From: Pierre Vachon
Subject: Pointers in Lisp (again...)
Date:
Message-ID: <vachon.733628816@matane>
Different question, same subject...
Is there a way to tell Lisp to return the _address_ of something �I'm
referencing instead of the actual value? This is done automatically for
arrays, for example:
LISP> (setf array (make-array...�))
#<Array 0x24E5A23>
LISP> (setf other array)
#<Array 0x24E5A23>
A change to 'other' will also change 'array'... and I would like to do
the same with this:
LISP> (setf a '(0 1 2 3 4 5))
(0 1 2 3 4 5)
LISP> (special-setf temp (cdr a))
#<Address 0xD43E234>
LISP> (setf temp 'changed)
CHANGED
LISP> a
(0 CHANGED)
Why do I need this? Well, I've done a whole project with a
non-pointer structure, saving processing time and memory, but the
_very last part_ (of course...) involves changing many values in very
large & deeply nested lists DEPENDING ON WHAT'S ALREADY THERE. I'm
looking for a way to cut CPU time by not having to "destructure" the list
twice: once for testing, once for setting (if necessary..).
Thanks in advance!
Pierre.
In article <················@matane> ······@gel.ulaval.ca (Pierre Vachon) writes:
>LISP> (special-setf temp (cdr a))
>#<Address 0xD43E234>
>
>LISP> (setf temp 'changed)
>CHANGED
>
>LISP> a
>(0 CHANGED)
>
>Why do I need this? Well, I've done a whole project with a
>non-pointer structure, saving processing time and memory, but the
>_very last part_ (of course...) involves changing many values in very
Clue: what is the 'normal' implementation of a cons? What happens if you
set a and b to point to a cons cell, and do a rplaca on the cons?
Simon
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