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From: kend@data.UUCP (Ken Dickey)
Newsgroups: comp.lang.misc
Subject: Re^6: Some things that pointer-less languages can't do efficiently
Message-ID: <421@data.UUCP>
Date: 25 Oct 90 20:58:07 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> <415@data.UUCP> <+CI6:YD@xds13.ferranti.com> <418@data.UUCP> <83N6E05@xds13.ferranti.com>
Organization: Microcosm, Beaverton, OR
Lines: 37

peter@ficc.ferranti.com (Peter da Silva) writes:

>First of all... what's a pointer? It's not a machine address. A pointer is
>a token that refers to a value, such that it can refer to any value in
>the domain of the language, and that more than one such token can refer
>to a given value. The operation of getting to the value referred to is
>called dereferencing.

Where are you getting your definition of pointer?  Not from K & R: "The
C Programming Language.  Not from Ullman: "Fundamental Concepts of
Programming Systems".  Not from Trembly & Sorenson "An Introduction to
Data Structures with Applications".  Et cetera...  Have you ever heard
the phrase "pointer arithmetic"?


>In article <418@data.UUCP> kend@data.UUCP (Ken Dickey) writes:
>> Gee, I thought there was this constructor CONS which takes two values.

>And returns a pair of pointers. It can be implemented by writing down on
>a piece of paper the safe-deposit-box-numbers of a safe-deposit-box in
>New York City, but it is still functionally a pair of pointers.

(cons 3 3) returns an *object* with 2 *values* and NO pointers!


>> It is true that there are pointers all through typical implementatons
>> of Scheme, but there is no "pointer" in the definition of the language!

>This is only a true statement if you think "machine address" when I say
>"pointer".

Thats right!  I think "store location" when you say "pointer"! 

You will ceratinly find no mention of "pointer" in the Scheme language.


-Ken Dickey			kend@data.uucp