by Erro » Thu, 16 Sep 1999 04:00:00
In other words the item in the third record would be 7 and in the next
would be 11.
I want to use this as a hidden code so that people trying to duplicate
the number could not just randomly generate one.
errol
by Hans Rijnbo » Sat, 18 Sep 1999 04:00:00
--
Hans Rijnbout
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Postbus 80.083, NL-3508 TB UTRECHT
tel: +31 30 253 4567 fax: +31 30 253 3072
by Simon Slav » Sat, 18 Sep 1999 04:00:00
> In other words the item in the third record would be 7 and in the next
> would be 11.
I'd suggest that you use a fixed-time process to generate aQuote:> I want to use this as a hidden code so that people trying to duplicate
> the number could not just randomly generate one.
Simon.
--
<http://www.hearsay.demon.co.uk> | ... you start off with a typical message,
No junk email please. | let's say a 2.5MB Word document containing
ET may've phoned /us/. | three lines of text and a macro virus ...
by Erro » Sat, 18 Sep 1999 04:00:00
I am not sure what you mean by your comment below.
errol
> I'd suggest that you use a fixed-time process to generate a
> check-digit instead. That would be more appropriate.
> Simon.
> --
> <http://www.hearsay.demon.co.uk> | ... you start off with a typical message,
> No junk email please. | let's say a 2.5MB Word document containing
> ET may've phoned /us/. | three lines of text and a macro virus ...
by Erro » Sat, 18 Sep 1999 04:00:00
I am not sure what you mean by your comment below.
errol
> I'd suggest that you use a fixed-time process to generate a
> check-digit instead. That would be more appropriate.
> Simon.
> --
> <http://www.hearsay.demon.co.uk> | ... you start off with a typical message,
> No junk email please. | let's say a 2.5MB Word document containing
> ET may've phoned /us/. | three lines of text and a macro virus ...
by Mac_Za » Sun, 19 Sep 1999 04:00:00
>>Is there a script that could generate prime numbers. I am thinking of
>>using an item number that would be divisable by a prime that could be
>>generated by the record number?
> Errol,
> Yes, you could write a script that calculates the next prime, but the
> simplest I could think of still requires multiple loops through all
> records of your file. Much easier and faster to have a numbered list of
> primes in a separate lookup file and look them up via the record number.
Good luck
Chris
Do you happen to need to know all the prime numbers between, say,
8,123,456,789,000,000 and 8,123,456,790,000,000?
Or maybe you'd just like to say for sure if 6,000,000,016,333,021 is a prime
number.
Can you figure this out with dBASE or FoxPro?
The answer is yes, no problemo.
Okay, here's the story: I was cleaning house the other day and I ran across a
bench marking program I wrote back in my QA engineer days at Borland (I updated
it slightly a couple of years ago when I got my CD writer). I never published
this program and it is certainly obsolete but I thought someone might find it
interesting. It's tricky. I store all the primes within a range of 30 numbers
in a single byte. So, the primes within a range of 1 million numbers gets
stored in a table of only 34 k.
This code runs without modification under dBASE IV 2.0, dBASE 5, or FoxPro v
2.5 (it probably runs under other DOS versions but these are the ones I tested
with). It writes a log file with elapsed times for each range of 1 million.
So, I found it useful for speed benchmarking--comparing xBase versiions and
also comparing hardware setups.
The program uses a table of primes (all primes under 100 million) to facilitate
finding larger primes. If the program doesn't find this table then it
generates it. This will take a long time (perhaps overnight or even days on
slow systems). If you want to skip this step, you could dowload this starter
set of primes. The file is called
http://www.go2zero.com/1st100ml.dbf (it's about 3.3 megabytes)
Once you have the first 100 million table, it takes only about 10 seconds on a
fast system to find all the primes in a range of one million (for smallish
primes, say under 100 billion). The quadrillions take longer of course.
Here's the code:
http://www.go2zero.com/se-prg.txt
--Alan Dechert
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