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.

  • 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. However, the <=> operator is intentionally left out because not every pair of sets is comparable. ({x,y} vs. {x,z} for example)

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: {1, 2, "foo", 6}>
s1.subset? s2                         # -> false
s2.subset? s1                         # -> true

Contact

- Akinori MUSHA <knu@iDaemons.org> (current maintainer)
Methods
#
A
C
D
E
F
I
K
L
M
N
P
R
S
T
U
#
Included Modules
Constants
InspectKey = :__inspect_key__
 
Class Public methods
[](*ary)

Creates a new set containing the given objects.

# File lib/set.rb, line 71
def self.[](*ary)
  new(ary)
end
new(enum = nil)

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.

# File lib/set.rb, line 80
def initialize(enum = nil, &block) # :yields: o
  @hash ||= Hash.new

  enum.nil? and return

  if block
    do_with_enum(enum) { |o| add(block[o]) }
  else
    merge(enum)
  end
end
Instance Public methods
&(enum)

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

Also aliased as: intersection
# File lib/set.rb, line 385
def &(enum)
  n = self.class.new
  do_with_enum(enum) { |o| n.add(o) if include?(o) }
  n
end
+(enum)
Alias for: |
-(enum)

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

Also aliased as: difference
# File lib/set.rb, line 378
def -(enum)
  dup.subtract(enum)
end
<(set)
Alias for: proper_subset?
<<(o)
Alias for: add
<=(set)
Alias for: subset?
==(other)

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

# File lib/set.rb, line 403
def ==(other)
  if self.equal?(other)
    true
  elsif other.instance_of?(self.class)
    @hash == other.instance_variable_get(:@hash)
  elsif other.is_a?(Set) && self.size == other.size
    other.all? { |o| @hash.include?(o) }
  else
    false
  end
end
>(set)
Alias for: proper_superset?
>=(set)
Alias for: superset?
^(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)).

# File lib/set.rb, line 395
def ^(enum)
  n = Set.new(enum)
  each { |o| if n.include?(o) then n.delete(o) else n.add(o) end }
  n
end
add(o)

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

Also aliased as: <<
# File lib/set.rb, line 269
def add(o)
  @hash[o] = true
  self
end
add?(o)

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

# File lib/set.rb, line 277
def add?(o)
  if include?(o)
    nil
  else
    add(o)
  end
end
classify()

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"}>}
# File lib/set.rb, line 437
def classify # :yields: o
  block_given? or return enum_for(__method__)

  h = {}

  each { |i|
    x = yield(i)
    (h[x] ||= self.class.new).add(i)
  }

  h
end
clear()

Removes all elements and returns self.

# File lib/set.rb, line 135
def clear
  @hash.clear
  self
end
collect!()

Replaces the elements with ones returned by collect().

Also aliased as: map!
# File lib/set.rb, line 323
def collect!
  block_given? or return enum_for(__method__)
  set = self.class.new
  each { |o| set << yield(o) }
  replace(set)
end
delete(o)

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

# File lib/set.rb, line 287
def delete(o)
  @hash.delete(o)
  self
end
delete?(o)

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

# File lib/set.rb, line 294
def delete?(o)
  if include?(o)
    delete(o)
  else
    nil
  end
end
delete_if()

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

# File lib/set.rb, line 304
def delete_if
  block_given? or return enum_for(__method__)
  # @hash.delete_if should be faster, but using it breaks the order
  # of enumeration in subclasses.
  select { |o| yield o }.each { |o| @hash.delete(o) }
  self
end
difference(enum)
Alias for: -
disjoint?(set)

Returns true if the set and the given set have no element in common. This method is the opposite of intersect?.

# File lib/set.rb, line 254
def disjoint?(set)
  !intersect?(set)
end
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}>}>
# File lib/set.rb, line 466
def divide(&func)
  func or return enum_for(__method__)

  if func.arity == 2
    require 'tsort'

    class << dig = {}         # :nodoc:
      include TSort

      alias tsort_each_node each_key
      def tsort_each_child(node, &block)
        fetch(node).each(&block)
      end
    end

    each { |u|
      dig[u] = a = []
      each{ |v| func.call(u, v) and a << v }
    }

    set = Set.new()
    dig.each_strongly_connected_component { |css|
      set.add(self.class.new(css))
    }
    set
  else
    Set.new(classify(&func).values)
  end
end
each(&block)

Calls the given block once for each element in the set, passing the element as parameter. Returns an enumerator if no block is given.

# File lib/set.rb, line 261
def each(&block)
  block or return enum_for(__method__)
  @hash.each_key(&block)
  self
end
empty?()

Returns true if the set contains no elements.

