# File lib/sass/script/functions.rb, line 2196
    def unique_id
      generator = Sass::Script::Functions.random_number_generator
      Thread.current[:sass_last_unique_id] ||= generator.rand(36**8)
      # avoid the temptation of trying to guess the next unique value.
      value = (Thread.current[:sass_last_unique_id] += (generator.rand(10) + 1))
      # the u makes this a legal identifier if it would otherwise start with a number.
      identifier("u" + value.to_s(36).rjust(8, '0'))
    end