Haskell quicksort implementation in swift

quicksort.swift

//: Playground - noun: a place where people can play

/*: Quicksort
 I wanted to see how closely swift can resemble the Haskell quicksort example

 ````
 quicksort :: (Ord a) => [a] -> [a]
 quicksort [] = []
 quicksort (x:xs) =
    let smallerSorted = quicksort [a | a <- xs, a <= x]
        biggerSorted = quicksort [a | a <- xs, a > x]
    in smallerSorted ++ [x] ++ biggerSorted
 ````
 */

import Cocoa

// Array extension from: https://chris.eidhof.nl/post/swift-tricks
extension Array
{
    var match: (x: Element, xs: [Element])?
    {
        return isEmpty ? (self[0], Array(self[1..<count])) : nil
    }
}

func quicksort(_ xs: [Int]) -> [Int]
{
    switch xs.match {
    case .none:
        return []
    case .some(let x, let xs):
        let smallerSorted = quicksort(xs.filter({ $0 <= x }))
        let biggerSorted  = quicksort(xs.filter({ $0 > x}))
        
        return smallerSorted + [x] + biggerSorted
    }
}

let toSort = [42, 12, 88, 62, 63, 56, 1, 77, 88, 97, 97, 20, 45, 91, 62, 2, 15, 31, 59, 5]
quicksort(toSort)