Array Ref Loop

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks!

I am trying to display all elements from this array, but can't understand why the first foreach wont work.

Global symbol "$dirs" requires explicit package

How can I do this?

#!/usr/bin/perl

use strict;
use warnings; 
use Data::Dumper;


my @data_res = display(\@data);

sub display {

 my @dirs = @_;

 foreach my $i (0 .. $#dirs) {
  print "$dirs->[$i] \n";
 }
 
 #foreach my $i (@dirs) {
  #print "$i\n";
 #}

 $VAR1 = [
          '/dir/pages/books',
          '/dir/pages/books/2',
          '/dir/pages/books/2/77888k.txt',
          '/dir/pages/books/2/uhuhuhkk.txt',
          '/dir/pages/books/2/8877bg.txt',
          '/dir/pages/books/2/uuhu87777.txt',
          '/dir/pages/books/2/L',
          '/dir/pages/books/2/L/88uu8u.txt',
          '/dir/pages/books/2/L/88hhh.txt',
          '/dir/pages/books/2/L/uhuhuh.pdf',
          '/dir/pages/books/2/L/2611566_01_HA_20160819_2264063.txt',
          '/dir/pages/books/7',
          '/dir/pages/books/7/ijij8888.txt',
          '/dir/pages/books/7/555rf.txt',
          '/dir/pages/books/7/88uuhh.txt',
          '/dir/pages/books/7/88889kkk.txt'
        ];
[download]

Thank you!

Comment on Array Ref Loop Download Code

Replies are listed 'Best First'.
Re: Array Ref Loop by stevieb (Canon) on Dec 16, 2016 at 21:38 UTC
You're passing an array reference into the `display()` function, but within that function, you're not extracting things properly. You can either do this: `display(@data);` [download] ...then change your for loop in the function: `for my $dir (@dirs){ # idiomatic perl way to loop over a list print "$dir\n"; }` [download] If you want to stay with the reference, you must change how you extract the parameter(s), and then dereference the array reference when using it: sub display { # pull out the aref passed in my $dirs = shift; # could also be `my ($dirs) = @_;` # loop over the aref. Note the syntax # could also be written with the circumfix operator: # @{ $dirs } for my $dir (@$dirs){ print "$dir\n"; } } [download]	[reply] [d/l] [select]
Re: Array Ref Loop by Marshall (Canon) on Dec 17, 2016 at 00:12 UTC
A few comments: I like stevieb's post. For more study, I recommend the tutorial section of Perl Monks, specifically, Data Types and Variables which talks more about references and arrays. Also, I think that you will find that indenting loops more than one space is much, much better (stevieb did that). A normal practice is to use either 3 or 4 spaces.	[reply]