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From: "G.B." <bauhaus@notmyhomepage.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Ada 2012 Constraints (WRT an Ada IR)
Date: Wed, 14 Dec 2016 19:55:17 +0100
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Xref: news.eternal-september.org comp.lang.ada:32826
Date: 2016-12-14T19:55:17+01:00
List-Id: <comp.lang.ada>

On 14/12/2016 17:55, Dmitry A. Kazakov wrote:
> You cannot say it in Ada, as the example shows. You must do that in English or in SPARK or in any other language where you can *spell* it. In Ada you cannot.

It?  Boolean expressions or expressions about Boolean
expressions? Rules of inference? Proofs? Why? A contract
does not argue.

Automatic quantifiers are obviously present when A and B
are parameters, and they are of a MUST kind if the programmer
doesn't reduce them in rank to SHALL or MAY by controlling
checking, say.

  function ... (A, B: T) return ...
   with
    Pre => A > B;

Pre is meant to hold for *any* pair of values A and B, to be
passed to the function. So the programmer can infer a universal
requirement.

It is of no concern how any tool or any programmer arrives
at Pre. If he arrives at Pre => True, then this can be
well-reasoned. Does the client programmer care?