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Here are solutions to this weeks challenges from the Perl Weekly Challenge.

You can find my full code on Github

Challenge 1

You are given a string $S and a pattern $P.

Write a script to check if given pattern validate the entire string. Print 1 if pass otherwise 0.

The patterns can also have the following characters:

• ? - Match any single character.
• * - Match any sequence of characters.

Example 1:

Input:  $S = "abcde" $P = "a*e"
Output: 1

Solution

This challenge is relatively simple - converting "file name" wildcards into perl regular expressions. the "*" wildcard is the same as ".*" in perl, "?" is the same as "." in perl.

So we replace them in the regex (and remembering we are tied to the ends of the string).

  my $regex  = '\A' . ( $pattern =~ s{[*]}{.*}r =~ s{[.]}{?}r ).'\Z';

These are some answers to the Week 156 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 March 20, 2022 at 24:00). 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: Pernicious Numbers

Write a script to permute first 10 Pernicious Numbers.

A pernicious number is a positive integer which has prime number of ones in its binary representation.

The first pernicious number is 3 since binary representation of 3 = (11) and 1 + 1 = 2, which is a prime.

Expected Output:

3, 5, 6, 7, 9, 10, 11, 12, 13, 14

I’m not sure why the task description speaks about permuting the first 10 pernicious numbers. It seems we’re simply requested to display them.

Pernicious Numbers in Raku

I recently became aware of a very cool service provided by the Google. The Civic Information API provides contact information for all elected representatives (from head of state down to municipal official) for any US address.

I wrote the Perl client for the API, published as Net::Google::CivicInformation. Get a free API token and you're up and running.

This was a satisfying project because I can imagine people finding actual value in the product. I'm all for being vocal with our government! I decided to take it a step further and created a webservice interfacing to the API. It's written in Dancer2 and the source code is on Github (at the urging of ++GabSzab who pointed out that there are few examples of Dancer2 apps for developers to study.)

The site is online now at https://contactmyreps.com. Please give it a try. Feedback welcome!

Let's look at the brighter side ...

Did you have chance to read my annual report?

I have been doing monthly report for many years now.

Why? What is the point?

Well, let me answer the first question, Why? To be honest with you, I do it to keep myself motivated. I need some kind of (self) motivation to carry on what I do on a daily basis. Now to answer the second question, What is the point? It helps me to keep track and follow the progress.

The British Royal Family and GameStop have been in a secret war with each other for hundreds of years. Nobody knows why. GameStop has included it in their manifesto and the Royals is always untrustworthy. They leave clues to mock us! GAMESTOP HAS INCLUDED IT IN THEIR MANIFESTO! MOCK! MOCK!

There is more:

Q found out that reincarnation is true and he has been imprisoned in The Pentagon. Qanon are protecting this secret. The Biden administration knows the truth but Qanon have paid them off with a warehouse full of holy water. The Wikipedia entry for The Pentagon keeps getting edited by the Biden administration and Qanon even admit it. They leave clues to mock us.

You too can find out the truth about what's REALLY going on here or here

These are some answers to the Week 155 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 March 13, 2022 at 24:00). 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: Fortunate Numbers

Write a script to produce first 8 Fortunate Numbers (unique and sorted).

According to Wikipedia:

A Fortunate number, named after Reo Fortune, is the smallest integer m > 1 such that, for a given positive integer n, pn# + m is a prime number, where the primorial pn# is the product of the first n prime numbers.

Expected Output:

3, 5, 7, 13, 17, 19, 23, 37

Fortunate Numbers in Raku

We first create an infinite (lazy) list (@primes) of prime numbers. Then, we use it to create a list of primordials (@primorials). And then, we use it to find fortunate numbers.

Here are solutions to this weeks challenges from the Perl Weekly Challenge.

You can find my full code on Github

Challenge 1

You are given string $S containing alphabets A .. Z only and a number $N . Write a script to encrypt the given string $S using Caesar Cipher with left shift of size $N .

Solution

sub caesar {
  return $_[0] =~ s{([A-Z])}{chr 65+(-65-$_[1]+ord$1)%26}regex;
}

This is a simple one liner - but has some neat features - other than using "regex" for the switches, although most are important...

• r - return value rather than substitute in original string
• e - evaluate replace rather than use string
• g - repeat over all characters
• x - not needed (comments in match) - but looks good!

In the evaled replacement code - there is some clever ordering of values to reduce the need for brackets...

Well, it’s been a hot minute since the last release, hasn’t it? Dancer2 0.300005 has landed on CPAN and features a number of bug fixes, enhancements, and doc patches:

The lighting in my bedroom uses Philips Hue bulbs — specifically, the coloured ones. Last night, I decided it would be nice to set the three lights in my bedroom to cycle slowly through a set of warm colours using a script.

I didn't want harsh transitions from one colour to the next, but for the lighting to fade from one colour to the next in a smooth gradient. Also, I didn't want the three bulbs to all be the exact same colour, but wanted each bulb to be at different stage in the cycle, like they're "chasing" each other through the colours.

So I whipped up a quick script. It requires the command-line tool hueadm to be installed and set up before we start. You can run hueadm lights to get a list of available lights, and in particular, their ID numbers.

These are some answers to the Week 154 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 March 6, 2022 at 24:00). 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: Missing Permutations

You are given possible permutations of the string ‘PERL’.

PELR, PREL, PERL, PRLE, PLER, PLRE, EPRL, EPLR, ERPL,
ERLP, ELPR, ELRP, RPEL, RPLE, REPL, RELP, RLPE, RLEP,
LPER, LPRE, LEPR, LRPE, LREP

Write a script to find any permutations missing from the list.

