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From: 18k11tm001@sneakemail.com (Russ)
Newsgroups: comp.lang.ada
Subject: Re: += in ada
Date: 21 Oct 2003 00:43:54 -0700
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"Robert I. Eachus" <rieachus@comcast.net> wrote in message news:<3F937806.9080205@comcast.net>...
> I had about decided to let this topic die a graceful death when Chad R. 
> Meiners wrote:
> 
> > People that use Ada are people that feel safety and maintenance are
> > important characteristics of a programming language.
> 
> I felt this is worth repeating, if only as a epitaph to this topic. 
> This is what Russ kept not understanding.  Add clarity and readability 
> and a lot of what we used to call the -ilities, and that is the debate 
> in a nutshell.  Chad even gave a perfect riposte, to the question of 
> side effects. The statement x += y += 1; is perfectly legal C, and I'll 
> let Russ choose what is the effect, and what is the side effect.

I'll tell you exactly what the effect is: a compile error. And I must
say that I am a bit surprised that this is not obvious to you. "+="
would be a procedure, and my understanding of procedures in Ada is
that they do *not* return a value.

Let's consider either possibility for operator precedence:

    x += ( y += 1 );
or
    ( x += y ) += 1;

The first grouping will not compile because the expression in parens
returns no value. The second grouping will not compile because, as far
as I know, a procedure cannot be an lhs (because it cannot return a
reference, as in C++). Am I missing something here?