Reenement in a Type Extension Context

This paper extends the methods of the reenement calculi to allow the derivation of an Oberon implementation. The use of records, pointers, opaque types and type extension distinguishes this work from previous examples. A case study for a stack abstract data type illustrates the method, which involves three data reenement steps. Firstly, a sequence of integers is reened to a sequence of integer records with pointers. Secondly, the sequence of records is reened to a linked list accessed through a start pointer. Finally, this is reened to a generic implementation that is close to Oberon code. Pointers are facilitated by declaring an explicit local data store for each stack variable. The advantage of Oberon over Modula-2 is the ability to separate the nal code into two modules | a generic stack that maintains the linked list property and an integer instantiation of the stack, using type extension. This separation of concerns (isolation of the linked data structure properties) is the main beneet of the approach.