           Expression
                  </p>
                </th>
<th>
                  <p>
                    Semantics
                  </p>
                </th>
</tr></thead>
<tbody><tr>
<td>
                  <p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">clear_value</span><span class="special">&lt;</span><span class="identifier">Attrib</span><span class="special">&gt;::</span><span class="identifier">call</span