr class="field"><th class="docinfo-name">Number:</th><td class="field-body">WG21/N2244 J16/07-0104</td>
</tr>
<tr class="field"><th class="docinfo-name">Working Group:</th><td class="field-body">Library</td>
</tr>
</tbody>
</table>
<div class="abstract topic">
<p class="topic-title first">Abstract</p>
<p>This paper provides wording for the type-trait decay and
new wording for the functions make_pair of make_tuple to make them optimally
efficient. This change was motivated in <a class="reference" href="http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2006/n2069.html">n2069</a>.</p>
</div>
<div class="contents topic">
<p class="topic-title first"><a id="table-of-contents" name="table-of-contents">Table of Contents</a></p>
<ul class="auto-toc simple">
<li><a class="reference" href="#introduction" id="id1" name="id1">1&nbsp;&nbsp;&nbsp;Introduction</a></li>
<li><a class="reference" href="#wording" id="id2" name="id2">2&nbsp;&nbsp;&nbsp;Wording</a></li>
</ul>
</div>
<div class="section">
<h1><a class="toc-backref" href="#id1" id="introduction" name="introduction">1&nbsp;&nbsp;&nbsp;Introduction</a></h1>
<p>Each numbered section below describes a new section
for the standard or modifications to an existing section.
Comments are written in <strong>bold</strong> and are not part of the wording.</p>
<p>The author would like to thank Douglas Gregor and Howard Hinnant. Any mistake
is the responsibility of the author.</p>
</div>
<div class="section">
<h1><a class="toc-backref" href="#id2" id="wording" name="wording">2&nbsp;&nbsp;&nbsp;Wording</a></h1>
<p><strong>Extend the synopsis of 20.4.2 to include the following</strong></p>
<pre class="literal-block">
template &lt;class T&gt; struct decay;
</pre>
<p><strong>Add the following row to Table 46 (Other transformations):</strong></p>
<table border="1" class="docutils">
<colgroup>
<col width="30%" />
<col width="19%" />
<col width="51%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head"><strong>Template</strong></th>
<th class="head"><strong>Condition</strong></th>
<th class="head"><strong>Comments</strong></th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="docutils literal"><span class="pre">template</span> <span class="pre">&lt;class</span> <span class="pre">T&gt;</span> <span class="pre">struct</span> <span class="pre">decay;</span></tt></td>
<td>&nbsp;</td>
<td>Let <tt class="docutils literal"><span class="pre">U</span></tt> be <tt class="docutils literal"><span class="pre">remove_reference&lt;T&gt;::type</span></tt>.
If <tt class="docutils literal"><span class="pre">is_array&lt;U&gt;::value</span></tt> is <tt class="docutils literal"><span class="pre">true</span></tt>, the member typedef
<tt class="docutils literal"><span class="pre">type</span></tt> shall equal <tt class="docutils literal"><span class="pre">remove_extent&lt;U&gt;::type*</span></tt>.
If <tt class="docutils literal"><span class="pre">is_function&lt;U&gt;::value</span></tt> is <tt class="docutils literal"><span class="pre">true</span></tt>, the member typedef
<tt class="docutils literal"><span class="pre">type</span></tt> shall equal <tt class="docutils literal"><span class="pre">add_pointer&lt;U&gt;::type</span></tt>. Otherwise
the member typedef <tt class="docutils literal"><span class="pre">type</span></tt> equals <tt class="docutils literal"><span class="pre">U</span></tt>.</td>
</tr>
</tbody>
</table>
<p><strong>Modify make_pair() in the synopsis of 20.2 to read</strong></p>
<pre class="literal-block">
template&lt;class T1, class T2&gt; 
pair&lt; typename decay&lt;T1&gt;::type, typename decay&lt;T2&gt;::type &gt; make_pair(T1&amp;&amp;, T2&amp;&amp;);
</pre>
<p><strong>Modify the specification of make_pair() in 20.2.2 to read</strong></p>
<pre class="literal-block">
template&lt;class T1, class T2&gt; 
pair&lt; typename decay&lt;T1&gt;::type, typename decay&lt;T2&gt;::type &gt; make_pair(T1&amp;&amp; x, T2&amp;&amp; y);
</pre>
<p><em>Returns</em>: <tt class="docutils literal"><span class="pre">pair&lt;</span> <span class="pre">typename</span> <span class="pre">decay&lt;T1&gt;::type,</span> <span class="pre">typename</span> <span class="pre">decay&lt;T2&gt;::type</span> <span class="pre">&gt;(</span> <span class="pre">forward&lt;T1&gt;(x),</span> <span class="pre">forward&lt;T2&gt;(y)</span> <span class="pre">)</span></tt></p>
<p><strong>and remove the footnote 222.</strong></p>
<p><strong>Modify the specification of make_tuple() in 20.3.1.2 to read</strong></p>
<pre class="literal-block">
template&lt;class... Types&gt;
tuple&lt;VTypes...&gt; make_tuple( Types&amp;&amp;... t);
</pre>
<p>where each <tt class="docutils literal"><span class="pre">Vi</span></tt> in <tt class="docutils literal"><span class="pre">VTypes</span></tt> is <tt class="docutils literal"><span class="pre">X&amp;</span></tt> if for the corresponding type <tt class="docutils literal"><span class="pre">Ti</span></tt> in <tt class="docutils literal"><span class="pre">Types</span></tt> 
<tt class="docutils literal"><span class="pre">remove_cv&lt;</span> <span class="pre">remove_reference&lt;Ti&gt;::type</span> <span class="pre">&gt;::type</span></tt> equals
<tt class="docutils literal"><span class="pre">reference_wrapper&lt;X&gt;</span></tt>,
otherwise <tt class="docutils literal"><span class="pre">Vi</span></tt> is <tt class="docutils literal"><span class="pre">decay&lt;Ti&gt;::type</span></tt>.</p>
<!-- corresponding reference-qualifier-removed cv-unqualified  -->
<p><em>Returns:</em> <tt class="docutils literal"><span class="pre">tuple&lt;VTypes...&gt;(forward&lt;Types&gt;(t)...)</span></tt></p>
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