package kapitel_03

/**
 * Beispiel aus
 *
 * - Algorithmen und Datenstrukturen für Dummies
 *   - von Andreas Gogol-Döring und Thomas Letschert
 *   - Verlag Wiley-VCH; Oktober 2019
 *  - Kapitel 3, Daten und ihre Struktur
 *
 * @author A. Gogol-Döring, Th. Letschert
 */

object AuD_03_05_ListSum_App extends App {

  abstract class IntList
  case object Nil                          extends IntList
  case class Cons(head: Int, tail:IntList) extends IntList

  def FList(n: Int): IntList = {

    def F(x: Int): Int = if (x == 0) 1 else x * F(x-1)

    var l: IntList = Nil
    for (i <- 0 to n)
      l = Cons(F(i), l)

    l
  }

  def ListSum(lst: IntList): Int = {
    var s = 0
    var lstVar: IntList = lst
    while (lstVar != Nil) {
      lstVar match {
        case Cons(v, rest) =>
          s = s + v
          lstVar = rest
        case _ =>
      }
    }
    s
  }

  def ListSumR(lst: IntList): Int = lst match {
    case Cons(v, rest)  => v + ListSumR(rest)
    case Nil            => 0
  }

  val l = Cons(1, Cons(2, Cons(3, Cons(4, Cons(5, Nil)))))

  println(ListSum(l))
  println(ListSumR(l))

}