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Re: simple session question [message #175745 is a reply to message #175741]

Sun, 23 October 2011 03:03

Jerry Stuckle
Messages: 2598
Registered: September 2010

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Senior Member

On 10/22/2011 8:12 PM, Thomas Mlynarczyk wrote:
> Richard Damon schrieb:
>
>> I suspect that there is a difference between the execution model of
>> C/C++ and PHP here, do in part to the fact that C/C++ is (normally) a
>> compiled language with the goal of allowing the compiler to generate
>> as efficient of code as possible, while PHP is designed as a
>> interpreted language.
>
> Hm. But PHP is written in C, so I would assume it to just follow C here.
>
>> x = x; /* perform the = */
>> x = x+1; /* perform the ++ */
>
> That could be further optimized by dropping the x = x. But here the
> assignment seems to have a higher precedence than the increment.
>
>> temp = x;
>> x = x+1;
>> ... do what ever with temp
>>
>> Which being an interpreted language makes some sense, why put off
>> doing something, and recording somewhere that you need to do it, when
>> you can do it now, the possible savings that C might have been able to
>> make, get swamped by the other overhead in PHP.
>
> Now I wonder why x = x++ is undefined in C. If it was defined to be a no
> op as it behaves in PHP, then it could be optimized away completely.
>
> Greetings,
> Thomas
>

Because it's not a noop. The language only defined the order of
operator evaluation - not operand evaluation. Some C compilers will
return 0, others will return 1.

The problem here is you are setting the value in the operand ($!foo)
twice in the same expression. Results of such operations is always
undefined in C.

--
==================
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================

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[Message index]

		simple session question By: cerr on Fri, 21 October 2011 17:44
		Re: simple session question By: Thomas Mlynarczyk on Fri, 21 October 2011 18:19
		Re: simple session question By: Jonathan Stein on Fri, 21 October 2011 18:51
		Re: simple session question By: Thomas Mlynarczyk on Fri, 21 October 2011 20:00
		Re: simple session question By: Jerry Stuckle on Fri, 21 October 2011 20:14
		Re: simple session question By: Thomas Mlynarczyk on Fri, 21 October 2011 22:50
		Re: simple session question By: Jerry Stuckle on Fri, 21 October 2011 23:05
		Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 13:40
		Re: simple session question By: Richard Damon on Sat, 22 October 2011 21:19
		Re: simple session question By: The Natural Philosoph on Sat, 22 October 2011 21:56
		Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 22:35
		Re: simple session question By: Tim Streater on Sat, 22 October 2011 22:43
		Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 23:56
		Re: simple session question By: Richard Damon on Sat, 22 October 2011 23:29
		Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 23:54
		Re: simple session question By: Thomas Mlynarczyk on Sun, 23 October 2011 00:12
		Re: simple session question By: Richard Damon on Sun, 23 October 2011 01:13
		Re: simple session question By: The Natural Philosoph on Sun, 23 October 2011 07:44
		Re: simple session question By: Thomas Mlynarczyk on Sun, 23 October 2011 15:31
		Re: simple session question By: The Natural Philosoph on Sun, 23 October 2011 16:18
		Re: simple session question By: Thomas Mlynarczyk on Sun, 23 October 2011 17:14
		Re: simple session question By: The Natural Philosoph on Sun, 23 October 2011 17:16
		Re: simple session question By: Thomas Mlynarczyk on Sun, 23 October 2011 17:00
		Re: simple session question By: Richard Damon on Sun, 23 October 2011 19:28
		Re: simple session question By: Jerry Stuckle on Sun, 23 October 2011 03:03
		Re: simple session question By: Thomas Mlynarczyk on Sun, 23 October 2011 17:06
		Re: simple session question By: Jerry Stuckle on Sun, 23 October 2011 18:35
		Re: simple session question By: The Natural Philosoph on Fri, 21 October 2011 23:32
		Re: simple session question By: Luuk on Sat, 22 October 2011 10:01
		Re: simple session question By: The Natural Philosoph on Sat, 22 October 2011 14:27
		Re: simple session question By: The Natural Philosoph on Sat, 22 October 2011 14:37
		Re: simple session question By: Luuk on Sat, 22 October 2011 15:08
		OT: and even in Dart .........Re: simple session question By: Luuk on Sat, 22 October 2011 15:17
		Re: OT: and even in Dart .........Re: simple session question By: The Natural Philosoph on Sat, 22 October 2011 15:54
		Re: OT: and even in Dart .........Re: simple session question By: Luuk on Sat, 22 October 2011 16:47
		Re: OT: and even in Dart .........Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 17:34
		Re: OT: and even in Dart .........Re: simple session question By: Norman Peelman on Sat, 22 October 2011 20:08
		Re: OT: and even in Dart .........Re: simple session question By: Jerry Stuckle on Sat, 22 October 2011 20:28
		Re: OT: and even in Dart .........Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 23:39
		Re: OT: and even in Dart .........Re: simple session question By: Norman Peelman on Sun, 23 October 2011 02:40
		Re: OT: and even in Dart .........Re: simple session question By: Jerry Stuckle on Sun, 23 October 2011 03:05
		Re: OT: and even in Dart .........Re: simple session question By: The Natural Philosoph on Sat, 22 October 2011 21:52
		Re: OT: and even in Dart .........Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 23:25
		Re: OT: and even in Dart .........Re: simple session question By: The Natural Philosoph on Sun, 23 October 2011 07:41
		Re: OT: and even in Dart .........Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 22:56
		Re: OT: and even in Dart .........Re: simple session question By: Norman Peelman on Sun, 23 October 2011 02:52
		Re: OT: and even in Dart .........Re: simple session question By: Thomas Mlynarczyk on Sun, 23 October 2011 15:12
		Re: OT: and even in Dart .........Re: simple session question By: Tim Streater on Sun, 23 October 2011 08:39
		Re: OT: and even in Dart .........Re: simple session question By: The Natural Philosoph on Sun, 23 October 2011 08:40
		Re: OT: and even in Dart .........Re: simple session question By: Tim Streater on Sun, 23 October 2011 08:43
		Re: OT: and even in Dart .........Re: simple session question By: Peter H. Coffin on Sat, 05 November 2011 20:04
		Re: OT: and even in Dart .........Re: simple session question By: The Natural Philosoph on Sat, 22 October 2011 21:47
		Re: OT: and even in Dart .........Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 23:22
		Re: OT: and even in Dart .........Re: simple session question By: The Natural Philosoph on Sun, 23 October 2011 07:40
		Re: OT: and even in Dart .........Re: simple session question By: Thomas Mlynarczyk on Sun, 23 October 2011 15:04
		Re: OT: and even in Dart .........Re: simple session question By: Peter H. Coffin on Sat, 05 November 2011 20:00
		Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 13:39
		Re: simple session question By: cerr on Fri, 21 October 2011 21:43
		Re: simple session question By: Thomas Mlynarczyk on Fri, 21 October 2011 22:47
		Re: simple session question By: Jerry Stuckle on Fri, 21 October 2011 23:06
		Re: simple session question By: cerr on Fri, 21 October 2011 21:17
		Re: simple session question By: Thomas Mlynarczyk on Sat, 22 October 2011 13:50
		Re: simple session question By: Denis McMahon on Sun, 23 October 2011 15:47

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