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From: peter@ficc.ferranti.com (Peter da Silva)
Newsgroups: comp.lang.misc
Subject: Re: Some things that pointer-less languages can't do efficiently
Message-ID: <5P57P18@xds13.ferranti.com>
Date: 23 Nov 90 17:44:49 GMT
References: <26739:Oct1023:44:2690@kramden.acf.nyu.edu> <65450@lanl.gov> <10397:Oct1212:55:1090@kramden.acf.nyu.edu> <3975@goanna.cs.rmit.oz.au> <3716@skye.ed.ac.uk> <HEZ6WP9@xds13.ferranti.com> <3808@skye.ed.ac.uk>
Reply-To: peter@ficc.ferranti.com (Peter da Silva)
Organization: Xenix Support, FICC
Lines: 12

In article <3808@skye.ed.ac.uk> jeff@aiai.UUCP (Jeff Dalton) writes:
> What you can't do is:

>   (setq a '(some list))
>   (setq b (pointer-to (cdr a)))

But "a" is already a "pointer" to "cdr a". In this case the "reference"
operation is simply "cdr".

You want to factor the pointer out of the cons. I don't care if you can
or not: the cons already has the same semantics as a pair of pointers, and
everything that can be said "about" pointers can be said "about" a cons.
-- 
Peter da Silva.   `-_-'
+1 713 274 5180.   'U`
peter@ferranti.com