My approach with such things is to use a tied hash (Berkeley DB in my case), and to pack and unpack the flag and count. It works well enough and is simple enough so I don't make ugly programming errors:

my $mask = "NN";
foreach my $item (LARGE_LIST) {
    $key = property($item);
    my $val = $record{ $key } || pack $mask, 0,0;
    my ($count, $flag) = unpack $mask, $val;
    $count++;
    $flag ||= condition_is_true($item);
    $record{ $key } = pack $mask, $count, $flag;
}

[download]

Even without using a tied hash, you'll almost cut your memory use by half as you don't need to allocate the anonymous hash and the scalar for the flag anymore.

In reply to Re: How to create a compact data structure? by Corion
in thread How to create a compact data structure? by bart

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