><p>computes the volume of an abstract element</p></div></div><h2 id="set-theoretic-operations"><a href="#set-theoretic-operations" class="anchor"></a>Set-theoretic operations</h2><div class="odoc-spec"><div class="spec value anchored" id="val-join"><a href="#val-join" class="anchor"></a><code><span><span class="keyword">val</span> join : <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>