blogs.perl.org

I've turned the libdeflate compression library into a CPAN module:

Gzip::Libdeflate

This is the gzip compression method, but updated.

It's supposed to be much faster and better than libz (the original gzip library).

Sometimes I am getting compression of as much as 30% better on some files.

So far I haven't tested whether or not it is faster.

See the module above for links to the original library and so on.

Since this is an early release, it's very likely indeed that bugs in the module are my fault rather than any problem with libdeflate, so please report them to me.

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 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:

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.

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.

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...

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 January 30, 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 Digit Sum

Given an input $N, generate the first $N numbers for which the sum of their digits is a Fibonacci number.

Example:

f(20)=[0, 1, 2, 3, 5, 8, 10, 11, 12, 14, 17, 20, 21, 23, 26, 30, 32, 35, 41, 44]

Fibonacci Digit Sum in Raku

We first populate a Set (for fast look-up) with the Fibonacci numbers up to 1000. Note that we could choose a much smaller maximum value, but it doesn’t cost much and it will work with very large sequences.

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:

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!

These are some answers to the Week 148 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 January 23, 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: Eban Numbers

Write a script to generate all Eban Numbers <= 100.

*An Eban number is a number that has no letter ‘e’ in it when the number is spelled in English (American or British).

Example:

2, 4, 6, 30, 32 are the first 5 Eban numbers.

The task asks us to list the Eban integers smaller than or equal to 100. To start with, 100 (“one hundred”) has two ‘e’, so it is not an Eban number. So we can limit our search to all Eban Numbers < 100, so that we can limit our search to integers with one or two digits.

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!

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]

These are some answers to the Week 147 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 January 16, 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: Truncatable Prime

Write a script to generate first 20 left-truncatable prime numbers in base 10.

In number theory, a left-truncatable prime is a prime number which, in a given base, contains no 0, and if the leading left digit is successively removed, then all resulting numbers are primes.

Example:

9137 is one such left-truncatable prime since 9137, 137, 37 and 7 are all prime numbers.

Truncatable Prime in Raku

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.

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.

These are some answers to the Week 146 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 January 9, 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: 10001st Prime Number

Write a script to generate the 10001st prime number.

10001st Prime Number in Raku

Raku has a fast is-prime subroutine or method, using the Miller-Rabin algorithm, to test whether a integer is prime. We can just generate an infinite (lazy) list of prime numbers and look for the 10000st one.

use v6;

my @primes = grep { .is-prime }, (1, 2, 3, -> $a { $a + 2} ...Inf);
say @primes[10001 - 1];  # Subtract 1 because the array starts at 0

This script displays the following output:

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.