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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Extend slices for n dimensional arrays for Ada 202X
Date: Fri, 27 Jan 2017 17:37:33 -0600
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Date: 2017-01-27T17:37:33-06:00
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"G.B." <bauhaus@notmyhomepage.invalid> wrote in message 
news:o6fja1$vq8$1@dont-email.me...
> On 27.01.17 10:34, Dmitry A. Kazakov wrote:
>> On 26/01/2017 19:29, Randy Brukardt wrote:
>>
>>> So I don't see this happening - it doesn't make sense in the context of 
>>> Ada
>>> implementation strategies.
>>
>> That is why I keep on saying, give users the array interface (and the 
>> array slice interface)
>> and let users implement their custom arrays.
>>
>
> Will some Iterator_Interface and generalized
> loop iteration not provide for custom arrays?

...and generalized indexing.

But those features don't have an provision for slices, and I don't see any 
way that they could be usefully extended to give slices. I tried a few years 
ago to come up with a Root_String_Class, which mostly would work well, but 
it gets ugly when dealing with slices and string literals. You can make 
something that works like a slice, but assigning into them or passing them 
as parameters would always require copies. Whether that's acceptable would 
depend on the application. (It doesn't seem to be a general solution.)

I'm unconvinced that Dmitry's array interfaces would have been any better: 
general slices really don't fit very well into any type model since they're 
a different shape (in general) than the originating array type.

                                      Randy.