title: how to rewrite the following for loop in swift 3 syntax?
body: <pre><code>for (int i = n-2; i &gt;= 0; --i)
  {
  ....
  }
  </code></pre>
  
  <p>the automatic translation of the above to swift 3 syntax is this</p>
  
  <pre><code>for i in n-2 ... 0 
  {
  }
  </code></pre>
  
  <p>this doesn't work, because n could be 1, in the c syntax, this is valid, the loop won't be triggered,</p>
  
  <p>but in the swift 3 syntax, this will cause runtime error.</p>