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Newsgroups: comp.lang.ada
Date: Mon, 1 Jul 2013 04:14:43 -0700 (PDT)
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Subject: Re: "shadow" package hierarchy using renaming of child packages
From: Oliver Kellogg <okellogg@users.sourceforge.net>
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Xref: number.nntp.dca.giganews.com comp.lang.ada:182174
Date: 2013-07-01T04:14:43-07:00
List-Id: <comp.lang.ada>

On Monday, July 1, 2013 11:37:23, UTC+2 AdaMagica wrote:
> 
> > [...] In the example, apparently the declaration "subtype T is Foo.T;" in the
> > Shadow package spec creates the structural equivalence.
> No, it hasn't anything to do with structural equivalence.
> Just compare:
> [...]

Yikes, you're right!

Looking from the user perspective:
Imagine Shadow to preexist, with much code written against its API.
Imagine that a new package Foo representing a light-weight subset of the Shadow API is added to the system at a later date. Now the interesting thing is that the existing applications do not need to be changed.
In shadow-test.adb,
   I : Shadow.T := Shadow.Child.Create;
the declaration of T in Shadow ensures that.

Thanks.