The code is now publicly available in
Download all Maple sheets in a compressed .zip file.
Alternatively, download separate Maple sheets with calculations for...
...the elements of the fundamental octagon (vertices, midpoints...)
...rational dummy points
...the diameters of the empty disks for the dummy points (algebraic and rational)
...the proof of Theorem 1 in the paper
...the expressions of the translations around a vertex of the fundamental domain
...the algebraic degree of the Orientation predicate
...the algebraic degree of the InCircle predicate
...the algebraic degree of the SideOfOctagon predicate