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