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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Ada 2012 Constraints (WRT an Ada IR)
Date: Wed, 21 Dec 2016 22:15:31 +0100
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Date: 2016-12-21T22:15:31+01:00
List-Id: <comp.lang.ada>

On 2016-12-21 19:26, G.B. wrote:
> On 21/12/2016 16:56, Dmitry A. Kazakov wrote:
>
>> It is a continuous subset. This preserves a lot of properties like
>> being a convex set a,b in S => (a+b)/2 in S etc.
>
> The subtype in question seems to be this:
>
>    subtype Z_Too is
>      X range X'Range  -- 1 .. 100
>    with Static_Predicate => Z_Too > 0;
>
> I see no breaks there.

It is for the compiler to see breaks, which it cannot. There is a far 
better and safer model to produce user-defined subtypes that this mess.

>> That would produce non-sets.
>
> At compile time? Otherwise, how can a specification of membership by
> any Boolean function "produce" anything but that decision, if it does
> compute a result?

When predicate is not a complete function of the argument, e.g.

    P (x) = (Integer (Clock - Epoch) mod 2) = 1

> Also, how can one predict, from a SW design POV or
> otherwise,  that those "run-time sets" of subtypes do not reflect what
> the engineers had been carefully designing, and documenting that way?

Easy. Anything contradicting results of more general frameworks, like 
logic, mathematics etc is not even considered. Engineers insisting that 
2+2=5 or doing things because the spirit of Napoleon told them so are to 
be fired and probably sent to medical examination.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de