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Recursively set ownership in Windows

rattle remark, technology 2013-04-02

I have a folder data with stuff in it. I am not using an Administrator account on my Windows machine, and that folder is supposed to be owned by my user. When you search for how to take ownership of all files and folders in a certain directory recursively, you get told to use TAKEOWN, a lot. Well, it has a little catch: You can only really use it to take ownership. Not to give it. A much more giving command is

ICACLS C:\data /setowner rattle /T

Oh yea, it's the /T switch that makes it recursive.

Characters of the Symmetric Group

rattle code, mathematics 2013-03-27

Harm Derksen brachte uns schon im Jahre 1998 die weltschnellste Methode zur Berechnung irreduzibler Charaktere der symmetrischen Gruppe. Aber in seinem preprint, Computing with Characters of the Symmetric Group, bleiben einige Fragen offen, die ich hiermit zu klären versuche.

» The code to end all codes «

Die Welt ist einen halben Herzschlag alt. Der unsterbliche Prophet meditiert seit Anbeginn der Laufzeit auf dem তাজমহল und studiert die heiligen 12 Zeilen C-Code, die jede SAT Instanz in $\mathcal{O}(n^{9699690})$ lösen. Wenn der Puls eine Ganzzahl wird, so wird er erwachen und die Wahrheit verkünden, und Lob wird gepriesen, und Licht wird ewig scheinen auf die Kinder des Schaltkreises. Denn er ist der Taktgeber, und an der Spitze des Signals wird es sein, wenn er uns erscheint. Buch Arithmæl Circulæ, Vers 21:7 Wollen Sie mehr wissen?

Lenovo System Update somewhat demystified

rattle remark, technology 2013-03-09

Suppose you have a Laptop, which therefore must be a [ThinkPad](http://www.lenovo.com/products/us/laptop/thinkpad/). Let's also assume that you [use Windows 2008 as a workstation](http://www.win2008workstation.com/), just like [I do](/2012/03/22/turning-windows-2008-r2-into-a-workstation/). Then, you might run into some issues with [Lenovo System Update](http://support.lenovo.com/de_DE/detail.page?LegacyDocID=TVSU-UPDATE). To be precise, it tells you: > An error occurred while gathering user information. Then it stops. I will provide a solution to this problem which is not specific to Windows 2008 R2, and therefore, I hope that my solution will also work for future versions of Windows that are not out-of-the-box supported by SystemUpdate. Do you want to know more?

Nested case distinctions in LaTeX

rattle latex 2013-03-07

Trust me, I am not one to enjoy deeply nested case distinctions in a mathematical proof. In fact, I'd rather there were no case distinctions necessary at all. However, to quote the famous mathematician Nikolai Nowaczyk: > Some theorems have beautiful proof - and some theorems are worth fighting for. Anyway. If you have to do it, you should do it in beautiful $\KaTeX$. Do you want to know more?

Convert WAV to MP3 with VLC

rattle remark, technology 2013-03-05

If you like electronic music, you obviously lurk getworkdonemusic.com all the time with jDownloader running, so you can copy the link to any nice track on the air and download it, slowly aquiring a groovy selection of electronic music for the lonely train hours where you have to get work done, offline style. Sometimes, however, these tracks are in wave format, for reasons that are completely beyond me. A quick google search for »convert WAV to MP3« points you towards a huge selection of shitware, when it could be so much easier: Fire up VLC, the best media player in the world ((This post refers to VLC media player 2.0.5 Twoflower.)) and go * Media, Convert/Save (Ctrl+R) * Add your file to the list. * Click the button that says Convert/Save. * Select a destination file. * Set the profile to Audio - MP3 and hit Start. Also, make sure you don't have VLC set to loop, because otherwise it'll spend the next few hours overwriting that file with the same converted MP3 again and again. True story.

Thunderbird: Mark all drafts as read

born technology 2013-03-04

I wasted like 60 seconds a day marking drafts in Thunderbird as read after using the SendLater-Plugin. The following AutoIt-Scripts that runs in background now saves this precious amount of time!

