On Sat, May 24, 2008 at 1:11 AM, Thomas Hartman
World.hs:42:0: No instances for (Eq (a (M.Map String Player)), Eq (a (M.Map ItemId Item)), Eq (a (M.Map PlayerId Player)), Eq (a (M.Map RoomId Room)), Eq (a RoomId)) arising from the 'deriving' clause of a data type declaration at World.hs:(42,0)-(50,14) Possible fix: add an instance declaration for (Eq (a (M.Map String Player)), Eq (a (M.Map ItemId Item)), Eq (a (M.Map PlayerId Player)), Eq (a (M.Map RoomId Room)), Eq (a RoomId)) When deriving the instance for (Eq (World a))
This error looks suspicious: notice that "a" in a type-constructor position. My guess is that you're accidentally using World's type parameter in a strange way. Perhaps you should double-check that your types and constructor definitions are using parentheses appropriately. Stuart