Random of zero

[Wil Dijkstra]

The maximum of the random parameter is apparently 2^31-1.
The integer limit of MC? Try this:
  put 2^53-1 into x
  put x & cr & x+1 & cr & x+2

How does the random function work?
Most, if not all random functions use:
z[n] = a * z [n-1] mod m
a and m are positive integers. The seed (z[0]) should be a positive integer (usually based on the number of ticks).
which produces a random number 0,1,2,...,m-1

Generally (for statistical use), the numbers a and m are selected in such a way that the number 0 is excluded and a random number 1,2,3,...,m-1 is generated. Next, the generated number is divided by m (u[n] = z[n]/m) , to generate a real number >0 and <1.

A common choice for a and m is:
  a = 630360016
  m = 2^31-1
which excludes 0. Quite likely, these numbers are used in MC too.

Wil Dijkstra

> Shari, 
> 
> Consider that the function random(x)-1 = right result for any x < (2^64)-1 (the integer limit of MC - I didn't test this limit lately though)... 
> 
> Naturally if you assume 0 to be a number and/or part of your answer. Remember those problems with 0-255 = 256 values? 
> 
> The proof I wrote the day this thread was first posted but I didn't post it since you probably already think im such a nuts... 
> 
> cheers 
> Xavier 
> 
> 
> 
> ---------------------=---------------------
> Xavier Bury
> TNS NT LAN Server
> ext 6465 
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> 
> 
> 	Shari <gypsyware at earthlink.net> 
> Sent by: metacard-admin at lists.runrev.com 
> 
> 13/05/03 14:18 
> Please respond to metacard 
>         
>         To:        metacard at lists.runrev.com 
>         cc:        ^ 
>         Subject:        RE: Random of zero 	
> 
> 
> 
> >It is clear that you read the MetaTalk entry for random, and 
> >likewise it is clear that you chose to try to use the function 
> >outside of its clearly documented scope.
> 
> The assumption that random(0) would obviously be 0 was made based on 
> general principles.  Not on Metatalk itself.  I did not expect to 
> have to look up what would seem to be a simple function.
> 
> It was not until the handler failed, and I discovered that random(0) 
> consistently produces 1, that I looked it up in the reference docs to 
> see if there was an explanation, and some way to fix it to produce 0 
> as I intended it to.
> 
> I do not know in general mathematical principles, what result one 
> would get from random(0).  But I would expect it to be 0.  My mistake 
> for assuming.  (Unless of course, general math principles support my 
> theory :-)
> 
> Any math gurus out there know?
> 
> :-)
> 
> Shari C
> -- 
> --Shareware Games for the Mac--
> http://www.gypsyware.com
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