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Re: HASH Array advice

by serf (Chaplain)
on Jan 24, 2006 at 11:46 UTC ( #525160=note: print w/replies, xml ) Need Help??

in reply to HASH Array advice

There's no specific reason not to.

If you are only making a small hash (with low numbers) you may find that an array is easier and more efficient *but* there are benefits in using a hash this way over using an array:

Particularly if you have to use a very large index number in the array; I believe that an array is created with (empty where not defined) elements up to the size of the highest index number, so by using a large index number you are pre-allocating (and therefore wasting) a chunk of un-needed memory.

On the other hand with an array you can just do:

for my $element (@array)
and get all the elements back in order (which may or may not be useful in the case you are looking at), whereas with a hash you would have to sort the keys:
for my $key (sort keys %hash)
or explicitly ask for them:
for my $key (@array_of keys)
(which obviously means using a hash *and* an array!) because a hash does not store the keys (or values) in numerical order.

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