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

hi brothers, This might sound stupid but, how do I get the key name of my array using a loop? let's say theres : 
my @item;
my $val;

$item["A"] = (["dunno", "i think so"]);
$item["B"] = (["okay", "duh"]);

foreach $val(@item){

  #$val holds array A and B's 0 position,
   but no other parameters to get its key name instead.

}

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unlike php, where i could actually do this : 
foreach($item as $key=>$value)
    {
    
      //where $key is keyname, and $value is the value
    }

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anyway to do this..without asking me to change it to hashes?

Replies are listed 'Best First'.
Re: how to get array's key name?
by Corion (Patriarch) on Feb 22, 2008 at 08:55 UTC

    Perl arrays cannot be indexed by strings. If you had #!/usr/bin/perl -w or use warnings;, Perl would have told you so. If you need strings as keys, you need a hash. But you need to know that hash keys are unordered. If you need a hash where the hash keys are in an order specified by you, either use a parallel hash and an array for the keys, or use Tie::IxHash.

    If you just want to iterate over the keys and values of a hash, just use the each keyword, but you need to store your data in a hash, still.

    my %item;

$item{"A"} = ["dunno", "i think so"];
$item{"B"} = ["okay", "duh"];

foreach $val (keys %item) {
    print "$val => @{ $item{$val}}\n";
}

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Re: how to get array's key name?
by wfsp (Abbot) on Feb 22, 2008 at 11:31 UTC
    Generally, a good rule of thumb is
    • if order is important use an array
    • if a 'lookup' is important use a hash
    It is possible to combine the two with an array of hashes (AoH). And you can use perl's each to get at the key/value pairs in the hashes. 
    #!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
$Data::Dumper::Indent = 1;
$Data::Dumper::Sortkeys = 1;

my @db = (
  {one   => q{red}},
  {two   => q{green}},
  {three => q{blue}},
);

#print Dumper \@db;

for my $rec (@db){
  my ($key, $value);
  while (($key, $value) = each %{$rec}){
    print qq{$key -> $value\n};
  }
}

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    produces: 
    one -> red
two -> green
three -> blue

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Re: how to get array's key name?
by adrive (Scribe) on Feb 22, 2008 at 09:07 UTC
    thanks, im just too used to using associative arrays. I'll change it to hashes tehn.
[reply]
      "associative arrays" is another name for "hash", but awfully long to write :o)
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