Scheme bezier of n order

gistfile1.txt

(require-extension srfi-4 glm)
(require-extension list-utils)
(require-extension statistics)

(define (mapi p l)
  (let loop ((l l) (i 0) (r '()))
    (if (pair? l)
        (loop (cdr l) (+ i 1) (cons (p (car l) i) r))
        (reverse r))))

(define (bezier points)
  (lambda (t)
    (let ((n (length points)))
        (define (calc point i)
          (v* point (* (combinations n i) (expt (- 1 t) (- n i)) (expt t i))))
        (fold (lambda (left right)
                (v+ left right)) (vec3 0 0 0) (mapi calc points)))))

(define bez (bezier `(,(vec3 1 1 1)
                      ,(vec3 2 2 2)
                      ,(vec3 2 2 2)
                      ,(vec3 2 2 2)
                      ,(vec3 2 2 2)
                      ,(vec3 2 2 2)
                      ,(vec3 2 2 2)
                      ,(vec3 2 2 2)
                      ,(vec3 3 3 3))))

(time
    (begin
      (print (bez 0))
      (print (bez 0.25))
      (print (bez 0.5))
      (print (bez 0.75))
      (print (bez 1.0))))