I check Stack Overflow every day and one thing that surprised me is that the users do not upvote my answers or select my answer as The Answer when my answer is the solution.  Am I missing something here? Because this really bothers me, that I can't collect reputation and this kind of things disappoint me on continuing to contribute to this community.

While at least some answers from every question seem to have been up-voted as a "helpful" answer:   about 49% of questions have score of 0 or 1. another 21% of questions have a score of 2.   Most questions seem to have an answer or two with score +5. Is it that we have a lot of fluff questions and not useful ones? Or perhaps it just seems more natural to vote for answers than questions? If we want the most useful info on Stack Overflow to filter to the top, how can this disparity be fixed?  I think this may cause real problems for people getting the badges which require +25 or +100 votes on questions.    I like a lot of the feedback I'm seeing. Two problems are highlighted:   The work flow doesn't promote voting for questions the way it promotes voting for answers. One solution: when a user answers a question, the system should invite them to vote for the question.  If someone cares enough to answer a question, then they care enough to vote for it as well. Users with less than 15 reputation cannot vote for questions or answers. Is this warranted?  Maybe these users could provisionally vote for questions and answers and those ratings would only take effect when the user reaches 15 reputation?   All I ask is this. As you browse Stack Overflow, when you see a good question: vote for it.  If everyone does, then this problem will disappear.


There have been several post on this subject, but most are dated 3-4 years ago, or more. I have recently installed Minecraft on my iMac. My sons have it installed on their iPads. Is there any way for them to join the world I've created on the iMac?  I didn't think this was a duplicate question, as the ones I had found were old. Further, there appeared to be conflicting answers in those that I did find. Thus, my reason for this post was to get an August 2016 clarification.

My kids are playing Minecraft on 2 PCs, creative mode.  They are connected by the way of one of them starts a single player game on the other one than joins that game over the LAN.  Can I, using Minecraft PE on my iPad, join their game as well?


import java.util.Scanner; class TestMatrix {     public static void main(String args[]){         Scanner in=new Scanner(System.in);         System.out.println("Enter the number of matrices: ");         int num=in.nextInt();         int[][] temp=new int[10][10];         Matrix[] matrixarray=new Matrix[num];         Matrix.numberOfMatrices(num);         for(int i=0;i<num;i++)             {                 System.out.println("Enter the rows and columns of M["+(i+1)+"]: ");                 int r=in.nextInt();                 int c=in.nextInt();                 System.out.println("Enter the values: ");                 for(int x=0;x<r;x++)                     for(int y=0;y<c;y++)                         {                             temp[x][y]=in.nextInt();                         }             matrixarray[i].inputMatrixValues(temp);              }         } } public class Matrix {     static int number;     int[][] matrix=new int[10][10];     int row,col;     public static void numberOfMatrices(int n)     {number=n;}     public void inputMatrixValues(int[][] matrix)     {         for(int i=0;i<row;i++)             for(int j=0;j<col;j++)             {                 this.matrix[i][j]=matrix[i][j];             }     } }   the above code returns null pointer exception while calling the method inputMatrixValues() at line 22. matrixarray[i].inputMatrixValues(temp);  matrixarray is an object array of class Matrix. The exception occurs while accessing the ith element of object array. Matrix object array is created in line 9. Pls check what part of the code causes error.

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?


For a list of input text, I want to execute a repetitive command using each element from the list. In addition I also need to monitor the results of each of these commands in parallel. So I am looking for a solution to display the repetitive commands output in separate windows in a single terminal console; probably need a form of terminal multiplexer?  So far I have the following:  for i in `command1 find msgs/Poly`; do echo command2 echo "$i" ; multitail -l 'command2 echo "$i"' ; done    which seems to open only one window at a time.

From vi, if you issue the command :sp, the screen splits into two "views", allowing you to edit more than one file from the same terminal.   Along those same lines, is there a way to have multiple shells open in the same terminal?


This question is a part of my other question . I have fiddled and example of the broken line item feature. You can use the add row button to add rows and the tiny square to the right is supposed to be a glyphicon trash can which will remove a row.   In the example given you will notice that the first two lines which are part of page load will allow you to edit quantity and rate values and will auto updated the subtotal and grand totals. The issue comes in when you add a new row and attempt to update the quantities and rates. Nothing happens.  I believe this conflict is due to something I am not seeing in the following functions. OR, worse yet something to do with the table row being added and jquery not being allowed to access the elements.  $('#addVar').on('click', function(){    var varCount = $('#lineitem tr').length;    $node = ['
',     ''+varCount+'	',     '<select name="itemID[]" class="itemID form-control">',     '<option disabled selected>Product/Service</option>',     '</select>	',     '<input class="itemdetail form-control" type="text" name="describe" value=""/>	',     '<input id="qty" class="qty form-control" type="text" name="qty" value="0"/>	',     '<input id="rate" class="rate form-control" type="text" name="rate" value="0.00"/>	',     '<input id="amount" class="amount form-control" type="text" name="amount" value="0.00"/>	',     '	',     '
'].join('\n');   $('#lineitem > tbody:last').append($node); });   and  $("select.itemID").mousedown(function(){     var $this = $(this);     if (data) {         $(this).val(data);     } else {         itemList();         $(this).html(result);     } });     Other factors from the original question will have effects on this row. like select list on mousedown and on change events ( which dont work either ) are intended to populate the row after which the user would be able to edit quantity and rates.  EDIT** before duplicating with questions like that one be sure to read the code.... EVERYTHING is bound to .on() events therefore is not a duplicate problem.. Something else is wrong. I have triwd variations of .on("mousedown","#itemID" function... they change nothing directly

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 have a boolean which checks if an action is to be performed or not, the boolean is being being accessed through setters and getters, I have other booleans am accessing in a similar way and they are not giving me any errors except this one, at first I was checking it in a piece of code within a seperate thread and that part was not working without producing an exception so I put it in a toggleButton just to do a simple read and write on it, then the nullPointerException came up, here is my code I have commented it  toggleButton.setOnMousePressed(new EventHandler<MouseEvent>() {         @Override public void handle(MouseEvent event) {          //this part is executing perfectly          //meaning my toggleButton is ok          System.out.println("Toggle Button Clicked");           //this is where I am getting the NullPointerException          if(!getblackAndWhite()){              setblackAndWhite(true);           }else{                setblackAndWhite(false);            }         }});   private void setblackAndWhite(Boolean blackAndWhite)  {     this.blackAndWhite = blackAndWhite; }  private Boolean getblackAndWhite() {     return this.blackAndWhite; }


I was wonder if there is an equivalent to  for Ubuntu. The Pageant tool load private keys for prolonged usage, so you won't have to load the keys (as well as heir passprhases, if there are any), each time anew.   How could you achieve this in Ubuntu, and especially the Ubuntu CLI?

