[asagoo]

Is there a function or class in the Cocoa frameworks or the CoreFoundation that allows me to easily get a random integer?
Didn't find anything in the documentation.

[tom_waters]

Originally posted by asagoo:
Is there a function or class in the Cocoa frameworks or the CoreFoundation that allows me to easily get a random integer?
Didn't find anything in the documentation.

There's nothing in Cocoa or Core for this because it is already in BSD.

Code:

% man random
RANDOM(3)                 System Programmer's Manual                 RANDOM(3)

NAME
     random, srandom, initstate, setstate - better random number generator;
     routines for changing generators

SYNOPSIS
     #include <stdlib.h>

     long
     random(void)

     void
     srandom(unsigned seed)

     char *
     initstate(unsigned seed, char *state, int n)

     char *
     setstate(char *state)

DESCRIPTION
     The random() function uses a non-linear additive feedback random number
     generator employing a default table of size 31 long integers to return
     successive pseudo-random numbers in the range from 0 to (2**31)-1.  The
     maximum value returned by random() is LONG_MAX (as defined by the header
     file <limits.h>). The period of this random number generator is very
     large, approximately 16*((2**31)-1).

[Amorph]

Not to mention C's own rand(), also in <stdlib.h> (and more portable than random()).


------------------
James

"I grew up. Then I got better." - Sea Wasp

[Scott_H]

Man. I knew a guy in grad school that used to freak over random number generators. He was setting out to write his own because he didn't trust the C ones. Like he could do a better job? PLUS his work wasn't sensitive enough to pick up on a bad random number generator anyway. Freak!

[mr_sonicblue]

Supposedly the Merseen Twister (sp?) is the current best random number generator. But, I think only PHP uses it natively (they have the old one, too).

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[parallax]

Of course, if you don't care about getting millions of numbers per second, your best bet is to just find as many statistics as you can and manipulate them together (core processor temperature, audio in, &c.).

You can get the Mersenne Twister code here:
http://www.math.keio.ac.jp/~matumoto/emt.html

[mr_sonicblue]

Originally posted by parallax:
You can get the Mersenne Twister code here:
http://www.math.keio.ac.jp/~matumoto/emt.html

Wow, that's amazingly short.

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[lgerbarg]

Originally posted by mr_sonicblue:
Supposedly the Merseen Twister (sp?) is the current best random number generator. But, I think only PHP uses it natively (they have the old one, too).

MT is very cool, and it is really fast, but it does not have any intrinsic methods for entropy gathering, and it is not cryptographicly secure. For serious crypto grade numbers I recommend Yarrow. Apple has a userlevel implementation of it as part of SecurityServer (though I think the interfaces are private), and I have ported a kernel level version from FreeBSD. My patches are available from http://www.rpi.edu/~gerbal/darwin-patches/.

Louis

------------------
Louis Gerbarg
Darwin Developer