Passing parameter types in programming languages with data abstractions

Recently designed programming languages provide mechanisms which support the use of procedural and data abstraction. In particular, most of them give the possibility of defining parametric data types. However this new feature affects procedure definitions, since parameters with partially specified type must be allowed. The paper tackles the problems generated by this generalization of procedures, by showing that parameter passing requires a pattern matcning mechanism. A proposal is made which keeps parameter passing and type checking separate, thus simplifying procedure calls. Furthermore the paper analyzes the ways in which operations can be associated with abstract data types and how operations can have access to the representation of their parameters. A construct for data abstractions is proposed, which achieves great generality by separating the two above aspects.