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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: class wide iterable (and indexable)
Date: Fri, 18 Jan 2019 17:54:43 +0100
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Xref: reader01.eternal-september.org comp.lang.ada:55309
Date: 2019-01-18T17:54:43+01:00
List-Id: <comp.lang.ada>

On 2019-01-18 17:29, Olivier Henley wrote:
>> Array interface is not separated from implementation/representation. The
>> problems with String encoding is a consequence of. You cannot have
>> differently encoded Strings with the same interface. You cannot have two
>> array interfaces for the same String (array of characters vs. array of
>> encoding units, e.g. of code points).
> 
> Ok but is it not the intended purpose of an 'array' to be/stay a 'primitive memory mapping construct'?

That is a purpose of a builtin array, a building block of user types 
implementation. *If* a builtin array is all the user needs, fine. That 
is 80% of the cases. But the example of containers represent multiple 
cases when just primitive memory mapping is not enough. Concurrently 
accessed arrays is another example. Externally kept arrays, e.g. 
interfacing other language, DB, network etc is yet another example.

The same applies to record types, access types, enumeration types, 
numeric types, subroutine types, task types, protected types. Each one 
must have an interface which can be used together with a custom 
implementation or the builtin implementation.

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