The following program import Complex instance Ord a => Ord (Complex a) where (x1 :+ y1) `compare` (x2 :+ y2) = (x1, y1) `compare` (x2, y2) gives the message ERROR Bug.hs:3 - Cannot build superclass instance *** Instance : Ord (Complex a) *** Context supplied : Ord a *** Required superclass : Eq (Complex a) What is hugs' problem here? It compiles with ghc. -- -- Johannes Waldmann ---- http://www.informatik.uni-leipzig.de/~joe/ -- -- joe@informatik.uni-leipzig.de -- phone/fax (+49) 341 9732 204/252 --