pan> : <code class="type">'a -&gt; ('a * 'b) list -&gt; 'b</code></pre><div class="info">
<code class="code">assoc a l</code> returns the value associated with key <code class="code">a</code> in the list of
   pairs <code class="code">l</code>. That is,
   <code class="code">assoc a [ ...; (a,b); ...] = 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>.
   Raise <code class="code"><span class="constructor">Not_found</spa