title: Swift 3 Set Operations Subtract
body: <pre><code>var studSubj: [String: Set&lt;String&gt;] = [
  
      "Juan":["OOP","WEBAPP","MOBILEAPP","XML"],
  
      "Pedro":["XML","DATASTRUCT","OOP","WEBAPP"],
  
      "Jose":["WEBAPP","XML","SYSAD"]];
  
  print(studSubj["Juan"]!.subtract(studSubj["Pedro"]!));
  </code></pre>
  
  <p>I'm using IBM Swift Sandbox to simulate the code. The only output i see is (), is there anything wrong with my code?</p>
  
  <p>[EDIT]
  I am subtracting to get the unique subjects taken by juan.</p>