This is true if Set is a proper list without duplicates.
- eliminate_duplicate(List, Set):
This is true when Set has the same elements as List, in the same order. Only the left-most copy of the duplicate is retained.
- intersection(Set1, Set2, Set3):
This is true if Set3 unifies with the intersection of Set1 and Set2.
- union(Set1, Set2, Set3):
This is true if Set3 unifies with the union of Set1 and Set2.
- subset(SubSet, Set):
This is true if all of the elements of SubSet also belong to Set.
- subtract(Set, Delete, Result):
Delete all of the elements from Set that occur in the set Delete, and unify the result with Result.