2002-10-03 22:13:37 +00:00
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<title>BOOST_PP_LIST_CONS</title>
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<link rel="stylesheet" type="text/css" href="../styles.css">
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</head>
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<body>
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<div style="margin-left: 0px;">
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The <b>BOOST_PP_LIST_CONS</b> macro is a <i>list</i> constructor.
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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_CONS</b>(<i>head</i>, <i>tail</i>)
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</div>
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<h4>Arguments</h4>
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<dl>
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<dt>head</dt>
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<dd>
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An element in a <i>list</i>.
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</dd>
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<dt>tail</dt>
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<dd>
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Either a <i>list</i>, <b>BOOST_PP_LIST_NIL</b>, or <b>BOOST_PP_NIL</b>.
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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 appends a new head to an existing <i>list</i> or creates a <i>list</i> from <b>BOOST_PP_LIST_NIL</b>.
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</div>
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<div>
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This macro is no longer necessary.
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For example...
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<div>
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<b>BOOST_PP_LIST_CONS</b>(a, <b>BOOST_PP_LIST_CONS</b>(b, <b>BOOST_PP_LIST_NIL</b>)))
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</div>
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...is just an explicit way of writing the following:
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<div>
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(a, (b, <b>BOOST_PP_NIL</b>))
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</div>
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Because of this, this macro is deprecated.
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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_nil.html">BOOST_PP_LIST_NIL</a></li>
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<li><a href="nil.html">BOOST_PP_NIL</a></li>
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</ul>
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<h4>Requirements</h4>
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<div>
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2004-10-11 06:58:45 +00:00
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<b>Header:</b> <a href="../headers/list/adt.html"><boost/preprocessor/list/adt.hpp></a>
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2002-10-03 22:13:37 +00:00
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</div>
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<h4>Sample Code</h4>
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<div><pre>
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2004-10-11 06:58:45 +00:00
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#include <<a href="../headers/list/adt.html">boost/preprocessor/list/adt.hpp</a>>
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2002-10-03 22:13:37 +00:00
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#define OLD \
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<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
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a, \
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<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
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b, \
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<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
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c, \
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<a href="list_nil.html">BOOST_PP_LIST_NIL</a> \
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) \
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) \
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) \
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/**/
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#define NEW (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)))
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<a href="list_first.html">BOOST_PP_LIST_FIRST</a>(OLD) == <a href="list_first.html">BOOST_PP_LIST_FIRST</a>(NEW)
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// expands to a == a
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<a href="list_rest.html">BOOST_PP_LIST_REST</a>(OLD) == <a href="list_rest.html">BOOST_PP_LIST_REST</a>(NEW)
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// expands to (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)) == (b, (c, <a href="nil.html">BOOST_PP_NIL</a>))
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</pre></div>
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</body>
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</html>
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