Seemingly enigmatic data structures

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

Hello monks.

I was reading some code this afternoon:

#!/usr/bin/perl
use warnings;

my @staff = ( 
             { 
               age      => 21,
               position => 'programmer',
             },

             {  
               age      => 23,
               position => 'administrative assistant',
             },
            );
[download]

Ok. I understand that the 'staff' array contains two anonymous hashes (indexed as '0' and '1' respectively). If I wanted to obtain the value of the 'age' key in the second hash, I could write:

print $staff[1]->{age};
[download]

I decided to experiment with this code slightly and enclose each anonymous hash within an anonymous array:

my @staff = ( 
             [{ 
               age      => 21,
               position => 'programmer',
             }],

             [{  
               age      => 23,
               position => 'administrative assistant',
             }],
            );
[download]

After doing so, I wasn't sure how to describe such a structure nor how to obtain the values stored within each respective hash.

Any help?

Thank you monks,

Linda

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Re: Seemingly enigmatic data structures by lidden (Curate) on Mar 05, 2005 at 05:19 UTC
You get anonymous arrays with one element each. The following two do the same. `print $staff[0][0]{age}, "\n"; print $staff[0]->[0]->{age}, "\n";` [download]	[reply] [d/l]
Re: Seemingly enigmatic data structures by Prior Nacre V (Hermit) on Mar 05, 2005 at 06:34 UTC
Linda, In this context using arrays and hashes, the -> operator: must be used in one place must not be used in one place may be used everywhere else must It must be used to access the first data structure level of a reference to an array: `my $ra_staff = \@staff; $ra_staff->[0]...` [download] must not It must not be used to access the first data structure level of an array: `$staff[0]...` [download] may It is optional everywhere else: as shown by lidden above. Regards, PN5	[reply] [d/l] [select]
Re^2: Seemingly enigmatic data structures by tphyahoo (Vicar) on Mar 05, 2005 at 12:16 UTC
must be used in one place must not be used in one place isn't this a contradiction? UPDATE: Ah, OK, I get it now, more or less. Though I do think that could have been more clearly worded. "...first data structure level of a reference" is pretty gibberishy to me. But the examples make it more or less clear.	[reply]
Re^3: Seemingly enigmatic data structures by merlyn (Sage) on Mar 05, 2005 at 13:55 UTC
Another simpler rule is: Arrows are optional between subscripty kinds of things (brackets, braces, parens). -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re^4: Seemingly enigmatic data structures by tphyahoo (Vicar) on Mar 05, 2005 at 17:39 UTC
Re^5: Seemingly enigmatic data structures by Joost (Canon) on Mar 05, 2005 at 18:01 UTC
Re: Seemingly enigmatic data structures by sh1tn (Priest) on Mar 05, 2005 at 13:37 UTC
In addition: `# in order to see stucture: use Data::Dumper; my @staff = ( [{ age => 21, position => 'programmer', }], [{ age => 23, position => 'administrative assistant', }], ); print Dumper(@staff);` [download]	[reply] [d/l]