./index.html#type-id">id</a></span></code></div></div><div class="odoc-spec"><div class="spec type anchored" id="type-t"><a href="#type-t" class="anchor"></a><code><span><span class="keyword">type</span> t</span></code></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-empty"><a href="#val-empty" class="anchor"></a><code><span><span class="keyword">val</span> empty : <a href="#type-t">t</a></span></code></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-add"