求用matlab程序，编写出高斯塞德尔迭代法

function [x,k,index]=GS(A,b,ep,it_max)

n=length(A);k=0;

x=zeros(n,1);

y=zeros(n,1);

index=1;

for k=1:it_max

y=x;

for i=1:n

z=b(i);

for j=1:n;

if j~=i

z=z-A(i,j)*x(j);

end

end

if abs(A(i,i))<1e-10

index=0;

return;

end

z=z/A(i:i);

x(i)=z;

end

if norm(y-x,inf)<ep

break;

end

end