I'd like to know if there a chance to root my Acer tablet  to install ubuntu on it. There is method under Windows but this  did not work on my tablet.   I've still seached the internet but can't find a solution. Can some one help me?

I would like to port Ubuntu Touch to a device that is currently not supported. What are the requirements for doing this and where do I begin?


I have 28,000 files of size 6.7 GB in the directory aaa/input. I need create TAR files in the directory aaa/output, such that each TAR file cannot exceed 1.9 GB, so I have to tar the 28,000 files into 4 TAR files (6.7/1.9) as Log_(current date)_01.tar Log_(current date)_02.tar ... etc.  such that each tarball is less than 1.9 GB. Is there a way to do this using a Unix script?

I have a very large folder that I am trying to create a tar archive of. The issue is I don't have enough extra free space to store the entire archive so I want to create say 100-200GB chunks of the archive at a time and transfer those individually to cloud storage. I need to be able to control when new chunks are created so my HDD doesn't fill up but all of the commands i've found to create split tarballs always create it all at once, in the same directory. The closest solution I found was from  but all the responses base the archives on number of files, not size which is important for my use case as my file sizes are unevenly distributed.


The plural of giraffe, according to  and some other dictionaries I checked, is "giraffes". Normally when the final sound of an English word is F, its plural ends in V sound. But not always. Examples:  knife → knives wife → wives life → lives wolf → wolves leaf → leaves.  But giraffe → giraffes? My best guess would be that the former words are all native English words while "giraffe" is not. I searched "wolf" in Etymology Dictionary and :  from Old English wulf  For "life" :  Old English life (dative lif)  For "wife" :  Middle English wif, wyf, from Old English wif  For "knife" :  late Old English cnif  BUT for "" the entry is quite different:  long-necked ruminant animal of Africa, 1590s, giraffa, from Italian giraffa, from Arabic zarafa, probably from an African language. Earlier Middle English spellings varied wildly, depending on the foreign source, and included jarraf, ziraph, and gerfauntz, some apparently directly from Arabic, the last reflecting some confusion with olifaunt "elephant. The modern form of the English word is attested by c. 1600 and is via French girafe (13c.). Replaced earlier camelopard (from Latin camelopardalis), which was the basis form the name of the "giraffe" constellation Camelopardalis, among those added to the map 1590s by Flemish cartographer Petrus Plancius.  So why is the plural of giraffe different than the other similar words? Why is it not "giraves"?

Many nouns that end in ‑f are made plural by changing the ‑f to ‑v‑ and adding ‑es.  +----------+-----------+ | Singular |   Plural  | +----------+-----------+ |  half    |  halves   | |  leaf    |  leaves   | |  shelf   |  shelves  | +----------+-----------+     But some nouns that end in ‑f are made plural simply by adding ‑s.  +----------+-----------+ | Singular |   Plural  | +----------+-----------+ |  chief   |  chiefs   | |  roof    |  roofs    | |  cliff   |  cliffs   | +----------+-----------+   Some nouns that end in ‑f can be made plural in two ways, either by adding ‑s or ‑ves:   +----------+--------------------+ | Singular |      Plural        | +----------+--------------------+ |  scarf   |  scarfs or scarves | |  hoof    |  hoofs or hooves   | |  dwarf   |  dwarfs or dwarves | |  wharf   |  wharfs or wharves | +----------+--------------------+   Now my question is how to determine whether to use only ‑s or to change the ‑f to ‑v‑ and add ‑es?


For example, I put this:  for i in range (2,n**0.5+1,2):        print(i)   And it doesn't work. I tried putting 1/2 instead but it didn't work  I have python 3.6

Is there a way to step between 0 and 1 by 0.1?   I thought I could do it like the following, but it failed:  for i in range(0, 1, 0.1):     print i   Instead, it says that the step argument cannot be zero, which I did not expect.


The flat FRW metric is given by:  $$ds^2=-c^2dt^2+a(t)^2dr^2$$  If we take $dt=0$ then we get:  $$ds=a(t)\ dr$$  Thus we find that space expands.  If we take $ds=0$ to find the null geodesic followed by a light beam we get:  $$c\ dt=a(t)\ dr$$  Does this imply that cosmological time expands along with space?

The FRW metric is given by: $$ds^2=-dt^2+a^2(t)\ dr^2$$ where $ds$ is an interval of proper length, $dt$ is an interval of cosmic time, $dr$ is an interval of co-moving co-ordinate distance and $a(t)$ is the scale factor (also $c=1$).  If I take $dt=0$ then I find that an interval of proper distance $ds$ is given by: $$ds = a(t)\ dr$$  Thus the proper distance between two nearby co-moving points is proportional to the scale factor - space expands.  If I take $ds=0$ then I obtain the null geodesic equation describing the path of a light ray: $$dt = a(t)\ dr$$  Thus the light travel time between two nearby co-moving points is also proportional to the scale factor.  Does this imply that intervals of cosmic time expand along with intervals of space?  The natural clocks in co-moving co-ordinates are expanding light-clocks.   Maybe in order to derive the constant units of the "atomic" time that we experience, $d\tau$, from expanding cosmic time intervals $dt$, we need to use the conformal time equation: $$d\tau = dt/a(t)$$


Suppose $M$ is a module, $H$ and $K$ submodules.   If $$M/H \cong M/K$$ can I conclude that $H \cong K $ ?   If not, how to construct a counterexample ?

Let $A$ be a commutative ring, $M$ an $A$-module and $N_1, N_2$ two submodules of $M$.  If we have $M/N_1 \cong M/N_2$, does this imply $N_1 \cong N_2$?  This seems so trivial, but I just don't see a proof... Thanks!


Hello and thanks in advance,  I am trying to parse longitude and latitude data from the USGS website then use a for loop to set a pin for each earthquake in a map activity. The format for this value [-102.684,38.47,5] where -102.684, 38.47, and 5 are the longitude, latitude, and depth respectively  This is my for loop in the maps activity:      for (int i = 0; i < 30; i++) {           String finalLongitudeString = longitudeArray[i].substring(1);         double longitudeDouble = Double.parseDouble(finalLongitudeString);           String finalLatitudeString = latitudeArray[i];         double latitudeDouble = Double.parseDouble(finalLatitudeString);          LatLng earthquake = new LatLng(latitudeDouble, longitudeDouble);         mMap.addMarker(new MarkerOptions().position(earthquake).title(locationArray[i]));      }   This is how i am extracting the data from JSON:  coordinatesArray =  coordinates.split(",");              longitude = coordinatesArray[0];             latitude = coordinatesArray[1];             depth = coordinatesArray[2];              longitudeArray[i] = longitude;             latitudeArray[i] = latitude;             depthArray[i] = depth;              locationArray[i] = location;   I am using longitudeArray[i].substring(1) to remove the [ at the beginning of the longitude value.  When I go to the earthquake activity the app crashes with the error "Attempt to invoke virtual method 'java.lang.String java.lang.String.substring(int)' on a null object"  However, when I reopen the app it doesn't crash. Here are screenshots of what the app looks like after opening the app after the crash:    This question was marked as duplicate but I couldn't find the answer I was looking for in the articles marked as duplicate.

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


Last time I restarted my computer, I could not get Ubuntu to load; the screen would either go black, or would hang at the purple screen indefinitely.  I have had some graphics problems in the past, but had put 'nomodeset' after 'quiet splash' in the grub command line, which at least let Ubuntu load.  That doesn't work now, and doesn't work if I remove it.  I looked up some answers, such as this one:  However, when I enter the root in recovery mode in grub, I always get errors when I run those command lines and it won't let me modify the files.  Also, if I run in recovery mode and then choose 'resume normal boot', it will continue.  But instead of getting a usual interface, I get a black screen that asks for my username and password.  I enter these, and it tells me I'm in Ubuntu 12.04, but I'm still on a black screen with texts.  It also informs me that there are updates to install.  When I use the command 'sudo apt-get update', it starts to retrieve the information, but then the screen goes blank after a couple of seconds and I can't do anything anymore.  Any ideas?

After installing Ubuntu 11.10 on a new computer everything worked fine for a few weeks and now suddenly when starting up Ubuntu I get a blank purple screen with no "Ubuntu" splash and the 5 dots but the system does start up.  What has happened to loose the Ubuntu splash screen?  Also, I've checked in the Grub startup and it has quiet splash in the Linux line.   I have an ATI Radeon 5450 graphics card which needed nomodeset to be added to the Grub line when booting for the first time off the install CD but now this line has disappeared from the grub startup.  Can anyone help?


I'm learning Ruby on Rails and was following the tutorial minding my own business, but after creating and trying to merge static pages etc., my app is failing to deploy on heroku and the tests are failing all of a sudden.  Based on the research I've done this is may be due to a merge conflict? In any case, the following lines:   <<<<<<< HEAD content >>>>>>> efcece9f3324a1a06d5f70e2a350b33d0c06d6c7   Have popped up in a bunch of my files (gemfile, gemfile.lock and even a controller) pretty randomly randomly. My tests no longer return green but now display an error "unexpected <<". I'm a noob and totally confused?   Can anyone help me understand if this is indeed a merging conflict, and in any case what caused this and how do I go about fixing it?

I want to resolve merge conflicts in my Git repository. How to do that ?


I seem to have a problem with the zooming levels in QGIS 2.6 Brighton. When I go to zoom in to a vector or raster layer, e.g. for digitizing purposes, the scale seems to be fixed at 1:2,256, I can't zoom in any further than this scale. My previous version of QGIS, 2.2.0 did not have this problem.  Is there a fix for this?

In QGIS, whatever might be the source, I couldn't zoom beyond the scale of 1:2256.   Whether it's a raster or vector, result is the same.   Does anyone know how to fix this ?    On @Chris' advice I've uninstalled "Tile Map Scale Plugin" which fixed the problem (at least for me).


