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< p >
< code class = "computeroutput" > < span class = "identifier" > optional< / span > < span class = "special" > < < / span > < span class = "identifier" > T< / span > < span class = "special" > > < / span > < / code > is
currently implemented using a custom aligned storage facility built from < code class = "computeroutput" > < span class = "identifier" > alignment_of< / span > < / code > and < code class = "computeroutput" > < span class = "identifier" > type_with_alignment< / span > < / code >
(both from Type Traits). It uses a separate boolean flag to indicate the initialization
state. Placement new with < code class = "computeroutput" > < span class = "identifier" > T< / span > < / code > 's
copy constructor and < code class = "computeroutput" > < span class = "identifier" > T< / span > < / code > 's destructor
are explicitly used to initialize,copy and destroy optional values. As a result,
< code class = "computeroutput" > < span class = "identifier" > T< / span > < / code > 's default constructor is
effectively by-passed, but the exception guarantees are basic. It is planned
to replace the current implementation with another with stronger exception
safety, such as a future < code class = "computeroutput" > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > variant< / span > < / code > .
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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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