Make sync function async

asyncSyncFunction.swift

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

import UIKit
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true


let userQueue = DispatchQueue.global(qos: .userInitiated)
let defaultQueue = DispatchQueue.global()


func slowAdd(_ input: (Int, Int)) -> Int {
  sleep(2)
  return input.0 + input.1
}

// TODO: Dispatch slowAdd to userQueue

func asyncSlowAdd(_ input: (Int, Int),
                  runQueue: DispatchQueue,
                  comletionQueue: DispatchQueue,
                  completion: @escaping (Int) ->() ) {
  runQueue.async {
    let result = slowAdd(input)
    comletionQueue.async {
      completion(result)
    }
  }
}


asyncSlowAdd((2,3), runQueue: userQueue, comletionQueue: defaultQueue) { result in
  print(result)
}
print("after calling asyncSlowAdd")


sleep(3)
PlaygroundPage.current.finishExecution()