an>:int <span class="arrow">&#45;&gt;</span></span>
  <span><span class="optlabel">?header</span>:bool <span class="arrow">&#45;&gt;</span></span>
  <span><span class="optlabel">?fmt</span>:<span>(<span><a href="#type-elt">elt</a> <span class="arrow">&#45;&gt;</span></span> string)</span> <span class="arrow">&#45;&gt;</span></span>
  <span><a href="#type-arr">arr</a> <span class="arrow">&#45;&gt;</span></span>
  unit</span></code></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-ab