Haskell style quicksort in Swift

quicksort.hs

quicksort :: (Ord a) => [a] -> [a]
quicksort [] = []
quicksort (x:xs) =
  let smallOrEqual = filter (<= x) xs
      larger = filter (> x) xs
   in quicksort smallOrEqual ++ [x] ++ quicksort larger 

quicksort.swift

extension Array {
    var decompose : (head: Element, tail: [Element])? {
        return (count > 0) ? (self[0], Array(self[1..<count])) : nil
    }
}

func quickSort<T: Comparable>(_ input:[T]) -> [T] {
    guard let (x, xs) = input.decompose else { return [] }
    let smallOrEqual = xs.filter { $0 <= x }
    let larger = xs.filter { $0 > x }
    return quickSort(smallOrEqual) + Array([x]) + quickSort(larger)
}

let list = [0, 7, 11, 2, 10, 13, 4, -3, 2, 15, 32, -4, 27]
quickSort(list)