EDIT: The answers found in this previously asked question didn't help:   I'm trying to use particles, which are moving along a path,by following an animated emitter. Basically it's supposed to look like sparks coming out of a firework's propeler.  PROBLEM My particles are forming rings/clusters while moving. They used to look random (as it should be) but it starts to form clusters when you constrain the emitter to "Follow Path".   Only way to not get clustering is by manually building the animation (not an option on the long run)

I have tried using the Subframes option. It hasn't done a thing.  So I have an object which gives off 3 particles into the air.  I have an Icosphere object on a different layer with a particle instance modifier on it.  That allows me to add a particle system to the Icosphere to create some awesome particle trails    But the particle system that is attached to the Icosphere creates clumps of particles on each frame.  I am wanting a nice, smooth stream of particles being emitted from the main particles.  Is there a way to fix this, or does the Subframes option not work with the Particle Instance modifier.  Here is my .blend file:  I am using Blender 2.72


I want to create a Python's code snippet which includes single quotes using minted package. I've put it altogether like this:  \begin{minted}[     autogobble,     frame=lines,     framesep=4mm,     fontfamily=fdm,     fontsize=\footnotesize,     python3=true,     style=vs]{python} >>> D.mro() [<class '__main__.D'>, <class '__main__.B'>, <class '__main__.C'>, <class '__main__.A'>, <class 'object'>] \end{minted}   But the output does look a bit odd:    However changing single quotes to double quotes does not seem to work either. Does anyone know how to fix such behaviour? Thanks

I'm using minted to highlight code in Python. In some cases I want to mix code with output that the user will see. This gives me the red syntax error boxes, for example like so:    And sometimes it gives me no error but I would like to turn off the highlighting (second line):    So what I would like to know if it's possible to turn off the highlighting for a few lines but at the same time keeping the options such as the line numbering and background.  MWE:  \documentclass{article}  \usepackage{minted} \definecolor{bg}{rgb}{0.95,0.95,0.95} \newminted{python3}{bgcolor=bg, linenos=true, tabsize=4}  \begin{document}  I want lines 2 and 4 not to be highlighted but still keep the background and line numbering.  \begin{python3code} >>> type(3.14) <class 'float'> >>> print(name) NameError: name 'name' is not defined \end{python3code}  \end{document}   Edit: To clarify: There are lines that I want highlighted that start with >>> and there are lines I want highlighted which don't start with >>>. There are also lines that I don't want highlighting for. So the default should be that it highlights the line but that I can add an exception to some lines.


Executing the Test class gives a StackOverFlow error :(   Parent class :   package Pack;  public class Alpha {   protected void sayHi() {     System.out.println("Hi...from Alpha");   } }   Child class :   import Pack.Alpha;  public class AlphaSub extends Alpha {   AlphaSub sb=new AlphaSub() ;    void hi() {     sb.sayHi() ;    } }   Test class :   public class test { public static void main(String[] args) {      AlphaSub ob=new AlphaSub() ;     ob.hi() ; }   }

What is a StackOverflowError, what causes it, and how should I deal with them?


a friend is trying to install Firefox on an Ubuntu loaded in Crouton in a Chromebook. Technically, all they have to do is enter the sudo command to install firefox, but apparently a user agreement window pops up after installation and doesn't allow them to continue. There is an "okay" at the end but clicking on it doesn't do anything. As they cannot screenshot, this is their description:  There's a fuchsia background. At the top in grey it says "Package configuration" then in the middle there's a large grey box. At the very top there's a piece of scarlet text that reads "Configuring ttf-mscorefonts-installer". It doesn't move, even when you scroll down. The text inside is black and reads "TrueType core fonts for the Web EULA" at the top and then "END-USER LICENSE AGREEMENT FOR MICROSOFT SOFTWARE", then the rest is the agreement. When you scroll down to the very bottom, it reads "Reference:" then gives a link. At the bottom there's a piece of stationery text that reads, " < Ok >", but it's unclickable.  Is there a way to bypass this? We downloaded twice but came across the same problem so it doesn't seem like it's a bug in the installer itself.  Also this is our first time trying Linux so do be gentle :P

After a recent update, ttf-mscorefonts-installer prompted me to accept its license agreement.     ┌─────────────────┤ Configuring ttf-mscorefonts-installer ├─────────────────┐  │                                                                           │   │ TrueType core fonts for the Web EULA                                          │                                                                               │ END-USER LICENSE AGREEMENT FOR MICROSOFT SOFTWARE                             │                                                                               │ IMPORTANT-READ CAREFULLY: This Microsoft End-User License Agreement           │ ("EULA") is a legal agreement between you (either an individual or a          │ single entity) and Microsoft Corporation for the Microsoft software           │ accompanying this EULA, which includes computer software and may include      │ associated media, printed materials, and "on-line" or electronic              │ documentation ("SOFTWARE PRODUCT" or "SOFTWARE"). By exercising your          │ rights to make and use copies of the SOFTWARE PRODUCT, you agree to be        │ bound by the terms of this EULA. If you do not agree to the terms of          │ this EULA, you may not use the SOFTWARE PRODUCT.                              │                                                                               │                                  <Ok>                                         │                                                                           │   └───────────────────────────────────────────────────────────────────────────┘    Screenshot:   For some reason my terminal will not allow me to accept, or for some reason I am pressing the wrong hotkey...  I've tried every letter on the keyboard and Enter among others...  I'm sure there is a very simple and obvious solution to this.  I've also just tried to remove the package completely however the terminal states that due to the package not being correctly installed, I should reinstall the package before removing it.  Very frustrating!  Essentially, because I cannot successfully install this package, I can't really ever upgrade my system because I always have to end up terminating the terminal with the license agreement (thus the upgrade fails).


I have this GWT code that opens a new browser window to show a text file.       Window.open("data:text/plain;base64," + Base64.byteArrayToBase64(textBytes), "_blank", "");   My questions are:   How long is the maximum URL part that a browser can handle? And what is the maximum bytes that this code will be able to handle properly?

What is the maximum length of a URL in different browsers? Does it differ among browsers? Is a maximum URL length part of the HTTP specification?


How do I delete all music from an iPhone 5? It got loaded from my computer without me checking the box. I tried to follow the directions from one search result with no success.

How do I delete all the music on my iPhone.  I tried doing it through iTunes but it says my collection is not managed by iTunes and I don't want to erase and sync because all my apps are nicely backed up and sorted with iTunes.  I have only seen a way of deleting song by song on the phone.


$$\begin{bmatrix} 1235 &2344 &1234 &1990\\ 2124 & 4123& 1990& 3026 \\ 1230 &1234 &9095 &1230\\ 1262 &2312& 2324 &3907  \end{bmatrix}$$  Clearly, its determinant is not zero and, hence, the matrix is invertible.   Is there a more elegant way to do this?  Is there a pattern among these entries?


I got a problem, when I tried to apt-get update it gives me these error. I don't know why, but I got my network properly work in other way. Please help fix it. I tried many methods of fixing it according to what I've searched but it never worked.   root@isaac-desktop:~# dpkg --configure -a root@isaac-desktop:~# apt-get update Get:1 http://ph.archive.ubuntu.com/ubuntu xenial InRelease [392 B] Get:2 http://ph.archive.ubuntu.com/ubuntu xenial-updates InRelease [392 B] Get:3 http://ph.archive.ubuntu.com/ubuntu xenial-backports InRelease [392 B] Get:4 http://security.ubuntu.com/ubuntu xenial-security InRelease [392 B] Err:1 http://ph.archive.ubuntu.com/ubuntu xenial InRelease   Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) Err:2 http://ph.archive.ubuntu.com/ubuntu xenial-updates InRelease   Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) Err:3 http://ph.archive.ubuntu.com/ubuntu xenial-backports InRelease   Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) Err:4 http://security.ubuntu.com/ubuntu xenial-security InRelease   Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) Fetched 2,059 B in 1s (1,863 B/s) Reading package lists... Done E: Failed to fetch http://ph.archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) E: Failed to fetch http://ph.archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) E: Failed to fetch http://ph.archive.ubuntu.com/ubuntu/dists/xenial-backports/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) E: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) E: Some index files failed to download. They have been ignored, or old ones used instead.

So I am on my college network which requires me to sign in to the browser before I start using the internet. I do so succesfully but on a clean install of Ubuntu, when I try to do sudo apt update, I get the following output:  $ sudo apt update Get:1 http://in.archive.ubuntu.com/ubuntu xenial InRelease [2,847 B] Err:1 http://in.archive.ubuntu.com/ubuntu xenial InRelease                     Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) Get:2 http://security.ubuntu.com/ubuntu xenial-security InRelease [2,854 B]     Err:2 http://security.ubuntu.com/ubuntu xenial-security InRelease              ... Get:3 http://in.archive.ubuntu.com/ubuntu xenial-updates InRelease [2,855 B]    Err:3 http://in.archive.ubuntu.com/ubuntu xenial-updates InRelease ... Get:4 http://in.archive.ubuntu.com/ubuntu xenial-backports InRelease [2,857 B] Err:4 http://in.archive.ubuntu.com/ubuntu xenial-backports InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) Fetched 11.4 kB in 0s (18.3 kB/s) Reading package lists... Done E: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/xenial/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?) ... E: Some index files failed to download. They have been ignored, or old ones used instead.   But when I do wget http://in.archive.ubuntu.com/ubuntu/dists/xenial/InRelease, I get this output success:  2017-04-01 05:34:57  http://in.archive.ubuntu.com/ubuntu/dists/xenial/InRelease Resolving in.archive.ubuntu.com (in.archive.ubuntu.com)... 91.189.88.162, 91.189.88.149, 91.189.88.152, ... Connecting to in.archive.ubuntu.com (in.archive.ubuntu.com)|91.189.88.162|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 246846 (241K) Saving to: ‘InRelease.3’  InRelease.3         100%[===================>] 241.06K   110KB/s    in 2.2s      2017-04-01 05:35:00 (110 KB/s) - ‘InRelease.3’ saved [246846/246846]   Clearly I have internet access from my browser and on wget but when I do sudo apt (or apt-get) update I get this error.  PS: This question is not similar to other threads as their solutions do not seem to work on mine        As I have found out, this problem is happening only to me, not others on the college network. Despite setting up the network according to instructions, this still happens. Any more help would be appreciated  EDIT: So as it turns out, 50% of us in the college are facing this issue, while 50% aren't despite having no issues with the hardware and sudo apt update before the last week. Thanks to @David Foerster for helping me throughout all this time.  As it stands, the issue has been raised to our college's networking department :)


I want to ask the following problem: Let $a_n$ be a sequence of positive numbers such that $\sum a^2_n$ converges. For $b_n = \dfrac{a_1 + a_2 + \cdots + a_n }{n}$, does $\sum b^2_n$ converges? At first, I tried to find a counterexample by computing the case where $a_n = 1/n^{1/2 + \epsilon} $, but sadly that made $\sum b^2_n$ convergent. Also, I tried to prove that the sequence converges by using C-S inequality, limit comparison test, etc... but all ideas failed. Please give me your advice or ideas for this problem. Thank you in advance.

If the sequence $b_n$ is defined as $$b_n =\frac {a_1+a_2+\dots+a_n}n.$$  then  I found out that $b_n$ is always divergent and now that I have to prove the given statement I tried using comparison test. The problem is that I am getting that this is true if the sequence $a_n$ in monotonically increasing. But the hypothesis only says that it is a non negative sequence.


I just downloaded the new Android app (version 1.0.2) and every question and answer consistently just shows up as a black box (excepting where there's a link) on my Sprint LG Mach. I see  complaining about this same issue in early betas--but that was four months ago. Has any progress been made on determining the cause of this bug or resolving it? Is the app open source so us community members can help solve bugs? This app looks absolutely fantastic, but completely useless if you can't read the answers because you have black text on a black background

On my Samsung Galaxy S2 all answers appear as black box. Here is an example:    I am running Android 4.0.3


Let $S$ be a multiplicative system. Then the localization of $R$ is defined by an equivalence relation on $R \times S$. The relation is $(a,b) \sim (c,d)$ if there is an $s \in S$ such $s(ad-bc)=0$.  Regarding this, I can't show that transitivity works. Could anyone show me how to prove that $(a,b) \sim (c,d)$ and $(c,d) \sim (e,f)$ then $(a,b) \sim (e,f)$?

