Hi there. If someone can tell me why I am getting type ambiguity in the following code: class (Ord s, Num s) => Scalar s where zero :: s class Metric m where delta :: Scalar s => m -> m -> s (=~) :: m -> m -> Bool (/~) :: m -> m -> Bool (=~) a b = (delta a b) <= zero (/~) a b = not (a =~ b) I will scream. The error I get compiling is: Ambiguous type variable `s' in the constraint: `Scalar s' arising from a use of `delta' at test.hs:13:23-31 Probable fix: add a type signature that fixes these type variable(s) If I change "Scalar" to "Num", and "zero" to "0" within the class "Metric", then it works. I don't get it. "zero" is defined in the "Scalar" class, and "delta" returns a Scalar, and Scalar derives "Ord", so where's the ambiguity? Thanks. I will understand Haskell eventually... =) Make the switch to the world's best email. Get the new Yahoo!7 Mail now. www.yahoo7.com.au/worldsbestemail