sealed trait Type
object Apple extends Type
object Orange extends Type
object Potato extends Type

object Item {
  def join(i1: Item, i2: Item): Item = Item(i1.t, i1.amount + i2.amount)
}
case class Item(t: Type, amount: Int)

val items = Seq[Item](Item(Apple, 1), Item(Apple, 30), Item(Orange, 1), Item(Apple, 12), Item(Potato, 50))