Let $A$ be a ring (commutative with $1$), let $S$ be a multiplicatively closed subset of $A$, i.e $S$ is contained in $A$ , $1\in S$ and $a,b\in S$ implies $ab\in S$, for every $a,b\in A$. Consider the following relation defined in $A\times S$: $$(a,s)\equiv(b,t) \iff \exists u\in S:u(at-bs)=0$$ I proved this relation to be reflexive and symmetric, but i have difficulties in proving its transitivity. Can someone suggest me a trick?


Diamonds are the best material in the Minecraft. There are many ways to mine diamonds, but which one is the best and most efficient one? If someone can tell me the time it takes, the tools used, the sequence etc, it would help me a lot.

When I'm not exploring fresh caves or lands in minecraft, I'm busy trying to find deposits of diamond, gold and iron deep in the earth. So far I've just been digging around just above bedrock on a whim to look for these rare minerals but I've started thinking that I should be taking a more controlled, efficient approach to mining.  What is the optimal mining strategy that yields the most rare minerals while minimizing blocks removed and time spent digging and traveling?  Edit: The existing answers are great for mining, but no one has addressed travel time to and from the mine which is usually ~60 blocks downward and incredibly tedious. Solutions?


I want to solve the proof by using mathematical induction. I'm just not exactly sure of how I should start, like how should I do the base case?

How can I prove that a polynomial with degree $n$ is continuous everywhere in $\mathbb{R}$ using definitions?  With induction. I can show that this polynomial is continuous at $x_0$ but I do not know how to prove that it is continuous everywhere in $\mathbb{R}$. I know that a function is continuous on an interval if it is continuous at every point on the interval but this implies that I need to show for every $x_0\in\mathbb{R}$, the polynomial is continuous.


In the definition of localization of a ring $R$ where $S$ the multiplicative subset, we say $(a,s) \sim (b,s') \iff \exists t \in S$ such that $t(s'a-sb)=0$.  Why do we require such a $t\in S$?  What if we just say $(a,s) \sim (b,s') \iff s'a-sb=0$?

Let $A$ be a ring and $S$ a multiplicative closed set. Then the localization of $A$ with respect to $S$ is defined as the set $S^{-1}A$ consisting of equivalence classes of pairs $(a, s)$ where to such pairs $(a,s), (b,t)$ are said to be equivalent if there exists some $u$ in $S$ such that  $$u(at-bs)=0$$ Now, in the  about the localization of a ring, it says that the existence of that $u\in S$ is crucial in order to guarantee the transitive property of the equivalence relation.   I've seen the proof that the equivalence relation defined above is indeed an equivalence relation, but I fail to see how crucial the existence of $u$ is. For example, why doesn't it work if we simply say that two pairs $(a,s),(b,t)$ are equivalent iff $at - bs = 0$? I tried to come up with a counterexample for such case, but failed in the attempt.


I have my Mac OS X Yosemite system configured in spanish, but I have an app with a horrible spanish translation, and I would like to run it (and just this app) in english. How could I do that?

I'm a developer, and my primary language is French, so I use Mac OS X in French. However, I need on a regular basis to open an application in English to do support.  Right now I'm going to the International System Preferences and I put English above in the languages list, then I open the app I need to run in English. When I'm done, I switch it back to French.  This is an annoying process. Is there something else I can use, like a command-line program, to launch an application in a specific language?


I learn Lotka-Volterra model in computing mathematics textbook and solve it by different numerical methods.   $$ \frac{1}{x}\frac{dx}{dt} = a - by$$ $$ \frac{1}{y}\frac{dy}{dt} = cx - d$$  where, $a,b,c,d \in \mathbb{R}$  But I am trying to solve it by myself, and I can't work it out.  Particularly, I don't know how to deal with $$ \log x = \int_{0}^{t} (a - by) dt $$  where $y$ is also a function of $t$.

I am looking for exact or perturbative solution realistic lotka-volterra (the one with logistic term in one of the equations) equations in population dynamics.  Any reference where they have done it will be useful.


So this lady hit me up on Instagram and asked if I’d maybe be interested in being her sugar baby. We talked a bit but she wants my bank login and password. I asked for picture proof and she sent a picture but I still don’t know if I should believe it. I understand that “she” can take out my money but I only have $15 so there’s not that much of a risk. If I give her my info, what’s the worst that can happen?

Someone is offering to pay me in a sort of sugar daddy/sugar baby arrangement. They want to make online deposits to me, and they're asking me for my online banking username and password. Is that information alone enough for them to be able to take my money out of my account, or am I safe?


Minecraft keeps closing a whenever I try to play on multiplayer and its keeps saying that I have a file open. Here is the crash report:  Completely ignored arguments: [--nativeLauncherVersion, 301] [17:43:10]  [Client thread/INFO]: Setting user: Legend_2007 [17:43:10]  [Client thread/INFO]: (Session ID is <censored>) [17:43:13]  [Client thread/INFO]: LWJGL Version: 2.9.4 [17:43:14]  [Client thread/INFO]: Reloading ResourceManager: Default [17:43:16] [Sound Library Loader/INFO]: Starting up SoundSystem... [17:43:16] [Thread-5/INFO]: Initializing LWJGL OpenAL [17:43:16] [Thread-5/INFO]: (The LWJGL binding of OpenAL.  For more information, see http://www.lwjgl.org) [17:43:17] [Thread-5/INFO]: OpenAL initialized. [17:43:17] [Sound Library Loader/INFO]: Sound engine started [17:43:25]  [Client thread/INFO]: Created: 1024x512 textures-atlas [17:43:35]  [Client thread/INFO]: Connecting to play.cubecraft.net, 25565 [17:43:38]  [Client thread/INFO]: [CHAT]                                        #  # A fatal error has been detected by the Java Runtime Environment:  #  #  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x00007ffd2ee92177, pid=3040, tid=5852  #  # JRE version: Java(TM) SE Runtime Environment (8.0_25-b18) (build 1.8.0_25-b18)  # Java VM: Java HotSpot(TM) 64-Bit Server VM (25.25-b02 mixed mode windows-amd64 compressed oops)  # Problematic frame:  # C  [ig75icd64.dll+0x12177]  #  # Failed to write core dump. Minidumps are not enabled by default on client versions of Windows  #  # An error report file with more information is saved as:  # (i got rid of this part because it showed private info)  #  # If you would like to submit a bug report, please visit:  #   http://bugreport.sun.com/bugreport/crash.jsp  # The crash happened outside the Java Virtual Machine in native code.  # See problematic frame for where to report the bug.  # AL lib: (EE) alc_cleanup: 1 device not closed Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

When I try to launch Minecraft 1.7.4 or newer, the game crashes on startup, and the game output screen says this:  #  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=*, pid=*, tid=* # # JRE version: Java™ SE Runtime Environment (7.0_51-b13) (build 1.7.0_51-b13) # Java VM: Java HotSpot™ Client VM (* mixed mode, sharing windows-* ) # Problematic frame: # C  [ig4dev32.dll+0x3e88] OR # C  [ig4dev64.dll+0x55ec] OR # C  [ig4icd32.dll+0x104a77] OR  # C  [ig4icd64.dll+0x84930a]   This happens with both Java 7 and 8.  What causes this error, and what can I do to fix the issue?


I have looked throughout this site to find a method to calculate the overlap area of multiple polygons within a single shapefile but haven't found one that works for my case. I've tried the intersect tool but that doesn't seem to accomplish my task as it requires multiple input shapefiles.     Above I have included a image of my shapefile and the polygons. Each polygon represents an animal's territory and has several attributes assigned to it (age, sex, etc). In this example, there are some polygons (animal territories) that don't overlap and others that overlap multiple polygons. What I would like to do is to calculate the total overlap area (dark purple) within the shapefile. Eventually I would like to know the identities of all the animals that overlap each other. In the entire shapefile I have 300+ territories and multiple years of data so I need an approach that would be somewhat efficient.

I have a shapefile composed of fire scar polygons identifiable as unique categories based on year of fire.   I am interested in measuring the area of overlapping fire scars from different years.   Is it possible to perform an intersect of categories within a shapefiles or will I have to split each category into a separate shapefile first?


If a mapping $f:X \rightarrow S^4$ is not surjective, then it must be null-homotopic.  Why is this? I understand that if the map is surjective then it is not homotopic to the constant map because $S^4$ is not contractible. Can somebody explain this to me? Are there similiar situations for $S^2, S^3$ or $S^n$ for that matter? Thanks!

I am attempting to prove the following:  If $g:X \to S^n$, $n \ge 1$, is a continuous map whose image $g(X)$ is a proper subset of $S^n$, then $g$ is null-homotopic.  Just before this I proved that if $Y$ is contractible, then every continuous map $f:X \to Y$ is null-homotopic.  Therefore I'd like to show that any proper subset of $S^n$ is contractible.  What is the best way to do this?  I wanted to use that $S^n$ is an $n$-manifold to associate it with an open set in $\mathbb{R}^n$, which, if it is convex, is contractible.  However, I don't think this works, and it seems like overkill anyway.  What is the best way to show that a proper subset of $S^n$ is contractible?  Thanks.


In the circuitikz package a specific element called sinusoidal voltage source is available (it is presented in the , page 18, first image).  The code (or part of it) is in the tex/pgfcircbipoles.tex inside the package. I tried to use it in a new document with tikz, but it doesn't work.  Is it possible to create and use this shape in tikz (that is: inside a \begin{tikzpicture}...\end{tikzpicture} block)? How?

Some time ago, I asked about . wh1t3 wrote: "However, as far as I know there is nothing the circuitikz package does that the TikZ circuit library can't."  So if it is true that the tikz library is more powerful, how do I get all the symbols described in the  using the TikZ circuit library?  Especially I am missing the symbols for ammeters and voltmeters.


I try to open a hyperlink from a feature in QGIS using the Windows options. I managed to make a hyperlink working, by copying in the edit action tab, the Adobe Acrobat path, the field name and the destination field, but it shows error messages. If I close the messages, I can visualise the document.

I want an attribute in a shapefile named "Link" to add.   The works are all fine but then I would like to add a link in my directory.   This link accesses a PDF. Now, this PDF is not shown.   Is there any other solution or there is nothing to be done?


