Passing an Array of an Array to a subroutine using perl

Question

Ok, so I got an array of an array (AoA) and I need to pass it to a subroutine, and then access it. This works… but is it strictly correct and indeed is there a better way that I should be doing this?

#!/usr/bin/perl
$a = "deep";
push(@b,$a);
push(@c,\@b);

print "c = @{$c[0]}\n";
&test(\@c);

sub test
{
    $d = $_[0];
    print "sub c = @{$$d[0]}\n";
}

Thanks

Instead of $d = $_[0] I'd say my ($d) = @_. And in your sub, you should be able to say $d->[0]->[0] to dereference your AoA. — Joe Z
– Joe Z, Commented Dec 7, 2013 at 7:00

Tudor Constantin · Accepted Answer · 2013-12-07 07:57:00Z

3

The definitely better way to do it is to use strict; and use warnings; and to declare your variables before using them.

Also, you know that is not good practice to name your vars a or b - give them meaningful names, especially because the $a variable for example, is defined by the compiler (the one used with sort {} @).

answered Dec 7, 2013 at 7:57

Tudor Constantin

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2 Comments

Tim Pierce Over a year ago

Using meaningful names is always helpful, of course, but the $a variable is only predefined in the dynamic scope of a sort call. Defining global $a and $b variables poses no conflict with sort.

Tudor Constantin Over a year ago

@qwrrty try this perl -e 'use strict; use warnings; $a=1; print $a;' and then try this perl -e 'use strict; use warnings; $r=1; print $r;'

ikegami · Accepted Answer · 2013-12-07 19:34:12Z

1

use strict;          # Always!
use warnings;        # Always!

sub test {
    my ($d) = @_;
    print "$d->[0][0]\n";

    # Or to print all the deep elements.
    for my $d2 (@$d) {
       for (@$d2) {
          print "$_\n";
       }
    }
}

{
   my $a = "deep";   # or:  my @c = [ [ "deep" ] ];
   my @b;
   my @c;
   push(@b,$a);
   push(@c,\@b);
   test(\@c);        # Can't pass arrays per say, just refs. You had this right.
}

Still needs better names. In particular, $a and $b should be avoided as they can interfere with sort.

edited Dec 7, 2013 at 19:34

answered Dec 7, 2013 at 16:39

ikegami

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