I now understand that a similar question has been asked, but not everyone might come to the adapted solution for this version of the question straight away.  Is there a simple way to count the number of occurrences of every group of numbers in a string? I can't think of one and anything I can think of seems way too convoluted, for what seems like a simple ish task.  (note that any string of numbers in the line could be any length)  Example input:  AGTHDTGY35AHSJFHHFG7GHHAHH   Example output:  2

I need to solve this in a shell script. I am counting number of occurrence of the abc string below and I want to get the answer as 3.    echo abcsdabcsdabc | grep -o abc   abc   abc   abc     Assuming we do not have the -o option in grep, how do we approach this then?


I have just been told that in order to delete my Stack Overflow account I need to email team@stackoverflow.com.   What is the reason behind not providing privilege to a user to delete their own account?

How can I delete my Stack Exchange account(s)? Also,  What happens to my content? Can I request it be deleted as well? What if I'm suspended, rate-limited, or banned from posting questions or answers? What will happen to my votes? Will other users be impacted? Why wasn't my account deleted immediately after the timer expiring? What will happen to my pending bounties and close, reopen, delete, or undelete votes? I want my account deleted on all Stack Exchange sites. How do I do this? Will my profile on chat be removed once I delete my site account?   For more information, see "" in the .


Okay, so if I have 2 blocks of different masses 4kg and 2kg placed side by side with possibly a distance of 1 molecule between them (sorry if the diagram doesn't show that). There is negligible friction on the surface they are kept. I apply a constant force of 20N on a side of the block with mass 4kg so both move with a constant acceleration. Now I know that the acceleration would be equal to the sum of masses divided by the force applied. But here comes the problem. When I apply force on the block, it starts moving with a constant acceleration of 20/4 which is equal to 5m/s. Hence it applies a force of magnitude 5*4=20N on the second block after moving the distance of 1 molecule. So according to newton's third law of motion, the second block will apply a reaction force of 20N on the first block as long as it is in touch with it. So the two forces should cancel each other out and the first block should not move. Since the first block stopped moving, the second block should stop moving too. Then why are the blocks moving? Please solve this mathematically.

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  homepage.asp (old legacy code)  with a div like this:

    I am loading another page with a self contained form (it submits to itself) in to this div like this:          $.get('Poll/poll.asp', function(data) {          $('#poll').html(data);}        );      The form on poll.asp looks basically like this :     <form id="formPoll" onsubmit="return false">

             Poll question here

                     <Input type="Radio" name="SelOPT" value="1" />	                     Option 1

                     <Input type="Radio" name="SelOPT" value="2" />	                     Option 2

         <input id="pollSubmit" type="submit" value=" Cast Vote " />

         <input type="Hidden" name="mode" value="vote" />         </form>   I am trying to submit the form without refreshing the page, but I need the page loaded in the div to reload to show the results of the form submission. On homepage.asp I have a script like this:          $(function() { //hang on event of form with id=formPoll $("#formPoll").submit(function(e) {      //prevent Default functionality     e.preventDefault();      //do your own request an handle the results     $.ajax({             url: 'Poll/poll.asp',             type: 'post',             dataType: 'json',             data: $("#formPoll").serialize(),             success: function(data) {             //if(data.success == true){ // if true (1)              //$("#poll").load("#poll > *");               $('#poll').html(data);      }     }             });          });     });     homepage.asp does not refresh on submit but it only submits the form data every other time the button is clicked and I have to manually refresh the page to reload the results. I think I have read every "refresh or reload div after submit" question on here with no luck. Any ideas would be appreciated. You can see a couple of the things I have tried commented out under the success function.

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.


I'm using MS Paint on WinXP at work, for capturing simple screenshots. Problem: MS Paint always wants to save in BMP format. How can I set PNG to be Paint's default file-saving format?  Note: Suggestions about other software are irrelevant. I know there are many other software tools available. But I'm asking specifically about MS Paint.

Every time I want to save an image I've pasted into the  application, it chooses a BMP/DIB format (which is the worst for saving things from the clipboard).  How can I hack Paint into defaulting to the JPEG format when saving images?  I am using Windows XP SP3 and Paint 5.1 at the moment. I hope though that any hacks might be generic and I'd be able to use them across all my Windows machines.


An OS is not typically I look for in a mobile or a laptop. Since almost a year now, I have been addicted to this game Clash of Clans on my Nexus 4 running Android 5.1. I am looking for experimenting with my Nexus and run Ubuntu Touch on it. Is there any possible way we can run Android apps on Ubuntu touch or Ubuntu mobile OS?

I'm wondering why Android apps won't be able to be run natively on . I mean, isn't it all just Linux?


In the Doctor Who episode "Blink", the Doctor tells Sally this about the Weeping Angels:     They are quantum-locked. They don't exist when they're being observed. The moment they are seen by any other living creature, they freeze into rock. No choice. It's a fact of their biology. In the sight of any living thing, they literally turn to stone.   Towards the end of the episode the Doctor then traps the four Angels by having them all facing each other after the TARDIS has dematerialised. If the Angels cease to exist while being observed, then how can they be observing each other while locked into stone? If the observation to trigger the quantum-lock counts as 'In the sight of any living thing', then they surely aren't actually trapped as when they're stone they don't exist so aren't observing one another, and so long as they move one at a time they could escape the formation the Doctor left them trapped in? Note that this question doesn't deal with how to generally defeat/damage an Angel in its quantum-locked state, but rather the very specific case and nuanced trap presented in this episode.

In the Doctor Who episodes with Weeping Angels, the Angels turn into statues when they are observed. In "The Time of Angels" and "Flesh and Stone", the Angel statues become deteriorated as the actual Angels die, which means that the state of the Angel's statue is connected to the state of its actual body.  Also in those episodes, the protagonists have weapons with the capability of destroying or at least severely damaging the statues, but they never use their weapons for that purpose, even when it would have been tactically useful to kill or injure a single Angel. This implies that they knew that destroying the statues would be useless or a waste of ammunition.  The Doctor says multiple times that when the Angels are quantum locked they turn into statues and that this is the ultimate defense mechanism. So, is there any explanation for what exactly happens when the Weeping Angels are quantum locked that resolves the apparent contradiction between the statues being the Angels' bodies and that harming the statues would not harm the Angels?


I am very new to SARIMA and I am really facing a poblem which p,q,P,Q to use. Here is ACF and PACF of first-difference, two first plots (stationary) and ACF and PACF of first-seasonal difference (two last plots).    I think that P=1, Q=1 because ACF and PACF of first-seasonal difference drop off at lag 1 and are outside the confidence band. What about p and q ? Can I san that p=2 and q=2 because it drop of at lag 2? Or should I take under consideration the fact that only at lag 4 ACF and PACF are outside confidence band? Is p=4 and q=4 or 2 for both?  Or should I do AIC test for (2,1,2)(1,1,1)12, (4,1,2)(1,1,1)12, (2,1,4)(1,1,1)12, (4,1,4)(1,1,1)12 and check which one has the smallest? Or assuming that p=2 and q=2 does not make any sense because its within the confidence band?  SARIMA (4,1,4)(1,1,1)12 gives me  lots of non-significant coefficients. :   Or maybe should I try SARIMA(7,1,4)(1,1,1)12, SARIMA(8,1,4)(1,1,1)12 ? But it really does not seem reasonable.  Please tell me what to do now :( Thank you for any help!

I would appreciate if someone could check the mathematical equation for the seasonal ARIMA (4,1,4) x (1,1,1) period 12 that I wrote. I have done it this way, but I am not really sure if it correct is. Can someone check it and correct it? I would be graetfull.  $(1+0.0789359 B - 0.0007957 B^2- 0.7559195B^3 + 0.2814265B^4)(1+0.0851737 B^{12}) (1-B) (1-B^{12}) Y_t= (1 - 0.4212575 B - 0.2042966  B^2 -0.9272988 B^3 + 0.5528213B^4)(1-0.8477401B^{12})e_t$  Please just tell me if I am thinking right. Coefficients here:      Thank you for your answer!  but how can I simplify it?   I am very new to SARIMA and I am really facing a poblem which p,q,P,Q to use. Here is ACF and PACF of first-difference (two top plots),  and ACF and PACF of first-seasonal difference.  I think that P=1, Q=1 because ACF and PACF of first-seasonal difference drop off at lag 1 and are outside the confidence band. What about p and q ? Can I then say that p=2 and q=2 because it drop of at lag 2? Or should I take under consideration the fact that only at lag 4 ACF and PACF are outside confidence band? Is p=4 and q=4 or 2 for both?  Or should I do AIC test for (2,1,2)(1,1,1)12, (4,1,2)(1,1,1)12, (2,1,4)(1,1,1)12, (4,1,4)(1,1,1)12 and check which one has the smallest? Or assuming that p=2 and q=2 does not make any sense because its within the confidence band?


I want to prompt the user for a password in a Java code, and I'd rather not have the input printed to the screen for security reasons.  I am aware of the class Console, but I would like to be able to run my program from an IDE for testing reasons. Any alternatives?

I use the Eclipse IDE to develop, compile, and run my Java projects. Today, I'm trying to use the java.io.Console class to manage output and, more importantly, user input.  The problem is that System.console() returns null when an application is run "through" Eclipse. Eclipse run the program on a background process, rather than a top-level process with the console window we're familiar with.  Is there a way to force Eclipse to run the program as a top level process, or at least create a Console that the JVM will recognize? Otherwise, I'm forced to jar the project up and run on a command-line environment external to Eclipse.


Today a couple of buffer overflows in NTP were announced , . It looks like updating my system to fix these issues is in order.   How can I find out if they have been fixed in the Ubuntu repositories, such that if I were to run:   sudo apt-get update sudo apt-get upgrade   then the fix would get installed and the vulnerability closed?   Edit: The selected answer specifically addresses the question of how to identify if a given CVE has been fixed or not, "Does Ubuntu generally post timely security updates?"  is certainly related but not identical

Concrete issue: The  is at version 1.0.5-1, released in July 2011 according to the .  The recent memory-disclosure vulnerability (, , ) isn't fixed in 1.0.5-1. If I'm not misreading the Ubuntu CVE page, all Ubuntu versions seem to ship a vulnerable nginx.   Is this true?  If so: I thought there was a security team at Canonical that's actively working on issues like this, so I expected to get a security update within a short timeframe (hours or days) through apt-get update. Is this expectation -- that keeping my packages up-to-date is enough to stop my server from having known vulnerabilities -- generally wrong? If so: What should I do to keep it secure? Reading the  wouldn't have helped in this case, as the nginx vulnerability was never posted there.


