Singular Manual: closureFrac

| #### D.4.25.7 closureFrac Procedure from library `normal.lib` (see normal_lib). Usage: closureFrac (L); L a list of size n+1 as in the result of primeClosure, L[n] contains an additional polynomial f Create: a list fraction of two elements of L[1], such that f=fraction[1]/fraction[2] via the injections phi L[i]-->L[i+1]. Example:
    LIB "normal.lib";
    ring R=0,(x,y),dp;
    ideal ker=x2+y2;
    export ker;
    list L=primeClosure(R);          // We normalize R/ker
    for (int i=1;i<=size(L);i++) { def R(i)=L[i]; }
    setring R(2);
    kill R;
    phi;                             // The map R(1)-->R(2)
    ==> phi[1]=X(1)
    ==> phi[2]=X(2)
    poly f=T(2);                     // We will get a representation of f
    export f;
    L[2]=R(2);
    closureFrac(L);
    setring R(1);
    kill R(2);
    fraction;                        // f=fraction[1]/fraction[2] via phi
    ==> [1]:
    ==>    x
    ==> [2]:
    ==>    y
    kill R(1);

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