SPVM 0.9014 Release - add class, method, static keyword, omit SPVM:: namespace

I release SPVM 0.9014. Latest releases have some big changes.

add class, method, static keyword, omit SPVM:: namespace, and remove sub, self, keyword.


Perl Weekly Challenge 130: Odd Number and Binary Search Tree

These are some answers to the Week 130 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 September 19, 2021 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: Odd Number

You are given an array of positive integers, such that all the numbers appear even number of times except one number.

Write a script to find that integer.

Example 1:

Input: @N = (2, 5, 4, 4, 5, 5, 2)
Output: 5 as it appears 3 times in the array where as all other numbers 2 and 4 appears exactly twice.

Example 2:

Input: @N = (1, 2, 3, 4, 3, 2, 1, 4, 4)
Output: 4

Monthly Report - August

Finally enjoying again ...

Ever since I joined Oleeo, I keep talking about it in every monthly report.


Well, right from day one, I have been getting to work on something I never worked on before. To be honest with you, I was expecting to fight with good old CGI ridden code mostly. I find myself lucky to have such a great supporting team. Right now I am playing with Elastic Search and I am enjoying it. Thanks to CPAN for such a cool library, Search::Elasticsearch.

Did you notice last monthly report was published on 22nd Aug?

I have never been so late ever since I started the series of monthly report.

You must be thinking, why bother with monthly report? Who cares what I do?

I agree, nobody cares. But I still do it every month since Nov 2018, my first monthly report was published on 2nd Nov 2018. In two months time, I would complete 3 years of monthly reporting. Honestly speaking, I didn't realise it until now.

My Favorite Warnings: redundant and missing

The redundant and missing warnings were added in Perl 5.22 to cover the case where a call to the printf or sprintf had more (redundant) or fewer (missing) arguments than the format calls for. The documentation says that they may be extended to other built-ins (pack and unpack being named specifically) but as of Perl 5.34.0 only the printf() built-ins are covered.

I have (very occasionally) found myself writing a subroutine taking a printf-style format and some arguments, and letting the format specify which (if any) of the arguments actually appear in the output. If I just throw all the arguments after the format into the printf(), one of these warnings is very likely to be thrown, starting with 5.22, since use warnings; enables them by default.

How to show UTF-8 at the Windows command prompt

If you windows Perl user, It is good to know How to show UTF-8 at the Windows command prompt .

How to show UTF-8 at the Windows command prompt

One liner is yet buggy, however UTF-8 showing is good in Windows command prompt.

Perl Weekly Challenge 128: Minimum Platforms

These are some answers to the Week 128 of the Perl Weekly Challenge organized by Mohammad S. Anwar.

Note: very little time this week, so I only completed task 2.

You are given two arrays of arrival and departure times of trains at a railway station.

Write a script to find out the minimum number of platforms needed so that no train needs to wait.

Example 1:

TWC 127: Intersection on a Sunday Afternoon

This is my entry for

The Weekly Challenge, week 127

Task 1, "Disjoint Sets" was basically something I've done before somewhere else. In fact, what I'm using is overkill for just determining if two sets intersect. I imagine most people would probably use the FAQ answer. However, I'm a fan of what cardinal LanX of Perl Monks fame was trying to do in making set intersection a more "organic" operation. I don't know how much those ideas developed, however, so I'll be looking at the other solutions to see if there's anything new.

I actually did use my perlmonks code on real problem a few years ago, in modified form. It does the trick pretty quickly compared to other approaches. Thanks perl hashing!

You can find my code for Task #1 here.

My Favorite Warnings: once

The Perl compiler wants to help us write clean code. One of the ways that it does this is to issue warnings when a global variable appears ony once: Name "main::Foo" used only once: possible typo at ...

The thing is, sometimes this is not an error. For example, we may want to refer to a global variable in another package, one that was not imported into our namespace.

