[Haskell-cafe] Types depending on tuples.

I'm doing some geometry in 2 and 3 dimensions. To do this, I've got Vector2d and Vector3d classes, which are basically just wrappers around 2 and 3-tuples of doubles: type Vector2d = (Double, Double) type Vector3d = (Double, Double, Double) I've also got a typeclass Vector so I can do polymorphic things on them: type Vector3d = (Double, Double, Double) (Ok, polymorphic thing). I now have a need to convert lists of Vector's to a list of lists of Doubles. I'd like that to be part of the Vector typeclass, but - well, declaring it is interesting. I can't just add a method "toLists :: a -> [Double]", because (according to ghc), there's no match between the expected type 'Double' and the actual type '[t1]'. Can I declare this typeclass?