Implementations
A set can be implemented in many ways. For example, one can use a list, ignoring the order of the elements and taking care to avoid repeated values. Sets are often implemented using various flavors of trees, tries, or hash tables.
A set can be seen, and implemented, as a (partial) associative array, in which the value of each key-value pair has the unit type.
Read more about this topic: Set (abstract Data Type)