14.13.12  Checking if an object in space is a square: is_square

See Section 13.16.8 for checking for squares in two-dimensional geometry.

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

• is_square takes one argument:
  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.

• Input:
  is_square([2,2,0],[-2,2,0],[-2,-2,0],[2,-2,0])
  Output:

  1

• Input:

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

  is_square(S)

  Output:

  1

• Input:
  is_square([2,2,0],[-2,2,0],[-2,-1,0],[2,-1,0])
  Output:

  0