Re: Idempotence and "Replication Insensitivity" are equivalent ?
Date: Thu, 21 Sep 2006 12:46:07 GMT
Message-ID: <jQvQg.2073$HZ5.276_at_trndny08>
"Marshall" <marshall.spight_at_gmail.com> wrote in message news:1158801185.053583.184200_at_i42g2000cwa.googlegroups.com...
> Oh, okay. I think I see what you're trying to get at. We have an n-ary
> function which we wish to express as an aggregate, that is n-ary
> NOR. That is, if all operands are F, return T, otherwise return F.
> So we could define this n-ary NOR as this aggregate:
>
> not(fold(or,F))
>
> OR() is idempotent, n-ary NOR is duplication insensitive. So
> my proposed equivalence holds.
>
> But the above function has some problems. For one thing,
> it's not NOR. For another, it's not commutative, so it's
> going to evaluate to different things depending on the
> order in which it is supplied operands. But even if we're
> generous and call it well-defined, while not idempotent,
> it's duplicate-sensitive, so it's not a counter to the
> equivalence.
I don't understand. n-ary NOR looks commutative to me. Can you give an example? Received on Thu Sep 21 2006 - 14:46:07 CEST