Question

Is there a “canonical” (pure-)perl implementation of a tree-based ordered key-value storage with O(log(n)) access time?

I’ve tried searching for “tree” on CPAN but haven’t got much insight from that.

This question inspired me to post my own.

EDIT: So the question was unclearly stated.

What I’m looking for is a storage that barely does what a %hash would do, but maintains the order of its keys at a price of worse algorithmic complexity. All structures with such properties I know so far are based on some kind of tree (B-tree, red-black tree etc), hence the title.

Here’s a pseudocode example of what I’d like to see:

my $set = Some::Module->new();
$set->store( foo=>1 );
$set->store( bar=>2 );
$set->fetch( "foo" ); # 1
$set->keys(); # bar, foo and not foo, bar
$set->keysBetween( undef, "baz" ); # bar only

Answer 1

Tie::IxHash is the perlfaq4 recommendation:

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,...)

DESCRIPTION

This Perl module implements Perl hashes that preserve the order in
which the hash elements were added. The order is not affected when
values corresponding to existing keys in the IxHash are changed. The
elements can also be set to any arbitrary supplied order. The familiar
perl array operations can also be performed on the IxHash.

Also try searching for “tie hash order” on CPAN if this module doesn’t cut the mustard.