Singular Manual: isTwoSidedGB

| ##### 7.5.1.0. isTwoSidedGB Procedure from library `bimodules.lib` (see bimodules_lib). Usage: isTwoSidedGB(I); I ideal Return: Returns 0 if the generators of a given ideal are not two-sided, 1 if they are.\\ Note: This procedure should only be used for non-commutative rings, as every element is two-sided in a commutative ring. Purpose: Auxiliary procedure for diagonal forms. Let R be a non-commutative ring (e.g. G-algebra), and p in R, this program checks whether p is two-sided i.e. Rp = pR. Example:
    LIB "bimodules.lib";
    ring r = 0,(x,s),dp;
    def R = nc_algebra(1,s); setring R; //1st shift algebra
    ideal I = s^2, x*s, s^2 + 3*x*s;
    isTwoSidedGB(I); // I is two-sided
    ==> 1
    ideal J = s^2+x;
    isTwoSidedGB(J); // J is not two-sided; twostd(J) = s,x;
    ==> 0

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