Implementing Haskell overloading

Haskell overloading poses new challenges for compiler writers. Until recently there have been no implementations of it which have had acceptable performance; users have been adviced to avoid it by using explicit type signatures. This is unfortunate since it does not promote the reusability of software components that overloading really offers. In this paper we describe a number of ways to improve the speed of Haskell overloading. None of the techniques described here is particularly exciting or complicated, but taken together they may give an order of magnitude speedup for some programs using overloading. The techniques fall into two categories: speeding up overloading, and avoiding overloading altogether. For the second kind we borrow some techniques from partial evaluation. There does not seem to be a single implementation technique which is a panacea; but a number of different ones have to be put together to get decent performance. 1 Introduction Haskell, [Hud92], introduces a new ..