1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>use_default</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../index.html" title="Chapter 1. Boost.Core"> 8<link rel="up" href="../index.html" title="Chapter 1. Boost.Core"> 9<link rel="prev" href="uncaught_exceptions.html" title="uncaught_exceptions"> 10</head> 11<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 12<table cellpadding="2" width="100%"><tr> 13<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 14<td align="center"><a href="../../../../../index.html">Home</a></td> 15<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 16<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 17<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 18<td align="center"><a href="../../../../../more/index.htm">More</a></td> 19</tr></table> 20<hr> 21<div class="spirit-nav"> 22<a accesskey="p" href="uncaught_exceptions.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a> 23</div> 24<div class="section"> 25<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 26<a name="core.use_default"></a><a class="link" href="use_default.html" title="use_default">use_default</a> 27</h2></div></div></div> 28<div class="toc"><dl class="toc"> 29<dt><span class="section"><a href="use_default.html#core.use_default.overview">Overview</a></span></dt> 30<dt><span class="section"><a href="use_default.html#core.use_default.example">Example</a></span></dt> 31<dt><span class="section"><a href="use_default.html#core.use_default.reference">Reference</a></span></dt> 32</dl></div> 33<div class="section"> 34<div class="titlepage"><div><div><h3 class="title"> 35<a name="core.use_default.overview"></a><a class="link" href="use_default.html#core.use_default.overview" title="Overview">Overview</a> 36</h3></div></div></div> 37<p> 38 The header <boost/core/use_default.hpp> provides the type <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span></code> which is used by other Boost 39 libraries as a sentinel type in a templates to indicate defaults. 40 </p> 41</div> 42<div class="section"> 43<div class="titlepage"><div><div><h3 class="title"> 44<a name="core.use_default.example"></a><a class="link" href="use_default.html#core.use_default.example" title="Example">Example</a> 45</h3></div></div></div> 46<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Derived</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Base</span><span class="special">,</span> 47 <span class="keyword">class</span> <span class="identifier">Value</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span><span class="special">,</span> 48 <span class="keyword">class</span> <span class="identifier">CategoryOrTraversal</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span><span class="special">,</span> 49 <span class="keyword">class</span> <span class="identifier">Reference</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span><span class="special">,</span> 50 <span class="keyword">class</span> <span class="identifier">Difference</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span><span class="special">></span> 51<span class="keyword">class</span> <span class="identifier">iterator_adaptor</span><span class="special">;</span> 52 53<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Value</span><span class="special">></span> 54<span class="keyword">class</span> <span class="identifier">node_iterator</span> 55 <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">iterator_adaptor</span><span class="special"><</span><span class="identifier">node_iterator</span><span class="special"><</span><span class="identifier">Value</span><span class="special">>,</span> <span class="identifier">Value</span><span class="special">*,</span> 56 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_traversal_tag</span><span class="special">>;</span> 57</pre> 58</div> 59<div class="section"> 60<div class="titlepage"><div><div><h3 class="title"> 61<a name="core.use_default.reference"></a><a class="link" href="use_default.html#core.use_default.reference" title="Reference">Reference</a> 62</h3></div></div></div> 63<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> 64 <span class="keyword">struct</span> <span class="identifier">use_default</span> <span class="special">{</span> <span class="special">};</span> 65<span class="special">}</span> 66</pre> 67</div> 68</div> 69<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 70<td align="left"></td> 71<td align="right"><div class="copyright-footer">Copyright © 2014 Peter Dimov<br>Copyright © 2014 Glen Fernandes<br>Copyright © 2014 Andrey Semashev<p> 72 Distributed under the <a href="http://boost.org/LICENSE_1_0.txt" target="_top">Boost 73 Software License, Version 1.0</a>. 74 </p> 75</div></td> 76</tr></table> 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