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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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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 > .
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However, since references are not real objects some restrictions apply and
some operations are not available in this case:
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Converting constructors
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Converting assignment
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InPlace construction
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InPlace assignment
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Value-access via pointer
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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:
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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.
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Value-access will actually provide access to the referenced object rather
than the reference itself.
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< td align = "right" > < div class = "copyright-footer" > Copyright © 2003-2007 Fernando Luis Cacciola Carballal< p >
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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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