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| author | Yitzchak Scott-Thoennes <sthoenna@efn.org> | 2003-05-07 08:27:07 -0700 |
|---|---|---|
| committer | Jarkko Hietaniemi <jhi@iki.fi> | 2003-05-08 18:12:46 +0000 |
| commit | 126c71c82576d5dc652db25ca9e3f8e18442c4fd (patch) | |
| tree | e2790a78faaa94be96e8fcce8035cddddae1602e /pod | |
| parent | 86e5a81e88dbe10bf1c195d6ca6fefab8bfafc17 (diff) | |
| download | perl-126c71c82576d5dc652db25ca9e3f8e18442c4fd.tar.gz | |
Re: [perl #17718] %tiedhash in bool context doesn't check if hash is empty
Message-ID: <7gYu+gzkgaFU092yn@efn.org>
p4raw-id: //depot/perl@19452
Diffstat (limited to 'pod')
| -rw-r--r-- | pod/perldata.pod | 4 | ||||
| -rw-r--r-- | pod/perldiag.pod | 8 | ||||
| -rw-r--r-- | pod/perltie.pod | 8 |
3 files changed, 19 insertions, 1 deletions
diff --git a/pod/perldata.pod b/pod/perldata.pod index 572058924f..c58d41974a 100644 --- a/pod/perldata.pod +++ b/pod/perldata.pod @@ -257,7 +257,9 @@ 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 C<"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. +10,000 of your items. This isn't supposed to happen. If a tied hash +is evaluated in scalar context, a fatal error will result, since this +bucket usage information is currently not available for tied hashes. 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: diff --git a/pod/perldiag.pod b/pod/perldiag.pod index b6558ec998..ad5841ca34 100644 --- a/pod/perldiag.pod +++ b/pod/perldiag.pod @@ -912,6 +912,14 @@ for stdout. (F) The script you specified can't be opened for the indicated reason. +=item Can't provide tied hash usage; use keys(%hash) to test if empty + +(F) When a hash is evaluated in scalar context, bucket usage is +returned if the hash is populated, and false is returned if the hash +is empty. Bucket usage is not currently available for tied hashes. +To test if a hash is empty or populated, use keys(%hash) in scalar +context instead. + =item Can't read CRTL environ (S) A warning peculiar to VMS. Perl tried to read an element of %ENV diff --git a/pod/perltie.pod b/pod/perltie.pod index 05b79730c3..3665f0420e 100644 --- a/pod/perltie.pod +++ b/pod/perltie.pod @@ -1076,6 +1076,14 @@ source code to MLDBM. Tied filehandles are still incomplete. sysopen(), truncate(), flock(), fcntl(), stat() and -X can't currently be trapped. +The bucket usage information provided by C<scalar(%hash)> is not +available. If C<%hash> is tied, this will currently result in a +fatal error. + +Counting the number of entries in a hash via C<scalar(keys(%hash))> or +C<scalar(values(%hash)>) is inefficient since it needs to iterate +through all the entries with FIRSTKEY/NEXTKEY. + =head1 AUTHOR Tom Christiansen |