This library provides the Set class, which deals with a collection of unordered
values with no duplicates. It is a hybrid of Array's intuitive inter-operation
facilities and Hash's fast lookup.

The method to_set is added to Enumerable for convenience.

Set implements a collection of unordered values with no duplicates. This is a
hybrid of Array's intuitive inter-operation facilities and Hash's fast lookup.

Set is easy to use with Enumerable objects (implementing each). Most of the
initializer methods and binary operators accept generic Enumerable objects
besides sets and arrays. An Enumerable object can be converted to Set using the
to_set method.

WWW: https://github.com/ruby/set