> import Foundation
>
> (1..<4).sample
> [1,2,3].sample
> "abc".characters.sample
> ["a": 1, "b": 2, "c": 3].sample
>
> Like so many users of Swift, I have extensions of IntegerType, ClosedInterval
> and CollectionType that avail me of the above methods and their family, but
> I’d much rather if such extensions came with Darwin or at least Foundation.
I don't think a `sample` property or method is the right approach here. It
would be using some sort of global source of random numbers, which means that:
* It's not testable or repeatable
* It needs to be synchronized with other threads
* It can't be configured to use a different random number generator
Personally, I would eventually like to see something like this in the standard
library:
protocol RandomizerProtocol {
mutating func randomBytes(_ n: Int) -> [UInt8]
// or possibly something involving a generic-length tuple, for
speed
}
extension RandomizerProtocol {
// for coin flips
mutating func randomChoice() -> Bool { ... }
// for choosing a random element
mutating func randomChoice<CollectionType:
RandomAccessCollection>(from collection: CollectionType) ->
CollectionType.Element { ... }
// for choosing a random value from an uncountable range (e.g.
Range<Double>)
mutating func randomChoice<Element: Strideable>(from range:
Range<Element>) -> Element { ... }
}
struct Randomizer: RandomizerProtocol {
init(state: [UInt8]) { ... }
init() { self.init(state: somethingToMakeAGoodRandomState()) }
mutating func randomBytes(_ n: Int) -> [UInt8] {
// akin to arc4random()
}
}
This would allow you to confine a random number generator to a particular
thread, swap one implementation for another, or inject one with a fixed
starting state as a dependency to make tests predictable. A design like this
one works around the problems I described nicely.
However, I don't think this is a high enough priority to address right now.
This is borderline out-of-scope as "major new library functionality", and
there's so much stuff to do that is truly core to the language, this simply
seems like a distraction.
--
Brent Royal-Gordon
Architechies
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