This time, the first challenge was more difficult than the second one. So, let’s start with the easier one.
Centring
To centre an array of lines, just find the longest one, and prolong each line on both sides so its length is the same as the maximal one. When printing, we don’t have to prolong the right hand sides of the lines, prefixing the spaces to the left is enough.
#!/usr/bin/perl
use warnings;
use strict;
use Path::Tiny;
use List::Util qw{ max };
sub center {
my @lines = @_;
my $max_length = max(map length, @lines);
return map +(' ' x (($max_length - length) / 2)) . $_, @lines
}
my @lines = path(shift)->lines;
print for center(@lines);
Write a script that computes the first five perfect numbers. A perfect number is an integer that is the sum of its positive proper divisors (all divisors except itself). Please check Wiki for more information. This challenge was proposed by Laurent Rosenfeld.
(reposted from the now-sadly-extinct http://use.perl.org/use.perl.org/_Mark+Leighton+Fisher/journal/40449.html)
You can search on hierarchies in Lucene if your hierarchy can be represented as a path enumeration (a Dewey-Decimal-like style of encoding a path, like "001.014.003" for the 3rd grandchild of the 14th child of the 1st branch).
For example, a search phrase like:
hierarchy:001
would return only the direct children of the 1st branch, while:
hierarchy:001*
would return all descendants of the 1st branch.
To get only the children of a particular node, you specify only that node, like:
hierarchy:001.014.003
To get all of the descendants you specify everything that starts with that node:
hierarchy:001.014.003*
To get only the descendants after the children (grandchildren, etc.), you specify:
hierarchy:001.014.003.*
2019-05-21: I haven't tried it, but it looks like you could do this right in Perl with the now-quiescent Apache Lucy loose port of Lucene.
At the Perl Toolchain Summit 2019 in Marlow/Bisham, I added a feature to manage PAUSE permissions per distribution, which I hope makes it easier for you to grant permissions to other contributors.
This was the fifth year of my PAUSE hacking. I had spent first two years to port PAUSE web interface from mod_perl to Plack to get rid of deprecated tools, and another two years from Plack to Mojolicious for more structure and understandability. PAUSE on Mojolicious was deloyed into production at the 2018 summit (I'm sorry I couldn't report this last year). However, it was still checked out from my mojo_wip branch, and fell back to the old PAUSE on Plack from time to time, e.g. when something weird was found in my branch, or to use new maintenance tools my branch didn't have. One of my goals this year was to resolve this issue.
I know I’m late with my blog post. I had the solutions ready in time, but I suffered a dental abscess and spent the rest of the week either praying for the painkillers to kick in or sleeping when they did.
Perl RT 133292 is a request to expose the internal perl subroutine that does string interpolation, so that one does not need to figure out how to double-quote a string (escaping where necessary) when feeding it to eval() as a quick-and-dirty templating system.
In fact, there is no such subroutine (the parser makes an interpolation into a concatenation), and anyway why not just use sprintf()?
For someone determined to dive down this rabbit hole, though, Unicode offers another way out: use generic quotes; that is, qq, but delimit the string with a noncharacter. This was suggested to me when I saw the Incompatible Changes section of the Perl 5.29.0 perldelta(1). They're making unassigned code points illegal delimiters? They were legal before??? What else is legal that I did not know about????? (2)
I was fortunate to be able to attend the Perl Toolchain Summit again this year. The MetaCPAN team worked hard. I've tried to summarize our efforts with this post.
I just added a feature called "Merge Keys" to
YAML::PP. No Perl YAML module supports
this so far. You can merge mappings defined elsewhere in your YAML document into
other mappings with that. Here is a short example:
Every year at the Perl Toolchain Summit (PTS), there is some work done on PAUSE, but 2019 was a vintage year. In this blog post we'll remind you exactly what PAUSE is and does, and then take you through the major bits of PAUSE work done.
This blog post is brought to you by ZipRecruiter, who were a Gold sponsor for the PTS. More information about ZipRecruiter is provided at the end of this article.
