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/Ruby 3

class Set

Parent:
Object
Included modules:
Enumerable

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

Public Class Methods

[](*ary) Show source
# File lib/set.rb, line 73
def self.[](*ary)
  new(ary)
end

Creates a new set containing the given objects.

Set[1, 2]                   # => #<Set: {1, 2}>
Set[1, 2, 1]                # => #<Set: {1, 2}>
Set[1, 'c', :s]             # => #<Set: {1, "c", :s}>
json_create(object) Show source
# File ext/json/lib/json/add/set.rb, line 10
def self.json_create(object)
  new object['a']
end

Import a JSON Marshalled object.

method used for JSON marshalling support.

new(enum = nil) { |o| ... } Show source
# File lib/set.rb, line 88
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

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.

Set.new([1, 2])                       #=> #<Set: {1, 2}>
Set.new([1, 2, 1])                    #=> #<Set: {1, 2}>
Set.new([1, 'c', :s])                 #=> #<Set: {1, "c", :s}>
Set.new(1..5)                         #=> #<Set: {1, 2, 3, 4, 5}>
Set.new([1, 2, 3]) { |x| x * x }      #=> #<Set: {1, 4, 9}>

Public Instance Methods

&(enum) Show source
# File lib/set.rb, line 481
def &(enum)
  n = self.class.new
  if enum.is_a?(Set)
    if enum.size > size
      each { |o| n.add(o) if enum.include?(o) }
    else
      enum.each { |o| n.add(o) if include?(o) }
    end
  else
    do_with_enum(enum) { |o| n.add(o) if include?(o) }
  end
  n
end

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

Set[1, 3, 5] & Set[3, 2, 1]             #=> #<Set: {3, 1}>
Set['a', 'b', 'z'] & ['a', 'b', 'c']    #=> #<Set: {"a", "b"}>
Also aliased as: intersection
+(enum)
Alias for: |
-(enum) Show source
# File lib/set.rb, line 471
def -(enum)
  dup.subtract(enum)
end

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

Set[1, 3, 5] - Set[1, 5]                #=> #<Set: {3}>
Set['a', 'b', 'z'] - ['a', 'c']         #=> #<Set: {"b", "z"}>
Also aliased as: difference
<(set)
Alias for: proper_subset?
<<(o)
Alias for: add
<=(set)
Alias for: subset?
<=>(set) Show source
# File lib/set.rb, line 306
def <=>(set)
  return unless set.is_a?(Set)

  case size <=> set.size
  when -1 then -1 if proper_subset?(set)
  when +1 then +1 if proper_superset?(set)
  else 0 if self.==(set)
  end
end

Returns 0 if the set are equal, -1 / +1 if the set is a proper subset / superset of the given set, or nil if they both have unique elements.

==(other) Show source
# File lib/set.rb, line 515
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

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

Set[1, 2] == Set[2, 1]                       #=> true
Set[1, 3, 5] == Set[1, 5]                    #=> false
Set['a', 'b', 'c'] == Set['a', 'c', 'b']     #=> true
Set['a', 'b', 'c'] == ['a', 'c', 'b']        #=> false
===(o)

Returns true if the given object is a member of the set, and false otherwise.

Used in case statements:

require 'set'

case :apple
when Set[:potato, :carrot]
  "vegetable"
when Set[:apple, :banana]
  "fruit"
end
# => "fruit"

Or by itself:

Set[1, 2, 3] === 2   #=> true
Set[1, 2, 3] === 4   #=> false
Alias for: include?
>(set)
Alias for: proper_superset?
>=(set)
Alias for: superset?
^(enum) Show source
# File lib/set.rb, line 502
def ^(enum)
  n = Set.new(enum)
  each { |o| n.add(o) unless n.delete?(o) }
  n
end

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

Set[1, 2] ^ Set[2, 3]                   #=> #<Set: {3, 1}>
Set[1, 'b', 'c'] ^ ['b', 'd']           #=> #<Set: {"d", 1, "c"}>
add(o) Show source
# File lib/set.rb, line 354
def add(o)
  @hash[o] = true
  self
end

