Category: Programming

Categories
Programming

Line of Succession

I’m a republican. No… wait… come back! That’s not what I mean.

I’m a long way from being a supporter of the Republican Party. I mean “republican” in its older meaning of “someone who thinks their country should be a republic. That is to say, I’m not a big fan of the British royal family.

But while I believe that the UK should get rid of the royal family, I’m also fascinated by them. In particular, I’m fascinated by the laws that determine the line of succession – that is the list of people in line to take over the throne.

When I was a child I believed that the line of succession was a big list that had every British person’s name on it and that it would only take a single catastrophic event to propel my name to the top of that list. Later on I discovered the Act of Settlement (1701), which is the law which actually defines the line of succession (modulo a few later tweaks). I was disappointed to find that there were only a few thousand people on the list (and that didn’t include me!) and also that a lot of the people on the list weren’t British (largely due to Queen Victoria’s children marrying royalty from all over Europe).

A few months ago, I started to think about building a web site that would allow people to explore the line of succession through time. And over the last few weeks, I have build the site. It’s at lineofsuccession.co.uk. On the main page, you will see the current line of succession. And in the navigation bar is a drop-down menu that allows you to move to a few interesting data (the days that the last four monarchs came to the throne) and a date picker allowing you to choose any random date.

The code is, of course, on Github. The web app is a pretty standard Dancer2 application which really doesn’t do anything clever. Most of the complexity in an application like this is in the data gathering.

Currently I have just over a hundred people in the database. That’s most of the descendants of Edward VII (there a few lines that I haven’t completely filled out yet), but eventually I want to go back to all include all of the descendants of Electress Sophia (the person who the crown was “settled on” in the Act of Settlement). I’ve heard estimates that she has somewhere between 5-6,000 descendants. So I have a bit of work to do there!

Other than more people, I have a few other things I’d like to add to the site:

  • More names and titles People on the line of succession tend to have many titles during their lives. The data model already supports the concept of a name that is only valid on a range of dates (see the current queen described as Princess Elizabeth of York on the day before her father became king,  Princess Elizabeth when he was king, Duchess of Edinburgh when she got married and, finally, Queen Elizabeth II when she became queen. But tracking down and adding all that data is hard work.
  • Excluded people Catholics are excluded from the line of succession. And people who married Catholics were also excluded until recently. Oh, and obviously children born out of wedlock (that’s more common than you might expect in some of the more obscure branches of the modern Windsor family). Of course, people can convert to (and from) Catholicism at any time, so supporting that in the app would mean implementing some kind of “exclusions” data. But it would be good to show these people, perhaps in a dimmer font.
  • Tree views Today I added text to each person showing their relationship to the monarch. That can help a reader to visualise the family tree, but I’d like to make it more explicit. Nested lists could make it easy to see the relationships. And, later, perhaps show the whole tree using SVG.
  • Position changes Sometimes the line of succession feels a bit like the pop charts. Take Prince Harry, for example. He entered the chart at position 3 and stayed there until Prince George bumped him down to number 4 and Princess Charlotte pushed him down to 5. He’s only likely to fall further in the coming years. The same thing happened to Princess Anne, who was number 3 when she was born, but currently languishes down at number 12. I think it would be interesting to plot those changes over time.
  • Make it prettier Bootstrap does the job. It allows design dunces like me to get a reasonable-looking site up and running in no time. But it’s not very regal.

Anyway, there’s my current itch scratched. And, as in so many cases, it’s just given me more itches. But please let me know if you find the site at all interesting or useful.

Categories
Programming

I Wrote Some Perl

Ok, yes, I’ve been writing Perl for over twenty years. But Perl 5.26 was released this week and for the first time, my name is mentioned in the release notes. Because I have not one, but two fixes in this release of Perl.

The first is this commit which fixes a piece of documentation to make it clear that grep() returns a list, not an array.

The second is this commit which fixes some sample code so that it runs without warnings under use strict.

It’s a small start, I admit, but I have a taste for it now. In a years time, I hope to report that I have more than two commits in Perl 5.28.

And you can help too. Instructions on how to contribute are in the perlhack manual page. There is more information in perlhacktips and perlhacktut.

The people working on Perl all do a great job. But it’s a hard job and it might just get a little easier if more of us helped out.

