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.
Unfortunately, the symbol 'N' is used by some to denote the
set of non-negative integers and by others to denote the set
of positive integers. I consider the latter usage
old-fa****oned and something to be avoided, and I *never* use
N for the set of positive integers. If you want the set of
positive integers, use Z+, which is wholly unambiguous.
(The '+' should be a superscript.)
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