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.

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. 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)

Public Class Methods

[](*ary) click to toggle source

Creates a new set containing the given objects.

# File lib/set.rb, line 74
def self.[](*ary)
  new(ary)
end

new(enum = nil) { |o| ... } click to toggle source

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 83
def initialize(enum = nil, &block) # :yields: o
  @hash ||= Hash.new(false)

  enum.nil? and return

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

Public Instance Methods

&(enum) click to toggle source

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

# File lib/set.rb, line 439
def &(enum)
  n = self.class.new
  do_with_enum(enum) { |o| n.add(o) if include?(o) }
  n
end

Also aliased as: intersection

+(enum)

Alias for: |

-(enum) click to toggle source

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

# File lib/set.rb, line 432
def -(enum)
  dup.subtract(enum)
end

Also aliased as: difference

<(set)

Alias for: proper_subset?

<<(o)

Alias for: add

<=(set)

Alias for: subset?

==(other) click to toggle source

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 457
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) click to toggle source

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 449
def ^(enum)
  n = Set.new(enum)
  each { |o| n.add(o) unless n.delete?(o) }
  n
end

add(o) click to toggle source

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

# File lib/set.rb, line 330
def add(o)
  @hash[o] = true
  self
end

Also aliased as: <<

add?(o) click to toggle source

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 338
def add?(o)
  add(o) unless include?(o)
end

classify() { |o| ... } click to toggle source

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"}>}

Returns an enumerator if no block is given.

# File lib/set.rb, line 493
def classify # :yields: o
  block_given? or return enum_for(__method__) { size }

  h = {}

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

  h
end

clear() click to toggle source

Removes all elements and returns self.

# File lib/set.rb, line 162
def clear
  @hash.clear
  self
end

collect!() { |o| ... } click to toggle source

Replaces the elements with ones returned by collect(). Returns an enumerator if no block is given.

# File lib/set.rb, line 379
def collect!
  block_given? or return enum_for(__method__) { size }
  replace(self.class.new(self) { |o| yield(o) })
end

Also aliased as: map!

compare_by_identity() click to toggle source

Makes the set compare its elements by their identity and returns self. This method may not be supported by all subclasses of Set.

# File lib/set.rb, line 97
def compare_by_identity
  if @hash.respond_to?(:compare_by_identity)
    @hash.compare_by_identity
    self
  else
    raise NotImplementedError, "#{self.class.name}\##{__method__} is not implemented"
  end
end

compare_by_identity?() click to toggle source

Returns true if the set will compare its elements by their identity. Also see Set#compare_by_identity.

# File lib/set.rb, line 108
def compare_by_identity?
  @hash.respond_to?(:compare_by_identity?) && @hash.compare_by_identity?
end

delete(o) click to toggle source

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

# File lib/set.rb, line 344
def delete(o)
  @hash.delete(o)
  self
end

delete?(o) click to toggle source

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 351
def delete?(o)
  delete(o) if include?(o)
end

delete_if() { |o| ... } click to toggle source

Deletes every element of the set for which block evaluates to true, and returns self. Returns an enumerator if no block is given.

# File lib/set.rb, line 358
def delete_if
  block_given? or return enum_for(__method__) { size }
  # @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) click to toggle source

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

e.g.:

require 'set'
Set[1, 2, 3].disjoint? Set[3, 4] # => false
Set[1, 2, 3].disjoint? Set[4, 5] # => true

# File lib/set.rb, line 315
def disjoint?(set)
  !intersect?(set)
end

divide(&func) click to toggle source

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}>}>

Returns an enumerator if no block is given.

# File lib/set.rb, line 523
def divide(&func)
  func or return enum_for(__method__) { size }

  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) click to toggle source

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 322
def each(&block)
  block or return enum_for(__method__) { size }
  @hash.each_key(&block)
  self
end

empty?() click to toggle source

Returns true if the set contains no elements.

# File lib/set.rb, line 157
def empty?
  @hash.empty?
end

flatten() click to toggle source

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

# File lib/set.rb, line 216
def flatten
  self.class.new.flatten_merge(self)
end

flatten!() click to toggle source

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

# File lib/set.rb, line 222
def flatten!
  replace(flatten()) if any? { |e| e.is_a?(Set) }
end

include?(o) click to toggle source

Returns true if the set contains the given object.

Note that include? and member? do not test member equality using == as do other Enumerables.

