Using partial evaluation in support of portability, reusability, and maintainability

Abstract

Partial evaluation is ordinarily intended to be used to increase program efficiency. This paper shows how partial evaluation can be used in place of a preprocessor phase and of source-code templates (e.g. C++ templates or Ada generics). In this way it can be used to support portability features provided by a preprocessor, and the reusability provided by code templates, but with higher maintainability due to the simpler syntax required. The important mechanisms needed are: annotating variables and functions with an evaluation time, treating declarations as translation-time "executable" statements, treating user-defined types as translation-time variables, giving programmers control over the scope of symbols, and providing translation-time name binding. The effects of these changes on the size and complexity of a compiler are estimated. A translator for a language called "Safer_C" which supports these techniques has been implemented. Important existing C software is analyzed to evaluate the applicability of these techniques in replacing the preprocessor.