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From: Warren <ve3wwg@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Inferring array index type from array object
Date: Wed, 23 Jun 2010 16:33:43 +0000 (UTC)
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Date: 2010-06-23T16:33:43+00:00
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Niklas Holsti expounded in news:88ec2vF3uqU1@mid.individual.net:
> Dmitry A. Kazakov wrote:
>> On Wed, 23 Jun 2010 00:30:23 -0700 (PDT), Maciej Sobczak wrote:
..
>>> 2. Is it possible to declare the index variable without hardcoding
>>> the index type (that is, to infer it from the array object)?
>> 
>> No, without improving the type system. E.g. introducing abstract
>> index types, and abstract range types (or more general sets of index
>> types), and abstract composite types like arrays.
> 
> I don't think such large language changes would be necessary. The 
> expression S'Range gives the compiler all the information about the
> type and its constraints, so I see no reason why Ada could not be
> extended simply to allow S'Range in a variable declaration, as in the
> above quoted "I : S'Range". The declared variable "I" would have the
> same (sub)type as the loop counter in "for I in S'Range loop ...".

I think most would agree that this is a "convenience" feature.
I think the language (and its compiler) is probably complicated
enough for these types of additions. Don't forget each new feature
requires a "test suite" and validation, in addition to the 
compiler itself.

Warren