"> (</code><a href="List.html#VALmap2"><code class="code"><span class="constructor">List</span>.map2</code></a><code class="code"> f l1 l2)</code>, but is tail-recursive and
   more efficient.<br>
</div>
<pre><span id="VALfold_left2"><span class="keyword">val</span> fold_left2</span> : <code class="type">('a -&gt; 'b -&gt; 'c -&gt; 'a) -&gt; 'a -&gt; 'b list -&gt; 'c list -&gt; 'a</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.fold_left2 f a [b1; ...; bn] [c1; ...; c