I have seen various expedients used to avoid this warning in CPAN code. Something like $Foo::Bar = $Foo::Bar = 42; is fairly typical. Sometimes this strange-looking code is commented as to its purpose, others not.

Alternatively, you can use the pragma no warnings 'once'; to supress this warning. This seems to me the appropriate way to spell "I meant to do that!" under the circumstances:

Monthly Report - July

Never been so busy ...

The guilt is killing me every time I delay the monthly report. I finally found time to get this out on 22nd day of the month where I would do that on the very first day of the month in the past.

Life can be challenging at times, balancing personal and professional aspect can be difficult, I must confess.

In all of these up and down, I have to keep myself motivated and find ways to stay happy.

I try to avoid negative thoughts coming on my way and stay positive.

A dream realized

Have you heard that they are finally putting together a proposal to add a clean modern OO system into the core of Perl?

If you haven’t, I strongly encourage you to look over the RFC for Corinna, or at least watch Ovid’s excellent presentation on the project.

It’s reassuring that the list of contributors to the proposed design includes some of the most highly respected names in the Perl community, many of whom have previously taken one (or more!) tilts at this particular object-oriented windmill.

Indeed, over the past two decades I too have repeatedly attempted to design and prototype richer and more robust OO systems for Perl, starting way back in the previous millennium with a brief stint as the maintainer of Class::Struct, and continuing on though the release of modules such as Class::Std, Class::Delegation, and most recently: Dios.

Making Taint support optional in Perl

One of the changes to Perl that we're considering on p5p (the perl5-porters mailing list) is the removal of taint support. The first step towards that is to add a Configure option that lets you build a Perl without taint support.

In this post I'll explain what we're considering, and why. The purpose of this post is to let everyone beyond p5p know about this, and give you a chance to comment.

TWC 124: Literalism and existence proofs in the service of stress reduction

Again another week where I solve one answer and punt on another.

TWC Task #1, Happy Women Day

jaredor submission for Task #1

Well, "solve" may be a strong word for what I did with this problem, at least for my programming conscience. The problem statement was simple, but had no requirements for an acceptable solution other than what you could infer from the example solution in the problem statement. However I did give not one, but two solutions, so that's not totally lazy, even if each, on its own, is lazy, right?

--lazy solution

EV charge calculator from script to Dancer web

Since my last post I wanted to take my EV charge calculator script and convert it into a web form. In this post I breakdown how I migrated the script to a Dancer2 web app.

Just a minor note for those readers who may not be aware, Dancer2 is a "lightweight web-framework for Perl" as described in Dancer2 documentation and can be similar in comparison to Ruby Sinatra and Python Flask.

I started by creating a new project folder with the dancer2 program ( # please note that I am working on a Windows PC and on a linux OS the program would just be named dancer2 )

dancer2.bat -a EVCalc

I then copy over the files inside this directory to my project repository as shown in this commit and moved all the scripts to the bin directory as shown in this commit

I wrote a script to covert the electric rate csv file into a module and added all the calculation code in the main project module. All the html markup is stored in this template file and I sprinkled some CSS which renders a page similar to the screenshot below after submitting some data for calculating the charge of an EV :


Thank you for your time, I hope you enjoyed my post.

Railroad diagrams for SQL 2003 and SQL 2016

On github at https://github.com/ronsavage/SQL you will find a repo of SQL stuff created by Jonathan Leffler.

I recently added some files for SQL 2003 and SQL 2016, created by Domingo Alvarez Duarte.

Specifically, look for:
o sql-2003-2.ebnf
o sql-2003-2.ebnf.readme
o sql-2003-2-railroad-diagrams.xhtml
o sql-2016.ebnf
o sql-2016.ebnf.readme
o sql-2016-railroad-diagrams.xhtml

I'd suggest downloading the *.xhtml files and viewing them locally, rather than hammering the on-line convertor mentioned in the readme files, which accepts *.ebnf files and displays these railroad diagrams.

And that begs the question: Is there any Perl code which converts a grammar into a railroad diagram?

