순서쌍은 나란한 car·cdr 벡터를 가리키는 주소가 될 수 있다.

(begin
  (define (tagged-list? value tag)
    (and (pair? value) (eq? (car value) tag)))
  (define (make-vector-memory capacity)
    (list '*vector-memory*
          (make-vector capacity '*unused*)
          (make-vector capacity '*unused*)
          (cons 'free 0)))
  (define (memory-cars memory) (list-ref memory 1))
  (define (memory-cdrs memory) (list-ref memory 2))
  (define (memory-free-cell memory) (list-ref memory 3))
  (define (memory-free memory) (cdr (memory-free-cell memory)))
  (define (set-memory-free! memory value)
    (set-cdr! (memory-free-cell memory) value))

  (define (pair-pointer? value) (tagged-list? value 'ptr))
  (define (make-pointer index) (list 'ptr index))
  (define (pointer-index pointer) (cadr pointer))

  (define (allocate-pair! memory car-value cdr-value)
    (let ((index (memory-free memory)))
      (if (>= index (vector-length (memory-cars memory)))
          (error "vector memory exhausted" index)
          (begin
            (vector-set! (memory-cars memory) index car-value)
            (vector-set! (memory-cdrs memory) index cdr-value)
            (set-memory-free! memory (+ index 1))
            (make-pointer index)))))
  (define (memory-car memory pointer)
    (vector-ref (memory-cars memory) (pointer-index pointer)))
  (define (memory-cdr memory pointer)
    (vector-ref (memory-cdrs memory) (pointer-index pointer)))
  (define (set-memory-car! memory pointer value)
    (vector-set! (memory-cars memory)
                 (pointer-index pointer)
                 value))
  (define (set-memory-cdr! memory pointer value)
    (vector-set! (memory-cdrs memory)
                 (pointer-index pointer)
                 value))

  (define (list->memory values memory)
    (if (null? values)
        '()
        (let ((tail (list->memory (cdr values) memory)))
          (allocate-pair! memory (car values) tail))))
  (define (memory->list pointer memory)
    (if (null? pointer)
        '()
        (cons (memory-car memory pointer)
              (memory->list (memory-cdr memory pointer)
                            memory))))
  (define (used-vector-prefix values count)
    (define (loop index result)
      (if (= index count)
          (reverse result)
          (loop (+ index 1)
                (cons (vector-ref values index) result))))
    (loop 0 '()))
  (define memory (make-vector-memory 8))
  (define root (list->memory '(a b c) memory))
  (list (memory-free memory)
        root
        (memory->list root memory)
        (memory-car memory root)
        (memory-car memory (memory-cdr memory root))
        (memory-car memory
                    (memory-cdr memory
                                (memory-cdr memory root)))
        (used-vector-prefix
          (memory-cars memory)
          (memory-free memory))
        (used-vector-prefix
          (memory-cdrs memory)
          (memory-free memory)))
)