lass template.
</p>

<p>
A type <code>S</code> is a <i>holder specifier</i> if:
<ol>
  <li>One of the following conditions is satisfied:
    <ol type="a">
      <li><a href="#is_holder"><code>is_holder&lt;S&gt;::type</code></a> is
      <a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::true_</code></a>,</li>
      <li><code>S</code> is of the form <a href="#holder_construct"><code>holder&lt;S'&gt;</code></a>.</li>
    </ol>
  </li>
  <li><code>S</code>, or <code>S'</code> if (b) applies, is a