Correct functional for internal dofs TNT quadrilateral

python/demo/demo_tnt-elements.py

@@ -221,9 +221,14 @@ def create_tnt_quad(degree):
         pts, wts = basix.make_quadrature(basix.CellType.quadrilateral, 2 * degree)
         u = pts[:, 0]
         v = pts[:, 1]
-        poly = basix.polynomials.tabulate_polynomial_set(basix.CellType.quadrilateral, basix.PolynomialType.legendre, degree-2, 2, pts)
-        # this assumes the conventional [0 to 1][0 to 1] domain of the reference element, and takes the Laplacian of (1-u)*u*(1-v)*v*poly, cf https://github.com/mscroggs/symfem/blob/main/symfem/elements/tnt.py
-        poly = (poly[5]+poly[3])*(u-1)*u*(v-1)*v+2*(poly[2]*(u-1)*u*(2*v-1)+poly[1]*(v-1)*v*(2*u-1)+poly[0]*((u-1)*u+(v-1)*v))
+        pol0 = basix.polynomials.tabulate_polynomial_set(
+            basix.CellType.quadrilateral, basix.PolynomialType.legendre, degree-2, 2, pts
+        )
+        # this assumes the conventional [0 to 1][0 to 1] domain of the reference element, 
+        # and takes the Laplacian of (1-u)*u*(1-v)*v*poly, 
+        # cf https://github.com/mscroggs/symfem/blob/main/symfem/elements/tnt.py
+        poly = (pol0[5]+pol0[3])*(u-1)*u*(v-1)*v+ \
+                2*(pol0[2]*(u-1)*u*(2*v-1)+pol0[1]*(v-1)*v*(2*u-1)+pol0[0]*((u-1)*u+(v-1)*v))
         face_ndofs = poly.shape[0]
         x[2].append(pts)
         mat = np.zeros((face_ndofs, 1, len(pts), 1))