Fast fourier transform matlab code

Please Copy and paste this code in matlab m-file
%-- *********************************************************
%
%-- Wins
%-- Suhap Sahin
%-- 04/02/2009
%-- Fast Fourier Transform
%--
%-- *********************************************************
clear;
clc;
%-- Input vector
Xn=[1 3 0 2 4 1 0 2 2 0 1 4 2 0 3 1 1 3 0 2 4 1 0 2 2 0 1 4 2 0 3 1 1 3 0 2 4 1 0 2 2 0 1 4 2 0 3 1 1 3 0 2 4 1 0 2 2 0 1 4 2 0 3 1 ...
1 3 0 2 4 1 0 2 2 0 1 4 2 0 3 1 1 3 0 2 4 1 0 2 2 0 1 4 2 0 3 1 1 3 0 2 4 1 0 2 2 0 1 4 2 0 3 1 1 3 0 2 4 1 0 2 2 0 1 4 2 0 3 1];
%-- Modify the input vector to have pair that traet fft on that
m_Xn=[];
p=1;
for i=1:length(Xn)/2
m_Xn(p)=Xn(i);
m_Xn(p+1)=Xn(i+length(Xn)/2);
p=p+2;
end
Xn=m_Xn;

N=2;
for i=1:2:length(Xn)
for k=1:N
k=k-1
Xk(i+k)=Xn(i)+exp(-j*2*(pi/N)*(k))*Xn(i+1);
end
end
u=length(Xn)/2;
for d=1:log2(u)
Xn=Xk;
Xk=0;
N=N*2;
k=0;
s=1;
for i=1:u
Xk(s)=Xn(i)+exp(-j*2*(pi/N)*(k))*Xn(i+u);
Xk(s+N/2)=Xn(i)-exp(-j*2*(pi/N)*(k))*Xn(i+u);
k=k+1;
s=s+1;
if k == N/2
k=0;
s=s+N/2;
end
end
end
Xn=Xk