libs/preprocessor/doc/ref/tuple_elem.html

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   3     <title>BOOST_PP_TUPLE_ELEM</title>
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   8                 The <b>BOOST_PP_TUPLE_ELEM</b> macro extracts an element from a <i>tuple</i>.
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  10         <h4>Usage</h4>
  11                 <div class="code">
  12                         <b>BOOST_PP_TUPLE_ELEM</b>(<i>size</i>, <i>i</i>, <i>tuple</i>)<sup></sup><br>
  13 <br>
  14 or<br>
  15 <br>
  16 <b>BOOST_PP_TUPLE_ELEM</b>(<i>...</i>) <a href="../topics/variadic_macros.html#VNotation" target="_self"><sup>(v)</sup></a><b></b><br>
  17 </div>
  18         <h4>Arguments</h4>
  19                 <dl>
  20                         <dt>size</dt>
  21                         <dd>
  22                                 The size of the <i>tuple</i>.&nbsp;
  23                                 Valid <i>tuple</i> sizes range from <i>1</i> to <b>BOOST_PP_LIMIT_TUPLE</b>.&nbsp;
  24                         </dd>
  25                         <dt>i</dt>
  26                         <dd>
  27                                 The zero-based index into the <i>tuple</i> of the element to be extracted.&nbsp;
  28                                 Valid values range from <i>0</i> to <i>size</i> - <i>1</i>.
  29                         </dd>
  30                         <dt>tuple</dt>
  31                         <dd>
  32                                 The <i>tuple</i> from which an element is to be extracted.
  33                         </dd>
  34                 </dl>
  35         <h4>Remarks</h4>
  36                 <div>
  37                         The <i>size</i> argument must be the actual size of the <i>tuple</i>,
  38                         and <i>i</i> must be less than the size of the <i>tuple</i>. <br>
  39             <br>You can
  40             invoke the variadic version as BOOST_PP_TUPLE_ELEM(<i>i</i>,<i>tuple</i>) or
  41             BOOST_PP_TUPLE_ELEM(<i>size</i>,<i>i</i>,<i>tuple</i>).
  42                 </div>
  43         <h4>See Also</h4>
  44                 <ul>
  45                         <li><a href="limit_tuple.html">BOOST_PP_LIMIT_TUPLE</a></li>
  46                 </ul>
  47         <h4>Requirements</h4>
  48                 <div>
  49                         <b>Header:</b> &nbsp;<a href="../headers/tuple/elem.html">&lt;boost/preprocessor/tuple/elem.hpp&gt;</a>
  50                 </div>
  51         <h4>Sample Code</h4>
  52 <div><pre>#include &lt;<a href="../headers/tuple/elem.html">boost/preprocessor/tuple/elem.hpp</a>&gt;<br><br>#define TUPLE (a, b, c, d)<br><br><a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, TUPLE) // expands to a<br><a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 3, TUPLE) // expands to d<br><br>// or for the variadic version <a href="../topics/variadic_macros.html#VNotation" target="_self"><sup>(v)</sup></a><br><br><a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(0, TUPLE) // expands to a in the variadic version<br><a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(3, TUPLE) // expands to d in the variadic version<br></pre></div>
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  55                 <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
  56                 <br><i>© Copyright Paul Mensonides 2002<br>
  57         </i><i>© Copyright Edward Diener 2011,2013</i><br>
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  60                 <p><small>Distributed under the Boost Software License, Version 1.0. (See
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  62                 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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