# Does the collection contain exactly all the elements of `other`?
	#
	# The same elements must be present in both `self` and `other`,
	# but the order of the elements in the collections are not considered.
	#
	#     assert [1..3].has_exactly([3,1,2]) == true  # the same elements
	#     assert [1..3].has_exactly([3,1])   == false # 2 is not in the array
	#     assert [1..2].has_exactly([3,1,2]) == false # 3 is not in the range
	#
	# Repeated elements must be present in both collections in the same amount.
	# So basically it is a multi-set comparison.
	#
	#     assert [1,2,3,2].has_exactly([1,2,2,3]) == true  # the same elements
	#     assert [1,2,3,2].has_exactly([1,2,3])   == false # more 2 in the first array
	#     assert [1,2,3].has_exactly([1,2,2,3])   == false # more 2 in the second array
	#
	# Note that the default implementation is general and correct for any lawful Collections.
	# It is memory-efficient but relies on `count` so may be CPU-inefficient for some kind of collections.
	fun has_exactly(other: Collection[nullable Object]): Bool
	do
		if length != other.length then return false
		for e in self do if self.count(e) != other.count(e) then return false
		return true
	end