title: How does the Scala toSeq:_* syntax work?
body: <p>In the Scala code</p>
  
  <pre><code>val s = Set(List(1,2,3).toSeq:_*)
  </code></pre>
  
  <p>how does the <code>toSeq:_*</code> syntax work? I know what the code does, I know what <code>toSeq</code> does, I understand <code>List(1,2,3).toSeq:Seq[Int]</code>. Is <code>toSeq:_*</code> a special case?</p>