Type Classes with Functional Dependencies

  • Mark P. Jones
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1782)

Abstract

Type classes in Haskell allow programmers to define functions that can be used on a set of different types, with a potentially different implementation in each case. For example, type classes are used to support equality and numeric types, and for monadic programming. A commonly requested extension to support ‘multiple parameters’ allows a more general interpretation of classes as relations on types, and has many potentially useful applications. Unfortunately, many of these examples do not work well in practice, leading to ambiguities and inaccuracies in inferred types and delaying the detection of type errors.

This paper illustrates the kind of problems that can occur with multiple parameter type classes, and explains how they can be resolved by allowing programmers to specify explicit dependencies between the parameters. A particular novelty of this paper is the application of ideas from the theory of relational databases to the design of type systems.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Mark P. Jones
    • 1
  1. 1.Department of Computer Science and EngineeringOregon Graduate Institute of Science and TechnologyBeavertonUSA

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