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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Array conversion and bounds
Date: Sun, 15 Apr 2018 14:34:42 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:51510
Date: 2018-04-15T14:34:42+02:00
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On 2018-04-15 12:37, Niklas Holsti wrote:
> On 18-04-15 12:36 , Dmitry A. Kazakov wrote:
>> Do array bounds slide during conversion? Consider this:
>>
>>    type A is array (Integer range <>) of Whatever;
>>    type B is array (Unsigned_32 range <>) of Whatever;
>>
>>    X : A (-10..-1);
>>    Y : B (1..10);
>> begin
>>    Y := B (X); -- Is this OK?
>>
>> If bounds slide it must be OK, if bounds do not slide, it must raise
>> Constraint_Error.
>>
>> Any language lawyers?
> 
> I believe the bounds should _not_ slide, because the "target subtype" of 
> the conversion is type B, which is an _unconstrained_ array subtype.

Better to say, they should, but they do not. Clearly conversions like 
this should not require resorting to Unchecked_Conversion.

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