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Subject:	Re: random() : What am I doing wrong?
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Date:	Wed, 5 Sep 2007 09:01:37 -0600
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DJ Delorie <dj AT delorie DOT com> wrote on Tue, 4 Sep 2007 15:48:27 -0400:

# > What about if I want to generate numbers in the range of 1 through 50?
# > How do I specify my range?
#
# Take the result and "% 50".

That depends if you care about equidistribution; if you do, you'd be
better off doing something more or less like this:

unsigned int raw = random();
unsigned int scaled = (unsigned int) (raw * (50 / (double) UINT_MAX));

At the cost of some performance, of course.

If you do a modulo, you effectively "fold" the original random number
space back on itself - and the numbers will be weighted towards the
first "n" (where n is the remainder of the division).  The code above
actually scales the number so you don't have that problem.

It's not a problem for most cases... it just depends on what
characteristics you need out of your output.

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