# HP Prime for All

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is_rectangle(Point1, Point2, Point3, Point4)

Tests whether or not a set of four points are vertices of a rectangle. Returns 0 if they are not, 1 if they are, and 2 if they are vertices of a square.

is_rectangle(point(0,0), point(4,2), point(2,6), point(-2,4)) returns 2.
With a set of only three points as argument, tests whether or not they are vertices of a right triangle. Returns 0 if they are not. If they are, returns the number order of the common point of the two perpendicular sides (1, 2, or 3).
is_rectangle(point(0,0), point(4,2), point(2,6)) returns 2.