I am new to Latex (technically not "new" - I got my interest from the Maths Stack Exchange, where I absorbed some Latex typesetting skills for maths). Hopefully, this type of question is allowed on this SE: basically, where do I start? I initially thought Latex was primarily for scientific typesetting for maths and chemistry etc only. ie recursive fractions, square roots, chemical equations which are impossible to typeset without using the "\blahblah" command. But I really like the aesthetic and simplicity of Latex documents which I have seen in thesis and papers. I am actually very confused as to how this whole thing works - but hopefully there is a guide somewhere? I thought that there would be an app to make Latex documents like you do in Word but it seems that there are so many different downloads and extensions you have to get. Additionally, it seems very complex and overkill to write stuff like \startdocument, put an "&" sign whenever you want a new sentence, and especially tables get very complex when Word does it instantly. Is it designed for everyday use? I am a school student but it would be nice to do homework in Latex (it seems only formal documents are in Latex, however). I have a mac and am just using the online Overleaf, but why are there so many more online website to do the same thing? (sorry I am not sure what tag to use)

What editors/IDEs are available for easing the process of writing TeX/LaTeX documents? Please state some useful features like code completion, spell checking, building final DVI or PDF files, etc.  This question is undergoing a systematic refurbishment, see  on Meta. If you’d like to see another editor feature covered here or to take care of an editor that’s not covered yet, share your ideas in that meta question.  List of editors Links to answers.


In practice we sometimes used a wisdom that two overlapping CIs for sample mean distribution meant we could not reject Hull hypothesis, to get a quick answer.  It looks though that this is a very raw estimate. I was working on a toy example of a two-sample hypothesis testing when I realized that our "wisdom" was just incorrect.  Am I right?    When I took the difference of samples X and Y, and plotted its moments, apparently the p-value is quite low.       α = 0.01; one-sided test; n(X) = n(Y) = 1000; var(X) = var(Y) = 1.   > t.test(x = xy[sample == 'x', x], y = xy[sample == 'y', x], +        alternative = "less", +        mu = 0, paired = F, var.equal = T)      Two Sample t-test  data:  xy[sample == "x", x] and xy[sample == "y", x] t = -2.7023, df = 1998, p-value = 0.003472 alternative hypothesis: true difference in means is less than 0 95 percent confidence interval:         -Inf -0.04665049 sample estimates:  mean of x  mean of y  0.02546606 0.14476431

It is well known that confidence intervals and testing statistical hypothesis are strongly related. My questions is focused on comparison of means for two groups based on a numerical variable. Let's assume that such hypothesis is tested using t-test. On the other side, one can compute confidence intervals for means of both groups. Is there any relation between overlapping of confidence intervals and the rejection of the null hypothesis that means are equal (in favor of the alternative that means differ - two-sided test)? For example, a test could reject the null hypothesis iff the confidence intervals do not overlap.


If a holomorphic on the whole complex plane funtion $f$ has a bounded real part then it is constant.  Could I use here Cauchy-Riemann equations here? They seem to lead me nowhere.

Greets  This is exercise 15.d chapter 3 of Stein & Shakarchi's "Complex Analysis", they hint: "Use the maximum modulus principle", but I didn't see how to do the exercise with this hint rightaway, instead I knew how to do it with the Casorati-Weiestrass Theorem, here is my answer:  Define $g(z)=f(1/z)$ for $z\neq{0}$,then by the hypothesis we must have that for any $\epsilon>0$ $g(D_{\epsilon>0}(0)-\{0\})$ is not dense in $\mathbb{C}$, then the singularity at $0$ of $g$ is not essential, this implies $f$ must be a polynomial, but if $f$ is a non-constant polynomial, it is easy to see that its real part must be unbounded, so $f$ must be constant.  I would like to know an answer with the the maximum modulus principle.  Thanks


This is the context:  'The 21h00 draw features two Suzuki Ignis up for grabs.'  I don't know whether it's Ignis', Ignis's or just Ignis  Thank you.

With a name that ends in -s, such as Travis or Lewis, where and when should you use -es, -'s, -s or just leave it alone to both pluralise, and to infer belonging to?  E.g., if the ball belongs to Travis, which suffix would be used in      The ball is Travis[es/'s/s/].   And, referring to a group of people all named Travis, which is correct:     Here come the Travis[es/'s/s/].


Suppose a, b, c  are positive real numbers such that    $$(1+a+b+c)\left(1+\frac 1a+\frac 1b+\frac 1c\right)=16$$  Then is it true that  we must have  $a+b+c=3$ ?  Please help me to solve this. Thanks in advance.

Let $a,b,c\in \Bbb R^+$ such that $(1+a+b+c)(1+\frac{1}{a}+\frac{1}{b}+\frac{1}{c})=16$.  Find $(a+b+c)$.  I computed the whole product ;If  $(a+b+c)=x\implies (1+x)(1+\frac{bc+ca+ab}{abc})=16$. Unable to view how to proceed further.  Please help.


How can I prove this? I was thinking of using strong induction on $n$, and I've managed to prove the base case using induction again on $a$,  $$2^3 \mid a^{2} - 1$$  but I couldn't work my way around the rest of the proof with the usual properties of divisibility (if $m \mid n$, then $a^m - 1 \mid a^n - 1$, etc).

Prove that:  $$a^{2^n} \equiv 1\pmod{2^{n+2}}$$  I have done the base case, and then have an assumption that:  $$a^{2^k} \equiv 1 \pmod {2^{k+2}}$$  I wish to prove the last step, that:  $$a^{2^{k+1}} \equiv 1 \pmod{2^{k+3}}$$  How would I do this?


So my regression model is able to fit the training data. However, the test data never decreases. It starts increasing as soon as the model is learning (first epoch). Meanwhile, the training loss keeps decreasing. I pretty much tried everything I've found on the internet and the problem remains.  What I tried so far:  Created the dataset with the same distribution and then split it into train and test. Changed all tuning parameters including activation function, batch-size, hidden layers, etc. Reduced model complexity Used Layer normalization, standardization etc. Added more data Shuffled the data Added regularization with different weight decays    and yet nothing appears to solve the problem. What could I do besides this?

I'm training a neural network and the training loss decreases, but the validation loss doesn't, or it decreases much less than what I would expect, based on references or experiments with very similar architectures and data. How can I fix this?    As for question        to which this question is inspired, the question is intentionally left general so that other questions about how to reduce the generalization error of a neural network down to a level which has been proved to be attainable, can be closed as duplicates of this one.  See also dedicated thread on Meta:


The Bajoran/Federation outpost Deep Space Nine has several Federation runabout vessels assigned to it. One of them, either the Ganges or the Rio Grande, can occasionally be seen with a device attached to the top of the vessel. Here is a screenshot showing the runabout in question beside another one without the device:    Does anyone know what this device is or why only one runabout has it?

The runabouts in Deep Space Nine sometimes have additional equipment on their backs; this is a screenshot from S02E15 (Paradise), showing the Orinoco in the background with the unknown equipment & the Rio Grande in the foreground with a clean configuration:  What is the equipment & why is it only sometimes present?


If I have a Poisson regression such that $\lambda = \alpha + \beta t$, $\alpha + \beta t \geq 0$ $\forall t, \alpha, \beta$ and $Y_t \sim \textrm{Poisson}(\lambda_t)$ for which I have 10 observations from $t=0$ to $t=9$ then the likelihood is:  $$\prod_{t=0}^9 \left\{\frac{(\alpha+\beta t)^{y_t}}{y_t!}e^{-(\alpha+\beta t)} I_{\alpha+\beta t} \geq 0\right\}$$  If I set the prior to be proportional to 1, then the likelihood is proportional to the posterior, so mathematically the expressions for deriving the MLE of $(\alpha, \beta)$ and the posterior distribution are the same.   However, are the sufficient statistics the same? I know that sufficient statistics for $(\alpha, \beta)$ with regards to obtaining the MLE in the linear model are:  $$\sum_{t=0}^9 y_t\ \text{ and }\ \sum_{t=0}^9 y_tt$$ for $\alpha$ and $\beta$, respectively (which I also have trouble seeing). But does this also apply for the posterior distribution?

The title pretty much says it all. I wonder whether there is any difference in the way Bayesians understand sufficiency vs. the way orthodox statistics understands sufficiency, or are they equivalent?  If there is a difference, what is it?


I run om-my-zsh and my prompt usually says      gregg@Gumby $    where Gumby is the name of my Mac.  Today it said       gregg@Michaels-iPhone $    I was not connected to any iPhone. All sharing features in system preferences sharing are off.  what is going on?

My computer name in System Preferences > Sharing is set to "archos", but is showing as "iphone" on Terminal. It just started doing this after I loaded Xcode for doing iPhone development: Last login: Mon Nov  7 14:46:55 on ttys001 iphone:~ travis$   Any ideas what could be causing this?


Compute the volume of $$ S_n=\{(x_1,x_2,...,x_n)\in\mathbb{R^n},x_i\geq 0,\displaystyle\sum_{k=0}^{n} x_i<1\} $$  I don't really have an idea how to solve it.  My 'work': Perhaps I could use  $$ ||x||_1=|x_1|+...+|x_n| $$ So the set is  $$ S_n=\{(x_1,x_2,...,x_n)\in\mathbb{R^n},x_i\geq 0,B(0,1)\} $$ Where $$ B(0,1)=\left\{M\in\mathbb{R^n} \,\mid\,d(M,0)<1\right\} $$ But I don't see where it leads me...  Thank you in advance

It's rather tedious to show using Fubini's Theorem and induction on $n$ that the volume of the region $x_1+x_2+...+x_n \leq 1$ with $x_1,...,x_n$ nonnegative is $\frac{1}{n!}$.  Is there an easier way to see this?


Looking for an equivalent svn command to the selective adding and committing in git:  git add --patch

Given the case I made two independent changes in one file: eg. added a new method and changed another method.  I often don't want to commit both changes as one commit, but as two independent commits.  On a git repository I would use the Interactive Mode of  to split the hunk into smaller ones:   git add --patch   What's the easiest way to do this with Subversion? (Maybe even using an Eclipse plug-in)  Update: In , Ryan calls it: “The Tangled Working Copy Problem.”


So When I logged into roblox I have put my age as ‘9’ and I am 14 years old. My username is poodles_246 and I would really like for roblox to try and change my age to 14 because it would really help out. Thanks

How do you set your age settings on ROBLOX if you accidentally set to under 13? I accidentally put 2008 instead of 1998 in the sign up section. Is there any way to change this, as in settings, age settings are greyed out.


