Re: OT: and even in Dart .........Re: simple session question

From	Norman Peelman <npeelmandog@cfl.rr.com>
Newsgroups	comp.lang.php
Subject	Re: OT: and even in Dart .........Re: simple session question
Date	2011-10-22 22:40 -0400
Organization	A noiseless patient Spider
Message-ID	<j7vurf$13h$1@dont-email.me> (permalink)
References	(12 earlier) <j7uov3$d1o$1@news.albasani.net> <il8bn8-po9.ln1@luuk.invalid.lan> <j7uusi$qlu$1@news.albasani.net> <j7v7r2$v78$1@dont-email.me> <j7v911$6oc$1@dont-email.me>

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On 10/22/2011 04:28 PM, Jerry Stuckle wrote:
> On 10/22/2011 4:08 PM, Norman Peelman wrote:
>> On 10/22/2011 01:34 PM, Thomas Mlynarczyk wrote:
>>> Luuk schrieb:
>>>> i did send a bug-report:
>>>> https://bugs.php.net/bug.php?id=60114
>>>
>>> I do not see any bug here. I was confused because it's a crappy way to
>>> code, but it's clear why it works the way it does:
>>>
>>> $foo = 0;
>>> $foo = $foo++;
>>>
>>> is definitely identical to
>>>
>>> $foo = 0;
>>> $foo = ($foo++);
>>>
>>> since ++ has higher precedence than =. In fact, ($foo = $foo)++ does
>>> rightfully throw a parse error, since you can only increment a variable,
>>> not an expression.
>>>
>>> As mentioned before in this thread, the above code is equivalent to
>>>
>>> $foo = 0;
>>> $tmp = $foo; // $foo++ yields the previous value, which is 0
>>> $foo = $foo + 1; // then $foo is incremented...
>>> $foo = $tmp; // ...and then re-assigned the old value
>>>
>>> It's the exact same procedure as it would be with $foo = $bar++.
>>>
>>> Greetings,
>>> Thomas
>>>
>>
>> No they are not the same.
>>
>> $foo = 0;
>> $foo = $foo++;
>>
>> It should be equivalent to:
>>
>> $foo = 0; // 0
>> $foo = $foo; // 0 = 0
>> $foo = $foo + 1; // 0 = (0 + 1)
>>
>> $foo++ means that the variable is to be incremented after the variable
>> is accessed. Something is clobbering that increment.
>>
>> ++$foo means that the variable is to be incremented piror to the
>> variable being accessed. Works as expected.
>>
>>
>> Haven't seen the source code but there must be some temporary variable
>> that's getting clobbered for the $foo++ example.
>>
>>
>
> Actually, I take my previous statement about the behavior being defined
> back. Officially in C/C++, the results of this operation is undefined.
>
> Precedence and associativity define the order in which operators are
> processed. But the order of operand processing is not defined.
>
> For
>
> $foo = $foo++;
>
> we have the same operand ($foo) being set twice. The $foo++ will return
> 0, and this value will be assigned into $foo.
>
> But what is NOT defined is whether the assignment will occur before or
> after the value of $foo is actually incremented. Either is possible.
>
> Now in the case of
>
> $foo = ($foo++);
>
> The results are different, but they are still undefined.
>
> In the first case the increment is obviously performed before the
> assignment (although the assignment correctly uses the pre-increment
> value).
>
> In the second case it looks like the assignment is still using the
> pre-increment value, but the increment is done after the assignment.
>
> Since the results are undefined, both are correct (or incorrect, as you
> may look at it), and may change with changes to the interpreter (or
> potentially the same version on different OS's).
>

   The problem seems to be that the post increment is being overwritten 
as if:

$foo = 0;
$tmp = $foo;
$foo = $foo + 1;
$foo = $tmp;

Which I think someone else may have said.

