while (a=b()) ... infinite sets digression
Gordon McMillan
gmcm at hypernet.com
Thu May 20 00:12:38 EDT 1999
Blake blunders into the tarpit:
> On Wed 19 May, Chad Netzer <chad at vision.arc.nasa.gov> wrote:
> In comp.lang.python, you wrote:
> >Greg Ewing wrote:
> >> Chad Netzer wrote:
> >In fact, both are probably Aleph-1 sets which means they are larger than
> >the set of integers... I'm out of my area, here, so I'll let it go at
> >that. ;)
>
> Hmmm... I can't quite believe that, since there is an obvious
> mapping from the set of all strings to the set of all integers.
> (Think base n, where n=the number of possible characters.) I
> suppose this assumes a less-than-infinite number of characters, but
> I can only think of about 104 different characters, so the total
> must be finite, right? :)
Moshe, Chad & I straightened this out in email. Chad is correct
(well, if you take him as saying "more than Aleph-0").
Instead of the integers, take the numbers between 0 and 1. Use your
mapping. Now realize that most of the numbers you've created are
transcendentals, and the rationals, by comparison, amount to a hill
of beans. So it _is_ a denser form of infinity than the integers.
Well, as long as you leave 42 out of it.
my-density-is-calling-me-ly y'rs
- Gordon
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