code: public Direction direction() {
          double range = this.end - this.start;
          if (!Op.isFinite(range) || Op.isEq(range, 0.0)) {
              return Direction.Zero;
          }
          if (Op.isGt(range, 0.0)) {
              return Direction.Positive;
          }
          return Direction.Negative;
      }
docs: Returns the direction of the ramp
  
  @return the direction of the ramp