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These are some answers to the Week 221, task 2, of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Spoiler Alert: This weekly challenge deadline is due in a few days from now (on June 18, 2023 at 23:59). This blog post offers some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.

Arithmetic Subsequence

You are given an array of integers, @ints.

Write a script to find the length of the longest Arithmetic Subsequence in the given array.

A subsequence is an array that can be derived from another array by deleting some or none elements without changing the order of the remaining elements.

A subsequence is arithmetic if ints[i + 1] - ints[i] are all the same value (for 0 <= i < ints.length - 1).

Example 1:

Following the release of 5.36.0, we have a new Perl Steering Council (PSC). The PSC for the next year comprises Ricardo Signes (RJBS), Paul Evans (PEVANS), and Philippe Bruhat (BOOK). These three will serve until 5.38.0 is released, at which point the next PSC will be elected.

There is nothing like looking, if you want to find something. -- The Hobbit, iv, "Over Hill and Under Hill"

Recently on the p5p mailing list the topic of removing smart match re-surfaced. There was a fairly vigorous discussion about the effect this would have on CPAN. So I thought I would look into how many uses there actually were.

Fortunately there are Perl Critic policies for this: Jan Holčapek's Perl::Critic::Policy::ControlStructures::ProhibitSwitchStatements and Perl::Critic::Policy::Operators::ProhibitSmartmatch. All I had to do was run them against my mini-CPAN.

My results:

• Total distributions: 40704
• Distributions with violations: 842
• Files with violations: 1568

A look at the file names involved says that about two-thirds of the violations are in the published modules themselves, and the rest are in support code (directories t/, inc/, and the like).

It is possible that the results of Perl::Critic::Policy::ControlStructures::ProhibitSwitchStatements contain false positives simply because someone implemented subroutines named given() or when() unrelated to smart matching.

I am trying to contact Francis van Dun (FVANDUN on cpan) for permission to relicense Net::DHCP to the MIT license.

The email listed on cpan bounces. If you are out there Francis please give me your blessing via the above link.

These are some answers to the Week 221, task 1, of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Spoiler Alert: This weekly challenge deadline is due in a few days from now (on June 18, 2023 at 23:59). This blog post offers some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.

Good Strings

You are given a list of @words and a string $chars.

A string is good if it can be formed by characters from $chars, each character can be used only once.

Write a script to return the sum of lengths of all good strings in words.

Example 1

Input: @words = ("cat", "bt", "hat", "tree")
       $chars = "atach"
Output: 6` 

The good strings that can be formed are "cat" and "hat" so the answer is 3 + 3 = 6.

Please checkout my experience decoding hexdump.

https://theweeklychallenge.org/blog/decode-hexdump

File::stat overrides the core stat() and lstat() functions. Instead of arrays, the new functions return an object having methods corresponding to the elements of the arrays returned by the original functions. This module has been in core since Perl 5.004.

The advantage of this module is clearer code. For example, to get the size of file $file without it is something like

    my $size = ( stat $file )[7];

But with this module the same effect is given by

    my $size = stat( $file )->size();

Once you have the object in hand, you cam query it for any of its properties, so if you want both size and modification time, instead of

    my ( $size, $mtime ) = ( stat $file )[ 7, 9 ];

There's been a lot of work on MooseX::Extended and now it comes with a fairly extensive tutorial.

The basics are pretty easy to learn, but it gives you a good amount of power. It also allows you to easily define custom versions so you can just slap use My::Custom::Moose; (or role) at the top or your code and it works just fine.

You can now disable just about any features in it you don't want. You can also include experimental features, such as multimethods (based on number of args) and async/await.

Check out the github repo if you'd like to contribute.

These are some answers to the Week 220, task 1, of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Spoiler Alert: This weekly challenge deadline is due in a few days from now (on June 11, 2023 at 23:59). This blog post offers some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.

Common Characters

You are given a list of words.

Write a script to return the list of common characters (sorted alphabetically) found in every word of the given list.

Example 1

Input: @words = ("Perl", "Rust", "Raku")
Output: ("r")

Example 2

Input: @words = ("love", "live", "leave")
Output: ("e", "l", "v")

Common Characters in Raku

On Tuesday 21st June there will be a Perl IDE Hackathon in the Hackathon room at The Perl and Raku Conference. You can also participate in this event remotely.

Our goal is to enhance IDE and Editor support for Perl 5 which is typically via plugins, with an an emphasis on helping people make their first every contribution. It's not even required that you use the IDE/Editor that you are helping out with.

With support from their authors, I am hoping we can help make meaningful contributions to the following, :

- Jetbrains IDEA plugin
- Language Server's for VSCode etc. i.e. Perl Navigator, Perl::LanguageServer, PLS
- Vim plugin vim-perl
- Emacs
- Others!

Recall that IDE support is a priority for the community and we need your help!

