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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Examining individual bytes of an integer
Date: Mon, 15 Oct 2018 21:43:57 +0300
Organization: Tidorum Ltd
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Xref: reader02.eternal-september.org comp.lang.ada:54596
Date: 2018-10-15T21:43:57+03:00
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On 18-10-15 13:18 , AdaMagica wrote:
> Am Sonntag, 14. Oktober 2018 23:28:57 UTC+2 schrieb Niklas Holsti:
>> Not guaranteed, but implied by the "Implementation advice":
>>
>> - RM 13.3(11): X'address denotes the address of the first of the
>> storage elements allocated to X.
>>
>> - RM 13.3(14): For an array X, X'Address should point at the first
>>  component of the array [...].
>>
>> Combining those two, it seems that the first element of an array
>> should start at the first storage element (= lowest address)
>> allocated to the array.
>>
>> By reasonable induction  :-)  the second, third, etc. array
>> elements follow in increasing address order. But not _guaranteed_,
>> I agree.
>
> There is the old Dewar rule that no compiler is doing nonsense. It
> would be a very unfriendly compiler to not follow this advice.

As I remember it, Dewar's rule says that the Ada *RM* does not specify 
nonsense, meaning that if some reading of the RM seems to be nonsense, 
it is the wrong reading.

I don't remember Dewar saying anything similar about compilers.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .