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| <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: |
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| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| Converting constructors |
| </li> |
| <li class="listitem"> |
| Converting assignment |
| </li> |
| <li class="listitem"> |
| InPlace construction |
| </li> |
| <li class="listitem"> |
| InPlace assignment |
| </li> |
| <li class="listitem"> |
| 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 class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| 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 class="listitem"> |
| Value-access will actually provide access to the referenced object rather |
| than the reference itself. |
| </li> |
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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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