Amita:

I have just started with Scala so please forgive if this turns out to be silly.

I am trying to implement a linked list in Scala. So, I created a file that contains MyList class and others in MyList.scala:

abstract class MyList[+A] {
  def head : A
  def tail : MyList[A]
  def isEmpty : Boolean
  def add[B>:A](element: B) : MyList[B] = new MyNonEmptyList[B](element,this)
}

object MyEmptyList extends MyList[Nothing]{
  override def head: Nothing = throw new NoSuchElementException("Head of an Empty list : ")

  override def tail: MyList[Nothing] = throw  new NoSuchElementException("Tail of an Empty list!" )

  override def isEmpty: Boolean = true

  override def toString : String = ""
}

case class MyNonEmptyList[A] (head: A, tail:MyList[A]) extends MyList[A]{
  override def isEmpty: Boolean = false
  override def toString : String = head + ", " + tail.toString
}

After carving out the basic functionalities, it was time to test it. So, I created a scala worksheet test.sc:

object test{
  val list = MyNonEmptyList(1,MyEmptyList)
  val b = list.head
}

Now, when I try to run the code (on IntelliJ), I get the following error:

Error:(1, 18) not found: value MyNonEmptyList
lazy val list = MyNonEmptyList(1,MyEmptyList)
                ^

I do not get the reason behind this error. When I do ctrl+click, I am redirected to the source in MyList.scala file.