Categories
Programming

Shaving Last.FM Yaks

Long-time readers might remember that I once had a bit of an obsession with aggregating web feeds on sites that I called “planets”. I wrote Perlanet to make this job easier and I registered the domain theplanetarium.org to host these planets.

The planets I built were of varying levels of usefulness – but of all of them, planet davorg was the vanity project. It was simply a way to aggregate all the web feeds that I produced. There were feeds from various blogs along with things like Flickr, Twitter and CPAN.

One of the things I liked about planets was that they were self-maintaining. Once you’ve configured a planet, it will just keep on running (well, as long as the cron job is running). If the web feeds they are aggregating have new content, the planet will have new content. And many of the feeds that powered planet davorg were still running.

But last weekend I found a couple of  problems with it. Firstly, it looked like it was designed by an idiot. Which, to be fair, it was. Web design was never my strong point. But we have Bootstrap now, so there’s no excuse for web sites to look that bad. So that’s how I spent the first hour or  so – slapping a bit of Bootstrap paint onto the site. I think it now looks acceptable.

The second problem was that not all of the feeds were still running some of them (Delicious, for example) were just dead. I can’t remember the last time I posted anything to Delicious – can you? So I spent some time tweaking and fixing the feeds (replacing CPAN with MetaCPAN, for example). Most of this was easy.

However, one feed was a problem. My Last.fm feed was dead. For over ten years I’ve been “scrobbling” ever song I’ve listened to and one of the feeds I was aggregating was that list. According to this page on their web site, my feed is supposed to be at http://ws.audioscrobbler.com/1.0/user/davorg/recenttracks.rss – and that was the URL in my Perlanet configuration. But it doesn’t work. It returns a 404 error.

I tried to contact someone at Last.fm to find out what was going on, but I haven’t got any kind of response. It looks like they’ve been running on a skeleton staff since CBS took them over and they don’t seem to have the time to support their users (not, I suspect, a recipe for long-term success!)

But there was one possibility. You can get the same data through their API. And some quick experimentation, revealed that their API hasn’t been turned off.

And CPAN has Net::LastFM which will make the API calls for me. Ok, so it hasn’t been updated since 2009, but it still works (I’ve just noticed that there’s also Net::LastFMAPI which is a little more recent).

So it just took a small amount of work to write a little program which grabs uses the Last.fm API to get some JSON that contains the information that I want and convert it to an Atom feed. In case this is useful to anyone else, I’ve put the code on Github. Please let me know if you do anything interesting with it.

And if anyone from Last.fm reads this. Please either turn the web feeds back on or remove the documentation that still claims they exist.

Categories
Programming

Two Weekend Projects

It’s far too long since I’ve posted anything here. I’ve no excuse really. Following the end of my contract in Canary Wharf, I was off work for seven weeks. OK, I was on holiday for two of those weeks, but that still leaves five weeks when I could have been doing something constructive, but actually just spent a lot of time watching Netflix.

But there were a couple of things I did. Neither of them took more than a few hours, but I thought it was worth writing them up – if only to give an example of a couple of really useful (to me, at least) things that I was able to build really quickly with Perl.

Cooking Vinyl

If you were a music fan in the 1990s, then there’s a good chance that you own at least one album released on Cooking Vinyl Records. At times, it seemed like pretty much every album I bought was released by them. Back in 2005, I wrote a blog post where I tried to explain how much they meant to me.

In particular, they produced a series of compilation albums that introduced me to so many of my favourite acts. Ten years ago, I tried to find a definitive list of all of the songs and artists which appeared on those compilation albums. As I failed to find one, I created it myself. At the time, it was a static list of albums which listed the tracks and artists on each of the albums. For ten years I’ve had it in the back of my head to do something more interesting with the data. A few weeks ago, I finally got round to it.

As I said, the original page just had a list of albums with artists and song titles. That’s useful, but it would be more interesting to be able to cross-reference the data in various ways – list all of the albums that an artist appeared on, for example. And for that, we need a database.

If you’ve come on any of my database training course over the last ten years, you’ll know that I use a CD database example. The model that I use is pretty simple and, in particular, it assumes that all tracks on a given CD are by the same artist. As I say in the class “various artists compilations don’t exist in this simplified universe”. Obviously, that’s not going to work in this example. So I needed to come up with another database model.

