Case Classes and Pattern Matching

IntTreeTest.scala

object IntTreeTest {
   abstract class IntTree
   case object EmptyTree extends IntTree
   case class Node(elem: Int, left: IntTree, right: IntTree) extends IntTree
   
   def contains(t: IntTree, v: Int): Boolean = t match {
      case EmptyTree => false
      case Node(e, l, r) => 
         if (v < e) contains(l, v)
         else if (v > e) contains(r, v)
         else true
   }
   
   def insert(t: IntTree, v: Int): IntTree = t match {
      case EmptyTree => Node(v, EmptyTree, EmptyTree)
      case Node(e, l, r) =>
         if (v < e) Node(e, insert(l, v), r)
         else if (v > e) Node(e, l, insert(r, v))
         else t
   }
   
   def main(args: Array[String]) {
      val t = insert(insert(insert(insert(insert(EmptyTree, 11), 1), 20), 18), 25)
      println("Tree is: " + t)
      println("Does Tree contain 20?: " + (if (contains(t, 20)) "Yes" else "No"))
      println("Does Tree contain 15?: " + (if (contains(t, 15)) "Yes" else "No"))
   }
}