Hello all, I have a question about how to create the right kind to declare lists to be a class. I have a class Foo class Foo f where foo :: f a -> Foo and I want to define that a list of Foos is also a Foo, but can't see how to do it. I imagine something like instance Foo f => Foo [f] where foo xs = map foo xs but of course [f] isn't a valid type. I can define newtype LL f a = LL [f a] instance Foo f => Foo (LL f) where foo (LL xs) = LL (map foo xs) but then I haven't defined anything regarding an actual list. When I try type LL f a = [f a] instance Foo f => Foo (LL f) where foo xs = map foo xs I am informed that LL should have two arguments. Any suggestions? Am I overlooking something obvious? -- David Roundy http://www.darcs.net