Quick Sort in Swift 3

QuickSortSwift3.swift

func quickSort<T: Comparable>(array: [T]) -> [T] {
    guard !array.isEmpty else { return [] }
    let pivot = array.first!
    let arrayLessThanOrEqualToPivot = array.dropFirst().filter { $0 <= pivot }
    let arrayGreaterThanOrEqualToPivot = array.dropFirst().filter { $0 > pivot }
    return quickSort(arrayLessThanOrEqualToPivot) + [Int(pivot)] + quickSort(arrayGreaterThanOrEqualToPivot)
}