How do you determine the size of array reference?

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

Brother Monks, I've Super Searched, I've Googled, and I've played with the smallest possible program (below) I could build, but I haven't been able to find how to deterime the size of a reference to an array (not a hash)

use strict;

my @Header =
  (
   'Record Type               ',
   'File Generation Date/Time ',
   'Origin                    ',
  );

my @New;
my @Trailer;

my %Classes = (
        'NW' => { labels => \@New },
        'HD' => { labels => \@Header },
        'TR' => { labels => \@Trailer },
       );

my $type = 'HD';
Display( $Classes{ $type }->{labels} );

sub Display
  {
    my ( $Labels ) = @_;

    my $count = scalar( $Labels ); ### I know this doesn't work.

    print sprintf( "Display: %d '%s'\n", $count, $Labels->[1] );
  }
[download]

I realize if I was using an array (rather than an array reference) I could use $#name or scalar( @Name ).

Unfortunately, I need to use the contents of @Header sequentially, so using a hash isn't an option.

Thank you for your help in advance.

Comment on How do you determine the size of array reference? Select or Download Code

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Re: How do you determine the size of array reference? by Fletch (Bishop) on Jul 02, 2007 at 15:39 UTC
`scalar @{ $arrayref }` Pretty much wherever you use `@array` you can substitute in `@{$arrayref}` (and the related invocation for the last index of the array ref is `$#{ $arrayref }`, but you really shouldn't be using that to determine the size).	[reply] [d/l] [select]
Re^2: How do you determine the size of array reference? by apl (Monsignor) on Jul 02, 2007 at 17:11 UTC
Thanks, Fletch. That echo you hear is me slapping my forehead...	[reply]
Re: How do you determine the size of array reference? by naikonta (Curate) on Jul 02, 2007 at 15:50 UTC
I've Super Searched, I've Googled Really? Try this: array size, or determine array size in perl. But, what do you really mean by array size? The number of elements? `my @array = (1 ..4); my $size = @array; print "The size of array \@array is $size\n";` [download] The memory size? `use Devel::Size 'size'; my @array = (1 ..4); my $size = size(\@array); print "The size of array \@array is $size\n";` [download] Should you used an array reference, then you could do the same. `my @array = (1 ..4); my $ar_ref = \@array; my $size = @$ar_ref; print "The size of array \@array is $size\n"; use Devel::Size 'size'; my $memory = size($ar_ref); print "The size of array \@array is $memory\n";` [download] Open source softwares? Share and enjoy. Make profit from them if you can. Yet, share and enjoy!	[reply] [d/l] [select]
Re^2: How do you determine the size of array reference? by apl (Monsignor) on Jul 02, 2007 at 17:17 UTC
Many thanks, naikonta. My queries were along the lines of Perl array reference size. reference probably made it too specific, while size (in 20-20 hindsight) should have been something like number of elements. IAE, I thank you for your time.	[reply]
Re: How do you determine the size of array reference? by mikeB (Friar) on Jul 02, 2007 at 15:39 UTC
Try `perldoc perlreftut` for all your reference (and dereferencing) needs.	[reply] [d/l]
Re^2: How do you determine the size of array reference? by apl (Monsignor) on Jul 02, 2007 at 17:09 UTC
~~Many thanks. I'll read it this afternoon...~~	[reply]
Re: How do you determine the size of array reference? by FunkyMonk (Bishop) on Jul 02, 2007 at 16:08 UTC
This... I realize if I was using an array (rather than an array reference) I could use $#name or scalar( @Name ). ...makes me think you want the number of elements in a reference to an array. You need to convert your arrayref to an array, like so `my $arrayref = [ 1, 2, 3 ]; #step-by-step my @array = @$arrayref; # derefernce to array, @{ $arrayref } works to +o my $num_elements = @array; #in one step $num_elements = @$arrayref; #or, when in list context print scalar @$arrayref; #or, if it's the last element number you want print $#$arrayref;` [download]	[reply] [d/l]
Re^2: How do you determine the size of array reference? by apl (Monsignor) on Jul 02, 2007 at 17:20 UTC
~~Thank you for your time and your patience, FunkyMonk. That's exactly what I needed to know.~~	[reply]
Re: How do you determine the size of array reference? by leocharre (Priest) on Jul 02, 2007 at 16:23 UTC
`my $ar1 = [qw(this is another element)]; my $ar2 = [ 'this','is','another','element']; my @a1 = ('this','is','another','element'); my @a2 = (qw(this is another element)); printf " \$ar1 has %s elements \$ar2 has %s elements \@a1 has %s elements \@a2 has %s elements ", scalar @$ar1, scalar @{$ar2}, scalar @a1, scalar @a2;` [download]	[reply] [d/l]
Re^2: How do you determine the size of array reference? by apl (Monsignor) on Jul 02, 2007 at 17:21 UTC
~~Many thanks, leocharre.~~	[reply]