"Brian M. Scott" <b.scott@[EMAIL PROTECTED]
> wrote in message
news:1usfqoaxp7374.gz6czvua09cx.dlg@[EMAIL PROTECTED]
> On Sat, 19 Jul 2008 22:58:04 +0100, Jack <jj@[EMAIL PROTECTED]
>
> wrote in <news:trtgk.39540$7B3.5025@[EMAIL PROTECTED]
> in
> alt.algebra.help:
>
> [...]
>
>> The thing that perplexes me a little is that Paul was
>> saying I could define |N as the set of positive integers
>> if I so wished, which might in retrospect turn out to
>> be a good option for me; but then if we have t: |N --> |N
>> you allow me to have t(n)=0, but 0 is not positive.
>
> I don't see how this relates to what preceded it.
It's just something that niggles me: if you have a function t: N ---> N
and
N is by definition a positive integer, it looks wrong to refer to t(n)=0;
yet neither you nor Paul objected to the use of N --->N when N could, so
it
seemed, be the set of positive integers. So if I then say t: Z^+ ---> Z^+,
and refer to t(n)=0, is that sound or unsound?
Cheers.
|
