delete on tied variables

cmac has asked for the wisdom of the Perl Monks concerning the following question:

I'm writing a module that implements tied interfaces. The description of the tied interface describes the DELETE function for both arrays and hashes as applying to only one entry/element.

The description of the delete function says that it can be used on a "hash element, array element, hash slice, or array slice".

Q1: What is a hash slice and how is one written in Perl?

Q2: if a delete function in a Perl program specifies a slice, will the interpreter break it up into individual calls to DELETE?

Q3: if not, what are the operands to DELETE that express a slice, for both an array and a hash?

If there are other pages that cover this subject, please tell me.

Thanks be to Perl Monks,
cmac
www.animalhead.com

Comment on delete on tied variables

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Re: delete on tied variables by ikegami (Patriarch) on Jan 12, 2009 at 03:38 UTC
What is a hash slice and how is one written in Perl? A means of selecting multiple elements for fetching or setting. An example would be `@hash{ 'key1', 'key2', ... }`. See perldata for details. if a delete function in a Perl program specifies a slice, will the interpreter break it up into individual calls to DELETE? Yes. `{ package Tester; use Tie::Hash qw(); our @ISA = 'Tie::StdHash'; sub DELETE { my $self = shift; print("DELETE @_\n"); $self->SUPER::DELETE(@_) } } { tie my %hash, 'Tester'; %hash = ( a => 1, b => 2, c => 3, d => 4, ); delete @hash{qw( b c )}; print(join(' ', keys %hash), "\n"); }` [download] `DELETE b DELETE c a d` [download] If there are other pages that cover this subject, please tell me. tie Tie::Scalar Tie::Array Tie::Hash Tie::Handle Update: Formatting changes. Switched from using array to using hash in `DELETE` test.	[reply] [d/l] [select]
Re: delete on tied variables by dragonchild (Archbishop) on Jan 12, 2009 at 16:45 UTC
Perl is opensource. As such, there are dozens of modules on CPAN that use tying. One example is DBM::Deep. It implements tying for both arrays and hashes and it implements (nearly) every single method that the tie interface provides for arrays and hashes. If DBM::Deep doesn't do it or worry about it, then it's probably not something you need to worry about. (If I'm mistaken, I need to know cause it's a bug in DBM::Deep!) My criteria for good software: Does it work? Can someone else come in, make a change, and be reasonably certain no bugs were introduced?	[reply]