Re: Best way to get a non-repeating random number?
Re: Best way to get a non-repeating random number?
- Subject: Re: Best way to get a non-repeating random number?
- From: Gwynne Raskind <email@hidden>
- Date: Mon, 13 Apr 2009 23:26:39 -0400
On Apr 13, 2009, at 8:36 PM, Michael Ash wrote:
You can put every (unsigned) value you want in there, though in
general it's used passing (unsigned)time(NULL) as parameter. This
way
you'll always get a different int.
No you won't. It's a *random* number generator. The seed simply
means you
get a different sequence of random numbers. However, random really
means
RANDOM. I.e. it's perfectly possible to get the same number three
times in a
row during a sequence. That would still be random.
Technically, I'm pretty sure you will always get a different int.
rand() is a crappy, crappy random number generator, and I would guess
that its algorithm can never return the same number twice in a row.
(If anyone is wondering what the alternatives are, use random()
instead.)
arc4random() is also pretty decent, if you need cryptographically
strong random numbers.
-- Gwynne, Daughter of the Code
"This whole world is an asylum for the incurable."
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