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From: anw@maths.nott.ac.uk (Dr A. N. Walker)
Newsgroups: comp.lang.misc
Subject: Re: C's sins of commission
Message-ID: <1990Nov2.172508.6393@maths.nott.ac.uk>
Date: 2 Nov 90 17:25:08 GMT
References: <2062@aber-cs.UUCP> <1990Oct26.155937.29185@maths.nott.ac.uk> <PCG.90Oct30201101@teachk.cs.aber.ac.uk>
Reply-To: anw@maths.nott.ac.uk (Dr A. N. Walker)
Organization: Maths Dept., Nott'm Univ., UK.
Lines: 35

In article <PCG.90Oct30201101@teachk.cs.aber.ac.uk> pcg@cs.aber.ac.uk
(Piercarlo Grandi) writes:

	[Well, what he wrote, I found rather confusing (even assuming
that he means by Bell's Theorem what I mean by Bell's Inequalities).
I *think* it amounted to the following:

pcgp>	You shouldn't write "node := GREEN; ptr_to_node := node" because
pcgp>	"node" then doesn't include its location.  You should have instead
pcgp>	"node := { GREEN, node }" and then an associative search for
pcgp>	"{ GREEN, node }" will find node without the need for pointers.

(pcgp means PierCarlo Grandi Paraphrase).  In the following direct
extract, "This" means the version that I *shouldn't* write.]

>This adds a whole new world of complication, because we need no longer
>just an algebra for objects, but also an algebra for locations, and we
>must prove that a program not only works ok wrt to contents, but also to
>locations, and that the encoding of parts of the contents in the
>location is preserved correctly.

	But if content has to include location, then an algebra for
objects has to include an algebra for location, so the algebra and the
proofs already had to be supplied.  Furthermore, if I am denied access
to the algebra of locations, then some useful ideas like anonymous
objects, and like remembering locations, become inexpressible.

	In other words, either the PCGP bears no relationship to what
PCG *meant* to write, or else PCG's article was self-evident nonsense.
At the end of a difficult week, I'm in no fit state to decide which,
but I have my suspicions.

-- 
Andy Walker, Maths Dept., Nott'm Univ., UK.
anw@maths.nott.ac.uk