MTA-STS (RFC8461) is a new standard that makes it possible to send downgrade-resistant email over SMTP. In that sense, it is like an alternative to DANE. It does this by piggybacking on the browser Certificate Authority model.
There is a validator here which defaults to checking gmail.com, and possibly can answer your questions about it without the "tl;dr" factor of the RFC.
This perl script was posted on the Exim mailing list, and is designed to work with the Exim Perl interpreter. On demand, this script will check if MTA-STS data is in a LMDB database. If it is not then it will poll a domain for MTA-STS info and put the info into the database. Then, respond to EXIM with required info for processing the outgoing email.
This script provides reboot resistant caching of MTA-STS data. And if the database is not found, it will reconstruct the database and restart the caching.
Exim is the most popular MTA to if you are running your own mail server this is a good chance you are using it.
One thing about Map::Tube that kept annoying me for long time, is not able to format the result of search without bending the back. Let me share the details what I am talking about. Earlier, before v3.62, this is what you would had to do to format the result.
use strict; use warnings;
use Map::Tube::London;
my $map = Map::Tube::London->new;
my $route = $map->get_shortest_route('Baker Street', 'Wembley Park');
print $map->to_json($route);
We have a plugin Map::Tube::Plugin::Formatter that provides the functionalities. It currently supports the following formats.
1. XML
2. JSON
3. YAML
4. STRING
If you noticed the line "print $map->to_json($route);", this is plain ugly, in my opinion and I always wanted to clean up. Yesterday, I finally got that done. Now the above code can be simplified as below:
use strict; use warnings;
use Map::Tube::London;
my $map = Map::Tube::London->new;
my $route = $map->get_shortest_route('Baker Street', 'Wembley Park');
print $route->to_json;
Print all the niven numbers from 0 to 50 inclusive, each on their own line. A niven number is a non-negative number that is divisible by the sum of its digits.
A Niven number or harshad number is a strictly positive integer that can be evenly divided by the sum of its digits. Note that this property depends on the number base in which the number is expressed (the divisibility property is intrinsic to a pair of numbers, but the sum of digits of a given number depends on the number base in which the number is expressed). Here we will consider only numbers in base 10.
Please also note that 0 cannot be a divisor of a number. Therefore, 0 cannot really be a Niven number. We'll start at 1 to avoid problems.
This year, I was happy to hear I would be invited again to the Perl Toolchain
Summit, an annual event with about
30-35 people hacking four days on toolchain related stuff, improving user
experience.
This time it was held in Marlow, a small city two hours from London, in an
old abbey which was beautiful (but cold!).
As we continue to build Tau Station, the free-to-play narrative sci-fi MMORPG (what a mouthful!), we find our code base is getting larger and larger. As with any large codebase, we've found ourselves sometimes mired in technical debt and need a way out.
One simple hack I wrote has saved so much grief with this process. I can run this from the command line:
And it automatically renames the module for me, updates all references to it, creating directories as needed, renaming test classes built for it, and uses git.
Yesterday was the saddest day for me as the daily CPAN upload chain was broken again. It reminded me of the day when it happened last time when I was on 1027 days. It was the first day of my holiday in India. It was easier to cope with the heartbreak that time as I was with my parents. Like always, I had delegated the uploading task to my younger brother, who lives in Pune, India. But for some reason, he forgot to upload the tarball and when he realised it was too late.
Around 12:15pm yesterday I was about to do routine daily upload to CPAN. I immediately got "Internal Server Error" first. I have never ever seen that error before. Not sure what to do, I jumped on Twitter and asked for any advise.
Olaf Alders responded first and suggested to reach out to #toolchain (IRC).
Little later Neil Bowers replied that he contacted Andreas and Perl NOC team by email.
The Perl Toolchain Summit (previously known as the Perl QA Hackathon) is an annual coding workshop for people involved in the Perl toolchain, testing, quality assurance, and related issues. I was glad to be invited to this one, my fourth.
