Why is this a duplicate instance declaration: > class C a > class D b > data T a b > instance (C (T a b), C a) => D b > instance (C (T a b), C b) => D a These are symmetric, but not duplicate, as I see it. -- Hal Daume III "Computer science is no more about computers | hdaume@isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume