How to efficiently get an array of values from a referenced hash and an array of keys in perl?

Question

I currently have an referenced hash and an array of keys that the hash contains. I want to get an array of the values corresponding to my array of keys.

I know how to do this in multiple lines:

# Getting hash reference and array of keys.
my $hashRef = {
    one   => 'foo',
    two   => 'bar',
    three => 'baz'
};
my @keys = ('one', 'three');

# Getting corresponding array of values.
my @values;
foreach my $key (@keys) {
    push @values, $hashRef->{$key};
}

However, I believe that there must be a much better way that doesn't make use of a loop. But unfortunately I just can't figure it out. How can I efficiently get an array of values from a referenced hash and an array of keys; ideally in one line if possible?

mwp · Accepted Answer · 2017-11-30 21:30:42Z

5

Easily:

my @values = @$hashRef{@keys};

Or, on Perl 5.24+:

my @values = $hashRef->@{@keys};

Or, on Perl 5.20+ by enabling some additional features:

use feature qw(postderef);
no warnings qw(experimental::postderef);

my @values = $hashRef->@{@keys};

This takes advantage of the fact that you can get the values for multiple keys (a "slice") of a %hash with the @hash{LIST} syntax. You just have to dereference it first. See perldoc for more information.

edited Nov 30, 2017 at 21:30

answered Nov 30, 2017 at 21:09

mwp

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3 Comments

J0HN_TIT0R Over a year ago

Would this work the same? I prefer to use arrow notation: @{ $hashRef->{@keys} }

J0HN_TIT0R Over a year ago

Ah I see, but this will still be equivalent right: @{ $hashRef }{@keys}

mwp Over a year ago

Yup. You've got it.

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