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<div class="section" lang="en">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="fusion.sequences.containers.cons"></a><a href="cons.html" title="cons">cons</a></h4></div></div></div>
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<a name="fusion.sequences.containers.cons.description"></a><h5>
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<a name="id978120"></a>
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<a href="cons.html#fusion.sequences.containers.cons.description">Description</a>
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</h5>
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<p>
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<code class="computeroutput"><span class="identifier">cons</span></code> is a simple <a href="../concepts/forward_sequence.html" title="Forward
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Sequence">Forward Sequence</a>.
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It is a lisp style recursive list structure where <code class="computeroutput"><span class="identifier">car</span></code>
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is the <span class="emphasis"><em>head</em></span> and <code class="computeroutput"><span class="identifier">cdr</span></code>
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is the <span class="emphasis"><em>tail</em></span>: usually another cons structure or <code class="computeroutput"><span class="identifier">nil</span></code>: the empty list. Fusion's <a href="list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a> is built on top of this more
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primitive data structure. It is more efficient than <a href="vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a> when the target sequence
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is constructed piecemeal (a data at a time). The runtime cost of access
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to each element is peculiarly constant (see <a href="../../notes.html#fusion.notes.recursive_inlined_functions">Recursive
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Inlined Functions</a>).
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</p>
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<a name="fusion.sequences.containers.cons.header"></a><h5>
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<a name="id978250"></a>
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<a href="cons.html#fusion.sequences.containers.cons.header">Header</a>
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</h5>
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<pre class="programlisting">
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<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">sequence</span><span class="special">/</span><span class="identifier">container</span><span class="special">/</span><span class="identifier">list</span><span class="special">/</span><span class="identifier">cons</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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</pre>
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<a name="fusion.sequences.containers.cons.synopsis"></a><h5>
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<a name="id978351"></a>
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<a href="cons.html#fusion.sequences.containers.cons.synopsis">Synopsis</a>
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</h5>
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<pre class="programlisting">
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<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Car</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Cdr</span> <span class="special">=</span> <span class="identifier">nil</span><span class="special">></span>
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<span class="keyword">struct</span> <span class="identifier">cons</span><span class="special">;</span>
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</pre>
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<a name="fusion.sequences.containers.cons.template_parameters"></a><h5>
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<a name="id978446"></a>
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<a href="cons.html#fusion.sequences.containers.cons.template_parameters">Template
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parameters</a>
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</h5>
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<div class="informaltable"><table class="table">
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<colgroup>
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<col>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>
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<p>
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Parameter
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</p>
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</th>
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<th>
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<p>
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Description
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</p>
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</th>
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<th>
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<p>
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Default
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</p>
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</th>
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</tr></thead>
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<tbody>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">Car</span></code>
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</p>
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</td>
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<td>
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<p>
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Head type
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</p>
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</td>
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<td>
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<p>
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">Cdr</span></code>
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</p>
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</td>
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<td>
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<p>
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Tail type
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</p>
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</td>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">nil</span></code>
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</p>
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</td>
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</tr>
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</tbody>
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</table></div>
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<a name="fusion.sequences.containers.cons.model_of"></a><h5>
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<a name="id978582"></a>
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<a href="cons.html#fusion.sequences.containers.cons.model_of">Model of</a>
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</h5>
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<div class="itemizedlist"><ul type="disc"><li><a href="../concepts/forward_sequence.html" title="Forward
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Sequence">Forward Sequence</a></li></ul></div>
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<div class="variablelist">
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<p class="title"><b>Notation</b></p>
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<dl>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">nil</span></code></span></dt>
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<dd>
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An empty <code class="computeroutput"><span class="identifier">cons</span></code>
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</dd>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">C</span></code></span></dt>
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<dd>
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A <code class="computeroutput"><span class="identifier">cons</span></code> type
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</dd>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">l</span></code>,
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<code class="computeroutput"><span class="identifier">l2</span></code></span></dt>
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<dd>
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Instances of <code class="computeroutput"><span class="identifier">cons</span></code>
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</dd>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">car</span></code></span></dt>
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<dd>
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An arbitrary data
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</dd>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">cdr</span></code></span></dt>
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<dd>
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Another <code class="computeroutput"><span class="identifier">cons</span></code> list
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</dd>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">s</span></code></span></dt>
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<dd>
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A <a href="../concepts/forward_sequence.html" title="Forward
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Sequence">Forward
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Sequence</a>
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</dd>
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<dt><span class="term"><code class="computeroutput"><span class="identifier">N</span></code></span></dt>
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<dd>
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An <a href="http://www.boost.org/libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
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Integral Constant</a>
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</dd>
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</dl>
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</div>
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<a name="fusion.sequences.containers.cons.expression_semantics"></a><h5>
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<a name="id996285"></a>
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<a href="cons.html#fusion.sequences.containers.cons.expression_semantics">Expression
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Semantics</a>
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</h5>
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<p>
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Semantics of an expression is defined only where it differs from, or is
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not defined in <a href="../concepts/forward_sequence.html" title="Forward
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Sequence">Forward
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Sequence</a>.
