THE FORMAL SPECIFICATION OF ABSTRACT-DATA-TYPES AND THEIR IMPLEMENTATION IN FORTRAN-90 - IMPLEMENTATION ISSUES CONCERNING THE USE OF POINTERS

In this paper we continue our investigation into the development of co mputational-science software based on the identification and formal sp ecification of Abstract Data Types (ADTs) and their implementation in Fortran 90. In particular, we consider the consequences of using point ers when implementing a formally specified ADT in Fortran 90. Our aim is to highlight the resulting conflict between the goal of information hiding, which is central to the ADT methodology, and the space effici ency of the implementation. We show that the issue of storage recovery cannot be avoided by the ADT user, and present a range of implementat ions of a simple ADT to illustrate various approaches towards satisfac tory storage management. Finally, we propose a set of guidelines for i mplementing ADTs using pointers in Fortran 90. These guidelines offer a way gracefully to provide disposal operations in Fortran 90. Such an approach is desirable since Fortran 90 does not provide automatic gar bage collection which is offered by many object-oriented languages inc luding Eiffel, Java, Smalltalk, and Simula.