| arpad@php.net 2007-04-30, 8:06 am |
| ID: 41228
Updated by: arpad@php.net
Reported By: terminatorul at gmail dot com
Status: Open
Bug Type: Documentation problem
PHP Version: Irrelevant
New Comment:
This isn't a side-effect, but an intrinsic property of these operators.
As two out of the four user notes on the page mention, the first dating
back to 1999, these operators short-circuit.
Perhaps this could be explained in the text to make it clearer for
people new to programming, but I don't think there's any great need;
I assume most people can look up terms they're not familiar with.
Previous Comments:
------------------------------------------------------------------------
[2007-04-30 09:00:14] rquadling@php.net
Agreed.
<?php
// Echo's F and does NOT set $a.
echo (False && ($a=1)) ? 'T' : 'F';
// Echo's T, sets $b but does not set $c.
echo (($b=2) || False || ($c=3)) ? 'T':'F';
// Turn off notices about undefined variables for $a and $c.
error_reporting(E_ALL & ~E_NOTICE);
// Rather than "1 2 3", we get just " 2 ".
echo "$a $b $c";
?>
------------------------------------------------------------------------
[2007-04-29 18:29:26] terminatorul at gmail dot com
Description:
------------
The manual page for logical operators
http://www.php.net/manual/en/langua...ors.logical.php
should warn users that the right-hand operand of && or ||
will never be evaluated if that is not necesary
For example when doing:
$result = FALSE && mysql_query($query);
than the mysql $query will never get executed.
Or at least the page should advise users to never rely on side-effects.
Reproduce code:
---------------
http://www.php.net/manual/en/langua...ors.logical.php
Expected result:
----------------
The page should say something like:
For the binary logical operators the second operand will never be
evaluated when it is clear from the first operand what the result will
be.
For example the code
$prev_status = FALSE;
$crt_status = $prev_status && mysql_query($query);
echo mysql_affected_rows();
will never execute the query, simply because $crt_status will be FALSE
no matter what mysql_query() would return.
Actual result:
--------------
Right now I can see nothing about side-effects in the page.
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=41228&edit=1
|