%0 Journal Article %J Computer Languages %D 1981 %T Implementation of language enhancements %A Zelkowitz, Marvin V %A Lyle,James R. %K Compiler design %K Data abstraction %K Language extensions %K specifications %X 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. %B Computer Languages %V 6 %P 139 - 153 %8 1981/// %@ 0096-0551 %G eng %U http://www.sciencedirect.com/science/article/pii/0096055181900266 %N 3–4 %R 10.1016/0096-0551(81)90026-6