Hi, thanks for the patch! It has been applied. Regards, Jens On Tue, Mar 22, 2005 at 03:33:08PM +0300, Sheplyakov Alexei wrote:

Hello!

This simple program fails:

#include <iostream> #include <stdexcept> #include <cassert> #include <ginac/ginac.h> using namespace std; using namespace GiNaC;

int main(int argc, char** argv) { symbol x("x"); symbol y("y"); ex a = pow(x,2) - pow(y,2); ex b = pow(x,4) - pow(y, 4); ex ca, cb; cout << "GCD(" << a << ", " << b << ") = "; ex ab_gcd = gcd(a, b, &ca, &cb, false); cout << ab_gcd << endl; assert((a-ca*ab_gcd).expand().is_zero()); assert((b-cb*ab_gcd).expand().is_zero()); return 0; }

Documentation (normal.cpp:1256) says \begin{quote} /* * Compute GCD (Greatest Common Divisor) of multivariate * polynomials a(X) and b(X) in Z[X]. Optionally also compute * the cofactors of a and b, defined by a = ca * gcd(a, b) * and b = cb * gcd(a, b). */ \end{quote}

so this behaviour is probably a bug.

I've got a patch to fix it (see attachment #1), but I'm not sure if it is correct.

Relevant part of gdb session is attached too.

P.S.

I use GiNaC 1.3.1 from CVS, g++-3.4 from Debian testing.

-- Best regards, Alexei