Dump array in perl

Question

I need to fill some array with data and dump it to the screen. Here is the code:

my @a;

@a[0] = 69;
foreach $sibling ($someotherlist){
    my $cha = $sibling->{"id"} * 1;

    if (defined @a[$cha]){
        @a[$cha] = 0;
    }

    @a[$cha] = @a[$cha] + 1;
}
print Dumper(@a);

The problem is that it only prints $VAR1 = 69;
It should be something like:

$VAR1 = {
   0 => 69,
   1 => 30,
   20 => 90
}

You need to turn on use strict; use warnings;. You will then get at least one warning of Scalar value @a[0] better written as $a[0] — TLP
– TLP, Commented Nov 14, 2014 at 14:20
Tip: if (defined $a[$cha]) { $a[$cha] = 0; } can be simplified to $a[$cha] //= 0;. If you don't want a dependency on Perl 5.10+, you can use $a[$cha] ||= 0; in this case. — ikegami
– ikegami, Commented Nov 14, 2014 at 14:44
Tip: $a[$cha] = $a[$cha] + 1; can be simplified to ++$a[$cha]. — ikegami
– ikegami, Commented Nov 14, 2014 at 14:46

Gilles Quénot · Accepted Answer · 2014-11-14 13:59:25Z

6

Always use references with Data::Dumper, so

print Dumper(\@a);

See

answered Nov 14, 2014 at 13:59

Gilles Quénot

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1 Comment

ikegami Over a year ago

Except he wants to get a hash when he has an array... There's insufficient information to help him with that, though.

G. Cito · Accepted Answer · 2014-11-14 14:34:40Z

1

You might want to install Data::Printer which can be used via its DDP alias from the command line as -MDDP or as use DDP; inside an application. In your case:

use DDP; 

... # [rest of script] 

p @a ;

Data::Dumper remains the standard but DDP is quite useful and easily configurable. The colours and shiny things and p() shortcut :-) make DDP easy to use as a "visualization aid" for data structures.

answered Nov 14, 2014 at 14:34

G. Cito

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Comments

Never Sleep Again · Accepted Answer · 2019-05-28 22:19:52Z

0

I've become a big fan of

use JSON;
warn to_json(\%data,{canonical=>1,pretty=>1});

even though it's a mess of typing.

answered May 28, 2019 at 22:19

Never Sleep Again

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