Perl: what is 'my $data1{}'

[bcostacurta]

Hello,

I have a code containing

...
my $data1{};
my $ret = function($data1, ..other..);
...

As far as I undertand data1 is an associative array.
How can I parse $data1 ?
I do not know its structure.

Thanks for any clue.

Bye,
Bruno

[Cabhan]

The code that you wrote is not valid. I will assume that you meant this:

my $data1 = {};
my $ret = function($data1, ..other..);

(note the addition of an equals sign to the first line)

In this case, $data1 is what we call a hashref, or a reference to a hash / associative array. $data1 is a scalar, but when dereferenced, produces a hash. If you don't already know about references, I suggest learning about them: they are a bit complicated, but in more advanced Perl, you use them all the time.

To print a hashref, you might do something like this:

my @keys = sort(keys(%$data1));
for my $key (@keys)
{
    print "$key -> ", $data1->{$key}, "\n";
}

[bcostacurta]

Dear Cabhan,
thanks a lot. You save my day

Bye,
Bruno

[bcostacurta]

As I'm able now to display values in mydata1, ie:

CodedCharSetId -> 850

How can I modify a value in it ?
I continue to struggle with the syntax and prefix $ or % ..etc..

Thanks for help
Bruno

[Cabhan]

Once again, I would suggest finding a good tutorial on references for all of this information.

In any event, I showed you how to get a value from a hashref: assigning a value is pretty obvious at that point:

print $hashref->{$key};
$hashref->{$key} = "value";

[bcostacurta]

Dear Cabhan,
thanks a lot again for your help.

Just to keep you in touch about your (good) advices as I indeed bought some Perl books:

- 'Learning Perl' by Randal Schwartz (aka 'The Llama book')
- 'Programming Perl' by Larry Wall (I suppose aka 'The Camel book')

I found 'Learning Perl' is a great Perl book, I really enjoy reading it, and I must admit that I discover (and now love) Perl by reading it.

Hopefully my next questions on the forum will be more accurate.

Bye,
Bruno