 ring r=32003,(x,y,z),dp;
poly f=x5+5x4y+10x2y3+y5;
matrix m=coef(f,y);
print(m);
==> y5,y3, y, 1,
==> 1, 10x2,5x4,x5
f=x20+xyz+xy+x2y+z3;
print(coef(f,xy));
==> x20,x2y,xy, 1,
==> 1, 1, z+1,z3
vector v=[f,zy+77+xy];
print(v);
==> [x20+x2y+xyz+z3+xy,xy+yz+77]
matrix mc; matrix mm;
coef(v,y,mc,mm);
print(mc);
==> x2+xz+x,x20+z3,
==> x+z, 77
print(mm);
==> y,1,
==> y,1
