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From: dd@sei.cmu.edu (Dennis Doubleday)
Newsgroups: comp.lang.ada
Subject: Re: Ada language revision
Message-ID: <7796@aw.sei.cmu.edu>
Date: 23 Nov 88 13:37:52 GMT
References: <44449@beno.seismo.CSS.GOV> <3563@hubcap.UUCP> <7882@nsc.nsc.com> <739@marvin.cme-durer.ARPA>
Organization: Carnegie-Mellon University (Software Engineering Institute), Pgh, PA
In-reply-to: leake@cme-durer.ARPA's message of 22 Nov 88 14:37:13 GMT
List-Id: <comp.lang.ada>


In article <739@marvin.cme-durer.ARPA> leake@cme-durer.ARPA (Stephe Leake) writes:
>In article <7882@nsc.nsc.com> rfg@nsc.nsc.com (Ron Guilmette) writes
>>   I have some problems with limited private types too.  Specifically, if such
>>   types are really only accessable through a "limited" functional interface,
>>   then why shouldn't we be able to declare such types in the public part of
>>   a package and then defer the full declaration until the package body?
>
>What would this gain? Do you have any specific examples where this
>would have improved the readability or functionality of an
>application? Let's not just suggest changes because they "sound good".
>Let's put some thought into it, including concrete examples.

There is a VERY good reason for it, if you're at all concerned about
portability.  The declaration of a limited private type is an
IMPLEMENTATION decision.  It doesn't belong in the specification, it
belongs in the body.  If I'm trying to export some abstract data type
from a package, I'd like to have a specification that could be moved,
intact, from one machine to another.  Only the body should need
changing.  However, since I must give the full declaration of the type
in the private part of the spec instead of in the body, it may be that
I will have to change that part of the spec if I want to port the
package to a machine which requires a different implementation of the
type. 

Why does your post sound so hostile?  How do you know that Ron hasn't
put any thought into his suggested changes?

Dennis Doubleday                       dd@sei.cmu.edu
Software Engineering Institute         (412)268-5873
Carnegie Mellon University
Pittsburgh, PA 15213