Let $\phi(t) = \phi_1(t)+i\phi_2(t)$ be a complex function in a real interval $t$  In order to prove: $$\left|\int_a^b \phi(t) \ dt \right|\le \int_a^b |\phi(t)| \ dt$$  I tried: $$\int_a^b \phi(t) \ dt  = \int_a^b \phi_1(t) + i\phi_2(t) \ dt  = \int_a^b \phi_1(t) \ dt + \int_a^b \phi_2(t) \ dt \rightarrow$$  $$\left|\int_a^b \phi(t) \ dt \right| = \sqrt{\left(\int_a^b \phi_1(t) \ dt\right)^2+\left(\int_a^b \phi_2(t) \ dt\right)^2}\le \sqrt{\left(\int_a^b \phi_1(t) \ dt\right)^2}+\sqrt{\left(\int_a^b \phi_2(t) \ dt\right)^2} = $$  $$\left|\int_a^b \phi_1(t) \ dt\right|+\left|\int_a^b \phi_2(t) \ dt\right|\le \int_ a^b |\phi_1(t)| \ dt + \int_a^b |\phi_2(t)| \ dt = \int_a^b |\phi_1(t)|+|\phi_2(t)| \ dt$$  But how to arrive at $\int_a^b |\phi(t)| \ dt$?

I've been given a proof that shows the following:  If $f:[a,b]\to \mathbb C$ is a continuous function and $f(t)=u(t)+iv(t)$ then $$\left| \int_a^b f(t) dt \right| \leq \int_a^b \left| f(t) \right| dt$$ The proof begins by letting $\theta$ be the principle argument of the complex number $\int_a^b f(t)dt$ and there is one step in the proof I don't understand; can anyone explain to me why $$\int_a^b e^{-i\theta}f(t) dt=\Re\bigg(\int_a^be^{-i\theta}f(t)dt\bigg)$$  Would this not imply that the imaginary part of the left hand side is equal to $0$? I'm not sure why the LHS and RHS would be equal here.


Youtube videos do not play. Instead, the following messages appear: "This plugin is vulnerable and should be updated", "Activate Adobe Flash", "Check for updates." Since my version is 14.04LTS, the Adobe Flash Player cannot be installed. What should I do for playing Youtube videos. The browser I use is Firefox.

I have had significant problems with watching flash video in 64-bit Ubuntu.  Does anyone know of a good way to get flash running on the platform?


Is this a bug in jvm the code bellow gives the result : 409.99999999999994 !  public class HelloWorld{      public static void main(String []args){           double d = 4.10d;           double d2 = d * 100d ;           System.out.println(d2);      }  }   changing double by float solves the problem, but why?

double r = 11.631; double theta = 21.4;   In the debugger, these are shown as 11.631000000000000 and 21.399999618530273.  How can I avoid this?


In Topological Solitons by Nicholas Manton where he considers "compact Lie groups" to be the gauge groups  for generalizing gauge theoretic concepts. But, he does not mention why that condition is required  The killing is non-degenerate as per the requirement of the kinetic terms.Kinetic part of the Yang Mills action $$ \int Tr({\bf{F^2}}) dV$$ to be positive definite. I do think there is relevancy of the compactness of the lie group as apposed to the views in   I've found this result.      For compact groups the Killing form will be negative definite   I'm not able to find any such result for a Lie group. Can anyone tell me how this and the above result are result and its implementation in gauge theory?  Thanks, Sai

What is the motivation for including the compactness and semi-simplicity assumptions on the groups that one gauges to obtain Yang-Mills theories?  I'd think that these hypotheses lead to physically "nice" theories in some way, but I've never, even from a computational perspective. really given these assumptions much thought.


I'm trying to make a map with a death-checker. I'm not a command pro, so I used MCStacker to generate a command. The below command is a function that I generated: give @p chain_command_block{display:{Name:'{"text":"Consequence block","color":"blue","bold":true}'},Enchantments:[{}],BlockEntityTag:{Command:"execute if score @p Deaths matches 10 run title @p title {"text":"this is a test","color":"#6BFF93","bold":true}",auto:1b}} 1  This will give me a command block, which will check if I'm at 10 deaths and if so, will execute a title. But for some reason it doesn't work. Instead, the command generator wants me to make the code like this: run title @p title {"}} 1  But if I do that, my command doesn't work anymore. I've been stuck with it for a few hours now. How can I get this command to work? I'd prefer solutions that fix the issue in MCStacker so I can regenerate the command. My screen with the commands:  The error in Minecraft log:

I need help with a specific command that I am using in a new game that I am creating inside of Minecraft. The command is:  /give @p sign 1 0 {BlockEntityTag:{Text1:"{"text":" [MF2]","color":"gold","clickEvent": {"action":"run_command","value":"tellraw @a [""{"text":"[MF2]  ","color":"gold"},{"selector":"@p","color":"dark_aqua"},{"text":" is now an admin of the server!","color":"white"}]"}}",Text3:"{"text":"Click to join Admin","color":"dark_aqua","clickEvent": {"action":"run_command","value":"scoreboard teams join admin @p"}}"},display: {Name:"Custom Sign"}}   If I take out the /tellraw command then the command works fine, but I need the command in there to announce to the game that a new admin has joined.  With the tellraw command, the error message is the following:  Data tag parsing failed: Unexpected token 't' at: text":" [MF2]","color":"gold","clickEvent":{"action":"run_command","value":"tellraw @a [""{"text":"[MF2] ","color":"gold"}, {"selector":"@p","color":"dark_aqua"},{"text":" is now an admin  of the server!","color":"white"}]"}}",Text3:"{"text":"Click to join Admin","color":"dark_aqua","clickEvent": {"action":"run_command","value":"scoreboard teams join admin @p"}}"   If anyone knows how to fix this, please let me know.


As the title says, I am looking for source code that shows how to read(write) MS Excel files in pure C (OS agnostic). I have seen some Java code (e.g. JExcel) and would use that if I can't find some existing C code with similar functionality.  What I need is to read an Excel file and convert it to XML (or some other more manageable format).  TIA

Well... that's it.   I need something simple and reliable (doesn't have to have fancy features - I need to write and read text and numbers from Excel cells)  And yes, I would like a sample "Hello Cell" code...  What do you recommend?


Prove that $1 + nx ≤ (1 + x)^n$ , for all real numbers $x > −1$ and integers $n ≥ 2$ by mathematical induction.  My attempt (1) $n=2$ $x > -1 \Rightarrow (1+2x > -1) \land (x^2 \ge 0)   \Leftrightarrow (1+2x) \le (1+x)^2 $ Hence p(2) is true.  (2) We must show that for all integers $k \ge 2, p(k) \Rightarrow p(k+1)$   Suppose for inductive hypothesis, $k \ge 2, p(k)$. That is $1 + kx ≤ (1 + x)^k$ Then, $1 + kx + x = 1 + (k+1)x ≤ (1 + x)^k + x$    I should get $1 + (k+1)x ≤ (1 + x)^{k +1} $. It seems when I multiply each side by (1+x), the left side gets complex and far away from desired inequlity. On the other hand, when I add 1, it doesn't help since we have to get $(1+x)^{k+1}$ on the right side, $(1 + x)^k + x+1$ doesn't increase the exponent of $(1+x)$.  What should I do next to get out of $1 + kx + x = 1 + (k+1)x ≤ (1 + x)^k + x$?   $1 + kx + x = 1 + (k+1)x ≤ (1 + x)^k$

I'm asked to used induction to prove Bernoulli's Inequality: If $1+x>0$, then $(1+x)^n\geq 1+nx$ for all $n\in\mathbb{N}$. This what I have so far:  Let $n=1$. Then $1+x\geq 1+x$. This is true. Now assume that the proposed inequality holds for some arbitrary $k$, namely that $$1+x>0\implies (1+x)^k\geq 1+kx,~\forall~k\in\mathbb{N}\setminus\{1\}$$ is true. We want to show that the proposed inequality holds for $k+1$. Thus multiplication of $(1+x)$ on each side of the above inequality produces the following result: $$(1+x)(1+x)^k\geq (1+kx)(1+x)\implies (1+x)^{k+1}\geq 1+x+kx+kx^2\cdots\cdots\cdots$$  I'm not sure where to go from here.


In my understanding, $64^{\frac23}$ can be defined as $(64^{\frac13})^2=4^2=16.$ How can I define $64^x$ when $x$ is real?

We all know that $2^5$ means $2\times 2\times 2\times 2\times 2 = 32$, but what does $2^\pi$ mean? How is it possible to calculate that without using a calculator? I am really curious about this, so please let me know what you think.


<?php   $pattern = "/http:\\/\\/(([A-Za-z0-9.\-])*)/";   $text = "http://www.google.com";   $text = preg_replace($pattern,"\\0",$text);   echo $text;  ?>   The code above gets the URL from a string variable and adds an HTML tag           for a link. So "http://www.google.com" becomes "http://www.google.com".  My question is how "\0" is something like placeholder for the value of the parameter "$text" in the "preg_repace" function, after it means NULL or 0x0?

I am trying to grab the capital letters of a couple of words and wrap them in span tags. I am using  for extract and wrapping purposes, but it's not outputting anything.  preg_replace("/[A-Z]/", "$1", $str)


Find all real solutions for the system:   $$x+\frac{1}{y}=y+\frac{1}{z}=z+\frac{1}{x}$$    given that $xyz=1$.   This is from a math olympiad (OBM 2009).   By inspection it is easy to spot that a possible solution is $x=y=z=1$ but are there others? It looks like it is not a difficult question but I'm not finding a nice approach.   Hints and solutions are appreciated. Sorry if this is a duplicate.  Edit 1: Pointed out by helpful comments below,  presents a complete solution for this problem, for all possible cases. From that mentioned answer we can conclude that when $xyz=1$ there are two possible solutions:  $$(x,y,z)=(1,1,1)~~\text{and}~~(x,y,z)=(a,\frac{-1}{a+1},\frac{-(a+1)}{a}),\forall a \in \mathbb R\setminus\{0;-1\}.$$  Answers using other techniques or arguments are welcomed.

If $x,y,z$ are distinct positive numbers, such that $$x + \frac1y = y + \frac1z = z + \frac1x $$ then value of $xyz$ is?  $$A)\ 4\quad  B)\ 3\quad C)\ 2\quad  D)\ 1$$  My attempt:  1.I equaled the equation to '$k$'. Using the AM-GM inequality, I found that $k>2$ (the equality does not hold because all are distinct). However, this, I couldn't put to much use. 2. For the next attempt, I substituted the values of $x$ and $y$ in terms of $z$ and $k$ in $xyz$. What I am getting is $xyz=zk^2 - k - z$. That's the farthest I could do..Please, help.


Sorry in advance for the newbie question, but I can't seem to find a good answer. Recently, I've gotten into printed circuit boards and it is all still fairly new. I'm working towards creating a 4 layer pcb and I'm curious common practice for layer stack up. I've seen some places that use the outer layers as signal layers and internal two layers as GND and VCC and vice versa other places.  Is there any  stack up for a four layer board (or any amount of layers for that matter) that is particularity advantageous?   Also from previous research it seems that having both a GND and VCC plane creates a small amount of capacitance, why is this useful?

