Get Unique list of values from array inside hash perl

Question

I have a hash which contains a list of array and i have to get a unique list from that array . But when i am trying to id i am not getting any error or the unique list.

NOTE : I don't want to use any module.

Below is the sample structure of my hash which has the array :

'15445' => { 'str' => {
                        'TOKEN' => [
                           'HC',
                           'HC',
                           'HC',
                           'HC',
                           'HC',
                           'HC'
                            ]
                }
        }

How i am tying to get a unique list of values from the array TOKEN

foreach my $id (keys %$client) {
    my @unique_srp_id;
    @unique_srp_id = uniq($hash->{$id}->{str}->{TOKEN});
    print @unique_srp_id;
}

sub uniq {
    my %seen;
    grep !$seen{$_}++, @_;
}

Can anyone suggest me what wrong i am doing here.

Consider passing references (for arrays/hashes) instead of flat lists — zdim
– zdim, Commented Feb 11, 2019 at 21:39
@zdim, hmm... Taking an arbitrary number of scalars is far more useful for uniq. — ikegami
– ikegami, Commented Feb 12, 2019 at 1:46
@ikegami As a ("far") more common use case (a handful of scalars to clean up)? Right, good point. I just get all itchy when I see multi-valued variables passed around subs freely, for fear of stack abuse or unintended flattening (and out of habits from elsewhere I guess). — zdim
– zdim, Commented Feb 13, 2019 at 20:18

Grinnz · Accepted Answer · 2019-02-11 21:24:01Z

4

You are passing an array reference containing the values to the function, but the function is expecting the values directly in @_.

my @unique = uniq(@{$hash->{$id}{str}{TOKEN}});

On Perl 5.24+, you can use postderef to make this look a bit nicer (maybe?)

my @unique = uniq($hash->{$id}{str}{TOKEN}->@*)

On Perl 5.26+, the core version of List::Util is new enough (1.45) to contain the uniq function and it will be faster than your pure-perl version and also handle undef values distinctly.

answered Feb 11, 2019 at 21:24

Grinnz

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Comments

mob · Accepted Answer · 2019-02-11 21:25:17Z

2

uniq expects a list but $hash->{$id}->{str}->{TOKEN} is an array reference (a single element). Either pass an array to uniq

 uniq(@{$hash->{$id}{str}{TOKEN}})

or write uniq to expect an array reference

sub uniq {
    my %seen;
    grep !$seen{$_}++, @{$_[0]};
}

answered Feb 11, 2019 at 21:25

mob

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