    # File lib/standard/facets/random.rb, line 68
        def at_rand
          first, last = first(), last()
          if first.respond_to?(:random_delta)  # TODO: work on this!!!
            begin
              first.random_delta(last, exclude_end?)
            rescue
              to_a.at_rand
            end
          else
            to_a.at_rand
          end
          ##elsif first.respond_to?(:succ)
          ##  # optimized algorithm
          ##  if (Fixnum === first || Bignum === first) &&
          ##     (Fixnum === last  || Bignum === last)
          ##    last -= 1 if exclude_end?
          ##    return nil if last < first
          ##    return Random.number(last - first + 1) + first
          ##  end
          ##  # standard algorithm
          ##  return to_a.at_rand
          ##elsif Numeric === first && Numeric === last
          ##  return nil if last < first
          ##  return nil if exclude_end? && last == first
          ##  return (last - first) * Random.number + first
          ##else
          ##  return nil
          ##end
        end