<p>Allow the printer to choose which of the given document to render.
Choices must be semantically equivalent.</p></div></div><div class="spec val" id="val-fail"><a href="#val-fail" class="anchor"></a><div class="def val"><code><span class="keyword">val </span>fail : <a href="index.html#type-t">t</a></code></div><div class="doc"><p>Unit for the choice function.</p></div></div><div class="spec val" id="val-empty"><a href="#val-empty" class="anchor"></a><div class="def val"><code><span class="keyword">val </s