title: How to check for NSDecimalNumber.zero() in Swift
body: <p>Using 'num1' as a comparison reference to determine if 'num2' or 'num3' are zero.  Have done this successfully in Objective-C, and am trying to do it in Swift:</p>
  
  <pre><code>let num1: NSDecimalNumber = NSDecimalNumber.zero()
  let num2: NSDecimalNumber = NSDecimalNumber.decimalNumberWithString("0")
  let num3: NSDecimalNumber = NSDecimalNumber.decimalNumberWithString("0.000001")
  
  if num1.compare(num2) == NSOrderedSame {
      println("They match")
  }
  </code></pre>
  
  <p>This attempt results in: "error: use of unresolved identifier 'NSOrderedSame'."
  What is the proper way to accomplish this in Swift?  (Have searched the book and web, but missing something possibly obvious, thank you).</p>