gistfile1.rb

module Enumerable
  module Ordonned
    def [](arg)
      case arg
      when Numeric
        detect.with_index { |_, index| index == arg }
      when Range
        result = []
        each.with_index do |object, index|
          result << object if arg.include?(index)
        end
        result
      else
        raise ArgumentError, "Range or Numeric expected"
      end
    end
  end
end