title: How to get index(of:) to return multiple indices?
body: <p>Here is a group array.</p>
  
  <pre><code>var group = ["H","H","E","D",
               "G","D","G","E",
               "D","B","A","B",
               "A","A","G","C",
               "C","H","D","G",
               "H","B","E","F",
               "F","C","E","A",
               "B","C","F","F"]
  </code></pre>
  
  <p>I want to do something like this to find indices of "A".</p>
  
  <pre><code>group.index(of: "A"!)
  </code></pre>
  
  <p>But this will return only first index, but not other indices for next three "A"s.</p>
  
  <pre><code>print(group.index(of: "A")!) //10
  </code></pre>
  
  <p>What do I do to get the program to return all four indices for "A"?</p>