It looks like you've given the Vector2D type an argument, but not used
one for the BasicVector instance.
On Thu, May 20, 2010 at 6:35 PM, Walck, Scott
Hi folks,
I'm trying to make doubles and triples act like vectors, as in
(3,4) <+> (7,8) ==> (10,12) (3,2,1) <+> (9,8,7) ==> (12,10,8) 6 *> (1,2,3) ==> (6,12,18)
I thought I should make a type class so that I could use <+> for both double addition and triple addition, and *> for both double and triple scalar multiplication. (Some of this functionality is provided by NumericPrelude, but I didn't need all of that, and I hoped this would be simple to write.) The code below gives the error
NewVectorShort.hs:19:0: Type synonym `Vector2D' should have 1 argument, but has been given 0 In the instance declaration for `BasicVector Vector2D' Failed, modules loaded: none.
I don't understand how what I'm trying to do is different from, say, the Monad instance for Maybe. (Maybe a) is a type, and (Vector2D a) is a type.
Thanks,
Scott
{-# LANGUAGE TypeSynonymInstances #-}
infixl 6 <+> infixl 6 <-> infixl 7 *> infixl 7 <*
class BasicVector v where (<+>) :: v a -> v a -> v a (<->) :: v a -> v a -> v a (*>) :: Num a => a -> v a -> v a (<*) :: Num a => v a -> a -> v a v1 <-> v2 = v1 <+> fromInteger (-1) *> v2 v1 <* c = c *> v1 c *> v1 = v1 <* c
type Vector2D a = (a,a)
instance BasicVector Vector2D where (ax,ay) <+> (bx,by) = (ax+bx,ay+by) c *> (ax,ay) = (c*ax,c*ay)
_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners