class Set - RDoc Documentation

# class Set

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¶ ↑

- Akinori MUSHA <knu@iDaemons.org> (current maintainer)

### Public Class Methods

[](*ary) click to toggle source

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}>

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

json_create(object) click to toggle source

Import a `JSON` Marshalled object.

method used for `JSON` marshalling support.

    # File ext/json/lib/json/add/set.rb, line 10
    def self.json_create(object)
      new object['a']
    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.

    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}>

    # 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

### Public Instance Methods

&(enum) click to toggle source

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"}>

    # 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

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.

    Set[1, 3, 5] - Set[1, 5]                #=> #<Set: {3}>
    Set['a', 'b', 'z'] - ['a', 'c']         #=> #<Set: {"b", "z"}>

    # File lib/set.rb, line 471
    def -(enum)
      dup.subtract(enum)
    end

Also aliased as: difference
<(set)
Alias for: proper_subset?
<<(o)
Alias for: add
<=(set)
Alias for: subset?
<=>(set) click to toggle source

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.

    # 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

==(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?`.

    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

    # 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

===(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) 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))`.

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

    # File lib/set.rb, line 502
    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.

    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}>

    # File lib/set.rb, line 354
    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.

    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

    # File lib/set.rb, line 366
    def add?(o)
      add(o) unless include?(o)
    end

as_json(*) click to toggle source

`Marshal` the object to `JSON`.

method used for `JSON` marshalling support.

    # File ext/json/lib/json/add/set.rb, line 17
    def as_json(*)
      {
        JSON.create_id => self.class.name,
        'a'            => to_a,
      }
    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.

    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.

    # 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

clear() click to toggle source

Removes all elements and returns self.

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

    # File lib/set.rb, line 169
    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 407
    def collect!
      block_given? or return enum_for(__method__) { size }
      set = self.class.new
      each { |o| set << yield(o) }
      replace(set)
    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 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

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 113
    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 372
    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 379
    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 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

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?`.

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

    # File lib/set.rb, line 335
    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).

    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.

    # 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

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 342
    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 160
    def empty?
      @hash.empty?
    end

filter!(&block)

Equivalent to `Set#select!`

Alias for: select!
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 230
    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 236
    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 246
    def include?(o)
      @hash[o]
    end

Also aliased as: member?, ===
initialize_clone(orig, **options) click to toggle source

Clone internal hash.

Calls superclass method

    # File lib/set.rb, line 136
    def initialize_clone(orig, **options)
      super
      @hash = orig.instance_variable_get(:@hash).clone(**options)
    end

initialize_dup(orig) click to toggle source

Dup internal hash.

Calls superclass method

    # File lib/set.rb, line 129
    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 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

Also aliased as: to_s
intersect?(set) click to toggle source

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

    # 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

intersection(enum)
Alias for: &
join(separator=nil) click to toggle source

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

    # File lib/set.rb, line 644
    def join(separator=nil)
      to_a.join(separator)
    end

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 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

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 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

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 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

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 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

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 417
    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.

    set = Set[1, 'c', :s]             #=> #<Set: {1, "c", :s}>
    set.replace([1, 2])               #=> #<Set: {1, 2}>
    set                               #=> #<Set: {1, 2}>

    # 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

reset() click to toggle source

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

Elements will be reindexed and deduplicated.

    # 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

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 426
    def select!(&block)
      block or return enum_for(__method__) { size }
      n = size
      keep_if(&block)
      self if size != n
    end

Also aliased as: filter!
size() click to toggle source

Returns the number of elements.

    # File lib/set.rb, line 154
    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 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

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 450
    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 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

Also aliased as: >=
to_a() click to toggle source

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]

    # File lib/set.rb, line 195
    def to_a
      @hash.keys
    end

to_json(*args) click to toggle source

return the `JSON` value

    # File ext/json/lib/json/add/set.rb, line 25
    def to_json(*args)
      as_json.to_json(*args)
    end

to_s()
Alias for: inspect
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 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

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.

    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}>

    # File lib/set.rb, line 460
    def |(enum)
      dup.merge(enum)
    end

Also aliased as: +, union