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- <div class="titlepage"><div><div><h2 class="title" style="clear: both">
- <a name="boost_optional.type_requirements"></a><a class="link" href="type_requirements.html" title="Type requirements">Type requirements</a>
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- <p>
- At the very minimum for <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
- to work with a minimum interface it is required that <code class="computeroutput"><span class="identifier">T</span></code>
- has a publicly accessible no-throw destructor. In that case you need to initialize
- the optional object with function <code class="computeroutput"><span class="identifier">emplace</span><span class="special">()</span></code> or use <span class="bold"><strong>InPlaceFactories</strong></span>.
- Additionally, if <code class="computeroutput"><span class="identifier">T</span></code> is <code class="computeroutput"><span class="identifier">Moveable</span></code>, <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
- is also <code class="computeroutput"><span class="identifier">Moveable</span></code> and can be
- easily initialized from an rvalue of type <code class="computeroutput"><span class="identifier">T</span></code>
- and be passed by value. Additionally, if <code class="computeroutput"><span class="identifier">T</span></code>
- is <code class="computeroutput"><span class="identifier">Copyable</span></code>, <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is
- also <code class="computeroutput"><span class="identifier">Copyable</span></code> and can be easily
- initialized from an lvalue of type <code class="computeroutput"><span class="identifier">T</span></code>.
- </p>
- <p>
- <code class="computeroutput"><span class="identifier">T</span></code> <span class="underline">is
- not</span> required to be <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html" target="_top">Default
- Constructible</a>.
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