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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="fusion.tuple.class_template_tuple.tuple_helper_classes"></a><a class="link" href="tuple_helper_classes.html" title="Tuple helper classes">Tuple
  28         helper classes</a>
  29 </h4></div></div></div>
  30 <h6>
  31 <a name="fusion.tuple.class_template_tuple.tuple_helper_classes.h0"></a>
  32           <span class="phrase"><a name="fusion.tuple.class_template_tuple.tuple_helper_classes.description"></a></span><a class="link" href="tuple_helper_classes.html#fusion.tuple.class_template_tuple.tuple_helper_classes.description">Description</a>
  33         </h6>
  34 <p>
  35           The <a href="http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2002/n1403.pdf" target="_top">TR1
  36           Tuple</a> provides 2 helper traits, for compile time access to the
  37           tuple size, and the element types.
  38         </p>
  39 <h6>
  40 <a name="fusion.tuple.class_template_tuple.tuple_helper_classes.h1"></a>
  41           <span class="phrase"><a name="fusion.tuple.class_template_tuple.tuple_helper_classes.specification"></a></span><a class="link" href="tuple_helper_classes.html#fusion.tuple.class_template_tuple.tuple_helper_classes.specification">Specification</a>
  42         </h6>
  43 <pre class="programlisting"><span class="identifier">tuple_size</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value</span>
  44 </pre>
  45 <p>
  46           <span class="bold"><strong>Requires</strong></span>: <code class="computeroutput"><span class="identifier">T</span></code>
  47           is any fusion sequence type, including <code class="computeroutput"><span class="identifier">tuple</span></code>.
  48         </p>
  49 <p>
  50           <span class="bold"><strong>Type</strong></span>: <a href="http://www.boost.org/libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
  51           Integral Constant</a>
  52         </p>
  53 <p>
  54           <span class="bold"><strong>Value</strong></span>: The number of elements in the sequence.
  55           Equivalent to <code class="computeroutput"><a class="link" href="../../sequence/intrinsic/metafunctions/size.html" title="size"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">size</span></code></a><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">type</span></code>.
  56         </p>
  57 <pre class="programlisting"><span class="identifier">tuple_element</span><span class="special">&lt;</span><span class="identifier">I</span><span class="special">,</span> <span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">type</span>
  58 </pre>
  59 <p>
  60           <span class="bold"><strong>Requires</strong></span>: <code class="computeroutput"><span class="identifier">T</span></code>
  61           is any fusion sequence type, including <code class="computeroutput"><span class="identifier">tuple</span></code>.
  62           <code class="computeroutput"><span class="number">0</span> <span class="special">&lt;=</span>
  63           <span class="identifier">I</span> <span class="special">&lt;</span>
  64           <span class="identifier">N</span></code> or the program is ill formed.
  65         </p>
  66 <p>
  67           <span class="bold"><strong>Value</strong></span>: The type of the <code class="computeroutput"><span class="identifier">I</span></code>th
  68           element of <code class="computeroutput"><span class="identifier">T</span></code>. Equivalent
  69           to <code class="computeroutput"><a class="link" href="../../sequence/intrinsic/metafunctions/value_at.html" title="value_at"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at</span></code></a><span class="special">&lt;</span><span class="identifier">I</span><span class="special">,</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">type</span></code>.
  70         </p>
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