Set.rb illuminated

aritmethics.rb

  # given enumerable object.
  def |(enum)
    dup.merge(enum)
  end
  alias + |             ##
  alias union |         ##

  # Returns a new set built by duplicating the set, removing every
  # element that appears in the given enumerable object.
  def -(enum)
    dup.subtract(enum)
  end
  alias difference -    ##

  # Returns a new set containing elements common to the set and the
  # given enumerable object.
  def &(enum)
    n = self.class.new
    do_with_enum(enum) { |o| n.add(o) if include?(o) }
    n
  end
  alias intersection &  ##

  # Returns a new set containing elements exclusive between the set
  # and the given enumerable object.  (set ^ enum) is equivalent to
  # ((set | enum) - (set & enum)).
  def ^(enum)
    n = Set.new(enum)
    each { |o| if n.include?(o) then n.delete(o) else n.add(o) end }
    n
  end