def ell(pts):
     return ddiff(drectangle(pts, -1, 1, -1, 1), drectangle(pts, -2, 0, -2, 0))
 def ell(pts):
     return ddiff(drectangle(pts, -1, 1, -1, 1),
                  drectangle(pts, -2, 0, -2, 0))
 def circle_with_a_hole(pts):
     return ddiff(dcircle(pts, 0, 0, 1), dcircle(pts, 0.5, 0, 0.4))
 def circle_with_a_hole(pts):
     return ddiff(dcircle(pts, 0, 0, 1), dcircle(pts, 0.5, 0, 0.4))