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| <title>BOOST_PP_EXPAND</title> |
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| The <b>BOOST_PP_EXPAND</b> macro performs a double macro-expansion on its argument. |
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| <h4>Usage</h4> |
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| <b>BOOST_PP_EXPAND</b>(<i>x</i>) |
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| <h4>Arguments</h4> |
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| <dt>x</dt> |
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| The argument to be expanded twice. |
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| <h4>Remarks</h4> |
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| This macro is useful when a delay is necessary to produce the correct semantics of a macro invocation. |
| For example, when a macro expands to an argument list to another macro. |
| This macro will expand the the argument list on the first pass, and then rescan to expand any more macros. |
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| <h4>Requirements</h4> |
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| <b>Header:</b> <a href="../headers/facilities/expand.html"><boost/preprocessor/facilities/expand.hpp></a> |
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| <h4>Sample Code</h4> |
| <div><pre> |
| #include <<a href="../headers/control/if.html">boost/preprocessor/control/if.hpp</a>> |
| #include <<a href="../headers/facilities/expand.html">boost/preprocessor/facilities/expand.hpp</a>> |
| |
| #define MACRO(a, b, c) (a)(b)(c) |
| #define ARGS() (1, 2, 3) |
| |
| <a href="expand.html">BOOST_PP_EXPAND</a>(MACRO ARGS()) // expands to (1)(2)(3) |
| |
| #define SAMPLE(n) \ |
| <a href="expand.html">BOOST_PP_EXPAND</a>( \ |
| MACRO \ |
| <a href="if.html">BOOST_PP_IF</a>( \ |
| n, \ |
| (x, y, z), \ |
| (a, b, c) \ |
| ) \ |
| ) \ |
| /**/ |
| |
| SAMPLE(0) // expands to (a)(b)(c) |
| SAMPLE(1) // expands to (x)(y)(z) |
| </pre></div> |
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| <div style="margin-left: 0px;"> |
| <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i> |
| </br><i>© Copyright Paul Mensonides 2002</i> |
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| <div style="margin-left: 0px;"> |
| <p><small>Distributed under the Boost Software License, Version 1.0. (See |
| accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or |
| copy at <a href= |
| "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p> |
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