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

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:

The program I’ve been [writing about recently][1] has come to a point where I think it can be shown to the wide public. It’s called [Sunflower][2] and has its home on GitHub. It’s nowhere near being completed, and of alpha quality right now, but even at this stage it might be useful.

Clojure by default protects macro authors from incidentally capturing a local symbol. Stuart Halloway describes this in more detail, explaining why this is a Good Thing. However, sometimes this kind of symbol capture is called for. I’ve encountered one such case today while hacking a Swing application.

A couple of weeks ago I finally got around to acquainting myself with [Leiningen][1], one of the most popular build tools for Clojure. The thing that stopped me the most was that Leiningen uses [Maven][2] under the hood, which seemed a scary beast at first sight — but once I’ve overcome the initial fear, it turned out to be a quite simple and useful tool.

I’ve just taken a short breath off work to put some code on GitHub that I had written over one night some two months ago. It is an implementation of the Set game in Clojure, using Swing for GUI.

I do not have time to clean up or comment the code, so I’m leaving it as is for now; however, I hope that even in its current state it can be of interest, especially for Clojure learners.

Fighting procrastination has been my major concern these days. I’ve devised a number of experimental tools to help me with that. One of them is called snafu and can generate reports of your activity throughout the whole day of work. It’s in a preliminary state, but works (at least since I’ve found and fixed a long-standing bug in it which would cause it to barf every now and then), and I already have a number of ideas for its further expansion.

So, how much disk space does your average CL image eat up? A hundred megs? Fifty? Twenty? Five, perhaps, if you’re using LispWorks with a tree-shaker? Well then, how about this?

[nathell@chamsin salza2-2.0.4]$ ./cl-gzip closures.lisp test.gz
[nathell@chamsin salza2-2.0.4]$ gunzip test
[nathell@chamsin salza2-2.0.4]$ diff closures.lisp test
[nathell@chamsin salza2-2.0.4]$ ls -l cl-gzip
-rwxr-xr-x 1 nathell nathell 386356 2008-08-09 11:08 cl-gzip