dementhiumShift.kt

fun <I: Item> ItemContainer<I>.dementhiumShift(predicate: (I) -> Boolean = Item::isInvalidItem) {
    val oldData: List<I> = items.toList()
    items.clear()
    var ptr = 0
    items.forEachIndexed { itemIndex, item ->
        if (predicate(item)) {
            set(ptr++, oldData[itemIndex])
        }
    }
}