I'm designing a 4 layer PCB and I know that the standard stack-up is  Signals GND VCC Singals  (GND and VCC can be switched depending on the layer with more signals) The problem is, I don't really want to connect all ground pins through vias, there are just too many of them ! maybe because I'm not used to 4 layer PCBs, anyway, I've read a  by Henry W. Ott about a different stack-up  GND Signals Signals GND  (Where the power is being routed with wide traces on the signal planes) According to him, this is the best stack-up possible with a four-layer PCB, for the following reasons: 1.Signal layers are adjacent to ground planes. 2.Signal layers are tightly coupled (close) to their adjacent planes. 3.The ground planes can act as shields for the inner signal layers. (I think this requires stitching ??) 4.Multiple ground planes lower the ground (reference plane) impedance of the board and reduce the common-mode radiation. (don't really understand this one) One problem is cross-talk, but I really don't have any signals in the third layer, so I don't think that corss-talk will be an issue with this stack-up,am I correct in my assumption ? Note: The highest frequency is 48MHz, there's a wifi module on the board too.


There is an explanation of how a battery works that says that inside the battery (in the positive charge convention) there is a field and the battery does work on the positive charge against the field to move it from the negative terminal to the positive terminal and it becomes full of potential energy, ready to be used in a circuit.  But from what I understand from a battery (an excess of electrons on one side and a lack of electrons on the other side) there isn't a field inside the battery and the battery doesn't take a charge and move it from one side to the other so it gains potential energy.  What I need is a chemical detailed explanation of how a battery works that tells more about how the battery's electric field is created.

I would like to know why does electrons flow through a wire connected to a battery as said in .It tells that "the electrons that are stripped from the carbon electrode is collected on the zinc can" and then tells     The electrons at the negative terminal want to go to positive terminal, they just need a way to get there. In our light bulb circuit, the way to get there is through the wire.   Why couldn't the electrons go to the positive terminal through the electrolyte(potassium hydroxide) instead of going through the wire?


I am travelling from Ukraine to Serbia, transfer via Vienna airport? Do I need transit visa in this case?

I found many related questions on this site but I am still not sure about the rules. How can I decide if I need a visa to transit? Schengen members as of May 2021 are as follows:  Austria Belgium Czech Republic Denmark (excluding Greenland and the Faroe Islands - but an open border with the Schengen Area is maintained) Estonia Finland France (excluding overseas departments and collectivities) Germany Greece Hungary Iceland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands (excluding Aruba, Curaçao, Sint Maarten and the Caribbean Netherlands) Norway (excluding Svalbard) Poland Portugal Slovakia Slovenia Spain (except Ceuta and Melilla) Sweden Switzerland


Here's code of Splash Screen (it's not my desire, but client) - the only thing I've done - just to replace sone code with loading data to this activity:  public class SplashActivity extends AppCompatActivity {  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);      Retrofit retrofit = new Retrofit.Builder()             .baseUrl(Constants.API_URL)             .addConverterFactory(GsonConverterFactory.create())             .build();      GetAll getAllProducts = retrofit.create(GetAll.class);     Call<ArrayList<Products>> call = getAllProducts.getAll(Constants.PARTNER_ID,             WaterFragment.getMD5Hash(Constants.PARTNER_ID + Constants.API_KEY));     call.enqueue(new Callback<ArrayList<Products>>() {         @Override         public void onResponse(Response<ArrayList<Products>> response, Retrofit retrofit) {             if (response.body() != null) {                 ActiveAndroid.beginTransaction();                 try {                     ProductsDMC product;                     for (Products p : response.body()) {                         if (new Select().from(ProductsDMC.class).where("product_id = ?", p.id).executeSingle() != null) {                             product = new Select().from(ProductsDMC.class).where("product_id = ?", p.id).executeSingle();                             product.price = p.price;                         } else {                             product = new ProductsDMC(p.id, p.article, p.title, p.price, p.amount, p.category_id,                                     p.brand_id, p.description, p.photo[0], p.option != null ? p.option.bottle_price : "0");                         }                         product.save();                     }                     ActiveAndroid.setTransactionSuccessful();                 } finally {                     ActiveAndroid.endTransaction();                 }             }else{                 Toast.makeText(SplashActivity.this, "Try later!", Toast.LENGTH_SHORT).show();             }         }         @Override         public void onFailure (Throwable t){             Toast.makeText(SplashActivity.this, "Check your connection!", Toast.LENGTH_SHORT).show();             Log.d("LoloPolo", t.getMessage().toString());         }     });     Intent intent = new Intent(this, ListOrdersActivity.class);     startActivity(intent);     finish(); } }   Tonight my crashlytic send info about crash on app:  Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference    at ru.luny.aqualuxe.activity.SplashActivity$3.onFailure(SplashActivity.java:142)    at retrofit.ExecutorCallAdapterFactory$ExecutorCallback$2.run(ExecutorCallAdapterFactory.java:94)    at android.os.Handler.handleCallback(Handler.java:739)    at android.os.Handler.dispatchMessage(Handler.java:95)    at android.os.Looper.loop(Looper.java:145)    at android.app.ActivityThread.main(ActivityThread.java:5832)    at java.lang.reflect.Method.invoke(Method.java)   It's about this:  Toast.makeText(SplashActivity.this, "Try later!", Toast.LENGTH_SHORT).show();   I really don't understand - how Toast.makeText().show can cause NPE))  Could you help me please?  EDIT  It seems strange but crashlytics shows me wrong place of error code string. It's not about toast but debug-loggin with getting message from exception.

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?


What is a good package for taking note of draft ideas, and have them emphasized in the output document? For example:  This is a very brilliant idea for a  research topic \somecommandthathighlightsanotetoself{(Try to find out exactly why this is a brilliant idea.)}   In the output document, I would like to see the note in red or any other color to call out my attention as I review my work. As a bonus, perhaps some note in the margins for additional attention-calling.

Is there a simple way to add todo notes to LaTeX documents ?  I would like to have these notes in red in the generated pdf and a simple syntax to write them.


How can we explain spin of electron, or the spin of other fundamental particles?  If we think the spin of electron is similar to the spin of a ball or planet we make a mistake.  We say it is an intrinsic property. However, in calculating magnetic momenta and other cases we consider it as spinning entity. It's too difficult to abandon the model which we see. Without which to explain abstract one becomes challenging.

I often hear about subatomic particles having a property called "spin" but also that it doesn't actually relate to spinning about an axis like you would think. Which particles have spin? What does spin mean if not an actual spinning motion?


bash builtin command read  is said to accept input from stdin, but why does the following not read in anything?  $ printf "%s" "a   b" | read line $ printf "%s" "$line" $   Thanks.

With ksh I'm using read as a convenient way to separate values: $ echo 1 2 3 4 5 | read a b dump $ echo $b $a  2 1 $  But it fails in Bash: $ echo 1 2 3 4 5 | read a b dump $ echo $b $a     $  I didn't find a reason in the man page why it fails, any idea?


I am trying to read in a file using read in bash 3.2, but read seems to be converting any instance of multiple whitespace into a single space.  For example, the code below has two tabs between "hello" and "there", and three spaces between "today" and "world":  while read -r LINE; do     echo $LINE done <<< "hello     there today   world"   However, when run, it outputs with only a space in between each set of words:  hello there today world   Instead, I'd like it to output the lines with whitespace preserved, e.g.:  hello       there today   world   Is there any way to do this? If not with read, then with something else?

Or, an introductory guide to robust filename handling and other string passing in shell scripts.  I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some file names).  I encountered a problem such as the following:   I have a file name containing a space hello world, and it was treated as two separate files hello and world. I have an input line with two consecutive spaces and they shrank to one in the input. Leading and trailing whitespace disappears from input lines. Sometimes, when the input contains one of the characters \[*?, they are replaced by some text which is is actually the name of files. There is an apostrophe ' (or a double quote ") in the input and things got weird after that point. There is a backslash in the input (or: I am using Cygwin and some of my file names have Windows-style \ separators).   What is going on and how do I fix it?


In Perl, if I want to execute a shell command such as foo, I'll do this:   #!/usr/bin/perl $stdout = `foo`   In Python I found this very complex solution:   #!/usr/bin/python import subprocess p = subprocess.Popen('foo', shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT) stdout = p.stdout.readlines() retval = p.wait()   Is there any better solution ?   Notice that I don't want to use call or os.system. I would like to place stdout on a variable

How do you call an external command (as if I'd typed it at the Unix shell or Windows command prompt) from within a Python script?


When I create multiple users in ubuntu it's much more convienient. In ubuntu, we get seperate hard drives management for all users created. One user cannot access the files of the other user, unless s/he is  the superuser. But, in windows, it seems like all  the files are accessible, only the desktop is cleared up and the programs are defaulted. It's not really convienient if other users created can access your files.      This is the case now for me, I have created a new user,  and password protected my account, but, say my brother accesses  my PC,  and signs in into  the account  created for him, then he accesses my files in D: from his account.      Is this  really the case  with windows,  or is it that I'm missing  something that  can be customized? Or if it is how to get the behaviour like ubuntu? I'm currently using windows 8.1.

I have extra internal and external hard drives in my computer.  One I use to keep some unused files, and the other I use for backup of my C: drive.  How can I limit anyone that uses my pc under the guest account to even be able to see this HDD?  Furthermore, I actually would like to give guest access to a media folder in one of the hard drives, so I would like to know:   Can I hide a drive from a guest user? How? Can I only make folders unavailable (not hide them) and still share a folder? How?


I'm a mathematics student in my junior year and I'm interested in computational complexity and specially geometric complexity theory. I'm going to learn algebraic geometry and representation theory but I want to consider the parts that are related to geometric complexity theory so I wonder What are the topics that should be mastered by someone who wants to understand geometric computational complexity?  Surely, a lot of algebraic geometry and representation theory are needed, but which topics? and representation theory of what? finite groups? lie algebras(probably not) etc? and which topics in algebraic geometry are needed? It would be great if it is possible to name some topics that are required to be well understood in algebraic geometry and representation theory to before tackling  geometric  complexity theory. naming good resources ( texts etc ) that cover this background will be highly appreciated too.  I have asked the same question on math stackexchange but got no answer, so I thought I should ask it here.

