(moved to Cafe) At 2002-03-19 03:33, dominic.j.steinitz@britishairways.com wrote:

I've already declared Gaussian a as being of class Eq so why does it need to be told again?

No you haven't. You've declared 'Eq a => Eq (Gaussian a)' -- 'Gaussian a' is Eq if 'a' is, not 'Eq (Gaussian a)'. Try this instance Eq a => Num (Gaussian a) where ... ...and actually looking at your code, I think you want this: instance Num a => Num (Gaussian a) where ... -- Ashley Yakeley, Seattle WA