utput"><span class="identifier">optional</span></code>
                    instance and leave it uninitialized.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">variant</span><span class="special">&lt;</span><span class="identifier">T1</span><span class="special">,</span>
                    <span class="identifier">T2</span><span cla