$x_offset = 80
$y_offset = 140

TraySetIcon('C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe', 1)

While 1
    WinWait('[TITLE:Send this email later; CLASS:MozillaDialogClass]')
    WinWaitActive('[REGEXPTITLE:Mozilla Thunderbird]')
    Sleep(1000)
    $tb_pos = WinGetPos('[REGEXPTITLE:Mozilla Thunderbird]')
    $mouse_pos = MouseGetPos()
    MouseClick('right', $tb_pos[0]+$x_offset, $tb_pos[1]+$y_offset, 1, 0)
    Send('{UP 4}{ENTER}')
    MouseMove($mouse_pos[0], $mouse_pos[1], 0)
WEnd

Animated LaTeX

rattle latex, mathematics 2013-03-01

After discovering the toggle command available in MathJax, I immediately went to asked the capable people of tex.stackexchange whether this could be done inside a PDF file. And indeed: It can be done!

\documentclass{article}
\usepackage{animate}

\begin{document}
\begin{animateinline}[step]{1}
  \strut$x=1$
\newframe
  \strut$x=2$
\newframe
  \strut$x=3$
\end{animateinline}
\end{document}

Now, what do I want with this package? I want to do abstract nonsense. A diagram-based proof should, in my opinion, be a slideshow. You start with the diagram that is your assumption and by simply interacting with the diagram (clicking it), in each step, a new arrow is constructed from some universal property. I wanted to write a neat animated PDF with an abstract nonsense proof of the famous Snake Lemma, and there is a great book by Francis Borceux containing a proof, but unfortunately, I was unable to overcome a difficulty with the proof, so that will have to wait until someone answers my question.

Blog Size

rattle remark

Looking at Roman's beautiful blog, I really couldn't take it no more. I finally removed that scourge of a tiny font size from the blag, now it is actually possible to read everything on a commonly shaped screen. At this point I wished this had been done in LESS, because then I would probably only have to change two variables in order to achieve, what now took me, approximately one hour.

Extension by Scalars and Dimension

rattle mathematics 2013-02-26

Let $K\subseteq L$ be a field extension, and let $V$ be a $K$-vector space. The extension of $V$ by scalars in $L$ is the tensor product $E=V\otimes_KL$. I will prove that every $L$-vector spaced is obtained as some extension in this way and that $\dim_L(E)=\dim_K(V)$. Do you want to know more?

Windows Shortcuts

born technology 2013-02-23

I learned three new Windows shortcuts today: * Win + Pause: System Properties * Alt + Space, n: Minimize window * Alt + Space, x: Maximize window Especially the latter two are very useful for me.

Offline Navigation

nikno technology 2013-02-20

On Android Smartphones you can use GoogleMaps app for Navigation — unfortunately, it requires an internet connection and this can be very expensive if you use this outside your home country. Therefore, I was looking for a free app which supports downloading the entire maps for certain regions. I think Navfree does the job.

A Yay for Community-Managed Textbooks

rattle mathematics, remark 2013-02-07

Most people probably know about the stacks project, but fewer might have heard about the CRing project. Now, there might be certain disadvantages to having a large number of contributors to a single document, but I would like to put some emphasis on the one, big advantage: You actually end up with a very complete reference, not just the narrower standpoint of one or two authors. If done correctly, group efforts of this sort are the perfect way to cover all basic (whatever that means) knowledge in some field. I really hope to see more areas pick up on the idea.

Sum over Product Lemma

rattle mathematics 2013-01-31

I was doing some math with Lars and during our session, we came up with the following inequality. Let $a_1,\ldots,a_r\in\mathbb N$ be integer numbers with $a_i\ge k$. Then, \[ \frac{\sum_{i=1}^r a_i}{\prod_{i=1}^r a_i} = \sum_{i=1}^r \frac{1}{\prod_{j\ne i} a_j} \le \frac{r}{k^{r-1}}= \frac{rk}{k^r} \] The inequality is completely obvious, but I found it useful and didn't want to forget about it.