Re: Thinking about MINUS

From: NENASHI, Tegiri <tnmail42_at_gmail.com>
Date: Mon, 8 Jan 2007 18:19:01 +0100 (CET)
Message-ID: <Xns98B27D88ABC82asdgba@194.177.96.26>

"Marshall" <marshall.spight_at_gmail.com> wrote in news:1168200540.103754.204710_at_s80g2000cwa.googlegroups.com:

> On Jan 7, 10:54 am, paul c <toledobythe..._at_oohay.ac> wrote:

>> Maybe, and I would be curious to see that definition work.  I believe
>> the conventional stance (ie., most products' stance) is that the
>> result is undefined.  If I have that right, my attitude is that means
>> an implementation must support exceptions to handle it.  Although I
>> don't object to having exceptions if they give some programming or
>> user safety, for some reason I can't explain, I don't like the idea
>> of a system that allows undefined conditions to be produced and then
>> must support exceptions to cope with them.

>
> Exceptional conditions are an inescapable fact of life, alas. Consider
> 1/0.
> Even if we consider a system consisting only of the natural numbers,
> zero, successor and predecessor, we have to wrestle with the question
> of what the predecessor of zero is.

We have not wrestle if we think that the natural numbers satisfy the axioms of Peano. Zero does not have the predecessor, see the axioms.

>
> Marshall
>
Received on Mon Jan 08 2007 - 11:19:01 CST