"Brian M. Scott" <b.scott@[EMAIL PROTECTED]
> wrote in message
news:h58904wbod8p$.fmz64u0n8xfy.dlg@[EMAIL PROTECTED]
> On Sat, 19 Jul 2008 14:47:38 +0100, Jack <jj@[EMAIL PROTECTED]
>
> wrote in <news:Zfmgk.7980$CE1.120@[EMAIL PROTECTED]
> in
> alt.algebra.help:
>
> [...]
>
>> So how about |Z ---> |N?
>
> What about it? Do you have a function f with both of the
> following properties?
>
> (1) For each integer n, f(n) is defined.
> (2) For each integer n, f(n) is a non-negative integer.
>
> If so, then it's correct to write f : Z --> N. (I can't be
> bothered with the pseudo-boldface. When writing in ASCII I
> try not to use 'N' and 'Z' for anything but these sets
> anyway.)
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.
Cheers.
|
