Happy Bit Rot Thursday! This week I'm taking care of fixing minor issues with packaging of my Perl 6 modules, and so, I'll talk about the general process of
releasing a Perl 6 module. Let's dive in!
Prelude
Perl 6 is a brand new language, so there's yet no well-established module system like what Perl 5 has, but there is a work in progress. Thus, I'll first describe the process for our temporary GitHub-based system and then I'll talk about the PAUSE-based system that's being worked on.
There are some tools and helpers available to help with the process of module development, but they are beyond the
scope of this post.
B::C and cperl has now proper support for copy-on-grow (COG) and
copy-on-write (COW) arrays.
COG means that the array of SV* pointers is allocated by the compiler
statically, not dynamically, and that the cperl runtime creates a
new array whenever the array is extended (copy-on-grow).
COW means that the array of SV* pointers is allocated by the compiler
constant and static in the .rodata segment, and that the cperl runtime
creates a new array whenever an element of the arrays is changed
(copy-on-write).
With a typical example of a medium sized module, Net::DNS::Resolver, the
memory usage is as follows:
What’s in a name? that which we call a rose
By any other name would smell as sweet;
(William Shakespeare, Romeo & Juliet, Act II Scene ii)
I went to FOSDEM in Brussels this year as a representative of the Perl Foundation. As such I spent the weekend doing my best to be a good advocate of the Perl programming languages.
FOSDEM for those of you in gentle unawareness is probably the world's largest, free, Open Source event. It is held each year in Brussels, Belgium, and attracts speakers for hundreds of talks on dozens of projects, languages and distros. The event is attended by over seven thousand people from almost everywhere in the world.
On the bus ride out to Charleroi I caught a stray brainwave about how to properly notate at least some of Haskell's Lens library, so I wrote up some notes on it. This is going to be slightly spooky, but not much more than the previously-existing ability to bind one data structure to another.
I do want to finish up the Scheme work, if only to prove the crowd on Perlmonks wrong, first though.
The 'lens' library is essentially a metaphor for focussing in on your data, in roughly the following sense:
I came across an excellent book on mazes, written for programmers (Mazes for Programmers). My only complaint is that all the examples are written in ruby. All is good though, as I work through the book, I will be converting the examples into working perl examples, detailing that experience here.
I also came across a perl module that makes some good mazes Games::Maze which also has some TODOs. Bonus! I'll take what I learn and apply it to that distribution, hopefully making Games::Maze into the goto resource for making maze-like games in perl.
I am not the author of Games::Maze. I hope that he/she is ready for some pull requests. 8)
To me It seemed a particularly good FOSDEM for both for Perl5/6 and
other talks although very crowded as usual and I didn't see the usual
*BSD or Tor stalls. I was stuck by the statistic that there were
about 500 speakers from many thousands of people so of the order of
one speaker per tens of attendees which is very high.
On Saturday I started with Poettering and systemd which was a keynote
and perhaps a little disappointing since he usually is a better
speaker and the audio was a little indistinct. systemd had won being
used by all distros except gentoo and slackware. They were now working
on a dns resolver component which supported DNSSEC although in
practice validating signed zone files would slow down browsing and
currently only 2% of websites had it activated. He didn't mention
strong criticisms of its security by crypto experts such as DJB.
Programming is a task where laziness is a virtue. We write modules to avoid repeatedly writing subroutines. We write subroutines to avoid repeatedly writing loops. We write loops to avoid repeatedly writing code... And there's another level of laziness: we use language shortcuts to avoid writing too much code.
Shortcuts are a controversial subject. Some say they make code faster to write and easier to read. Some say they make it harder to understand for people unfamiliar with those shortcuts. So this article is merely telling you about shortcuts and it's up to you to decide whether to use them or to avoid them. Let's begin, shall we!
