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Type Classes and Constraint Handling Rules

Kevin Glynn·Martin Sulzmann·Peter J. Stuckey
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Abstract

Type classes are an elegant extension to traditional, Hindley-Milner based typing systems. They are used in modern, typed languages such as Haskell to support controlled overloading of symbols. Haskell 98 supports only single-parameter and constructor type classes. Other extensions such as multi-parameter type classes are highly desired but are still not officially supported by Haskell. Subtle issues arise with extensions, which may lead to a loss of feasible type inference or ambiguous programs. A proper logical basis for type class systems seems to be missing. Such a basis would allow extensions to be characterised and studied rigorously. We propose to employ Constraint Handling Rules as a tool to study and develop type class systems in a uniform way.

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Kevin Glynn, Martin Sulzmann, Peter J. Stuckey. 2000-06-26. Type Classes and Constraint Handling Rules. https://arxiv.org/abs/cs/0006034

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