Как работает классическая сборка мусора в лиспе? Сколько памяти занимает cons-ячейка? - Lisp

(defun powerset (lst)
  (loop for i below (expt 2 (length lst)) collect
       (loop for j below i for x in lst if (logbitp j i) collect x)))
 
(defstruct thing id weight value)
 
(defun read-lines-as-lists (filename)
    (with-open-file (stream filename)
        (loop for line = (read-line stream nil)
            while line collect (read-from-string (concatenate 'string "(" line ")")))))
 
(defun lists-to-things (lst)
    (mapcar #'(lambda (x) (make-thing :id (first x) :weight (second x) :value (third x))) lst))
 
(defun sum-by-param (param things-lst)
    (reduce #'+ (mapcar param things-lst)))
 
(defun special-print (x)
    (format t "-----------------------------------~%< weight: ~a, value: ~a >~%" (second x) (third x))
    (dolist (i (car x))
        (format t "id: ~a,~aweight: ~a,~avalue: ~a~%" (thing-id i) #\tab (thing-weight i) #\tab (thing-value i))))
 
(defun print-result (x)
    (special-print (first x))
    (when (= (third (first x)) (third (second x)))
        (print-result (cdr x))))
 
(defun main (filename)
    (let ((maxWeight 0)
          (lst (read-lines-as-lists filename)))
        (setf maxWeight (car (car lst))
              lst       ((lambda (x) (sort x #'> :key #'third)) 
                            (remove-if #'(lambda (x) (> (second x) maxWeight)) 
                                (mapcar #'(lambda (x) (list x (sum-by-param 'thing-weight x) (sum-by-param 'thing-value x))) (powerset (lists-to-things (cdr lst)))))))
        (print-result lst)))

360
1 10 60
2 20 200
3 55 120
4 30 120
5 40 110
6 40 80
7 30 20
8 15 320
9 10 10
10 90 120
11 30 70
12 5 10
13 50 10
14 50 100
15 20 10
16 5 5
17 75 15
18 45 110
19 50 50
20 50 105
21 20 35
22 20 35
23 20 35