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Class: Set

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Subclasses:
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, ::Enumerable
Inherits: Object
Defined in: lib/set.rb

Overview

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 (y vs. 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 <knu@iDaemons.org> (current maintainer)

Constant Summary

Class Method Summary

Instance Attribute Summary

Instance Method Summary

::Enumerable - Included

#to_set

Makes a set from the enumerable object with given arguments.

Constructor Details

.new(enum = nil, &block) ⇒ Set

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}>
[ GitHub ]

  
# File 'lib/set.rb', line 93

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

Class Method Details

.[](*ary)

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}>
[ GitHub ]

  
# File 'lib/set.rb', line 78

def self.[](*ary)
  new(ary)
end

Instance Attribute Details

#compare_by_identity (readonly)

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

[ GitHub ]

  
# File 'lib/set.rb', line 107

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?Boolean (readonly)

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

[ GitHub ]

  
# File 'lib/set.rb', line 118

def compare_by_identity?
  @hash.respond_to?(:compare_by_identity?) && @hash.compare_by_identity?
end

#empty?Boolean (readonly)

Returns true if the set contains no elements.

[ GitHub ]

  
# File 'lib/set.rb', line 157

def empty?
  @hash.empty?
end

Instance Method Details

#&(enum) Also known as: #intersection

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"}>
[ GitHub ]

  
# File 'lib/set.rb', line 465

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

#+(enum)

Alias for #|.

[ GitHub ]

  
# File 'lib/set.rb', line 447

alias + |

#-(enum) Also known as: #difference

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"}>
[ GitHub ]

  
# File 'lib/set.rb', line 455

def -(enum)
  dup.subtract(enum)
end

#<(set)

Alias for #proper_subset?.

[ GitHub ]

  
# File 'lib/set.rb', line 298

alias < proper_subset?

#<<(o)

Alias for #add.

[ GitHub ]

  
# File 'lib/set.rb', line 342

alias << add

#<=(set)

Alias for #subset?.

[ GitHub ]

  
# File 'lib/set.rb', line 285

alias <= subset?

#==(other)

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
[ GitHub ]

  
# File 'lib/set.rb', line 499

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

#===(o)

Alias for #include?.

[ GitHub ]

  
# File 'lib/set.rb', line 553

alias === include?

#>(set)

Alias for #proper_superset?.

[ GitHub ]

  
# File 'lib/set.rb', line 272

alias > proper_superset?

#>=(set)

Alias for #superset?.

[ GitHub ]

  
# File 'lib/set.rb', line 259

alias >= 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)).

Set[1, 2] ^ Set[2, 3]                   #=> #<Set: {3, 1}>
Set[1, 'b', 'c'] ^ ['b', 'd']           #=> #<Set: {"d", 1, "c"}>
[ GitHub ]

  
# File 'lib/set.rb', line 486

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

#add(o) Also known as: #<<

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}>
[ GitHub ]

  
# File 'lib/set.rb', line 338

def add(o)
  @hash[o] = true
  self
end

#add?(o) ⇒ Boolean

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
[ GitHub ]

  
# File 'lib/set.rb', line 350

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

#classify

Classifies the set by the return value of the given block and returns a hash of => 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.

[ GitHub ]

  
# File 'lib/set.rb', line 568

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

Removes all elements and returns self.

set = Set[1, 'c', :s]             #=> #<Set: {1, "c", :s}>
set.clear                         #=> #<Set: {}>
set                               #=> #<Set: {}>
[ GitHub ]

  
# File 'lib/set.rb', line 166

def clear
  @hash.clear
  self
end

#collect! Also known as: #map!

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

[ GitHub ]

  
# File 'lib/set.rb', line 391

def collect!
  block_given? or return enum_for(__method__) { size }
  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.

[ GitHub ]

  
# File 'lib/set.rb', line 356

def delete(o)
  @hash.delete(o)
  self
end

#delete?(o) ⇒ Boolean

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

[ GitHub ]

  
# File 'lib/set.rb', line 363

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

#delete_if

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

[ GitHub ]

  
# File 'lib/set.rb', line 370

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 #-.

[ GitHub ]

  
# File 'lib/set.rb', line 458

alias difference -

#disjoint?(set) ⇒ Boolean

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
[ GitHub ]

  
# File 'lib/set.rb', line 319

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).

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.

[ GitHub ]

  
# File 'lib/set.rb', line 596

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

#do_with_enum(enum, &block) (private)

This method is for internal use only.
[ GitHub ]

  
# File 'lib/set.rb', line 122

def do_with_enum(enum, &block) # :nodoc:
  if enum.respond_to?(:each_entry)
    enum.each_entry(&block) if block
  elsif enum.respond_to?(:each)
    enum.each(&block) if block
  else
    raise ArgumentError, "value must be enumerable"
  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.

[ GitHub ]

  
# File 'lib/set.rb', line 326

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

#eql?(o) ⇒ Boolean

This method is for internal use only.
[ GitHub ]

  
# File 'lib/set.rb', line 515

def eql?(o)   # :nodoc:
  return false unless o.is_a?(Set)
  @hash.eql?(o.instance_variable_get(:@hash))
end

#filter!(&block)

Alias for #select!.

[ GitHub ]

  
# File 'lib/set.rb', line 418

alias filter! select!

#flatten

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

[ GitHub ]

  
# File 'lib/set.rb', line 227

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.

