An unordered set.
An immutable hash set using [hash array mapped tries] 1.
Most operations on this set are O(logx n) for a
suitably high x that it should be nearly O(1) for most sets.
Because of this, it’s a great choice for a generic set as long as
you don’t mind that values will need to implement
Values will have a predictable order based on the hasher
being used. Unless otherwise specified, this will be the standard
Construct a set from a sequence of values.