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<div><h2 class="title">
<a name="optional"></a>Chapter&#160;1.&#160;Boost.Optional</h2></div>
<div><div class="author"><h3 class="author">
<span class="firstname">Fernando Luis</span> <span class="surname">Cacciola Carballal</span>
</h3></div></div>
<div><p class="copyright">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal</p></div>
<div><p class="copyright">Copyright &#169; 2014 Andrzej Krzemie&#324;ski</p></div>
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        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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<p><b>Table of Contents</b></p>
<dl class="toc">
<dt><span class="section"><a href="index.html#optional.introduction">Introduction</a></span></dt>
<dt><span class="section"><a href="boost_optional/motivation.html">Motivation</a></span></dt>
<dt><span class="section"><a href="boost_optional/development.html">Development</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="boost_optional/development.html#boost_optional.development.the_models">The models</a></span></dt>
<dt><span class="section"><a href="boost_optional/development.html#boost_optional.development.the_semantics">The semantics</a></span></dt>
<dt><span class="section"><a href="boost_optional/development.html#boost_optional.development.the_interface">The Interface</a></span></dt>
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<dt><span class="section"><a href="boost_optional/synopsis.html">Synopsis</a></span></dt>
<dt><span class="section"><a href="boost_optional/detailed_semantics.html">Detailed Semantics</a></span></dt>
<dt><span class="section"><a href="boost_optional/examples.html">Examples</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="boost_optional/examples.html#boost_optional.examples.optional_return_values">Optional
      return values</a></span></dt>
<dt><span class="section"><a href="boost_optional/examples.html#boost_optional.examples.optional_local_variables">Optional
      local variables</a></span></dt>
<dt><span class="section"><a href="boost_optional/examples.html#boost_optional.examples.optional_data_members">Optional
      data members</a></span></dt>
<dt><span class="section"><a href="boost_optional/examples.html#boost_optional.examples.bypassing_expensive_unnecessary_default_construction">Bypassing
      expensive unnecessary default construction</a></span></dt>
</dl></dd>
<dt><span class="section"><a href="boost_optional/optional_references.html">Optional references</a></span></dt>
<dt><span class="section"><a href="boost_optional/rebinding_semantics_for_assignment_of_optional_references.html">Rebinding
    semantics for assignment of optional references</a></span></dt>
<dt><span class="section"><a href="boost_optional/in_place_factories.html">In-Place Factories</a></span></dt>
<dt><span class="section"><a href="boost_optional/a_note_about_optional_bool_.html">A note about
    optional&lt;bool&gt;</a></span></dt>
<dt><span class="section"><a href="boost_optional/exception_safety_guarantees.html">Exception Safety
    Guarantees</a></span></dt>
<dt><span class="section"><a href="boost_optional/type_requirements.html">Type requirements</a></span></dt>
<dt><span class="section"><a href="boost_optional/dependencies_and_portability.html">Dependencies
    and Portability</a></span></dt>
<dd><dl><dt><span class="section"><a href="boost_optional/dependencies_and_portability.html#boost_optional.dependencies_and_portability.optional_reference_binding">Optional
      Reference Binding</a></span></dt></dl></dd>
<dt><span class="section"><a href="boost_optional/acknowledgments.html">Acknowledgments</a></span></dt>
</dl>
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="optional.introduction"></a><a class="link" href="index.html#optional.introduction" title="Introduction">Introduction</a>
</h2></div></div></div>
<p>
      This library can be used to represent 'optional' (or 'nullable') objects that
      can be safely passed by value:
    </p>
<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">readInt</span><span class="special">();</span> <span class="comment">// this function may return either an int or a not-an-int</span>

<span class="keyword">if</span> <span class="special">(</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">oi</span> <span class="special">=</span> <span class="identifier">readInt</span><span class="special">())</span> <span class="comment">// did I get a real int</span>
  <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"my int is: "</span> <span class="special">&lt;&lt;</span> <span class="special">*</span><span class="identifier">oi</span><span class="special">;</span>   <span class="comment">// use my int</span>
<span class="keyword">else</span>
  <span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"I have no int"</span><span class="special">;</span>
</pre>
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<td align="left"><p><small>Last revised: May 08, 2014 at 12:05:10 GMT</small></p></td>
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