subset? and superset? functions
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
]