blogs.perl.org

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

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

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

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

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).

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 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

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!

The file access operators are, for the purpose of this blog entry, the file test operators -r, -w, -x, -R, -W, and -X. The upper case operators test the ability of the user's real UID to read, write, or execute the file being tested. The lower case operators do the same for the user's effective UID.

Though Perl provides these, their documentation comes with cautions about their use. The rest of this blog entry represents my thoughts on their use or avoidance.

Although they may be an anthema to many, there are many active Perl communities on Facebook. The primary ones I subscribe to are

Perl Programmers

The Perl Community

The Weekly Challenge

The Perl and Raku Conference

Perl Mongers

If you search for Perl groups, you'll find many, many more, including ones for individual Perl Mongers groups.

If someone wants to talk Perl, I don't care where it is - let's talk.

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

Cross-posted from my own blog: Replay/Debug/Test Cron Events With Cron::Sequencer.

MooseX::Extended is coming along well and is ready for testing. See Introducing MooseX::Extended for a decent introduction on how to make writing your Moose code safer and easier.

With Perl 5.36.0 just around the corner, we thought that this is a good time to clarify plans for the future of the Perl programming language. We realised that the future was hammered out in a number of steps, across several months. This meant that there hasn't been a single statement we could refer people to. This post is to fill that gap.

These are some answers to the Week 217 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 May 21, 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.

Task 1: Sorted Matrix

You are given a n x n matrix where n >= 2.

Write a script to find 3rd smallest element in the sorted matrix.

Example 1

Input: @matrix = ([3, 1, 2], [5, 2, 4], [0, 1, 3])
Output: 1

The sorted list of the given matrix: 0, 1, 1, 2, 2, 3, 3, 4, 5.
The 3rd smallest of the sorted list is 1.

Example 2

One of the steps of debugging Perl can be to find out what is actually in a string. There are a number of more-or-less informative ways to do this, and I thought I would compare them.

For this I used two short strings. The first was just the concatenation of the characters whose ordinals are 24 through 39; that is, 16 ASCII characters straddling the divide between control characters and printable characters. The second was a small variation on the first, made by removing the last character and appending "\N{U+100}" (a.k.a. "\N{LATIN CAPITAL A WITH MACRON}") to force the string's internal representation to be upgraded.

The results given below include the version of the module used, the actual code snippet that generated the output, the output itself, and any comments I thought relevant. All subroutines used to dump strings are exportable except for those called as methods. The sample code makes fully-qualified calls because of duplication of subroutine names between different modules.

On github, I've released MooseX::Extreme.

It's based on years of experience being the lead designer of the Corinna project and trying to figure out how we can get a version of Moose which is safer and easier to use, including removing a lot of boilerplate. This code:

package My::Class {
    use MooseX::Extreme;

    ... your code here
}

Is sort of the equivalent to:

Hello everybody,

after a long time of waiting it is finally time - we cordially invite you
to the German Perl/Raku Workshop 2023.

Next year's workshop will take place from Monday 28 February to
Wednesday 1. March in the Saalbau Gallus in Frankfurt am Main.

These are some answers to the Week 216 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 May 14, 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.

Task 1: Registration Number

You are given a list of words and a random registration number.

Write a script to find all the words in the given list that has every letter in the given registration number.

Example 1

Input: @words = ('abc', 'abcd', 'bcd'), $reg = 'AB1 2CD'
Output: ('abcd')

The only word that matches every alphabets in the given registration number is 'abcd'.

Example 2

Input: @words = ('job', 'james', 'bjorg'), $reg = '007 JB'
Output: ('job', 'bjorg')

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:

Last night, I finally nailed it with the help of my best friend. "Taint" can no longer scare me.

https://theweeklychallenge.org/blog/taint