bool DPoly::down_level(int newlevel, int oldlevel, poly &f)
{
if (f == 0) return true;
for (int i=oldlevel; i>newlevel; i--)
{
if (f->deg > 0)
{
dealloc_poly(f);
return false;
}
poly g = f->arr.polys[0];
f->arr.polys[0] = 0;
dealloc_poly(f);
f = g;
}
return true;
}
void ARingTower::reset_degree(poly &f) const
{
if (f == 0) return;
int fdeg = f->deg;
for (int j = fdeg; j >= 0; --j)
if (f->polys[j] != 0)
{
f->deg = j;
return;
}
// at this point, everything is 0!
dealloc_poly(f); // sets f to 0
}