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sealed abstract class MyList[@specialized +A] {
def head: A
def tail: MyList[A]
def ::[@specialized B >: A](x: B): MyList[B] =
new Cons[B](x, this)
}
case object MyNil extends MyList[Nothing] {
def head = sys.error("nil")
def tail = sys.error("nil")
}
case class Cons[@specialized a](private val hd: a, tl: MyList[a]) extends MyList[a] {
def head = hd
def tail = tl
}
abstract class IntList extends MyList[Int]
object Main extends App {
val xs = 1 :: 2 :: 3 :: MyNil
println(xs)
}
/*
final class ConsI(hd1: Int, tl1: MyList[Int]) extends Cons[Int](hd1, tl1) {
override val hd = hd1
override val tl = tl1
}
*/
//class IntCons(_hd: Int, _tl: MyList[Int]) extends Cons[Int](_hd, _tl)
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