From: Greg Menke <nos...@erols.com>
Subject: Sharing of list elements in Common Lisp
Date: 1999/01/27
Message-ID: <socxxmta.fsf@erols.com>#1/1
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Hi,

I've a couple questions, if you wouldn't mind considering
them....

In Common Lisp, is it possible to have a list item shared 
in 2 or more lists; ie:

lista -> (a b c d)
listb -> (1 c 2 3)

where c is the same object?  By same object, I mean
when c is deleted from one list, it disappears from the
other.  It would also be desirable to preserve the linkage
even if the item moves in one or both lists.

Second, is it possible to record the position of
an item in a large list so the item may be efficently 
retrieved?

Third, is it possible to get a "handle" or pointer to a
list item which is independent of its position, or presence
in some other list?


Thanks,

Gregm