It seems that Geometric Complexity Theory requires much knowledge of pure maths such as algebraic geometry, representation theory.   While I am a CS student and do NOT have classes of very abstract and pure mathematics, I am interested in this program.  Is there a list of "minimum knowledge" for learning this theory ?     This list includes lecture notes of CS or math departments, surveys of any journal or conferences, and text books of pure math.  [EDIT: Added later] Thank you for your comments.  General theory of computing: I read Sipser's book with the title "Introduction to the Theory of Computation"  Complexity Theory :In particular, I am interested in concrete models for lower bounds of complexity. Thus I read the part of the "concrete lower bounds" in Arora-Barak's text book. I also have basic knowlede in the several chapers of the communication complexity book written by Nisan.  Basic Mathematics : I have learnt about proof-based linear algebra such as general definition of the vector space etc and precicely argument of calculas based on epsilon-delta argument.   Algebra: I have learned about definition and examples of group, ring, and field. I had a class for cs students, and have not learned about general thoery of this algebraic systems.


Hello everybody ~ I am fresh off the newbie tree and waving good bye to Windows through the rear view mirror.   I just started up an old machine that has a fresh install of 8.10 on it and has never been used since.    As far as I can tell there is no gui desktop on it.  I would like to update it to the latest, 14.x?   How do I update?  Do I just over write the 8.10 with the latest?  do I wipe the 8.10 first then install?  Can anyone please advise on this?  Many thanks.

Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc


Would a PC with no or limited ability to speak (like a character born deaf or mute) be able to use spells with Verbal components?

A Kenku can only speak by mimicry, so can a Kenku fulfill the verbal portion of spells of his class? I would assume that he could only cast a verbal spell if he has heard the spell be cast by another caster of his same class. Also, the other caster would have to have cast the spell in a way that the Kenku knew what was spoken and why.


I went to the self-advertized pstricks web site,     and tried to run a few examples in TeXShop version 3.51 on Mac OSX Yosemite.  The examples I tried are cycloid.tex, game0.tex, and curve0.tex.  These appear to be self-contained, syntactically complete examples, but they all fail with similar error messages  ! Undefined control sequence. <recently read> \c@lor@to@ps  l.82      dAngle=90,nAngle=4](0,0)(0,360){1}{1}{1}   suggesting that \c@lor@to@ps is not defined properly somewhere in the pstricks stack. I thought rather than go down the rabbit hole of trying to debug this, I'd ask the community, because it appears that something systematic and cosmic is wrong, either with the distribution of pstricks in TeXShop / MacTeX / TeXlive, or perhaps pstricks is just dead, being replaced by Tikz?  I don't know.  BTW, fails with the same kinds of error messages at the console with pdflatex  pdfTeX 3.14159265-2.6-1.40.15 (TeX Live 2014) kpathsea version 6.2.0 Compiled with libpng 1.6.10; using libpng 1.6.10 Compiled with zlib 1.2.8; using zlib 1.2.8 Compiled with xpdf version 3.03


In many cases, we have to make a special attention to specific part of code, and Arrows are great way for that. Is it possible, that CharMap (or at least several SpecialSymbols were added into post EDITOR (for Superuser, Stackoverflow and several other coding SO sites)? so, we can quickly insert those symbols/arrows into answer.    (Btw, or there could be a way to mark the part of code which should cause more attention to it... i.e. making the color of the word RED and BOLDED)  p.s. why you thought that i am including them in questions? I said while Answering to questions, it is usable for. So, it's not me who uses these chars, but any of answer-er.

It would be nice to be able to put emphasis on specific bits of a fragment or of a quote (bold can help for a quote but I find that it makes things less readable sometimes). What do you think? Update: On , you can highlight particular lines by prefixing each line with @@. See also:


I was trying to make a simple Spreadsheet java app. For this I am using JTable in swing. My code is as follows:  import javax.swing.*; import java.awt.*;  public class Main {      private JFrame Frame;     public Font f = new Font("Candara", Font.PLAIN, 14);     public JFileChooser choicer = new JFileChooser();     public String dir;     private JTable Table;     public String[] columns;     public String[][] data = new String[10][2];     public static Main m = new Main();      /**      * Launch the application.      */     public static void main(String[] args) {         EventQueue.invokeLater(new Runnable() {             public void run() {                 try {                     m.Frame.setVisible(true);                 } catch (Exception e) {                     e.printStackTrace();                 }             }         });     }      /**      * Create the application.      */     public Main() {         initialize();     }      /**      * Initialize the contents of the frame.      */     private void initialize() {         Frame = new JFrame();         Frame.setTitle("Spreadsheet");         Frame.setBounds(100, 100, 1000, 800);         Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);          JMenuBar menuBar = new JMenuBar();         Frame.setJMenuBar(menuBar);          JMenu File_Menu = new JMenu("File");         File_Menu.setFont(f);         menuBar.add(File_Menu);          JMenuItem New_Doc = new JMenuItem("New Document");         New_Doc.setFont(f);         New_Doc.addActionListener(e -> {             choicer.setCurrentDirectory(new java.io.File("."));             choicer.setDialogTitle("New Document");             choicer.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);             choicer.setAcceptAllFileFilterUsed(false);              if (choicer.showOpenDialog(new JPanel()) == JFileChooser.APPROVE_OPTION) {                 dir = String.valueOf(choicer.getCurrentDirectory());             }         });         File_Menu.add(New_Doc);          JMenuItem Save_Doc = new JMenuItem("Save Document");         Save_Doc.setFont(f);         File_Menu.add(Save_Doc);          JMenuItem Open_Doc = new JMenuItem("Open Document");         Open_Doc.setFont(f);         File_Menu.add(Open_Doc);         Frame.getContentPane().setLayout(null);          m.newTable();         Table = new JTable(data, columns);         Table.setBounds(10, 11, 964, 718);         Table.setFillsViewportHeight(false);         Frame.getContentPane().add(Table);         Table.setDragEnabled(false);      }      public void newTable() {         int i = 1;         columns = new String[10];         while (i <= 10) {             columns[i - 1] = String.valueOf(i);         }          i = 0;         int j = 0;         while (i < 10) {             while (j < 2) {                 data[i][j] = String.valueOf(i + j);             }         }      }  }   When I run this code, I get the following message:       Exception in thread "main" java.lang.ExceptionInInitializerError   Caused by: java.lang.NullPointerException     at Main.initialize(Main.java:76) (this line is: m.newTable();)     at Main.(Main.java:34)     at Main.(Main.java:13)     Why does this happen?  Additionally, is there something wrong in the way in which I'm setting the bounds for the Table?

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 trying to use a very jury-rigged (and probably totally irreproducible, sorry) build process to get my moderncv cv to build on Netlify.  Netlify doesn't officially support tex builds, but someone  using a complicated bash script that does a minimal installation of texlive and then uses texliveonfly to fetch packages.  This process is failing largely because it can't get ahold of something called l3regex.sty  But this is the mysterious part. See, I've edited the script in that repository to add a bunch of tlmgr commands in order to get the stuff that my build keeps failing on.  Right now, I have:   tlmgr update -self -all tlmgr install l3packages tlmgr install etoolbox tlmgr install xcolor tlmgr install microtype tlmgr install l3kernel tlmgr install xpackages tlmgr install regexpatch   , l3regex is part of l3kernel.  But when I try to install l3kernel, I get:   tlmgr install: package already present: l3kernel  yet when it actually tries to build, it still throws an error Latexmk: Missing input file: 'l3regex.sty'  There's also a SO from about a year ago .  So, I tried to install that too, but it said tlmgr install: package expl3 not present in repository, which I guess makes sense, because .  But I've got l3kernel installed!  So why can't tex find l3regex?    And is there just somewhere that I can straight-up download l3regex.sty to put it on the search path and have done with it, rather than fight with package management for days?

I updated my MiKTeX today. Now, I do not get any error without packages but it can not compile my latex files with packages.  Uninstalling and reinstalling both Texmaker and Miktex did not work. I could not find l3regex.sty file on internet.     LaTeX Error: File `l3regex.sty' not found.   My packages:  \usepackage[colorlinks=true, linkcolor = blue, urlcolor  = blue, citecolor = blue, anchorcolor = red]{hyperref}   \usepackage[utf8]{inputenc}   \usepackage[top=1cm, bottom=2cm, left=1.5cm, right=1.5cm]{geometry}   \usepackage{amsfonts}   \usepackage{amsmath}   \usepackage{amssymb}   \usepackage{graphicx}   \usepackage{microtype}   \DisableLigatures{encoding = *, family = * }   \usepackage{coloring}   \pagenumbering{gobble}


i am doing a project in php i want to know is my code is preventing SQL injunction    $pageid=mysql_real_escape_string($page);         $query = "SELECT * FROM distdb WHERE BANK_ID = ".$pageid;

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


From Sipser's Introduction to the Theory of Computation:     A slight problem arises because certain numbers, such as 0.1999... and 0.2000..., are equal even though their decimal representations are different.   Can someone explain? Because that's news to me.

I'm told by smart people that $$0.999999999\ldots=1$$ and I believe them, but is there a proof that explains why this is?


I am trying to run an OpenGL program. When I compile that program terminal, it shows an error:  fatal error: GL/glut.h: No such file or directory  #include <GL/glut.h>   When I try to install freeglut, I got another error:  $ sudo apt-get install mesa-common-dev libgi-mesa-dev libglui-mesa-dev freeglut3-dev [sudo] password for yash:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package libgi-mesa-dev E: Unable to locate package libglui-mesa-dev    Please help me to figure this out.

When I try to install any package through the command line, I get an error.   $ sudo apt-get install <package> Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package <package>   Can anyone help me on this?


I am writing a powershell script to automate creation of websites in iis 10 and iis 8. This is what I have put in to the script till now: $WebSiteName = "TestApp8" $PathInfo = "D:\iis\testapp" $PortNumber = 1014 $CertificateName = "IIS Express Development Certificate" New-WebAppPool -Name $WebSiteName New-Website -Name $WebSiteName -ApplicationPool $WebSiteName -PhysicalPath $PathInfo -Port $PortNumber -ssl New-NetFirewallRule -DisplayName $WebSiteName -Profile 'Private' -Direction Inbound -Action Allow -Protocol TCP -LocalPort $PortNumber  The script works for majority of the part and creates a website as expected. However it misses out on one of my requirements, which is assigning a SSL certificate. It defaults to "Not Selected". My requirement is to assign a certificate which is already available in the drop down. For example, assign "IIS Express Development Certificate"  I have been following  to create the script. The document talks about -sslflags parameter. However I am not sure on how to use it and whether it will serve my purpose or not. Setting in a random value for sslflags has thrown an error stating: Bindings property 'bindingInformation' must specify hostname value when SSLFlags value is non zero.

