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From: card@syr.lmco.com
Subject: Re: Visibility and access to "public" attributes
Date: 1997/09/02
Message-ID: <873212609.24297@dejanews.com>#1/1
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To: card@syr.lmco.com
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Newsgroups: comp.lang.ada,comp.lang.eiffel
Date: 1997-09-02T00:00:00+00:00
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I'd like to thank everyone who replied to my original
post RE: visibility of attributes.

I had wondered when/why one would make a class'
attributes read-only rather than hiding them altogether.
The answer to my question was provided by Peter Horan:

>One must export parameters and functions when they
>are needed to verify pre-conditions. This is an
>Eiffel validity requirement (VAPE). (I am reminded
>of keeping one's fingers crossed when making
>promises :-)). This does not apply to features in
>post-conditions and invariants, which may be more
>restrictive than the client needs without harm.

This makes sense. Since everything in a precondition
must be visible to a class's client(s), then the
client must be able to read the class's attributes
(features) if they are used in the precondition(s).

Thanks, Pete!

- Mike

---------------
Michael P. Card
Lockheed Martin Ocean, Radar and Sensor Systems Division
Syracuse, NY 13221
voice: (315)-456-3022  FAX: (315)-456-2414  e-mail:card@syr.lmco.com

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