    </td>
</tr>
<tr>
<td>
                    <p>
                      <code class="computeroutput"><span class="identifier">sym</span><span class="special">.</span><span class="identifier">add</span><span class="special">(</span><span class="identifier">s1</span><span class="special">,</span>
                      <span class="identifier">d1</span><span class="special">)(</span><span class="identifier">s2</span><span class="special">,</span>
                      <span class="identifier">d2</span><span cl