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

Set[1, 2].add(3)                    #=> #<Set: {1, 2, 3}>
Set[1, 2].add([3, 4])               #=> #<Set: {1, 2, [3, 4]}>
Set[1, 2].add(2)                    #=> #<Set: {1, 2}>
Also aliased as: <<
add?(o) Show source
# File lib/set.rb, line 366
def add?(o)
  add(o) unless include?(o)
end

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

Set[1, 2].add?(3)                    #=> #<Set: {1, 2, 3}>
Set[1, 2].add?([3, 4])               #=> #<Set: {1, 2, [3, 4]}>
Set[1, 2].add?(2)                    #=> nil
as_json(*) Show source
# File ext/json/lib/json/add/set.rb, line 17
def as_json(*)
  {
    JSON.create_id => self.class.name,
    'a'            => to_a,
  }
end

Marshal the object to JSON.

method used for JSON marshalling support.

classify() { |o| ... } Show source
# File lib/set.rb, line 584
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

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.

require 'set'
files = Set.new(Dir.glob("*.rb"))
hash = files.classify { |f| File.mtime(f).year }
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.

clear() Show source
# File lib/set.rb, line 169
def clear
  @hash.clear
  self
end

Removes all elements and returns self.

set = Set[1, 'c', :s]             #=> #<Set: {1, "c", :s}>
set.clear                         #=> #<Set: {}>
set                               #=> #<Set: {}>
collect!() { |o| ... } Show source
# File lib/set.rb, line 407
def collect!
  block_given? or return enum_for(__method__) { size }
  set = self.class.new
  each { |o| set << yield(o) }
  replace(set)
end

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

Also aliased as: map!
compare_by_identity() Show source
# File lib/set.rb, line 102
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

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

compare_by_identity?() Show source
# File lib/set.rb, line 113
def compare_by_identity?
  @hash.respond_to?(:compare_by_identity?) && @hash.compare_by_identity?
end

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

delete(o) Show source
# File lib/set.rb, line 372
def delete(o)
  @hash.delete(o)
  self
end

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

delete?(o) Show source
# File lib/set.rb, line 379
def delete?(o)
  delete(o) if include?(o)
end

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

delete_if() { |o| ... } Show source
# File lib/set.rb, line 386
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

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

difference(enum)
Alias for: -
disjoint?(set) Show source
# File lib/set.rb, line 335
def disjoint?(set)
  !intersect?(set)
end

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

Set[1, 2, 3].disjoint? Set[3, 4]   #=> false
Set[1, 2, 3].disjoint? Set[4, 5]   #=> true
divide(&func) Show source
# File lib/set.rb, line 612
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

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).

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

Returns an enumerator if no block is given.

each(&block) Show source
# File lib/set.rb, line 342
def each(&block)
  block or return enum_for(__method__) { size }
  @hash.each_key(&block)
  self
end

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

empty?() Show source
# File lib/set.rb, line 160
def empty?
  @hash.empty?
end

Returns true if the set contains no elements.

filter!(&block)

Equivalent to Set#select!

Alias for: select!
flatten() Show source
# File lib/set.rb, line 230
def flatten
  self.class.new.flatten_merge(self)
end

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

flatten!() Show source
# File lib/set.rb, line 236
def flatten!
  replace(flatten()) if any? { |e| e.is_a?(Set) }
end

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

include?(o) Show source
# File lib/set.rb, line 246
def include?(o)
  @hash[o]
end

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?

Also aliased as: member?, ===
initialize_clone(orig, **options) Show source
# File lib/set.rb, line 136
def initialize_clone(orig, **options)
  super
  @hash = orig.instance_variable_get(:@hash).clone(**options)
end

Clone internal hash.

Calls superclass method
initialize_dup(orig) Show source
# File lib/set.rb, line 129
def initialize_dup(orig)
  super
  @hash = orig.instance_variable_get(:@hash).dup
end

Dup internal hash.

