envelope-segments   xtlang

(bind-func envelope-segments
  (lambda (points:double* num-of-points:i64)
    (let ((lines:[double,double]** (zone-alloc num-of-points))
          (k 0))
      (dotimes (k num-of-points)
        (let* ((idx (* k 2))
               (x1 (pointer-ref points (+ idx 0)))
               (y1 (pointer-ref points (+ idx 1)))
               (x2 (pointer-ref points (+ idx 2)))
               (y2 (pointer-ref points (+ idx 3)))
               (m (if (= 0.0 (- x2 x1)) 0.0 (/ (- y2 y1) (- x2 x1))))
               (c (- y2 (* m x2)))
               (l (lambda (time) (+ (* m time) c))))
          (pointer-set! lines k l)))
      lines)))