Mark Dominus:
> My first cut at the program didn't make contraposition inferences, but
> I found a behavior that I interpreted as a bug, and contraposition was
> necessary to fix it. Pr. Sanderson's example program demonstrates
> this same behavior:
>
> > All dogs are mammals
> OK.
> > No octopuses are mammals
> OK.
> > Are any octopuses dogs?
> I don't know.
I find that none of the other submitted solutions (except mine) comes
up with "no" here; they all say "I don't know". (Except perhaps Randy
Sims', which I couldn't get to work.) This makes me worry that I've
committed a basic logic error somewhere, which is something that
hapened more than once while I was developing the program.
I would be interested to see the results of testing the five solution
programs. I could contribute some tests. For example, here's a
simple test that an earlier version of my program failed:
All cats are mammals.
Are any cats not mammals? # No
Here's one that the program got right but that *I* failed:
Some octopuses are orange.
Some cats are orange.
No octopuses are cats.
All cats are mammals.
Are any orange things not mammals? # I don't know
(I initially thought that the answer should be "yes", since orange
octopuses are not mammals. But one cannot conclude that from the
information given; orange octopuses might all be (nonfeline) mammals.)
|
