simpleXML get node child based on attribute
SimpleXML: Selecting Elements Which Have A Certain Attribute Value
Is the set of all finite sequences of letters of Latin alphabet countable/uncountable? How to prove either? Today in Coding/Cryptography class, we were talking about basic definitions, and the professor mentioned that for a set $A=\left \{ \left. a, b, \dots, z \right \} \right.$ (the alphabet) we can define a set $A^{*}=\left \{ \left. a, ksdjf, blocks, coffee, maskdj, \dots, asdlkajsdksjfs \right \} \right.$ (words) as a set that consists of all finite sequences of the elements/letters from our $A$/alphabet. My question is, is this set $A^{*}$ countably or uncountably infinite? Does it matter how many letters there are in your alphabet? If it was, say, $A=\left \{ \left. a \right \} \right.$, then the words in $A^{*}$ would be of form $a, aa, aaa, \dots$ which, I think, would allow a bijection $\mathbb{N} \to A^{*}$ where an integer would signify the number of a's in a word. Can something analogous be done with an alphabet that consists of 26 letters (Latin alphabet), or can countability/uncountability be proved otherwise? And as mentioned before, I am wondering if the number of elements in the alphabet matters, or if all it does is change the formula for a bijection.   P.S. Now that I think of it, maybe we could biject from $\underset{n}{\underbrace{\mathbb{N}\times\mathbb{N}\times\mathbb{N}\times\dots\times\mathbb{N}}}$ to some set of words $A^{*}$ whose alphabet $A$ has $n$ elements? Thanks! How to tell how many CPUs (cores) you have on Windows 7 I would like to align the view straight on to a face, perpendicular to the normal. How do I align the 3D viewport to the face of a mesh? Evolutionarily speaking, why do humans have 46 chromosomes Apparently $1+2+3+4+\ldots+n = \dfrac{n\times(n+1)}2$.  How? What's the proof? Or maybe it is self apparent just looking at the above?   PS: This problem is known as "The sum of the first $n$ positive integers". We roll a six-sided die ten times. What is the probability that the total of all ten rolls is divisible by 6? So the question is really hard I think. I tried using a simple way by calculating the probability of each combination that makes a sum divisible by six, but it would take forever. Does anyone have any ideas?  Suppose that we roll a six-sided die ten times. What is the probability that the total of all ten rolls is divisible by six? Lie Algebra of U(N) and SO(N) U(N) and SO(N) are quite important groups in physics. I thought I would find this with an easy google search. Apparently NOT! What is the Lie algebra and Lie bracket of the two groups? Count below a comment is misleading Why do all Winforms programs require the [STAThread] attribute? Why don’t I have the Get Windows 10 icon? I want to get Windows 10, but I do not see this icon in the notification area (tray):    How do I get the icon to get Windows 10? I'm getting pretty close to the reputation where I can start to edit others' posts, and I'm wondering what the etiquette for when (and when not) to do so. I figure that I should edit in the following circumstances:  Grammatical or spelling errors. Clarification where the meaning is not changed. For instance if the title does not describe the question very well. Where the user has made a very minor mistake that doesn't justify a full post to clarify. To add related resources or links that will help someone answer the post, or provide context  Before the commenting feature was added, I noticed that some moderators edit posts in order to insert a reply or extension to the post. I feel this isn't good etiquette (but I could be wrong) because I don't know what to do with their changes when I come to re-edit or respond. I also feel that I should be very careful not to change the meaning of any question or answer, even if that meaning is misguided. What other rules would be best practice?  Signatures and fluff are discouraged and are fair game to be removed.  See, for example, this post by  and this post by  and also see .  Also see Jeff Atwood's response in the comments to Use dynamic variable names in JavaScript I just recently bought an arduino and requires gcc-avr/avrdude to compile the software. I installed avr for another microprocessor component a while ago but is obviously an outdated version (gcc version 3.3 20030512 (prerelease)) so I went ahead to update these but it didn't work.   (Please note that before hand I also broke my aptdaemon through an incomplete wine installation (couldn't get passed font installation agreement) but I fixed that via a re-installation then accepting the agreement.)   I am trying to update these by running  but the dependencies it requires cannot be installed due to avr... terminal reports   Reading package lists... Done Building dependency tree        Reading state information... Done build-essential is already the newest version. libncurses5-dev is already the newest version. libncurses5-dev set to manually installed. libusb-0.1-4 is already the newest version. libx11-dev is already the newest version. You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: arduino-core : Depends: gcc-avr but it is not going to be installed avr-libc : Depends: gcc-avr (&gt;= 1:4.3.4) but it is not going to be installed Depends: binutils-avr (&gt;= 2.20) but it is not going to be installed binutils-dev : Depends: binutils (= 2.21.0.20110327-2ubuntu3) but 2.21.0.20110327-2ubuntu2 is to be installed libcwidget-dev : Depends: libcwidget3 (= 0.5.16-3ubuntu2) but it is not going to be installed Depends: libsigc++-2.0-dev but it is not going to be installed Depends: libncursesw5-dev but it is not going to be installed libmpfr-dev : Depends: libgmp3-dev (&gt;= 4.2.dfsg-1) but it is not going to be installed python-dev : Depends: python (= 2.7.1-0ubuntu5.1) but 2.7.1-0ubuntu5 is to be installed Depends: python2.7-dev (&gt;= 2.7.1-1~) but it is not going to be installed tk8.4-dev : Depends: tk8.4 (= 8.4.19-4) but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   But running   apt-get -f install   results in   (Reading database ... 