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From: eberard@ajpo.sei.cmu.edu (Edward Berard)
Newsgroups: comp.lang.ada
Subject: Re: Record rep specs for private components
Keywords: Ada, Rep Specs, Private Types, Compilers
Message-ID: <523@ajpo.sei.cmu.edu>
Date: 18 Jun 89 14:30:51 GMT
List-Id: <comp.lang.ada>

I have a problem with the following:

>   package a is
>      type aa is private;
>   private
>      type aa is range 0..1000;
>   end a;
>
>   with a;
>   package b is
>      type bb is record
>         bbb : a.aa;
>      end record;
>      for bb use record
>        at mod 2;
>        bbb at 0 range 0..15;       --Legal?
>      end record;
>      x : bb;
>   end b;

If type a.aa is private, then its underlying implementation should be
unknown outside of package a. This means that it should be impossible
for another program unit to specify how much space an instance of this
type should take up. [Of course, package a could supply operations
which could provide alternative representations of known sizes, and
these could be used in other program units.]

In short, if the rep spec is legal Ada, it should not be, and should
be fixed in Ada 9X.

				-- Ed Berard
				   (301) 353-9652