Better enum

enum.rb

# Ruby Enum
# ---------
# enum = Enum.new("Apple", "Orange", "Prun")
# enum[:apple] = 0
# enum[0] = :apple

require 'set'

class Enum < Set

  class Member

    include Comparable

    attr_reader :symbol
    attr_reader :index
    attr_reader :name

    def initialize(value, index = 0, name = nil)
      @symbol = value.to_sym
      @index = index.to_i
      @name = name ||= value
    end

    def <=>(other_member)
      self.symbol <=> other_member.symbol
    end
  end

  def initialize(*members)
    super()
    populate(members)
  end
    
  def to_a
    super.sort_by(&:index)
  end

  def each
    block_given? or return enum_for(__method__)
    self.to_a.each { |o| yield(o) }
    self
  end

  def [](index_or_symbol)
    if index_or_symbol.is_a?(Symbol)
      return self.select {|member| member.symbol == index_or_symbol }.first
    elsif index_or_symbol.is_a?(Integer)
      return self.select {|member| member.index == index_or_symbol }.first
    end
  end

  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.collect(&:name).inspect[1..-2])
    ensure
      ids.pop
    end
  end

  protected
  
  def populate(members)
    members.each_with_index do |member, index|
      self.add(Enum::Member.new(member, index)) unless self.to_a.collect(&:name).include?(member)
    end
  end
end

I'd like

Enum.new(:does_not_exist => -1, red, blue, gray)
doest_not_exist == -1
red == 0
blue == 1
gray == 2