On Sat, Apr 12, 2014 at 07:50:02AM -0700, Matthew Rocklin wrote:
>    In sympy/core/sets.py:
> 
>  > @@ -1465,6 +1500,9 @@ def _sorted_args(self):
>  >          from sympy.utilities import default_sort_key
>  >          return sorted(self.args, key=default_sort_key)
>  >
>  > +    def _eval_powerset(self):
>  > +        return self.func(self.func(s) for s in subsets(self.args))
> 
>    This solution should work for any iterable set.

But subsets() only works for finite iterables, not for
Naturals, for example.