 <span class="identifier">b</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--&gt;</span> <span class="special">(</span><span class="identifier">a</span> <span class="special">|</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">A</span></pre>
<p>
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  Difference (<code class="computeroutput"><span class="identifier">a</span> <sp