Set

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.

Comparison

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).

Example

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

Contact

• Akinori MUSHA <[email protected]> (current maintainer)