Class: Set

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.

Several methods accept any Enumerable object (implementing each) for greater flexibility: new, replace, merge, subtract, |, &, -, ^.

The equality of each couple of elements is determined according to Object#eql? and Object#hash, since Set uses Hash as storage.

Finally, if you are using class Set, you can also use Enumerable#to_set for convenience.

Example

  require 'set'
  s1 = Set.new [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: {6, 1, 2, "foo"}>
  s1.subset? s2                         # -> false
  s2.subset? s1                         # -> true

Public Class methods

[](*ary)

Creates a new set containing the given objects.

new(enum = nil) {|o| ...}

Creates a new set containing the elements of the given enumerable object.

If a block is given, the elements of enum are preprocessed by the given block.

Public Instance methods

&(enum)

Returns a new set containing elements common to the set and the given enumerable object.

+(enum)

Alias for #|

-(enum)

Returns a new set built by duplicating the set, removing every element that appears in the given enumerable object.

<<(o)

Alias for add

==(set)

Returns true if two sets are equal. The equality of each couple of elements is defined according to Object#eql?.

^(enum)

Returns a new set containing elements exclusive between the set and the given enumerable object. (set ^ enum) is equivalent to ((set | enum) - (set & enum)).

add(o)

Adds the given object to the set and returns self. Use merge to add several elements at once.

add?(o)

Adds the given object to the set and returns self. If the object is already in the set, returns nil.

classify( {|o| ...}

Classifies the set by the return value of the given block and returns a hash of {value => set of elements} pairs. The block is called once for each element of the set, passing the element as parameter.

e.g.:

  require 'set'
  files = Set.new(Dir.glob("*.rb"))
  hash = files.classify { |f| File.mtime(f).year }
  p hash    # => {2000=>#<Set: {"a.rb", "b.rb"}>,
            #     2001=>#<Set: {"c.rb", "d.rb", "e.rb"}>,
            #     2002=>#<Set: {"f.rb"}>}

clear()

Removes all elements and returns self.

collect!() {|o| ...}

Do collect() destructively.

delete(o)

Deletes the given object from the set and returns self. Use subtract to delete several items at once.

delete?(o)

Deletes the given object from the set and returns self. If the object is not in the set, returns nil.

delete_if() {|o| ...}

Deletes every element of the set for which block evaluates to true, and returns self.

difference(enum)

Alias for #-

divide(&func)

Divides the set into a set of subsets according to the commonality defined by the given block.

If the arity of the block is 2, elements o1 and o2 are in common if block.call(o1, o2) is true. Otherwise, elements o1 and o2 are in common if block.call(o1) == block.call(o2).

e.g.:

  require 'set'
  numbers = Set[1, 3, 4, 6, 9, 10, 11]
  set = numbers.divide { |i,j| (i - j).abs == 1 }
  p set     # => #<Set: {#<Set: {1}>,
            #            #<Set: {11, 9, 10}>,
            #            #<Set: {3, 4}>,
            #            #<Set: {6}>}>

each() {|o| ...}

Calls the given block once for each element in the set, passing the element as parameter.

empty?()

Returns true if the set contains no elements.

flatten()

Returns a new set that is a copy of the set, flattening each containing set recursively.

flatten!()

Equivalent to Set#flatten, but replaces the receiver with the result in place. Returns nil if no modifications were made.

include?(o)

Returns true if the set contains the given object.

initialize_copy(orig)

Copy internal hash.