See also Enumerable#include?

# File lib/set.rb, line 232
def include?(o)
  @hash[o]
end

Also aliased as: member?

initialize_clone(orig) click to toggle source

Clone internal hash.

Calls superclass method

# File lib/set.rb, line 130
def initialize_clone(orig)
  super
  @hash = orig.instance_variable_get(:@hash).clone
end

initialize_dup(orig) click to toggle source

Dup internal hash.

Calls superclass method

# File lib/set.rb, line 124
def initialize_dup(orig)
  super
  @hash = orig.instance_variable_get(:@hash).dup
end

inspect() click to toggle source

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

# File lib/set.rb, line 557
def inspect
  ids = (Thread.current[InspectKey] ||= [])

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

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

intersect?(set) click to toggle source

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

e.g.:

require 'set'
Set[1, 2, 3].intersect? Set[4, 5] # => false
Set[1, 2, 3].intersect? Set[3, 4] # => true

# File lib/set.rb, line 297
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() { |o| ... } click to toggle source

Deletes every element of the set for which block evaluates to false, and returns self. Returns an enumerator if no block is given.

# File lib/set.rb, line 369
def keep_if
  block_given? or return enum_for(__method__) { size }
  # @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) click to toggle source

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

# File lib/set.rb, line 405
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) click to toggle source

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

# File lib/set.rb, line 277
def proper_subset?(set)
  case
  when set.instance_of?(self.class)
    @hash < set.instance_variable_get(:@hash)
  when set.is_a?(Set)
    size < set.size && all? { |o| set.include?(o) }
  else
    raise ArgumentError, "value must be a set"
  end
end

Also aliased as: <

proper_superset?(set) click to toggle source

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

# File lib/set.rb, line 251
def proper_superset?(set)
  case
  when set.instance_of?(self.class)
    @hash > set.instance_variable_get(:@hash)
  when set.is_a?(Set)
    size > set.size && set.all? { |o| include?(o) }
  else
    raise ArgumentError, "value must be a set"
  end
end

Also aliased as: >

reject!(&block) click to toggle source

Equivalent to Set#delete_if, but returns nil if no changes were made. Returns an enumerator if no block is given.

# File lib/set.rb, line 387
def reject!(&block)
  block or return enum_for(__method__) { size }
  n = size
  delete_if(&block)
  self if size != n
end

replace(enum) click to toggle source

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

# File lib/set.rb, line 169
def replace(enum)
  if enum.instance_of?(self.class)
    @hash.replace(enum.instance_variable_get(:@hash))
    self
  else
    do_with_enum(enum)  # make sure enum is enumerable before calling clear
    clear
    merge(enum)
  end
end

select!(&block) click to toggle source

Equivalent to Set#keep_if, but returns nil if no changes were made. Returns an enumerator if no block is given.

# File lib/set.rb, line 396
def select!(&block)
  block or return enum_for(__method__) { size }
  n = size
  keep_if(&block)
  self if size != n
end

size() click to toggle source

Returns the number of elements.

# File lib/set.rb, line 151
def size
  @hash.size
end

Also aliased as: length

subset?(set) click to toggle source

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

# File lib/set.rb, line 264
def subset?(set)
  case
  when set.instance_of?(self.class)
    @hash <= set.instance_variable_get(:@hash)
  when set.is_a?(Set)
    size <= set.size && all? { |o| set.include?(o) }
  else
    raise ArgumentError, "value must be a set"
  end
end

Also aliased as: <=

subtract(enum) click to toggle source

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

# File lib/set.rb, line 417
def subtract(enum)
  do_with_enum(enum) { |o| delete(o) }
  self
end

superset?(set) click to toggle source

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

# File lib/set.rb, line 238
def superset?(set)
  case
  when set.instance_of?(self.class)
    @hash >= set.instance_variable_get(:@hash)
  when set.is_a?(Set)
    size >= set.size && set.all? { |o| include?(o) }
  else
    raise ArgumentError, "value must be a set"
  end
end

Also aliased as: >=

to_a() click to toggle source

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

# File lib/set.rb, line 181
def to_a
  @hash.keys
end

to_set(klass = Set, *args, &block) click to toggle source

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 190
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) click to toggle source

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

# File lib/set.rb, line 424
def |(enum)
  dup.merge(enum)
end

Also aliased as: +, union