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14<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./numeric-metafunction.html" class="navigation-link">Prev</a>&nbsp;<a href="./type-selection.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./numeric-metafunction.html" class="navigation-link">Back</a>&nbsp;Along</span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./metafunctions-concepts.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td>
15<td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./metafunctions.html" class="navigation-link">Metafunctions</a> / <a href="./metafunctions-concepts.html" class="navigation-link">Concepts</a> / <a href="./trivial-metafunction.html" class="navigation-link">Trivial Metafunction</a></td>
16</tr></table><div class="header-separator"></div>
17<div class="section" id="trivial-metafunction">
18<h1><a class="toc-backref" href="./metafunctions-concepts.html#id444" name="trivial-metafunction">Trivial Metafunction</a></h1>
19<div class="section" id="trivial-description">
20<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
21<p>A <a class="reference" href="./trivial-metafunction.html">Trivial Metafunction</a> accepts a single argument of a class type <tt class="literal"><span class="pre">x</span></tt> and
22returns the <tt class="literal"><span class="pre">x</span></tt>'s nested type member <tt class="literal"><span class="pre">x::name</span></tt>, where <tt class="literal"><span class="pre">name</span></tt> is
23a placeholder token for the actual member's name accessed by a specific
24metafunction's instance. By convention, all <a class="reference" href="./trivial-metafunctions.html">trivial metafunctions</a> in MPL
25are named after the members they provide assess to. For instance, a <a class="reference" href="./trivial-metafunction.html">Trivial Metafunction</a> named <tt class="literal"><span class="pre">first</span></tt> reaches for the <tt class="literal"><span class="pre">x</span></tt>'s nested member
26<tt class="literal"><span class="pre">::first</span></tt>.</p>
27</div>
28<div class="section" id="trivial-expression-requirements">
29<h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
30<p>In the following table and subsequent specifications, <tt class="literal"><span class="pre">name</span></tt> is placeholder token for the names of
31the <a class="reference" href="./trivial-metafunction.html">Trivial Metafunction</a> itself and the accessed member, and <tt class="literal"><span class="pre">x</span></tt> is
32a class type such that <tt class="literal"><span class="pre">x::name</span></tt> is a valid <em>type-name</em>.</p>
33<table border="1" class="table">
34<colgroup>
35<col width="37%" />
36<col width="26%" />
37<col width="37%" />
38</colgroup>
39<thead valign="bottom">
40<tr><th>Expression</th>
41<th>Type</th>
42<th>Complexity</th>
43</tr>
44</thead>
45<tbody valign="top">
46<tr><td><tt class="literal"><span class="pre">name&lt;x&gt;::type</span></tt></td>
47<td>Any type</td>
48<td>Constant time.</td>
49</tr>
50</tbody>
51</table>
52</div>
53<div class="section" id="trivial-expression-semantics">
54<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
55<pre class="literal-block">
56typedef name&lt;x&gt;::type r;
57</pre>
58<table class="field-list" frame="void" rules="none">
59<col class="field-name" />
60<col class="field-body" />
61<tbody valign="top">
62<tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">x::name</span></tt> is a valid <em>type-name</em>.</td>
63</tr>
64<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">is_same&lt;r,x::name&gt;::value</span> <span class="pre">==</span> <span class="pre">true</span></tt>.</td>
65</tr>
66</tbody>
67</table>
68</div>
69<div class="section" id="trivial-models">
70<h3><a class="subsection-title" href="#models" name="models">Models</a></h3>
71<ul class="simple">
72<li><a class="refentry reference" href="./trivial-metafunctions.html#trivial-first"><tt class="refentry literal"><span class="pre">first</span></tt></a></li>
73<li><a class="refentry reference" href="./trivial-metafunctions.html#trivial-second"><tt class="refentry literal"><span class="pre">second</span></tt></a></li>
74<li><a class="refentry reference" href="./trivial-metafunctions.html#trivial-base"><tt class="refentry literal"><span class="pre">base</span></tt></a></li>
75</ul>
76</div>
77<div class="section" id="trivial-see-also">
78<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
79<p><a class="reference" href="./metafunctions.html">Metafunctions</a>, <a class="reference" href="./trivial.html">Trivial Metafunctions</a>, <a class="refentry reference" href="./identity.html"><tt class="refentry literal"><span class="pre">identity</span></tt></a></p>
80<!-- modtime: November 10, 2004 04:31:05 +0000 -->
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83
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