On Fri, 14 Jul 2017 13:29:37 +0430, esarcush esarcush <esarcush@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@maths.leeds.ac.uk> wrote: >>>>>>> On Fri, 14 Jul 2017 12:15:49 +0430, esarcush esarcush >>>>>>> <esarcush@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/ >>