# Re: [PHP] Whacky increment/assignment logic with \$foo++ vs ++\$foo

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________________________________
From: tedd <tedd.sperl...@gmail.com>
To: php-general@lists.php.net; a...@ashleysheridan.co.uk; Daevid Vincent
<dae...@daevid.com>
Sent: Wed, October 7, 2009 12:42:41 PM
Subject: RE: [PHP] Whacky increment/assignment logic with \$foo++ vs ++\$foo

At 1:59 PM +0100 10/7/09, Ashley Sheridan wrote:
>>On Wed, 2009-10-07 at 08:54 -0400, tedd wrote:
>>At 6:15 PM -0700 10/6/09, Daevid Vincent wrote:
>>>Except that:
>>>
>>>\$a = 123;
>>>\$b = \$a++;
>>>echo \$b;  //gives 123, not 124
>>>
>>>as you logically expect it to and common sense would dictate, regardless of
>>>what K&R or anyone else says.
>>
>>That's not the way I look at it.
>>
>>     \$b = \$a++;
>>
>>means to me "take the value of \$a and assign to \$b and then increment \$a."
>>
>>Whereas:
>>
>>     \$b = ++\$a;
>>
>>means to me "increment \$a and take the value of \$a and assign to \$b."
>>
>>Cheers,
>>
>>tedd
>>
>>
>
>Which is exactly the reason for the two operators in C.
>
>Thanks,
>Ash

Ash:

The reason was simply to provide a different way of doing something.
For example, take the statements of:

\$a = 10;
\$b = a\$++;  // \$b = 10 and \$a = 11

This post-increment operator was a way to assign 10 to \$b and
increment \$a in one statement.

Whereas:

\$a = 10;
\$b = ++a\$;    // \$b = 11 and \$a = 11

This pre-increment operator was a way to increment \$a and also assign
that value to \$b.

Both are perfectly valid ways of using the operator. Also realize
that the pre-decrement and post-decrement operators worked in similar
fashion.

Now why would someone want to do that? There could be many reasons,
but that was left to the programmer to use as he/she needed.

However, what I find wacky about all of this is:

for(\$i=1; \$i<=10; \$i++)
{
echo(\$i);
}

and

for(\$i=1; \$i<=10; ++\$i)
{
echo(\$i);
}

Do exactly the same thing. I would have expected the first to print
1-10, while the second to print 2-10, but they both print 1-10.

Cheers,

tedd

Tommy>> Why would expect to print 2-10?  The way I read the for loop is:  start
\$i with 1, do loop body until \$i <= 10, increment \$i  before next loop.  So
whether post/pre-increment doesn't matter logically.  Moreover,  your loop can
also be written as:

for (\$i=1; \$i <= 10;)
{
echo (\$i++);
}

PS:  I hate to send reply in 'rich text' but Yahoo's plain text screw up the
quote...  I think it's time to switch over to gmail...

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