On Fri, 30 Jul 2010 15:20:55 -0700
John Meacham
type family Add n m :: *
type instance Add Zero Zero = Zero type instance Add Zero (SuccessorTo n) = SuccessorTo n type instance Add (SuccessorTo n) m = SuccessorTo (Add n m)
Standard package is could be somewhat difficult. Standards are undeniably good but "one size doesn't fit all" rule does apply here. Your package couldn't be used to represent big numbers. Little real work has been done on this so it's reasonable to expect progress or even some breakthough.
I thought there was some elegant way to express type level numbers using balanced ternary, but I can't find a reference to it at the moment.
Balanced ternary is useful for represeting signed integers. Implementation of next, prev and basic arithmetic operations is not very elegant Some time ago I wrote implementation of type level numbers using binary and balanced ternary encoding. Will upload to hackage soon.