I've created passphrase protected RSA key. The public key is installed on remote server in authorized_keys in the user's .ssh directory.  From requesting server, I can SSH into the remote server without a problem, but I need to enter passphrase every time I do this.  I want to use this key for a Munin server to SSH into a Munin node and get data, so the procedure fails because of the passphrase.  I have thought of two options:   Remove the passphrase from the key. Save the passphrase somewhere, maybe in a configuration file?   Is there a better solution?  I think ssh-agent is supposed to do something like this, but I cannot find concise information about it.


I normally use Thunderbird as my email client, but the other day I accidentally started up evolution.  Now the envelope icon in the indicator area contains information about both Thunderbird and Evolution. Since I'm not using Evolution, I tried to get rid of the Evolution information by uninstalling the evolution-indicator package, but this didn't help. I still have both Thunderbird and Evolution listed when I click the envelope icon. (And, yes, I did restart the computer.)  The /usr/share/indicators/messages/applications/ directory only contains Thunderbird and Empathy, not Evolution.  How do I get rid of the Evolution information?

I have recently upgraded from 12.04 to 14.04 and then noticed the usual email icon (little envelope icon) which allowed me to run my Evolution, chat and Thunderbird applications is no longer available. Is there a simple way of getting it back?


I just installed the new one Debian xfce via VirtualBox, but decided to increase the vdi size from 8GB to 20GB (because it requires 42% of all disk space at this moment):     VBoxManage.exe modifyhd debian.vdi --resize 20000   VirtualBox Manager tells me that debian.vdi now has 20GB as supposed, but when I started Debian, the df output tells me that it has 8GB as earlier. Why?

I am running Virtualbox. I increased the size of my hard disk (.vdi) from 10G to 15G. Now when I start my Mint vm, the hard disk reports as 7.5g (df) even though i extended it (fdisk -l). I am not sure what is the problem. Can anyone point me the problem?  $ df -h Filesystem      Size  Used Avail Use% Mounted on /dev/sda1     >>7.5G<< 7.1G   61M 100% / udev            1.5G  4.0K  1.5G   1% /dev tmpfs           581M  888K  581M   1% /run none            5.0M     0  5.0M   0% /run/lock none            1.5G   88K  1.5G   1% /run/shm  $ sudo fdisk -l Disk /dev/sda: >>16.1 GB<<, 16106127360 bytes 255 heads, 63 sectors/track, 1958 cylinders, total 31457280 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000c55a4     Device Boot      Start         End      Blocks   Id  System /dev/sda1   *        2048    15728639     7863296   83  Linux /dev/sda2        15730686    16775167      522241    5  Extended /dev/sda5        15730688    16775167      522240   82  Linux swap / Solaris  $ vboxmanage showhdinfo mint.vdi UUID:                 a94931b9-673c-440a-ab6b-2c3eedd0cf93 Accessible:           yes Logical size:         15360 MBytes Current size on disk: 7806 MBytes Type:                 normal (base) Storage format:       VDI Format variant:       dynamic default Location:             /opt/virtualization/vm/mint.vdi


What the following code does is take the selected genre genre and check if it contains one of the data which are all arrays.  Example:  genre = "comedy"; data = ["action", "comedy"]   I just want to check if data contains "comedy":  $( "header section" ).selectable({     selected: function() {         var genre = $(".ui-selected").data("genre");         console.log(genre);         $("body > section div").each(function() {             var data = $(this + ":contains('" + genre + "')").data("genre");             if (data != genre) {                 $(this).css("display", "none");                } else {                 $(this).css("display", "block");             }     });     }  });   I tried to do it with the Selector "contains" but it doesn't work with this I think.

What is the most concise and efficient way to find out if a JavaScript array contains a value? This is the only way I know to do it: function contains(a, obj) {     for (var i = 0; i < a.length; i++) {         if (a[i] === obj) {             return true;         }     }     return false; }  Is there a better and more concise way to accomplish this?


On my ubuntu phone the date is not shown correct, it always shows the yesterday's date,I have to restart the device and then it works and my settings are on automatically, why this ?

I have a new Ubuntu Aquaris E4.5 phone (latest updates installed).  Locale UK Timzone British Summer Time.  The Today Scope screen does not automatically change days, so for example today is Thursday, but this morning is was still showing Wednesday.  The only way I could seem to get it to change was to reboot the phone.  Is this a bug? or have I done something wrong?


Can someone could help me write the mathematical/backshift equation for the seasonal ARIMA (0,0,1) x (2,1,2) with 12 periods? I'm confused with how to go about this. I would prefer an equation involving $B$, $Y_{t}$, $e_{t}$, $\phi$, $\Phi$, $\theta$, and $\Theta$.  This is different from other models that have previously been answered and I don’t understand the explanation in FPP2.

I would appreciate if someone could help me write the mathematical equation for the seasonal ARIMA (2,1,0) x (0,2,2) period 12. I'm a little confused with how to go about this. I would prefer an equation involving $Y_t , e_t, θ$ and $Θ$.


