Re: How to print a multi-level Hashes of Hashes without the use of a module

[BrowserUk]

#! perl -slw
use strict;
use Data::Dump qw[ pp ];

sub dumpIt {
    my $r = shift;
    my $d = shift() // 1;
    die "'$r' not a hashref" unless ref $r eq 'HASH';
    print "{" if $d == 1;
    for( keys %$r ) {
        if( ref $r->{ $_ } ) {
            print chr(9) x $d, "$_ => {";
            dumpIt( $r->{ $_ }, $d + 1 );
            print chr(9) x $d, "}";
        }
        else {
            print chr(9) x $d, "$_ => $r->{ $_ }";
        }
    }
    print "}" if $d == 1;
}

my %multiLevelHash = (
    'firstSampleKey' => 'SampleValue',
    'secondSampleKey' => {
        'secondLevelSampleKey' => {
            'thirdLevelSampleKeyOne'   => 'thirdLevelSampleValue',
            'thirdLevelSampleKeyTwo'   => 'thirdLevelSampleValue',
            'thirdLevelSampleKeyThree' => {
                'fourthLevelSampleKey' => 'fourthLevelSampleValue',
            }
        }
    }
);

dumpIt( \%multiLevelHash );

__END__
C:\test>junk90
{
        firstSampleKey => SampleValue
        secondSampleKey => {
                secondLevelSampleKey => {
                        thirdLevelSampleKeyTwo => thirdLevelSampleValu
+e
                        thirdLevelSampleKeyThree => {
                                fourthLevelSampleKey => fourthLevelSam
+pleValue
                        }
                        thirdLevelSampleKeyOne => thirdLevelSampleValu
+e
                }
        }
}

[thanos1983]

Hello BrowserUk,

Thank you for your time and effort. I will try to experiment with your solution a little bit to become familiar. I was not aware that you can call the same subroutine inside the actual subroutine.

Again thank you for your time and effort reading my question and replying.

[Athanasius]

Hello thanos1983,

I was not aware that you can call the same subroutine inside the actual subroutine.

This is a very important concept in computer science called recursion. It’s one of the key elements of the functional programming paradigm (think Lisp, Scheme, Haskell, ...), but is by no means limited to that paradigm. In fact, it’s something every programmer needs to know. Here are some references:

• Wikipedia, Recursion_(computer_science)
• DigitalKitty, Recursion: The Towers of Hanoi problem (Monastery Tutorial)
• Gabor Szabo (szabgab), “Understanding Recursive Subroutines — Traversing a Directory Tree,” online
• Jonathan Bartlett, “Mastering Recursive Programming,” online
• Mark Jason Dominus, Higher-Order Perl, “Chapter 1: Recursion and Callbacks,” online

Hope that helps,

[thanos1983]

Hello Athanasius,

Wow thank you for your time and effort providing me all these tutorials. To be honest at the beginning it was not the easiest thing to understand, but reading one after the other tutorial it started to make more sense. Thank you again for your time and effort.

[Anonymous Monk]

I was not aware that you can call the same subroutine inside the actual subroutine.

You may want to have a look at recursion, which Perl supports.

[thanos1983]

Hello Anonymous Monk,

Thank you for your time and effort to provide me with more information. It starts to make more sense to me know.