8. Complex data structures - 5: Custom complex structure

You're are able now to create your own data structure using the datatypes you've seen. I made one for demonstration purposes only.
I also introduce you to the module Data::Dumper, which stringifies perl data structures, suitable for both printing and evaluation.

8.1 Create a custom complex structure

As already stressed in previous chapters, you can always use a reference in a list. So, let's define an array, containing a list.

@CS = 
(
  'Reinier',
  'www.reiniermaliepaard.nl',
  'Perl',
);

print("Name: $CS[0]\n");
print("Website: $CS[1]\n");
print("Programming: $CS[2]");

Nothing new here. Let's extend this structure with an anonymous hash and an anonymous array reference.

@CS = 
(

  { # anonymous hash
    first_name => 'Reinier',
    last_name => 'Maliepaard',
  },

  'www.reiniermaliepaard.nl', # scalar value
   ['Perl', 'newLisp', 'Windows Commandline'] # anonymous array

);

print("First name: ${$CS[0]}{'first_name'}\n");
print("Last name: ${$CS[0]}{'last_name'}\n");
print("Website: $CS[1]\n");
print("Programming: @{$CS[2]}");

If you're aware of the internal structure of this array, then there is no problem. But the job can be done better, i.e. adding a label to the several fields.

8.2 A better custom complex structure

In Chapter 8 Hashes of Hashes, you read about an alternative way to construct a HoH. I use it now to create my Complex Structure.

%CS = ();
$CS{'Name'}{'first_name'} = 'Reinier';
$CS{'Name'}{'last_name'} = 'Maliepaard';
$CS{'Website'} = 'www.reiniermaliepaard.nl';
$CS{'Programming'}{'language'}->[0] = 'Perl';
$CS{'Programming'}{'language'}->[1] = 'newLisp';
$CS{'Programming'}{'language'}->[2] = 'Windows commandline';

This is equivalent to (see comments)

%CS = (
 'Name'        => {  # hash of hash
                    'first_name' => 'Reinier',
                    'last_name'  => 'Maliepaard',
                  },
 'Website'     => 'www.reiniermaliepaard.nl',  # normal hash
 'Programming' =>  {  # hash of hash of arrays
                     'language' => ['Perl','newLisp','Windows Commandline'],
                   },
);

Most important, this code is readable, thanks to its descriptive labels.

8.3 Data::Dumper

Save the following code to e.g. Test.pl and run it in the terminal.

use Data::Dumper;
%CS = ();
$CS{'h1'} = 'h1_value';
$CS{'h2'}{'h2_key1'} = 'h2_key1_value';
$CS{'h2'}{'h2_key2'} = 'h2_key2_value';
$CS{'h3'}{'h3_key1'}->[0] = 'h3_key1_value1';
$CS{'h3'}{'h3_key1'}->[1] = 'h3_key1_value2';
$CS{'h3'}{'h3_key1'}->[2] = 'h3_key1_value3';
$CS{'h3'}{'h3_key2'}->[0] = 'h3_key2_value1';
$CS{'h3'}{'h3_key2'}->[1] = 'h3_key2_value1';
print Dumper(\%CS);

The result should be like:

In other words, the Module Dumper helps you printing a complex structure.