arithmetic with residue of polynomials in giac/XCas?

[jocaps]

Is it possible to use residue ring arithmetic in giac, e.g. instead of Q[x0,x1,x2] I want to do arithmetic in Q[x0,x1,x2]/<f1,f2> for some polynomials f1, f2. I can always artificially induce this, but many things may break if this is not internally encoded (for instance matrix arithmetic with entries in this ring, using linsolve etc.). My motivation for this is that I work very often on some function field or sometimes on some algebraic numbers (at the moment I just do rem on defining polynomials of multiple algebraic numbers or of an ideal of the polynomial ring) and I would need to do this and my code becomes extremely error prone if I keep using rem(rem(g,f1),f2) to do arithmetic.

[parisse]

Did you try with rootof?