e><span class="keyword">val</span> volume : <a href="index.html#type-t">t</a> <span>&#45;&gt;</span> float</code></dt><dd><p>computes the volume of an abstract element</p></dd></dl></section><section><header><h2 id="set-theoretic-operations"><a href="#set-theoretic-operations" class="anchor"></a>Set-theoretic operations</h2></header><dl><dt class="spec value" id="val-join"><a href="#val-join" class="anchor"></a><code><span class="keyword">val</span> join : <a href="index.html#type-t">t</a> <span>&#45;&gt;</