Calls superclass method
inspect() Show source
# File lib/set.rb, line 652
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

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

Also aliased as: to_s
intersect?(set) Show source
# File lib/set.rb, line 321
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

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

Set[1, 2, 3].intersect? Set[4, 5]   #=> false
Set[1, 2, 3].intersect? Set[3, 4]   #=> true
intersection(enum)
Alias for: &
join(separator=nil) Show source
# File lib/set.rb, line 644
def join(separator=nil)
  to_a.join(separator)
end

Returns a string created by converting each element of the set to a string See also: Array#join

keep_if() { |o| ... } Show source
# File lib/set.rb, line 397
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

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

length()
Alias for: size
map!()
Alias for: collect!
member?(o)
Alias for: include?
merge(enum) Show source
# File lib/set.rb, line 438
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

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

proper_subset?(set) Show source
# File lib/set.rb, line 291
def proper_subset?(set)
  case
  when set.instance_of?(self.class) && @hash.respond_to?(:<)
    @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

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

Also aliased as: <
proper_superset?(set) Show source
# File lib/set.rb, line 265
def proper_superset?(set)
  case
  when set.instance_of?(self.class) && @hash.respond_to?(:>)
    @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

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

Also aliased as: >
reject!(&block) Show source
# File lib/set.rb, line 417
def reject!(&block)
  block or return enum_for(__method__) { size }
  n = size
  delete_if(&block)
  self if size != n
end

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

replace(enum) Show source
# File lib/set.rb, line 180
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

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

set = Set[1, 'c', :s]             #=> #<Set: {1, "c", :s}>
set.replace([1, 2])               #=> #<Set: {1, 2}>
set                               #=> #<Set: {1, 2}>
reset() Show source
# File lib/set.rb, line 540
def reset
  if @hash.respond_to?(:rehash)
    @hash.rehash # This should perform frozenness check.
  else
    raise FrozenError, "can't modify frozen #{self.class.name}" if frozen?
  end
  self
end

Resets the internal state after modification to existing elements and returns self.

Elements will be reindexed and deduplicated.

select!(&block) Show source
# File lib/set.rb, line 426
def select!(&block)
  block or return enum_for(__method__) { size }
  n = size
  keep_if(&block)
  self if size != n
end

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

Also aliased as: filter!
size() Show source
# File lib/set.rb, line 154
def size
  @hash.size
end

Returns the number of elements.

Also aliased as: length
subset?(set) Show source
# File lib/set.rb, line 278
def subset?(set)
  case
  when set.instance_of?(self.class) && @hash.respond_to?(:<=)
    @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

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

Also aliased as: <=
subtract(enum) Show source
# File lib/set.rb, line 450
def subtract(enum)
  do_with_enum(enum) { |o| delete(o) }
  self
end

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

superset?(set) Show source
# File lib/set.rb, line 252
def superset?(set)
  case
  when set.instance_of?(self.class) && @hash.respond_to?(:>=)
    @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

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

Also aliased as: >=
to_a() Show source
# File lib/set.rb, line 195
def to_a
  @hash.keys
end

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

Set[1, 2].to_a                    #=> [1, 2]
Set[1, 'c', :s].to_a              #=> [1, "c", :s]
to_json(*args) Show source
# File ext/json/lib/json/add/set.rb, line 25
def to_json(*args)
  as_json.to_json(*args)
end

return the JSON value

to_s()
Alias for: inspect
to_set(klass = Set, *args, &block) Show source
# File lib/set.rb, line 204
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

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.

union(enum)
Alias for: |
|(enum) Show source
# File lib/set.rb, line 460
def |(enum)
  dup.merge(enum)
end

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

Set[1, 2, 3] | Set[2, 4, 5]         #=> #<Set: {1, 2, 3, 4, 5}>
Set[1, 5, 'z'] | (1..6)             #=> #<Set: {1, 5, "z", 2, 3, 4, 6}>
Also aliased as: +, union

Ruby Core © 1993–2020 Yukihiro Matsumoto
Licensed under the Ruby License.
Ruby Standard Library © contributors
Licensed under their own licenses.