Seeded random numbers with upper bound in Swift 3?

Question

Is there any way to seed the random number generator and also specify an upper bound in Swift 3?

If you're seeding the random number generator, aren't you using the wrong random number generator? `arc4random_uniform` doesn't need seeding. — matt, Jan 01 '17 at 22:11
Yes but the project I am working on requires the random number generator to be seeded. (I am attempting the Perlin Noise Algorithm in Swift 3) — BCRwar3, Jan 01 '17 at 22:14
[How does one generate a random number in Apple's Swift language?](http://stackoverflow.com/questions/24007129/how-does-one-generate-a-random-number-in-apples-swift-language) — clearlight, Jan 01 '17 at 22:25
Well, a common way is to use `arc4random_uniform("upper bound")`. This solves the upper bound problem but this is an unseeded random number generator. There also exists `srand48("seed")`, this plants the seed and then you can use `drand48()` to produce a random number between 0.0 and 1.0, this solves the seeding problem but does not allow you to produce a number out of the range of 0.0 and 1.0. — BCRwar3, Jan 01 '17 at 22:31
Never used drand48() but can't you just multiply its 0.0 to 1.0 output by your upper bound? — Ali Beadle, Jan 01 '17 at 22:39

score 0 · Answer 1 · answered Jan 02 '17 at 02:53

The most convenient random number generators in Swift reside in GameKit. This generates random integers between -10 and 10 (inclusive):

import GameKit
let source = GKARC4RandomSource(seed: Data(bytes: [42]))
let random = GKRandomDistribution(randomSource: source, lowestValue: -10, highestValue: 10)

for _ in 0..<10 {
    print(random.nextInt())
}

Seeded random numbers with upper bound in Swift 3?

1 Answers1