The only script-visible changes would be the module you include to say you want sorted hashes

and the function it exports so you 'seek' the each operator.

It'd seek to a particular key value. There are certainly trees that would also allow seeking to a particular index. I don't care whether there is a way to override the default comparison function (just cmp).

Yes, using an attribute for this would be fine.

Update: s/<=>/cmp/.

- tye        

use strict;
use warnings;
use feature 'say';
use Tree::RB;

my $tied = tie(my %capital, 'Tree::RB');
%capital = (
    France  => 'Paris',
    England => 'London',
    Hungary => 'Budapest',
    Ireland => 'Dublin',
    Egypt   => 'Cairo',
    Germany => 'Berlin',
);

say 'Countries starting from Germany:';
$tied->hseek('Germany');
while(my ($key, $val) = each %capital) {
    say "key: $key, val: $val";
} 

say "\nCountries in reverse:";
$tied->hseek({-reverse=> 1});
while(my ($key, $val) = each %capital) {
    say "key: $key, val: $val";
}
[download]

Countries starting from Germany:
key: Germany, val: Berlin
key: Hungary, val: Budapest
key: Ireland, val: Dublin

Countries in reverse:
key: Ireland, val: Dublin
key: Hungary, val: Budapest
key: Germany, val: Berlin
key: France, val: Paris
key: England, val: London
key: Egypt, val: Cairo
[download]

'seek' doesn't care whether the key exists or not. It just arranges for the next use of each (actually, adding a way to reverse 'each' would be prudent as well) finds the earliest key greater than or equal to the key given to 'seek'. For convenience of interface, 'seek' might return something which might be different depending on whether the requested key exists or not, but those are details best left to the (unknown) implementor.

- tye        

But say you have a hash like

%capital = (
    France  => 'Paris',
    England => 'London',
    Hungary => 'Budapest',
);
[download]

and you seek to 'Russia'. Should the next call to each behave as if all the elements had been read (i.e. return end-of-hash) ?