On Mon, 17 Jul 2017 19:56:44 +0200, "Richard B. Kreckel" <kreckel@in.terlu.de> said:
RK> On 07/14/2017 11:18 AM, Vladimir V. Kisil wrote: >> 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? RK> Isn't that there already? RK> <https://www.ginac.de/ginac.git/?p=ginac.git;a=blob;f=ginac/function.cppy;h=a7e3649c7c195e93ae5886c66202ad9fdc1bbd6c;hb=HEAD#l744> It seems, not. Assume, I want to calculate the Laplacian in polar coordinates. Then the expression f(sqrt(x*x+y*y),atan2(y,x)).diff(x,2)+f(sqrt(x*x+y*y),atan2(y,x)).diff(y,2) does it, provided that f is a function of two variables without defined derivatives. For one variable the step function is (the only?) example of such function. So my proposition is to add to GiNaC a family of "generic functions" of 1-4 variables without any specific properties. Advises "derive your own class" or "define your own function" is a certain barrier for a set of GiNaC users, I think (from my own experience). Best wishes, Vladimir -- 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/