I'm getting a NullPointerException by running the following code:  Main:  public class NeuralXOR {  public static void main(String[] args) {     double[] inputs = {1.0, 0.0};     NeuralNetwork network = new NeuralNetwork(2, 1, 3, 0.7, 0.9); }   }  Neural Network Classes: public class NeuralNetwork {  Node[] inputNodes; Node[] hiddenNodes; Node[] outputNodes;  Layer[] layers;  int noOfInputNodes; int noOfOutputNodes; int noOfLayers = 3;  public NeuralNetwork(int noOfInputNodes, int noOfOutputNodes, int noOfHiddenNodes, double learningRate, double momentum) {      this.outputNodes = new Node[noOfOutputNodes];     for (int i = 0; i < outputNodes.length; i++) {         outputNodes[i] = new Node(i);     }      this.hiddenNodes = new Node[noOfHiddenNodes];     for (int i = 0; i < hiddenNodes.length; i++) {         hiddenNodes[i] = new Node(i);     }      this.inputNodes = new Node[noOfInputNodes];     for (int i = 0; i < hiddenNodes.length; i++) {         hiddenNodes[i] = new Node(i);     }      layers[0] = new Layer(inputNodes);     layers[1] = new Layer(hiddenNodes);     layers[2] = new Layer(outputNodes);  }  public void setInputs(double[] inputs) {     if (inputs.length == this.inputNodes.length) {         System.out.println(inputs.length);         for (int i = 0; i < inputs.length; i++) {             this.inputNodes[i].activation = inputs[i];         }     } }  public double[] getOutputs() {     double[] outputs = new double[this.outputNodes.length];     for (Node outNode : this.outputNodes) {         outputs[outNode.nodeNumber] = outNode.activation;     }     return outputs; }   }  class Node {  int nodeNumber; double sum; // z double activation; //Output double deltaNode; double gradient;   double[] outWeights;  public Node (int nodeNumber) {     this.nodeNumber = nodeNumber; }  public void setOutWeights(int noOfOutNodes) {     this.outWeights = new double[noOfOutNodes];     for (int i = 0; i < outWeights.length; i++) {         this.outWeights[i] = Math.random();     } }  public double sigmoid(double x) {     return 1 / (1 + Math.pow(Math.E, -x)); }   }  class Layer {  double layerBias; Node[] nodes;  public Layer (Node[] nodes) {     this.nodes = nodes; }   }  The error points at the line "layers[0] = new Layer(inputNodes);" in the NeuralNetwork class. No red is showing nor any warnings...  I assume it's an error from lack of knowledge on how the JVM works. Until now I've tried separating the classes into public classes in their separate files, which didn't help (wasn't expecting it to). I haven't tried anything else. Any thoughts? Thanks in advance!

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?


We know $e$ and $\pi$ are transcendental. Meaning that they aren't the solutions to any polynomial equation with coefficients that are integers. The next obvious question to ask - what about polynomials with coefficients that are rational numbers? Is there a name for such numbers? And has anyone proven that $e$ and $\pi$ don't belong to this family?   The next obvious extension is polynomials with coefficients that are algebraic numbers.   I assume all of these sets will be countable, so it's almost certain $e$ and $\pi$ won't belong to them. Is this a fair assertion to make?

Since $\pi$ and $e$ are transcendental, neither can be the root of a polynomial with rational coefficients. However, it is easy to construct a polynomial transcendental coefficients (with $\pi$ or $e$ as one of it's roots), namely $(x-\pi)$ and $(x-e)$. However, is it possible to construct a finite polynomial (one of whose roots is $\pi$ or $e$) with only algebraic coefficients? (i.e. something such as $y=x^5-(\sqrt 2 -1)x^2+x$ .) A polynomial with only radical coefficients would be the best.  P.S. The polynomial doesn't necessarily need to have BOTH $\pi$ and $e$ as it's roots, just one is interesting enough.


How do you find the coefficients for logistic regression?  Is it a case of just transforming the samples from the dependent variable and preceding to fit it like a linear regression?

I know I mess up different things. However I want to get better understanding what is motivation behind logistic regression.  $p(y_i=1|x_i)=(1+e^{-x_iw})^{-1}$  and according to OLS  $S(w)=\sum_{i}^{}(y_i-\hat{y_i})^2$,where $y \in \{1,0\}$.  What if $\hat{y_i}=p(y_i=1|x_i)$ and estimate $w$ by finding minimum to $S(w)$.  Why this is incorrect approach?


Are they somehow dangerous? What are they and how can I get rid of them?

I am in Portugal (Lisbon) at the moment, and when leaving my room late at night (12 pm ~ 04 am) I usually face about 4 of these arthropods in the corridors:    (For reference, the "line" in the image is a standard separation on the floor. This particular example of the animal is a little smaller than a nail.) They seem to have quite variable sizes and walk primarily on ground. Also, as implicit above, they seem to be active primarily during the late night. (I don't see them much often, if at all, during the morning/afternoon.) They can be quite fast, but if left unharmed do not move much. They also appear to take shelter inside the walls.  From what I searched, it seems possible that they are centipedes. I've seen sites saying that they are useful to keep other less pleasant animals at bay. My questions are: What are those animals, and should I leave them be or not?


The informal word for telling on people is "dobbing" (and we call that person a "dibber-dobber", at least here in Australia.   Is there an actual word for it?   Example: Sue went to my mother and told on me when I said that I was having an abortion. Sue is such a [insert word].

Some one who is not good at keeping secrets. In my native language it is called "chugalkhor" but it's a slang. So I can't translate it.  What do you call such a person who can't keep secrets because his instincts don't let him.


As I understand it, approval of edits now takes more than one reviewer.  I am a high rep user on  and thus, I often edit questions to improve them. Today I came across a question that needed editing. One low rep user had already proposed some edits. I approved these edits. But because I was the first reviewer, I could not then build on those edits to really polish the question. It seems that I have to wait for another reviewer to come along and approve the edits. This seems pointless.  Given that I am a high rep user I can in theory make any edits to the question without approval. Thus, I could choose to incorporate the proposed edits or not. Of course, general standards suggest that I should incorporate any reasonable edits already made. And I would typically do that. The important point however is that high rep users who have editing privileges should be able to edit a question immediately even if there are pending edits.   My feature request  High rep users should be able to edit a question that is under editing review and should be given the choice when pressing edit of    approving the edit under review immediately or  disapproving the edit under review.   (UPDATE) Alternatively a high rep user should be able to improve an edit after they have pressed "approve" and prior to the edit receiving sufficient approvals to be published.  Are there any reasons why this would not be a good idea? What do others think?

