[Haskell-cafe] Polymorphic addition function with variable number of arguments?

[Johannes Waldmann]

> Can someone tell me why this is not working 

that "someone" is actually ghci:

Prelude> instance (Num a, Add a b) => Add (a -> b) where add x y = add (x + y)

<interactive>:8:30:
    Expecting one more argument to `Add (a -> b)'
    In the instance declaration for `Add (a -> b)'