Generic Views

Abstract

Structural polymorphism allows for generic functions to be defined by induction over the structure of types. In Generic Haskell, the structure of a type is perceived as a nested sum of products. Over the last few years it has been shown that a great amount of generic programs can be defined in terms of this perception. Still, there are applications for which viewing data types as sums of products limits the expressiveness of Generic Haskell. As it turns out, different perceptions of the structure of types enable the definition of generic programs that are more efficient, more elegant, and more expressive. We show how these different perceptions, which we call generic views, can be implemented and used in Generic Haskell.