Are you using Cache::Memcached and its ->stats method?

It's very slow if you have more than a few thousand keys in memcached. Not an unusual use case I think? I've got a fix here, which appears to DTRT: https://rt.cpan.org/Ticket/Display.html?id=138133. Maybe? I didn't spend too long looking at memcached's low level wire protocol.

The patch passes all the module's current tests and works for us. It took our CPU load from being pegged at 75% all of the time to being idle. So, if you're using Cache::Memcached, and the ->stats method (which isn't in the XS version of the module) then you might want this patch.

On that note - who is maintaining Cache::Memcached? The last release was in 2012. This isn't a high river module, but any app of significant size or age is *probably* using it and if they're using the ->stats method then ... Sure there's the ::Fast version, but I suspect this version is in a lot of places.

So if you know someone who knows someone who can prod the current maintainers then please point them at this post/patch. If you're using Cache::Memcached then perhaps try out this patch as well.

Random Thought: Exposure of Perl in the Academic Circles

Today I have wandered on the famous academic paper archive and suddenly a thought popped into my mind - use Perl as the keyword in searching.

Computer science papers with "Perl" in the title
https://arxiv.org/search/advanced?advanced=1&terms-0-operator=AND&terms-0-term=Perl&terms-0-field=title&classification-computer_science=y (8*)

Computer science papers with "Lisp" in the title
https://arxiv.org/search/advanced?advanced=1&terms-0-operator=AND&terms-0-term=Lisp&terms-0-field=title&classification-computer_science=y (12**)

Computer science papers with "Ruby" in the title
https://arxiv.org/search/advanced?advanced=1&terms-0-operator=AND&terms-0-term=Ruby&terms-0-field=title&classification-computer_science=y (6***)

Computer science papers with "Julia" in the title
https://arxiv.org/search/advanced?advanced=&terms-0-term=Julia&terms-0-field=title&classification-computer_science=y (53 ****)

For Haskell: ~50

For Java: ~249

For Python: ~357

For Perl Data Language (PDL): 0

On the eve of CPAN Testers

Have a look at the CPAN Testers reports for two TRIAL releases of the same module, one from 2 days ago, the other a little over 3 years ago:

Last time, reports started coming in within hours of the release; over 60% of the picture was there within a day; some 85% after 2 days; and the first wave of reports lasted a week.

This time, it took almost a day to even start getting reports, and the diversity has been much lower. 3 days in, reports are still absent for many platforms:

TWC 119: Les Nybb and the Arrhythmic Trio

In which Raku solutions give shape to Perl solutions, and vice versa, and then Raku does what Raku does best.

Task 1: Swap Nibbles - basic and extended solutions in Raku and Perl.

Task 2: Sequence of symbols 123 without adjacent 1’s. Solutions in Raku and Perl, then a radically different approach that I would have never discovered in anything but Raku.

CPAN Bus Factor

Perhaps you've noticed a new metric when browsing MetaCPAN?


What is "bus factor"?

Wikipedia defines "bus factor" as

a measurement of the risk resulting from information and capabilities not being shared among team members, derived from the phrase "in case they get hit by a bus."

For CPAN our definition is "a measurement of how risky it might be to start relying on a CPAN module, which might not be actively maintained".

Read the full post.

How I Uploaded a CPAN Module

An updated but yet to be completed version is here.

So, accumulating effort from Wednesday, today(Friday) I become a CPAN contributor!

I got a PAUSE ID 2 weeks ago. If you are also interested in the Perl ecosystem, you may consider to apply for a PAUSE ID as well.

In this blogpost, I mainly follow the instructions here:

Some contents of the PerlMonks article are largely repeated here.

This piece of PerlMonks article is already 19-year-old, but it is still valid. One of the good things of the article is that you need not install new modules or programs if you are on a *nix system.


One should have some knowledge on modules, packages and, not really necessary, object-oriented Perl ("Perl OO" in short).

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