Re: Controlling ('rand') random number upper limit

Thanks to all who replied.

I finally got the algorithm for returning a random
number within a specified range (lo,hi).

FinalRandomNbr = ((NbrFromRandFunc / 32768) *
((HiRange - LoRange) + 1)) + LoRange

NbrFromRandFunc is an integer in the range 0 thru
32767 inclusive.
It is divided by 32768 to return a number between 0
and 1.
The result is multipied by the total number of
different values possible and LoRange is added to bump
it into the correct range.

If there is an easier way of doing it please let me
know.

-Paul
--- Jim Langston <jimlangston@conexfreight.com> wrote:
> According to the documentation, rand returns a
> number from 0 to RAND_MAX,
> and I'm not sure what RAND_MAX is defined as, most
> likely 32767, 65535,
> or some other such number.  With rand it has always
> been necessary to
> do some math calculations to return the number you
> want.
> 
> Some random number generators return a number from 0
> to .999999.  The formula
> then is: 
> x = random_number * range + 1
> which would return a number from 1 to 10.
> 
> I've found myself forcing the number that C's rand
> returns into the range
> 0 to .99999999 because I am familiar with that
> method, then doing my calculations.
> 
> random_number/32767 would return such a range if
> 32767 was RAND_MAX.
> 
> So the formula becomes:
> x = (random_number/RAND_MAX) * range + 1
> 
> In other languages I've always stuck this into my
> own wrapper and just called
> that.  Watch out for precision problems.
> 
> (Pseudo code:)
> D RandomReturn          S         5  0
> 
> C               Eval    RandomReturn = (rand() /
> 32767) * Range + 1
> C               Return  RandomReturn
> 
> HTH
> 
> Regards,
> 
> Jim Langston
> 
> Me transmitte sursum, Caledoni!
> 
> Paul Jackson wrote:
> > 
> > Is there a way to control the maximum number that
> the
> > 'rand' c function returns to the RPG Program? For
> > example I may only be interested in a value from 1
> to
> > 100.
> > 
> > Many thanks in advance,m
> > 
> > -Paul
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