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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: The future of Spark . Spark 2014 : a wreckage
Date: Tue, 09 Jul 2013 12:29:03 +0100
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Date: 2013-07-09T12:29:03+01:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> On Mon, 8 Jul 2013 16:32:21 -0500, Randy Brukardt wrote:

>> that they use whatever information is available, and most of all,
>> that they only depend on the specifications of packages (never, ever,
>> on the contents of a body).
>
> There are obviously goals which cannot be proven without the
> bodies. Proofs about specifications are important but far not
> all. Consider LSP as an example. You cannot prove substitutability
> from interfaces. It simply does not work. Same with almost everything
> else, because proving something in general is much more harder, even
> impossible, than proving things about a concrete instance, e.g. body.

I think what Randy meant (and may even have said) was that in

   with A;
   package B is ...

it shouldn't be necessary to look at the body of A to prove the body of
B. Of course the body of A will have to be proved ... but not right now.