LIB "reesclos.lib";
ring R=0,(x,y),dp;
ideal ker=x2+y2;
export R;
→ // ** `R` is already global
list L=primeClosure(R);          // We normalize R/ker
closureRingtower(L);             // Now R/ker=R(1) with normalization R(2)
setring R(2);
kill(R);
phi;                             // The map R(1)-->R(2)
→ phi[1]=T(1)*T(2)
→ phi[2]=T(1)
poly f=T(1)*T(2);                // We will get a representation of f
export R(2);
→ // ** `R(2)` is already global
closureFrac(L);
setring R(1);
kill (R(2));
fraction;                        // f=fraction[1]/fraction[2] via phi
→ [1]:
→    xy
→ [2]:
→    y