subtraction</strong></span></em></span> implemented
          by <code class="computeroutput"><span class="identifier">subtract</span></code> and <code class="computeroutput"><span class="keyword">operator</span> <span class="special">-=</span></code>
          are identical for all Set-types of the <span class="bold"><strong>icl</strong></span>.
        </p>
<p>
          For Map-types, <code class="computeroutput"><span class="identifier">erase</span></code> provides
          the <span class="bold"><stro