<span class="keyword">struct</span> <a class="link" href="is_old_value_copyable.html" title="Struct template is_old_value_copyable">is_old_value_copyable</a> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_copy_constructible</span><span class="special"><</span> <span class="identifier">T</span> <span class="special">></span> <span class="special">{</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
-<a name="idm45751728270496"></a><h2>Description</h2>
-<p>By default, this unary boolean meta-function is equivalent to <code class="computeroutput">boost::is_copy_constructible<T></code> but programmers can chose to specialize it for user-defined types (in general some kind of specialization is needed on compilers that do not support C++11, see <a href="http://www.boost.org/doc/libs/release/libs/type_traits/doc/html/boost_typetraits/reference/is_copy_constructible.html" target="_top"><code class="computeroutput">boost::is_copy_constructible</code></a>):</p>
-<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">u</span><span class="special">;</span> <span class="comment">// Some user-defined type.</span>
+<a name="idm45707994778288"></a><h2>Description</h2>
+<p>By default, this unary boolean meta-function is equivalent to <code class="computeroutput">boost::is_copy_constructible<T></code> but programmers can chose to specialize it for user-defined types (in general some kind of specialization is
also needed on compilers that do not support C++11, see <a href="http://www.boost.org/doc/libs/release/libs/type_traits/doc/html/boost_typetraits/reference/is_copy_constructible.html" target="_top"><code class="computeroutput">boost::is_copy_constructible</code></a>):</p>
+<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">u</span><span class="special">;</span> <span class="comment">// Some user-defined type for which old values shall not be copied.</span>
<span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">contract</span> <span class="special">{</span>
- <span class="keyword">template</span><span class="special"><</span><span class="special">></span> <span class="comment">// Specialization.</span>
+ <span class="keyword">template</span><span class="special"><</span><span class="special">></span> <span class="comment">// Specialization to not copy old values of type `u`.</span>
<span class="keyword">struct</span> <span class="identifier">is_old_value_copyable</span><span class="special"><</span><span class="identifier">u</span><span class="special">></span> <span class="special">:</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">false_type</span> <span class="special">{</span><span class="special">}</span><span class="special">;</span>
<span class="special">}</span> <span class="special">}</span> <span class="comment">// namespace</span>
</pre>
-<p>In summary, a given old value type <code class="computeroutput">T</code> is copied only if <code class="computeroutput">boost::contract::is_old_value_copyable<T>::value</code> is <code class="computeroutput">true</code>. Copyable old value types are always copied using <code class="computeroutput">boost::contract::old_value_copy<T></code>. Non-copyable old value types generate a compile-time error when <code class="computeroutput">boost::contract::old_ptr<T></code> is dereferenced, but instead leave <code class="computeroutput">boost::contract::old_ptr_if_copyable<T></code> always null (without generating compile-time errors).</p>
+<p>A given old value type <code class="computeroutput">T</code> is copied only if <code class="computeroutput">boost::contract::is_old_value_copyable<T>::value</code> is <code class="computeroutput">true</code>. A copyable old value type <code class="computeroutput">V</code> is always copied using <code class="computeroutput">boost::contract::old_value_copy<V></code>. A non-copyable old value type <code class="computeroutput">W</code> generates a compile-time error when <code class="computeroutput">boost::contract::old_ptr<W></code> is dereferenced, but instead leaves <code class="computeroutput">boost::contract::old_ptr_if_copyable<W></code> always null (without generating compile-time errors).</p>
<p><span class="bold"><strong>See Also:</strong></span></p>
<p> <a class="link" href="../../boost_contract/extras.html#boost_contract.extras.old_value_requirements__templates_" title="Old Value Requirements (Templates)">
Old Value Requirements</a> </p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
-<td align="right"><div class="copyright-footer">Copyright © 2008-201
8 Lorenzo Caminiti<p>
+<td align="right"><div class="copyright-footer">Copyright © 2008-201
9 Lorenzo Caminiti<p>
Distributed under the Boost Software License, Version 1.0 (see accompanying
file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
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