code class="code">a</code> in the list of
    pairs <code class="code">l</code>. That is,
    <code class="code">assoc_opt&nbsp;a&nbsp;[&nbsp;...;&nbsp;(a,b);&nbsp;...]&nbsp;=&nbsp;Some&nbsp;b</code>
    if <code class="code">(a,b)</code> is the leftmost binding of <code class="code">a</code> in list <code class="code">l</code>.
    Returns <code class="code">None</code> if there is no value associated with <code class="code">a</code> in the
    list <code class="code">l</code>.</p>
</div>
<ul class="info-a