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| 1 | <html> |
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| 2 | <head> |
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| 3 | <title>BOOST_PP_EMPTY</title> |
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| 4 | <link rel="stylesheet" type="text/css" href="../styles.css"> |
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| 5 | |
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| 6 | </head> |
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| 7 | <body> |
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| 8 | <div style="margin-left: 0px;"> |
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| 9 | The <b>BOOST_PP_EMPTY</b> macro is a nullary utility macro that expands to nothing. |
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| 10 | </div> |
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| 11 | <h4>Usage</h4> |
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| 12 | <div class="code"> |
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| 13 | <b>BOOST_PP_EMPTY</b>() |
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| 14 | </div> |
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| 15 | <h4>Remarks</h4> |
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| 16 | <div> |
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| 17 | This macro is helps avoid inefficient macro-expansion. |
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| 18 | It is primarily useful as arguments to <b>BOOST_PP_IF</b> or <b>BOOST_PP_IIF</b>. |
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| 19 | </div> |
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| 20 | <h4>Requirements</h4> |
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| 21 | <div> |
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| 22 | <b>Header:</b> <a href="../headers/facilities/empty.html"><boost/preprocessor/facilities/empty.hpp></a> |
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| 23 | </div> |
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| 24 | <h4>Sample Code</h4> |
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| 25 | <div><pre> |
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| 26 | #include <<a href="../headers/control/if.html">boost/preprocessor/control/if.hpp</a>> |
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| 27 | #include <<a href="../headers/facilities/empty.html">boost/preprocessor/facilities/empty.hpp</a>> |
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| 28 | |
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| 29 | #define X() result |
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| 30 | #define MACRO(c) <a href="if.html">BOOST_PP_IF</a>(c, X, <a href="empty.html">BOOST_PP_EMPTY</a>)() |
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| 31 | |
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| 32 | MACRO(0) // expands to nothing |
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| 33 | MACRO(1) // expands to result |
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| 34 | </pre></div> |
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| 35 | </body> |
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| 36 | </html> |
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