Re: [Haskell-cafe] Functional dependencies *not* part of the next Haskell standard?

On Thu, 12 Jul 2007, peterv wrote:

I tried to do something in CAL that I could not solve without functional dependencies. In their support forum, it got mentioned that func.deps propably won't make into the next Haskell standard... Any comments on that?

Now, the thing I tried to solve was:

data Vector2 a = Num a => V2 a a

class Vector a n | a -> n where dot :: a -> a -> n

instance Num a => Vector (Vector2 a) a where dot (V2 x1 y1) (V2 x2 y2) = x1 * x2 + y1 * y2

test1 = dot (V2 1.0 2.0) (V2 3.0 4.0)

class Vector v where dot :: Num a => v a -> v a -> a instance Vector Vector2 where dot (V2 x1 y1) (V2 x2 y2) = x1 * x2 + y1 * y2 This will work satisfyingly if you don't plan a larger type class hierarchy.