Can you advise me whether it is possible or not to assign a SSL Certificate to a website in IIS7 using the APPCMD application?  I am familiar with the command to set the HTTPS Binding  appcmd set site /site.name:"A Site" /+bindings.[protocol='https',bindingInformation='*:443:www.mysite.com']   and how to obtain current mappings   %windir%\system32\inetsrv\Appcmd   but can not seem to find any way to map a site to a certificate (say the certificates hash for example)


I know that "fair enough" is similar to (but not the same as) OK, used to politely concede or partially agree with a point or to indicate that you understand where they're coming from. But then we have the following:  "I'm terribly sorry, yada yada yada so the system is currently down and and we have to enter everything manually." "Fair enough"  I would use "fair enough" here meaning "yea, that sucks, I understand why this is going to take longer than usual, I'm cool with it", but it just occurred to me that it could be understood as "I'm not sure if that's quite right but that's alright" as if I were questioning them. Is the former indeed a valid use of the phrase, or would it be more likely to be interpreted as the latter? Is it impolite to use it in a such way?  For a bit of extra context, I'm referring to Australian English specifically.

Is fair enough completely equivalent to OK? If not, under what circumstances should I say fair enough in my response? Any good examples will be most welcomed.


that following key should be XF86AudioLowerVolume, but it has not even a defined keycode, i could assign the function of XF86AudioLowerVolume. I've used xev to find that out. I'm using debian Jessie and a Thinkpad T520.  FocusOut event, serial 32, synthetic NO, window 0x1800001,     mode NotifyGrab, detail NotifyAncestor  FocusOut event, serial 32, synthetic NO, window 0x1800001,     mode NotifyUngrab, detail NotifyPointer  FocusIn event, serial 32, synthetic NO, window 0x1800001,     mode NotifyUngrab, detail NotifyAncestor  KeymapNotify event, serial 32, synthetic NO, window 0x0,     keys:  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0               0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   for comparison, the output of XF86AudioRaiseVolume  KeyRelease event, serial 32, synthetic NO, window 0x1800001,     root 0x9a, subw 0x0, time 2905663, (3,321), root:(810,328),     state 0x0, keycode 123 (keysym 0x1008ff13, XF86AudioRaiseVolume), same_screen YES,     XLookupString gives 0 bytes:      XFilterEvent returns: False   any ideas?

What do people mean when they point out that the "keys are not properly mapped" in a Linux installation when working on the command line?  Isn't the default installation OK? What extra/specific mappings are needed?    I also was told that for my Mac where my Home and End and Ctrl keys do not do what I expected.


I'm using QGIS 1.8.0; I have two layers turned on, one is the Google Earth hybrid layer from the OpenLayers plugin and the other a shapefile of my own making.  I set on the fly projection and everything looks spot on in the active window. When I got to composer everything still looks good. It's only once I have saved the image (exported) that there is an issue.   I think I read about this earlier but I can't find the answer to it anywhere. I can't remember if it has to do with on the fly projection or not... it seems ridiculous that the composer doesn't just "print the screen" of what's displayed there.  Any help would be great.  Shapefile is located   On the fly projection is UTM 50S or EPSG:32750

I'm having trouble with the OpenLayers Plugin of Qgis and the map composer:  If I create an OSM-background layer and if I want to export this, the OSM-Layer looks perfectly all right in the normal qgis program window. But in the map composer and after export the layer has shifted relatively to my other shape layers (EPSG:32633 - WGS 84 / UTM zone 33N).  The second thing is that the output resolution of the exported osm-layer is very, very poor.   A really bad way of getting around this whole trouble would be to increase the screen resolution and make a screenshot of the map composition window of qgis. But I don't think this would be very professional. It also would cause a lot of pain :)   I'm using Qgis 1.8.0-Lisboa under Linux. The openlayers plugin is version 0.92.


Given a macro  % bold task titles \newcommand{\mypar}[1]{{\bf #1:}}  %task decription template \newcommand{\task}[3]{     \mypar{#1} #2 \\     \emph{Solution:} #3\\ }   I should like for the text generated by a task macro to be an atomic unit. I.e. it either fits entirely into the space left on a page or all of it (and everything following it) is pushed to the next page.  What can I do to this macro to enforce this?

I want to do something like the following in TeX:  \begin{nobreak}    Text here will not split over pages, it will remain as one continuous chunk. If there isn't enough room for it on the current page a pagebreak will happen before it and the whole chunk will start on the next page.    \end{nobreak}   Is this possible?


On Ubuntu 18.10, when I press Super+[number] for an application with a single window, that window is brought to focus. If there are multiple windows though, I get a popup selection which requires me to choose which window I want, and then press Enter.    Is there a way I can get the following behavior?   Pressing Super+[number] and releasing focuses the first window of the application at [number] on the dock. Pressing Super+[number] and holding Super displays the popup.   Then pressing [number] multiple times cycles through the available windows. Releasing both keys on the selected window focuses that window.    This is the behavior on Windows, and I'm almost positive it's the behavior I had with Gnome on a different distribution. I might have had an extension installed or something though.

Ubuntu 18.04 (and presumably other versions that use Gnome, such as 17.10 and 18.10) has global keyboard shortcuts for switching among applications based on their location in the dock with Super-0...9:    But if you have multiple windows a given application open, instead of switching to the application, it will display a menu of all the open windows. You have to select one of the windows (using Enter or the mouse) to switch to the application.    Is there a way of having these global shortcuts instead automatically switch to the window of the application that's closest to the foreground?


I know the limit is $-e/2$ but I can't get there. I know I should be using L'Hopitals Rule here, I tried both $0/0$ and $\infty/\infty$, either way it's a big mess. Please help. Maybe you can use the $e^{log(...)}$ trick but I haven't found it to be useful.  Edit: I'm not familiar with the Big-O notation

In Problems in Mathematical Analysis, Volume 2 by Kaczor and Nowak, Problem 2.3.34 is stated as follow.   Find this limit using L`Hôpital rule  $$\lim\limits_{x\to\infty}x((1+\frac{1}{x})^x-e).$$  I have tried by using L'Hospital rule five times but have no result.  I can compute this limit by using Taylor expansion.


I have some idea of where the mistake in this 'proof' may be, but can't quite formalize.  We start with the trivially correct statement, $1 - 3 = 4 - 6$. Then, completing the square on the LHS, we add $\frac{9}{4}$ to both sides, giving us $1 - 3 + \frac{9}{4} = 4 - 6 + \frac{9}{4}$, which is still accurate. Then, we factor both sides into $\left(1 - \frac{3}{2}\right)^2 = \left(2 - \frac{3}{2}\right)^2$. I was confused particularly by this step, especially as to why this works on the right-hand side, but upon verifying it, it seems to hold.    The proof then, I think incorrectly, takes principal roots of both sides and writes that $1 - \frac{3}{2} = 2 - \frac{3}{2}$, which implies that $1 = 2$.   I believe the mistake is in not writing $1 - \frac{3}{2} = \pm \left(2 - \frac{3}{2}\right)$, but this statement is still inaccurate unless we take take the negation on the RHS, though I'm not sure why, other than realizing this with arithmetic, we would think to only take its negation.   So, my questions are:   (a) How does the factoring on the right-hand side work? I know that the standard method of factoring when completing the square is to take the square of the first number, sign of the second, and square of the third. But I don't quite understand 'why' this works or, for that matter, why it would work on the right-hand side, other than the fact that $4$ and $\frac{9}{4}$ are squares, though I don't understand the significance of the $-6$ here: if this is all that is required, that $-6$ could in principle be anything at all, which is surely not the case.   (b) Is it correct that the mistake in the proof is in taking principal square roots? What is the logic behind leaving out the $\pm$ here?

$$\begin{align} 2+2 &= 4 - \frac92 +\frac92\\ &= \sqrt{\left(4-\frac92\right)^2} +\frac92\\ &= \sqrt{16 -2\times4\times\frac92 +\left(\frac92\right)^2} + \frac92\\ &= \sqrt{16 -36 + \left(\frac92\right)^2} +\frac92\\ &= \sqrt {-20 +\left(\frac92\right)^2} + \frac92\\ &= \sqrt{25-45 +\left(\frac92\right)^2} +\frac92\\ &= \sqrt {5^2 -2\times5\times\frac92 + \left(\frac92\right) ^2} + \frac92\\ &= \sqrt {\left(5-\frac92\right)^2} +\frac92\\ &= 5 + \frac92 - \frac92 \\ &= 5\end{align}$$  Where did I go wrong


I set up a validation rule that prevents our delegated admin users from creating/updating a user to not have a role. The validation rule works exactly as expected when creating/updating the user directly from a user record.  AND(  ISPICKVAL(UserType, "Standard"),  ISBLANK(UserRoleId))   Today, I found that some of our delegated users have inadvertently removed roles from some of our users via the Setup | Manage Users | Roles | and then using the assign link by removing the user from the list.    Why does this area ignore validation rules and is there a non-programmatic way to enforce removing a role from a user?

There are two ways to change user role. One is from user detail page, which invoke user trigger. I am facing issue where if user role is changed from ROLE hierarchy screen, then user trigger is not being invoked.  Any body know if there is written documentation which specifies this? or is it just my ORG having some setting to skip user trigger?   Below is screenshot of the screen from where it happens.


I was looking through some of my reviews because I wanted to know what happened to some questions I had reviewed earlier, and discovered clicking on a link from the Activity page then using the Back button would display me the page as it was almost 2 weeks ago.  Page while viewing it:     Page when hitting the Back button:    I found this extremely confusing until I realized what was happening.  Switching between the filters (all, accepts, posts, etc) also displays old data, but clicking on the Activity tab correctly refreshes the page and gives me current data.  Can the Back button take us to the most recent cached data, and not some data from almost 2 weeks ago?  (Not sure if it matters or not, but I'm using Chrome)

I've noticed recently that, when viewing the comments tab, my user-page decides to go back to an arbitrary point in time. It's also getting earlier and earlier.   This seems to be my user-page as of a month ago. This screenshot was captured, this morning, from a newly opened page (i.e. one that hadn't been sat on my browser for a month).    And the current one (also newly opened this morning)    This also happened earlier in the week but it only went back a few weeks rather than an entire month.  I'm using Chrome 19.0.1084.52 and have deleted cookies and emptied the cache after the last time this occurred.  I'm not really certain how to explain this but it seems like SO is displaying my user-page as it would have appeared a month ago. It doesn't happen often and, so far, has only occurred when on the comments tab.   I, perhaps wrongly, assumed that a cached version of the page was being displayed.  It may well be ; it's not that important just a little disconcerting.


