lass="arrow">&#45;&gt;</span></span>
  <span><span><span class="type-var">'b</span> <a href="#type-t">t</a></span> <span class="arrow">&#45;&gt;</span></span>
  <span><span class="label">eq</span>:<span>(<span><span class="type-var">'a</span> <span class="arrow">&#45;&gt;</span></span> <span><span class="type-var">'b</span> <span class="arrow">&#45;&gt;</span></span> bool)</span> <span class="arrow">&#45;&gt;</span></span>
  <span><span>(<span><span>(<a href="#type-key">key</a> * <span>[&gt; <span>`Left of 