LIB "difform.lib";
ring R = 0,(x,y,z),ds;
diffAlgebra();
==> // The differential algebra Omega_R was constructed and the differential \
   forms dDx, dDy, dDz, dx, dy, dz are available.
////////////////////////////////////////
// Construction of differential forms //
////////////////////////////////////////
poly f = 3x3z*(y4-y5) + 2;
difform df = f;
df;
==> 2+3x3y4z-3x3y5z
==> 
// For the construction of more general differential forms,
// the constructor difformFromPoly is used implicitly:
difform dg = 3*x*dx - y*dy + dx*dy*dz + 1;
dg;
==> 1+3x*dx+(-y)*dy+dx*dy*dz
==> 
kill Omega_R,df,dg,dx,dy,dz;