We got this exercise sheet and I don't really know how to solve some of the problems, thanks for any help or/and advice!  Problem a) $A,B$ and $C$ are sets. Prove that:   $A \cap (B \cup C) = (A \cap B) \cup (A \cap C)$   Problem b) Proof that for sets $A, B\subset X$ counts   $X \setminus (A \cap B) = (X \setminus A) \cup (X \setminus B)$   If someone could explain how I'm supposed to write down the proof I will probably be able to solve the rest on my own, all I need is a little start help.  Thanks a lot!

I have to resit a calculus exam and for some reason set proofs were never my best friend...  Anyway, on a practice exam I encountered the following proof:  $$A\cap(B\cup C) = (A\cap B)\cup(A\cap C)$$  When I draw a Venn-diagram it seems quite obvious but I couldn't manage to write the proof down properly.  If someone could help me, that'd be great!


I search on  but I not found an answer.  I want make a output on my keyboard to charge an usb device (ie: mp3 reader or smartphone).  - In first time I want to know if is there a mechanical computer keyboard generating current with keystrokes? (with current generation in keyboard)  - In second time I want to know how is possible to make that?    EDIT #1 :  The  on it in December 30, 2014.  This article describes a keyboard, which can among other features, harvest energy. But the abstract does not reveal the harvesting method and it is not clear if the harvested energy is sufficient to fulfil its own tasks.    EDIT #2 :      This paper presents a hybrid energy harvester which combines piezoelectric (PZT) and electromagnetic (EM) transduction mechanisms to scavenge vibration energy from a keyboard. The system comprises of improvements to the dome structure presented in previous studies, in which only PZT transduction mechanism was used to harvest 16.95 μW of experimentally verified power. An in-house modeling and simulation tool is first introduced in this work to evaluate the integration of EM transduction into the PZT system. The tool combines analytical mechanical equations and FEM results for magnetic fields for the optimization of the electromagnetically generated power. Two designs of different cost are then compared. It is concluded that the design utilizing the frequency-up-conversion technique at an incrementally higher cost is superior due to significantly higher contribution to the generated power compared to the alternative implementation without frequency-up-conversion. Modeling and simulations show an additional 2.81 μW power can be generated through EM integration to the previous PZT based keyboard energy harvester system.   According to :      only 4077 years needed for 1 kWh..    I think (fix me if I mistake) USB device need 500 mA to charge 5V.   - I ask me how many times is needed to charge an usb device?    EDIT : I feel that this question goes beyond me

Recently I'm working on a project aiming to convert the vibration of sound waves into electricity to charge batteries using a piezoelectric material (MFC type). I was trying to use the human voice as an input, but theoretically it was not enough, so do you have any ideas about some places that I can apply my project on it (that must be noisy or can give me vibrations)?  Moreover, has the MFC material been used before in this application? If I used many pieces of it in parallel would that help?


I am getting out of memory error,how to resolve?what is mean by Permgen space area? What is causing it?  What is solution for it?  java.lang.OutOfMemoryError: PermGen space     java.lang.ClassLoader.defineClass1(Native Method)     java.lang.ClassLoader.defineClassCond(Unknown Source)     java.lang.ClassLoader.defineClass(Unknown Source)     java.security.SecureClassLoader.defineClass(Unknown Source)     org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1814)     org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:872)     org.jboss.web.tomcat.service.WebAppClassLoader.findClass(WebAppClassLoader.java:75)     org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1325)     org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)     com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:289)     java.sql.DriverManager.getConnection(Unknown Source)     java.sql.DriverManager.getConnection(Unknown Source)

Recently I ran into this error in my web application:     java.lang.OutOfMemoryError: PermGen space   It's a typical Hibernate/JPA + IceFaces/JSF application running on Tomcat 6 and JDK 1.6. Apparently this can occur after redeploying an application a few times.  What causes it and what can be done to avoid it? How do I fix the problem?


So far every time I have uninstalled a new version of Ubuntu I have done a clean install of the system, and after that I have installed all programs all over again, but now I am thinking as I have a quite many programs installed currently on my Ubuntu version:  Is it "safe" to update my version of Ubuntu to the latest 13.10 or it is the best to use the 'old school' way and to install a fresh installation and then try to install and transfer all data and programs that I had in previous version? What is better option?

Is it better to install Ubuntu completely new or is the upgrade process just as good? In other words, will my computer run just as problem-free and efficiently when I upgrade as opposed to a fresh install?


Guys recently i installed ubuntu in my dell inspiron and after installing it my wifi is not working. Any help would be appreciated.  And here are the results as asked.  lspci -vnn | grep Network 12:00.0 Network controller [0280]: Broadcom Corporation BCM4313 802.11bgn Wireless Network Adapter [14e4:4727] (rev 01)

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


See title.  I am trying to figure out if it's possible for someone to find the proper information without an OS being on the machine in question. Usually there are a number of programs you could use to find whether your computer can use either/or, and in the case of Windows it tells you if your machine is 64-bit compatible.  However, I do not have an OS installed on this machine, and from my knowledge you cannot run an executable without an OS. Do I use the BIOS? Determine it by RAM? 'How do?'  Thanks in advance, and pardon my computer illiteracy.

My Windows XP installation has become unusable for some unknown reason. Since Microsoft is going to end support in a few days anyway, I decided to install Linux Mint.  For optimal hardware utilization, I want to use a 64-bit system if possible. However, since XP isn't working it's not possible to .  Therefore, I want to use the BIOS to find it out.  What information in the BIOS should I use to determine whether or not my I can install a 64-bit operating system?


I was solving a problem Called Modular inverting on  the problem states that: if we have 3 * d ≡ 1 mod 13 how can we get d using  I solved it using basic math but I found a solution that I couldn't understand ''' Looking again at Fermat's little theorem... if p is prime, for every integer a:         pow(a, p) = a mod p and, if p is prime and a is an integer coprime with p:         pow(a, p-1) = 1 mod p We can do some magic like this: Note: i'll use math notation, so a^b means pow(a,b)         a^(p-1) = 1 (mod p)         a^(p-1) * a^-1 = a^-1 (mod p)         a^(p-2) * a * a^-1 = a^-1 (mod p)         a^(p-2) * 1 = a^-1 (mod p) So finally we have:         a^(p-2) = a^-1 (mod p) So, doing a^(p-2) and then (mod p) we can achieve our result '''  that problem was with the last part when we have $$a^{p-2} ≡ a^{-1}\pmod  p \tag{1}$$ all I know that $$a ≡ b\pmod n $$ means: $$a = kn + b$$ which means: $$(a\bmod  n) = b$$ applying this to the first equation: $$a^{p-2}\bmod  p = a^{-1}$$ I am new to the  so I am sorry if it's a dumb question but can someone explain to me what I am missing here?

Why is $a^{-1}$ mod $p$ equal to $a^{p-2}$ mod $p$ in modular arithmetic?


Hi I've recently become interested in developing applications for iOS. I've taken classes in Objective-C before, and we've always used Xcode to build and run our programs. I am a Windows user at home, and I'm not interested in buying a Macintosh. Is there any way to install Xcode on a Windows 8 PC? Any help is appreciated, thanks. :D

Is there any way to tinker with the iPhone SDK on a Windows machine? Are there plans for an iPhone SDK version for Windows?  The only other way I can think of doing this is to run a Mac VM image on a VMWare server running on Windows, although I'm not too sure how legal this is.


I two .py files: file_1.py file_2.py file_1.py contains code that will open an raster and split it into sections. Similar to creating a grid and clipping to each grid within QGIS. I have a variable x set as my file that I want to use "raster.tif". I would like import this variable into file_2.py. I found this  by @Ashwini Chaudhary (import file_1 then file_1.x). The problem I am facing is when I run file_2.py, file_1 is executing first. I simply want to access the variable and not execute the file. Is that possible to do?

Given the following code, what does the if __name__ == "__main__": do?  # Threading example import time, thread  def myfunction(string, sleeptime, lock, *args):     while True:         lock.acquire()         time.sleep(sleeptime)         lock.release()         time.sleep(sleeptime)  if __name__ == "__main__":     lock = thread.allocate_lock()     thread.start_new_thread(myfunction, ("Thread #: 1", 2, lock))     thread.start_new_thread(myfunction, ("Thread #: 2", 2, lock))


I read this short story in an anthology borrowed from the local public library around 1980.  (The book itself may have been older.)  The story begins with the global sensation of a massive object entering our solar system from interstellar space.  As it approaches the Sun it maneuvers which indicates it is an actual alien visitor, not just a random rogue planet.  (It is of planetary scale.)  I believe that when it is viewed through a telescope it has massive wings that it uses to steer using the Sun's light.  The alien brakes into a solar orbit and matches its orbit to Mercury.  Humanity watches, wondering what it is doing, and then the crust of Mercury starts to crack.  The entire crust is dislodged, and a smaller version of the alien spreads its wings.  The alien begins to spiral out to Venus' orbit, and people on Earth start freaking out.  Massive projects are started to drill through the Earth's crust and set off hydrogen bombs in the hope of killing the hatchling before it destroys the Earth.  Meanwhile Venus hatches, and the (now 3) aliens start towards Earth.  The story ends with the narrator saying something like "this morning the Earth began to knock."

I read a short story as a child that revolved around the people of earth observing a distant object in space approaching.  Over time as the distant speck got closer it was observed to be a giant bird and the earth itself began to tremble and quake as if our planet was the bird's egg.  Does anyone know the name of this story?


I feel like I have a good grasp of what the __name__ environment variable is in python in general. However, when I print out the __name__ variable from an __init__.py it prints out the name of the directory it's in (aka the package name). How does __name__ get defined in the init file?    Also, does each python file have its own local __name__ variable? because it's constantly changing between files... (maybe I don't understand __name__ as well as I thought I did)    EDIT: I really don't think this question is the same as the __name__ equals __main__ question. I understand what __name__ equals in most python files. I'm just still confused on what it's value is in the __init__ files.


This is my first freelance work. Can somebody tell me that on what basis should I fix my rates for this home page design coz I am not able to decide. The client wanted in green and red combination. I have designed the whole UI in photoshop. Logo is also designed by me. Please give reviews and feedback. Should i fix my rates on time taken, or on the quantity of work or on my experience....???

I was hoping I would find some people in the industry that could help me decide what's the best price to charge to design (in this case) business cards.  What are standard prices for professional designers?  From a firm point of view? From a freelancer?  I don't want to overcharge clients but I don't want to ruin the industry by underselling my services.


I created a PHP file, which give back an image location. for example:  Its give back this:   Its okey. But I need to read the example.php and GET the image location (so the https:// www dot example dot com/image1.png) and display on my site with Javascript.  var wheelImageName   = "url/image1.png";  function begin()    {  surface = document.getElementById(canvasId);   if (surface.getContext)  {     wheel = new Image();     wheel.onload = initialDraw;          wheel.src = wheelImageName; } }   This is the code now, My question is, how to modify this, to read the target image url from the example.php.  Thanks!

I need to do an  request in JavaScript. What's the best way to do that?  I need to do this in a Mac OS X dashcode widget.


