Singular Manual: variablesSorted

| ##### 7.5.3.0. variablesSorted Procedure from library `central.lib` (see central_lib). Usage: variablesSorted(); Return: ideal, generated by sorted algebra variables Purpose: computes the set of algebra variables sorted so that Cartan variables go first Note: This is a heuristics for the computation of the center: it is better to compute centralizers of Cartan variables first since in this case we can omit solving the system of equations. Example:
    LIB "central.lib";
    ring AA = 0,(x,y,z),dp;
    matrix D[3][3]=0;
    D[1,2]=-z;  D[1,3]=2*x;  D[2,3]=-2*y;
    def A = nc_algebra(1,D); setring A; // this algebra is U(sl_2)
    // There is only one Cartan variable - z in U(sl_2),
    // it must go 1st:
    variablesSorted();
    ==> _[1]=z
    ==> _[2]=y
    ==> _[3]=x
See also: variablesStandard.

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