On Wed, Nov 15, 2000 at 11:37:18AM +1100, James Wilkinson wrote:
> This one time, at band camp, [EMAIL PROTECTED] said:
>
> >all primes end in either 1 3 7 or 9 except 2 and 5
>
> How about 39? That's not prime :) You need a better heuristic ;)
No, he didn't say everything ending in 1 3 7 or 9 _is_ prime, just
that to be prime you have to end in 1 3 7 or 9 (except 2 and 5)
>
> > so it is pointless to test it if it dosent ie ends in a 5, so how can i
> >test to see if the last number is 1 3 7 9 before i start the curnum % x
> >!=0
>
> Well, you could convert it to a string, and look at the last character.
> I think you're going to spend more time in the conversion than you think
> you'd save by using it.
number % 10 will give you the last digit. There are much better methods
of finding prime numbers, though. sci.crypt has a lot of info about them.
Stephen
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Stephen Norris [EMAIL PROTECTED]
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