> unsigned long RandomNum(unsigned long n)
SysRandom only returns 15 bits of random data, so using a 32-bit argument
for the desired range is potentially confusing. If you pass in a large value
for n, you'll get large results, but some of the values between zero and n-1
will never be returned. OTOH, the way you're using n within the function
would require a cast if it was declared as a 16-bit argument.
> {
> static Boolean initialized = false;
>
> unsigned long x;
> if (initialized == false) {
> initialized = true;
> SysRandom(TimGetTicks());
> }
> if (n == 0)
> n = 1;
>
> x = SysRandom(0) ;
Storing a 16-bit (15, actually) in a 32-bit variable. So far so good...
> x = (double) x / ( (double) (1 + sysRandomMax / n )) ;
Why are you using doubles? What I mean is why are you using floating point?
The "sysRandomMax / n" expression will round down. I'm not sure if I
understand this statement. AFAICT, what you're trying to do, mathematically
speaking, is:
SysRandom(0) * n / sysRandomMax
If you limit n to be in the [0..32767] range, then you can do this using
32-bit integer math:
x = x * n / sysRandomMax;
Note that this doesn't mind n being zero. Many people use:
SysRandom(0) % n;
despite the fact that it isn't uniform, particularly for large n. If n is a
power of two, you can use masking, for example:
SysRandom(0) & 0x001F;
returns a random number in the [0..31] range.
>
> return x;
> }
--
For information on using the Palm Developer Forums, or to unsubscribe, please see
http://www.palmos.com/dev/tech/support/forums/
