I have a typeclass related question that I have been puzzling over. In a library I am working on, I have a series of functions for converting values to Renderables: | labelToRenderable :: Label -> Renderable | legendToRenderable :: Legend -> Renderable | axisToRenderable :: Axis v -> Renderable | layoutToRenderable :: Layout x y -> Renderable These names are overloaded for convenience via a typeclass: | class ToRenderable a where | toRenderable :: a -> Renderable | | instance ToRenderable Label where | toRenderable = labelToRenderable | ... But some recent changes mean that Renderable needs to become a type constructor, and the functions now product different types: | labelToRenderable :: Label -> Renderable () | legendToRenderable :: Legend -> Renderable String | axisToRenderable :: Axis v -> Renderable () | layoutToRenderable :: Layout x y a -> Renderable a Is there a nice way to overload a "toRenderable" function for these? Something like this is possible: | class ToRenderable a b where | toRenderable :: a -> Renderable b But the above is, I think, too general for my needs. I don't want to be able to generate Renderables of different type b for a single input type a. Also, MPTC take me out of the world of haskell 98, which I was trying to avoid. Am I missing something simple? Any pointers would be much appreciated. Tim