title: Scala: convert Option to Set
body: <p>How can I convert <code>Option</code> to <code>Set</code> easily, so that set contain one element if Option has element, and zero elements otherwise?</p>
  
  <p>I did that manually this way, but it's cumbersome:</p>
  
  <pre><code>option match {
    case Some(x) =&gt; Set(x)
    case None =&gt; Set()
  }
  </code></pre>