span class="keyword">val</span> filter_diff : <span><a href="#type-t">t</a> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-internal_constr">internal_constr</a> <span class="arrow">&#45;&gt;</span></span> <span><span>(<a href="#type-t">t</a> * <a href="../../Tools/VarSet/index.html#type-t">Tools.VarSet.t</a>)</span> <a href="../../Consistency/index.html#type-t">Consistency.t</a></span></span></code></div><div class="spec-doc"><p>same as filter but also return a set of variables that had the