er
single values or intervals of the coordinates <code>h</code>, <code>c</code>, <code>l</code>. Their
interfaces are always designed such that <code>h</code>, <code>c</code>, <code>l</code> can take vector
arguments (as needed) but alternatively or additionally <code>h1</code>/<code>h2</code>,
<code>c1</code>/<code>c2</code>/<code>cmax</code>, and <code>l1</code>/<code>l2</code> can be specified. If so,
the latter coordinates overwrite the former.
</p>
<p><code>qualitative_hcl</code> distinguishes the unde