Product Excluding Self

#lang racket
;; Given a list of numbers, return a list where the i-th element corresponds to the multiplication of the initial list except its i-th element.

;; Example:
;; [1,2,3,4] -> [24, 12, 8, 6]

; index :: [Number] -> [(Integer, Number)]
; indexes a list of numbers
(define (index lNum)
  (for/list [(i (in-naturals))
             (n (in-list lNum))]
    (cons i n) ; tuple '(i . n)
    )
  )

; filter-i :: [(Integer, Number)] -> [(Integer, Number)]
; filters an indexed list, indexed-l, by removing
; the element with index i
(define (filter-i indexed-l idx)
  (filter [lambda (a) (not [eq? (car a) idx])] indexed-l)
  )

; product-ex-self :: [Number] -> [Number]
; produces a list of products of elements of list, l,
; in which, in each product, one of the list elements
; is excluded
(define (product-ex-self lNum)
  (let [(idx-l (index lNum)) ; indexed list
        ]
    ;--IN--
    (for/list [(ix (in-list idx-l))]
      (apply * (map cdr [filter-i idx-l (car ix)]))
      )
    )
  )

(define mylist (list 1 2 3 4))
(print (product-ex-self mylist))