in reply to Re^2: Common hash keys
in thread Common hash keys

(: Indeed! (But I did not write Perl, did I?)

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Re^4: Common hash keys
by massa (Hermit) on Jun 07, 2008 at 13:34 UTC
    Maybe 
    my @keys_in_commmon =
  grep $hashref1->{$_}, keys %$hashref2;

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    would've sufficed?? If you just have to determine if they have keys in common, 
    if( grep $hashref1->{$_}, keys %$hashref2 ) { ... }

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    would do the trick...
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[d/l]
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      I would say  my @keys_in_commmon = grepexists($hashref1->{$_}), keys %$hashref2; to avoid autovivification.
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[d/l]
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        massa's code does not actually cause autovivification (perl 5.8.8) ... 

        use warnings; use strict;
use Data::Dumper;

my %p;
my %q = ( 1 => undef );

print Dumper( 'before', \%p );

my $r = grep $p{ $_ }, keys %q;

print Dumper( 'after', \%p );

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        ... I was also suspicious of autovivification but had to test that myself.

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[d/l]
        The exists test is so that the case where a key has undef as a value, not to aviode auto vivification. Undef itself cannot be a key in a hash. But '0' and '' can.
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