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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Your wish list for Ada 202X
Date: Tue, 8 Apr 2014 12:56:44 +0200
Organization: cbb software GmbH
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Xref: number.nntp.dca.giganews.com comp.lang.ada:185628
Date: 2014-04-08T12:56:44+02:00
List-Id: <comp.lang.ada>

On Tue, 08 Apr 2014 12:15:45 +0200, G.B. wrote:

> On 08.04.14 11:15, Dmitry A. Kazakov wrote:
>>> Constrained types*are*  useless -- Ada has no such thing. It only has
>>> >unconstrained types (remember that names only apply to subtypes). And in
>>> >particular, a constrained class-wide type is an evil thing, because it's
>>> >mixing things that should not be mixed: relaxing and tightening constraints
>>> >at the same time.
>> OK, constraining is useless, discriminants are evil, specific instances of
>> classes are wrong. We have to agree to disagree.
> 
> Reminder: an Ada "type", formally, is different from the "type"
> that Dmitry has in mind (seeing subtype constraints as
> establishing a "type", IIRC, which, for the most part, it isn't
> doing, in Ada).
> 
> It might help to have a USENET specific type of link
> that establishes evidence of the difference in terminology.

Can be found in any textbook:

    type is a set of values bound by operations defined on these values

Yes, Ada's subtype is a type, no less than C++'s class is.

But however you call it, Randy's point was about putting a constraint on
some set of values being useless. I can guess that his position is
motivated by the ideas of LSP subtyping. Surely Ada's subtyping is in
contradiction with LSP-subtyping. That does not make Ada's subtyping any
useless or evil. On the contrary, it rather does the LSP-subtyping.

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