It's not consistent to leave an edit pending for approval (thus not making available for everyone else and locking its state) after a user who has those privileges have given his endorsement.   You could say why don't I improve the edit, but that makes no sense for something that is correct and it would not follow the "keep it simple" policy.  Update:  This is the current time line:   Someone who doesn't know about formatting makes a question. It's not legible A user without edit privileges amends the formatting. The correction is not visible, still not legible. I see the question and the pending revision and then cast my approval. It doesn't take effect yet, still not legible. Even for me if I didn't take care of copying the question source because it disappears from my own revision page!   I might agree that one's approval is indicative of both revision's quality and editor's competence. But we should retain that the main objective is to ask and answer questions. So, I propose this model:   Someone who doesn't know about formatting makes a question. It's not legible A user without edit privileges amends the formatting. The correction is not visible, still not legible. A user with edit privileges cast his approval. Revision takes effect. Although it keeps the pending approval (the Edit (1) button). If a second user with edit privileges cast a rejection, it also takes effect as a rollback.


public class Cart {      private String id;       private List<RentedMovie> rentedMovies = new ArrayList<RentedMovie>();       private long totalRent;      private long cartItemsCount;      public Cart(Cart sessionCart) {         this.id = sessionCart.id;         this.rentedMovies = sessionCart.rentedMovies;         this.totalRent = sessionCart.totalRent;         this.cartItemsCount = sessionCart.cartItemsCount;     }      ..<Getters and setters of all private varibles>.. }   I am little bit confused with my constructor concepts in java. In the above sample code, I have declared one Cart constructor which is having argument as Cart (that can be referring to another Cart object). As we can see in the sample class, all the instance variables are private, how can I able to access the private variables of Cart class via reference sessionCart directly. Ideally I should not be able to.   Please help.

In Java, are there clear rules on when to use each of access modifiers, namely the default (package private), public, protected and private, while making class and interface and dealing with inheritance?


I am trying to build an application for which i need to display number of check boxes that depends on the number of input.  For example: If user inputs 100, so i will create 100 check boxes.  Currently in example i am trying to make an array of JCheckboxes of fixed length. But it is giving Null Pointer Exception.  I need to store the value of check boxes because i will perform action accordingly whether a particular check box is selected or not after the user click Button.     JCheckBox [] chk=new JCheckBox[10];          for(int i=0;i<10;i++)          {              gbc.fill=GridBagConstraints.HORIZONTAL;              gbc.gridx=0;              gbc.gridy=i+1;              JCheckBox xp=chk[i];              jp.add(xp,gbc);          }     Exception in thread "main" java.lang.NullPointerException     at java.awt.Container.addImpl(Unknown Source)     at java.awt.Container.add(Unknown Source)     at UI.<init>(UI.java:93)


why is the prototype property of the instance throwing undefined?.  function Test(name){     this.name = name; }  Test.prototype = {     constructor: Test,     sayHello : function(){         console.log(this.name);     } }  var z = new Test("Hello");   console.log(z.prototype); //undefined console.log(zUtils.constructor); // Test   I am able to access the sayHello method via z.sayHello(), then why is my instance prototype returning me undefined instead of Test.prototype?.

I'm not that into dynamic programming languages but I've written my fair share of JavaScript code. I never really got my head around this prototype-based programming, does any one know how this works? var obj = new Object(); obj.prototype.test = function() { alert('Hello?'); }; var obj2 = new obj(); obj2.test();  I remember a lot discussion I had with people a while back (I'm not exactly sure what I'm doing) but as I understand it, there's no concept of a class. It's just an object, and instances of those objects are clones of the original, right? But what is the exact purpose of this ".prototype" property in JavaScript? How does it relate to instantiating objects? Update: correct way var obj = new Object(); // not a functional object obj.prototype.test = function() { alert('Hello?'); }; // this is wrong!  function MyObject() {} // a first class functional object MyObject.prototype.test = function() { alert('OK'); } // OK  Also these  really helped a lot.


How exactly do these kinds of compound words work?     "Okun's Law" and "Philips Curve" rather than "Okun Law" and "Philips' Curve"?   Is there any grammar book I can look for?

Possible Duplicate:     Which one is correct? I thought the latter would be correct but apparently the former is always used; why? Edit: Another (confusing) example:


I have my visa to a Schengen country from 20th October(Thursday), so I'm booking a flight with a transit at Abu Dhabi airport.  Would it be fine to board the plane on 19th Octobers at 22:00, or I can pass through immigration in India only if the Schengen visa is valid?

I have a question, I applied for the Schengen visa through Germany, on the form they ask me when I'd arriving (to Germany) and when I'd returning. they take this exact date as the visa period.  I wondering if they would let me get into the plane, even though my flight it a day before the arrival.  Let get the real deal; let say this:  My visa is valid from 02/12/2014 to 02/02/2015. But, my flight is scheduled to be departing on 01/12/2014, but entering Germany 02/12/2014. the flight duration is almost 9hours and there is 7hours difference between Germany and the departing flight country.


I am making a pie chart in Tikz. This is what it looks like so far:    The code is shown below:  \begin{tikzpicture}     \pie{ 2/Demonstration of Conservatism,6/Gross Premium Valuation (GPV),  1/Loss Ratio,86/Cash Flow Testing (CFT),1/Risk Theory Techniques, 4/Other} \end{tikzpicture}   The picture looks ok, but I feel like the labels are pretty cramped and it looks a bit ugly. Is there a better way to put the labels so they are more spaced out?

