if; end for;
    d:=Degree(h); h1:=Matrix(F,1,d+1,[Eltseq(h)[i]: i in {1..d+1}]);
    h2:=ReverseColumns(h1);
    h3:=Matrix(F,1,d+1,[h2[1][i]^((p^t)^(i-1)): i in {1..d+1}]);
    h4:=(1/h3[1][d+1])*h3; h5:=R![h4[1][i]: i in {1..d+1}];
    k:=Degree(f)-Degree(h5); V:=VectorSpace(F,n);
    H:=Matrix(F,k,n,[V!(HorizontalJoin(Matrix(1, j+Degree(h5)+1, 
    Eltseq((R![0,1])^j*h5)), ZeroMatrix(F, 1, n-j-Degree(h5)-1))): 
    j in {0..k-1}]); k2:=Degree(f)-Degree(g1);
    G:=Matrix(F,k2,n,[V!(HorizontalJoin(Matrix(1, j+Degree(g1)+1, 
    Eltseq((R![0,1])^j*g1)), ZeroMatrix(F, 1, n-j-Degree(g1)-1))): 
    j in {0..k2-1}]); L:=LinearCode(G); LD:=LinearCode(H);
    print "==========================================="; print " ";
    print "Code Skew", a,"-cyclic of type: ", n, k2, MinimumWeight(L);
    print " "; print "Polynomial generator:"; print g1; print " ";
    print "Generator Matrix:"; print G; print " ";
    print "-------------------------------------------"; print " ";
    print "Dual Code Skew", 1/a,"-cyclic of type: ", n, k, 
    MinimumWeight(LD); print " "; print "Check Polynomial:"; 
    print h5; print " "; print "Parity Check Matrix:"; print H; 
    print " "; print G*Transpose(H); Q:=[0];
    print "===========================================";
    for j in [1..n-2] do
    Q:=Q cat [0]; end for;
    U:= [-a^-1] cat P cat [1]; Z:=R!U; Z; h5;
    Quotrem(R!Z,R!h5); return "end";
    end function;

Consider the finite field $\F_4=\{ 0,1,w,w^2\}$, where $w^2+w+1=0$, and the Frobenius automorphism $\theta :\F_4\to\F_4$ defined by $\theta(x)=x^2$. Let $\mathscr{C}$ be the skew $w$-cyclic $[8,2,4]_4-$code generate by the polynomial $x^6+wx^4+w^2 x^2+1$ (command +SD(8,w)+ in Program $1$) with generator matrix $$\begin{pmatrix}
1 & 0 & w^2 & 0 & w & 0 & 1 & 0 \\
0 & 1 & 0 