I need to create a HTML/JavaScript code to edit hiring/firing records for a given employee (the software receives a constant employee ID for the UI to deal with one employee at a time).  One employee may be hired and fired several times during the history of our company. (For example she may go to a parental leave and return to the work later.)  The table has the following fields:   employeeid (the ID of the employee) hired (date) fired (date) firereason enum('fired','left','parental','vacation','sick','death')  comment text   As you see there are a number of fire reasons:   'fired' (forced to be fired by the boss) 'left' (left the job by his own will) 'parental' (left for a parental vacation) 'vacation' (non paid vacation) 'sick' (sick leave) 'death' (death)   I want to present the list of pairs of hire/fire to the editor as a table, sorted by hire date.  Note that for the last hire/fire record fire date may be missing (null), if the employee for hired but not yet fired.  I am lost about more details how it should be presented and interacted.    After some additional thought I decided that it is best to present the information as a static (non-editable) table with "Edit" buttons in every row.  Now an additional question is arisen: Should "Edit" open a modal window above gray background or an additional row in the table? Which of these two variants is better? Also which buttons should be present in this additional row: "OK", "Cancel"? Can we switch to editing an other row without pressing "OK" or "Cancel"?

I'm interested to know what would be best the option from a UX perspective. I have a table in which i need to decide if i should edit each row with inline editing where you can click on each item in the row and edit seperately or all at once with a modal popup.


If we call addition (and subtraction as they are the same) the first hyperoperator, multiplication (and division) the second, exponentiation (radicals, indices and logarithms) the third, then tetration the fourth and so on, we then have a definition of a hyperoperator.   My question is:     Is there a way to have a fractional hyperoperator such as an operation half way between addition and subtraction which would be the 1 + 1/2’th hyperoperator.

I noticed this  which attempts to find the shades of grey between a linear and log scale where results are between zero and one.  However, I was looking for the more general case where we find the continuum between the operators themselves - add, multiply, and exponentiation or even higher.  The function could be a hyperoperation$(n,x,y)$, where $x$ and $y$ are the numbers to operate on, and $n$ is allowed to be a non-integer number for the type of operator. So $n=1$ would be 'addition', $n=2$ would be multiplication, and $n=3$ would be exponentiation. But one would also have $n=2.5$ to be the shade of grey BETWEEN multiplication and exponentiation, or $n=3.5$ or $4$ for beyond exponentiation and tetration).  I want the formula to work with real numbers, not just integers. Any thoughts?  These related posts may also be of interest:


In Harry Potter and the Order of the Phoenix chapter 36, we see  Professor Dumbledore dueling with the Dark Lord in the Ministry of Magic.  From their exchange, it seems that Professor Dumbledore is not fighting to kill.     ‘You do not seek to kill me, Dumbledore?’ called Voldemort, his scarlet eyes narrowed over the top of the shield.  ‘Above such brutality, are you?’      ‘We both know that there are other ways of destroying a man, Tom,’ Dumbledore said calmly, continuing to walk towards Voldemort as though nothing had happened to interrupt his stroll up the hall.  ‘Merely taking your life would not satisfy me, I admit –’   Why did Professor Dumbledore not try to kill the Dark Lord?    At that time, Professor Dumbledore may have suspected that the Dark Lord has another Horcrux, so he would not truly die, but only become a bodyless spirit.  Even so, that would have been a huge setback to the Dark Lord’s plans, as evidenced from Professor Dumbledore’s explanation in Philosopher’s Stone chapter 17.     ‘[… Voldemort] is still out there somewhere, perhaps looking for another body to share … not being truly alive, he cannot be killed.  He left Quirrell to die; he shows just as little mercy to his followers as his enemies.  Nevertheless, Harry, while you may only have delayed his return to power, it will merely take someone else who is prepared to fight what seems a losing battle next time – and if he is delayed again, and again, why, he may never return to power.’   This question may be a special case of

During the First Wizarding War, why didn't Dumbledore just hunt Voldemort down, as he had done with Grindelwald?  By 'hunting down', I mean finding, defeating and imprisoning him, exactly as in Gridelwald's case, and not, say killing him, something which Dumbledore would not do, as the answers to a previous question (as to him not hunting down Death Eaters) show.  Dumbledore knew that Voldemort had delved into the Dark Arts deeper than anyone else in history and hence "had powers he will never have". But he must have also known well that he could have defeated Voldemort at a direct confrontation, given that he had defeated Grindelwald earlier even against the Elder Wand, and now had that same wand at his disposal. He is seen confident about this throughout the series.  At the Battle of the Department of Mysteries, he did not go beyond outweighing Voldemort and forcing him to flee, probably because, by then, he had reasons to suspect that there was more to Voldemort's survival than his physical body, and thus, destroying that body which had Harry's blood without permanently disposing him off would not have been wise.  But why did he not do that at the First Wizarding War? Is it just that they could not track him down, or did he suspect even then that Voldemort had more sinister things about his soul? is there any canon confirmation of the latter suspicion?


Evaluate the integral $$P(s)=\int^\infty_0 \frac{\ln(x) \,dx}{1+x^s}$$  I tried integration by parts, using $u=\ln(x),du=\frac{x}{dx},v=\frac{1}{1+x^s}$, but I did not manage to get anything. I thought about using a power series, but I did not find one that converges on the entire domain. Using the substitution $u=\ln(x),du=\frac{dx}{x}$ we get $$\int^\infty_{-\infty} \frac{ue^{-u}}{1+e^{su}} ,$$ which doesn't seem useful either. The previous similar question  gives $$\int^\infty_0 \frac{x^n \,dx}{1+x^s}=\frac{\Gamma(\frac{1}{s})\Gamma\left(1-\frac{1}{s}\right)}{s(n+1)} .$$ Another possibly relevant question is .

Seeking Methods to solve the following two definite integrals:  \begin{equation} I_(n) = \int_0^\infty \frac{\ln(t)}{t^n + 1}\:dt \qquad J(n) = \int_0^\infty \frac{\ln^2(t)}{t^n + 1}\:dt \end{equation}  For $n \in \mathbb{R},\:n \gt 1$  The method I took was to take the following integral:  \begin{equation}  \int_0^\infty \frac{t^k}{\left(t^n + 1\right)^m}\:dt = \frac{1}{n}B\left(m - \frac{k + 1}{n}, \frac{k + 1}{n} \right) \end{equation}  Where: $0 \leq k \lt n$. Here let $m = 1$.   with respect to $k$ and taking the limit as $k \rightarrow 0^+$ (via the ), i.e.   \begin{align} \lim_{k \rightarrow 0+} \frac{d}{dk} \left[ \int_0^\infty \frac{t^k}{t^n + 1}\:dt \right] &= \lim_{k \rightarrow 0+} \frac{d}{dk} \left[\frac{1}{n}B\left(1 - \frac{k + 1}{n}, \frac{k + 1}{n} \right) \right] \\ \lim_{k \rightarrow 0+}  \int_0^\infty \frac{t^k \ln(t)}{t^n + 1}\:dt  &= \lim_{k \rightarrow 0+}  \left[\frac{1}{n^2} B\left(1 - \frac{k + 1}{n}, \frac{k + 1}{n}\right)\left[\psi^{(0)}\left(\frac{k + 1}{n} \right) - \psi^{(0)}\left(1 - \frac{k + 1}{n} \right)\right] \right] \\ \int_0^\infty \frac{\ln(t)}{t^n + 1}\:dt&= \frac{1}{n^2} B\left(1 - \frac{1}{n}, \frac{1}{n}\right)\left[\psi^{(0)}\left(\frac{1}{n} \right) - \psi^{(0)}\left(1 - \frac{1}{n} \right)\right] \\ &=- \frac{\pi^2}{n^2}\operatorname{cosec}\left(\frac{\pi}{n}\right)\cot\left(\frac{\pi}{n} \right) \end{align}  Which is our expression for $I_n$. Taking the same approach but differentiating twice with respect to $k$ we arrive at our expression for $J_n$:  \begin{equation}  J(n) = \int_0^\infty \frac{\ln^2(t)}{t^n + 1}\:dt = \frac{\pi^3}{n^3}\operatorname{cosec}\left(\frac{\pi}{n} \right)\left[\operatorname{cosec}^2\left(\frac{\pi}{n}\right) + \cot^2\left(\frac{\pi}{n}\right) \right] \end{equation}  And in fact we may generalise:  \begin{equation}     \int_0^\infty \frac{\ln^p(t)}{\left(t^n + 1\right)^m}\:dt = \lim_{k\rightarrow 0}\frac{d^p}{dk^p}\left[\frac{1}{n} B\left(m - \frac{k + 1}{n}, \frac{k + 1}{n}\right)\right] \end{equation}  Where $p \in \mathbb{N}$  This method however was just an extension of another integral. I'm curious, if I had just started with $I_n, J_n$ what alternative methods could be used?


I've seen this situation arise a few times lately, and I find that it actually annoys me a bit.  Take  question as an example.  There are 3 comments posted by the same guy (not sure if I should link his profile here directly, or if that would be considered bad form) within the space of a minute that are all asking to check his answer.  One such comment is to the OP directly, and the other two are posted under other people's answers.  It's all pointless, and just adds to the noise, when anyone can read the whole question anyway.  It also makes me feel like the guy's more concerned with farming reputation, rather than creating an answer that is correct (which his isn't).  I could understand if he was pointing out a specific issue with someone's answer, or if it was a link to an answer on a different question, but it's neither of those.  Are these kinds of comments to be discouraged, and should I be flagging them?

I've started to flag a few of these once I had seen one too many of them, but I'm not sure whether I'm doing the right thing.  This is an example of what I'm talking about (this comment is on the question, but sometimes on their own answers too):    Are they something that should be considered acceptable, and if not, are they bad enough to be "flaggable"?


I'm trying to use scp to transfer a file from a server (which, admittedly, I know not much about) to my local machine. I ssh'ed into the server, and used pwd in the directory of the file to be sure I had it down correctly. Then, I used pwd in the directory of my local machine where I'd like to place the file, just to be sure. I ran scp myusername@server.com:/path/to/file/file.txt /path/to/local/directory. I didn't get any error messages, only export SROOTBASE="/cvmfs/servername.org/py2-v2". When I looked for the file on my local machine, nothing was to be found. I then tried searching for it by name, and still found nothing. What's going on here?


