Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-28 Thread Rory Browne 
 $a = $b ^^  $c

You sure? It didn't work for me, and it isn't listed in the PHP manual.

I used:
?php
var_dump(1 ^^ 0);
var_dump(0 ^^ 1);
var_dump(0 ^^ 0);
var_dump(1 ^^ 1);
?

to test it and got a syntax error. 

I suppose you could use the bitwise one as a bit of a hack, so long as
you 'boolean-ised' both arguments first.
eg $a = (!!$b) ^ (!!$c);   // or even $a = !$b ^ !$c; since xor
depends exclusively on both sides being different to each other.


  Generally however there is no need to parentisize everything to the
  right of the assignment operator(=), since besides 'and', 'or', 'xor',
  and the comma operator. The only time I see the need to parentisize
  everything to the right is when using the xor operator, since there is
  no equivlent above the = operator.
 
 $a = $b ^^ $c;
 
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Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-27 Thread Jose M.Herrera 
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Rory Browne wrote:
| I think what Jose is trying to say, is that because 'or' has a lower
| precidence than =, you are interpreting the expression wrong.
Yes, I was trying to say that. The () are very important when you need
to use OR, AND, ||, , etc...
Bye!, Merry Christmas and a happy new year for all!!
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Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-27 Thread Rory Browne 
I think what this highlights is that the or operator isn't supposed to
be used in that way. It is simply supposed to be used to add a back
door to failed function calls.
ie
mysql_connect(args) or die(mysql connection failed)

If you want to return true when either $a or $b is true, then use ||.
eg

$ret = $a || $b;
return $a || $b; // although 'or' would work here too

In the end, whilst you should try to have a general idea of the
precidence operators, for the purpose of debugging other peoples code,
you should always parentisize your own.

Generally however there is no need to parentisize everything to the
right of the assignment operator(=), since besides 'and', 'or', 'xor',
and the comma operator. The only time I see the need to parentisize
everything to the right is when using the xor operator, since there is
no equivlent above the = operator.

Check out http://www.php.net/manual/en/language.operators.logical.php
and follow the link to operator Precidence.

Sorry if you recieved this twice. I forgot to cc it to the list first
time around.

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Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-27 Thread Thomas Goyne 
On Mon, 27 Dec 2004 21:19:39 +, Rory Browne [EMAIL PROTECTED]  
wrote:

Generally however there is no need to parentisize everything to the
right of the assignment operator(=), since besides 'and', 'or', 'xor',
and the comma operator. The only time I see the need to parentisize
everything to the right is when using the xor operator, since there is
no equivlent above the = operator.
$a = $b ^^ $c;

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Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-26 Thread Rory Browne 
I think what Jose is trying to say, is that because 'or' has a lower
precidence than =, you are interpreting the expression wrong.

$b1 = is_null($x) or ($y  5);

is the same as 
($b1 = is_null($x)) or ($y  5)
This assigns the value of is_null($x) to $b1, regardless of the result
of ($y  5). It's shorthand for

if( !($b1 = is_null($x)) ){
($y  5);
} 

similarly 

$b2 = ($y  5) or is_null($x);

assigns $b2 to ($y  5), or in this case true(since $y == 10). If ($y
 5) returned false, ie if $i = 5, then it would call the function
is_null($x). In this case calling the function is_null() is pointless,
since you aren't using the result.

