Kamal Ahmed wrote:
> Hi Perl Group,
> How can I get number of objects in a hash ?
perlfaq4:
How can I know how many entries are in a hash?
If you mean how many keys, then all you have to do is take the scalar sense
of the keys() function:
$num_keys = scalar keys %hash;
The keys() function also resets the iterator, which in void context is
faster for tied hashes than would be iterating through the whole hash, one
key-value pair at a time.
perldata (hash storage info):
If you evaluate a hash in scalar context, it returns false if the hash is
empty. If there are any key/value pairs, it returns true; more precisely,
the value returned is a string consisting of the number of used buckets and
the number of allocated buckets, separated by a slash. This is pretty much
useful only to find out whether Perl's internal hashing algorithm is
performing poorly on your data set. For example, you stick 10,000 things in
a hash, but evaluating %HASH in scalar context reveals ""1/16"", which means
only one out of sixteen buckets has been touched, and presumably contains
all 10,000 of your items. This isn't supposed to happen.
You can preallocate space for a hash by assigning to the keys() function.
This rounds up the allocated buckets to the next power of two:
keys(%users) = 1000; # allocate 1024 buckets
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