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Date: Thu, 06 Nov 2003 19:22:39 -0500
From: "Robert I. Eachus" <rieachus@comcast.net>
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Subject: Re: Clause "with and use"
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Date: 2003-11-06T19:22:39-05:00
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Martin Dowie wrote:

> So, Russ, have read AI-318? Do you still think that "+=",etc is
> still necessary, now there is a mechanism to avoid that extra deep
> copy for things like matrices/vectors?

For the record, AI-318 as written applies to limited and unlimited 
types.  But the current ARG discussion has determined that there are 
significant implementation problems with requiring this feature to be 
used with non-limited return types.  I don't know what the final 
resolution will be.  It could either allow implementations to do the 
"extra" copy when the type is non-limited, or involve a notation that 
made it clear in the subprogram declaration that this style of return is 
being used.

Sorry this is one of those cases where the ARG has to be concerned about 
the "real" issues of language maintenance.  (The final resolution might 
be to permit the notation for all cases, and require the "generate 
return value in place" behaviour for limited types only.  That way a 
compiler could do the optimization if it can tell at the point of any 
calls that the function body is written this way.)

-- 
                                           Robert I. Eachus

100% Ada, no bugs--the only way to create software.