I want to create a pie chart with labels (one blank an one with percentage for the teacher, the mwe is the teachers version) so that my students have to fill the percentage in by themselves.  So far I created a pie chart using the code given in the answer here    and then I used labels from the code given in the answer here    Now I have this    The node in the violett part is the one I created manually and the other ones are implemented in the code, but I don't know what to change so that the automatic generated ones look like the one I created manually  My MWE      \documentclass[11pt]{article}   \usepackage{tikz} \usetikzlibrary{arrows}  \usepackage{xcolor}  \usepackage[utf8]{inputenc}  \definecolor{rosso}{RGB}{220,57,18} \definecolor{giallo}{RGB}{255,153,0} \definecolor{blu}{RGB}{102,140,217} \definecolor{verde}{RGB}{16,150,24} \definecolor{viola}{RGB}{153,0,153}  \makeatletter  \tikzstyle{chart}=[     legend label/.style={font={\scriptsize},anchor=west,align=left},     legend box/.style={rectangle, draw, minimum size=5pt},     axis/.style={black,semithick,->},     axis label/.style={anchor=east,font={\tiny}}, ]  \tikzstyle{pie chart}=[     chart,     slice/.style={line cap=round, line join=round, very thick,draw=white},     pie title/.style={font={\bf}},     slice type/.style 2 args={         ##1/.style={fill=##2},         values of ##1/.style={}     } ]  \pgfdeclarelayer{background} \pgfdeclarelayer{foreground} \pgfsetlayers{background,main,foreground}   \newcommand{\pie}[3][]{     \begin{scope}[#1]     \pgfmathsetmacro{\curA}{90}     \pgfmathsetmacro{\r}{1}     \def\c{(0,0)}     \node[pie title] at (90:1.3) {#2};     \foreach \v/\s in{#3}{         \pgfmathsetmacro{\deltaA}{\v/100*360}         \pgfmathsetmacro{\nextA}{\curA + \deltaA}         \pgfmathsetmacro{\midA}{(\curA+\nextA)/2}          \path[slice,\s] \c             -- +(\curA:\r)             arc (\curA:\nextA:\r)             -- cycle;         \pgfmathsetmacro{\d}{max((\deltaA * -(.5/50) + 1) ,1)}           \begin{pgfonlayer}{foreground}         \draw[*-,thin] \c -- (\midA:\r) node[above,near end, pos=\d,pie values,values of \s]{$\v\%$};         \end{pgfonlayer}               \global\let\curA\nextA     }     \end{scope} }  \newcommand{\legend}[2][]{     \begin{scope}[#1]     \path         \foreach \n/\s in {#2}             {                   ++(0,-10pt) node[\s,legend box] {} +(5pt,0) node[legend label] {\n}             }     ;     \end{scope} }   \begin{document}   \begin{tikzpicture} [     pie chart,     slice type={comet}{blu},     slice type={legno}{rosso},     slice type={coltello}{giallo},     slice type={sedia}{viola},     slice type={caffe}{verde},     pie values/.style={font={\small}},     scale=2 ]  \pie{Sommerjobs in Österreich}{52/comet,12/legno,20/sedia,16/coltello}   \legend[shift={(-1cm,-1cm)}]{{Eisverkäufer}/comet, {Schwimmbad}/legno, {Zettelverteiler}/coltello} \legend[shift={(1cm,-1cm)}]{{Kellner}/sedia}     \draw [*-,thin] (0.6,-0.2)  -- (0.7,-0.2 + 0.5ex) -- (2,0.5ex) node[above, near end]{20\%};    \end{tikzpicture}   \end{document}


I am using the Koma-script book class (scrbook) to draft a manuscript. The publisher has a very strict requirement on the margins of the pages.   I define the margins with the DIV command:  \documentclass[fontsize=14pt,a4paper,DIV=7,twoside,chapterprefix=on,draft]{scrbook}   This seems to work well for most of the document, except occasionally, there will be a word that goes over the margin. Is there a way to enforce strict guidelines about the margin?  Please see this screen-shot:     I tried reducing the font size by a couple of points, but it breaks the margins at other points:    I am using the microtype package, but it doesn't seem to eliminate all the over-runs.   Secondly, is there a way or a tool to automatically check to see if any part of the text, figures or tables have gone over a 3cm margin requirement? (My publisher seems to have an automated tool that marks the sections over the margin).

I often see output from TeX with the warning overfull hbox, badness 10000. What does this message mean?


I have to prove that the mapping $f(x,y) = {\displaystyle \sum_{i=1} ^ {n} }{ \displaystyle \sum_{j=1}^{n} }x_iy_j{f}(e_i,e_j)$  is a bilinear form, that is, inter alia, the condition: $f(x+y,z)=f(x,z)+f(y,z)$  I have: $f(x+y,z)=f\left({\displaystyle \sum_{i=1}^{n}}x_{i}e_{i}+{\displaystyle \sum_{k=1}^{n}}y_{k}e_{k},{\displaystyle \sum_{j=1}^{n}}z_{j}e_{j}\right)=f\left({\displaystyle \sum_{i=1}^{n}}{\displaystyle \sum_{k=1}^{n}}\left(x_{i}e_{i}+y_{k}e_{k}\right),{\displaystyle \sum_{j=1}^{n}}z_{j}e_{j}\right)=\ldots$  and what's next?  Help!

I have to prove that the mapping $f(x,y)={\displaystyle \sum_{i=1}^{n}}{\displaystyle \sum_{j=1}^{n}}x_{i}y_{j}{f}(e_{i},e_{j})$  is a bilinear form, that is, inter alia, the condition: $f(x+y,z)=f(x,z)+f(y,z)$  I have: $f(x+y,z)=f\left({\displaystyle \sum_{i=1}^{n}}x_{i}e_{i}+{\displaystyle \sum_{k=1}^{n}}y_{k}e_{k},{\displaystyle \sum_{j=1}^{n}}z_{j}e_{j}\right)=f\left({\displaystyle \sum_{i=1}^{n}}{\displaystyle \sum_{k=1}^{n}}\left(x_{i}e_{i}+y_{k}e_{k}\right),{\displaystyle \sum_{j=1}^{n}}z_{j}e_{j}\right)=\ldots$  and what's next?  Help!