[ GitHub ]

  
# File 'lib/set.rb', line 233

def flatten!
  replace(flatten()) if any? { |e| e.is_a?(Set) }
end

#flatten_merge(set, seen = Set.new) (protected)

This method is for internal use only.
[ GitHub ]

  
# File 'lib/set.rb', line 206

def flatten_merge(set, seen = Set.new) # :nodoc:
  set.each { |e|
    if e.is_a?(Set)
      if seen.include?(e_id = e.object_id)
        raise ArgumentError, "tried to flatten recursive Set"
      end

      seen.add(e_id)
      flatten_merge(e, seen)
      seen.delete(e_id)
    else
      add(e)
    end
  }

  self
end

#freeze

This method is for internal use only.
[ GitHub ]

  
# File 'lib/set.rb', line 145

def freeze    # :nodoc:
  @hash.freeze
  super
end

#hash

This method is for internal use only.
[ GitHub ]

  
# File 'lib/set.rb', line 511

def hash      # :nodoc:
  @hash.hash
end

#include?(o) ⇒ Boolean Also known as: #member?, #===

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?

[ GitHub ]

  
# File 'lib/set.rb', line 243

def include?(o)
  @hash[o]
end

#initialize_clone(orig, freeze: nil)

Clone internal hash.

[ GitHub ]

  
# File 'lib/set.rb', line 140

def initialize_clone(orig, freeze: nil)
  super
  @hash = orig.instance_variable_get(:@hash).clone(freeze: freeze)
end

#initialize_dup(orig)

Dup internal hash.

[ GitHub ]

  
# File 'lib/set.rb', line 134

def initialize_dup(orig)
  super
  @hash = orig.instance_variable_get(:@hash).dup
end

#inspect Also known as: #to_s

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

[ GitHub ]

  
# File 'lib/set.rb', line 630

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) ⇒ Boolean

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
[ GitHub ]

  
# File 'lib/set.rb', line 305

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 #&.

[ GitHub ]

  
# File 'lib/set.rb', line 478

alias intersection &

#keep_if

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

[ GitHub ]

  
# File 'lib/set.rb', line 381

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.

[ GitHub ]

  
# File 'lib/set.rb', line 154

alias length size

#map!

Alias for #collect!.

[ GitHub ]

  
# File 'lib/set.rb', line 397

alias map! collect!

#member?(o)

Alias for #include?.

[ GitHub ]

  
# File 'lib/set.rb', line 246

alias member? include?

#merge(enum)

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

[ GitHub ]

  
# File 'lib/set.rb', line 422

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

#pretty_print(pp)

This method is for internal use only.
[ GitHub ]

  
# File 'lib/set.rb', line 647

def pretty_print(pp)  # :nodoc:
  pp.text sprintf('#<%s: {', self.class.name)
  pp.nest(1) {
    pp.seplist(self) { |o|
      pp.pp o
    }
  }
  pp.text "}>"
end

#pretty_print_cycle(pp)

This method is for internal use only.
[ GitHub ]

  
# File 'lib/set.rb', line 657

def pretty_print_cycle(pp)    # :nodoc:
  pp.text sprintf('#<%s: {%s}>', self.class.name, empty? ? '' : '...')
end

#proper_subset?(set) ⇒ Boolean Also known as: #<

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

[ GitHub ]

  
# File 'lib/set.rb', line 288

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

#proper_superset?(set) ⇒ Boolean Also known as: #>

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

[ GitHub ]

  
# File 'lib/set.rb', line 262

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

#reject!(&block)

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

[ GitHub ]

  
# File 'lib/set.rb', line 401

def reject!(&block)
  block or return enum_for(__method__) { size }
  n = size
  delete_if(&block)
  self if size != n
end

#replace(enum)

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}>
[ GitHub ]

  
# File 'lib/set.rb', line 177

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

#reset

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

Elements will be reindexed and deduplicated.

[ GitHub ]

  
# File 'lib/set.rb', line 524

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

#select!(&block) Also known as: #filter!

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

[ GitHub ]

  
# File 'lib/set.rb', line 410

def select!(&block)
  block or return enum_for(__method__) { size }
  n = size
  keep_if(&block)
  self if size != n
end

#size Also known as: #length

Returns the number of elements.

[ GitHub ]

  
# File 'lib/set.rb', line 151

def size
  @hash.size
end

#subset?(set) ⇒ Boolean Also known as: #<=

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

[ GitHub ]

  
# File 'lib/set.rb', line 275

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

#subtract(enum)

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

[ GitHub ]

  
# File 'lib/set.rb', line 434

def subtract(enum)
  do_with_enum(enum) { |o| delete(o) }
  self
end

#superset?(set) ⇒ Boolean Also known as: #>=

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

[ GitHub ]

  
# File 'lib/set.rb', line 249

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

#to_a

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]
[ GitHub ]

  
# File 'lib/set.rb', line 192

def to_a
  @hash.keys
end

#to_s

Alias for #inspect.

[ GitHub ]

  
# File 'lib/set.rb', line 645

alias to_s inspect

#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.

[ GitHub ]

  
# File 'lib/set.rb', line 201

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 #|.

[ GitHub ]

  
# File 'lib/set.rb', line 448

alias union |

#|(enum) Also known as: #+, #union

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}>
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# File 'lib/set.rb', line 444

def |(enum)
  dup.merge(enum)
end