How to compare an empty key with another empty key in associative array

[nandymamith]

Am trying to compare two values, say $a = ''; $b = {}; if($a eq $b){ print "PASS"; } else { die "FAIL"; } May i know how to get the output as PASS ?? moreover i don't want get my out put as FAIL. In short how to compare the associative array($b) with the empty variable ($a)

[bart]

That sounds like you're coming from PHP. Well, OK, I'll write a little utility function empty which should look a bit familiar. That way you can compare if 2 values are both empty.

sub empty {
    my $r = shift;
    if(!ref $r) { return !$r }
    if(ref $r eq 'HASH') { return !keys %$r }
    if(ref $r eq 'ARRAY') { return !@$r }
    if(ref $r eq 'SCALAR') { return !$$r }
    return !1;    
}
$a = ''; $b = {}; $c = [];
if(empty($a) && empty($b) && empty($c)) { print "PASS"; }

[DrHyde]

'' and {} are different in just about every possible way. What you are trying to do is equivalent to comparing a strawberry and a moose and say that they're the same.

[2teez]

Hi nandymamith,


• $a = ''; $b = {};
  You really don't want to use $a and $b which are aliases for the two operands being compared in a sortsub.
• That been said, $a and $b in above are two different things in perl. While $a is an empty scalar variable, $b is a reference to an anonymous hash, created using curly brackets which is empty in this case

However, in this case, you can compare these, printing what you want like so:

use warnings;
use strict;

my $empty_str = q{};
my $empty_hash_ref = { q{} => q{}, };

for ( keys %$empty_hash_ref ) {
    $empty_str eq $_ ? print "PASS" : print "FAIL";  ## print PASS
}

## use smartmarch ~~
$empty_str ~~ $empty_hash_ref ? print "PASS" : print "FAIL"; ## print 
+PASS

• Note however, that iterating through the hash comparing either the keys or values of the hash with the empty scalar variable, when the hash is empty ( with no variable atall) will print nothing, but using the smart match ~~ Operator will print "FAIL"
.

  my $empty_str = q{};
  my $empty_hash_ref = {};  ## why?

   for (keys %$empty_hash_ref){
       $empty_str eq $_? print "PASS": print "FAIL"; # print nothing
   }

   $empty_str~~$empty_hash_ref?print "PASS": print "FAIL"; # print FAI
+L


Hope this helps

[Rudolf]

$b = {}; is not an associative array. An array containing other arrays may look something like this:

my @two_d_array = ([$x,$y,$z],[1,2,3],['a','b','c']);

To see if an array is empty, you can check it's scalar value for contents.

my $elements = scalar(@two_d_array);

UPDATED: Associative array is considered a hash in Perl, (thanks choroba),

[choroba]

"Associative array" is "hash" in Perl lingo, not an array.