SRC Research Report 121
SRC Research Report 121
A frequent dilemma in programming language design is the choice between a language with a rich set of notations and a small, simple core language. We address this dilemma by proposing extensible grammars, a syntax-definition formalism for incremental language extensions and restrictions.
The translation of programs written in rich object languages into a small core language is defined via syntax-directed patterns. In contrast to macro-expansion and program-rewriting tools, our extensible grammars respect scoping rules. Therefore, we can introduce binding constructs while avoiding problems with unwanted name clashes.
We develop extensible grammars and illustrate their use by extending the lambda calculus with let-bindings, conditionals, and constructs from database programming languages, such as SQL query expressions. We then give a formal description of the underlying rules for parsing, transformation, and substitution. Finally, we sketch how these rules are exploited in an implementation of a generic, extensible parser package.
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