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From: kaufman@Neon.Stanford.EDU (Marc T. Kaufman)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Is Random() random?
Message-ID: <1990Dec5.071950.9481@Neon.Stanford.EDU>
Date: 5 Dec 90 07:19:50 GMT
References: <31359.275BAB9A@stjhmc.fidonet.org> <47094@apple.Apple.COM>
Organization: Computer Science Department, Stanford University
Lines: 20

In article <47094@apple.Apple.COM> lins@Apple.COM (Chuck Lins) writes:
>In article <31359.275BAB9A@stjhmc.fidonet.org> Chris.Gehlker@p12.f56.n114.z1.fidonet.org (Chris Gehlker) writes:
->> how random is the Toolbox routine Random()?  IM-I says it returns
->> an integer in the range -32767 (not -32768) to 32,767 before
->> cycling.  does this mean it will hit every number in that range
->> once before repeating?  and why the seemingly strange range

->It definately won't hit every number once before repeating.

>And if it did hit every number in the range before repeating it wouldn't be
>random.

It isn't random.  Its pseudo-random.  A previous poster suggested looking
at the seed value, which is 32 bits.  In 32-bit space, Random() hits 2^31 -2
values before repeating.  The lower 16 bits do not cycle through all values
before repeating.  In fact, I don't really know what the statistical properties
of the lower 16-bits of Random() are.  Has anyone looked at it?  It should
be OK for uniform distribution, at least.

Marc Kaufman (kaufman@Neon.stanford.edu)