How to select range of values when using arc4random()

Question

Can I set a range of numbers when using arc4random()? For example 50-100 only.

Answer 1

To expand upon JohnK comment.

It is suggested that you use the following function to return a ranged random number:

arc4random_uniform(51)

which will return a random number in the range 0 to 50.

Then you can add your lower bounds to this like:

arc4random_uniform(51) + 50

which will return a random number in the range 50 to 100.

The reason we use arc4random_uniform(51) over arc4random() % 51 is to avoid the modulo bias. This is highlighted in the man page as follows:

arc4random_uniform(upper_bound) will return a uniformly distributed random number less than upper_bound. arc4random_uniform() is recommended over constructions like ``arc4random() % upper_bound'' as it avoids "modulo bias" when the upper bound is not a power of two.

In short you get a more evenly distributed random number generated.