Extensible programming with first-class cases

We present language mechanisms for polymorphic, extensible records and their exact dual, polymorphic sums with extensible first-class cases. These features make it possible to easily extend existing code with new cases. In fact, such extensions do not require any changes to code that adheres to a particular programming style. Using that style, individual extensions can be written independently and later be composed to form larger components. These language mechanisms provide a solution to the expression problem. We study the proposed mechanisms in the context of an implicitly typed, purely functional language PolyR. We give a type system for the language and provide rules for a 2-phase transformation: first into an explicitly typed -calculus with record polymorphism, and finally to efficient index-passing code. The first phase eliminates sums and cases by taking advantage of the duality with records. We implement a version of PolyR extended with imperative features and pattern matchin...

• Type: Conference
• Year: 2006
• Where: ICFP
• Authors: Matthias Blume, Umut A. Acar, Wonseok Chae
• Keywords: Extensible First-class Cases, ICFP 2006, Phase Eliminates Sums, Polymorphic Sums, Programming Languages