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28<h2><span class="refentrytitle">Function get</span></h2>
29<p>boost::get &#8212; <p>Retrieves a value of a specified type from a given
30          <code class="computeroutput"><a href="boost/variant.html" title="Class template variant">variant</a></code>.</p></p>
31</div>
32<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
33<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis">
34<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> U, <span class="bold"><strong>typename</strong></span> T1, <span class="bold"><strong>typename</strong></span> T2, ..., <span class="bold"><strong>typename</strong></span> TN&gt; 
35  <span class="type">U *</span> get(<a href="boost/variant.html" title="Class template variant">variant</a>&lt;T1, T2, ..., TN&gt; * operand);
36<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> U, <span class="bold"><strong>typename</strong></span> T1, <span class="bold"><strong>typename</strong></span> T2, ..., <span class="bold"><strong>typename</strong></span> TN&gt; 
37  <span class="type"><span class="bold"><strong>const</strong></span> U *</span> get(<span class="bold"><strong>const</strong></span> <a href="boost/variant.html" title="Class template variant">variant</a>&lt;T1, T2, ..., TN&gt; * operand);
38<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> U, <span class="bold"><strong>typename</strong></span> T1, <span class="bold"><strong>typename</strong></span> T2, ..., <span class="bold"><strong>typename</strong></span> TN&gt; 
39  <span class="type">U &amp;</span> get(<a href="boost/variant.html" title="Class template variant">variant</a>&lt;T1, T2, ..., TN&gt; &amp; operand);
40<span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> U, <span class="bold"><strong>typename</strong></span> T1, <span class="bold"><strong>typename</strong></span> T2, ..., <span class="bold"><strong>typename</strong></span> TN&gt; 
41  <span class="type"><span class="bold"><strong>const</strong></span> U &amp;</span> get(<span class="bold"><strong>const</strong></span> <a href="boost/variant.html" title="Class template variant">variant</a>&lt;T1, T2, ..., TN&gt; &amp; operand);</pre></div>
42<div class="refsect1" lang="en">
43<a name="id2839339"></a><h2>Description</h2>
44<p>The <code class="computeroutput">get</code> function allows run-time checked,
45          type-safe retrieval of the content of the given
46          <code class="computeroutput"><a href="boost/variant.html" title="Class template variant">variant</a></code>. The function succeeds
47          only if the content is of the specified type <code class="computeroutput">U</code>, with
48          failure indicated as described below.</p>
49<p><span class="bold"><strong>Warning</strong></span>: After either
50          <code class="computeroutput">operand</code> or its content is destroyed (e.g., when the
51          given <code class="computeroutput"><a href="boost/variant.html" title="Class template variant">variant</a></code> is assigned a
52          value of different type), the returned reference is invalidated.
53          Thus, significant care and caution must be extended when handling
54          the returned reference.</p>
55<p><b xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision"><span class="term">Notes</span></b>:
56
57    As part of its guarantee of type-safety, <code class="computeroutput">get</code>
58        enforces <code class="computeroutput">const</code>-correctness. Thus, the specified type
59        <code class="computeroutput">U</code> must be <code class="computeroutput">const</code>-qualified whenever
60        <code class="computeroutput">operand</code> or its content is likewise
61        <code class="computeroutput">const</code>-qualified. The converse, however, is not required:
62        that is, the specified type <code class="computeroutput">U</code> may be
63        <code class="computeroutput">const</code>-qualified even when <code class="computeroutput">operand</code> and its
64        content are not.<br><b xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision"><span class="term">Returns</span></b>:
65
66    If passed a pointer, <code class="computeroutput">get</code> returns a pointer to
67        the value content if it is of the specified type <code class="computeroutput">U</code>;
68        otherwise, a null pointer is returned. If passed a reference,
69        <code class="computeroutput">get</code> returns a reference to the value content if it is of
70        the specified type <code class="computeroutput">U</code>; otherwise, an exception is thrown
71        (see below).<br><b xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision"><span class="term">Throws</span></b>:
72
73    Overloads taking a
74        <code class="computeroutput"><a href="boost/variant.html" title="Class template variant">variant</a></code> pointer will not
75        throw; the overloads taking a
76        <code class="computeroutput"><a href="boost/variant.html" title="Class template variant">variant</a></code> reference throw
77        <code class="computeroutput"><a href="bad_get.html" title="Class bad_get">bad_get</a></code> if the content is not of
78        the specified type <code class="computeroutput">U</code>.<br><b xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision"><span class="term">Rationale</span></b>:
79
80    While visitation via
81        <code class="computeroutput"><a href="apply_visitor.html" title="Function apply_visitor">apply_visitor</a></code>
82        is generally prefered due to its greater safety, <code class="computeroutput">get</code> may
83        may be more convenient in some cases due to its straightforward
84        usage.</p>
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