I don't see the point at all in removing the ability to represent expressions like *C1.x * C1.i + C2.y * C2.j *, it is perfectly desirable and has a well-defined behavior under differential operators (since it's an addition).
The point I brought up on github, is about the behavior of differential operators on expressions like *divergence(C2.y * C1.i) *or *gradient(x*r)* where *x* is the Cartesian coordinate, and *r* is the radius in spherical coordinates. - *gradient(x+r) = gradient(x) + gradient(r) = v_x + v_r * ===> this is straightforward - *gradient(x*r) = gradient(x*sqrt(x**2+y**2+z**2)) = gradient(r**2*sin(theta)*cos(phi))* ===> what should it return? What if there does not exist a conversion between *x* and *r* (e.g. if scalars of an other coordinate system)? In my opinion, the second case should raise an exception. It's about calculating a differential operator, not about building the expression which should always be possible. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/d1ec9288-d464-461a-8fce-75d35ad50dad%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
