random.swift

import Darwin

extension Int {
    static func random() -> Int {
        return Int(arc4random())
    }

    static func random(range: Range<Int>) -> Int {
        return Int(arc4random_uniform(UInt32(range.endIndex - range.startIndex))) + range.startIndex
    }
}

extension Double {
    static func random() -> Double {
        return drand48()
    }
}

@lchenay is right

Note iLast can be left out in favor of ..<count.
Same in Int.random(i..<count).
Also note [T] is deprecated in favor of [Element]
For sets

extension Set {
    mutating func shuffle() {
        if count > 1 {
            for i in 0..<count {
                let r = Int.random(i..<count)
                let temp = self[self.startIndex.advancedBy(r)]
                self.removeAtIndex(self.startIndex.advancedBy(r))
                self.insert(temp)
            }
        }
    }
}