Re: Use a hashref as a key in another hashref?

[2teez]

hi mwb613,
..Is it possible to use hash reference as a key in another hash reference?..

Ordinarily, maybe not! (But that is a 'white' lie) ;) Until you consider module like Tie::RefHash, which allows you use reference as hash key.

use strict;
use warnings;

use Data::Dumper;
use Tie::RefHash;

tie my %h, "Tie::RefHash";

my $key_hash_1 =
  { 'day' => 1, 'month' => 1, 'year' => 2000, 'hour' => 4, 'minute' =>
+ 44 };
my $key_hash_2 =
  { 'day' => 1, 'month' => 1, 'year' => 2000, 'hour' => 4, 'minute' =>
+ 45 };

%h = (
    $key_hash_1 =>
      { 'burgers_sold' => 5, 'fries_sold' => 3, 'sodas_sold' => 11 },
    $key_hash_2 => { 'burgers_sold' => 2, 'fries_sold' => 4, 'sodas_so
+ld' => 7 }
);

print Dumper( $key_hash_1, $key_hash_2 );
print Dumper( \%h );

for ( keys %h ) {
    print join ' ' => %{$_}, ' => ', %{ $h{$_} }, $/;
}

Output:

$VAR1 = {
          'hour' => 4,
          'minute' => 44,
          'month' => 1,
          'day' => 1,
          'year' => 2000
        };
$VAR2 = {
          'hour' => 4,
          'minute' => 45,
          'month' => 1,
          'day' => 1,
          'year' => 2000
        };
$VAR1 = {
          'HASH(0x8e963e0)' => {
                                 'fries_sold' => 3,
                                 'sodas_sold' => 11,
                                 'burgers_sold' => 5
                               },
          'HASH(0x8eb01d0)' => {
                                 'fries_sold' => 4,
                                 'sodas_sold' => 7,
                                 'burgers_sold' => 2
                               }
        };
hour 4 minute 44 month 1 day 1 year 2000  =>  fries_sold 3 sodas_sold 
+11 burgers_sold 5 
hour 4 minute 45 month 1 day 1 year 2000  =>  fries_sold 4 sodas_sold 
+7 burgers_sold 2

Secondly, I think where you are using chains of while loops, a for loop would have been better.

[tobyink]

There's also a Tie::RefHash::Weak on CPAN. (The core module Tie::RefHash treats keys as strong references.)