Hash of Arrays

[Akino877]

Hello,

I read in a book that I can create a hash of arrays like this :

%hash = ( "testA" => [77,88],
                  "testB" => [90, 91] );
 

In this code, each key is associated with a reference to an array.
My question is can I set it up so that each key is associated with
an array - not a reference to an array?

I have tried :

%hash = ("testA", (77,88),
                 "testB", (90,91) );
 

But it did not work for me.

Thank you - Akino

[Kelicula]

What is the benefit? Why are you trying to make each key be associated with an array as opposed to a reference to an anonymous array?

[Akino877]

Hi Kelicula,

Thank you very much for your reply.

There is no reason for me to try to do that - I was just curious.
Now, I understand that a value in a hash can only be a scalar.

Akino

[Kelicula]

No problem Akino877!
The way perl overcomes this is through "references", you can use a reference to an array or hash, or even an array of hashes or hash of arrays as a value for a hash, here's an example:
To make a reference you simply use the slash like so:
my @array = ('Jon', 'James', "jimmy', 'Julie');
my $array_ref = \@array;

Now $array_ref is a scalar value that points to the memory allocation spot of the array named @array.

Or you can just make a reference initially with the square brackets:

my $array = ['Jon', 'James', 'jimmy', 'Julie'];

Then
my %hash = ( one => $array, two => $array2, etc... );

To make a reference to an anonymous hash you can use the "{" like so:

my $hash_ref = { one => $array_ref, two => $array_ref2, etc..};

You access these references with the special arrow operator:
$hash->{one}->[1] would equal "James".

Data structures can be very complicated and deep in Perl, but it's all accomplished through references, there are really only 4 types of values in perl; scalar, hash, array, or TYPEGLOB.

There's WAY to much about this to include here, but that should give you some terms to Google with ;-)

Here is a great place to start:
http://perldoc.perl.org/perlref.html

Happy coding...