because you haven't helped write a patch change it yet :)
-Carter
On Sat, Oct 25, 2014 at 9:53 AM, Barney Hilken
If you define your own type level naturals by promoting data Nat = Z | S Nat you can define data families recursively, for example data family Power :: Nat -> * -> * data instance Power Z a = PowerZ data instance Power (S n) a = PowerS a (Power n a) But if you use the built-in type level Nat, I can find no way to do the same thing. You can define a closed type family type family Power (n :: Nat) a where Power 0 a = () Power n a = (a, Power (n-1) a) but this isn't the same thing (and requires UndecidableInstances). Have I missed something? The user guide page is pretty sparse, and not up to date anyway. If not, are there plans to add a "Successor" constructor to Nat? I would have thought this was the main point of using Nat rather than Int. Barney. _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users