ier">M</span>
</pre>
<p>
      </p>
<p>
        For <code class="computeroutput"><span class="identifier">Sets</span></code>, the <span class="emphasis"><em><span class="bold"><strong>key types</strong></span></em></span> defined for maps are identical
        with the set types themselves. So the distinction between the function groups
        <span class="emphasis"><em><span class="bold"><strong>selection by key</strong></span></em></span> and
        <span class="emphasis"><em><span class="bold"><strong>