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Acme-CPANModules-HashUtilities-0.003
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NAME

Acme::CPANModules::HashUtilities - Modules that manipulate hashes

VERSION

This document describes version 0.003 of Acme::CPANModules::HashUtilities (from Perl distribution Acme-CPANModules-HashUtilities), released on 2023-10-06.

DESCRIPTION

Most of the time, you don't need modules to manipulate hashes; Perl's built-in facilities suffice. The modules below, however, are sometimes convenient. This list is organized by task.

Creating an alias to another variable

Hash::Util's hv_store allows you to store an alias to a variable in a hash instead of copying the value. This means, if you set a hash value, it will instead set the value of the aliased variable instead. Copying from Hash::Util's documentation:

my $sv = 0;
hv_store(%hash,$key,$sv) or die "Failed to alias!";
$hash{$key} = 1;
print $sv; # prints 1

Getting internal information

Aside from creating restricted hash, Hash::Util also provides routines to get information about hash internals, e.g. hash_seed(), hash_value(), bucket_info(), bucket_stats(), etc.

Merging

Merging hashes is usually as simple as:

my %merged = (%hash1, %hash2, %hash3);

but sometimes you want different merging behavior, particularly in case where the same key is found in more than one hash. See the various hash merging modules:

Hash::Merge

Data::ModeMerge

Hash::Union

Providing default value for non-existing keys

Hash::WithDefault

Restricting keys

Perl through Hash::Util (a core module) allows you to restrict what keys can be set in a hash. This can be used to protect against typos and for simple validation. (For more complex validation, e.g. allowing patterns of valid keys and/or rejecting patterns of invalid keys, you can use the tie mechanism.)

Reversing (inverting)

Reversing a hash (where keys become values and values become keys) can be done using the builtin's reverse (which actually just reverse a list):

%hash = (a=>1, b=>2);
%reverse = reverse %hash; # => (2=>"b", 1=>"a")

Since the new keys can contain duplicates, this can "destroy" some old keys:

%hash = (a=>1, b=>1);
%reverse = reverse %hash; # => sometimes (1=>"b"), sometimes (1=>"a")

Hash::MoreUtil's safe_reverse allows you to specify a coderef that can decide whether to ignore overwriting, croak, or whatever else.

Slicing (creating subset)

Hash::MoreUtils's slice_* functions.

Hash::Subset

Hash::Util::Pick

Tying

The tie mechanism, although relatively slow, allows you to create various kinds of "magical" hash that does things whenever you get or set keys.

ACME::CPANMODULES ENTRIES

Hash::Util

Author: RJBS

Hash::Merge

Author: HERMES

Data::ModeMerge

Author: PERLANCAR

Hash::Union

Author: LONERR

Hash::WithDefault
Hash::MoreUtil
Hash::MoreUtils

Author: REHSACK

Hash::Subset

Author: PERLANCAR

Hash::Util::Pick

Author: PINE

FAQ

What is an Acme::CPANModules::* module?

An Acme::CPANModules::* module, like this module, contains just a list of module names that share a common characteristics. It is a way to categorize modules and document CPAN. See Acme::CPANModules for more details.

What are ways to use this Acme::CPANModules module?

Aside from reading this Acme::CPANModules module's POD documentation, you can install all the listed modules (entries) using cpanm-cpanmodules script (from App::cpanm::cpanmodules distribution):

% cpanm-cpanmodules -n HashUtilities

Alternatively you can use the cpanmodules CLI (from App::cpanmodules distribution):

% cpanmodules ls-entries HashUtilities | cpanm -n

or Acme::CM::Get:

% perl -MAcme::CM::Get=HashUtilities -E'say $_->{module} for @{ $LIST->{entries} }' | cpanm -n

or directly:

% perl -MAcme::CPANModules::HashUtilities -E'say $_->{module} for @{ $Acme::CPANModules::HashUtilities::LIST->{entries} }' | cpanm -n

This Acme::CPANModules module also helps lcpan produce a more meaningful result for lcpan related-mods command when it comes to finding related modules for the modules listed in this Acme::CPANModules module. See App::lcpan::Cmd::related_mods for more details on how "related modules" are found.

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/Acme-CPANModules-HashUtilities.

SOURCE

Source repository is at https://github.com/perlancar/perl-Acme-CPANModules-HashUtilities.

SEE ALSO

Acme::CPANModules::OrderedHash

Acme::CPANModules - about the Acme::CPANModules namespace

cpanmodules - CLI tool to let you browse/view the lists

AUTHOR

perlancar <perlancar@cpan.org>

CONTRIBUTING

To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

% prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps required beyond that are considered a bug and can be reported to me.

COPYRIGHT AND LICENSE

This software is copyright (c) 2023, 2020 by perlancar <perlancar@cpan.org>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Acme-CPANModules-HashUtilities

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.