[GiNaC-list] How to differentiate from a Tensor?

[Vladimir V. Kisil]

>>>>> On Fri, 14 Jul 2017 13:29:37 +0430, esarcush esarcush <esarcush at gmail.com> said:

    EE> E needs to depend on x. So, symbol A("A"), x("x"); symbol
    EE> i_sym("i"), j_sym("j"); idx i(i_sym, 3), j(j_sym, 3); ex e =
    EE> indexed(A, i, j); ex de_dx = e.diff(x); cout << de_dx << "\n";

    EE> returns 0. Thus, what is the way to depend "e" on "x" like
    EE> undefined functions?

    If a dependence of A on x is not defined, try to use the step
  function (as one without defined derivative): 

    ex e = indexed(step(x), i, j);

    This keeps track on derivatives.

    To maintainer: I have run into similar situation working with
  differential operators. Shall we add "generic" functions to GiNaC with
  1, 2, 3, 4 variables?  
-- 
Vladimir V. Kisil                 http://www.maths.leeds.ac.uk/~kisilv/
  Book:     Geometry of Mobius Transformations     http://goo.gl/EaG2Vu
  Software: Geometry of cycles          http://moebinv.sourceforge.net/

    EE> All the bests,

    EE> On 7/14/17, Vladimir V. Kisil <kisilv at maths.leeds.ac.uk> wrote:
    >>>>>>> On Fri, 14 Jul 2017 12:15:49 +0430, esarcush esarcush
    >>>>>>> <esarcush at gmail.com> said:
    >> 
    EE> Dear all, What is right way to have something like \(
    EE> \frac{\partial A^{i}_{jk}}{\partial x} \)? Indeed, I defined a
    EE> tensor "A~i.j.k" and want to differentiate from it with respect
    EE> to "x" e.g.
    >> 
    >> For a GiNaC object E its derivative with respect to x is obtained
    >> by E.diff(x)
    >> --
    >> Vladimir V. Kisil http://www.maths.leeds.ac.uk/~kisilv/ Book:
    >> Geometry of Mobius Transformations http://goo.gl/EaG2Vu Software:
    >> Geometry of cycles http://moebinv.sourceforge.net/
    >>