Re^2: How to get Keys from hash having same value?

Or, to avoid the extra hash lookups, iterate over key-value pairs using each.

my @as = ();
while (my ($key, $value) = each %myhash){
   push @as, $key if $value eq 'a';
}
[download]

Update:

Is there a monk among us who can shorten this into a one-liner, similar to the grep keys examples we have seen?

It seems that each does not combine nicely with grep, map and their ilk.

Comment on Re^2: How to get Keys from hash having same value? Select or Download Code

Replies are listed 'Best First'.
Re^3: How to get Keys from hash having same value? by shmem (Chancellor) on Jan 07, 2008 at 14:19 UTC
Voilà: `%newhash = reverse do { my $hash = reverse %myhash; %hash };` [download] To get the keys only (which are the values in the reversed hash: `@unique_keys = do { my $hash = reverse %myhash; values %hash };` [download] update: oops, got it all wrong. It' about getting all keys where duplicate values are found. As a single statement, formatted for readability `%myhash = (1 => 'a', 2=> 'b', 3=> 'a', 4=>'c',5 => 'b', 6 => 'a'); @k = do { my %s; map { my $v=$_; grep { $myhash{$_} eq $v} keys %myhash } grep {$s{$_}++==1} values %myhash }; print "$_ => $myhash{$_}\n" for @k; __END__ 6 => a 1 => a 3 => a 2 => b 5 => b` [download] Ah well. Readability... ;-) --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l] [select]
Re^3: How to get Keys from hash having same value? by targetsmart (Curate) on Jun 03, 2008 at 13:22 UTC
I tried doing that, It is working. `use Data::Dumper; %myhash = ( 1 => 'a', 2=> 'b', 3=> 'a', 4=>'c', 5 => 'a', 6 => 'a', 7 +=>'b'); %newhash = map { ($_,$myhash{$_}) } grep { $myhash{$_} eq 'a'; } keys + %myhash ; print Dumper \%newhash;` [download]	[reply] [d/l]