title: Scala initialize set from another set
body: <p>It is not clear how to create a new Set from an existing one.</p>
  
  <pre><code>scala&gt; val s = Set(1,2,3)
  </code></pre>
  
  <p>Try adding s directly in constructor:</p>
  
  <pre><code>scala&gt; val v = Set(s)
  v: scala.collection.mutable.Set[scala.collection.mutable.Set[Int]] = Set(Set(1, 2, 3))
  </code></pre>
  
  <p>Um that's a <em>nested</em> set..</p>
  
  <p>So let us try to take each element :</p>
  
  <pre><code>val v = Set[Int](s:_*)
  &lt;console&gt;:13: error: type mismatch;
   found   : scala.collection.mutable.Set[Int]
   required: Seq[Int]
         val v = Set[Int](s:_*)
  </code></pre>
  
  <p>How about a list?</p>
  
  <pre><code>val v = Set(  s.toList)
  v: scala.collection.mutable.Set[List[Int]] = Set(List(1, 2, 3))
  </code></pre>