Re: [boost] Re: is_base_and_derived question

From: Terje Slettebø (tslettebo_at_[hidden])
Date: 2003-01-31 12:16:25

>From: "David Abrahams" <dave_at_[hidden]>

> Terje Slettebø <tslettebo_at_[hidden]> writes:
>
> > No. You can't prove a negative, an impossibility.
>
> I think that's wrong, and here's my one white crow to prove it ;-)
>
> I can prove that there can never exist a positive integral multiple of 2
which
> is both greater than 2 and prime.
>
> It's the same as saying that *every* positive integral multiple of 2
> which is greater than 2 is a non-prime (now it's not a negative
> statement anymore, but it is logically equivalent).  The positive
> integral multiples of 2 which are not greater than 2 are: 2.  Since
> every other positive integral multiple of 2 is divisible by both 2 and
> itself, it must be non-prime.

Ok, so you can do it in a field where you decide on all the rules, such as
maths.

I was more thinking in terms of if you don't have all the facts. For
example, many thought it was impossible to fly, and perhaps constructed
"proofs" for it, using their available knowledge. However, it turned out to
be possible, anyway, in a way they may not have known about.

However, since the topic was whether it was possible to prove that you could
not detect inheritance without an access violation, I guess that might be
provable, as well, since you may decide on the logic used in the
implementation.

So it seems you're right.

> But anyway, isn't this straying a little bit far from being on-topic?

It is.

Regards,

Terje