### 26.15.8 Checking whether an object in the plane is a square

See Section 27.11.12 for checking for squares in 3D 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(1+i,-1+i,-1-i,1-i)

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K:=square(1+i,-1+i); is_square(K)

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K:=square(1+i,-1+i,C,D); is_square(K[0])

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Note that K[0] is a square since K is a list made of a square and vertices C and D.

affix(C,D)

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is_square(i,-1+i,-1-i,1-i)

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