I'm having some trouble understanding the constraints on the rule of inference Universal Introduction.  From :     The full generalization rule allows for hypotheses to the left of the turnstile, but with restrictions. Assume $\Gamma$  is a set of formulas, $\varphi$  a formula, and $\Gamma \vdash \varphi (y)$ has been derived. The generalization rule states that $\Gamma \vdash \forall x\,\varphi (x)$ can be derived if $y$ is not mentioned in $\Gamma$  and $x$ does not occur in $\varphi$.   (Emphasis mine)  I dont understand why these constraints are correct. I have seen other constraints elsewhere, and those I understand (I think). For example, the universal introduction in Dirk van Dalen's Logic and Structure (4th ed) is:     $${\forall I}\, \frac{\varphi}{\forall x\, \varphi} $$   where the intended restriction is: the variable $x$ may not occur free in any hypothesis on which   $\varphi$ depends, i.e. an uncancelled hypothesis in the derivation of $\varphi$.   I understand why this is correct (we learned a similar pair of constraints in class), but according to the constraints described on the Wikipedia article, I dont see why I would not be able to infer the following (obviously this is incorrect) from the set of premises $\Gamma = \{\exists x \varphi(x)\}$  $$ 1.\ \exists x \varphi(x) \quad \quad \quad \quad \quad \quad \quad \quad \text{premise} $$  $$ 2.\ \varphi(y) \quad \quad \text{1, existential elimination} $$ $$ 3.\ \forall x \varphi(x) \quad \text{2, universal introduction} $$  This seems to imply that $\exists x \varphi(x) \vdash \forall x \varphi(x)$, and I dont see how this would violate the conditions on Wikipedia. $y$ has not been mentioned in $\Gamma$, and $x$ does not occur in $\varphi$.  Am I misunderstanding something? Or is the Wikipedia article wrong?

doesn't seem to give a satisfactory explanation of the restrictions on when it can be used:  Assume $\Gamma$ is a set of formulas, $\varphi$ a formula, and $\Gamma \vdash \varphi(y)$ has been derived.  The generalization rule states that $\Gamma \vdash \forall x \varphi(x)$ can be derived if $y$ is not mentioned in $\Gamma$ and $x$ does not occur in $\varphi$.  The article then gives an example of UG being used incorrectly to derive $\exists z\exists w(z\neq w) \vdash \forall x(x\neq x)$, with the restrictions given certainly being violated.  However, wouldn't the following modification of the "proof" be in accordance with the restrictions?  $\exists z\exists w(z\neq w)$ $\exists w(y\neq w)$ $y\neq x$ $\forall\alpha(\alpha\neq x)$ $x\neq x$  Here, the generalization in step 4 has been amended to use $\alpha$ as the quantifier's bound variable, which should be permitted, as $\alpha$ does not occur in $y\neq x$ and $y$ does not occur in the assumption $\exists z\exists w(z\neq w)$, yet this leads to a universal instantiation that is clearly false!  Is the $\Gamma$ of the restrictions meant to be all previous steps of the proof, not just the assumptions?  If so, wouldn't this invalidate the proof given further in the article that includes the steps $P(y)\to Q(y)$ and $P(y)$ before generalizing $Q(y)$?  Does the presence of existential instantiation place further restrictions on universal generalization somehow, with the existential instantiated counting as a mention of the variable introduced?


I've noticed a recent glut of so called "Virtual Assistants" asking for help within a few different Google Sheets / Excel related tags on StackOverflow. I'm fine to help such folks if it's just help, but lately it feels more and more that they are trying to farm out their work to volunteers. What is the best way to handle this problem/suspicion? I'm relatively new to the Stack Community so maybe this is a commonly discussed problem and someone could point me to a discussion thread?

What is the best long-term solution for the  problem? Adapted from the above article:  Identifying Help Vampires can be tricky, because they look like any ordinary person (or Internet user, whichever is lesser). But by closely observing an individual's behavior using this handy checklist, you too can identify Help Vampires in the field:  Do they ask the same, tired questions others ask (at a rate of once or more per minute)? Do they clearly lack the ability or inclination to ask the almighty Google? Do they refuse to take the time to ask coherent, specific questions? Do they think helping them must be the high point of your day? Do they get offensive, as if you needed to prove them why they should use Ruby on Rails? Are they obviously just waiting for some poor, well-intentioned person to do all their thinking for them? Can you tell they really aren't interested in having their question answered, so much as getting someone else to do their work?


I realized that I only had one nameserver configured for an EC2 web server I set up last year, as the other elastic IP didn't get associated. Everything seems to work though? Is it necessary to have a working second nameserver for an EC2 web server?

Do you need separate elastic IP addresses for each nameserver - say NS1, NS2 - for an EC2 webserver?


For grad school application (US univerisity), we need recommendation from prof. I guess the process is that system send out recommendation letter request to prof's email.  Do you guys know how long does it take to submit these recomendation letter? Does it need to fill extra form while submitting these letter?    I ask because I want to know how time consuming it is. Should I limit the # of school I apply because it might be too much work for the prof?

When applying for post-doctoral and faculty positions you are typically asked for three (sometimes more) reference letters to support your application.    Given that it is competitive out there, it also makes sense to apply for all positions that are good matches to your qualifications and career development goals (in the case of post-docs).  Sometimes this may mean asking for several reference letters (or pre-application "can you support me if required?" requests) in a short space of time.  Also, there may only be a small pool of people (i.e. 3 or 4) who know your work sufficiently well to give an excellent reference.  I have also been told that referees want to help you out, and that there is no reason to fear asking them.  And, that in many cases once a letter is written it can typically be quickly repurposed.  But there must be a breaking point.  How do I manage this without being disrespectful?  How many requests in a given unit of time is too many, or harms my credibility?   I am asking this question in this forum, as I am interested in the norms in the academic world, which are often somewhat different than the rest of the working world.


During the review process of an article, the reviewers are (almost always) anonymous by default for obvious reasons.  Why are not authors also made anonymous?  It could help remove the weight that established authors carry in certain fields (which can tilt the scale in their favor), as well as the stigma associated to research coming from non-developed countries.  Are there any good reasons why this is not done? I can not think of any.

I'm new to the journal publishing world, and I can't but help wonder why the review process isn't completely blind?  By blind, I mean the reviewers don't know who performed the research or (more importantly) what university the research came from.  It seems that knowing the identity of the authors could influence the review such that the quality of the research no longer stands by itself. You should be able to read an article and, assuming that the experiment was conducted accurately and ethically, decide if it is a significant scientific advancement. Why are reviews not routinely double-blind?


It was found on a roof in Jaipur, Rajasthan, North-Western India.

Could someone tell me what the species of this beautiful insect is? Location: Chennai, India.   Thank you!


What is the difference between "" and ""?  I always assumed they are the same, until today I found both of them in one place for choice, seems that there's a difference between them:  N.b. I couldn't find a difference on the dictionary (see links to the words).

I am going to do an overseas internship in Canada next month. Since I have never worked with foreigners before, so now I wonder what I should call my boss or colleagues.   My supervisor is a Chinese, I don't know her English name, she is much older than me and I do know she is married.  Her family name is Liu (not her husband's). So may I call her Ms. Liu, or Mrs. Liu, I am not sure which one is correct. How about other foreigner supervisor? Should I call them MR. XX, MS. XX, or just call them first name directly. Can I ask them directly "Can I have your name or What should I call you"  For the colleagues which are older than me, I think I just need to call them first name?  Thanks.


I'm trying to regenerate an old document where I used to extract tikz figures using preview and I'm getting into a problem where preview extracts every page of the document rather than just the tikzpicture environments. The setup for preview are in this , included .   Here's the way I invoke the extraction:   pdflatex -file-line-error -halt-on-error '-interaction=nonstopmode' \   '-output-directory=src' '-jobname=ocamlunix-image' \   '\PassOptionsToPackage{active}{preview}\input{src/ocamlunix.tex}' This is pdfTeX, Version 3.14159265-2.6-1.40.15 (TeX Live 2014) (preloaded format=pdflatex)  restricted \write18 enabled. entering extended mode LaTeX2e <2014/05/01> Babel <3.9k> and hyphenation patterns for 21 languages loaded. (./src/ocamlunix.tex (/usr/local/texlive/2014basic/texmf-dist/tex/latex/memoir/memoir.cls Document Class: memoir 2013/05/30 v3.7b configurable book, report, article docu ment class (/usr/local/texlive/2014basic/texmf-dist/tex/generic/oberdiek/ifpdf.sty)  [...] Output written on src/ocamlunix-image.pdf (160 pages, 849607 bytes).   Any hints about what may be going on ?

This minimal example produces an error (undefined control sequences):  % !TEX TS-program = pdflatexmk  \documentclass{article}  \usepackage{tikz} \usepackage{preview}  \begin{document}  Hello.  \end{document}   Once the tikz package is removed, it compiles fine. Removing either usepackage commands allows the program to compile. Moreover, including both, but adding the [active] option to preview allows the script to compile.   I've pasted the log file .


So I have a string with multiple newline escape sequences within it. I would like to cut the string to the first n lines, like the head program from coreutils. For example say I have the string "a\nb\nc\n", I would want the first line so I would want my output string to be "a". In other cases where I needed to cut a string I simply placed a null terminator in the position where I wanted the string to end. However when I run something like this:  void main() {     char *str = "a\nb\nc\n";     str[1] = '\0'; }   I get a segfault. I really don't understand why. What can I do to fix this?

The following code receives seg fault on line 2:  char *str = "string"; str[0] = 'z';  // could be also written as *str = 'z' printf("%s\n", str);   While this works perfectly well:  char str[] = "string"; str[0] = 'z'; printf("%s\n", str);   Tested with MSVC and GCC.


Can someone suggest what keywords I should use to search online for "Using SSH folders as a directory for my local system?"?  I want some files on my system to interact with files on a SSH server I have access to.

I have two RasberryPi running debian wheezy and I would like to mount a folder from computer A on computer B.  What is the best (as in most efficient) way to do this?  I can do it via SMB, but that is for windows, I think there must be a better way to share across linux.


I have a table as shown below, and am trying to create a fixed header, so that no matter how much I scroll down, the header is always visible to the user. I don't have much experience with web design, so was wondering how to do this using either css / javascript? What I'm guessing is that I first need to put a
 tag around the  tags to make them one entity? Although this has to be done using javascript, as the html is generated using an external macro which I am not able to edit. Any help is much appreciated!

       Server Name  	       Network Zone  	       Operational Status

 w264521f

 GREEN

 READY

   Please note that the columns are not fixed width. They need to be variable, as the data is not constant.

Is there a cross-browser CSS/JavaScript technique to display a long HTML table such that the column headers stay fixed on-screen and do not scroll with the table body. Think of the "freeze panes" effect in Microsoft Excel.  I want to be able to scroll through the contents of the table, but to always be able to see the column headers at the top.


I don't really understand how to solve the equation $$47x \equiv 4  \mod 17.$$ If someone could help, that would be much appreciated. Thanks!

Problem :   Solve in $\mathbb N$ :   $8n+9\equiv 0\pmod{1163}$  The mathematics give me : $n=435+1163k$ , $k\in\mathbb N$   $1163$ is a prime number   $8n\equiv -9\pmod{1163}$   $8n\equiv 1154\pmod{1163}$   I don't know any ideas to complete my work ?   I have to see your hints


I'm creating a game in Unity3D and I'm using blender as my main modeling software, The problem here is that I don't know how to make a low poly water cube, I've seen that a lot of people makes this using a plane, but I need to make a cube, and I can´t find how to make this in blender render or in Unity without A package from Asset Store. It should look like this:

How would I achieve this low poly water effect using cycles?    But the closest I've gotten would be this: