NAME

Comparer - Reusable comparer subroutines

SPECIFICATION VERSION

0.1

VERSION

This document describes version 0.1.1 of Comparer (from Perl distribution Comparer), released on 2024-01-23.

SYNOPSIS

Basic:

 use Comparer::naturally;
 my $cmp = Comparer::naturally::gen_comparer;

 my @sorted = sort { $cmp->($a,$b) } ('track1.mp3', 'track10.mp3', 'track2.mp3', 'track1b.mp3', 'track1a.mp3');
 # => ('track1.mp3', 'track1a.mp3', 'track1b.mp3', 'track2.mp3', 'track10.mp3')

Specifying arguments:

 use Comparer::naturally;
 my $cmp = Comparer::naturally::gen_comparer(reverse => 1);
 my @sorted = sort { $cmp->($a,$b) } ...;

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

 % customsort -c naturally ...
 % customsort -c naturally=reverse,1 ...

DESCRIPTION

EXPERIMENTAL. SPEC MIGHT STILL CHANGE.

Glossary

A comparer is a subroutine that accepts two items to be compare and return a value of either -1/0/1. So in other words, just like Perl's cmp or <=>.

A comparer module is a module under the Comparer::* namespace that you can use to generate a comparer.

Writing a Comparer module

 package Comparer::naturally;

 # required. must return a hash (DefHash)
 sub meta {
     return +{
         v => 1,
         args => {
             reverse => {
                 schema => 'bool*', # Sah schema
             },
         },
     };
 }

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

 1;

Namespace organization

HOMEPAGE

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

SOURCE

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

SEE ALSO

Base specifications

DefHash

Sah

Related specifications

Sorter

SortKey

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, Comparer 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=Comparer

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 Comparer

perl -MCPAN -e shell
install Comparer