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Date: Tue, 11 Sep 2012 09:20:03 -0700 (PDT)
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Subject: Re: 'Size of an object
From: Micronian Coder <micronian2@gmail.com>
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Date: 2012-09-11T09:20:03-07:00
List-Id: <comp.lang.ada>

That's a good question. I would expect it to be the size of the object, whi=
ch could be anything really (8, 16, 32) and not the size of Enum'Size (ie. =
3). If I'm not mistaken, this confusion is why AdaCore implemented an Objec=
t_Size attribute which sadly didn't make it into any recent version of Ada.=
 A quick search on www.ada-auth.org turns up http://www.ada-auth.org/cgi-bi=
n/cvsweb.cgi/ais/ai-00319.txt?rev=3D1.5 , which is voted as NO ACTION. I sh=
ould read the AI discussion to see what the ARG was thinking.


On Tuesday, September 11, 2012 8:52:03 AM UTC-7, Adam Beneschan wrote:
> I had a customer ask a simple question and found that I didn't really
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> know the answer, and I'm not even sure where there is a clear answer.
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> The question has to do with X'Size where X is an object.  RM 13.3(40)
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> says this "denotes the size in bits of the representation of the
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> object".  Maybe I'm being dense, but this doesn't seem to clarify
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> things.
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> Suppose you have an enumeration type with eight literals, and no other
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> representation or aspect clauses apply to the type:
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>    type Enum is (E0, E1, E2, E3, E4, E5, E6, E7);
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> I think Enum'Size should be 3 in most or all implementations.  Now suppos=
e
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> you have a local variable of that type:
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>    procedure Proc is
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>       E : Enum;
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>    begin
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>       Put_Line (Integer'Image (E'Size));
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>    end Proc;
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> What would you expect E'Size to be, and why?  In a larger procedure,
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> what might you use 'Size on a local variable for; if you wouldn't ever
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> use it on a local variable, then what kinds of *objects* (not types or
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> subtypes) might you apply 'Size to, and what would you do with the value?
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>                         -- thanks, Adam