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From: 18k11tm001@sneakemail.com (Russ)
Newsgroups: comp.lang.ada
Subject: Re: += in ada
Date: 16 Oct 2003 14:53:34 -0700
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Date: 2003-10-16T14:53:34-07:00
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"Mark A. Biggar" <mark@biggar.org> wrote in message news:<w%yjb.783830$YN5.775353@sccrnsc01>...
> Hyman Rosen wrote:
> 
> > Lutz Donnerhacke wrote:
> > 
> >> * Russ wrote:
> >>
> >>> Actually, a competent programmer will define the "+" operator in terms
> >>> of the ":+" operator rather than vice versa, because the ":+" is
> >>> usually more efficient (since it has no need for temporaries and extra
> >>> copying).
> >>
> >>
> >> Wrong.
> > 
> > 
> > That's certainly the way it's usually done in C++,
> > for exactly the reason stated, so a bald "wrong" is
> > not terribly enlightening.
> > 
> 
> Okay, show how to define "+" in terms of "+=" with out explicitly
> reintroducing the temp variable you were so hot to eliminate?

When you define "+" in terms of "+=" you reintroduce the temp, of
course. The point is that you then have the option of using "+=",
which is more efficient, or "+", which is a bit more elegant. Also,
"+" can be "cascaded", as in "A = B + C + D", but "+=" cannot (you
need A=B; A+=C; A+=D).