@Override
 public Value evaluate(final Map<IdentifierNode, Value> variables) {
   final Value value1 = this.lhs.evaluate(variables);
   final Value value2 = this.rhs.evaluate(variables);
   return value1.lessEqual(value2);
 }
 @Override
 public Value evaluate(Map<Ident, Value> variables) {
   Value lhs = this.lhs.evaluate(variables);
   Value rhs = this.rhs.evaluate(variables);
   return lhs.sub(rhs);
 }