NAME

Acme::CPANModules::SmartMatch - List of modules to do smart matching

VERSION

This document describes version 0.003 of Acme::CPANModules::SmartMatch (from Perl distribution Acme-CPANModules-SmartMatch), released on 2023-11-05.

DESCRIPTION

About smart match

Smart matching, via the operator ~~, was introduced in perl 5.10 (released 2007). It's probably inspired by Perl 6 (now called Raku)'s given/when and/or Ruby's case and === operator that can "do the right/smart thing" in a case statement. Smart matching was indeed introduced along the new switch in perl 5.10.

What can smart match do? A whole lot. It can do string equality like eq if given a string on the left hand side and a string on the right hand side. Or it can do numeric equality like == when both sides are numbers. It can do regex matching like =~ if the left hand side is a scalar and the right hand side is a regexp.

But wait, there's (much) more. Interesting things begin when the left/right hand side is an array/hash/code/object. $str ~~ @ary, probably the most common use-case for smart matching, can do value-in-array checking, equivalent to grep { $str eq $_ } @ary but with short-circuiting capability. Then there's $re ~~ @ary which can perform regex matching over the elements of array. Now what about when the right hand side is an arrayref or hashref? Or the left hand side? What if the array is an array of regexes? Or a mix of other types?

You need a full-page table as a reference of what will happen in smart matching, depending on the combination of operands. Things got complex real fast. Behaviors were changed from release to release, starting from 5.10.1. Then nobody was sure what smart matching should or should not do exactly.

In the end almost everyone agrees that smart matching is a bad fit for a weakly typed language like Perl. The programmer needs to be explicit on what type of operation should be done by specifying the appropriate /operator/ (e.g. == vs eq) instead of the operator deducing what operation needs to be done depending on the operand, because in Perl the operand's type is unclear. Mainly, a scalar can be a string, or a number, or a bool, or all.

The roadmap to removal

In perl 5.18 (2013), 6 years after being introduced and used by programmers without warning, smart match was declared as experimental, which is weird if you think about it. You now have to add use experimental "smartmatch" to silence the warning. What happens to the switch statement then? Since it's tied to smart matching, it also gets the same fate: became experimental in 5.18.

In perl 5.38 (2023) smart match is deprecated. You can no longer silence the warning with "use experimental 'smartmatch'" and must replace the use of smart match with something else.

Perl 5.40 (planned 2024) will remove smart match, resulting in a syntax error if you still use it.

Modules

However, if you still miss smart matching, some modules have been written to give you somewhat similar feature.

match::smart (as |M| operator or as function match) gives you a similar behaviour to perl's own ~~.

match::simple, also by the author of match::smart, offers a simplified version of smart matching. Still it has 8 kinds of behavior depending on the /right/ hand side.

Also see match::simple::sugar which gives you when, then, and numeric for use in a for() statement as a switch/use alternative.

Smart::Match offers a bunch of functions related to matching. Probably too low-level to use if you just want a smart match replacement.

ACME::CPANMODULES ENTRIES

match::smart: Author: TOBYINK
match::simple: Author: TOBYINK
match::simple::sugar: Author: TOBYINK
Smart::Match: Author: LEONT

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 SmartMatch

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

    % cpanmodules ls-entries SmartMatch | cpanm -n

or Acme::CM::Get:

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

or directly:

    % perl -MAcme::CPANModules::SmartMatch -E'say $_->{module} for @{ $Acme::CPANModules::SmartMatch::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-SmartMatch.

SOURCE

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

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 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-SmartMatch

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.

To install Acme::CPANModules::SmartMatch, copy and paste the appropriate command in to your terminal.

cpanm

cpanm Acme::CPANModules::SmartMatch

CPAN shell

perl -MCPAN -e shell
install Acme::CPANModules::SmartMatch

For more information on module installation, please visit the detailed CPAN module installation guide.

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