Re: Type design question

G'day all. On Fri, Jul 25, 2003 at 03:48:15PM -0400, Dylan Thurston wrote:

Another approach is to make Universe a multi-parameter type class:

class (RealFrac a, Floating a) => Universe u a | u -> a where distanceVector :: u -> Vector a -> Vector a -> Vector a ...

Actually, this is a nice way to represent vector spaces, too: class (Num v, Fractional f) => VectorSpace vs v f | vs -> v f where scale :: vs -> f -> v -> v innerProduct :: vs -> v -> v -> f The reason why you may want to do this is that you may in general want different inner products on the same vectors, which result in different vector spaces. Cheers, Andrew Bromage