def square(pts):
     return drectangle(pts, -1, 1, -1, 1)
 def square(pts):
     return drectangle(pts, -1, 1, -1, 1)
 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))