Hi, So I'm trying the fun-deps example from http://www.haskell.org/hawiki/FunDeps and seeing if I can use it, but I can't really get things to work the way I want. The code follows below, and the error I get if I try to multiply 10 <*> (vector 10 [0..9]) is No instance for (MatrixProduct a (Vec b) c) arising from use of `<*>' at <interactive>:1:3-5 Probable fix: add an instance declaration for (MatrixProduct a (Vec b) c) In the definition of `it': it = 10 <*> (vector 10 ([0 .. 9])) import Array -- The elements and the size data Vec a = Vec (Array Int a) Int deriving (Show,Eq) type Matrix a = (Vec (Vec a)) class MatrixProduct a b c | a b -> c where (<*>) :: a -> b -> c instance (Num a) => MatrixProduct a (Vec a) (Vec a) where (<*>) num (Vec a s) = Vec (fmap (*num) a) s vector n elms = Vec (array (0,n-1) $ zip [0..n-1] elms) n