fun need_skip: Bool
	do
		if not are_sorted and not are_unique then
			return false
		else if are_sorted and are_unique then
			var max = -1
			for i in indices do
				if i <= max then return true
				max = i
			end
			return false
		else if are_sorted then
			var max = -1
			for i in indices do
				if i < max then return true
				max = i
			end
			return false
		else
			# are_unique
			for i in indices do
				if indices.count(i) > 1 then return true
			end
			return false
		end
	end