Is there a difference for this booleans

[r2d22y]

Hello

Is there a difference between:

if(defined $myvalue){

}


and

if($myvalue){

}

What I want to control is if $myvalue has a value or not
$myvalue is a Hashvalue that maybe isnt set so thats wy I have to control if it exists.

Regards/D_S

 

[TrojanWarBlade]

Yes, there is a BIG difference.

Your second example tests for "truth". 0, "" and undef are all considered false and everything else is true.

In your first example, ONLY undef is false, everything else (including 0 and "") is true.



Trojan.

 

[tchatzi]

if in your code you have

$foo{key} = 0;
$myvalue = $foo{key};
if (defined $myvalue){print "defined\n";}

it will print 'defined '

$myvalue = 0;
if (defined $myvalue){print "defined\n";}

it will print 'defined '

$myvalue = $foo{key};
if (defined $myvalue){print "defined\n";}

it will print nothing

on the other hand

$myvalue = $foo{key};
if ($myvalue){print "it has something in it\n";}

it will print nothing

$myvalue = 0;
if ($myvalue){print "it has something in it\n";}

it will print nothing

$myvalue = "whatever";    # except 0 or ''
if ($myvalue){print "it has something in it\n";}

it will print "it has something in it"

Did you get the difference?


``The wise man doesn't give the right answers,
he poses the right questions.''
TIMTOWTDI

 

[r2d22y]

Yes I do...Thanks!

/D_S