nchor"></a><code><span class="keyword">val</span> empty : <span><span class="type-var">'a</span> <a href="index.html#type-t">t</a></span></code></dt><dt class="spec value" id="val-is_empty"><a href="#val-is_empty" class="anchor"></a><code><span class="keyword">val</span> is_empty : <span><span class="type-var">'a</span> <a href="index.html#type-t">t</a></span> <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</spa