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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Will "renames" increase program size?
Date: Fri, 17 Jun 2011 08:53:21 +0200
Organization: cbb software GmbH
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Date: 2011-06-17T08:53:21+02:00
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On Thu, 16 Jun 2011 18:39:35 -0500, Randy Brukardt wrote:

>>Semantically returning result of a function is always copying because the
>>object being returned changes the scope.
> 
> "Changing scope" doesn't require a copy in either RM or some sort of outside 
> logical universe. The only thing that the "scope" of an object controls is 
> when it is finalized, and that has nothing to do with the contents (from a 
> logical perspective) of the object.

I fail to see how finalization could have nothing to do with the contents.
Finalized objects have no contents, they do not even exist.

> In further cases, Ada 
> requires that the anonymous object "mutate" into the target object with no 
> copying ("built-in-place"); this too changes scope.

Yep, "mutating", that is the term of the RM, I should have used instead of
"copying"! (:-))

So, the correct statement should have been: when the result of a function
is renamed it *mutates* into the target of renaming. Hmm, what is the RM
term for a non-existent thing?

(And some functions do not "return", they "build"!)

> The point is that copying has a visible semantic effect,

The cases under consideration are ones where copying should have no
semantic effect, e.g. parameter passing.

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