title: Swift loop from upper value to lower value
body: <p>I have a Swift for loop defined like this:</p>
  
  <pre><code> for i in 20...1 {
      array.append(i)
   }
  </code></pre>
  
  <p>But I get a crash with message </p>
  
  <pre><code>  Thread 1: Fatal error: Can't form Range with upperBound &lt; lowerBound
  </code></pre>
  
  <p>What is the fix?</p>