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.

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 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

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?

If you want to challenge yourself on programming, especially on Perl and/or Raku, go to https://perlweeklychallenge.org, code the latest challenges, submit codes on-time (by GitHub or email).

Do tell me if I am wrong or you strongly oppose my statements!

Task 1 of #094 looks like a sibling of Task 1 of #092 (which Perl codes are recently reviewed, my submitted code here) and Task 2 of #094 looks like a sibling of Task 2 of #093 (where I use the array representation of binary tree, code here).

Task 1: Group Anagrams

Now I was thinking of CJK characters. When comparing terms, put -CA; and inside scripts, put use utf8; use open ':std', ':encoding(UTF-8)';.

And my approach is similar to that of Week #092. On #092, a sub learn_pattern produces a hash from the first parameter; and sub verify_pattern for the second parameter returns true or false. Now, this time we face a bulk of terms, therefore we have to &collect_alphabets: [1]

The two challenges this week were a nice introduction to the new year.

Challenge 1 - Group words into groups of anagrams.

This is a nice hash or "arrayref"s question - a Perl staple. For each group we need to generate a key, and put every anagram into this bin.

The simplest key is just to sort the letters into alphabetical order:

join q(), sort split m{}

This means the meat of the method can be written as a one liner.

sub group_anagrams {
  my $anagrams = {};
  push @{ $anagrams->{join q(),sort split m{}} }, $_ foreach @_;
  return $anagrams;
}

Challenge 2 - Flattening Trees & Linked Lists

Again with simple Tree and LinkedList classes this becomes a good
example of simple OO coding.

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)

This is your friendly reminder that the SanDiego.pm quarterly meeting will be this Tuesday, January 12th, starting at 7 PM PST. As has been the case for the last several meetings, we'll be meeting again on Zoom (details below).

Topics for the meeting include Perl (of course), COVID-19, CentOS, and anything else that people would like to talk about.

One thing which I like about Mojolicious is that they put all the functions and methods in alphabetical order. When you get used to that then go back to a module like Git::Raw::Repository with a large number of functions in apparently random order, it does seem like quite a smart move for the reader to use the alphabetical ordering.

Anyway I thought so, so I've been putting all the functions, methods, and other things in my modules into alphabetical order. I even started to write tests that they are all alphabetical, since I usually manage to slip up on these things.

Bye, 2020

There are 28 entries on this blog in the Year 2020.

In February, I started to join "The Weekly Challenge"(PWC in short, as initially it was called "Perl Weekly Challenge" while the name "Perl6" hadn't been replaced by Raku). Then I slowly involved in the Perl community as a beginner.

At first, my codes were messy! I have forgotten from where I heard of Perl Best Practices(by Damian Conway; btw, I have to revisit it again), but have been trying to adopt some of its pieces of advice as many as possible. And then I read more codes and decided to maintain my code more modularized and structured; in addition, I have learnt to use the unit testing package in Perl (thanks to Perl Monks).

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:

Lets wipe out the memory of 2020

Am I bitter about 2020?

No, not at all. I like to find happiness in every little things in life. It is an art that I am still learning. I am writing this as a part of my monthly routine sharing last month activities. However this is special as it also has overall annual report of the year 2020.

I am embarassed looking back what I had planned at the start of the year.

Do I have any plan for 2021?

No way, I am not going to repeat my mistake. For a change, I want to see how I deal with my life without any plan.

Last January there was a post on reddit which claimed that my module JSON::Parse was not only failing some of the JSON Test Suite tests, but also crashing on one of them. Anyway I should have got around to doing something about it sooner, but here are my conclusions.

First of all there was a crash on one of the files, which went something like this: [{"":[{"":[{"", repeated about 100,000 times. (The actual file is here if you really want to see it.) Investigating it using a LInode, I found that after 80,000 open brackets the stack was overflowing, causing the crash to occur. If I added a printf in the midst of my code the printf would cause the stack overflow, so it wasn't actually due to my code but just because the stack size seems to be quite small on Linux.

This is a Raku answer for the 093 Perl Weekly Challenge . This is also my first post.

Exercise 1

Using a similar approach than James Curtis-Smith , the solution looks at points with equal slope to see if they are in a straight line. Being less literate in Raku, using classes help me to organize coding ideas.

This exercise gives me the opportunity to work with the type BagHash. The highest value of the slopes stored in a BagHash gives the number of points in a straight line. Happily, the first example in Raku documentation is for a Class Point, an example reused in this solution.

These are some answers to the Week 149 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 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: Fibonacci Words

You are given two strings having same number of digits, $a and $b.

Write a script to generate Fibonacci Words by concatenation of the previous two strings. Finally print 51st digit of the first term having at least 51 digits.

Example:

Update: Ben Bullock has provided script for my question.
See the comment section. Thanks Ben.

---------------------

Happy New Year!

$ perl pwc092-1_isomorphic.pl '茫茫人海' '夜夜笙歌'
0

--

Seeing others' post, I have a short reflection on dated The Weekly Challenge #092 Task 1 (statements / recap ), but may lead to a hike towards a hill in Perl.

Task statement:

TASK #1 › Isomorphic Strings Submitted by: Mohammad S Anwar

You are given two strings $A and $B.

Write a script to check if the given strings are Isomorphic. Print 1 if they are otherwise 0.
Example 1:

Input: $A = "abc"; $B = "xyz"
Output: 1

Example 2:

Input: $A = "abb"; $B = "xyy"
Output: 1

Example 3:

Input: $A = "sum"; $B = "add"
Output: 0

My unsatisfactory code (distaste due to the two subroutines &verify_pattern and &learn_pattern are almost the same).

Suddenly today I want to try out whether the Unicode support is direct; sadly, no:

For a single character:

These are some answers to the Week 93 of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Spoiler Alert: This weekly challenge deadline is due in a few days (January 3, 2021). This blog post offers some solutions to this challenge, please don’t read on if you intend to complete the challenge on your own.

I'm not a great blogger - but I will try and explain my solutions to the Perl weekly challenge each week. I always try and look for interesting solutions to the problems at hand.

Part 1

Not sure on the correct way to do this... I first looked at all the pairs of points - and looked to see what the direction was between the points. For those where the y-coordinates are different you can just use (x1-x2)/(y1-y2) to represent the slope. We also that flipping the order of the points gives the same value. For those canses where y is the same - the slop can be represented by an "infinity value" in my case i use "-"

I managed to cause another set of obscure bugs by misusing newSVpv. The goal of this code is to split the RGB and the alpha (transparent) part of a PNG image, for the use of the PDF::Builder module on CPAN.

Here the SV in newSVpv is "scalar value", and the "pv" means "string". My code says this:

sv = newSVpv ("", len);

and it causes the crash on Solaris and other operating systems because the above statement is a bad idea. What happens is that Perl copies "len" bytes from my string, where "len" might be a very large number, for a large PNG image, but I've given it the string "" to copy from. So Perl tries to copy from uninitialised, or possibly even inaccessible, parts of the computer's memory. I found out my error only after almost giving up, by using valgrind to look for memory errors.

The correct version of this is