docs: function() {
        var numAxes = this._numAxes, axesOrder = this._axesOrder, i, ordinal = 0, a, arg, j, tupleCount;
        //for each axis, in descending order
        for (a = 0, i = numAxes - 1; i >= 0; i--, a++) {
          arg = arguments[a];
          tupleCount = 1;
          //for all preceding axes, in descending order
          for (j = i-1; j >= 0; j--) {
            tupleCount *= axesOrder[j].tupleCount();
          }
          ordinal += arg * tupleCount;
        }
        return ordinal;
      }