I have observed the error message (ghci 6.4) Functional dependencies conflict between instance declarations: LocTest.hs:16:0: instance B S Bool LocTest.hs:22:0: instance (F f, B a b) => B (f a) (f b) when I changed in an instance from a simple type to a type with a parameter (i.e. from Int to (Int, Bool)). The following minimal program demonstrates the problem: an instance with type S (= T Float) conflicts with B (f a) (f b) whereas the comparable instance with data R (= R Float) does not. Is this intentional? How can it be avoided? Help is greatly appreciated! Andrew ---------------------------------------- class F f where m2 :: (a -> b -> c) -> f a -> f b -> f c --zipWith class B a b | a -> b where dist2 :: a -> a -> b instance B S Bool where -- line 16 dist2 a d = True instance B R Float where dist2 a d = 1 instance (F f, B a b) => B (f a) (f b) where -- line 22 dist2 a b = m2 dist2 a b data T f = T f type S = T Float data R = R Float