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Date: Wed, 13 Aug 2014 22:25:33 +0300
Message-ID: <CAPhkiZxW63SzUYKykBmXN+qfBO_PJkorPYpUpD_X53A0mP9m0A@mail.gmail.com>
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: internals@lists.php.net, Andrea Faulds <ajf@ajf.me>, 
	"guilhermeblanco@gmail.com" <guilhermeblanco@gmail.com>
Content-Type: multipart/alternative; boundary=047d7b45102c78ecee050087c01a
Subject: Re: [PHP-DEV] [RFC] Introduce Abstract Syntax Tree
From: narf@devilix.net (Andrey Andreev)

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Hi,

I'd personally find it horrible if $foo[$i] = $bar[$i++]; is executed
right-to-left, but given that your examples are a bit weird, I'm not sure
if mine is affected. Is it?

Cheers,
Andrey.

On Aug 13, 2014 10:05 PM, "Nikita Popov" <nikita.ppv@gmail.com> wrote:
>
> On Wed, Aug 13, 2014 at 7:18 PM, guilhermeblanco@gmail.com <
> guilhermeblanco@gmail.com> wrote:
>
> > When is this planned to go through voting process?
> >
>
> Before voting I'd like to have some opinions on the behavioral differences
> the proposal introduces. In particular I'd like to know whether we are
okay
> with changing order of evaluation in some places. We document that
> evaluation order is undefined, we document that it can change without
> warning between versions and that it is inconsistent within one version.
> However in the current implementation evaluation is usually left-to-right.
> The AST implementation introduces some places where evaluation is
> explicitly right-to-left, and not just incidentally.
>
> So basically the question is whether we are committed to things like
> $a[$i++] = $i++ or $a[$i++][$i++] = $j being undefined behavior, in which
> case order doesn't matter. If not, I can preserve left-to-right behavior
> here (CVs notwithstanding of course), but it would come at the cost of a
> good bit of additional complexity in the implementation (I suspect that
I'd
> have to reintroduce parts of the bp stack to properly shuffle the oplines
> around).
>
> My personal opinion is that things like $a[$i++] = $i++ have zero
practical
> relevance (and also think that anyone using something like this deserves
> any breakage he gets). I'd rather save some lines of code than maintain
any
> behavior guarantees for that. But some people have contrary opinions on
> this, so I'm bringing up the point for discussion.
>
> Nikita

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