+
+ # 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[E]): 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