This is the outcome of my code so far:    What I actually want to achieve is to move the two button to the center horizontally. But at the moment they are aligned to the left.  This is the result I want to achieve:    I have tried alignItems but it has no effect. I don't want to use any margin because the container size may vary.  Here is my code:    const H = "540px"; const W = "720px";  const ContentView = ({ width, height }) => (
Hello! Alt View!
 );  const ControlView = ({ width, height, onReveal, onCopy }) => {   const container = {     width,     height,     position: "relative"   };   const controlsContainer = {     width,     height,     position: "absolute",     left: 0,     top: 0,     border: "5px solid green",     display: "flex"   };   return (

             <button               style={{                 width: "400px",                 height: "60px",                 minWidth: "200px",                 display: "block"               }}               onClick={onReveal}             >               Reveal             </button>

             <button               style={{ width: "400px", height: "60px", minWidth: "200px" }}               onClick={onCopy}             >               Copy Meta             </button>

   ); };  class App extends React.Component {   constructor(props) {     super(props);     this.state = { playing: false };   }    _onReveal() {     this.setState({ playing: true });   }    _onCopy() {     window.alert("Meta data copied");   }    renderAltView() {     return <AltView />;   }   render() {     const { width, height } = this.props;     if (!this.state.playing) {       return (

Controls
           <ControlView             width={width}             height={height}             onReveal={() => this._onReveal()}             onCopy={() => this._onCopy()}           />
       );     }     return (
         <ContentView />
     );   } } ReactDOM.render(<App width={W} height={H} />, document.getElementById("app"));

     Unfortunately I cannot get it to work in SO code snippet. A working version is here at codepen   What flex directive I can use to position the buttons as I want?

I want to center a div vertically with CSS. I don't want tables or JavaScript, but only pure CSS. I found some solutions, but all of them are missing Internet Explorer 6 support.
Div to be aligned vertically
   How can I center a div vertically in all major browsers, including Internet Explorer 6?


I have an HTML link that links to an external site. I want to be able to add a dialog message when the user taps on the link and no internet connection is available. I want to be able to do this using HTML and javascript.  See this example of what I am trying to achieve. Thanks.

How to detect the Internet connection is offline in JavaScript?


Could you please help in understanding the output of below java code where this(0) of Superclass is called when object is created for Subclass.  In this code though there is no mention in the code to explicitly print 20, why the first value is printed as 20?  class Superclass {     Superclass() {         this(0);         System.out.println("1");     }      Superclass(int x) {         System.out.println("2" + x);     } }  class Subclass extends Superclass {     Subclass(int x) {         System.out.println("3" + x);     }      Subclass(int x, int y) {         System.out.println("4" + x + y);     } }  public class practiceTest {     public static void main(String[] args) {         Subclass s = new Subclass(10, 20);     } }

I have a question about default constructors and inheritance in Java.   Generally, if you write a class and do not include any constructor, Java provides automatically for you a default constructor (one without parameters), which initializes all instance variables of the class (if there are any) with some default values (0, null, or false). If you write a constructor, however, with some parameters, and you don't write  any default constructor, then Java does not provide a default constructor.  My question is: what is the case with classes, which inherit from other classes - if I write a constructor with some parameters in them, but don't include a default constructor, do they inherit the default constructor of the super class?


I want to find a ring $R$ which satisfies     $R$ is not Noether and $\operatorname{Spec}R$ is Hausdorff.   I found the latter condition is equivalent to R's Krull dimension is $0$. So, I just need to find an example of Non-noether and $0$ dimensional ring. Are there any good examples? Thank you advance.

Proposition: Let $A$ be a non-zero ring that is not a field. Suppose $A$ is zero dimensional. Then it is Noetherian.   Proof: Let $p$ be a prime ideal of $A$. If $p$ is not maximal, then $p \subsetneq m$ for a maximal ideal $m$. Hence $dim A \ge 1$, contradiction. Hence every prime ideal is maximal. Consequently, every increasing (or decreasing) chain of prime ideals will be trivial in the sense that it will have length $0$. Hence the ring is Noetherian (and Artinian).  Is there a problem with the above proof?


I opened a Facebook account for my husband using the same email as mine for my Facebook account. I have since purchased a new computer and when I enter my email address and password it says the password is wrong. When I use my husband's password it brings me to his Facebook page.    How do I access my Facebook page on my new computer if I can't use our email and my password?

My husband wanted me to set up a Facebook account for him and I accidentally used our shared email address, which is set against my own account.  Since then, neither of us has been able to log in, so I can't alter any settings.  Can anyone advise how to resolve this please?


I'm an ex Pascal guy, currently learning C#. My question is the following:  Is the code below faster than making a switch?  int a = 5;  if (a == 1) {     .... } else if(a == 2) {     .... } else if(a == 3) {     .... } else if(a == 4) {     .... } else     ....   And the switch:  int a = 5;  switch(a) {     case 1:         ...         break;      case 2:         ...         break;      case 3:         ...         break;      case 4:         ...         break;      default:         ...         break;   }   Which one is faster?  I'm asking, because my program has a similar structure (many, many "else if" statements). Should I turn them into switches?

What is the benefit/downside to using a switch statement vs. an if/else in C#.  I can't imagine there being that big of a difference, other than maybe the look of your code. Is there any reason why the resulting IL or associated runtime performance would be radically different? Related:


Let G be a group and let p be a prime. Let g and h be elements of G with order p.  I am wondering how I can use group theory to find the possible orders of the intersection between $\def\subgroup#1{\langle#1\rangle}\subgroup g$ and $\subgroup h$ and also to prove that the number of elements of order $p$ in $G$ is a multiple of $p-1$.  I've been looking for the path for ages and got nothing really. These are presented as typical applications to group theory and I'm not at ease with the subject so I'd like to see how you think on this example (in order to get a better idea). Can you hint me? Thank you.

This is a question in Pinter's A Book of Abstract Algebra.     Let $S=\{g\in G\mid \operatorname{ord}(g)=p\}$. Prove the order of $S$ is a multiple of $p-1$.   In his solution Pinter says $a \in S$ implies that $a$ generates a subgroup with $p-1$ elements. Shouldn't there be $p$ elements $\{1,a^1,\dots,a^{p-1}\}$? Or is it typical to only count the non-trivial elements in a subgroup?


I have Ubuntu machines that will be used by students and I would like it that every time google chrome is closed and reopened it reset to default settings. Do any of you know where to set that up?

I'm trying to boot a chrome application shortcut in full screen (kiosk mode).  Launching as an application shortcut is straightforward by appending the command --app=http://website.com. But the kiosk/fullscreen mode --kiosk or --start-maximized doesn't work.  I've looked up the commands through man google-chrome. I doesn't look like the option exists.  Is this option hidden, or are there alternatives? A way of starting chrome in fullscreen by default? I'm guessing that there is a way to fake a key press on F11 after chrome has started. Though this really isn't an ideal solution.


caught between a rock and a hard place   Where is this expression coming from? I understood the meaning but, for me, literal translation doesn't make sense. Can you give me some image?

What is the origin and definition of the expression "caught between a rock and a hard place"? I also heard it in a situation where it could have had a jocose double sense, but I may have misunderstood.


if i add add-apt-repository -y ppa:ondrej/php how can i just updated to pull the info from the new repo? I don't want to do apt update and get an update from all of the repo's installed. I just want to pull in the fresh data from the newly added repo.  is that possible?

When I add a PPA and I want to install some of its content, it is quite annoying to re-update all my apt list using apt-get update.  Is it instead possible to only sync the content of a given repository?


Let $\{a_n\}$ be a sequence such that $a_1 = 1 , a_{n+1} = \sqrt{6+a_n}$. We want to prove that this sequence is monotonic (increasing) and it is also bounded. So we can prove that it is convergent. I don't know how to start proving it that it is bounded. It is very easy to see that it is convergent to 3 by testing some number or if we think that we know it is convergent and then finding its limit in infinity. But I don't know how I can prove that it is bounded and monotonic so I can prove that it is convergent.

$\{a_n\}$ sequence $a_1=\sqrt{6}$ for $n \geq 1$ and $a_{n+1}=\sqrt{6+a_n}$ show that it convergence and as well find $\lim \limits_{n \to \infty} a_n$  In order to show that that sequence convergence I need to show that :  $$\lim_{n \to \infty} a_n= L$$  While $L$ is finite.  Using the calculator. I assume that L=3 because :  $$\sqrt{6+\sqrt{6+\sqrt{6+\sqrt{6........}}}}=2.999 \cong  3$$  I really don't think that this method is good enough to established that $\lim \limits_{n \to \infty} a_n= 3$ since it based on intuition.  I'll be glad to hear any ideas for an established method to show this.?  Any help will be appreciated.


I have imported an stl file to blender and its separate objects I can`t figure  out how to deselect the objects.  I have tried all the selection and deselection option s  The file was made on 123D this is the STL file I imported to blender and I want to un-group the highlighted objects any suggestion thanks?

I know I can use Ctrl+L to select vertices connected to a given one than P to separate selected vertices and move them in another object (as explained  for example).  But, is there a shortcut to do this automagically when there is like one hundred sub objects that I would like to separate ?


When I type the command   top   The first row of the output is   29646 Usernam+  20   0 7041320 1.047g 105604 S  1267  0.6 256:11.86 MATLAB   As you can see, the CPU utilization is 1267%. That means, this process is using 13 CPU of the server. By the following command, I try to force this process to use only one CPU (The 30th CPU of server)  taskset -c -p 30 29646   However, I still see the CPU utilization of the process is about 1300%. Why taskset is not working properly?

I'm attempting to limit a process to a given number of CPU cores. According to the taskset man page and , the following should work:  [fedora@dfarrell-opendaylight-cbench-devel ~]$ taskset -pc 0 <PID> pid 24395's current affinity list: 0-3 pid 24395's new affinity list: 0   To put it simply - this doesn't work. Putting the process under load and watching top, it sits around 350% CPU usage (same as without taskset). It should max out at 100%.  I can properly set affinity via taskset -c 0 <cmd to start process> at process spawn time. Using cpulimit -p <PID> -l 99 also . In both cases, putting the process under the same load results in it maxing out at 100% CPU usage.  What's going wrong here?


Hii have the recursion code below and while stepping through it i noticed that the value of jsonElement is not preserved well after stepping out of inner recursions. How do i go about it?  allnodes = getArrayOfNodes(tree); function toJson(node){      childrenList = []      jsonElement = {}     jsonElement["name"] = node.data       allnodes.forEach(function(item, index){         if(isParentOf(node, item) == true){             allnodes.splice(index, 1)             childrenList.push(toJson(item))         }     })     jsonElement["children"] = childrenList      return jsonElement }

What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally?


