+ex relational::subs(const lst & ls, const lst & lr, bool no_pattern) const
+{
+ const ex & subsed_lh = lh.subs(ls, lr, no_pattern);
+ const ex & subsed_rh = rh.subs(ls, lr, no_pattern);
+
+ if (!are_ex_trivially_equal(lh, subsed_lh) || !are_ex_trivially_equal(rh, subsed_rh))
+ return relational(subsed_lh, subsed_rh, o).basic::subs(ls, lr, no_pattern);
+ else
+ return basic::subs(ls, lr, no_pattern);
+}
+