163021 files and directories currently installed.) Unpacking binutils-avr (from .../binutils-avr_2.20.1-1ubuntu2_i386.deb) ... dpkg: error processing /var/cache/apt/archives/binutils-avr_2.20.1-1ubuntu2_i386.deb (--unpack): trying to overwrite '/usr/bin/avr-size', which is also in package avr-binutils 2.13.90.030512-2 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Unpacking gcc-avr (from .../gcc-avr_1%3a4.3.5-1_i386.deb) ... dpkg: error processing /var/cache/apt/archives/gcc-avr_1%3a4.3.5-1_i386.deb (--unpack): trying to overwrite '/usr/bin/avr-g++', which is also in package avr-gcc-c++ 3.2.90.20030512-2 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing: /var/cache/apt/archives/binutils-avr_2.20.1-1ubuntu2_i386.deb /var/cache/apt/archives/gcc-avr_1%3a4.3.5-1_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   I have tried running update manager and updating my system via it but all I get is an error message  The following packages have unmet dependencies: arduino-core: Depends: gcc-avr but it is not installed avr-libc: Depends: gcc-avr (&gt;= 1:4.3.4) but it is not installed Depends: binutils-avr (&gt;= 2.20) but it is not installed   which then tells me to try running apt-get -f install which just results the same as last time.  So how can I fix my system, I really need the new avr, please :) BTW, my system is Ubuntu 11.04 I took a bunch of photos at my son's martial arts club using a D90 with a 50mm F1.8.  The club is lit with overhead fluorescent lighting, and I was getting some weird results where some shots are "white", others have an "orange cast", and still others are partly white and partly orange in the same shot.  I suspect it has to do with the combination of the frequency of the light flicker and with the camera shutter speed. Here is a sequence of 3 shots that show the problem.  The shots were taken with 1/500s at F2 and ISO-800 and with Auto-WB.  First shot ("white/normal"):    Second shot ("orange cast" at top):   Third shot ("orange cast" at bottom):   These were taken in burst mode within a second of each other.  Can anybody tell me what is going on?  And, how I can avoid this? Evaluating $\int_0^{\infty}\frac{\ln(x^2+1)}{x^2+1}dx$ The choice between the gerund and the infinitive in a certain construction I am pretty much sure that for native speakers the issue I am going to bring up might look as an uncalled question as they can easily figure out which form of a verbal part of speech should be used, be it a gerund, an infinitive, or a bare infinitive. However, it can be pretty much misleading for a foreigner because the same construction works differently with different words and I don’t see a logical explanation. For example:  The purpose of this article is to analyze the issue…  My hobby is reading. One may assume, and many foreigners really come to this conclusion, that it’s OK to switch the “gerund” and “infinitive” as the meaning will stay the same, that is:  The purpose of this article is analyzing the issue… (same as 1 above)  My hobby is to read. (same as 2 above)   However, as I was told, this assumption is erroneous. Another example: His task was watching after them. (not good) His task was to watch after them. Is there any principle which governs the choice of the right form in such cases? I want to prove that the distance between incentre and orthocentre is $$\sqrt{2r^2-4R^2\cos A\cos B\cos C} $$here $r$ is inradius and $R$ is circumradius. I considered $\triangle API$ ($P$ is orthocentre and $I$ is incentre). I could find  $AP=2R\cos A$, $AI=4R\sin\frac{B}{2}\sin\frac{C}{2} $ and $\angle PAI=\angle \frac{B-C}{2}$. So applying cosine rule I got $$PI^2=4R^2+16R^2\sin^2\frac{B}{2}\sin^2\frac{C}{2} -16R^2\cos A\sin\frac{B}{2}\sin\frac{C}{2}\Bigg(\cos\frac{B}{2}\cos\frac{C}{2}+\sin\frac{B}{2}\sin\frac{C}{2}\Bigg)$$ How to proceed form here ? Cropping the exact same part of several pictures I have several pictures that are exactly the same except for some small variations. It was one picture that was photoshopped in several different ways. Now, I need to crop them all (13 in total) but I need to crop exactly the same part of it. It needs to be pixel perfect.  How do I do that with Pixelmator? Generate multiple renders of same scene, each at a different resolution? I would like to generate several renders of a static scene, each render being a different size (eg 1024x1024, 512x512 etc). Other than the size, each render will be identical.  Is there a way of doing this using, say, the command line, or a script? I am currently doing this by manually changing the dimensions within the render panel every time, but I was wondering if there's a quicker way.  I am using Blender Internal in this specific instance.  Many thanks Can the editor for editing tag descriptions get updated to match the normal questions/answers editor?