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This is the video from the morning stand-up on everyone's progress for the second day of the 2010 Vienna Perl QA Workshop.

Last day of the hackathon and things are going well. We're doing enough yak-shaving that I think it should be called a Yakathon, but that's a separate issue.

Backtracking is probably the defining feature of Prolog. Abstractly, the execution of a Prolog program can be seen as traversing a tree, looking for a path that fits certain criteria. Each node represents a choice between several options, and are usually referred to as choice points (for reasons that should be obvious). If at any time the path taken is found to be inconsistent with the constraints, execution goes back to the previous choice point and tries the next option. The search is depth-first, left-to-right.

Now, as I've mentioned before, in Parrotlog this is implemented using continuations, based on example code from Graham's On Lisp book (chapter 22). Simply put, continuations allow you to restore the execution of your program to a previous state. For the C programmers, this is simillar to setjmp(3) and longjmp(3), but returning from the originating function doesn't invalidate the saved state. On Lisp chapter 20 has more about continuations, and so do the Parrot docs.

I tried connecting to github again via our strict firewall and http_proxy, which only allows 443 and 80.
corkscrew and simplier proxy tools do not work, and my machine which has 443 redirector had a harddisc crash, so I fixed connect by Shun-ichi Goto
at http://www.taiyo.co.jp/~gotoh/ssh/connect.c
See http://www.taiyo.co.jp/~gotoh/ssh/connect.html

Our squid balances between several session servers so I needed to add realm support.
That was easy. See http://gist.github.com/360940

ProxyCommand connect -d -d -H proxy:8080 %h %p Host github.com User rurban Port 22 Hostname github.com IdentityFile ~/.ssh/proxy TCPKeepAlive yes IdentitiesOnly yes

Host ssh.github.com
User rurban
Port 443
Hostname ssh.github.com
IdentityFile ~/.ssh/proxy1
TCPKeepAlive yes
IdentitiesOnly yes

[remote "origin"] fetch = +refs/heads/*:refs/remotes/origin/* url = http://github.com/mirrors/perl.git

The new and shiny oe1.orf.at is finally online!

As you might expect it's crafted using the finest ingredients of Modern Perl: Catalyst, DBIx::Class, Moose, HTML::FormHandler, KinoSearch. Relaunching the site was a nice project, even though there were some setbacks:

I was forced to switch from Postgres to MySQL (using - the horrors - MyISAM), so I couldn't use any real database features like transactions and referential integrity; the launch date was postponed a few times, so I couldn't help organising the QA Hackathon as much as I wanted (in fact I can also not attend all days, because I want to spend some time with my family before leaving for Berlin / Icleand).

Anyway, after fixing some last post-deployment glitches everything seems to work now. Yay!

I always forget how to do this, so this is just Google fodder.

If I want to checkout a branch from someone else's repository:

git checkout -t -b $local_branch_name $remote_branch_name

The '-t' option says "track the remote branch from my branch". The '-b' option says to actually create the branch with the given name (name will be derived from $remote_branch_name if omitted).

It's so simple that I don't know why I forget this, but I do. Now that I've posted this, I probably won't forget it again :)

This is the video from the morning stand-up on everyone's progress for the first day of the 2010 Vienna Perl QA Workshop.

March has been a very busy time. Although we weren't able to meet the 1st March deadline, the switch to the HTTP submission process has started. Currently it's still considered Beta, but initial problems appear to have been worked out, and the Metabase is receiving reports thick and fast. So much so that some testers started to ramp up their smoker bots again, forgetting that some were still submitting SMTP reports. You can read David Golden's report of his beta test update.

The following is a brief summary of my Perl introduction/promotion talk at BarCamp Kerala 8, held in March 28th, 2010 at Tiruvalla, Kerala, India.

It was my first BarCamp, and the first other conference/camp that I ever attended apart from last year's YAPC::EU::2009 (which was a great experience, by the way!). I was very interested in having Perl promoted among a community that uses/promotes other programming languages. So, I thought of giving a talk and selected the title 'Y Perl?'. The talk concentrated on why Perl should be considered when there are myriad programming languages. Highlights were on the latest buzzwords in Perl, namely Catalyst, Moose and Padre, the community efforts such as Send-a-Newbie, Perl Monks and Perl Mongers.

Blog posts, pictures and tweets have been made on the session. You can find some at: http://bit.ly/brt0KV.

And, most of all, some people met me, expressing their interest in learning the Perl language. I am glad that I was able to encourage them to start taking up Perl. :-)

I am also intending to attend other camps/conferences (near and far), with the same motto of introducing/promoting Perl.

Hate the Perl debugger? Want it to do more? I do. For example, I hate it when I see this:

  DB<1> x $before                                                                                            
0  HASH(0x100e37fd8)
   'foo' => ARRAY(0x100c5f1d8)
      0  1
      1  2
      2  4
   'guess' => CODE(0x100dc0d78)
      -> &main::__ANON__[run.pl:13] in run.pl:10-13
   'this' => 'that'
   'uno' => HASH(0x100db9000)
      'this' => 'that'
      'what?' => HASH(0x10088dfc0)
         'this' => 'them'

At the end of last week, I sent mail to all CPAN authors letting them know that they could delete older distributions from author directories. CPAN is pretty large: last week it was almost 8 GB, and today it's almost down to 7 GB. That puts the Schwartz Factor at about 1/7th. We can do better.

