#VALmap2"><code class="code"><span class="constructor">List</span>.map2</code></a><code class="code">&nbsp;f&nbsp;l1&nbsp;l2)</code>, but is tail-recursive and
   more efficient.</p>
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<pre><span id="VALfold_left2"><span class="keyword">val</span> fold_left2</span> : <code class="type">f:('a -&gt; 'b -&gt; 'c -&gt; 'a) -&gt; init:'a -&gt; 'b list -&gt; 'c list -&gt; 'a</code></pre><div class="info ">
<div class="info-desc">
<p><code class="code"><span class="constructor">List</span>.fold_left2&