Function quadrant

quadrant(p1, p2): Quadrant
Calculates the quadrant in which the angle between the two points lies.
Parameters
- p1: PointXY
  First point in the line
- p2: PointXY
  Second point in the line
Returns Quadrant
The quadrant - 1 for upper right, 2 for lower right, 3 for lower left, 4 for upper left.

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