Date: Wed, 26 Nov 1997 12:53:28 -0800 (PST)
Message-Id: <199711262053.MAA16591@adit.ap.net>
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To: George Foot <mert0407 AT sable DOT ox DOT ac DOT uk>, djgpp AT delorie DOT com
From: Nate Eldredge <eldredge AT ap DOT net>
Subject: Re: randomize?
Precedence: bulk

At 05:28  11/25/1997 GMT, George Foot wrote:
>Also note that if you're from a Borland background you'll be expecting
>the `random' function to take a parameter (the smallest integer that
>will never be returned) -- in djgpp this is not the case.  The `rand'
>function returns an integer from 0 to RAND_MAX and the `random'
>function returns an integer from 0 to MAXINT.  In practice, these
>maxima are both the same, and equal to the largest number that can be
>expressed as a (32-bit) integer.  To restrict the range of the
>numbers, use the divison-remainder operator, `%'.
I'll make the usual comment here that for the `rand' RNG, the low-order
bits, which are what you get when using `%', are sometimes not as random as
one would like. You can fix this with some casts:
(int)((double)rand()/RAND_MAX)*largest_random_number_you_want
`random' doesn't have this problem, but also is not ANSI. The discrepancy is
due to legal issues and is being considered.

Nate Eldredge
eldredge AT ap DOT net