Generating a set of pattern matched function declarations in an instance declaration (see below) causes a "Conflicting definition error" upon linking. instance (G a) => F (Tree a) where f (Leaf x) = g x f (Branch x y) = g x `h` g y rewritten as instance (G a) => F (Tree a) where f x = case x of Leaf x -> g x Branch x y -> g x `h` g y works. I suspect that it has to do with the "level" the source code is considered. I.e. the transformation from the above into the below is already considered done by the compiler. The problem (it it's a problem) may be in the way I'm generating the code. If you can't get it to happen, I'll email my code. _________________________________________________________________ Help STOP SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail