help needed in retrieving the hash key

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

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Re: help needed in retrieving the hash key by murugu (Curate) on Apr 05, 2006 at 09:51 UTC
Hi, As you mentioned that keys and values are unique, `my %hash2 = reverse %hash1;` [download] Now the keys and values got interchanged. Regards, Murugesan Kandasamy use perl for(;;);	[reply] [d/l]
Re: help needed in retrieving the hash key by tirwhan (Abbot) on Apr 05, 2006 at 09:52 UTC
`%reverse_hash = reverse %original_hash` For more, see `perldoc -q "hash element by value"</p>` All dogma is stupid.	[reply] [d/l] [select]
Re: help needed in retrieving the hash key by inman (Curate) on Apr 05, 2006 at 11:38 UTC
An alternative method uses the each and keys functions to iterate over a hash and locate the keys. This has the advantage of coping with the more general case wher multiple instances of a value in addition to not requiring the storage of another hash. `my @keys = qw ( a b c d e f g h i j); my @vals = qw ( 1 1 1 4 5 6 7 8 9 0); my %hash; @hash{@keys} = @vals; my @ones = grep {(each %hash)[1] == 1} keys %hash; print "@ones\n";` [download] Inverting the hash as shown previously is a better method if you are OK with the storage overhead and you will be doing multiple retrievals.	[reply] [d/l]
Re: help needed in retrieving the hash key by jwkrahn (Abbot) on Apr 05, 2006 at 13:38 UTC
`$ perl -le' my %x = qw/ one two three four five six seven eight /; print ${ { reverse %x } }{ six }; ' five` [download]	[reply] [d/l]


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