I have 7 *.txt files each with 2 columns of data thus:  time(mins) contacts 3.25    8 1.166666667 4 3.2 6 3.2 7 2.25    8 5.466666667 12 2.25    3 2.166666667 7   I'd like to plot them in separate scatter plots (via TikZ or other at your discretion) but on the same page. I've exported excel versions and they look somewhat unprofessional. Can you point me in the right direction, or a push to get started?  I'd also like to put on a linear regression line with its equation and R^2 value. I can provide both but I see in  it's possible to do it automatically.   an MWE:  \begin{tikzpicture}[only marks, y=.5cm]  \draw plot[mark=*,xshift=-6cm] file {data/ScatterPlotExampleData.data}; \draw[->,xshift=-6cm] (6,0) -- coordinate (x axis mid) (17,0); \draw[->,xshift=-6cm] (6,0) -- coordinate (y axis mid)(6,27); \foreach \x in {6,8,10,12,14,16}     \draw [xshift=-6cm](\x cm,1pt) -- (\x cm,-3pt)         node[anchor=north] {$\x$}; \foreach \y/\ytext in {0/0,2.5/5000,5/10000,7.5/15000,10/20000,12.5/25000}     \draw (1pt,\y cm) -- (-3pt,\y cm) node[anchor=east] {$\ytext$}; \node[below=1cm] at (x axis mid) {Education}; \node[left=2cm,rotate=90] at (y axis mid) {Income}; \end{tikzpicture}   Equally this matlab2tikzlooks interesting

I am trying to plot a scatterplot with a fit line that I have already calculated, but I am having trouble getting them to line up and use the same scale. I tried doing it with  \begin{tikzpicture}[domain=0:8] \begin{axis}[xlabel={$\Delta x$ (m)}, ylabel={$Mg$ (N)}]     \draw[color=red, domain=0:1000] plot (\x,{0.0051026+10.372231*\x}) node[below right] {}; \addplot[scatter, only marks, scatter src=\thisrow{class},       error bars/.cd, y dir=both, x dir=both, y explicit, x explicit, error bar style={color=mapped color}]       table[x=x,y=y,x error=xerr,y error=yerr] { x      xerr      y        yerr     class 0.0047 0.0007071 0.054039 0.000098 0 0.0142 0.0007071 0.152651 0.000098 0 0.0237 0.0007071 0.252051 0.000098 0 0.0332 0.0007071 0.350466 0.000098 0 0.0525 0.0007071 0.548380 0.000098 0 0.0622 0.0007071 0.646893 0.000098 0 0.0720 0.0007071 0.746195 0.000098 0 0.0802 0.0007071 0.844709 0.000098 0 }; \end{axis} \end{tikzpicture}   but I am getting a plot that looks like    Can I make the fit line match up with the scatter plot with the type of plot I am using? If not, how can I make this work?


In the movies, Luke Skywalker only knows the name "The Emperor". He never even mentions "Darth Sidious" or "Emperor Palpatine". Surely Luke Skywalker knows that the Emperor is Darth Vader's master. But does he know that the Emperor is also Darth Sidious?

Similar to , I'm asking the more specific question, was Luke aware that the Emperor was a Sith Lord? I don't recall it being mentioned in any of the films.  If yes, at what point does he learn this? If not why did Yoda or Obi-Wan not warn him?  Perhaps he could have avoided being defenseless and struck by Force Lightning if he'd been made aware?


Currently, comments with about >35 upvotes have the same upvote-counter color as that of <5 upvotes (which is some shade of gray). Shouldn't more upvoted comments have a more prominent counter color like it's done on SO? Meta and workplace currently seem to follow this weird scheme.   I'm tagging this a bug. Please edit if you feel otherwise.

High voted comments are in black text and look boring and unremarkable, while comments with a few votes have the red "hot" color on them. (I have no idea what is with the blue 25 :P)  Could this be changed so that highly voted comments actually look highly voted?


Is there a native JavaScript function (or library/module for JavaScript) that modifies a key's value and then returns the full object?  Here's what I've done:  function modifyJSON(jsob, key, val) {     var newjsob = JSON.parse(JSON.stringify(jsob));     newjsob[key] = val;     return newjsob; }   (Of course, if I wanted to modify the original, I could delete var newjsob... and work with jsob directly.)  This works, but if this type of functionality has already been implemented somewhere, I'd prefer to use that than roll my own.

What is the most efficient way to clone a JavaScript object? I've seen obj = eval(uneval(o)); being used, but . I've done things like obj = JSON.parse(JSON.stringify(o)); but question the efficiency.  I've also seen recursive copying functions with various flaws.  I'm surprised no canonical solution exists.


Show that there exists no smooth function $f:\mathbb{R}^2→\mathbb{R}$,such that $f(x,y)\geq 0$ for any $(x,y)\in\mathbb{R}^2$, with exactly two critical points$(x_1,y_1)\in\mathbb{R}^2$, $(x_2,y_2)\in\mathbb{R}^2$ and $f(x_1,y_1 )=f(x_2,y_2 )=0$.

i) Show that there does not exist a smooth function $f:\mathbb{R} \rightarrow \mathbb{R}$, s.t. $f(x) \geq 0$, $\forall x \in \mathbb{R}$, $f$ has exactly two critical points, $x_1,x_2\in\mathbb{R}$ and $f(x_1)=f(x_2) = 0$. (This part is easy).  ii) Show that there does not exist a smooth function $f:\mathbb{R}^2 \rightarrow \mathbb{R}$, s.t. $f(x,y) \geq 0$, $\forall (x,y) \in \mathbb{R}^2$, $f$ has exactly two critical points, $(x_1,y_1),(x_2,y_2)\in\mathbb{R}^2$ and $f(x_1,y_1)=f(x_2,y_2) = 0$.   I have tried several methods, however, it does not work, could anybody help me out?


I am looking for the title of a short story where a space craft is made up of various creatures from around the universe.  If I remember correctly the skin of the craft is made of creatures. the computer is just a giant brain. The engine creature suffers some form of malfunction and a nearby suitable replacement is located which happens to be a human. Although not as good as the original the human will suffice. At first he is reluctant but then discovers he loves it. I think they call propelling the craft as "pushing".   I hope somebody can help. I had this book many years ago and I don't know what I have done with it.

I have a very vague recollection of a short story in which somehow the parts of a spaceship were aliens of different races, whose innate powers allowed them to perform a function (braking, steering...). The end revelation is about the nature of the ship's accelerator.  Any bell ringing?


How do the buttons (like A, B, X, Y, and D-Pad) on game pads (such as the Xbox controller) interact with the PCB? If my question sounds vague, refer to the pictures below:    Are A/B the same as C/D? In game, the D-Pad (left) shows up as "Axis", while the buttons (right) just show up as "button".  What are A/B/C/D called, and what are they made of? It all looks and feels like rubber, but if that were the case then it wouldn't have any effect on the electrical properties of the PCB in that area (right?).  How does the logic of A/B and C/D work? How does B pressing on A (or D pressing on C) send a signal to the computer saying "button X has been pressed"/"D-Pad UP has been pressed"?  For reference, I know how a push-button works; it makes and breaks physical connections, which in turn impedes or allows electrical current to flow. But I can't see how that happens in this picture.  Also, here's a picture of the other side of the PCB (it might help).

This may be a stupid question, but I have searched online for a little bit and can't seem to find my answer. I am working on a circuit board that uses buttons that i've never seen before. These buttons just have a metal lead around them and an LED in the middle (for lighting up the button I'd assume) but how does a button like this even work? I've attached some pictures to show you what i mean.    this is the back of the push buttons from the device


I want to change the DPI of the screen that is used in Ubuntu 11.10. How do I do this?  I don't just want to change the font size like in , but I also want the icons to appear bigger.

I have installed Ubuntu on my desktop, but my monitor don't pass more than 800x600 resolution.  My monitor is good at 1360x768. How can I set resolution at 1380x768 ?


Is it possible to backup the custom keyboard shortcuts and restore them when doing a fresh install?

I have customized some of the shortcuts in System ▸ Preferences ▸ Keyboard Shortcuts.  How can I restore individual shortcuts to their default settings? I do not want to reset all of the shortcuts, just a few of my choice.


I have a Python dictionary in a single file as follows: {'weight': ['2', '23', '12', '65', '34', '55', '23', '23', '68', '101'],  'Age': ['35', '23', '14', '39'],  'Count': ['23', '335', '112', '33', '543']}  I would like to sort just one key/value e.g. Age to be 'Age': ['14', '23', '35', '39']. The other keys/values to remain unchanged. How to retrieve a single key and sort its values? Tks

What is the best way of creating an alphabetically sorted list in Python?


I am trying to delete the 2nd to last item in my array. Using delete puts my indexing out of order?  Getting this using delete myArr[15];

What is the difference between using  on the array element as opposed to using ?   For example:  myArray = ['a', 'b', 'c', 'd'];  delete myArray[1]; //  or myArray.splice (1, 1);   Why even have the splice method if I can delete array elements like I can with objects?


i am an Indian. i want to go to nepal , Kathmandu within 2 weeks .but i don't have passport. so can i go to nepal from varanasi just having adhaar card as my identity proof  and how much will it cost to reach nepal exculding travelling fare.

I am an Indian Citizen and I wish to drive to Nepal. I am aware of the fact that if you enter Nepal by air, even as an Indian Citizen, you will be required to present an ID.   According to Wikipedia, Nepal has open borders with India underneath the . Thus, Indian citizens do not require a visa in order to enter Nepal, but while traveling by road, is an ID required?


I'm on Ubuntu 12.04, I have updated openssl with the latest update :  $ openssl version -a OpenSSL 1.0.1 14 Mar 2012 built on: Mon Apr  7 20:33:29 UTC 2014   And also updated libssl   $ sudo apt-get install libssl1.0.0 Reading package lists... Done Building dependency tree        Reading state information... Done libssl1.0.0 is already the newest version.   Then I rebooted the server but still show vulnerability using . Any ideas? Thanks.

I was looking at a reliable and portable way to check the OpenSSL version on GNU/Linux and other systems, so users can easily discover if they should upgrade their SSL because of the Heartbleed bug.  I thought it would be easy, but I quickly ran into a problem on Ubuntu 12.04 LTS with the latest OpenSSL 1.0.1g:  openssl version -a  I was expecting to see a full version, but instead I got this:  OpenSSL 1.0.1 14 Mar 2012 built on: Tue Jun  4 07:26:06 UTC 2013 platform: [...]  To my unpleasant surprise, the version letter doesn't show. No f, no g there, just "1.0.1" and that's it. The listed dates do not assist in discovering a (non-)vulnerable version either.  The difference between 1.0.1 (a-f) and 1.0.1g is crucial.  Questions:   What is a reliable way to check the version, preferably cross distro? Why isn't the version letter showing in the first place? I was unable to test this on anything else but Ubuntu 12.04 LTS.   Others are reporting this behaviour as well. A few examples:       Some (distro-specific) suggestions rolling in:   Ubuntu and Debian: apt-cache policy openssl and apt-cache policy libssl1.0.0. Compare the version numbers to the packages here:  Fedora 20: yum info openssl (thanks @znmeb on twitter) and yum info openssl-libs   Checking if a older version of OpenSSL is still resident:   It's not completely reliable, but you can try lsof -n | grep ssl | grep DEL. See  on why this may not work for you.   It turns out that updating the OpenSSL package on Ubuntu and Debian isn't always enough. You should also update the libssl1.0.0 package, and -then- check if openssl version -a indicates built on: Mon Apr  7 20:33:29 UTC 2014.


