functional list

simple_list.scala

sealed trait MyList[+A]

case object Nil extends MyList[Nothing]
case class Cons[+A] (head: A, tail: MyList[A]) extends MyList[A]





object HelloWorld {
    
    def sum_int_list(xs: MyList[Int]): Int = xs match {
    case Nil => 0
    case Cons(x, ys) => x + sum_int_list(ys)
}
    
   def main(args: Array[String]) {
       val list: MyList[Int] = Cons(1, Cons(2, Cons(3, Nil)))
      println(sum_int_list(list))
   }
}