| ##### 7.5.4.0. Sannfs Procedure from library `dmod.lib` (see dmod_lib). Usage: Sannfs(f [,S,eng]); f a poly, S a string, eng an optional int Return: ring Purpose: compute the D-module structure of basering[f^s] with the algorithm given in S and with the Groebner basis engine given in eng Note: activate the output ring with the `setring` command. The value of a string S can be 'bm' (default) - for the algorithm of Briancon and Maisonobe, 'lot' - for the Levandovskyy's modification of the algorithm of OT, 'ot' - for the algorithm of Oaku and Takayama. If eng <>0, `std` is used for Groebner basis computations, otherwise, and by default `slimgb` is used. In the output ring: - the ideal LD is the needed D-module structure. Display: If `printlevel`=1, progress debug messages will be printed, if `printlevel`>=2, all the debug messages will be printed. Example:
    LIB "dmod.lib";
    ring r = 0,(x,y,z),Dp;
    poly F = x^3+y^3+z^3;
    printlevel = 0;
    def A  = Sannfs(F); // here, the default BM algorithm will be used
    setring A;
    LD;
    ==> LD[1]=z^2*Dy-y^2*Dz
    ==> LD[2]=x*Dx+y*Dy+z*Dz-3*s
    ==> LD[3]=z^2*Dx-x^2*Dz
    ==> LD[4]=y^2*Dx-x^2*Dy

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