references troubles

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

I've constructed a rather complex data structure, after reading in the perl book panther perl book I wanted to give it a shot (and using perl for 6 months )
I have a hash that used as a key a servername the value of the hash is a reference to an array that has 2 elements those are again 2 references to arrays the dump look like this,
the first one is a normal list the second one is again an array of arrays but I seem to have problems with my references.

I can traverse the code in a following mock up code.

<some make up code>
while(($key, $value) = each(%hservers)) {
  $hserver{$keyX}->[0]->[1] ="some value";
  $hserver{$keyX}->[1]->[0]->[0] ="1";    #secondpart
  $hserver{$keyX}->[1]->[0]->[1] =1;      #secondpart
  $hserver{$keyX}->[1]->[0]->[2] ="parX";  #secondpart  
}
</some make up code>
[download]

In this way I can build the structure completely the second part of the structure is build dynamically by my input/gui thingy :-).

Therefore the second part should be constructed by an init function.
My idea was to make a function and give the reference as argument.
And I need to be able to access the values later on too to add stuff , remove stuff from the structure by just passing the reference of the hash.

But in the init function I am not able to construct the code to traverse the hash and init it.

while(($key, $value) = each(%$href)) {
  %$href{$key}->[1]->[0]->[0] = 1; #this gives a syntax error
  %{$href{$key}}->[1]->[0]->[0] = "blah" #gives error
  print "$key\n";  # but when i do this the code prints all the keys o
+f the reference to the hash.  so I assume the the hash was passed thr
+ough correctly
}
[download]

Any pointers where I went wrong ?

dump of the hash

$VAR1 = 'server1';
$VAR2 = [
          [
            '',
            '4',
            '0',
            '0',
            '-1',
            '0',
            '',
            '0'
          ],
          [
            [
              1,
              1,
              'par 2'
            ],
            [
              2,
              999,
              'par 1'
            ]
          ]
        ];
$VAR3 = 'server2';
$VAR4 = [
          [
            '',
            '2',
            '0',
            '0',
            '-1',
            '0',
            '',
            '0'
          ],
          [
            [
              1,
              1,
              'par 2'
            ],
            [
              2,
              999,
              'par 1'
            ]
          ]
        ];
$VAR5 = 'server3';
$VAR6 = [
          [
            '',
            '3',
            '0',
            '0',
            '-1',
            '0',
            '',
            '0'
          ],
          [
            [
              1,
              1,
              'par 2'
            ],
            [
              2,
              999,
              'par 1'
            ]
          ]
        ];
[download]

CODE and READMORE tags added by Arunbear

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Replies are listed 'Best First'.
Re: references troubles by philcrow (Priest) on Sep 22, 2005 at 18:56 UTC
When refering to elements of hash, don't use the % sigil. In other words say something like: `$href->{name} = $value;` [download] When working with hashes use braces {}, not brackets []. Finally, you can omit all the -> except the first one: `$href->{name}{subkey}` [download] Phil	[reply] [d/l] [select]
Re: references troubles by graff (Chancellor) on Sep 22, 2005 at 19:34 UTC
This should work also -- the "$$href" part means that you are dereferencing $href and looking to identify a scalar value somewhere in the referenced structure; this way, you get to avoid using "->" altogether: `while(($key, $value) = each(%$href)) { $$href{$key}[1][0][0] = 1; ... print "$key/1/0/0 = $$href{$key}[1][0][0]\n"; }` [download] Note that if you wanted to refer to an entire array that is referenced in the structure, you need to use extra curly brackets around the expression that follows the @ sigil: `my @toparray = @{$$href{$key}}; my @midarray = @{$$href{$key}[1]}; my @endarray = @{$$href{$key}[1][0]};` [download]	[reply] [d/l] [select]
Re: references troubles by ysth (Canon) on Sep 23, 2005 at 06:05 UTC
Any pointers where I went wrong ? Assuming '%' is needed to dereference a hash reference. Instead, you just need to put the hash reference (e.g. $href) where you would normally put the name of the hash (where "name" means not including the $,@,% sigils). So where you'd say $hash{key}, you say $$href{key} (though $href->{key} also does the trick). See references quick reference for a quick runthrough of the possibilities.	[reply]