Are there any nontrivial field endomorphisms of $\mathbb{H}$ that are not the identity map when restricted to $\mathbb{R}$? I realize that the only nontrivial endomorphism on $\mathbb{R}$ is the identity map, so if the desired function $f$ exists, it must be that $f(\mathbb{R}) \ne \mathbb{R}$. Are there any such mappings?

Is the quaternion ring an EAS Division ring?  An EAS Division ring is a ring $D$ such that each endomorphism of $D$ is surjective.  I know that $\mathbb{R}$ and $\mathbb{Q}$ are EAS Division rings.


I would like to know if there is some expression for the magnetic field generated by a electron spin.  As far as I know, the spin provides a magnetic moment to the electron and a magnetic dipoles momentum $\vec m$ produces a field:  $H = {1\over4\pi}  \left({3\vec r(\vec m\cdot\vec r)\over r^5} - {\vec{m}\over r^5}\right)$   However, the spin can be measured in each at any direction so, is the previous expression valid for the electron spin?

While a treatment of electron spin can be found in any introductory textbook, I've noticed that the electron's magnetic field seems to be treated classically. Presumably this is because a quantum treatment of the electromagnetic field would venture into the much more difficult topic of quantum electrodynamics. However, treating the magnetic field classically also seems to create conceptual difficulties. How can we write something like  $$\mathbf{\mu} = \frac{g_e \mu_b}{\hbar} \mathbf{S}$$  and treat the left-hand side as a vector, while treating the right-hand side as a vector-valued operator?  So, what does really happen when we measure the magnetic field around an electron? For simplicity imagine that the electron is in the ground state of the hydrogen atom, where it has zero orbital angular momentum. It seems to me that we can't observe what looks like a classical dipole field, because such a field would have a definite direction for the electron's magnetic moment, which would appear to contradict the quantum-mechanical properties of spin.  My guess is that measuring any one component of the magnetic field at a point near an electron would collapse the spin part of the electron wave function, and in general the three components of the magnetic field will fail to commute so we cannot indeed obtain a definite direction for the electron magnetic dipole moment. However, I'm not even sure how to begin approaching this problem in a rigorous fashion without breaking out the full machinery of QED. For an electron in a magnetic field we have the Dirac equation. For the magnetic field of the electron I wasn't able to find an answer online or in the textbooks I have at hand.


I have the following code that I use to populate a DataTable with information from a CSV file.  I have declared a DataTable as a class attribute  public partial class Super_Proyectos_LoadProjects: System.Web.UI.Page {    private DataTable dt;    private DataTable datosC;    string rutaActual;    .... }   protected void btnLoad_Click(object sender, EventArgs e) {     if(fupCSV.HasFile)     {         try         {             string csvPath = Server.MapPath("~/Projects/") + Path.GetFileName(fupCSV.PostedFile.FileName);             fupCSV.SaveAs(csvPath);              dt = new DataTable();                             dt.Columns.AddRange(new DataColumn[8] { new DataColumn("Project ID", typeof(string)), new DataColumn("Worker ID", typeof(string)),                                 new DataColumn("Project Name", typeof(string)));             dt.TableName = "Project";              string csvData = File.ReadAllText(csvPath);               foreach(string row in csvData.Split('\n'))             {                 if(!string.IsNullOrEmpty(row))                 {                     dt.Rows.Add();                     int i = 0;                      foreach (string cell in row.Split(','))                     {                         dt.Rows[dt.Rows.Count - 1][i] = cell;                         i++;                     }                 }                                 }                                                 gvProyectos.DataSource = dt;             gvProyectos.DataBind();                         }         catch(Exception)         {             string script = @"<script type='text/javascript'>                         alert('Error al cargar los datos.');                     </script>";              ScriptManager.RegisterStartupScript(this, typeof(Page), "alerta", script, false);         }                 } }   Everything works fine here  protected void btnAccept_Click(object sender, EventArgs e) {     Response.Write(dt.Rows[0][0].ToString()); }   But when I click on the accept button I get the following error:     Object reference not set to an instance of an object.   Why do I get error when using the DataTable outside where it was loaded?

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I'm reading :  Earth [...] is the third planet from the Sun[...] The Earth's human population is [...]   Then the   The Earth is certainly the most familiar planet [...] Apollo 11 shot of Earth Galileo shot of the Earth and Moon   I think no other planets have this problem. Nobody would say "The Mars is certainly the first planet that humans will travel to", so what's happening here?  So what is the correct way of referring to the planet that i'm on right now? Does it require "THE" or not? How come English-speaking Earthlings keep changing the rules in the middle of a paragraph?

In what cases do we have to put the definite article the before each of these words:   Sun Moon Earth   and in what cases do we not need to?


I see some SE sites moving to the new format, such as MSE, and this appears to work on my desktop and mobile. Most of the others are on the old format, which again works well on desktop, and is passable on mobile.  However, a couple of sites do weird things. Outdoors is especially strange - I assume it has some messed up formatting. See here - there is no nav bar, right hand column, no review link, etc:    I have turned off Ghostery and Scriptsafe blocking temporarily, the SE chat extension makes no difference, and I am running no scripts under TamperMonkey. It's an up-to-date Windows 10 install.  By comparison, here is how my machine renders MSE.  New layout, but all working (even if I don't quite like it as much as the earlier version...):

I seem to have clicked on something that changed my display preferences. The main site is now very minimalistic, with fewer controls and different fonts.  I want to change it back, but where is it?


The Lorentz group is defined to be the set of linear transformations that leave $ds^2 = -dt^2 + |d\vec{x}|^2$ invariant. The Poincaré group contains the Lorentz group, but now we allow transformations of the form $t' = t+a$ where $a$ is some constant. Is there a name for the group of transformations that leave $ds^2 = -dt^2 + |d\vec{x}|^2$ invariant without assuming linearity? The answers to this question  claims that any nonlinear transformation will have some "privileged" point, and hence we disregard them as nonphysical. However, I am curious nonetheless if there is a name for this group and any interest in it.

In almost all proofs I've seen of the Lorentz transformations one starts on the assumption that the required transformations are linear. I'm wondering if there is a way to prove the linearity:  Prove that any spacetime transformation $\left(y^0,y^1,y^2,y^3\right)\leftrightarrow \left(x^0,x^1,x^2,x^3\right)$ that preserves intervals, that is, such that  $$\left(dy^0\right)^2-\left(dy^1\right)^2-\left(dy^2\right)^2-\left(dy^3\right)^2=\left(dx^0\right)^2-\left(dx^1\right)^2-\left(dx^2\right)^2-\left(dx^3\right)^2$$  is linear (assuming that the origins of both coordinates coincide). That is, show that $\frac{\partial y^i}{\partial x^j}=L_j^i$ is constant throughout spacetime (that is, show that $\frac{\partial L_j^i}{\partial x^k}=0$).  Thus far all I've been able to prove is that $g_{ij}L_p^iL_q^j=g_{pq}$ (where $g_{ij}$ is the metric tensor of special relativity) and that $\frac{\partial L_j^i}{\partial x^k}=\frac{\partial L_k^i}{\partial x^j}$. Any further ideas?


I've read numerous examples converting from String to Boolean.  For example,  myString = (myString == "true");  But I'm unable to apply the logic to my code. Can someone help?     CommonConfig.getFeatureFlags['analytics.demo'] returns "true" (Note   the "").(That's how backend returns it)   var FeatureFlag = _.extend(CommonConfig, {     demoFeature: String == CommonConfig.getFeatureFlags['analytics.demo'], //either "true" or "false" but I want to make it to true or false });   Question: I want to convert from String "true" to boolean. And pass true or false based upon!  Can someone help?

Can I convert a string representing a boolean value (e.g., 'true', 'false') into a intrinsic type in JavaScript?  I have a hidden form in HTML that is updated based upon a user's selection within a list. This form contains some fields which represent boolean values and are dynamically populated with an intrinsic boolean value. However, once this value is placed into the hidden input field it becomes a string.  The only way I could find to determine the field's boolean value, once it was converted into a string, was to depend upon the literal value of its string representation.  var myValue = document.myForm.IS_TRUE.value; var isTrueSet = myValue == 'true';   Is there a better way to accomplish this?


I have a long literature.bib file. It has been running without a problem, suddenly it seems to not run further: INFO - Logfile is 'main.blg' INFO - Reading 'main.bcf' INFO - Found 27 citekeys in bib section 0 INFO - Processing section 0 INFO - Globbing data source 'literature/literature.bib' INFO - Globbed data source 'literature/literature.bib' to literature/literature.bib INFO - Looking for bibtex format file 'literature/literature.bib' for section 0 INFO - LaTeX decoding ... INFO - Found BibTeX data source 'literature/literature.bib'  It stays there and never generates the literature in the text nor shows an error.

I am on a Mac with MacTex 2020 and ran into a strange problem with Biber. Working on a document all was fine, I did not change the bibliography (says my git) and only fixing typos (not even adding cites) and suddenly latexmk stopped working after a Biber run, while that looked like  INFO - This is Biber 2.14 INFO - Logfile is 'doc.blg' INFO - Reading 'doc.bcf' INFO - Found 31 citekeys in bib section 0 INFO - Processing section 0 INFO - Globbing data source 'literature.bib' INFO - Globbed data source 'literature.bib' to literature.bib INFO - Looking for bibtex format file 'literature.bib' for section 0 INFO - LaTeX decoding ... INFO - Found BibTeX data source 'literature.bib'   so harmless in my view. Then with --debug I additionally get in the end.  INFO - LaTeX decoding ... warning: overriding existing definition of macro "jun" warning: overriding existing definition of macro "jul" warning: overriding existing definition of macro "sep" warning: overriding existing definition of macro "jan" [...] warning: overriding existing definition of macro "nov" INFO - Found BibTeX data source 'literature.bib' Unicode::UCD: failed to find unicore/version in /var/folders/hm/gt63cn0j2r7bwbzw7c1hww1r0000gn/T/par-626572676d616e6e/cache-2f8a664c3c933a44d096bcc8d018a5e92bced897/inc/lib /var/folders/hm/gt63cn0j2r7bwbzw7c1hww1r0000gn/T/par-626572676d616e6e/cache-2f8a664c3c933a44d096bcc8d018a5e92bced897/inc CODE(0x7fd026aeb5a8) CODE(0x7fd026aebb90) at /var/folders/hm/gt63cn0j2r7bwbzw7c1hww1r0000gn/T/par-626572676d616e6e/cache-2f8a664c3c933a44d096bcc8d018a5e92bced897/inc/lib/Biber/Input/file/bibtex.pm line 1011.   It seems unrelated to the library itself since deleting a few entries (going through deleting one half, then the other), the problem persists. It does not happen for an empty literature, but as soon as a first entry is added (just author/journal/title/year/volume/pages - no utf8-only chars) this error message appears.  what does this last error message mean?  How can I solve this?


