Archive for the ‘General’ Category

Dutch student protest

Sunday, January 31st, 2010

This week, various student organisations protest against major cuts in the funding of education and research.

A reader of dutch, can visit their site.

Unique followers on Twitter

Wednesday, December 16th, 2009

As pointed out by Jorg Kennis, Twitter’s new lists feature make it hard to determine the amount of unique followers. I’ve written a simple script, using a slightly modified TweePy, to determine the amount of unique followers.

Example usage:

bas@w-nz ~/twitter-unique-followers $ python twitter-unique-followers.py JorgK -ubwesterb
Password:
rate_limit_status: remaining_hits: 112
Jorg Kennis
 followed directly by 182
 in lists
  RPtje/vriendenbekenden subscribed to by 0
  JorgK/TechNL subscribed to by 0
  sentfanwyaerda/nijmegen1 subscribed to by 9
  JorgK/Friends subscribed to by 0
  sjorsjes/Community subscribed to by 0
  robinspeijer/iPhone subscribed to by 1
  nielsschooneman/iPhone subscribed to by 0
  JeanPaulH/iPhoneclub subscribed to by 5
number of unique followers: 198

You can download it here. I could write a simple webpage with the same functionality, if anyone would mind.

Normul

Sunday, November 1st, 2009

Normul normalizes URLs. It expands shortened URLs:

>>> from normul import normul
>>> normul('http://bit.ly/1I4VQ')
{'type': 'other', 'normalized': 'http://www.shinguz.ch/MySQL/mysql_mv.html', 'original': 'http://bit.ly/1I4VQ'}

And shows useful links for hosted-images:


>>> normul('http://yfrog.com/6c5krj')
{'image': {'full': 'http://img228.imageshack.us/img228/1079/5kr.jpg', 'thumbnail': 'http://img228.imageshack.us/img228/1079/5kr.th.jpg'}, 'type': 'image', 'original': 'http://yfrog.com/6c5krj', 'normalized': 'http://yfrog.com/6c5krj'}

You can find the simple but convenient sourcecode here.

Cantor never bores (1)

Saturday, October 24th, 2009

Given a set of countable sets K, such that K is totally ordered by inclusion, videlicet for every A,B\in K either A\subseteq B or A\supseteq B. Intuitively, for at every step in this chain one element at least must be added, one expects the set K to be countable as well.

Suppose K is countable. Then the union, \bigcup K is a countable union of countable sets, hence countable. (Suppose k: \mathbb N \to K is an enumeration of K and f_i: \mathbb N \to k(i) enumerations of the elements of the chain. Then f_0(0), f_1(0), f_0(1), f_2(0), f_1(1), f_0(2), \ldots enumerates \bigcup K.)

Thus \bigcup K is an upper bound of K. In the poset of countable subsets of some set U, of which \bigcup K is a subset, every non-empty chain has an upper bound. Hence, using Zorn’s lemma there is a maximal element, say M.

Suppose U is uncountable, then there exists a \star \in U \backslash M. M \cup \{\star\} is most definitely also countable and M \subset M \cup \{\star\} which contradicts M’s maximality. We are forced to conclude that there exists an uncountable chain of countable sets.

Cantor’s set theory keeps surprising.

Update: an example of such a chain is the set of the countable ordinals.

Another update: a “more concrete” example are the downsets in \mathbb Q without the empty set and \mathbb Q itself. These downsets correspond to real numbers, see Dedekind Cuts.

Bond against Loanwords

Thursday, September 10th, 2009

Although I don’t bear any animosity against most dutch loanwords (except those Anglo-Saxon), the dictionary of the dutch Bond tegen Leenwoorden is a true joy to read.

21

Monday, August 31st, 2009

Since yesterday I, for the first time, enjoy the anything-but-special age of 21 years.

Windows 7 Sins

Thursday, August 27th, 2009

Windows 7 Sins. I strongly agree with points 1, 3, 4, 5 and 6. The arguments for points 2 and 7 are a bit weak, but I do agree with the conclusions.

For the non US audience, it would have been nice to note that if Microsoft (or the US) would recall all foreign licenses for Windows, our entire government is crippled.

Twitter and Facebook

Friday, August 7th, 2009

were both victim of a DDoS today. Silently, I always hoped that a really long-lasting one will convince them to put effort in a distributed scheme.

