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

def join(i1: Item, i2: Item): Item = new Item(i1.t, i1.amount + i2.amount)
class Item(val t: Type, val amount: Int)

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