private void checkSatisfiable(RexNode e, String s) {
   assertTrue(SubstitutionVisitor.mayBeSatisfiable(e));
   final RexNode simple = SubstitutionVisitor.simplify(rexBuilder, e);
   assertEquals(s, simple.toString());
 }
 private void checkNotSatisfiable(RexNode e) {
   assertFalse(SubstitutionVisitor.mayBeSatisfiable(e));
   final RexNode simple = SubstitutionVisitor.simplify(rexBuilder, e);
   assertFalse(RexLiteral.booleanValue(simple));
 }