NAME

SortKey - Reusable sort key generators

SPECIFICATION VERSION

0.1

VERSION

This document describes version 0.1.1 of SortKey (from Perl distribution SortKey), released on 2024-02-14.

SYNOPSIS

Basic use with sort():

 use SortKey::Num::length;
 my $by_length = SortKey::Num::length::gen_keygen;

 my @sorted = sort { $by_length->($a) <=> $by_length->($b) } "food", "foo", "foolish";
 # => ('foo', 'food', 'foolish')

Basic use with Sort::Key:

 use Sort::Key qw(nkeysort);
 use SortKey::Num::length;
 my $by_length = SortKey::Num::length::gen_keygen;

 # use & prefix to get around prototype restriction
 my @sorted = &nkeysort($by_length, "food", "foo", "foolish");
 # => ('foo', 'food', 'foolish')

Specifying arguments:

 use Sort::Key qw(nkeysort);
 use SortKey::Num::pattern_count;
 my $by_pattern_count = Sort::Key::Num::pattern_count::gen_keygen(pattern => qr/foo/);
 my @sorted = &nkeysort($by_pattern_count, ...);

Specifying comparer on the command-line (for other CLI's):

 % customsort -k length ...
 % customsort -c pattern_count=pattern,foo ...

DESCRIPTION

EXPERIMENTAL. SPEC MIGHT STILL CHANGE.

Glossary

A sort key generator is a subroutine that accepts an item and converts it to a string/numeric key. The key then can be compared using <=> or cmp operator.

A SortKey::* module is a module that can return a sort key generator.

Writing a SortKey module

 package SorKey::Num::pattern_count;

 # required. must return a hash (DefHash)
 sub meta {
     return +{
         v => 1,
         summary => 'Number of occurrences of a pattern, as sort key',
         args => {
             pattern => {
                 schema => 're_from_str*', # Sah schema
                 req => 1,
             },
         },
     };
 }

 sub gen_keygen {
     my %args = @_;
     ...
 }

 1;

Namespace organization

SortKey::Num::* are for modules that return a numeric key generator. Other subnamespaces are for modules that return a string key.

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/SortKey.

SOURCE

Source repository is at https://github.com/perlancar/perl-SortKey.

SEE ALSO

Base specifications

DefHash

Sah

Related specifications

Sorter

Comparer

Previous incarnation

Sort::Sub

Sorter, SortKey, and Comparer are meant to eventually supersede Sort::Sub. The main improvement over Sort::Sub is the split into three kinds of subroutines:

1. sorter

A subroutine that accepts a list of items to sort.

Sorter::* modules are meant to generate sorters.

2. sort key generator

A subroutine that converts an item to a string/numeric key suitable for simple comparison using eq or == during sorting.

SortKey::* modules are meant to generate sort key generators.

3. comparer

A subroutine that compares two items. Can be used in sort() as custom sort block.

Comparer::* modules are meant to generate comparers.

Perl's sort(), as mentioned above, allows us to specify a comparer, but oftentimes it's more efficient to sort by key using key generator, where the keys are often cached. And sometimes due to preprocessing and/or postprocessing it's more suitable to use the more generic sorter interface.

Aside from the above, SortKey also makes Sort::Sub's special arguments reverse and is_ci become ordinary arguments, because they are not always applicable in all situation, especially is_ci.

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) 2024 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=SortKey

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.

cpanm SortKey

perl -MCPAN -e shell
install SortKey