This problem is about explicit references.
1. In the previous problem, we enhanced the Reflang language to allow reference arithmetic. Add a new predicate expression, rarith?, to check if an expression uses reference arithmetic during its evaluation.
The expression rarith? follows the grammar shown here:

The following interaction log illustrates the semantics of this expression:

2. Write an example Reflang program that has reference arithmetic as its subexpression, but that subexpression is not executed during its evaluation. Your program must use at least one lambda expression.