qsort.swift

import Foundation

extension Comparable {
    static func compare(l: UnsafePointer<Void>, _ r: UnsafePointer<Void>) -> Int32 {
        let left: Self = UnsafePointer(l).memory
        let right: Self = UnsafePointer(r).memory
        if left < right { return -1 }
        if left == right { return 0 }
        return 1
    }
    
}

typealias CompareFunc = (UnsafePointer<Void>, UnsafePointer<Void>) -> Int32

func cmp(thunk: UnsafeMutablePointer<Void>, l: UnsafePointer<Void>, r: UnsafePointer<Void>) -> Int32 {
    let compareFunc: CompareFunc = UnsafeMutablePointer(thunk).memory
    return compareFunc(l,r)
}

extension Array where Element: Comparable {
    func quickSort() -> [Element] {
        var array = self
        var compare = Element.compare
        qsort_r(&array, array.count, strideof(Element), &compare, cmp)
        return array
    }
    
    mutating func quickSortInline() {
        self = quickSort()
    }
    
}

//var myArray = [3,1,2,17,4]
var myArray = ["Hello", "ABC", "abc", "test"]
myArray.quickSortInline()

print(myArray)