-- 
Norman
Registered Linux user #461062
-Have you been to www.php.net yet?-

Thread

simple session question cerr <ron.eggler@gmail.com> - 2011-10-21 10:44 -0700
  Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-21 20:19 +0200
    Re: simple session question Jonathan Stein <jstein@image.dk> - 2011-10-21 20:51 +0200
      Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-21 22:00 +0200
        Re: simple session question Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-21 16:14 -0400
          Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-22 00:50 +0200
            Re: simple session question Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-21 19:05 -0400
              Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-22 15:40 +0200
                Re: simple session question Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-22 17:19 -0400
                Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-22 22:56 +0100
                Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 00:35 +0200
                Re: simple session question Tim Streater <timstreater@greenbee.net> - 2011-10-22 23:43 +0100
                Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 01:56 +0200
                Re: simple session question Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-22 19:29 -0400
                Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 01:54 +0200
                Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 02:12 +0200
                Re: simple session question Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-22 21:13 -0400
                Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-23 08:44 +0100
                Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 17:31 +0200
                Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-23 17:18 +0100
                Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 19:14 +0200
                Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-23 18:16 +0100
                Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 19:00 +0200
                Re: simple session question Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-23 15:28 -0400
                Re: simple session question Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-22 23:03 -0400
                Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 19:06 +0200
                Re: simple session question Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-23 14:35 -0400
            Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-22 00:32 +0100
              Re: simple session question Luuk <Luuk@invalid.lan> - 2011-10-22 12:01 +0200
                Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-22 15:27 +0100
                Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-22 15:37 +0100
                Re: simple session question Luuk <Luuk@invalid.lan> - 2011-10-22 17:08 +0200
                OT: and even in Dart .........Re: simple session question Luuk <Luuk@invalid.lan> - 2011-10-22 17:17 +0200
                Re: OT: and even in Dart .........Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-22 16:54 +0100
                Re: OT: and even in Dart .........Re: simple session question Luuk <Luuk@invalid.lan> - 2011-10-22 18:47 +0200
                Re: OT: and even in Dart .........Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-22 19:34 +0200
                Re: OT: and even in Dart .........Re: simple session question Norman Peelman <npeelmandog@cfl.rr.com> - 2011-10-22 16:08 -0400
                Re: OT: and even in Dart .........Re: simple session question Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-22 16:28 -0400
                Re: OT: and even in Dart .........Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 01:39 +0200
                Re: OT: and even in Dart .........Re: simple session question Norman Peelman <npeelmandog@cfl.rr.com> - 2011-10-22 22:40 -0400
                Re: OT: and even in Dart .........Re: simple session question Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-22 23:05 -0400
                Re: OT: and even in Dart .........Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-22 22:52 +0100
                Re: OT: and even in Dart .........Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 01:25 +0200
                Re: OT: and even in Dart .........Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-23 08:41 +0100
                Re: OT: and even in Dart .........Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 00:56 +0200
                Re: OT: and even in Dart .........Re: simple session question Norman Peelman <npeelmandog@cfl.rr.com> - 2011-10-22 22:52 -0400
                Re: OT: and even in Dart .........Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 17:12 +0200
                Re: OT: and even in Dart .........Re: simple session question Tim Streater <timstreater@greenbee.net> - 2011-10-23 09:39 +0100
                Re: OT: and even in Dart .........Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-23 09:40 +0100
                Re: OT: and even in Dart .........Re: simple session question Tim Streater <timstreater@greenbee.net> - 2011-10-23 09:43 +0100
                Re: OT: and even in Dart .........Re: simple session question "Peter H. Coffin" <hellsop@ninehells.com> - 2011-11-05 15:04 -0500
                Re: OT: and even in Dart .........Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-22 22:47 +0100
                Re: OT: and even in Dart .........Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 01:22 +0200
                Re: OT: and even in Dart .........Re: simple session question The Natural Philosopher <tnp@invalid.invalid> - 2011-10-23 08:40 +0100
                Re: OT: and even in Dart .........Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-23 17:04 +0200
                Re: OT: and even in Dart .........Re: simple session question "Peter H. Coffin" <hellsop@ninehells.com> - 2011-11-05 15:00 -0500
              Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-22 15:39 +0200
    Re: simple session question cerr <ron.eggler@gmail.com> - 2011-10-21 14:43 -0700
      Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-22 00:47 +0200
      Re: simple session question Jerry Stuckle <jstucklex@attglobal.net> - 2011-10-21 19:06 -0400
    Re: simple session question cerr <ron.eggler@gmail.com> - 2011-10-21 14:17 -0700
      Re: simple session question Thomas Mlynarczyk <thomas@mlynarczyk-webdesign.de> - 2011-10-22 15:50 +0200
    Re: simple session question Denis McMahon <denismfmcmahon@gmail.com> - 2011-10-23 15:47 +0000

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