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Posted by Rami Elomaa on 04/12/07 14:49
Steve kirjoitti:
> "Steve" <no.one@example.com> wrote in message
> news:JgcTh.1016$AE5.731@newsfe06.lga...
> | someone asked a question in alt.php about a problem they were having with
> an
> | algorytm. it contained something to the effect of:
> |
> | $i = $i++;
> |
> | some example code they'd snatched somewhere. in a loop, the expected $i to
> | increment. i explained why i thought it would not - as it does not.
> however,
> | i want to make sure i gave a valid answer.
> |
> | anyone have input?
>
>
> thanks all. that's how i explained it. i didn't quite get why the value of
> $i remained the same (whatever it's initial value was)...until:
>
> $i is incremented. Then $i is set with the old (pre-increment) value of
> $i (++ has precedence over =).
>
> thanks jerry. it just snapped for me. it's that even though $i++ may
> increment, the lhs assignment is made from $i's initial value prior to the
> increment... it's the = that resets/nullifies the ++ in this case. that
> about right?
Yes. That's why the assignment is not used with $i++. $i++ is a
shorthand that both increments and assigns at the same time. If you go
and add another assignment then it's fucked.
$i = ++$i; // this would've worked as expected, though.
Maybe this helps:
<?php
function ipp(&$i){ // equivalent of $i++
$old_i = $i; // old value is stored in temporary location
$i=$i+1; // value is altered
return $old_i; // old value is returned
}
$i = 5;
$i = ipp($i);
echo $i;
function ppi(&$i){ // equivalent of ++$i
$i=$i+1; // value is altered
return $i; // new value is returned
}
$j = 10;
$j = ppi($j);
echo $j;
?>
--
Rami.Elomaa@gmail.com
"Wikipedia on vähän niinq internetin raamattu, kukaan ei pohjimmiltaan
usko siihen ja kukaan ei tiedä mikä pitää paikkansa." -- z00ze
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