(bind-func window_hanning
(let ((i:i64 0))
(lambda (window_buffer:double* window_length)
(dotimes (i window_length)
(pset! window_buffer i
(* (pref window_buffer i)
(- 0.5 (* 0.5 (cos (/ (* TWOPI (i64tod i))
(i64tod (- window_length 1)))))))))
void)))