n></code></div><div class="spec-doc"><p><code>on cond attr</code> is <code>attr</code> if <code>cond</code> is <code>true</code> and <code>empty</code> otherwise.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-on_some"><a href="#val-on_some" class="anchor"></a><code><span><span class="keyword">val</span> on_some : <span><span><a href="#type-t">t</a> option</span> <span class="arrow">&#45;&gt;</span></span> <a href="#type-t">t</a></span></code></div><div class="spec-doc"><p><c