# File lib/sass/script/functions.rb, line 1853
    def set_nth(list, n, value)
      assert_type n, :Number, :n
      Sass::Script::Value::List.assert_valid_index(list, n)
      index = n.to_i > 0 ? n.to_i - 1 : n.to_i
      new_list = list.to_a.dup
      new_list[index] = value
      Sass::Script::Value::List.new(new_list, list.separator)
    end