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From: Lutz Donnerhacke <lutz@iks-jena.de>
Newsgroups: comp.lang.ada
Subject: Re: += in ada
Date: Thu, 16 Oct 2003 12:45:04 +0000 (UTC)
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* Russ wrote:
> Consider the common operation of scaling a vector, for example. I
> could write
>
>    vec := vec * factor
> or
>    vec :* factor
>
> The first form requires the construction of a temporary, the actual
> scaling operation, then the copying back of the temporary to the
> original vector. The latter, on the other hand, can be written to
> avoid the construction of the temp and the copying back.

Wrong! In the case of an exception, the original values need to be retained
in order to keep in touch with the current Ada feelings. So any 'idem'
notation or 'augmented assignment' requires a temporary copy as strong than
the original form.