Dear Jan, Thank you for reporting the bug, I am attaching a patch which is fixing it. Best wishes, Vladimir -- Vladimir V. Kisil http://v-v-kisil.scienceontheweb.net 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

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On Mon, 24 Aug 2026 18:37:23 +0200, Jan Rheinländer via GiNaC-list <ginac-list@ginac.de> said:

JR> Hi, JR> maybe this is a bug, maybe combining "algebraic" and JR> "no_pattern" is just not allowed. Here is the program: JR> #include <iostream> #include <ginac.h> using namespace GiNaC; JR> int main() { symbol x("x"); symbol y("y"); symbol A("A"); ex JR> w(wild()); JR> exmap repl; repl[w] = A; ex expr(x/y + w); JR> ex result = expr.subs(repl, subs_options::algebraic | JR> subs_options::no_pattern); JR> std::cout << "Result: " << result << std::endl; JR> return 0; } JR> Expected output: x/y + A JR> Actual output: A/y + A JR> Apparently mul::algebraic_subs_mul() does not honour the JR> no_pattern flag. JR> ---------------- JR> The practical reason why this problem arose is to achieve JR> algebraic substitution in sums: JR> #include <iostream> #include <ginac.h> using namespace GiNaC; JR> int main() { symbol x("x"); symbol y("y"); symbol z("z"); symbol JR> A("A"); symbol B("B"); ex w(wild()); JR> exmap repl; repl[x + y + w] = A/B + w; JR> ex expr = x + y + z; JR> // Try to substitute x+y with A/B ex result = JR> expr.subs(repl, subs_options::algebraic); JR> std::cout << "Result: " << result << std::endl; JR> return 0; } JR> Expected output: A/B + z JR> Actual output: z/B + z JR> BTW, I noticed that expairseq::match() can do algebraic matching JR> in sums. Why can it not be implemented for add::subs(), too? JR> Regards, JR> Jan