### 27.11.12 Checking whether an object in space is a square

See Section 26.15.8 for checking for squares in 2D geometry.

The is_square command determines whether or not a geometric object is a square.

- is_square takes G, a geometric object or a sequence of four points assumed to be the vertices of a quadrilateral.
- is_square(G) returns 1 if the object is a square and returns 0 otherwise.

#### Examples

is_square([2,2,0],[-2,2,0],[-2,-2,0],[2,-2,0])

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S:=square([0,0,0],[2,0,0],[0,0,1]); is_square(S)

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is_square([2,2,0],[-2,2,0],[-2,-1,0],[2,-1,0])

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