diffop

diffop(E*X,[X,E],[1,X*E],10)
diffop(Mod(S/C,S^2+C^2-1),[C],[-S],10)
E4(n)=1+240*sum(i=1,n,sigma(i,3)*q^i)+O(q^(n+1));
diffop(E4(15),[q],[q])
diffop(Mod(y,x^2-y),[y],[1])
diffop(Mod(10^100,x^2+y),[y],[1])
diffop(lllx,[x,lx,llx,lllx],[1,1/x,1/(x*lx),1/(x*lx*llx)],6)*Mod(1,3)