const Point<dim> &p) const = 0;
/**
- * Return the gradient of the #i#th shape
- * function at the point #p#.
- * #p# is a point on the reference element,
+ * Return the gradient of the
+ * #i#th shape function at the
+ * point #p#. #p# is a point on
+ * the reference element, and
+ * likewise the gradient is the
+ * gradient on the unit cell with
+ * respect to unit cell
+ * coordinates.
*/
virtual Tensor<1,dim> shape_grad (const unsigned int i,
const Point<dim> &p) const = 0;
/**
- * Return the tensor of second derivatives
- * of the #i#th shape function at
- * point #p# on the unit cell.
+ * Return the tensor of second
+ * derivatives of the #i#th shape
+ * function at point #p# on the
+ * unit cell. The derivatives are
+ * derivatives on the unit cell
+ * with respect to unit cell
+ * coordinates.
*/
virtual Tensor<2,dim> shape_grad_grad (const unsigned int i,
const Point<dim> &p) const = 0;