My macsyma defaults gcd to spmod. Maxima defults gcd to subres.
Further, some Maxima bugs go away when gcd is changed to spmod.
But consider this
(C1) display2d : false$
(C2) p : x^2 + x + 1$
(C3) sol : first(solve(p,x))$
(C4) sol : lhs(sol)-rhs(sol)$
(C5) gcd : subres$
(C6) algebraic : true$
(C7) ratsimp(p/sol);
(D7) (4*x-2*SQRT(3)*%I+2)/4
(C8) gcd : spmod$
(C9) ratsimp(p/sol);
(D9) (2*x^2+2*x+2)/(2*x+SQRT(3)*%I+1)
(C10) build_info();
With gcd == subres, the common factor of p and sol cancel. This
doesn't happen with gcd == spmod. Is this a spmod bug? A
subres bug? Or neutral? I get the same behavior with my macsyma.
Maxima version: 5.9.0.1cvs
Maxima build date: 11:29 3/24/2004
host type: i686-pc-mingw32
lisp-implementation-type: Kyoto Common Lisp
lisp-implementation-version: GCL 2.7.0
Barton