="anchor"></a><code><span class="keyword">val</span> is_empty : <a href="index.html#type-t">t</a> <span>&#45;&gt;</span> bool</code></dt><dt class="spec value" id="val-mem"><a href="#val-mem" class="anchor"></a><code><span class="keyword">val</span> mem : <a href="index.html#type-elt">elt</a> <span>&#45;&gt;</span> <a href="index.html#type-t">t</a> <span>&#45;&gt;</span> bool</code></dt><dt class="spec value" id="val-add"><a href="#val-add" class="anchor"></a><code><span class="keyword">val</span> add : <a 