# File lib/set.rb, line 130
def empty?
  @hash.empty?
end
flatten()

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

# File lib/set.rb, line 189
def flatten
  self.class.new.flatten_merge(self)
end
flatten!()

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

# File lib/set.rb, line 195
def flatten!
  if detect { |e| e.is_a?(Set) }
    replace(flatten())
  else
    nil
  end
end
include?(o)

Returns true if the set contains the given object.

Also aliased as: member?
# File lib/set.rb, line 204
def include?(o)
  @hash.include?(o)
end
initialize_copy(orig)

Copy internal hash.

# File lib/set.rb, line 104
def initialize_copy(orig)
  @hash = orig.instance_variable_get(:@hash).dup
end
inspect()

Returns a string containing a human-readable representation of the set. (“#<Set: {element1, element2, …}>”)

# File lib/set.rb, line 500
def inspect
  ids = (Thread.current[InspectKey] ||= [])

  if ids.include?(object_id)
    return sprintf('#<%s: {...}>', self.class.name)
  end

  begin
    ids << object_id
    return sprintf('#<%s: {%s}>', self.class, to_a.inspect[1..-2])
  ensure
    ids.pop
  end
end
intersect?(set)

Returns true if the set and the given set have at least one element in common.

# File lib/set.rb, line 243
def intersect?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  if size < set.size
    any? { |o| set.include?(o) }
  else
    set.any? { |o| include?(o) }
  end
end
intersection(enum)
Alias for: &
keep_if()

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

# File lib/set.rb, line 314
def keep_if
  block_given? or return enum_for(__method__)
  # @hash.keep_if should be faster, but using it breaks the order of
  # enumeration in subclasses.
  reject { |o| yield o }.each { |o| @hash.delete(o) }
  self
end
length()
Alias for: size
map!()
Alias for: collect!
member?(o)
Alias for: include?
merge(enum)

Merges the elements of the given enumerable object to the set and returns self.

# File lib/set.rb, line 351
def merge(enum)
  if enum.instance_of?(self.class)
    @hash.update(enum.instance_variable_get(:@hash))
  else
    do_with_enum(enum) { |o| add(o) }
  end

  self
end
proper_subset?(set)

Returns true if the set is a proper subset of the given set.

Also aliased as: <
# File lib/set.rb, line 234
def proper_subset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if set.size <= size
  all? { |o| set.include?(o) }
end
proper_superset?(set)

Returns true if the set is a proper superset of the given set.

Also aliased as: >
# File lib/set.rb, line 218
def proper_superset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if size <= set.size
  set.all? { |o| include?(o) }
end
reject!(&block)

Equivalent to #delete_if, but returns nil if no changes were made.

# File lib/set.rb, line 333
def reject!(&block)
  block or return enum_for(__method__)
  n = size
  delete_if(&block)
  size == n ? nil : self
end
replace(enum)

Replaces the contents of the set with the contents of the given enumerable object and returns self.

# File lib/set.rb, line 142
def replace(enum)
  if enum.instance_of?(self.class)
    @hash.replace(enum.instance_variable_get(:@hash))
  else
    clear
    merge(enum)
  end

  self
end
select!(&block)

Equivalent to #keep_if, but returns nil if no changes were made.

# File lib/set.rb, line 342
def select!(&block)
  block or return enum_for(__method__)
  n = size
  keep_if(&block)
  size == n ? nil : self
end
size()

Returns the number of elements.

Also aliased as: length
# File lib/set.rb, line 124
def size
  @hash.size
end
subset?(set)

Returns true if the set is a subset of the given set.

Also aliased as: <=
# File lib/set.rb, line 226
def subset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if set.size < size
  all? { |o| set.include?(o) }
end
subtract(enum)

Deletes every element that appears in the given enumerable object and returns self.

# File lib/set.rb, line 363
def subtract(enum)
  do_with_enum(enum) { |o| delete(o) }
  self
end
superset?(set)

Returns true if the set is a superset of the given set.

Also aliased as: >=
# File lib/set.rb, line 210
def superset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if size < set.size
  set.all? { |o| include?(o) }
end
to_a()

Converts the set to an array. The order of elements is uncertain.

# File lib/set.rb, line 154
def to_a
  @hash.keys
end
to_set(klass = Set, *args, &block)

Returns self if no arguments are given. Otherwise, converts the set to another with klass.new(self, *args, &block).

In subclasses, returns klass.new(self, *args, &block) unless overridden.

# File lib/set.rb, line 163
def to_set(klass = Set, *args, &block)
  return self if instance_of?(Set) && klass == Set && block.nil? && args.empty?
  klass.new(self, *args, &block)
end
union(enum)
Alias for: |
|(enum)

Returns a new set built by merging the set and the elements of the given enumerable object.

Also aliased as: +, union
# File lib/set.rb, line 370
def |(enum)
  dup.merge(enum)
end