It's not the size that's the problem so much: disk is cheap (still, no need to waste it). The more distributions CPAN stores, the more the masters need to check when a mirror wants to rsync. For the most part, mirrors only need to delete the files that disappeared and want the ones that appeared. The other files (aside from the PAUSE files such as CHECKSUMS) should not have changed. The rsync program doesn't know anything special about CPAN though, so it still does all its work.

Most aspects of the first round between Dancer and Mojo are covered in Alexis' post - a recommended read. However - with your approval, or not - I'd like to add another side of it, our overall developer understanding of the contest.

While it seems fun to "win" something, what we the developers (and I'm assuming it's pretty much the same for the Mojo people) liked most about the competition was that we'd get a complete understanding of the end-user learning experience.

David N. Welton:

This is actually, in my opinion, an interesting phenomenon in languages: you risk hitting some kind of local maximum when your language is popular enough to have a lot of users who will be angry if things are changed or accidentally broken in the course of big upheavals. So you have to slow down, go carefully, and not rock the boat too much. On the other hand, there is an opportunity cost in that newer languages with less to lose can race ahead of you, adding all kinds of cool and handy new things, or simply fix and remove “broken” features.

Oh brother.

And this bit as well:

The syntax, for your average programmer who doesn’t want to go too far out of their comfort zone, is perhaps a little bit further afield from the C family of languages than they would prefer. Still though, a “human” problem, rather than a technical one. Perhaps, sadly, the message is that you’d better not “scare” people when introducing a new language, by showing people something that [looks] at least a little bit familiar.

Arrived in Vienna last night and walked across the city center to get to the hotel. It's my second time in Vienna and I love how beautiful it is.

I'm about to leave for Vienna for the 2010 Perl QA Workshop, so now it's time to start thinking about my secret project. I've saved it especially for something to do on the plane.

A couple months ago, David Golden and I got together to talk about what a new CPAN.pm client would look like. Now, remember that both of us have our noses deep in the CPAN.pm source, and both of us have thought, on several occasions, that we should refactor CPAN.pm. Gabor, who is also going to be in Vienna, even went so far as to separate each package into its own file back in October 2008.

Here are the slides I've use while delivering my Fishing for Perl: The Perl New User Experience talk. These are not really slides, in any sense, the Powerpoint one or else, but actually a .pdf file that I generated out of this LaTeX source.

My main work method in creating this talk was two-fold. One, I jotted down ideas I had on the most immediate means, paper or electric (I found Google Wave to be an excellent tool for this, the only actual use I found for it). Two, I edited those ideas to a LaTeX document until they actually formed what seemed (at the time) a sensible narration. I also tend to follow the idea that if you can understand the talk by just reading the slides then the talk has no value. This actually means you may not understand much of what I'm talking about by just reading the slides.
That's OK, because I intend to use that as a base for several posts here.

In the I went with the simple solution to the problem of unification. Variables point to other variables, and in the end a variable either points to a term, or nothing. What happens when you unify X with Y, Y with Z, and Z with X should probably not be considered just yet, and will probably have to be fixed at some point. But that should be reasonably simple. Finding cycles in a graph is after all a well-known problem.

This means that the core infrastructure I need should now be in place: unification, backtracking and cuts (a post on those last two is coming up). Now it's time to start looking into writing the grammar, and figuring out how to represent rules and the fact database.

I know why "date" and "time" are in there, but I suspect it's not common for most folks.

~  $ history | awk {'print $2'} | sort | uniq -c | sort -k1 -rn | head
 255 git
 174 fg
 108 vim
  79 prove
  58 ack
  56 cd
  51 ls
  42 time
  41 rm
  31 date

When writing Perl, people often create hybrid interfaces that accept either a reference to an array or hash, a string, or a reference to a string. The Perl code to do appropriate conversion behind the scenes is usually trivial. Some even use this to overload their interface to do something entirely unrelated depending on the type passed in. However much one might loathe such interfaces, when replacing Perl code with XS, one usually has to reproduce the properties of the original. That is what this entry is about.

A rather reasonable example of such a hybrid interface is PPI::Document whose constructor accepts either a string (interpreted as a file name) or a reference to a scalar (interpreted as a reference to a scalar containing the code as a string). While (different) named arguments would have been clearer for a casual reader of the resulting code, this case of an overloaded interface is a generally reasonable optimization.

Last week, Marcel Grünauer (hanekomu) tweeted about his PAUSE deletions possibly triggered by one of the recent discussions about the CPAN ecosystem (and mirroring deficiencies). PAUSE sends deleted files to the BackPAN which has everything released to CPAN. However, selecting the files to delete is not much fun since PAUSE UI is sadly not dynamic and if you have lots of distributions you'll have even more released files on PAUSE.