On Fri, Aug 14, 2009 at 12:03 PM, Dan Weston<weston...@imageworks.com> wrote: > But presumably he can use a data family instead of a type family to restore > injectivity, at the cost of adding an extra wrapped bottom value and one > more layer of value constructor?
Actually, you don't even necessarily pay this penalty, since you can put newtypes into data families. > data family Foo a > newtype instance Foo () = UnitFoo Int You do need to add the constructor wrap/unwrapping in code, but they all get erased after typechecking. -- ryan _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
