title: Scala Sets Immutability
body: <pre><code>scala&gt; var immSet = Set("A", "B")
  immSet: scala.collection.immutable.Set[String] = Set(A, B)
  
  scala&gt; immSet += "C"
  
  scala&gt; println(immSet)
  Set(A, B, C)
  </code></pre>
  
  <p>I wonder, what is the advantage I am getting by allowing <code>var</code> to be used with with an immutable Set? Am I not losing immutability in this case? </p>