double epsilon
Note: List.sort(java.util.Comparator<? super E>) throws IllegalArgumentException when supplied a
PointDComparator whose PointDComparator.epsilon overlaps the coordinates of distinct
PointD instances in both dimensions, resulting in the classification of
PointD instances as equal when their PointD.equals(org.kynosarges.tektosyne.geometry.PointD, org.kynosarges.tektosyne.geometry.PointD, double) and PointD.hashCode()
results signal inequality. ("Comparison method violates its general contract.")