Compilation album data model
Compilation album data model

Here’s the data model I designed. You’ll see that it all hinges on the track table. A track is an instance of a particular song, recorded by a particular album appearing on a particular album. The only extra data on the track table is the “number” column which allows us to declare the order in which tracks appear on an album.

Advanced students will have spotted an omission from the data model. An artist might well have different versions of a song. There could be the original version, an edited single version and many live or remixed versions. So actually, we could add a “recording” table and it’s the recording that appears on an album. That’s, perhaps, an enhancement for the future.

Having designed the database the rest of the code just falls out really. I already had a data file so it was just a case of parsing that and inserting the data into an SQLite database. DBIx:Class (and, particularly the find_or_create method) makes this trivial. I then wrote another program that generated the web site using the Template Toolkit. Nothing complex there at all.

The site is at http://cookingvinyl.dave.org.uk/. And all of the code is on Github. It could do with being made a bit prettier – perhaps I can add some pictures.

Why not have a look. And check out some Cooking Vinyl recordings.

Tower Bridge

I’ve lived in London for thirty-five years. And in all that time I have never seen Tower Bridge opening. Oh, I’ve seen it when it’s  open, but I’ve never been in the right place at the right time to see it actually opening. As a Londoner, that’s a matter of supreme embarrassment to me.

But the office I’m working in currently is three minutes walk from Tower Bridge. All I need is a way to get a notification a few minutes before the bridge lifts. Surely, there must be a way to get that?

Sadly, no. The Tower Bridge web site has a page listing the upcoming lifts, but no service that would send any kind of notification. So, once again, it was up to me to provide one. I asked the London Perl Mongers on IRC what would be a good way to get notifications of upcoming events on an Android phone and Ilmari pointed out that the obvious method was to create a calendar that could be read by the calendar app on my phone.

So that’s what I’ve done. I use Web::Query to scrape the data from the Tower Bridge web site (doing some over-complicated madness to account for the fact that they are missing the year from their dates) and then create a .ics file using Date::ICal and Data::ICal. I also create a JSON version of the data in case it’s useful to anyone (if it is, please let me know).

The site is at http://towerbridge.dave.org.uk/ and (of course) the code is on Github.

So, there you are. Two (hopefully) little projects that I threw togther in a very small amount of time using the power of Perl. Please let me know if you find either of them useful.

Categories
Programming

Hacking Symbol::Approx::Sub

In October, for (I think) the second year, Digital Ocean ran Hacktoberfest – a campaign encouraging people to submit pull requests to Github repos in exchange for free t-shirts.

A few of us thought that this might be a good way to do a small bit of easy Perl advocacy, so we tagged some issues on Perl repos with “hacktoberfest” and waited to see what would happen.

I created a few issues on some of my repos. But the one I concentrated on most was symbol-approx-sub. This is a very silly CPAN module that allows you to make errors in the names of your subroutines. I wrote it many years ago and there’s an article I wrote for The Perl Journal explaining why (and how) I did it.

Long-time readers might remember that in 2014 I wrote an article for the Perl Advent Calendar about Perl::Metrics::Simple. I used Symbol::Approx::Sub as the example module in the article and it showed me that the module had some depressingly high complexity scores and I planned to get round to doing something about that. Of course, real life got in the way and Symbol::Approx::Sub isn’t exactly high on my list of things to do, so nothing happened. Until this October.

Over the month, a lot of changes were made to the module. I probably did about half of it and the rest was pull requests from other people. The fixes include:

  • Better tests (and better test coverage – it’s now at 100%)
  • Using Module::Load to load module
  • Using real exceptions to report errors
  • Updating the code to remove unnecessary ampersands on subroutine calls
  • Fixed a couple of long-term bugs (that were found by the improved tests)
  • Breaking monolithic subroutines down

And I’m pretty happy with how it all went. The work was mostly completed in October and this morning I finally got round to doing the last couple of admin-y bits and version 3.0.0 of Symbol::Approx::Sub is now on the way to CPAN. You still shouldn’t use it in production code though!

Thanks to everyone who submitted a pull request. I hope you did enough to earn a free t-shirt.

If you want to get involved in fixing or improving other people’s code, there’s the 24 Pull Request Challenge taking place over Advent. Or for more Perl-specific code, there’s the CPAN Pull Request Challenge.

p.s. In the Advert Calendar article, I linked to the HTML version of the results. For comparison, I’ve also put the new results online. It’s a pretty good improvement.