I have seen this formula, but how to prove this? $$2\sum\limits_{k=1}^\infty \frac{H_k}{\left( k+1 \right)^m} =m\zeta \left( m+1 \right)-\sum\limits_{k=1}^{m-2}{\zeta \left( m-k \right)\zeta \left( k+1 \right)}$$

I found the following formula   $$\sum_{n=1}^\infty \frac{H_n}{n^q}= \left(1+\frac{q}{2} \right)\zeta(q+1)-\frac{1}{2}\sum_{k=1}^{q-2}\zeta(k+1)\zeta(q-k)$$  and it is cited that Euler proved the formula above , but how ?  Do there exist other proofs ?  Can we have a general formula for the alternating form   $$\sum_{n=1}^\infty (-1)^{n+1}\frac{H_n}{n^q}$$


I have this code
     ##QA##

     qqq

     qqq

     ##QA##
   There are newlines and indentations. This
\s*##QA##\s*<\/p> works for matichg
##QA##
  I would like to match content between both
##QA##
.  I tried this but it does not work
\s*##QA##\s*<\/p>(.*?)
\s*##QA##\s*<\/p>

For example, this regex  (.*)<FooBar>   will match:  abcde<FooBar>   But how do I get it to match across multiple lines?  abcde fghij<FooBar>


I have found this question in a book, but I don't know how to use that $\left\Vert P\right\Vert =1$.  Question: If $P\in\mathcal{L}(H)$ is a projection and $\left\Vert P\right\Vert =1$, show that $P$ is an orthogonal projection.  Where $\mathcal{L}(H)$ is the set of linear bounded operators on a Hilbert space $H$.  Thanks.

Let $T$ be a linear operator on a finite-dimensional inner product space $V$. Suppose that $T$ is a projection such that $\|T(x)\| \le \|x\|$ for $x \in V$. Prove that $T$ is an orthogonal projection.    I can't understand well. The definition of orthogonal operator is $\|T(x)\| = \|x\|$. But why that $\|T(x)\| \le \|x\|$ for $x \in V$ means orthogonal projection?


I was uninstalling python which probably removed other packages from that directory. When I reboot, it won't show Ubuntu logo while booting and I'm stuck at black screen which says one line starting /dev/sda9 and some blocks. I can get into tty1,tty2 and tty3 though. I tried sudo update but it gives 403 forbidden IP error

I am a new Ubuntu user running Ubuntu 13.04.  I've been trying to install and use a DeDRM tool, but I've been having problems doing so. I was following some directions that said I needed a version of Python 2.7, but not anything Python 3.0 or later (because 3.0 versions are missing some necessary libraries?). I tried to install Python 2.7.5.6, but it didn't work. I thought it was probably because I had the later version of Python, so I went through terminal and removed Python 3.3, so I could install the earlier version of Python.  Now that I've uninstalled Python 3.3, a lot of applications no longer work, including the terminal and the Ubuntu Software Center. I have no idea how to fix this problem now.


I have created a blog in blogspot. What I need to do is to write equation in the blog so adding  would be great to add in the blogspot.

I want to add  on my blog hosted on Blogger. The only solution I found is , but it requires a hosting server. Any other option?


I am looking for a short story I read online a few years ago, about artificial lifeform, with a hard sci-fi taste.  A couple of software engineers were trying to identify a strange program behavior on a new system in development, but digging through the outer layers of software source didn't explain the seemingly random issues they observed. After hours of debugging, they identified unexpected output at the compiler level.  One of the developers manages to craft a workaround, only to see additional issues appear around the fixes, and he begins to fear a backdoor might have been planted in the compiler, which seemed tainted much like the Ken Thompson hack. As this might eventually jeopardize the entire project, they spend more and more time on the issue itself, but as time passes, the deeper bugs they discover and fainter they become.  In the end, it seems like some artificial intelligence tried to emulate evolutionary pressure by establishing a form of communication channel, and having groups of humans around the world fixing the most obvious software outer layers. Even computer-assisted hardware design could be contaminated at this time, but in such complex a way they might go undetected for a long time, now adapted to the silicon environment.  I've been literally searching this story for months, and begin to believe I dreamt of it and should start writing myself.

I read this story a couple of years ago but can't seem to find it since.It's a short story.  The story starts with a programmer debugging a program and not being able to find the bug. Frustrated, he decides to disassemble the program and look at the assembly and found instructions that can't possibly come from the original source code. He then looks at the compiler for the source of the bug and even recompiles the compiler but the alien code still managed to make it into the program.  Then he decides to actually see what the alien code does and finds that it's trying to do something simple like adding two numbers but doing it in a completely non-intuitive way. He concludes that no human would do it that way and starts suspecting a virus.  Later he finds alien code everywhere from the compiler (not in the source of the compiler) to the assembler to the OS down even to the router in his office at which point he begins to suspect that the alien code may even be part or the CPU itself (modern CPUs after all are designed on computers).  The story ends with the programming team receiving a letter from another engineering team (I forget if it's Geneva or Tokyo or somewhere else) stating that they've found the same thing but every effort they've tried to publish their findings got censored by the emerging AI (hence the handwritten letter).


I am working on a WordPress plugin that will be accessible only to a group of a few selected website owners. I have installed my plugin to those sites already. There is active development going on for this plugin. And we need to upload changes to all the sites. Manually uploading the changes in all sites will be a tedious process. So I would prefer to upload changes to all of those websites at the same time.   How is this possible with WordPress?

If I write a private plugin, is there any way to use the WordPress auto-update mechanism to update it?  I want to encapsulate the functionality, but it's specific to my own 5 or so blogs, so it's not a good candidate for the public plugins resource. But I love the easy-updating mechanism.  Is there a way to do this?


