Implementation of Language Enhancements

Data abstractions have been proposed as a mean,, to enhance program modularity. The implementation of such ne~ features to an existing language is typically handled bx either rewriting large portions of an existing compiler or by using a preprocessor 1o translate the extensions into the standard language. The first technique is expensixe to implement while the latter is usuall 3 slov, and clumsy to use. In this paper a data abstraction addition to PL 1 > described and a hybrid implementation is gixen. A minimal set of primitive features are added to the compiler and the other extensions are added via an internal macro processor that expand, the ne~ syntax inlo the existing language.