s="info-desc">
<p><code class="code"><span class="constructor">List</span>.iter2&nbsp;f&nbsp;[a1;&nbsp;...;&nbsp;an]&nbsp;[b1;&nbsp;...;&nbsp;bn]</code> calls in turn
   <code class="code">f&nbsp;a1&nbsp;b1;&nbsp;...;&nbsp;f&nbsp;an&nbsp;bn</code>.
   Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the two lists are determined
   to have different lengths.</p>
</div>
</div>

<pre><span id="VALmap2"><span class="keyword">val</span> map2</span> : <code class="type">f:('a -