Subject: Re: Cons Cell Representation---`sameness' again
From: Erik Naggum <>
Date: 1999/04/07
Newsgroups: comp.lang.lisp
Message-ID: <>

* Barry Margolin <>
| If the microscope operates at the machine level, addresses become
| apparent.  At that level, an object is not really the "same" before and
| after a copying GC, because its address has changed.  They're two
| different machine-level objects that happen to represent the same Lisp
| object at different times.

  if you can retain a pre-GC pointer to an object past the GC, you have a
  reportable GC bug or a violation of the sanity of the system.  I'm not
  sure this helps anyone understand anything at all.  so, I still think I'm
  missing something, or that this is just a waste of time.

| Vassil has made it clear in other posts that he was answering a different
| question than what was originally posed, I suspect to encourage this
| meta-level discussion about sameness.

  we might as well discuss sameness of objects before and after a page of
  virtual memory has been paged out and then in again at different physical
  machine addresses.  again, I'm not sure there is enlightenment to be
  found anywhere along this path.