I’ve moved to London last September. Like many new Londoners, I have changed accommodation fairly quickly, being already after one removal and with another looming in a couple of months; my current flat was largely unfurnished when I moved in, so I had to buy some basic homeware. I didn’t want to invest much in it, since it’d be only for a few months. Luckily, it is not hard to do that cheaply: many people are moving out and getting rid of their stuff, so quite often you can search for the desired item on Gumtree and find there’s a cheap one a short bike ride away.

This has somehow escaped me: just over a year ago, the Sixth Civil Division of the Lublin-West Regional Court in Lublin, Poland, has opened its online branch. It serves the entire territory of Poland and is competent to recognize lawsuits concerning payment claims. There is basic information available in English. It has proven immensely popular, having processed about two million cases in its first year of operation.

Sequences and iteration

There are a number of motivations for this post. One stems from my extensive exposure to Clojure over the past few years: this was, and still is, my primary programming language for everyday work. Soon, I realized that much of the power of Clojure comes from a sequence abstraction being one of its central concepts, and a standard library that contains many sequence-manipulating functions. It turns out that by combining them it is possible to solve a wide range of problems in a concise, high-level way. In contrast, it pays to think in terms of whole sequences, rather than individual elements.

This is a slightly edited translation of an article I first published on my Polish blog on January 19, 2011. It is meant to target newcomers to Clojure and show how to use Clojure to solve a simple real-life problems.

I’ve recently been developing an iPhone application in my spare time. I’m not going to tell you what it is just yet (I will post a separate entry once I manage to get it into the App Store); for now, let me just say that I’m writing it in JavaScript and HTML5, using [PhoneGap][1] and [jQTouch][2] to give it a native touch.

I keep running into this obstacle every now and then. Consider this example:

> q = []
[]
> for (var i = 0; i < 3; i++)
    q.push(function() { console.log(i); });
> q[0]()
3

I wanted an array of three closures, each printing a different number to the console when called. Instead, each prints 3 (or, rather, whatever the value of the variable i happens to be).

It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration.

— Edsger W. Dijkstra, EWD 498

I’ve been quiet on the front of blogging in English recently. But that doesn’t mean I’ve given up.

After more than a year, I had become tired of maintaining a Blosxom installation. I greatly admire Blosxom, its minimalism and extensibility, but the default installation is just too minimal for my needs. And the plugins tend to have rough edges. Like the Disqus comments that I’ve enabled at one time on the otherwise static blog pages: the correct number of comments appears in some places but not all; besides, they just don’t feel right.

I’ve decided to move my English blog to Posterous. The new address is http://danieljanus-en.posterous.com. This URL (http://blog.danieljanus.pl) will point to the new blog in about a week’s time.

I’m only posting this to let people update their RSS feeds to the new address, which is

There’s been an ongoing debate about how to pass optional named arguments to Clojure functions. One way to do this is the defnk macro from clojure.contrib.def; I hesitate to call it canonical, since apparently not everyone uses it, but I’ve found it useful a number of times. Here’s a sample: