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<title>Optional references</title>
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="boost_optional.optional_references"></a><a class="link" href="optional_references.html" title="Optional references">Optional references</a>
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<p>
This library allows the template parameter <code class="computeroutput"><span class="identifier">T</span></code>
to be of reference type: <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span></code>, and to some extent, <code class="computeroutput"><span class="identifier">T</span>
<span class="keyword">const</span><span class="special">&</span></code>.
</p>
<p>
However, since references are not real objects some restrictions apply and
some operations are not available in this case:
</p>
<div class="itemizedlist"><ul type="disc">
<li>
Converting constructors
</li>
<li>
Converting assignment
</li>
<li>
InPlace construction
</li>
<li>
InPlace assignment
</li>
<li>
Value-access via pointer
</li>
</ul></div>
<p>
Also, even though <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>
treats it wrapped pseudo-object much as a real value, a true real reference
is stored so aliasing will ocurr:
</p>
<div class="itemizedlist"><ul type="disc">
<li>
Copies of <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>
will copy the references but all these references will nonetheless reefer
to the same object.
</li>
<li>
Value-access will actually provide access to the referenced object rather
than the reference itself.
</li>
</ul></div>
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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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