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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Is this expected behavior or not
Date: Sat, 16 Mar 2013 08:41:27 +0100
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Date: 2013-03-16T08:41:27+01:00
List-Id: <comp.lang.ada>

On Fri, 15 Mar 2013 22:52:02 -0700 (PDT), Shark8 wrote:

> True; but there could be some more interesting cases, say, for Ada 2020.
> Something like:
> 
> Abstract Type UNIVERSAL_STRING(Element : UNIVERSAL_CHARACTER) is 
>     Array(Positive Range <>) of Element'Type;

That would not work. I presume that here you want to create a root type for
the class of string types and get at the members of the class (specific
types like Wide_String) using a constraint. The problem is that string
types must have different representations. The mechanism of constraining
does not support. Thus either subtypes will have same representation or you
won't have a class. Another problem is that string types must have more
than one interface to deal with UTF-8 etc. An UTF-8 string is *both* an
array of Wide_Wide_Character (= Unicode code points) and an array or
sequence of Character (octets). An UTF-16 string is an array of
Wide_Wide_Character and an array of Wide_String.
 
-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de