Public Getter/Setter for Class Attributes
The concept of a "getter" and "setter" is common in many languages: you have a "thing" in your class and you write a method to set or get the value of that thing. In verbose Perl 6, such a set up might look something like this:
I recently found the old Instapaper extraction rules to rewrite HTML content in a way that is easier on the eyes for consumption. This find has resulted in me writing HTML::ExtractContent::FTR and HTML::ExtractContent::Pluggable to get a nice/concise way to scrape HTML from sites for consumption via RSS or mail.
A few days ago I pushed to GitHub a sample web application written in the MVC style with Dancer2 and DBIx::Class. In this very first post about it, I'd like to highlight
how a route block that processes and validates form data can be made short and neat with the help of HTML::FormHandler.
Consider this HTML form from the application which creates a new user:
Rotor. The word makes a mechanic think about brakes, an electrical engineer about motors, and a fan of Red Letter Media YouTube channel about poorly executed films. But to a Perl 6 programmer, .rotor is a powerful tool for list operations.
Break up into chunks
At its simplest, .rotor takes an integer and breaks up a list into sublists with that many elements:
say <a b c d e f g h>.rotor: 3
>>>OUTPUT: ((a b c) (d e f))
We have a list of 8 elements, we called .rotor on it with argument 3 and we received two Lists, with 3 elements each. The last two elements of the original list we
not included, because they don't make up a complete, 3-element list. That can be rectified, however, using
the :partial named argument set to True:
Social media meta tags are HTML tags that allow you to make the most out of the content you share from a URL. You can determine what information is displayed from a post in Twitter, Facebook, LinkedIn, Pinterest and beyond. It gives developers control over the experience their content produces, as it shows up on these social networks.
I recently had to do some quick search/replace on a bundle of Windows XML files. They are all encoded as UTF-16LE, with the Windows \n\r line endings encoded as 0D 00 0A 00.
Perl can handle UTF-16LE just fine, and it handles CRLF endings on windows out-of-the-box, but the problem is that the default CRLF translation happens too close to the filehandle- on the wrong side of the Unicode translation. The fix is to use the PerlIO layers :raw:encoding(UTF-16LE):crlf - the ":raw" prevents the default CRLF translation from happening at the byte level, the UTF section translates between characters and the encoded bytes, and the final ":crlf" handles the line endings at the encoded-as-UTF16 level.
Knowing that is half the battle. The other half is applying those layers. This was a one-time, quick-and-dirty command-line edit, along these lines:
No, this is not about holy war ! I do respect other tools (-: , really
But rambling on stackoverflow I found quite interesting question about web tests automation. The author started using curl for quite simple test automation task and then changed to selenium web driver, the reason was quite obvious - curl has request oriented design which make it hard to use it when making complicated, sequential requests in a whole test story.
But curl is still cool stuff to get rid of , but you don't have to ... if you use swat PLUS curl.
EDIT: Just a note for PAUSE admins, as some emailed me, any module listed on this post can be given away to anyone who wishes to take it, without any need to ask me first. I do not wish to retain a co-maint either, so please just go ahead and transfer the ownership :) Thanks!
Today's Thursday, and if you regularly read blogs.perl.org, you know today is the first day of my plan to combat bit rot.
Happy Bit Rot Thursday, everyone!
The first step I'm undertaking is reducing the number of projects under my wing by means of deleting them entirely or putting them up for adoption. In total, there are about 107 modules I made adoptable, although some of them are a bundle deal.
Occasionally, the need to write a web service client comes about. For example, when the decision gets made to move away from a piece of software that you run in-house to a suite of hosted apps.
The hosted apps offer RESTful APIs for communication that you will need to use to transfer your data. Let's pretend that there isn't yet a Perl client implementation to fit our needs. So, the first thing that needs to be done is to write a client for these web services (using Mojolicious) to handle the few API methods you'll need.
The client
You end up with an overly simplified client library that might look like this:
Perl 5 has become pretty stable, but there is always room for small
improvements. I would like to discuss yet another "missing" operator.
Its purpose is to make expressions handle some edge cases more gracefully.
It could render some other extensions that have been suggested before
unnecessary.
