in reply to Re^4: Tie::Hash::MultiValue Unique question
in thread Tie::Hash::MultiValue Unique question

Oh! You keep talking about avoiding duplicates in a hash, but your problem is actually with avoiding duplicates in an array.

A common idiom to weed out duplicates is: (from perlfaq4) 

my %seen;
my @array = grep !$seen{$_}++, LIST;

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To insert at the same time, that would be 

my %seen;
my @array = grep !$seen{$_}++, @array, $new_value;

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Plug it in and get: 

my %edges;
while (<STREAM>) {
   my($node1, $node2) = split;
   my %seen;
   @{$edges{$node1}} = grep !$seen{$_}++, @{$edges{$node1}}, $node2;
}

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A faster (but more memory hungry) version would be: 

my %edges;
my %seen;
while (<STREAM>) {
   my($node1, $node2) = split;
   next if !$seen{$node1}{$node2}++;
   push @{$edges{$node1}}, $node2;
}

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Re^6: Tie::Hash::MultiValue Unique question
by elsubliminal (Initiate) on Apr 18, 2009 at 07:15 UTC
    Ahh Yes! Thanks for someone still making sense out of my
    pitifully worded question!
    The point is that I want to avoid duplicates in values, not keys.
    When googled this bit, I found out I could use Tie::Hash::Multivalue
    for ensuring I can add multiple values
    to a key in the hash, and I can pass an argument
    'Unique' to ensure that only unique values get added.
    So that was my original question - how do I pass the argument
    "unique" to Tie::Hash::Multivalue?

    Thanks all for responding!
[reply]
      # Uses string compare to determine uniqueness.
tie %hash, 'Tie::Hash::MultiValue', 'unique';

# Uses numerical compare to determine uniqueness.
tie %hash, 'Tie::Hash::MultiValue', unique => sub { $_[0] == $_[1] };

      [download]
[reply]
[d/l]
        Thanks Much!
[reply]

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