forked from boostorg/preprocessor
68 lines
2.5 KiB
HTML
68 lines
2.5 KiB
HTML
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<html>
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<head>
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<title>BOOST_PP_LIST_TRANSFORM</title>
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<link rel="stylesheet" type="text/css" href="../styles.css">
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<script language="javascript" type="text/javascript" src="../scripts.js"></script>
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</head>
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<body onload="init('sample');">
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<div style="margin-left: 0px;">
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The <b>BOOST_PP_LIST_TRANSFORM</b> macro transforms each element in a <i>list</i> according to a supplied transformation.
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</div>
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<h4>Usage</h4>
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<div class="code">
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<b>BOOST_PP_LIST_TRANSFORM</b>(<i>op</i>, <i>data</i>, <i>list</i>)
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</div>
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<h4>Arguments</h4>
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<dl>
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<dt>op</dt>
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<dd>
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A ternary predicate of the form <i>op</i>(<i>d</i>, <i>data</i>, <i>elem</i>).
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This transformation is expanded by <b>BOOST_PP_LIST_TRANSFORM</b> for each element in <i>list</i> with the next available <b>BOOST_PP_WHILE</b> iteration,
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the auxiliary <i>data</i>, and the current element in <i>list</i>.
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</dd>
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<dt>data</dt>
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<dd>
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Auxiliary data passed to <i>pred</i>.
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</dd>
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<dt>list</dt>
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<dd>
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The <i>list</i> to be transformed.
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</dd>
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</dl>
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<h4>Remarks</h4>
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<div>
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This macro expands <i>op</i> for each element in <i>list</i>.
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It builds a new <i>list</i> out of the results of each call.
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If, for example, <i>list</i> is (<i>a</i>, (<i>b</i>, (<i>c</i>, <b>BOOST_PP_NIL</b>))),
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this macro expands to...
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<div>
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(<i>op</i>(<i>d</i>, <i>data</i>, <i>a</i>), (<i>op</i>(<i>d</i>, <i>data</i>, <i>b</i>), (<i>op</i>(<i>d</i>, <i>data</i>, <i>c</i>), <b>BOOST_PP_NIL</b>)))
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</div>
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</div>
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<div>
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Previously, this macro could not be used inside <b>BOOST_PP_WHILE</b>.
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There is no longer any such restriction.
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It is more efficient, however, to use <b>BOOST_PP_LIST_TRANSFORM_D</b> in such a situation.
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</div>
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<h4>See Also</h4>
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<ul>
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<li><a href="list_transform_d.html">BOOST_PP_LIST_TRANSFORM_D</a></li>
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</ul>
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<h4>Requirements</h4>
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<div>
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<b>Header:</b> <a href="../headers/list/transform.hpp.html"><boost/preprocessor/list/transform.hpp></a>
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</div>
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<h4><a class="local" onclick="toggle('sample');" onmouseover="change(this);" onmouseout="revert(this);">Sample Code</a></h4>
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<div id="sample"><pre>
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#include <boost/preprocessor/arithmetic/dec.hpp>
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#include <boost/preprocessor/list/transform.hpp>
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#define LIST (1, (3, (2, (5, BOOST_PP_NIL))))
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#define OP(d, data, elem) BOOST_PP_DEC(elem)
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BOOST_PP_LIST_TRANSFORM(OP, 3, LIST) // expands to(0, (2, (1, (4, BOOST_PP_NIL))))
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<pre></div>
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</body>
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</html>
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