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.

Set uses Hash as storage, so you must note the following points:

• Equality of elements is determined according to Object#eql? and Object#hash. Use Set#compare_by_identity to make a set compare its elements by their identity.

• Set assumes that the identity of each element does not change while it is stored. Modifying an element of a set will render the set to an unreliable state.

• When a string is to be stored, a frozen copy of the string is stored instead unless the original string is already frozen.

The comparison operators <, >, <=, and >= are implemented as shorthand for the {proper_,}{subset?,superset?} methods. The <=> operator reflects this order, or return nil for sets that both have distinct elements ({x, y} vs. {x, z} for example).

Add this line to your application's Gemfile:

gem 'set'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install set

require 'set'
s1 = Set[1, 2]                        #=> #<Set: {1, 2}>
s2 = [1, 2].to_set                    #=> #<Set: {1, 2}>
s1 == s2                              #=> true
s1.add("foo")                         #=> #<Set: {1, 2, "foo"}>
s1.merge([2, 6])                      #=> #<Set: {1, 2, "foo", 6}>
s1.subset?(s2)                        #=> false
s2.subset?(s1)                        #=> true

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

Bug reports and pull requests are welcome on GitHub at https://github.com/ruby/set.

Feature requests should also go to https://bugs.ruby-lang.org/ for wider audience and discussion.

The gem is available as open source under either the terms of the 2-Clause BSD License. When bundled with Ruby, you can distribute/modify this program under the same terms of Ruby.