> <span><span class="type-var">'b</span> <a href="index.html#type-t">t</a></span> <span>&#45;&gt;</span> <span><span><span>(<span class="type-var">'a</span> * <span class="type-var">'b</span>)</span> <a href="index.html#type-t">t</a></span> <a href="index.html#module-Or_unequal_lengths">Or_unequal_lengths</a>.t</span></code></dt><dt class="spec value" id="val-zip_exn"><a href="#val-zip_exn" class="anchor"></a><code><span class="keyword">val</span> zip_exn : <span><span class="type-var">'a</span> <a href="in