Singular

LIB "difform.lib";
ring R = 0,(x,y,z,t),dp;
diffAlgebra();
==> // The differential algebra Omega_R was constructed and the differential \
   forms dDx, dDy, dDz, dDt, dx, dy, dz, dt are available.
/////////////////////////
// Sortation of a list //
/////////////////////////
list L = dx*x, x2 - y*t, 12, dt*dy*dx*dz;
// Sort list with standard ordering
difformListSort(L);
==> [1]:
==>    12
==> 
==> [2]:
==>    x2-yt
==> 
==> [3]:
==>    x*dx
==> 
==> [4]:
==>    dx*dy*dz*dt
==> 
// Sort list with changed ordering
difformListSort(L,"gen","ls","ringvar","wp",intvec(-1,1,1,1));
==> [1]:
==>    dx*dy*dz*dt
==> 
==> [2]:
==>    x*dx
==> 
==> [3]:
==>    12
==> 
==> [4]:
==>    x2-yt
==> 
/////////////////////////////////////////////
// Sortation of list with structure "Dlist" //
/////////////////////////////////////////////
list DL;
DL[1] = list(dx,x,t,dt); DL[2] = list(y,t*z,4,x);
// This list has the structure described by "Dlist"
difformListSort(DL,"Dlist","ringvar","ls");
==> [1]:
==>    [1]:
==>       x
==> 
==>    [2]:
==>       t
==> 
==>    [3]:
==>       dt
==> 
==>    [4]:
==>       dx
==> 
==> [2]:
==>    [1]:
==>       zt
==>    [2]:
==>       4
==>    [3]:
==>       x
==>    [4]:
==>       y
/////////////////////////////////////////////
// Sortation of list with structure "Llist" //
/////////////////////////////////////////////
list LL;
LL[1] = list(dx,x); LL[2] = list(t*dt,y); LL[3] = list(x,2);
// This list has the structure described by "Llist"
difformListSort(LL,"Llist");
==> [1]:
==>    [1]:
==>       x
==> 
==>    [2]:
==>       2
==> [2]:
==>    [1]:
==>       t*dt
==> 
==>    [2]:
==>       y
==> [3]:
==>    [1]:
==>       dx
==> 
==>    [2]:
==>       x
kill Omega_R,dx,dy,dz,dt,L,DL,LL;