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| <div class="section" title="Implementation Notes"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
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| <p> |
| <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is |
| currently implemented using a custom aligned storage facility built from <code class="computeroutput"><span class="identifier">alignment_of</span></code> and <code class="computeroutput"><span class="identifier">type_with_alignment</span></code> |
| (both from Type Traits). It uses a separate boolean flag to indicate the initialization |
| state. Placement new with <code class="computeroutput"><span class="identifier">T</span></code>'s |
| copy constructor and <code class="computeroutput"><span class="identifier">T</span></code>'s destructor |
| are explicitly used to initialize,copy and destroy optional values. As a result, |
| <code class="computeroutput"><span class="identifier">T</span></code>'s default constructor is |
| effectively by-passed, but the exception guarantees are basic. It is planned |
| to replace the current implementation with another with stronger exception |
| safety, such as a future <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">variant</span></code>. |
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| <td align="right"><div class="copyright-footer">Copyright © 2003 -2007 Fernando Luis Cacciola Carballal<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
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