Re: [Haskell-cafe] lists as instances of a class?

10 Jul 2006


      On Mon, 10 Jul 2006, David Roundy wrote:
...
...
class Vec v where
   (.+.) :: v -> v -> v
...
instance Vec [Double] where
   xs .+. ys = zipWith (+) xs ys
...
instance Vec Double where
   x .+. y = x + y
P.S. This is with ghc 6.4.1.  And oddly enough, if you make the instance
instance Num a => Vec [a] where
   xs .+. ys = zipWith (+) xs ys
What about

instance Vec a => Vec [a] where
   (.+.) = zipWith (.+.)

?

Re: [Haskell-cafe] lists as instances of a class?

Henning Thielemann