On Fri, 30 Nov 2007, Luke Palmer wrote: > But I can't figure out a good way to represent bodies in this world. > I considered: > > > newBody :: (Position,Velocity) -> World -> (Body,World) > > Where Body is an ADT with an internal representation of an Integer or > something. The problem with this is that (1) there is no way to > guarantee that a Body actually exists in a World (which is a minor but > still annoying issue), and (2) that there's a possibility that you > could make a Body in one world and use it in another and there would > be no way to detect the error.
Is it ok to have phantom types for Body and World? This would work if the number of worlds is fixed at compile time. newBody :: (Position,Velocity) -> World worldId -> (Body worldId, World worldId) _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
