[Chicken-users] General newbie query about tspl execise

[Enwin Thun]

Please redirect me if this is inappropriate for this forum.

The following code appears in the tspl book.
<http://www.scheme.com/tspl3/start.html#./start:s185>

It is an "implementation of a queue use[ing] a tconc structure".

To put new elements into the end of the list, it is required that the
2 'ignored atoms are really the same.

This makes me curious about how atoms and lists are stored.  I am
looking for a link that explains this in terms of memory addresses,
pointers, etc.  A link for general discussion about memory management
in scheme would also be nice.

Thanks.

(define make-queue
  (lambda ()
    (let ((end (cons 'ignored '())))
      (cons end end))))

(define putq!
  (lambda (q v)
    (let ((end (cons 'ignored '())))
      (set-car! (cdr q) v)
      (set-cdr! (cdr q) end)
      (set-cdr! q end))))

(define getq
  (lambda (q)
    (car (car q))))

(define delq!
  (lambda (q)
    (set-car! q (cdr (car q)))))