I am trying to use type classes to get some percollate actions through a nested data structure. The problem is I can't make an instance of a class unless the type is defined with newtype or data. This means all of my functions look something like this: findFugitive :: DetectiveLocations -> FugitiveLocations -> Move -> FugitiveLocat findFugitive (DetectiveLocations dL) (FugitiveLocations fL) StartGame = (FugitiveLocations minusSet fL (occupiedStops dL)) instead of this: findFugitive :: DetectiveLocations -> FugitiveLocations -> Move -> FugitiveLocat findFugitive dL fL StartGame = minusSet fL (occupiedStops dL) which is much simpler to read. Why can't I make a normal type an instance of a type class? I get errors that it's an ambiguous type. thanks, -mike