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) Please note this is just some testing code (the math people in here might be horrified by it ;), although any hints of how to do this in a clearer way are welcome. As side-note, does Haskell have some easy to use good linear algebra package for doing 2D, 3D and 4D math? Then I would not be writing any of this code, although I did find it useful for learning. Now without the funcdep a -> n in the type class declaration I get No instance for (Vector (Vector2 t) n) arising from use of `dot' at l:/Haskell/test/vector.hs:9:8-36 Possible fix: add an instance declaration for (Vector (Vector2 t) n) In the expression: dot (V2 1.0 2.0) (V2 3.0 4.0) In the definition of `test1': test1 = dot (V2 1.0 2.0) (V2 3.0 4.0) CAL seems to have the same problem, and without funcdeps I seem to be stuck in that language. PS(1): In the above I was using GHCI with extensions enabled. PS(2): IMHO CAL is in some aspects easier to get started than Haskell because of their nice Eclipse plugin and GEM Cutter environment for doing learning experiments. Thanks, Peter