HASH INITIALISATION

[naq2]

A very simple question for you guys, expert of hashes:
Can I do that? (I mean... will it work?)

my %myHash ;

$myHast{toto}{tata} = "DID YOU SEE THIS?!" ;

print $myHast{toto}{tata} ;
#will this print 'DID YOU SEE THIS?' or do I have to initialise the hash in some other way?

Thanks for your help.

 

[mikevh]

It's %myHash, not %myHast. Fix the typo and it'll work.

#!perl
use strict;
use warnings;
use Data::Dumper;

my %myHash ;

$myHash{toto}{tata} = "DID YOU SEE THIS?!";
my $d = Data::Dumper->new([\%myHash], [qw(*myHash)]);
print $d->Dump;

[b]Output:[/b]
%myHash = (
            'toto' => {
                        'tata' => 'DID YOU SEE THIS?!'
                      }
          );

 

[naq2]

Ok...

This was only an example of my question... so the answer is YES... it should initialise the value correctly.

Thanks.

 

[naq2]

OK...

In the same idea... if I want to add a new array in a hash... can I use the same thing?

my %myHash ;

push(@myHash{anyArray}, "NEW ELEMENT") ;

And if it doesn't work (coz it seams not to work... I get a compilation error), how should I do something like this?

Thanks for your help.

 

[mikevh]

$myHash{anyArray} is an array reference.
push expects an actual array as first argument, not a reference. You need to dereference
$myHash{anyArray} using @{...}.

#!perl
use strict;
use warnings;
use Data::Dumper;

my %myHash ;

$myHash{anyArray} = [];  [b]#an array ref[/b]
#or: @{$myHash{anyArray}} = (); [b]#dereferenced as actual array[/b]
push(@{$myHash{anyArray}}, "NEW ELEMENT"); [b]#push requires array, not ref[/b]

$myHash{toto}{tata} = "DID YOU SEE THIS?!";

my $d = Data::Dumper->new([\%myHash], [qw(*myHash)]);
print $d->Dump;

[b]Output:[/b]
%myHash = (
            'toto' => {
                        'tata' => 'DID YOU SEE THIS?!'
                      },
            'anyArray' => [
                            'NEW ELEMENT'
                          ]
          );

Check out
perldoc perlreftut
perldoc perldsc
perldoc perllol
perldoc perlref

 

[naq2]

ok... thanks a lot for this explanation.

Just one more question:
Do I really need this line:

$myHash{anyArray} = [];

Thanks again.

 

[mikevh]

No. It's there for illustration purposes.
You could cut and paste the code and actually try it, you know ...

 

[naq2]

euh... yes! great idea!

but I'm in a very theoretical mood... I've just writen a 2000 lines program on paper... I'll start typing soon! lol!

Thanks anyway.

 

[PaulTEG]

naq,

y oh y did you write 2000 lines of code on paper, unless you're going to scan it in, of course ...

It isn't a handwriting recogniser is it?

;-) --Paul

It's important in life to always strike a happy medium, so if you see someone with a crystal ball, and a smile on their face ... smack the fecker

 

[naq2]

doh! I didn't though about this one!