Hi,
I'm trying to create a random float between 0.15 and 0.3 in Objective-C. The following code always returns 1:
int randn = (random() % 15)+15;
float pscale = (float)randn / 100;
What am I doing wrong?
views:
172answers:
3
+2
A:
Try this:
(float) random()/RAND_MAX
Or to get one between 0 and 5:
float randomNum = (rand() / RAND_MAX) * 5;
Several ways to do the same thing.
Caladain
2010-08-04 21:45:05
This is wrong. `random() / RAND_MAX` will not give you a floating-point value as neither value is floating-point. Also, the domain of `random()` is not 0 to RAND_MAX. The domain of `rand()` and `rand_r()` is. So you should use: `(float)rand() / RAND_MAX` to get the expected result.
Jonathan Grynspan
2010-08-04 22:48:08
A:
- use arc4random() or seed your random values
try
float pscale = ((float)randn) / 100.0f;
Lou Franco
2010-08-04 21:46:48
A:
Your code works for me, it produces a random number between 0.15 and 0.3 (provided I seed with srandom()). Have you called srandom() before the first call to random()? You will need to provide srandom() with some entropic value (a lot of people just use srandom(time(NULL))).
For more serious random number generation, have a look into arc4random, which is used for cryptographic purposes. This random number function also returns an integer type, so you will still need to cast the result to a floating point type.
dreamlax
2010-08-04 22:05:38