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From: 18k11tm001@sneakemail.com (Russ)
Newsgroups: comp.lang.ada
Subject: Re: += in ada
Date: 16 Oct 2003 15:07:07 -0700
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Date: 2003-10-16T15:07:07-07:00
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Lutz Donnerhacke <lutz@iks-jena.de> wrote in message news:<slrnbot4mg.nr.lutz@taranis.iks-jena.de>...
> * 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.

We've been over this ad nauseum already. One of the Ada experts
clarified it for us, and if I recall correctly, I think you are
mistaken. Actually, I think you are "Wrong!".

Also, the ":+" form is *not* an assignment statement. It is equivalent
to a procedure call. If the procedure call needs a temp, then Ada is
inherently less efficient than C++ in that regard.