I actually asked this question already once , but I marked it answered by mistake and it was also titled wrong. I wanted to ask where I went wrong in the following lines and what should be the correct way to arrive at the conclusion. I suspect its line 3. $$ GCD\bigl(( LCM(a,b) , LCM(a,c)\bigr)  \\\\=> a \times GCD\left( \frac{b}{GCD(a,b)} , \frac{c}{GCD(a,c)} \right) \\\\=> \frac{a \times GCD(b,c)}{GCD\bigl( GCD(a,b) , GCD(a,c)\bigr)} \\\\=> \frac{a \times GCD(b,c)}{GCD(a,b,c)} \\\\=> \frac{a \times GCD(b,c)}{GCD\bigl(a, GCD(b,c)\bigr)} \\\\=> LCM\bigl(a , GCD(b,c)\bigr) $$

I was doing this problem on , and as I was trying to simplify the formula, I arrived at the above conclusion. But now that I think of it, I actually arrived at that conclusion by mistake. Here are my workings. $$ GCD\bigl(( LCM(a,b) , LCM(a,c)\bigr)  \\\\=> a \times GCD\left( \frac{b}{GCD(a,b)} , \frac{c}{GCD(a,c)} \right) \\\\=> \frac{a \times GCD(b,c)}{GCD\bigl( GCD(a,b) , GCD(a,c)\bigr)} \\\\=> \frac{a \times GCD(b,c)}{GCD(a,b,c)} \\\\=> \frac{a \times GCD(b,c)}{GCD\bigl(a, GCD(b,c)\bigr)} \\\\=> LCM\bigl(a , GCD(b,c)\bigr) $$ I suspect that the third line is wrong since $GCD(hi,jk) != GCD(hj) \times GCD(ik)$. I know the final formula is correct since my submission was accepted. So what is the correct way to arrive at the conclusion?


Recently, my phone has started to vibrate shortly every few hours, as if to notify me of something. But when I check it, there aren't any (non-permanent) notifications. How to find out what/what app is causing this?

I have a Moto G6 Play that vibrates like it is getting notifications but it's not. The vibration is inconsistent and seems random so I would like to know if there is a logcat or something I can run to log which app is calling the vibration so that I can shut it off? The same thing happens on my wife's phone, same model, and it does my head in. The device is running Android 9.


If The Higgs boson and field ceased to exist (starting now), then would particles zip around at the speed of light, or would they gain mass from $E=mc^2$?  Or would something else happen?

Suppose you reset the parameters of the standard model so that the Higgs field average value is zero in the vacuum, what would happen to standard matter?  If the fundamental fermions go from a finite to a zero rest mass, I'm pretty sure that the electrons would fly away from nuclei at the speed of light, leaving positively charged nuclei trying to get away from each other.  Looking at the solution for the Hydrogen atom, I don't see how it would be possible to have atoms with zero rest mass electrons.  What happens to protons and neutrons?  Since only a very small part of the mass of protons and neutrons is the rest mass of the quarks, and since they're flying around in there at relativistic speeds already, and since the nuclear force is so much stronger than the electrical force with an incredible aversion to naked color, would protons and neutrons remain bound assemblages of quarks and virtual gluons?  Would they get a little larger?  A little less massive?  What would happen to nuclei?  Would they stay together?  If the protons and neutrons hold together and their properties change only some, then I might expect the same of nuclei.  Different stable isotopes, different sizes, and different masses, but I would expect there would still be nuclei.  Also the W and Z particles go to zero rest mass.  What does that do to the electroweak interactions?  Does that affect normal stable matter (outside of nuclear decay modes)?  Is the weak force no longer weak?  What happens to the forces overall?


In Python, can someone explain the difference between the use of "s" and "s[:]"? Here, "s" is a sequence type?  Examples:  s = [1,2,3]   s[:] = [1,2,3]   for i in s:   print(i)   for i in s[:]:   print(i)   Are there any differences?  I was thinking maybe the last example means "copy of s" which would allow for modifying s inside loop? What else?  Update based on answers  Thanks everyone. This shows the difference in a very concise way.  >>> s = [1,2,3]; t = s; s[:] = [2,3,4]; print(t) [2, 3, 4]  >>> s = [1,2,3]; t = s; s = [2,3,4]; print(t) [1, 2, 3]

I need a good explanation (references are a plus) on Python's slice notation.   To me, this notation needs a bit of picking up.   It looks extremely powerful, but I haven't quite got my head around it.


I want to rent a car. I want to hire a car. I want to take a car. ( Taxi )  What is the difference between these sentences in meaning? I need to say here I am not sure to have chosen the right word in the last sentence. Thank you do much in advance.

English not my native language. I'm trying to understand what would be correct in British English.  If I want to use a car for some time. I can say, "I want to rent a car". But from my knowledge there may be a  misunderstanding. I can say the same words if I want to give a car to someone to use for some time and I want to receive payment.  So what would be correct and not misunderstanding?   1) I want to use a car for some time = "I want to hire a car" 2) I want to give a car to someone to use for some time = "rent out a car"   Is my understanding correct?


I am at a new project, in which I will have stone walls with with text on them. Is there any easy way to get the writing look somewhat like this, without having to model every single letter like this?  I don't care for the font, but I do care for the triangular inset shape.    Any ideas on that would be more than welcome.  Thanks for reading.

How can I make a bevel, like in the "Gibson," for my personal inscription? Is there an automatic method to do so?


I have one Windows Server 2019 Essentials which logs errors and automatically shuts down because of license problems. It logs the following:  Bei der Überprüfung der Benutzeranzahl wurde eine Bedingung in der Umgebung festgestellt, die nicht mit der Lizenzierungsrichtlinie konform ist. Der Server erfüllt nicht die Microsoft-Software-Lizenzbedingungen. Diese erlauben maximal 25 lokale Benutzerkonten. Der Computer hat 29 lokale Benutzerkonten.  Didn't install that OS in German myself, but the last sentences actually simply mean that too many accounts are CREATED. It doesn't mean that too many accounts are concurrently connecting to the server or accessing it's services. And that's the point: Many of those accounts are only special users created for backup purposes or tests or alike. They are NOT all connecting to the server concurrently, most of those won't access any file or printer services ever at all. Reading about the user limits of that Win Server edition I had the impression that it's about concurrent usage by users, NOT the pure existence of a number of user accounts itself.  explicitly wrote so as well:  it's a 25 connected/logged in users limit.  Though, that doesn't seem to be the case and instead it seems that the number of available accounts itself, regardless of if and how they are used at all, is the limit already. So, what exactly does the 25 user accounts limit apply to? Thanks!

This is a  about Licensing.    Questions on licensing are off-topic on Server Fault.  If your question has been closed as a duplicate of this question, then this is because we want to help you understand why licence questions are off topic rather than just telling you "it just is". In all likelihood, this question will not address your question directly, it was not meant to.    I have a question regarding software licensing. Can the Server Fault community please help with the following:   How many licenses do I need? Is this licensing configuration valid? What CALs do I need to be properly licensed? Can I run this product in a virtual environment? Can I downgrade this product to an earlier version? Am I entitled to feature X with license Y?


