# Are the elements in the generated sequences sorted?
	# Default `true`.
	#
	# When `true`, the original order is preserved.
	#
	# Elements are compared by their order in the base collection,
	# not by their intrinsic value or comparability.
	#
	# ~~~~
	# var xs = [1, 1, 2]
	# var cxs = new CombinationCollection[Int](xs, 2)
	# cxs.are_sorted = true
	# assert cxs.to_a == [[1,1], [1,2], [1, 2]]
	# cxs.are_sorted = false
	# assert cxs.to_a == [[1,1], [1,2], [1, 1], [1, 2], [2, 1], [2, 1]]
	# ~~~~
	var are_sorted = true is writable