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Re: Seeking explanation on assigning a hash to a scalar

by Samy_rio (Vicar)
on May 15, 2007 at 03:53 UTC ( #615452=note: print w/replies, xml ) Need Help??


in reply to Seeking explanation on assigning a hash to a scalar

Hi jesuashok, It means "Number of used buckets and the number of allocated buckets, separated by a slash." ( Ex.: 4/8 ).

In \html\lib\Pod\perldata.html, description as,

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

Regards,
Velusamy R.


eval"print uc\"\\c$_\""for split'','j)@,/6%@0%2,`e@3!-9v2)/@|6%,53!-9@2~j';

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