Type classes in Haskell

Abstract

This article defines a set of type inference rules for resolving overloading introduced by type classes, as used in the functional programming language Haskell. Programs including type classes are transformed into ones which may be typed by standard Hindley-Milner inference rules. In contrast to other work on type classes, the rules presented here relate directly to Haskell programs. An innovative aspect of this work is the use of second-order lambda calculus to record type information in the transformed program.