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- <html>
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- <title>BOOST_PP_LIST_FILTER</title>
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- <div style="margin-left: 0px;">
- The <b>BOOST_PP_LIST_FILTER</b> macro filters a <i>list</i> according to a supplied criterion.
- </div>
- <h4>Usage</h4>
- <div class="code">
- <b>BOOST_PP_LIST_FILTER</b>(<i>pred</i>, <i>data</i>, <i>list</i>)
- </div>
- <h4>Arguments</h4>
- <dl>
- <dt>pred</dt>
- <dd>
- A ternary predicate of the form <i>pred</i>(<i>d</i>, <i>data</i>, <i>elem</i>).
- This predicate is expanded by <b>BOOST_PP_LIST_FILTER</b> for each element in <i>list</i> with the next available <b>BOOST_PP_WHILE</b> iteration,
- the auxiliary <i>data</i>, and the current element in <i>list</i>.
- This macro must return a integral value in the range of <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.
- If this predicate expands to non-zero for a certain element, that element is included in the resulting <i>list</i>.
- </dd>
- <dt>data</dt>
- <dd>
- Auxiliary data passed to <i>pred</i>.
- </dd>
- <dt>list</dt>
- <dd>
- The <i>list</i> to be filtered.
- </dd>
- </dl>
- <h4>Remarks</h4>
- <div>
- This macro expands <i>pred</i> for each element in <i>list</i>.
- It builds a new <i>list</i> out of each element for which <i>pred</i> returns non-zero.
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- <div>
- Previously, this macro could not be used inside <b>BOOST_PP_WHILE</b>.
- There is no longer any such restriction.
- It is more efficient, however, to use <b>BOOST_PP_LIST_FILTER_D</b> in such a situation.
- </div>
- <h4>See Also</h4>
- <ul>
- <li><a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li>
- <li><a href="list_filter_d.html">BOOST_PP_LIST_FILTER_D</a></li>
- </ul>
- <h4>Requirements</h4>
- <div>
- <b>Header:</b> <a href="../headers/list/filter.html"><boost/preprocessor/list/filter.hpp></a>
- </div>
- <h4>Sample Code</h4>
- <div><pre>
- #include <<a href="../headers/comparison/less_equal.html">boost/preprocessor/comparison/less_equal.hpp</a>>
- #include <<a href="../headers/list/filter.html">boost/preprocessor/list/filter.hpp</a>>
- #define LIST (1, (3, (2, (5, <a href="nil.html">BOOST_PP_NIL</a>))))
- #define PRED(d, data, elem) <a href="less_equal.html">BOOST_PP_LESS_EQUAL</a>(elem, data)
- <a href="list_filter.html">BOOST_PP_LIST_FILTER</a>(PRED, 3, LIST)
- // expands to (1, (3, (2, <a href="nil.html">BOOST_PP_NIL</a>)))
- </pre></div>
- <hr size="1">
- <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>
- </div>
- <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>
- </div>
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- </html>
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