function w = hann(N)
    // Periodic Hann window
    // Usage:
    //       w = hann(N)
    // Where 
    //       N: Length of Hann window
    //       w: Vector containing the periodic Hann window
    // ---------------------------------- 
    w = 0.5 - 0.5*cos(2*%pi*(0:N-1)/N);
endfunction
