a Department of Computer Science, University of Maryland, College Park, MD 20742, U.S.A.
b Institute for Computer Sciences and Technology National Bureau of Standards, Washington, DC, U.S.A.
Abstract:
Data abstractions have been proposed as a means to enhance program modularity. The implementation of such new features to an existing language is typically handled by either rewriting large portions of an existing compiler or by using a preprocessor to translate the extensions into the standard language. The first technique is expensive to implement while the latter is usually slow and clumsy to use. In this paper a data abstraction addition to PL 1 is described and a hybrid implementation is given. A minimal set of primitive features are added to the compiler and the other extensions are added via an internal macro processor that expands the new syntax into the existing language.