>t</a></span></code></div></div><div class="odoc-spec"><div class="spec value" id="val-union_prefer_left" class="anchored"><a href="#val-union_prefer_left" class="anchor"></a><code><span><span class="keyword">val</span> union_prefer_left : <span><a href="#type-t">t</a> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-t">t</a> <span class="arrow">&#45;&gt;</span></span> <a href="#type-t">t</a></span></code></div><div class="spec-doc"><p>in case an element with the same rank is present both in