  </p>
                  </td>
<td>
                    <p>
                      Add one or more symbols (<code class="computeroutput"><span class="identifier">s1</span></code>...<code class="computeroutput"><span class="identifier">sN</span></code>) to <code class="computeroutput"><span class="identifier">sym</span></code>.
                      The associated data values of type <code class="computeroutput"><span class="identifier">T</span></code>
                      are default constructed.
          