What I think you are looking for is either
$b2 = (($y  5) or is_null($x)); // whole thing right of = enclosed in brackets

or 

$b2 = ($y  5) || is_null($x); // '||' has higher precidence than 'or'



On Fri, 24 Dec 2004 16:47:42 -0300, Jose M.Herrera
[EMAIL PROTECTED] wrote:
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 Bogdan Ribic wrote:
 | Here's a little test script:
 |
 | 
 | $x = 2;
 | $y = 10;
 |
 | $b1 = is_null($x) or ($y  5);
 | $b2 = ($y  5) or is_null($x);
 
 Yes, of course.
 Your code or example, is just like:
 
 ( $b1 = is_null($x) )  or ( $y  5  ) ;
 ( $b2 =  ($y  5)   )  or  is_null($x) ;
 
 The  has more precedence than =, or it has a very low precedence.
 Then, $b1 = false and $b2 = True... that's ok! :P
 
 You example, must have been:
 
 $b1 = (   ( is_null($x) )  or ( $y  5  ) );
 $b2 = (   ( $y  5  )  or ( is_null($x) ) );
 
 I this example the value of $b1 is all between the parenthesis (explicitly).
 
 Bye!
 
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Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-26 Thread Richard Lynch 
Bogdan Ribic wrote:
 $b1 = is_null($x) or ($y  5);
 $b2 = ($y  5) or is_null($x);

To add to what has been posted already:

If 'or' isn't what you want '||' probably *IS* what you want.

Watch out though -- Sometimes even the precedence of '||' isn't as
high/low as I hoped, and if in doubt, use parentheses to force things to
happen in the order you want.

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Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-24 Thread Jose M.Herrera 
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Bogdan Ribic wrote:
| Here's a little test script:
|
| 
| $x = 2;
| $y = 10;
|
| $b1 = is_null($x) or ($y  5);
| $b2 = ($y  5) or is_null($x);
Yes, of course.
Your code or example, is just like:
( $b1 = is_null($x) )  or ( $y  5  ) ;
( $b2 =  ($y  5)   )  or  is_null($x) ;
The  has more precedence than =, or it has a very low precedence.
Then, $b1 = false and $b2 = True... that's ok! :P
You example, must have been:
$b1 = (   ( is_null($x) )  or ( $y  5  ) );
$b2 = (   ( $y  5  )  or ( is_null($x) ) );
I this example the value of $b1 is all between the parenthesis (explicitly).
Bye!
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Est.Ing.Civil Informatica - UTFSM
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[PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-23 Thread Bogdan Ribic 
Here's a little test script:

$x = 2;
$y = 10;
$b1 = is_null($x) or ($y  5);
$b2 = ($y  5) or is_null($x);
var_dump($b1);
var_dump($b2);

Obviously, it should be false for both $b1 and $b2, but the output is:
bool(false)
bool(true)
Is this a bug? I tried dumping values of two expressions, they are both
boolean and correct value. Tried assigning values to two temp vars and
then or-ing these two, and that gave correct results.
I really cannot see what am I doing wrong. Tried this with php 4.3.2 and
4.3.9, and I get these weird results both times.
Maybe I should herd cattle or something :)
Boban.

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Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-23 Thread Rasmus Lerdorf 
Bogdan Ribic wrote:
Here's a little test script:

$x = 2;
$y = 10;
$b1 = is_null($x) or ($y  5);
$b2 = ($y  5) or is_null($x);
var_dump($b1);
var_dump($b2);

Obviously, it should be false for both $b1 and $b2, but the output is:
bool(false)
bool(true)
Is this a bug? I tried dumping values of two expressions, they are both
boolean and correct value. Tried assigning values to two temp vars and
then or-ing these two, and that gave correct results.
I really cannot see what am I doing wrong. Tried this with php 4.3.2 and
4.3.9, and I get these weird results both times.
Maybe I should herd cattle or something :)
The whole point of OR is that it is a very low precedence operator. 
Think of it as being at the bottom of the precedence table (it isn't 
quite, ',' is lower) so you can do:

$a = b() + $c / $d OR echo false;
That is, do everything before the OR first, then see what that evaluates 
to before applying the OR.  This wouldn't work if it took precedence 
over anything in the rest of the expression.

-Rasmus
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Re: [PHP] A serious bug? or operator gives out diffferent results depending on order of operands

2004-12-23 Thread Comex 
Uh.. $y is  5.

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