code: function in_half_open_range(key, low, high) {
      //return (low < high && key > low && key <= high) ||
      //    (low > high && (key > low || key <= high)) ||
      //    (low == high);
      return (less_than(low, high) && less_than(low, key) && less_than_or_equal(key, high)) ||
          (less_than(high, low) && (less_than(low, key) || less_than_or_equal(key, high))) ||
          (equal_to(low, high));
  }
docs: Is key in (low, high]