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Date: Fri, 25 Jul 2014 18:33:33 -0700 (PDT)
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Subject: Re: Effective use of derived types
From: "Dan'l Miller" <optikos@verizon.net>
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Xref: number.nntp.dca.giganews.com comp.lang.ada:187882
Date: 2014-07-25T18:33:33-07:00
List-Id: <comp.lang.ada>

On Friday, July 25, 2014 2:33:15 PM UTC-5, Dmitry A. Kazakov wrote:
> On Fri, 25 Jul 2014 11:40:58 -0700 (PDT), Dan'l Miller wrote:
> > I say of course URI should be a subtype of string in Ada2012 so that it
> > can Dynamic_Predicate post-conditions that enforce the regular expressi=
on
> > that URIs must obey.
>=20
> I doubt that were realistic. In any case the amount of work required to
> design such a predicate would be far bigger than in the case of a proper
> type. Usefulness would be near to zero.

The Dynamic_Predicate could raise an exception for a URI string (e.g., a UR=
L_string) that does not conform to the regular expression that all supporte=
d URIs (e.g., URLs) are required to obey.  Or are raising exceptions in Dmi=
try's same Bucket-of-Uselessness* as finite-state machines?

* some of which, other programmers find to be actually useful

> It is like designing a predicate
> that yields true of the string contains a valid Ada program...

mere hyperbole that does not answer Victor's question