A rationale for semantically enhanced library languages

This paper presents the rationale for a novel approach to providing expressive, teachable, maintainable, and cost-effective special-purpose languages: A Semantically Enhanced Library Language (a SEL language or a SELL) is a dialect created by supersetting a language using a library and then subsetting the result using a tool that “understands” the syntax and semantics of both the underlying language and the library. The resulting language can be about as expressive as a specialpurpose language and provide as good semantic guarantees as a special-purpose language. However, a SELL can rely on the tool chain and user community of a major generalpurpose programming language. The examples of SELLs presented here (Safe C++, Parallel C++, and Real-time C++) are based on C++ and the Pivot program analysis and transformation infrastructure. As part of the rationale, the paper discusses practical problems with various popular approaches to providing special-purpose features, such as compiler options and preprocessors.