Pragmatic Aspects of Reusable Program Generators

When writing a program generator requires considerable intellectual effort, it is valuable to amortize that effort by using the generator to build more than one application. When a program generator serves multiple clients, however, the implementor must address pragmatic questions that implementors of single-use program generators can ignore. In how many languages should generated code be written? How should code be packaged? What should the interfaces to the client code look like? How should a user control variations? This paper elaborates on these questions by means of case studies of the New Jersey Machine-Code Toolkit, the λ-RTL Translator, and the ASDL program generator. It is hoped that the paper will stimulate the development of better techniques. Most urgently needed are a standard way to support multiple target languages and a simple, clear way to control interfaces to generated code.