Re: Perl programming question

[Michael G Schwern]

On 7/14/06, Alan Winston - SSRL Central Computing
<[EMAIL PROTECTED]> wrote:

Somebody who knows something should respond to this, really, but a WAG at how
to do this, if your hash is static once set up:

my $ordinal, $index, %ordinalhash, %indexhash;

$ordinal = 0;
foreach $index (sort keys %yourhash)  {
 $ordinal++;
 $ordinalhash{$ordinal} = $index;
 $indexhash($index) = $ordinal;
}


To get your "what is the next index after this index", you can do


$next_index = $ordinal_hash{$indexhash{$this_index}+1};

and for the previous index

$previous_index = $ordinal_hash{$indexhash{$this_index}-1};

There's already a couple modules on CPAN for this, Tie::Hash::Sorted
and Tie::SortHash do internally.  They likely do some variation of
your algorithm.
However, as they are tied, hash performance will be a smoking ruin.