[GiNaC-list] symbol equality

[Vladimir V. Kisil]

	Hello, Reidel,

	As far as I can remember from my projects, subclassing may need
  re-implementation some technical methods, e.g. compare_same_type(),
  is_equal(), etc. You may also need a custom subs() for your subclass.

  Best wishes,
  Vladimir
-- 
Vladimir V. Kisil                 http://www1.maths.leeds.ac.uk/~kisilv/
  Book:      Geometry of Mobius Maps       https://doi.org/10.1142/p835
  Soft:      Geometry of cycles         http://moebinv.sourceforge.net/
  Jupyter notebooks:        https://github.com/vvkisil?tab=repositories
>>>>> On Thu, 9 Feb 2023 06:08:13 +0100, Marko Riedel <riedelmo at mathematik.uni-stuttgart.de> said:

    MR> Greetings to all.

    MR> I have been subclassing "symbol" for my project, where I need to
    MR> attach an integer value to a symbol. I am not sure this is the
    MR> best way to go about it but I would like to try. Everything
    MR> works so far but now I have moved on to substituting variables
    MR> in polynomials. Here is my sample program.

    MR> #include <iostream> #include <ginac/ginac.h>

    MR> #include "cindsymbol.h" #include "util.h"

    MR> using namespace std; using namespace GiNaC;


    MR> int main() { cindsymbol R = cindsymbol("R",0), G =
    MR> cindsymbol("G",0), B = cindsymbol("B",0), X = cindsymbol("X",0);

    MR>   ex pl = X + pow(X, 3) + R + G + B;

    MR>   cout << R << G << B << " " << pl << endl; cout << pl.subs({X},
    MR> {pow(X,4)}) << endl;

    MR>   return 0; }

    MR> The output of this program is as follows (the print functions
    MR> from the subclass are being invoked correctly and do not print
    MR> the zero value):

    MR> RGB X+R+G+B+X^3 4*X^4+X^12

    MR> Obviously GiNaC thinks that R=X, B=X and G=X. How do I get this
    MR> comparison to work? Do I need to override some function in my
    MR> subclass?  The function "cindsymbol" goes as follows (copied
    MR> from the tutorial):

    MR> static map<string, cindsymbol> directory;

    MR> cindsymbol cindsym(const std::string & initname, unsigned cl) {
    MR> std::string key = initname + "|" + std::to_string(cl);
    MR> map<std::string, cindsymbol>::iterator it = directory.find(key);

    MR>   if (it != directory.end()) return it->second; else{
    MR> std::pair<std::string, cindsymbol> ent = make_pair(key,
    MR> cindsymbol(initname, cl)); return
    MR> directory.insert(ent).first->second; } }

    MR> Can you advise me here? Thanks!

    MR> Best regards,

    MR> Marko Riedel





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