package kapitel_05

/**
 * Beispiel aus
 *
 * - Algorithmen und Datenstrukturen für Dummies
 *   - von Andreas Gogol-Döring und Thomas Letschert
 *   - Verlag Wiley-VCH; Oktober 2019
 *  - Kapitel 5, Bäume: Immer einer über den anderen
 *
 * @author A. Gogol-Döring, Th. Letschert
 */

object AuD_05_11_ExpressionTree_App extends App {

  sealed abstract class Expr
  case class Number(number: Int) extends Expr
  case class Add(left: Expr, right: Expr) extends Expr
  case class Sub(left: Expr, right: Expr) extends Expr
  case class Mult(left: Expr, right: Expr) extends Expr

  def Evaluate(expr: Expr): Int = expr match {
    case Number(n) => n
    case Add(l, r) => Evaluate(l) + Evaluate(r)
    case Sub(l, r) => Evaluate(l) - Evaluate(r)
    case Mult(l, r) => Evaluate(l) * Evaluate(r)
  }

  val two = Number(2)
  val three = Number(3)
  val four = Number(4)
  val five = Number(5)
  val threeTimesFour = Mult(three, four)
  val twoPlusThreeTimesFour = Add(two, threeTimesFour)
  val twoPlusThreeTimesFourMinusFive = Sub(twoPlusThreeTimesFour, five)

  println(Evaluate(twoPlusThreeTimesFourMinusFive))

}