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From: "Peter H. Coffin" <hellsop@ninehells.com>
Newsgroups: comp.lang.php
Subject: Re: OT: and even in Dart .........Re: simple session question
Date: Sat, 5 Nov 2011 15:00:13 -0500
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On Sat, 22 Oct 2011 16:54:11 +0100, The Natural Philosopher wrote:
> Luuk wrote:
>> On 22-10-2011 17:08, Luuk wrote:
>>> On 22-10-2011 16:37, The Natural Philosopher wrote:
>>>> The Natural Philosopher wrote:
>>>>> Luuk wrote:
>>>>>> On 22-10-2011 01:32, The Natural Philosopher wrote:
>>>>>>> try $foo=($foo++);
>>>>>>>
>>>>>>> But actually, why not just
>>>>>>>
>>>>>>> $foo+=1;
>>>>>>
>>>>>> Because they differ?
>>>>>>
>>>>>> $ php -r ' $foo=0; $foo=$foo++; print $foo."\n";'
>>>>>> 0
>>>>>> $ php -r ' $foo=0; $foo=($foo++); print $foo."\n";'
>>>>>> 0
>>>>>
>>>>> That is surely a bug..
>>>>>
>>>>
>>>> viz
>>>>
>>>> ~$ cat test.c
>>>> #include <stdio.h>
>>>> main()
>>>> {
>>>> int foo;
>>>> foo=0;
>>>> foo=(foo++);
>>>> printf("%d\n",foo);
>>>> }
>>>> ~$ ./test
>>>> 1
>>>>
>>>>
>>>> I thought PHP followed C operator precedence exactly..
>>>>
>>>>
>>>
>>> it seems to follow PERL
>>>
>>> $ perl -e '$foo=0; $foo=$foo++; print $foo."\n";'
>>> 0
>>> $ perl -e '$foo=0; $foo=($foo++); print $foo."\n";'
>>> 0
>>> $ perl -e '$foo=0; $foo++; print $foo."\n";'
>>> 1
>>> $
>>>
>>>
>> 
>> see: http://www.dartlang.org
>> 
>> main() {
>>   int foo=0;
>>   foo=foo++;
>>   print('First test: ${foo}');
>> 
>>   foo=0;
>>   foo=(foo++);
>>   print('Second test: ${foo}');
>> 
>>   foo=0;
>>   foo++;
>>   print('Third test: ${foo}');
>> 
>> }
>> 
>> which gives:
>> First test: 0
>> Second test: 0
>> Third test: 1
>> 
>> 
>
> still a bug in PHP where
>
> "Parentheses may be used to force precedence, if necessary. For 
> instance: (1 + 5) * 3 evaluates to 18"
>
> (from the manual)
>
> I THOUGHT the general rule was that the value of (entity) was always the 
> FINAL value after ALL internal operations had been carried out.
>
> Agreed its a crappy way to code, which is probably why no one has 
> noticed it.

The thing is that PHP is doing the right thing there. Remember that 

$foo++

is not the same as 

++$foo

The former "returns" the value PRIOR to incrementing, the latter AFTER
incrementing. Even wrapping $foo++ in parens won't change what it
returns. Don't use one when you want the other.

-- 
93. If I decide to hold a double execution of the hero and an underling
    who failed or betrayed me, I will see to it that the hero is 
    scheduled to go first.
	--Peter Anspach's list of things to do as an Evil Overlord