subset?: func [
        {Returns true if A is a subset of B; false otherwise.}
        a [series! bitset!]
        b [series! bitset!]
    ] [
        empty? exclude a b
    ]

    superset?: func [
        {Returns true if set1 is a superset of set2; false otherwise.}
        set1 [series! bitset!]
        set2 [series! bitset!]
    ][
        subset? set2 set1
    ]