Re^2: Dereferencing a Hash of Arrays

input:

my @atags = qw( 1 2 3 4 );
my @btags = qw( 9 8 7 6 );

my %alphabet = (
     'a' => \@atags,
     'b' => \@btags,
             );

say for values %alphabet;
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output:

ARRAY(0x8376dd8)
ARRAY(0x837f298)
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UPDATE: I did say for values %alphabet in response to an earlier version of Re^1 without the @{...}. My original code was my %alphabet = ('a', \@atags, 'b', \@btags); say for @{values %alphabet}; which prints an error similar to the OP.

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Re^3: Dereferencing a Hash of Arrays by johngg (Canon) on Jun 14, 2011 at 10:40 UTC
The "values" are array references so you have to dereference them using `@{ ... }` to get the array elements. You can also get there using keys and dereferencing the looked up value in the hash. knoppix@Microknoppix:~$ perl -MData::Dumper -Mstrict -wE ' > my @aTags = ( 1 .. 4 ); > my @bTags = reverse 6 .. 9; > my %alpha = ( a => \ @aTags, b => \ @bTags ); > print Data::Dumper->Dumpxs( [ \ %alpha ], [ qw{ alpha } ] ); > say q{-} x 20; > say qq{@{ $_ }} for values %alpha; > say q{-} x 20; > say qq{@{ $alpha{ $_ } }} for keys %alpha; > say q{-} x 20; > foreach my $arrayRef ( values %alpha ) > { > say for @{ $arrayRef }; > say q{-} x 20; > } > foreach my $key ( keys %alpha ) > { > say for @{ $alpha{ $key } }; > say q{-} x 20; > }' %alpha = ( 'a' => [ 1, 2, 3, 4 ], 'b' => [ 9, 8, 7, 6 ] ); -------------------- 1 2 3 4 9 8 7 6 -------------------- 1 2 3 4 9 8 7 6 -------------------- 1 2 3 4 -------------------- 9 8 7 6 -------------------- 1 2 3 4 -------------------- 9 8 7 6 -------------------- knoppix@Microknoppix:~$ [download] I hope this is helpful. Update:* Expanded the example code to show how to print one element per line as the OP's code seemed to want. Cheers, JohnGG	[reply] [d/l] [select]

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Re^3: Dereferencing a Hash of Arrays
by johngg (Canon) on Jun 14, 2011 at 10:40 UTC

The "values" are array references so you have to dereference them using @{ ... } to get the array elements. You can also get there using keys and dereferencing the looked up value in the hash.

knoppix@Microknoppix:~$ perl -MData::Dumper -Mstrict -wE '
> my @aTags = ( 1 .. 4 );
> my @bTags = reverse 6 .. 9;
> my %alpha = ( a => \ @aTags, b => \ @bTags );
> print Data::Dumper->Dumpxs( [ \ %alpha ], [ qw{ *alpha } ] );
> say q{-} x 20;
> say qq{@{ $_ }} for values %alpha;
> say q{-} x 20;
> say qq{@{ $alpha{ $_ } }} for keys %alpha;
> say q{-} x 20;
> foreach my $arrayRef ( values %alpha )
> {
>     say for @{ $arrayRef };
>     say q{-} x 20;
> }
> foreach my $key ( keys %alpha )
> {
>     say for @{ $alpha{ $key } };
>     say q{-} x 20;
> }'
%alpha = (
           'a' => [
                    1,
                    2,
                    3,
                    4
                  ],
           'b' => [
                    9,
                    8,
                    7,
                    6
                  ]
         );
--------------------
1 2 3 4
9 8 7 6
--------------------
1 2 3 4
9 8 7 6
--------------------
1
2
3
4
--------------------
9
8
7
6
--------------------
1
2
3
4
--------------------
9
8
7
6
--------------------
knoppix@Microknoppix:~$
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I hope this is helpful.

Update: Expanded the example code to show how to print one element per line as the OP's code seemed to want.

Cheers,

JohnGG

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