Compile and Execute Scala Online

object HelloWorld {
    
  sealed trait List[+A]
    case object Nil extends List[Nothing]
    
    case class Cons[+A](head: A, tail: List[A]) extends List[A]
    
    object List {
        
    def sum(ints: List[Int]): Int = ints match {
    case Nil => 0
    case Cons(x,xs) => x + sum(xs)
    }
    def product(ds: List[Double]): Double = ds match {
    case Nil => 1.0
    case Cons(0.0, _) => 0.0
    case Cons(x,xs) => x * product(xs)
    }
    def apply[A](as: A*): List[A] =
    if (as.isEmpty) Nil
    else Cons(as.head, apply(as.tail: _*))
    
    def tail[A](ls: List[A]): List[A] = ls match {
        case Nil => Nil
        case Cons(_,t) => t
    }
    
    def setHead[A](ls: List[A], nHead: A): List[A] = ls match {
        case Nil => Nil
        case Cons(_,t) => Cons(nHead,t)
    }
    
    def drop[A](l: List[A], n: Int): List[A] = l match {
        case Cons(h,t) => if (n>0) drop(t,n-1) else l
    }
    
    
    def dropWhile[A](l: List[A], f: A => Boolean): List[A] = l match  {
        case Nil => Nil
        case Cons(h,t) => if (!f(h)) l else dropWhile(t,f)
    }

    def init[A](l: List[A]): List[A] = l match {
        case Nil => Nil
        case (_,Nil) => Nil
        case Cons(h,t) => Cons(h,init(t))
        
    }

    
    }
    
   def main(args: Array[String]) {
       
      val a = List(22,2,3,4,5) match { case Cons(_,t) => t }
      
      val b=  List.dropWhile(List(22,11,22,44,55), (x:Int) => x==22 )
      
      val c=  List.drop(List(22,11,22,44,55), 2 )
      
       
      println(c)
   }
}