Path: utzoo!attcan!uunet!munnari.oz.au!goanna!ok
From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.misc
Subject: Re: Answers, Chapter 1: TeX (was C's sins... and others)
Message-ID: <4124@goanna.cs.rmit.oz.au>
Date: 29 Oct 90 09:26:16 GMT
References: <26726@megaron.cs.arizona.edu> <1990Oct29.051730.10838@murdoch.acc.Virginia.EDU>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 39

In article <1990Oct29.051730.10838@murdoch.acc.Virginia.EDU>, gl8f@astsun7.astro.Virginia.EDU (Greg Lindahl) writes:
> In article <4119@goanna.cs.rmit.oz.au> ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes:
> >Yes, *sigh* we're all talking past each other.
> >	THIS IS NOT AN INTRINSIC PROPERTY OF POINTERS;
> >	it is a property of the programming language *C*.

> Depends on how you define "pointers" ;-)

I certainly *don't* define "pointer" to mean "exactly what C means by
a pointer, no more, no less".  PL/I and Pascal and Algol 68 are some
well-known languages that have pointer-valued variables; Euclid is a
language which deserved to be better known.
None of them provides pointer arithmetic or pointer ordering.

If people want to say "pointer ARITHMETIC" is bad, let them say so.
If people want to say "pointer ORDERING" is bad, let them say so.
If people say "POINTERS" are bad, and they are talking with the
intention of being understand, then they are referring to the
idea behind PL/I POINTER, Pascal "^", Algol 68 and Mary REF, and
Euclid's whatever-it-was.  The question is whether this common
idea can be "tamed".  I am still waiting to hear what the objection
to Euclid's construct is.

> >To put this into C terms, suppose we introduce a new type
> >constructor "pointer into named array".

> C already has these. An example:

>      float a[100];
>      int i = 10;
>      a[i];

Where is "i" constrained to index only "a"?
(Am I the only person who remembers ESPL?  In ESPL you *could*
declare a variable to be a "verified index" for a particular array.)

-- 
The problem about real life is that moving one's knight to QB3
may always be replied to with a lob across the net.  --Alasdair Macintyre.