Random Double number in swift between 0 and 1

Question

I'm trying to generate random double numbers between 0 and 1 but I'm getting always 0

func randFunct() -> Double {
     let randomInt = arc4random_uniform(100) + 1 // [1, 100]
     let randomDouble : Double = Double(randomInt/100)
     return randomDouble
}

See also [Strange Swift numbers type casting](http://stackoverflow.com/questions/28813516/strange-swift-numbers-type-casting) — Hamish, Aug 26 '16 at 18:02
Why use `Double` when you seem to only want the result to 2 decimal places? — pjs, Aug 26 '16 at 18:07
@Developer2012 - So why limit them to 2 decimal places? And if you only want them to 2 decimals, why not use `Float` rather than `Double`? — pjs, Aug 26 '16 at 18:20

Alexander · Answer 1 · 2016-08-26T19:44:26.837

3

Try this:

extension Double {
    private static let arc4randomMax = Double(UInt32.max)

    static func random0to1() -> Double {
         return Double(arc4random()) / arc4randomMax
    }
}

print(Double.random0to1())

edited Aug 26 '16 at 19:44

answered Aug 26 '16 at 18:00

Alexander

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You should flag to close as a duplicate rather than repeating the already available answer that you, yourself, pointed out. – pjs Aug 26 '16 at 18:00
@pjs I wanted to help OP convert it to swift – Alexander Aug 26 '16 at 18:09
1

This is nice for a `Float`, but suboptimal for `Double`. See https://stackoverflow.com/a/34765674/1033581 – Cœur Sep 27 '17 at 08:40
@Cœur nice, thanks! – Alexander Sep 27 '17 at 15:03

score -1 · Answer 2 · answered Aug 26 '16 at 18:13

-1

It solves my question:

    let randomDouble : Double = Double(arc4random()) / Double(UINT32_MAX) * abs(0 - 1) + min(0, 1)

answered Aug 26 '16 at 18:13

Developer2012

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You can keep your original code, just change the parenthesis to make it a Double before dividing by 100. BTW if you want a number from 0.0 to 1.0 just use arc4random_uniform(101) that would generate a number between 0-100. `var randomDouble: Double { return Double(arc4random_uniform(101))/100 }` – Leo Dabus Aug 26 '16 at 18:31
1

`* abs(0 - 1) + min(0, 1)`? – Hamish Aug 26 '16 at 19:02
@Hamish == `* -1 + 0` == `* -1`? Yeah I'm confused, too. :p – Alexander Aug 26 '16 at 19:45
@AlexanderMomchliov Equals `* 1 + 0`... so just plain useless lol :P – Hamish Aug 26 '16 at 19:46
1

Ah yeah, it does an abs on the `-1`. lol I'm more confused now. – Alexander Aug 26 '16 at 19:48

Random Double number in swift between 0 and 1

2 Answers2