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</p>
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<div class="informaltable"><table class="table">
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<colgroup>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>
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<p>
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Expression
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</p>
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</th>
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<th>
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<p>
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Semantics
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</p>
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</th>
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</tr></thead>
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<tbody>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">nil</span><span class="special">()</span></code>
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</p>
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</td>
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<td>
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<p>
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Creates an empty list.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">C</span><span class="special">()</span></code>
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</p>
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</td>
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<td>
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<p>
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Creates a cons with default constructed elements.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">C</span><span class="special">(</span><span class="identifier">car</span><span class="special">)</span></code>
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</p>
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</td>
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<td>
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<p>
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Creates a cons with <code class="computeroutput"><span class="identifier">car</span></code>
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head and default constructed tail.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">C</span><span class="special">(</span><span class="identifier">car</span><span class="special">,</span>
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<span class="identifier">cdr</span><span class="special">)</span></code>
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</p>
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</td>
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<td>
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<p>
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Creates a cons with <code class="computeroutput"><span class="identifier">car</span></code>
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head and <code class="computeroutput"><span class="identifier">cdr</span></code> tail.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">C</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code>
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</p>
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</td>
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<td>
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<p>
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Copy constructs a cons from a <a href="../concepts/forward_sequence.html" title="Forward
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Sequence">Forward
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Sequence</a>, <code class="computeroutput"><span class="identifier">s</span></code>.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">l</span> <span class="special">=</span>
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<span class="identifier">s</span></code>
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</p>
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</td>
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<td>
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<p>
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Assigns to a cons, <code class="computeroutput"><span class="identifier">l</span></code>,
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from a <a href="../concepts/forward_sequence.html" title="Forward
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Sequence">Forward
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Sequence</a>, <code class="computeroutput"><span class="identifier">s</span></code>.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><a href="../intrinsics/functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">l</span><span class="special">)</span></code>
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</p>
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</td>
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<td>
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<p>
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The Nth element from the beginning of the sequence; see <a href="../intrinsics/functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a>.
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</p>
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</td>
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</tr>
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</tbody>
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</table></div>
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<div class="sidebar"><p>
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<span class="inlinemediaobject"><img src="../../../images/note.png" alt="note"></span> <code class="computeroutput"><a href="../intrinsics/functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">l</span><span class="special">)</span></code> is
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provided for convenience and compatibility with the original <a href="http://www.boost.org/libs/tuple/doc/tuple_users_guide.html" target="_top">Boost.Tuple</a>
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library, despite <code class="computeroutput"><span class="identifier">cons</span></code> being
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a <a href="../concepts/forward_sequence.html" title="Forward
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Sequence">Forward Sequence</a>
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only (<code class="computeroutput"><span class="identifier">at</span></code> is supposed to
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be a <a href="../concepts/random_access_sequence.html" title="Random
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Access Sequence">Random
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Access Sequence</a> requirement). The runtime complexity of <a href="../intrinsics/functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a> is constant (see <a href="../../notes.html#fusion.notes.recursive_inlined_functions">Recursive
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Inlined Functions</a>).
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</p></div>
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<a name="fusion.sequences.containers.cons.example"></a><h5>
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<a name="id996864"></a>
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<a href="cons.html#fusion.sequences.containers.cons.example">Example</a>
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</h5>
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<pre class="programlisting">
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<span class="identifier">cons</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">cons</span><span class="special"><</span><span class="keyword">float</span><span class="special">></span> <span class="special">></span> <span class="identifier">l</span><span class="special">(</span><span class="number">12</span><span class="special">,</span> <span class="identifier">cons</span><span class="special"><</span><span class="keyword">float</span><span class="special">>(</span><span class="number">5.5f</span><span class="special">));</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <a href="../intrinsics/functions/at_c.html" title="at_c"><code class="computeroutput"><span class="identifier">at_c</span></code></a><span class="special"><</span><span class="number">0</span><span class="special">>(</span><span class="identifier">l</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <a href="../intrinsics/functions/at_c.html" title="at_c"><code class="computeroutput"><span class="identifier">at_c</span></code></a><span class="special"><</span><span class="number">1</span><span class="special">>(</span><span class="identifier">l</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
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</pre>
|
||
</div>
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<td align="left"></td>
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<td align="right"><small>Copyright © 2001-2007 Joel de Guzman, Dan Marsden, Tobias
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Schwinger</small></td>
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