Generating a random number (GRX)

[Chris Sellitto]

I would like to thank Ken, and Brian for their helpful replies.  Brian, I used your example, and it works great.

Christopher Sellitto
VP Computer Operations
Guaranteed Returns®
100 Colin Drive
Holbrook, NY 11741
Phone: (631) 689-0191 x132
e-mail Chris 


 

> -----Original Message-----
> From: filepro-list-bounces+sellich=guaranteedreturns.com at lists.celestial.com
> [mailto:filepro-list-
> bounces+sellich=guaranteedreturns.com at lists.celestial.com] On Behalf Of
> Brian K. White
> Sent: Wednesday, May 12, 2010 6:18 PM
> To: filepro-list at lists.celestial.com
> Subject: Re: Generating a random number (GRX)
> 
> On 5/12/2010 12:14 PM, Chris Sellitto wrote:
> > filePro® version 5.0.14RN9
> > Windows Server/XP environments.
> >
> > I am trying to generate a number between 1-20, and seem to be doing
> something wrong.  I keep generating the same number over and over.  Below is
> a small test I tried, and RN always displays as 2192.
> >
> > 223  -------   -   -   -   -   -   -   -   -   -   -   -
> > @keyR  ◄ If:
> >         Then:
> > 224  -------   -   -   -   -   -   -   -   -   -   -   -
> >         ◄ If:      rn eq ""
> >         Then: rn(4,.0)=rand("20")
> > 225  -------   -   -   -   -   -   -   -   -   -   -   -
> >         ◄ If:
> >         Then: rn=rand(" ")
> > 226  -------   -   -   -   -   -   -   -   -   -   -   -
> >         ◄ If:
> >         Then: msgbox "Random Number ="<rn
> > 227  -------   -   -   -   -   -   -   -   -   -   -   -
> >         ◄ If:
> >         Then: end
> >
> > Any help is always appreciated.
> >
> > Thanks in advance.
> >
> > Christopher Sellitto
> > VP Computer Operations
> > Guaranteed Returns®
> > sellich at guaranteedreturns.com
> > _______________________________________________
> > Filepro-list mailing list
> > Filepro-list at lists.celestial.com
> > http://mailman.celestial.com/mailman/listinfo/filepro-list
> >
> 
> [...]
> Then: rn = (rand()/("32767"/"19"))+"1"
> [...]
> @once
> Then: x = rand("-1")
> Then: end
> 
> The math comes from the fact that rand() will output from 0 to 32767.
> In order to convert 0-32767 to 1-20, you want to divide 32767 by 19 (not
> 20), then divide rand() by that, which will give you a result from 0 to
> 19, then just add 1 to that for 1-20.
> 
> The @once is how you seed rand(). You only want to seed it once, and
> "-1" means to use the system time to seed it, so each time someone runs
> this process, they each seed rand() differently.
> 
> You can sort of think of rand() as a fixed written down list of random
> numbers, and each time you call rand() you are just reading the next
> number from that list, but the list is always the same and the first
> time you run rand() per process you are always starting out at the same
> point at the top of the list. You can sort of think of seeding rand() as
> changing the position in the list where you will start reading from
> instead of always starting at the top.
> If you never seed, or if you always seed with the same value, you'll
> always get the same number from the first call to rand() and the same
> next number, and the same next number...
> I don't think rand() is _actually_ returning data from a fixed list,
> more like running some math algorithm that will always produce the same
> output given the same starting input. I'm just saying that is a way to
> think about the purpose and effects of seeding, why you always want to
> do it, why you only need to do it once per session, and why you want to
> supply your own bit of randomness (system time) for the seed so you
> always seed differently.
> 
> --
> bkw
> 
> 
> 
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