ml#type-t">t</a> option</span></code></dt><dd><p>meet two abstract elements</p></dd></dl><dl><dt class="spec value" id="val-diff"><a href="#val-diff" class="anchor"></a><code><span class="keyword">val</span> diff : <span><span>(<a href="index.html#type-t">t</a> <span>&#45;&gt;</span> <a href="index.html#type-t">t</a> <span>&#45;&gt;</span> <span><a href="index.html#type-t">t</a> list</span>)</span> option</span></code></dt><dd><p>substracts the second abstract element from the first (difference operator) if