Dear Bernardo,
On Thu, 10 Feb 2011 16:11:41 -0200, Bernardo Rocha <bernardosk@gmail.com> said: BMR> Well, defining the function as a GiNaC expression is part of my BMR> doubt,
You need to define an indexed object, see respective section (4.14.1) in the manual. In the example symbol i_sym("i"), j_sym("j"); idx i(i_sym, 3), j(j_sym, 3); symbol A("A"); ex E=indexed(A, i, j); you need to replace A by a suitable GiNaC expression, which will encode properties of your tensor. In some cases you may need to define your own class for it if you wish a fine control on its behaviour. Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv@maths.leeds.ac.uk -- www: http://www.maths.leeds.ac.uk/~kisilv/