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.

The equality of each couple of elements is determined according to Object#eql? and Object#hash, since Set uses Hash as storage.

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.

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: {6, 1, 2, "foo"}>
s1.subset? s2                         # -> false
s2.subset? s1                         # -> true

Contact

- Akinori MUSHA <knu@iDaemons.org> (current maintainer)
Methods
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Included Modules
Constants
InspectKey = :__inspect_key__
 
Class Public methods
[](*ary)

Creates a new set containing the given objects.

# File lib/set.rb, line 58
def self.[](*ary)
  new(ary)
end
new(enum = nil)

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 67
def initialize(enum = nil, &block) # :yields: o
  @hash ||= Hash.new

  enum.nil? and return

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

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

Also aliased as: intersection
# File lib/set.rb, line 340
def &(enum)
  n = self.class.new
  do_with_enum(enum) { |o| n.add(o) if include?(o) }
  n
end
+(enum)
-(enum)

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

Also aliased as: difference
# File lib/set.rb, line 333
def -(enum)
  dup.subtract(enum)
end
<<(o)
==(other)

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 358
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
^(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)).

# File lib/set.rb, line 350
def ^(enum)
  n = Set.new(enum)
  each { |o| if n.include?(o) then n.delete(o) else n.add(o) end }
  n
end
add(o)

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

Also aliased as: <<
# File lib/set.rb, line 228
def add(o)
  @hash[o] = true
  self
end
add?(o)

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 236
def add?(o)
  if include?(o)
    nil
  else
    add(o)
  end
end
classify()

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"}>}
# File lib/set.rb, line 392
def classify # :yields: o
  block_given? or return enum_for(__method__)

  h = {}

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

  h
end
clear()

Removes all elements and returns self.

# File lib/set.rb, line 125
def clear
  @hash.clear
  self
end
collect!()

Replaces the elements with ones returned by collect().

Also aliased as: map!
# File lib/set.rb, line 278
def collect!
  block_given? or return enum_for(__method__)
  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 subtractto delete many items at once.

# File lib/set.rb, line 246
def delete(o)
  @hash.delete(o)
  self
end
delete?(o)

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 253
def delete?(o)
  if include?(o)
    delete(o)
  else
    nil
  end
end
delete_if()

Deletes every element of the set for which block evaluates to true, and returns self.

# File lib/set.rb, line 263
def delete_if
  block_given? or return enum_for(__method__)
  to_a.each { |o| @hash.delete(o) if yield(o) }
  self
end
difference(enum)
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).

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}>}>
# File lib/set.rb, line 421
def divide(&func)
  func or return enum_for(__method__)

  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()

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 220
def each
  block_given? or return enum_for(__method__)
  @hash.each_key { |o| yield(o) }
  self
end
empty?()

Returns true if the set contains no elements.

# File lib/set.rb, line 120
def empty?
  @hash.empty?
end
flatten()

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

# File lib/set.rb, line 169
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.

# File lib/set.rb, line 175
def flatten!
  if detect { |e| e.is_a?(Set) }
    replace(flatten())
  else
    nil
  end
end
include?(o)

Returns true if the set contains the given object.

Also aliased as: member?
# File lib/set.rb, line 184
def include?(o)
  @hash.include?(o)
end
initialize_copy(orig)

Copy internal hash.

# File lib/set.rb, line 91
def initialize_copy(orig)
  @hash = orig.instance_eval{@hash}.dup
end
inspect()

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

# File lib/set.rb, line 455
def inspect
  ids = (Thread.current[InspectKey] ||= [])

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

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

Deletes every element of the set for which block evaluates to false, and returns self.

# File lib/set.rb, line 271
def keep_if
  block_given? or return enum_for(__method__)
  to_a.each { |o| @hash.delete(o) unless yield(o) }
  self
end
length()
map!()
member?(o)
merge(enum)

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

# File lib/set.rb, line 306
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)

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

# File lib/set.rb, line 211
def proper_subset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if set.size <= size
  all? { |o| set.include?(o) }
end
proper_superset?(set)

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

# File lib/set.rb, line 197
def proper_superset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if size <= set.size
  set.all? { |o| include?(o) }
end
reject!()

Equivalent to #delete_if, but returns nil if no changes were made.

# File lib/set.rb, line 288
def reject!
  block_given? or return enum_for(__method__)
  n = size
  delete_if { |o| yield(o) }
  size == n ? nil : self
end
replace(enum)

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

# File lib/set.rb, line 132
def replace(enum)
  if enum.instance_of?(self.class)
    @hash.replace(enum.instance_variable_get(:@hash))
  else
    clear
    merge(enum)
  end

  self
end
select!()

Equivalent to #keep_if, but returns nil if no changes were made.

# File lib/set.rb, line 297
def select!
  block_given? or return enum_for(__method__)
  n = size
  keep_if { |o| yield(o) }
  size == n ? nil : self
end
size()

Returns the number of elements.

Also aliased as: length
# File lib/set.rb, line 114
def size
  @hash.size
end
subset?(set)

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

# File lib/set.rb, line 204
def subset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if set.size < size
  all? { |o| set.include?(o) }
end
subtract(enum)

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

# File lib/set.rb, line 318
def subtract(enum)
  do_with_enum(enum) { |o| delete(o) }
  self
end
superset?(set)

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

# File lib/set.rb, line 190
def superset?(set)
  set.is_a?(Set) or raise ArgumentError, "value must be a set"
  return false if size < set.size
  set.all? { |o| include?(o) }
end
to_a()

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

# File lib/set.rb, line 144
def to_a
  @hash.keys
end
union(enum)
|(enum)

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

Also aliased as: +, union
# File lib/set.rb, line 325
def |(enum)
  dup.merge(enum)
end