class Set - RDoc Documentation

# 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 #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[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 78
    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.

    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 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

### 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 472
    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.

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

    # File lib/set.rb, line 462
    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?.

    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 498
    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 485
    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 348
    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 360
    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.

    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 567
    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 176
    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 401
    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 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?() click to toggle source

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

    # File lib/set.rb, line 118
    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 366
    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 373
    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 380
    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 329
    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 595
    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 336
    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 167
    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 237
    def flatten
      self.class.new.flatten_merge(self)
    end

flatten!() click to toggle source

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

    # File lib/set.rb, line 243
    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 253
    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 140
    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 134
    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 629
    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 315
    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 391
    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 429
    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 298
    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 272
    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 #delete_if, but returns nil if no changes were made. Returns an enumerator if no block is given.

    # File lib/set.rb, line 411
    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 187
    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 523
    def reset
      if @hash.respond_to?(:rehash)
        @hash.rehash # This should perform frozenness check.
      else
        raise "can't modify frozen #{self.class.name}" if frozen?
      end
      self
    end

select!(&block) click to toggle source

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

    # File lib/set.rb, line 420
    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 161
    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 285
    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 441
    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 259
    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 202
    def to_a
      @hash.keys
    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 211
    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 451
    def |(enum)
      dup.merge(enum)
    end

Also aliased as: +, union