title: Expected ',' separator error on formula in Swift
body: <p>I have a formula to calculate wind chill in my app, which requires air temperature and wind speed inputs. I used the following calculation from the website MentalFloss:</p>
  
  <p>Wind Chill = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16) where T is air temperature in degrees fahrenheit and V is wind speed in mph. </p>
  
  <p>Here is my code:</p>
  
  <pre><code>import UIKit
  
  infix operator ** {}
  
  func ** (num: Double, power: Double) -&gt; Double{
      return pow(num, power)
  }
  
  
  class FirstViewController: UIViewController {    
      @IBOutlet weak var txtAirTemp: UITextField!
  
      @IBOutlet weak var txtWindSpeed: UITextField!
  
      @IBOutlet weak var lblWindChill1: UILabel!
  
  
  
      override func viewDidLoad() {
          super.viewDidLoad()
          // Do any additional setup after loading the view, typically from a nib.
      }
  
      override func didReceiveMemoryWarning() {
          super.didReceiveMemoryWarning()
          // Dispose of any resources that can be recreated.
      }    
  
      @IBAction func btnShowWindChill(sender: UIButton) {
  
          var airTemp = Double((txtAirTemp.text as NSString).doubleValue)
          var windSpeed = Double((txtWindSpeed.text as NSString).doubleValue)
  
          lblWindChill1.text = "\((35.74 + 0.6215(airTemp) - 35.75(windSpeed**0.16) +       ((0.4275(airTemp))windSpeed**0.16)))"
      }
  
      @IBAction func btnIncreaseValue(sender: UIButton) {
      }
  
  
      @IBAction func btnDecreaseValue(sender: UIButton) {
      }
  
  }
  </code></pre>
  
  <p>I'm getting the error "Expected ',' separator" in the lblWindChill1.text = formula lines in my btnShowWindChill event. Also there is a yellow arrow under the 'w' in windSpeed**0.16)))" toward the end of the formula, wanting to refactor, which doesn't help me. I added preceding zeros to my decimal numbers to no avail. </p>
  
  <p>Is this a casting problem, or a problem with how I handled the exponent? Can someone please give me some ideas to fix this? BTW I haven't done anything with the btnIncreaseValue and btnDecreaseValue events yet. </p>
  
  <p>If you can't tell, I'm somewhat of a beginner at this.</p>
  
  <p>Thank you for whatever you can suggest!</p>