An example program to show the power of pattern matching

Sequence.scala

sealed trait Sequence[+T]
case class Cons[+T](head: T, tail: Sequence[T]) extends Sequence[T]
case object Empty extends Sequence[Nothing]

object Main {
  def last2[T](list: Sequence[T]): Sequence[T] = list match {
    case result@Cons(_, Cons(_, Empty)) => result
    case Empty =>
      sys.error("list should not be empty")
    case Cons(_, Empty) =>
      sys.error("list should have two elements at least")
    case Cons(_, xs) => last2(xs)
  }

  def main(args: Array[String]): Unit = {
    // Cons(2,Cons(3, Empty))
    println(last2(Cons(1, Cons(2, Cons(3, Empty)))))
  }
}