title: How to return an optional tuple
body: <p>I have function that finds two ranges for a substring in the string1 and string2, and it returns the tuple</p>
  
  <pre><code>(Range&lt;String.Index&gt;!, Range&lt;String.Index&gt;!)  
  </code></pre>
  
  <p>I need tuples to store them later in an array. The problem comes when no ranges were found. How to deal with this, what function should return – empty tuple or tuple with nil (nil, nil) ?   </p>