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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="hash.disable"></a><a class="link" href="disable.html" title="Disabling The Extensions">Disabling The Extensions</a>
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</h2></div></div></div>
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<p>
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While <code class="computeroutput"><a class="link" href="../boost/hash.html" title="Struct template hash">boost::hash</a></code>'s extensions are
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generally useful, you might want to turn them of in order to check that your
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code will work with other implementations of TR1. To do this define the macro
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<code class="computeroutput"><span class="identifier">BOOST_HASH_NO_EXTENSIONS</span></code>. When
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this macro is defined, only the specialisations detailed in TR1 will be declared.
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But, if you later undefine the macro and include <<code class="computeroutput"><a class="link" href="reference.html#header.boost.container_hash.hash_hpp" title="Header <boost/container_hash/hash.hpp>">boost/container_hash/hash.hpp</a></code>>
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then the non-specialised form will be defined - activating the extensions.
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</p>
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<p>
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It is strongly recommended that you never undefine the macro - and only define
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it so that it applies to the complete translation unit, either by defining
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it at the beginning of the main source file or, preferably, by using a compiler
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switch or preference. And you really should never define it in header files.
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</p>
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<p>
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If you are writing a library which has code in the header which requires the
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extensions, then the best action is to tell users not to define the macro.
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Their code won't <span class="emphasis"><em>require</em></span> the macro.
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</p>
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<p>
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Translation units that are compiled with the macro defined will link with units
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that were compiled without it. This feature has been designed to avoid ODR
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violations.
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<td align="right"><div class="copyright-footer">Copyright © 2005-2008 Daniel
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James<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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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