de> of the last pair has a special marker. This is the empty list, also called nil or null. It is printed as <code>()</code>. The predicate <code>null?</code> checks if a list is empty (is nil).</li>
<li>Lisp has a procedure called <code>list</code>, which is just an abbreviation for the nested pairs.</li>
</ul>
<h3 id="1.3" class="anchor">
<a class="anchor__link link" href="#1.3" aria-hidden="true">#</a> Mapping lists
</h3>
<ul>
<li>It is common to write a procedure that does the same thing to each item in