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From: Ken Garlington <garlingtonke@lmtas.lmco.com>
Subject: Re: Modest proposal, 3 of 3
Date: 1996/11/25
Message-ID: <32999420.53AA@lmtas.lmco.com>#1/1
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references: <575aq0$t4j@netline-fddi.jpl.nasa.gov>
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organization: Lockheed Martin Tactical Aircraft Systems
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Date: 1996-11-25T00:00:00+00:00
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Van Snyder wrote:
> 
> BACKGROUND
> 
> This is OK, because there are only two things you can
> do with pointers (in a sane language): dereference them and copy them.

I'm not sure what a "sane" language is (isn't SANE a numerical representation?),
but I have certainly done mathematics with Ada accesses (systems programming-type
algorithms), and would like to continue to do so. Also, I'm not sure
what "copy" entails, but I assume this would permit access values to be passed
to subprograms.

> If one has a datum, say "A: T", and one later decides it's necessary to
> allocate it from the free store, the type of A changes from T to "access
> T".  That's not too bad.  But all the references change from "A" to
> "A.ALL".  That's bad.

Isn't this the general problem of making object declarations visible to clients,
as opposed to providing access routines (e.g., as an abstract data type/object)?
Other changes along these lines include changing from floating to fixed point,
chracter to a one-element string, etc. Certainly, with methodologies like
ADARTS, the programmer knows that a global variable in a package spec is a potential
maintenance issue later.

It doesn't seem that this is strong enough justification, given the incompatibilities
it would appear to introduce in existing code. (Doing a "simple" source translation
isn't so simple, I suspect, given all the ways in which access values can be used.)


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