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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Copying rows in a two dimensional array.
Date: Mon, 1 Feb 2010 18:11:37 -0600
Organization: Jacob Sparre Andersen
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Date: 2010-02-01T18:11:37-06:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:178rg3rch8qdu$.13cgkywb09x3p.dlg@40tude.net...
> On Sun, 31 Jan 2010 21:11:12 -0500, Peter C. Chapin wrote:
>
>> So I thought, "Perhaps A needs to be an array of arrays."
>>
>> type Matrix is array(Positive range <>) of WHAT_EXACTLY?
>>
>> Apparently the component type of an array needs to be fully constrained 
>> (which
>> again makes sense)
>
> Not really. Arrays should have been allowed to have discriminants. That 
> was
> missed in the language design.

Early Ada 9x had discriminants for arrays. The capability got dropped when 
lots of "nice-to-have" features got dropped from Ada 95. Such "array" types 
have to be implemented as discriminant dependent records anyway; there is no 
real hope of performance improvement from them, but a lot of implementation 
complication. (I recall I was one of the stronger opponents of this feature, 
mostly for implementation cost/benefit reasons.)

So it is completely wrong to say that "this was missed in the language 
design". The correct statement is that "this was explicitly rejected in the 
language design".

                                 Randy.