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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Practicalities of Ada for app development
Date: Thu, 21 Jun 2012 13:10:23 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2012-06-21T13:10:23-05:00
List-Id: <comp.lang.ada>

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:m0g3o1rrco75$.699fudiit3dt$.dlg@40tude.net...
...
> The example was given: UTF-8 string. It shall implement the interface of 
> an
> array of Wide_Wide_Character (code points), the interface of an array of
> octets (encoding layer). Further interfaces are at your choice.

It's not hard to define a Root_String'Class in Ada 2012 that would provide 
all of the interfaces you would expect other than slicing and string 
literals. One can easily imagine extending existing capabilities to provide 
those.

The problem is that if we did that, we'd have to make new versions of every 
existing interface in the Standard (to use Root_String'Class rather than 
String). And that would cause compatibility problems with string literals 
because it wouldn't be clear which type is involved. (We can't get rid of 
the existing types, and we can't make String into a tagged type as that 
would be representation-incompatible, so it cannot be derived from 
Root_String'Class.)

That would be a problem for *any* implementation based on interfaces. I'm 
going to continue to pursue it (because the existing direction for 
internationalization is just one kludge on top of another), but there is no 
guarentee of success.

                                        Randy.