Maybe I should be waiting for another Wave.

PijsMarietje

Wednesday, July 1st, 2009

At the faculty for sciences there are canteens for students. In each of these, there’s sound equipment connected to linux boxes. On each of those linux boxes, we run a music-request-server called Marietje. I just finished writing a front-end in Javascript. It wasn’t a pain. As instead, the use of jQuery was a bliss.

The frontend for one of those boxes and the source code (see the ajax folder).

Damned DOM (1)

Monday, June 22nd, 2009

When I wanted to react to any changes to a input textbox immediately, my first instrinct was to use onChange. onChange, however, is called when the input loses focus. onKeyPress then? Isn’t called on backspaces. onKeyDown, maybe? It does get called, but the effect of the keystroke isn’t yet applied, for the return value determines whether it that is done in the first place. (Same story for onKeyPress by the way.) onKeyUp does work a bit, except if someone is holding down a single key, for a while.

The solution: hook onKeyUp and use setTimeout with a timeout of 0. Yugh. I hate DOM.

Big Fat Disclaimer: I actually tested this only on one browser.

Unicode to ASCII (1)

Friday, June 19th, 2009

When I want to generate usernames from real names, which can contain non-ascii characters, you can’t simply ignore the unicode characters. For instance, danielle@blaat.org is the right e-mail address for Daniëlle, danille@blaat.org isn’t.

There’s trick. Unicode has got a single code for ë itself, but it has also got a code which (simplified) adds ¨ on top of the previous character. The unicode standard defines a normal form in which (at least) all such characters, which can be, are represented using such modifiers. If you then simply ignore the non-ascii representable codes, you’ll get the desired result.

In python: unicodedata.normalize('NFKD', txt).encode('ASCII', 'ignore').

However, this isn’t the right solution. For instance, in german, one prefers ue as a replacement of ü over u.

Django annoyances: no reverse select_related

Saturday, May 30th, 2009

Consider

for page in Page.objects.all():
  print page.title
  for comment in page.comments.all():
    print comment
.

There will be a single query to fetch all pages, but there will be for every page another query to fetch its comments. Luckily, Django has got a nice trick up its sleave: select_related. Would I use instead of Page.objects.all(), Page.objects.select_related('comments').all() then Django will use a single joined query to prefetch comments for each page.

However, Django’s select_related only supports forward one-to-many references. No many-to-many; certainly no reverce many-to-many; no reverse one-to-many and no, not even reverse one-to-one (yet). A developer claims it’s impossible (which is bullshit), another asks for patches, which means he doesn’t care doing it himself.

It’s quite easy to manually code around the missing reverse select_related, but it takes too many ugly lines compared to the single word it could’ve been.

Javascript’s stupid Date constructor

Wednesday, April 29th, 2009

new Date(2009, 1, 1) represents the first of February 2009. Not the second of February nor the first of January. Why this stupidity?

Spacing up- and downarrow properly for up- and downsets

Tuesday, March 24th, 2009

f(\uparrow x) is ugly, but f(\left\uparrow x\right.) is nice! The solution: prefix \uparrow with \mathopen.

Fosdem (3)

Friday, February 6th, 2009

In a few hours I’ll travel the short distance to Bruxelles to visit Fosdem. Once again I’m pretty excited :) . Lets hope this time the pink elephants of the Delirium Cafe don’t crush me. If you’re also going, drop me a comment.

Timestamp 1234567890

Thursday, January 29th, 2009

It’s soon. The 14th of februari, 00:31:30 (Europe/Amsterdam). Will the world end? Will ancient libc code giggle and break?

2009

Thursday, January 1st, 2009

Happy Newyear!

On-demand singleton for Python

Saturday, December 27th, 2008

Some singletons eat slightly more resources, than you want to give them for free. For instance, if you have a home-brew threadpool singleton, you don’t want it to create its threads if you are not going to use it. The solution: a simple function that creates a stub which proxies attribute access to an ad-hoc created instance.

Usage: create_ondemand_singleton('mylibrary.Threadpool', MyThreadPoolClass).

Music Animation Machine

Friday, October 10th, 2008

The sound and performance really aren’t that good, but the visual connection is so powerful:

Bach’s little fuge on a Music Animation Machine.

Vim Essentials

Friday, September 19th, 2008

Vim Essentials. Usefull.