Singular

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.
difform df = 3*dx*dz - x8*dx*dy;
difform dg = 3 + x8*dy;
difform dh = 2;
difform dt = 0;
/////////////////////////////////
// Homogeneous of given degree //
/////////////////////////////////
difformIsHomogDeg(df,2);
==> 1
difformIsHomogDeg(dh,0);
==> 1
difformIsHomogDeg(dt,-1);
==> 1
/////////////////////////////////////
// Not homogeneous of given degree //
/////////////////////////////////////
difformIsHomogDeg(df,1);
==> 0
difformIsHomogDeg(dg,1);
==> 0
difformIsHomogDeg(dh,1);
==> 0
kill Omega_R,df,dg,dh,dt,dx,dy,dz;