So the BCL thinking of implementing a set collection for a future release and we would like to get you our blog reading public opinion on what scenarios are important to you for a Set collection. The collection will likely have the standard ICollection<T> APIs like Add, Remove, Clear, and Count and we would likely support the following scenarios:

Test for membership (ie does element A exist in set T)

Test for subset (ie is set T a subset of set U)

Intersection

Complement

But what other functions should a Set collection be able to perform?