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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada 2012 Constraints (WRT an Ada IR)
Date: Thu, 1 Dec 2016 16:26:45 -0600
Organization: JSA Research & Innovation
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Date: 2016-12-01T16:26:45-06:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:o1oohd$13nu$1@gioia.aioe.org...
...
>On the contrary, predicates is useless and dangerous mess.

I can understand "useless" (that's an opinion I don't share, but it's fair 
to have it), and I understand "mess" (the difference between static and 
dynamic predicates shouldn't have happened; I wanted set constraints instead 
of static predicates, which would have been more consistent), but I don't 
understand dangerous. Predicates (and all contracts, for that matter) are 
designed not the affect the semantics of a program at all if they are 
removed (or "Ignored"). With the solitary exception of static predicates and 
case and loops (see "mess" above). Ergo, there can be no danger from 
including a contract; indeed, if there *is* a danger, there is a bug in 
either the implementation or the language.

Moreover, predicates are inherited in much the same way that constraints 
(and null exclusions as well, those also aren't formally constraints); 
there's little difference in the way any of these work. So it's hard to see 
why constraints would be OK and predicates would be dangerous. (It's 
actually more the other way around, since suppressing a contraint can 
actually make a program dangerous; that's not possible for a predicate.)

                                           Randy.