I am looking to upgrade to 16.04 but the updater will not detect it. Tried many mirrors, checked all the possible update icons. BTW, I am running 14.04 LTS

So, today is July 21st and . gives me an option to download 16.04.1 LTS. However, attempting to upgrade gets me this message -  $ sudo do-release-upgrade Checking for a new Ubuntu release No new release found   What is wrong? Does it matter that I am running apt-get update behind apt-cacher-ng?  Note: Commenting out the files in apt.conf.d that used apt-cacher-ng did not make a difference.  Edit: Explanation for possible duplicates:  deals with upgrade from 12.04LTS to 14.04LTS. My question is specific to 14.04 LTS to 16.04.1 LTS upgrade. Old answers, while good for archival purposes are less relevant in a fast changing package like ubuntu. Moreover none of the answers answer what is wrong. The link  pointed out is mentioned in one of the comments. This Q & A is more helpful for people upgrading today than the work around mentioned in "".


Perhaps this is obvious and I am overlooking something, but why are the homology groups of compact manifolds finitely generated?

Let G be a finitely generated abelian group and M a compact manifold,  I want to prove that $H_r(M,G)$ is finitely generated for $r\ge 0 $.  First I was thinking if  I could do induction over $r$ because for $r=0$, $H_0(M,G) \cong \bigoplus_{i=1}^nG$ where $n$ denotes the number of connected components of M.But for $r>0$ I can't see a way to relate $H_r(M,G$) and $H_{r+1}(M,G)$.  Then I tried to use the fact that for every compact surface there exists a finite cover $\{A_i\}_{i=1}^m$ such that the finite intersections of $A_i$'s are contractile.Let $\{A_i\}_{i=1}^m$ such cover for $M$.Then,using induction on $m$, we have :  -For $m=0$, $M$ is contractile and $G$ finitely generated then $H_r(M,G) $is finitely generated.  -For $m=r$ it's true by induction hypothesis.  -For $m=r+1$ now putting $A_{r+1}=B$ and $\cup_{i=1}^r A_i=A$, and using Mayer Vietoris we get:  $$ ...\rightarrow H_{r+1}(A\cap B,G)\rightarrow  H_{r+1}(A,G) \oplus H_{r+1}(B,G) \rightarrow H_{r+1}(M,G)\rightarrow H_{r}(A\cap B,G) \rightarrow...$$   Here I don't know what to do, maybe I'm missing some algebraic argument It's easy to see that $H_{r+1}(A\cap B,G)$ and $H_{r+1}(A,G) \oplus H_{r+1}(B,G)$ are finitely generated.But how can I argue that $H_{r+1}(M,G)$ is finitely generated? Any idea would be aprecciated.


My reputation on Stack Overflow was lessened by 105 points today.  Does anybody know why?

Message appearing when a user was removed.     It seems I lost 1765 reputation points on Stack Overflow yesterday. The reason given in my history is "removed", with the description of "User was removed ()". I don't understand what that means. What caused this?


Try to store prime numbers and output them but the console is empty and nothing happens  int main() {     vector <int> v;     int n = 1000;          int order; // Nth order     //cin >> order;     primes(n, v);     for (auto i = v.begin(); i != v.end(); ++i)         cout << *i << ' ';     return 0; }

What is the difference between    a parameter passed by reference a parameter passed by value?   Could you give me some examples, please?


:  But somehow, despite all of the reasons it shouldn’t work, it does. .   - it is strongly suggested that this doesn't work.  So at best, Shawyer has invented a very inefficient and expensive fan.  Even further - :  Shawyer's "analysis" is a mess, incoherent and deeply confused about fundamental aspects of relativity.  My question is: Has NASA confirmed that Roger Shawyer's EmDrive thruster works? Edit: There may . I just don't know what it means. Edit #2 I don't believe this is a duplicate of the other question - as it is not clear how much to trust NASA's engineers - or what their comment actually means.

Recently, there was some news that said that the researchers at NASA have come across some impossible kind of space engine which does not require any fuel. I have read at a few places like ,  and . They all say that this engine seems to violate the laws of physics including conservation of momentum.  The original paper is .  Is the statement that it violates conservation of momentum true?


Are there any Keyboard Shortcuts to Shutdown? (e.g. in Windows Alt+F4+Alt+F4 Right Arrow Enter)

Is there a keyboard shortcut available to shutdown the computer?  I know I can use the Power button, but I would like to be able to it from the keyboard.  If such a shortcut does not exist already, how do I set one?


Imagine a horse is tethered to a cart. According to Newton's third law, when the horse pulls on the cart, the cart will also pull backwards on the horse. Since the two objects are attached together, they are technically the same object, and they cannot accelerate. This doesn't make any sense. In the real world, horse carts are able to move, even though they are attached together. Am I overlooking something here?

Given Newton's third law, why is there motion at all? Should not all forces even themselves out, so nothing moves at all? When I push a table using my finger, the table applies the same force onto my finger like my finger does on the table just with an opposing direction, nothing happens except that I feel the opposing force. But why can I push a box on a table by applying force ($F=ma$) on one side, obviously outbalancing the force the box has on my finger and at the same time outbalancing the friction the box has on the table? I obviously have the greater mass and acceleration as for example the matchbox on the table and thusly I can move it, but shouldn't the third law prevent that from even happening? Shouldn't the matchbox just accommodate to said force and applying the same force to me in opposing direction?


I have the following javascript code:  $(function (){     $('a.folder').click(function() {        // code goes here ...     } });   And the following html code:  Etudes de cas   Whenever I click on the link, the javascript code is never reached. I must say that this html code is generated dynamically after the page loaded. Is this the reason? Any workaround?

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


In the below example I want to take $15 as normal string and it must consider "($\d+.?\d+)" as pattern  my data is dynamic so backslash(//)$15 won't work because data could be anything.  Is there a way if it is a pattern take it a pattern if there is any value with metachr, it should consider it as a string. regex = "this is $15 Fee will be ($\d+.?\d+)" my_text = "this is $15 Fee will be $20"; Pattern pattern = Pattern.compile(regex,Pattern.CASE_INSENSITIVE); Matcher matcher = pattern.matcher(my_text); System.out.println(matcher.find()); O/p = false // op is false because it takes $ from $15 as regex pattern

Does Java have a built-in way to escape arbitrary text so that it can be included in a regular expression? For example, if my users enter "$5", I'd like to match that exactly rather than a "5" after the end of input.


im trying to count the number of ocurrences for a list in awk, actually im able to get it for each user the total attemps, but i wanted total attemps by day. I have a txt file something like: ID, Event, Date, Type, Message, API, User, Protocol, Attemps  1, ERROR, 30-NOV-20, 4, TEXT, 2, user1, GUI, 9  i used below awk to count total attemps: awk 'FNR == NR {count[$(NF-3)]++; next} {print $(NF-3), $3 "\t" count[$(NF-3)]}' file file  Can someone help me? Expected output: USER  ATTEMPS DATE user1 3       20-NOV-2020 user1 6       22-NOV-2020 user2 2       01-DEC-2020 user3 4       12-NOV-2020 user3 19      18-NOV-2020

Suppose you have a file that contains IP addresses, one address in each line:  10.0.10.1 10.0.10.1 10.0.10.3 10.0.10.2 10.0.10.1   You need a shell script that counts for each IP address how many times it appears in the file. For the previous input you need the following output:  10.0.10.1 3 10.0.10.2 1 10.0.10.3 1   One way to do this is:  cat ip_addresses |uniq |while read ip do     echo -n $ip" "     grep -c $ip ip_addresses done   However it is really far from being efficient.  How would you solve this problem more efficiently using bash?  (One thing to add: I know it can be solved from perl or awk, I'm interested in a better solution in bash, not in those languages.)  ADDITIONAL INFO:  Suppose that the source file is 5GB and the machine running the algorithm has 4GB. So sort is not an efficient solution, neither is reading the file more than once.  I liked the hashtable-like solution - anybody can provide improvements to that solution?  ADDITIONAL INFO #2:  Some people asked why would I bother doing it in bash when it is way easier in e.g. perl. The reason is that on the machine I had to do this perl wasn't available for me. It was a custom built linux machine without most of the tools I'm used to. And I think it was an interesting problem.  So please, don't blame the question, just ignore it if you don't like it. :-)


Are the following methods always equivalent within a class? In other words, within MyClass can I interchangeably use cls in a class method and MyClass in a static method? class MyClass:      @classmethod     def my_class_method(cls):         cls.attribute = "a"      @staticmethod     def my_non_class_method():         MyClass.attribute = "b"

What is the difference between a function decorated with  and one decorated with ?


$G$ is a group.      If $H, K \le G, |H|, |K| < \infty$, then $$|HK| = \frac{|H||K|}{|H \cap K|}$$   How to prove it?  UPD:  I tried to prove that this function is bijective:    So if i prove it, I can do next thing:    But how to prove it?

Let $H$, $K$ be subgroups of $G$. Prove that $o(HK) = \frac{o(H)o(K)}{o(H \cap K)}$.  I need this theorem to prove something.


I started general topology recently, and a partner of mine made a example of two different topologies generated by the same basis, so I'd like to know if that is possible, and if it is not, to see a proof of it.

$(X, \mathcal{T}_X), (Y,\mathcal{T}_Y)$ be topological space, and let   $A, B$ be subset of $X,Y$ respectively.      Now, $(X \times Y, \mathcal{T}_{X \times Y})$ be product topology. $A  \times B \subset X \times Y$. Consider subspace topology   $\mathcal{T}_1$ on $A \times B$      Also, $(A, \mathcal{T}_A), (B, \mathcal{T}_B)$ where $\mathcal{T}_A$   and $\mathcal{T}_B$ are subspace topologies on $A, B$   respectively,consider product topology $\mathcal{T}_2$ on $A \times B$      Prove $\mathcal{T}_1 = \mathcal{T}_2$   My idea is to show that the bases of $\mathcal{T}_1$ and $\mathcal{T}_2$ are same. where $\mathcal{T}_1$ basis is {$(A \times B) \cap (U \times V)  | (U \times V) \in \mathcal{T}_{X \times Y}$}  and $\mathcal{T}_2$ basis is {$U_0 \times V_0 | U_0 \in \mathcal{T}_A,  V_0 \in \mathcal{T}_B$}. I know how to show these two bases are equal. However, I don't if this is sufficient to prove two topologies are equal.