We’ll assume that the permutations provided are correct, but that at least one is missing. In fact, if one of the permutation is wrong, this would not alter the result. For this task, we’ll generate all permutations and compare the result with the given list of permutations.

Missing Permutations in Raku

This week we had contrasting challenges.

Challenge 1 - Reverse Words

Take a string of words {with arbitrary white space around the words} and reverse the order of the words in the string and removing any redundant white space.

This is a classic example of a 1-liner....

   join q( ), reverse grep {$_} split m{\s+}, $_[0];

Challenge 2 - Edit Distance

I will provide 2 solutions here... one a less optimal solution which at the same time gives us a nice way of rendering the alignment - and then an more efficient "boiling down" of the first algorithm to just return the distance...

I'm just going to add "Another day job challenge!"

To be able to make "nicer" output - rather than just keeping track of the edit distance of substrings - we will actually keep the alignment of the two words as a string of "operations" whether they be Indels or SNPs.

Let me preface this short post with this, I don't have the solution to this problem. Perhaps there is someone in the wider Perl space who is well placed to pick this up, but there seems to be little going on in terms of community engagement.

In the first week of 2021 I noticed a link to this sunset message for rt.cpan behind displayed on the rt.cpan homepage. Firstly I believe the notification on the page could be highlighted better, grey on grey, on a page with lots of grey isn't exactly eye catching.

At the time the linked article didn't contain much information, besides a date. It has since been updated with links to resources to migrate tickets elsewhere.

This is a Raku answer for the 096 Perl Weekly Challenge

.

Exercise 1

The first task consists in writing a script to reverse the order of words without leading/trailing spaces. These are the examples:

Example 1:
Input: $S = "The Weekly Challenge"
Output: "Challenge Weekly The"

Example 2:
Input: $S = " Perl and Raku are part of the same family "
Output: "family same the of part are Raku and Perl"

This is easy to implement in Raku due to the many routines and methods included by default:

sub challenge( $string ) {
  return $string.words.reverse;
}

Exercise 2

The second exercise is the implementation of the Wagner–Fischer algorithm to compute the edit distance between two strings of characters. Raku shows the muscle of its support for OOP, allowing to almost literally write down the algorithm as a class. This is the pseudocode algorithm on Wikipedia:

These are some answers to the Week 153 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 February 27, 2022 at 24:00). 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: Left Factorials

Write a script to compute Left Factorials of 1 to 10. Please refer OEIS A003422 for more information.

Expected Output:

1, 2, 4, 10, 34, 154, 874, 5914, 46234, 409114

The task specification unfortunately lacks a precise definition of left factorials. Looking at OEIS A003422, I found we could use the following recursive definition:

a(0) = 0
a(1) = 1
a(n) = n*a(n - 1) - (n - 1)*a(n - 2)

What is a role? Put simply, roles are a form of code reuse. Often, the term shared behavior is used. Roles are said to be consumed and the methods ( including attribute accessors ) are flattened into the consuming class.

One of the major benefits of roles is they attempt to solve the diamond problem encountered in multi-inheritance by requiring developers to resolve name collisions manually that arise in multi-inheritance. Don't be fooled however, roles are a form of multi-inheritance.

I often see roles being used in ways they shouldn’t be. Let’s look at the mis-use of roles, then see an example of shared behavior.

I’m using that word inheritance a lot for a reason, one of the two ways I see roles most often misused is to hide an inheritance nightmare.

Palindromic numbers

You are given a number $N. Write a script to figure out if the given number is Palindrome. Print 1 if true otherwise 0.

There is an easy solution to this - to use "reverse" in string context to reverse the number and comparing the two strings:

sub is_palindrome_rev {
  return ( $_[0] eq reverse $_[0]) ? 1 : 0;
}

But this just seems a touch too easy - so let's see if we can find an alternative solution. Something that will potentially work in any base - not just base 10!

I have created a static archive of rt.cpan.org - it is avaliable at https://rt-cpan.github.io/. This is now what will be the official static archive once rt.cpan.org is sunset.

The static archive is a git repo, hosted using github pages. The repo can be found at https://github.com/rt-cpan/rt-cpan.github.io and it has a README that explains how the archive is/was built and URL structure.

The archive is generally complete, it will be updated one more time before the end of February this year. If you discover any issues then please raise an issue using the github link above. If you need to search the archive then you can do that using the gihub link above also, or git clone it and use the command line.

Happy New Year!

These are some answers to the Week 151 of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Task 1: Binary Tree Depth

You are given binary tree.

Write a script to find the minimum depth.

The minimum depth is the number of nodes from the root to the nearest leaf node (node without any children).

Example 1:

Input: '1 | 2 3 | 4 5'

                1
               / \
              2   3
             / \
            4   5

Output: 2

Example 2:

The other day I was converting the output of a Git::Raw::Commit into JSON using my module JSON::Create, when I noticed an oddity:

{
"commits":[
    {
        "body":null,
        "id":"27ed4669e32ce2d14831c719dfd5b341a659788e",
        "message":"Remove a stray html ending tag\n",
        "time":"1609997818"
    },

The "time" part always comes out as a string, even though it's clearly a number. Was this a bug in my module, some kind of dual-string-and-number wannabee variable which JSON::Create falsely turned into a string?

Here are solutions to this weeks challenges from the Perl Weekly Challenge.

You can find my full code on Github

Challenge 1

You are given file $FILE.

Create subroutine readN($FILE, $number) returns the first n-characters and moves the pointer to the (n+1)th character.

Solution

Rather than turning this into an object which was the first idea - I decided to keep the code clean by making it a function call, and to also make it work with multiple file handles open simultaneously.

To achieve this without an object - we will need to use a global hash to contain the opened file handles - so that when we re-call the function we don't re-open the file.