These are some answers to the Week 182 of the Perl Weekly Challenge organized by Mohammad S. Anwar.
Spoiler Alert: This weekly challenge deadline is due in a few of days from now (on Sept. 18, 2022 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: Max Index
You are given a list of integers.
Write a script to find the index of the first biggest number in the list.
Example:
Input: @n = (5, 2, 9, 1, 7, 6)
Output: 2 (as 3rd element in the list is the biggest number)
Input: @n = (4, 2, 3, 1, 5, 0)
Output: 4 (as 5th element in the list is the biggest number)
Max Index in Raku
This warning was touched on in A Belated Introduction, but I thought it deserved its own entry.
When a Perl scalar comes into being, be it an actual scalar variable or an array or hash entry, its value is undef. Now, the results of operating on an undef value are perfectly well-defined: in a nuneric context it is 0, in a string context it is '', and in a Boolean context it is false.
The thing is, if you actually operate on such a value, did you mean to do it, or did you forget to initialize something, or initialize the wrong thing, or operate on the wrong thing? Because of the latter possibilities Perl will warn about such operations if the uninitialized warning is enabled.
If you really intended to do this, no warnings 'uninitialized'; will suppress the error.
Util::H2O
is an incredibly powerful tool for managing
HASH
references in a more natural way.
This post is the first of several that will explore this awesome module. I've started using it quite a bit in both new code and in existing code. There are several imporant cases where it really shines. Here we explore the power it has to iteratively refine existing code. It's also
fun
and
easy
to introduce into existing code.
Util::H2O
provides a method called
h2o
that provides a very powerful way for turning a hash reference to an
object
. Generally speaking, this means I get accessors with as few keystrokes as possible.
I've been using this module quite a bit recently, and I really do like the improvements it has over the more traditional modules used for generating accessors.
The most basic use of
h2o
is to provide accessors to a hash reference with a single level of keys. I tend to use hash references
a lot
.
I release SPVM 0.9014. Latest releases have some big changes.
add class, method, static keyword, omit SPVM:: namespace, and remove sub, self, keyword.
Before
These are some answers to the Week 181 of the Perl Weekly Challenge organized by Mohammad S. Anwar.
Spoiler Alert: This weekly challenge deadline is due in a few of days from now (on Sept. 11, 2022 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: Sentence Order
You are given a paragraph.
Write a script to order each sentence alphanumerically and print the whole paragraph.
Example:
Finally enjoying again ...
Ever since I joined Oleeo, I keep talking about it in every monthly report.
Why?
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.
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.
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.
These are some answers to the Week 180 of the Perl Weekly Challenge organized by Mohammad S. Anwar.
Spoiler Alert: This weekly challenge deadline is due in a few of days from now (on Sept. 4, 2022 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: First Unique Character
You are given a string, $s.
Write a script to find out the first unique character in the given string and print its index (0-based).
Example 1
Input: $s = "Perl Weekly Challenge"
Output: 0 as 'P' is the first unique character
Example 2
Input: $s = "Long Live Perl"
Output: 1 as 'o' is the first unique character
First Unique Character in Raku
This is my entry for
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.
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.
I start to review Paul Evans's Object::Pad from my personal thinking.
Latest years, Perl core teams positively try to implement Object-Oriented feature to Perl core. I hope my review helps a little.
First time is constructor default arguments.
These are some answers to the Week 179 of the Perl Weekly Challenge organized by Mohammad S. Anwar.
Spoiler Alert: This weekly challenge deadline is due in a few of days from now (on Aug. 28, 2022 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: Ordinal Number Spelling
You are given a positive number, $n.
Write a script to spell the ordinal number.
For example,
11 => eleventh
62 => sixty-second
99 => ninety-ninth
Hum, this task is not very interesting, since it has more to do with English than with computer science. I’m not going to enumerate dozens of numeral or ordinal English names. So, contrary to what I usually do, I’ll use an off-the-shelf module to complete this task.
Ordinal Number Spelling in Raku
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.
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.
Again another week where I solve one answer and punt on another.
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
These are some answers to the Week 177 of the Perl Weekly Challenge organized by Mohammad S. Anwar.
Spoiler Alert: This weekly challenge deadline is due in a few of days from now (on Aug. 14, 2022 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: Damm Algorithm
You are given a positive number, $n.
Write a script to validate the given number against the included check digit.
Please checkout the wikipedia page for information.
Example 1
Input: $n = 5724
Output: 1 as it is valid number
Example 2
Input: $n = 5727
Output: 0 as it is invalid number
The algorithm is a check digit algorithm named after H. Michael Damm, who presented it in 2004.
Look, that's why there's rules, understand? So that you think before you break 'em. — Terry Pratchett, in Thief of Time.
A couple installments into this series of blog posts, I realized an introduction to Perl warnings would be appropriate, with some words on how to turn them off, and why you probably do not want to. Yes, this should have been the first post in the series, but I didn't know it would actually be a series, and, well, maybe better late than never.
The Perl compiler/interpreter can emit warnings when it finds things that may indicate a problem with the code. These are not (yet) enabled by default, but experience has shown that enabling them can highlight conceptual and logic errors.
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.
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?
