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The interpreter design pattern applied to the above composite list structure prescribes a coding pattern for list operations that is analogous to Scheme function template. It entails declaring an abstract method for each list operation in the abstract list class, IntList, and defining corresponding concrete methods in the concrete list subclasses: the empty list class, EmptyIntList, and the non-empty class, ConsIntList. The concrete method for EmptyIntList corresponds to the base case in the Scheme function template while the concrete method in ConstIntList corresponds to the recursive case by calling the same method on its rest.
The following is the coding template for the interpreter design pattern for IntList and its subclasses.
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