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<div class="titlepage"><div><div><h3 class="title">
<a name="any.reference"></a>Reference</h3></div></div></div>
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<dt><span class="section"><a href="reference.html#any.ValueType"><span class="emphasis"><em>ValueType</em></span> requirements</a></span></dt>
<dt><span class="section"><a href="reference.html#header.boost.any.hpp">Header &lt;boost/any.hpp&gt;</a></span></dt>
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<a name="any.ValueType"></a><span class="emphasis"><em>ValueType</em></span> requirements</h4></div></div></div>
<p>Values are strongly informational objects for which
      identity is not significant, i.e. the focus is principally on
      their state content and any behavior organized around
      that. Another distinguishing feature of values is their
      granularity: normally fine-grained objects representing simple
      concepts in the system such as quantities.</p>
<p>As the emphasis of a value lies in its state not its
      identity, values can be copied and typically assigned one to
      another, requiring the explicit or implicit definition of a
      public copy constructor and public assignment operator. Values
      typically live within other scopes, i.e. within objects or
      blocks, rather than on the heap. Values are therefore normally
      passed around and manipulated directly as variables or through
      references, but not as pointers that emphasize identity and
      indirection.</p>
<p>The specific requirements on value types to be used in an
      <code class="computeroutput"><a href="../boost/any.html" title="Class any">any</a></code>
      are:</p>
<div class="itemizedlist"><ul type="disc" compact>
<li>A <span class="emphasis"><em>ValueType</em></span> is
          <span class="emphasis"><em>CopyConstructible</em></span> [20.1.3].</li>
<li>A <span class="emphasis"><em>ValueType</em></span> is
        optionally <span class="emphasis"><em>Assignable</em></span> [23.1]. The strong
        exception-safety guarantee is required for all forms of
        assignment.</li>
<li>The destructor for a
        <span class="emphasis"><em>ValueType</em></span> upholds the no-throw
        exception-safety guarantee.</li>
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<a name="header.boost.any.hpp"></a>Header &lt;<a href="../../../boost/any.hpp" target="_top">boost/any.hpp</a>&gt;</h4></div></div></div>
<pre class="synopsis"><span class="bold"><strong>namespace</strong></span> boost {
  <span class="bold"><strong>class</strong></span> <a href="../bad_any_cast.html" title="Class bad_any_cast">bad_any_cast</a>;
  <span class="bold"><strong>class</strong></span> <a href="../boost/any.html" title="Class any">any</a>;
  <span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> ValueType&gt; <span class="type">ValueType</span> <a href="../any_cast.html" title="Function any_cast">any_cast</a>(<span class="bold"><strong>const</strong></span> <a href="../boost/any.html" title="Class any">any</a> &amp;);
  <span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> ValueType&gt; <span class="type"><span class="bold"><strong>const</strong></span> ValueType *</span> <a href="../any_cast.html" title="Function any_cast">any_cast</a>(<span class="bold"><strong>const</strong></span> <a href="../boost/any.html" title="Class any">any</a> *);
  <span class="bold"><strong>template</strong></span>&lt;<span class="bold"><strong>typename</strong></span> ValueType&gt; <span class="type">ValueType *</span> <a href="../any_cast.html" title="Function any_cast">any_cast</a>(<a href="../boost/any.html" title="Class any">any</a> *);
}</pre>
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