If you are attending the Perl and Raku conference then simply turn up at the venue on the 21st with your Laptop and find the room! There will be wifi and we will work together with everyone in the slack channel.

Do you want to convert Perl source into .exe?

Please checkout my experience.

https://theweeklychallenge.org/blog/strawberry-perl

The filetest pragma modifies the behavior of the file test operators (a.k.a. the -X operators.) It has been in core since Perl 5.6.0.

As of Perl 5.36.0 it still has only one sub-pragma, 'access', which applies to the -r, -w, -x, -R, -W, and -X tests. Normally, these tests only consider the mode bits returned by stat(), as discussed in my previous blog post, The File Access Operators: To Use, or Not to Use. But within the scope of use filetest 'access';, these tests consider not only the mode bits, but any ACLs (Access Control Lists) that may be applied to the file -- at least, under POSIX systems. Under systems that do not implement access(), this sub-pragma does nothing.

Taking ACLs into account sounds like a Good Thing, but it comes at a price. Within the scope of the 'access' sub-pragma:

These are some answers to the Week 219, task 1, of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Spoiler Alert: This weekly challenge deadline is due in a few days from now (on June 4, 2023 at 23:59). This blog post offers some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.

Sorted Squares

You are given a list of numbers.

Write a script to square each number in the list and return the sorted list, increasing order.

Example 1

Input: @list = (-2, -1, 0, 3, 4)
Output: (0, 1, 4, 9, 16)

Example 2

Input: @list = (5, -4, -1, 3, 6)
Output: (1, 9, 16, 25, 36)

Sorted Squares in Raku

As part of HalleLeipzig.pm I had my duties to co-organize the recent German Perl Workshop but also the opportunity to give some talks. (Recordings are online [EDIT] now at the CCC video platform). My main talk was about plotting data with Perl (english slides).

After a very long time, I found time to blog and here is my journey to deal with memory leak in Perl.

https://theweeklychallenge.org/blog/memory-leak/

The current state: The Perl interpreter and most of CPAN are provided under the Artistic 1.0 license and the GPL1.0 license. The Artistic 1.0 license was written by Larry Wall and due to its problems Perl is simultaneously licensed under the GPL 1.0 License.

It is the de-facto standard to license software published to CPAN under the same terms as the Perl interpreter.

The Artistic 2.0 license supersedes the Artistic 1.0 license and is designed to overcome its problems. Raku uses this license as it was specifically created for Perl 6. Mojolicious also uses this license.

The Artistic licenses are not widely used outside the Perl & Raku sphere.

What is the "best" license? (Discussion)

The major philosophical axis in (free) Open Source licenses is Copyleft versus Permissive

"Copyleft" licenses require source code to be made available with compiled software that is distributed. "Permissive" licenses don't have that requirement.

These are some answers to the Week 218 of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Note: the programs presented here were written several days ago, but I was unable to write this blog post in time due to various reasons, including lack of time and some serious problems with my computer.

Task 1: Maximum Product

You are given a list of 3 or more integers.

Write a script to find the 3 integers whose product is the maximum and return it.

Example 1

Input: @list = (3, 1, 2)
Output: 6

1 x 2 x 3 => 6

Example 2

In the wake of my postings on the file access tests (-r and friends) I wondered if there was a Perl::Critic policy to find them. So I constructed an annotated index of Perl Critic policies. Because of its size I stuck it on GitHub rather than in-line to this blog post.

This index assumes that any CPAN module whose name begins with Perl::Critic::Policy:: is a Perl Critic Policy. The index entry for each module contains the name of the module itself (linked to Meta::CPAN), the name of the distribution which contains it, and the abstract for the module if it contains anything other than a repeat of the module name. I suppose the module description could have been added, but I hoped the abstract would be sufficient.

This operation gave me 341 policies. I did not find the policy I wanted among them. In fact, only Kevin Ryde's Perl::Critic::Policy::ValuesAndExpressions::ProhibitFiletest_f came close.

For those who want context, the relevant blog posts are:

• The File Access Operators: To Use, or Not to Use
• Core Modules: filetest
• My Favorite Modules: File::stat

Let us all have fun with the latest Perl v5.36.

https://theweeklychallenge.org/blog/get-started-with-perl-v536

I'm looking for someone to take over as maintainer of these distributions. Some of these distributions contain relatively important modules, like Redis and IO-Socket-Timeout.

• Action-Retry
• Bloomd-Client
• Bot-BasicBot-Pluggable-Module-RT
• Dancer-Plugin-FlashMessage
• Dancer-Plugin-Params-Normalization
• Exception-Stringy
• IO-Socket-Timeout
• Log-Message-Structured-Stringify-AsSereal
• Moo-Lax
• POE-Wheel-GnuPG
• Params-Check-Faster
• PerlIO-via-Timeout
• Redis
• Riak-Client
• Sereal-Splitter

If you're interested by some or all of them, let me know!