require 'singleton'

class LongOperation
  include Singleton

  def initialize
    puts "Calculating"
    @base = 2 ** 32
  end

  def value
    @base
  end
end


class Base

  def initialize
    @value = LongOperation.instance.value
  end

  def value
    @value
  end

end

puts Base.new.value
puts Base.new.value
puts Base.new.value

## Old Approach


class Base
  include Singleton

  def initialize
    unless @base
      @base = "DABASE"
      puts "-----------------------------"
      puts "This is Base's initializer"
      puts "-----------------------------"
    end
  end
end

class Derived < Base
  def self.do_sth
    puts "do sth ..."
  end
end

if __FILE__ == $0
  3.times do
    Derived.do_sth
  end
end