/prog/ - Random [-x..x] && !NULL

Name: Anonymous 2012-01-19 12:22

Fellow Progs,
any idea to nicely implement this ?

First idea...ugly

get random value
if value is zero
get random value
done

Second idea

get random positive value
make coin toss
if coin shows head
value *= -1

But there must be something easiert / nicer

thanks alot.

Name: Anonymous 2012-01-19 12:47

from random import randrange

def randrange_nonzero(x, y):

    n = randrange(x, y-1)

    return n + (not n)

Name: Anonymous 2012-01-19 12:49

>>2
Sorry, disregard that, I fucked up. Here's the correct one:

def randrange_nonzero(x, y):

    n = randrange(x, y-1)

    return n + (0 if n < 0 else 1)

Name: Anonymous 2012-01-19 13:04

>>3
hmmm looks like a bigger version then my first idea
why the -1 on y ?

but thanks anyway :)
btw using C nothing fancy like if's in my return :P

Name: Anonymous 2012-01-19 13:24

>>4
Your first variant may not be constant time.

/* returns a random range between x and y, both inclusive, that's not 0 */

int randrange_nonzero(int x, int y)

{

        int n = rand() % (y - x) + x;

        return n + (n>=0);

}

Name: Anonymous 2012-01-19 13:27

something like pow(rand(2),2)*(1+rand(x)) would work, where rand gives you a ranged random from 0 to x, and pow is the power function (in this case x*x would also be sufficient).

Name: Anonymous 2012-01-19 13:27

>>5
Ahh thanks alot ,now i actually can see what u did there.
I know that my first attempt may not be finished in const. time.
Thus i wrote "ugly" on it ;)

Thanks for the help!

Name: Anonymous 2012-01-19 13:31

>>4
Python's x if y else z is equivalent to C's y?x:z.

Name: Anonymous 2012-01-19 13:33

>>8
Thanks, good to know

Name: Anonymous 2012-01-19 13:52

>>8,9
The numero uno trolling operator, the conditional operator.

Name: Anonymous 2012-01-19 14:16

>>10
Why?

Name: Anonymous 2012-01-19 14:50

>>11
Because it confuses mental midgets.

Name: Anonymous 2012-01-20 13:01

def randnot0(x): return randint(-x, x) or randnot0(x)

Name: Anonymous 2012-01-22 18:05

>>13
not really

Name: Anonymous 2013-09-01 11:23

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Random [-x..x] && !NULL

1 Name: Anonymous 2012-01-19 12:22

2 Name: Anonymous 2012-01-19 12:47

3 Name: Anonymous 2012-01-19 12:49

4 Name: Anonymous 2012-01-19 13:04

5 Name: Anonymous 2012-01-19 13:24

6 Name: Anonymous 2012-01-19 13:27

7 Name: Anonymous 2012-01-19 13:27

8 Name: Anonymous 2012-01-19 13:31

9 Name: Anonymous 2012-01-19 13:33

10 Name: Anonymous 2012-01-19 13:52

11 Name: Anonymous 2012-01-19 14:16

12 Name: Anonymous 2012-01-19 14:50

13 Name: Anonymous 2012-01-20 13:01

14 Name: Anonymous 2012-01-22 18:05

15 Name: Anonymous 2013-09-01 11:23

Name: Anonymous 2012-01-19 12:22

Name: Anonymous 2012-01-19 12:47

Name: Anonymous 2012-01-19 12:49

Name: Anonymous 2012-01-19 13:04

Name: Anonymous 2012-01-19 13:24

Name: Anonymous 2012-01-19 13:27

Name: Anonymous 2012-01-19 13:27

Name: Anonymous 2012-01-19 13:31

Name: Anonymous 2012-01-19 13:33

Name: Anonymous 2012-01-19 13:52

Name: Anonymous 2012-01-19 14:16

Name: Anonymous 2012-01-19 14:50

Name: Anonymous 2012-01-20 13:01

Name: Anonymous 2012-01-22 18:05

Name: Anonymous 2013-09-01 11:23