Sequence wildcards and sequence arguments in Scala

sequence.scala

import scala.collection.immutable.Queue

val q = Queue(1, 2, 3)

// When pattern matching against a sequence, the sequence wildcard _*
// can be used as the last pattern and will match an arbitrary number of
// elements. To bind the matched sequence to a variable, use the form
// `x @ _*`:
val restSeq = q match { case Queue(x, xs @ _*) => xs }
// --> rest: Seq[Int] = Queue(2, 3)

// Scala also supports sequence arguments to functions that take
// repeated parameters. To indicate that a sequence should be
// expanded, follow it with `: _*`:
val restQ = Queue(restSeq: _*)
// --> restQ: scala.collection.immutable.Queue[Int] = Queue(2, 3)