epiphany

[Roy Smith]

In article <mailman.1044.1366856455.3114.python-list at python.org>,
 Chris Angelico <rosuav at gmail.com> wrote:

> On Thu, Apr 25, 2013 at 11:41 AM, Roy Smith <roy at panix.com> wrote:
> > In article <5178884b$0$29977$c3e8da3$5496439d at news.astraweb.com>,
> >  Steven D'Aprano <steve+comp.lang.python at pearwood.info> wrote:
> >
> >> I don't see why you would need anything like that. Reading further on, I
> >> see that you are counting unimplemented rules as true, for some reason
> >> which I don't understand.
> >
> > The top-level logic we need to enforce is "this configuration doesn't
> > violate any rules".
> 
> Then have your unimplemented rules simply return True. Easy!
> 
> ChrisA

It's nice to have tri-state logic:

* This rule passes

* This rule fails

* This rule was not evaluated

What I've got now expresses that perfectly.