Scala example source code file (patterns.scala)

This example Scala source code file (patterns.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

branch, branch, int, int, leaf, leaf, list, none, option, pair, some, string, tree, tree

The Scala patterns.scala source code

package examples

object patterns {

  trait Tree
  case class Branch(left: Tree, right: Tree) extends Tree
  case class Leaf(x: Int) extends Tree

  val tree1 = Branch(Branch(Leaf(1), Leaf(2)), Branch(Leaf(3), Leaf(4)))

  def sumLeaves(t: Tree): Int = t match {
    case Branch(l, r) => sumLeaves(l) + sumLeaves(r)
    case Leaf(x) => x
  }

  def find[a,b](it: Iterator[Pair[a, b]], x: a): Option[b] = {
    var result: Option[b] = None
    var found = false
    while (it.hasNext && !found) {
      val Pair(x1, y) = it.next
      if (x == x1) { found = true; result = Some(y) }
    }
    result
  }

  def printFinds[a](xs: List[Pair[a, String]], x: a) =
    find(xs.iterator, x) match {
      case Some(y) => System.out.println(y)
      case None => System.out.println("no match")
    }

  def main(args: Array[String]) {
    println("sum of leafs=" + sumLeaves(tree1))
    printFinds(List(Pair(3, "three"), Pair(4, "four")), 4)
  }
}