How can I extract hash values into an array in their insertion order?

Question

Given a hash in Perl (any hash), how can I extract the values from that hash, in the order which they were added and put them in an array?

Example:

my %given = ( foo => '10', bar => '20', baz => '15' );

I want to get the following result:

my @givenValues = (10, 20, 15);

Answer 1

You can use values , but I think you can't get them in the right order , as the order has been already lost when you created the hash

Answer 2

The following will do what you want:

my @orderedKeys = qw(foo bar baz);
my %records     = (foo => '10', bar => '20', baz => '15');

my @givenValues = map {$records{$_}} @orderedKeys;

NB: An even better solution is to use Tie::IxHash or Tie::Hash::Indexed to preserver insertion order.

Answer 3

If you have a list of keys in the right order, you can use a hash slice:

 my @keys   = qw(foo bar baz);
 my %given  = {foo => '10', bar => '20', baz => '15'}
 my @values = @given{@keys};

Otherwise, use Tie::IxHash.

Answer 4

From perldoc perlfaq4: How can I make my hash remember the order I put elements into it?

---

Use the Tie::IxHash from CPAN.

use Tie::IxHash;
tie my %myhash, 'Tie::IxHash';

for (my $i=0; $i<20; $i++) {

    $myhash{$i} = 2*$i;
}

my @keys = keys %myhash;
# @keys = (0,1,2,3,...)