| </span><span><span class="constructor">Empty</span></span></code></li><li id="type-singleton_or_more.Singleton" class="def variant constructor anchored"><a href="#type-singleton_or_more.Singleton" class="anchor"></a><code><span>| </span><span><span class="constructor">Singleton</span> <span class="keyword">of</span> <span class="type-var">'a</span></span></code></li><li id="type-singleton_or_more.More" class="def variant constructor anchored"><a href="#type-singleton_or_more.More" class="anchor"></a><code