// given a vectorial Boolean function in univariate form, returns its gamma-rank 
function gammaRank(f)
        R:=Parent(f);
        Fn:=BaseRing(R);
        n:=2*Degree(Fn);
        M:=ZeroMatrix(GF(2),2^n,2^n);
        W:=VectorSpace(GF(2),n);

        Gf:={W!(Eltseq(v) cat Eltseq(Evaluate(f,v))): v in Fn};
        for w in W do
                ww:=[Integers()!w[i]:i in [1..n]];
                j:=SequenceToInteger(ww,2)+1;
                GFtilde:={r+w:r in Gf};
                for v in GFtilde do
                        vv:=[Integers()!v[i]:i in [1..n]];
                        i:=SequenceToInteger(vv,2)+1;
                        M[i][j]:=1;
                end for;
        end for;
        return Rank(M);
end function;