shuffle array in place.swift

import Cocoa

extension Int {
	static func anotherRandom(_ range: Range<Int>) -> Int {
		let floor = range.lowerBound
		guard var ceiling = range.last else { fatalError("No last value in range") }
		ceiling += 1
		let normalCeiling = ceiling - floor
		let rando = Int(arc4random_uniform(UInt32(normalCeiling)))
		return rando + floor
	}
}

extension Array {
	mutating func uniformRandomShuffle() {
		for index in 0..<self.count {
			let newIndex = Int.anotherRandom(0..<self.count)
			(self[index], self[newIndex]) = (self[newIndex], self[index])
		}
	}
}

func confirmUniformity() {
	let iterations = 10000

	// this is setting up a map of a count of where each value appears after each shuffle
	let individualTracker = (0...9).map { _ in 0 }
	var totalTracker = (0...9).map { _ in individualTracker }

	for _ in 1...iterations {
		var arrayToShuffle = Array(0...9)
		arrayToShuffle.uniformRandomShuffle()
		for (index, value) in arrayToShuffle.enumerated() {
			totalTracker[value][index] += 1
		}
	}

	for (value, counter) in totalTracker.enumerated() {
		print(value, counter)
	}
}

// every value should be roughly around 1/10 of iterations from the confirmation func
confirmUniformity()

I've realized that this isn't actually uniform, so scratch the uniformity