From what I know, given some argument, the argument is valid when it has true premises that lead to a true conclusion. Now, what if the premises were false? I mean, the conclusion would be vacuously true, but does that make the argument valid? It sounds rather odd, since taking the argument to be valid is essentially accepting some ridiculous statement. But I don't know, I'm just a bit confused.

Am unsure (leaning more towards no): true P and true C is valid, false P and false C is valid, True P and false C is invalid, how about false P and true C?  P= Premises; C= Conclusion.  People who says.. Yes, it is valid, I would like to hear some answers for   How can we derive the truth out of falsehood?  If we can, then True P - False C is valid too (tell me why it is invalid?).


I am downloading Ubuntu 16.04.2 LTS when I click on download, then it's shows "amd64"  somewhere in the name of file like "ubuntu-16.04.2-desktop-amd64.iso"  , What does it mean? Is this not for Intel processors?

When I go to the downloads page to get Ubuntu, it automatically downloads the AMD version, but my computer has no hardware with AMD on it. I only have Intel and Nvidia. Also, when I install this AMD version on my computer, it works (other than the constant random freezing of the computer when I use Ubuntu). I don't really understand why the amd version works on a computer with an intel processor.


I am currently using 13.04. Till 12.10 in file browser (nautilus) pressing any key press will select the directory starting with that key. For example when i do the below   Opening a nautilus  Press D (all folder that starts with D will be selected and not the subfolders)   Whereas in ubuntu 13.04 it searches all the folders in the current directories and in sub directories too.   Is it possible to restrict the search only to current directories by any configuration. Thanks for your guidance.

Is there a way to set the new Nautilus in Ubuntu 13.04 to have an old behaviour I liked, namely:   Type something An item matching that name will be selected (pretty much like using the Tab key in a terminal)   This used to be virtually instant and quite convenient, but now it does a deep search across a variety of parameters when you start typing.   The deep search is useful, but by far the more frequent task is to select something within the current directory by name, which the old function satisfied perfectly.  Is there a way to restore this behaviour? I couldn't find an option in Preferences.  If possible, I'd like to avoid a roll-back as I hate to fight progress, but if that's the only option I'll take it.


How can I install WxPython offline on my Ubuntu 13.04.

I could not install my modem driver so I have to update and install applications offline. For this I want to use keryx but to install keryx, Python and wxPython have to be installed first. So how do I install Python and wxPython offiline on Ubuntu 13.04?  Note : I don't have internet connection in Ubuntu. So I'll have to download the required file from my Windows 7.


Determine all functions $f(n)$ from the positive integers to the positive integers which satisfy the following condition: whenever $a,b,$ and $c$ are positive integers such that $\frac{1}{a} + \frac{1}{b} = \frac{1}{c}$ then $\frac{1}{f(a)} + \frac{1}{f(b)} = \frac{1}{f(c)}$.    Attempt  We want to find the form of $f(n)$. Notice that if $n$ is a positive integer, then the only possible solution to  $$ \frac{1}{a} + \frac{1}{b} = \frac{1}{n} $$ is only $a=b=2n$.  So we must only have that  $$ f(n) = \frac{f(2n)}{2}$$  If $n=1$ then $2f(1) = f(2)$, if $n=2$ then $2f(2) = f(4)$. $n=3$ then $2f(3) = f(6)$.  $$ f(1) = f(2)/2 $$ $$  f(2) = f(4)/2 $$ $$  f(3) = f(6)/2 $$ $$  f(4) = f(8)/2 $$ $$ f(5) = f(10)/2 $$ $$ \vdots $$  From here we can easily see that $$ f(1) =  \frac{f(2)}{2} = \frac{f(4)}{2^{2}} = \frac{f(8)}{2^{3}} = ... $$  So we have $f(2) = 2f(1), f(4) = 4f(1), f(8) = 8f(1), ...$  $$ f(2^{k}) = 2^{k} f(1)...$$  then also $f(3) = f(6)/2 = f(12)/4 = f(24)/8 = …,$ which means  $$ f(3 \times 2^{k}) = 2^{k} f(3)  $$

Find all functions $f: \mathbb{N} \rightarrow \mathbb{N} $ satisfying $\frac{1}{f(a)}+ \frac{1}{f(b)} = \frac{1}{f(c)} $ whenever $\frac{1}{a}+ \frac{1}{b} = \frac{1}{c} \ a,b,c \in \mathbb{N} $   After talking through it with a friend, they believe there is a simple solution only a couple of lines long, but I have yet to spot the method. Any ideas?


I just added a repeating command block to an adventure map(1.15.2) I've been working on for awhile. It's purpose was to detect a falling player and then to tp them approximately 300 blocks away. I got distracted and ended up turning it on with a command along the lines of "execute if @p at @p run tp 20 70 200" This causes me to tp to the location whenever the block region containing the command block is loaded. My question is has anyone got any ideas of possible ways to solve this? I know the general location but cannot use the fill function as the blocks aren't loaded. And states this when executed Gamerule commandblockoutput false doesn't help And it registers me in spectator mode and still tp back.

I set a command block to /tp. It was supposed to activate only if you had 0 time left, and to activate the command block with a hopper clock to keep giving it power.   But it is not checking if you have 0 time left, so it keeps teleporting me. I can't get close enough to the command block to break it, so I'm stuck in a neverending teleport loop.  Any ideas?


I realize that I can block an employer from contacting me. I have done so.  However, I'd like a way to report simply unfair use of the Careers systems. I received a poorly targeted recruitment attempt, I responded "Not Interested" and have received multiple followups "Can I just have a quick phone call to describe the roll..." "I'd love to tell you more..." etc.  After the second one, I found the "Block Employer" button. However, does this get any attention from the Careers site, in general? Is there any precedence for having your Careers account suspended because too many candidates have blocked you?  I'd like there to be a "Report Harassment" feature.

I just got my first offer through careers.stackoverflow.com.  The offer was for places other than the ones listed in my "Where do you want to work?".  This is one of my pet peeves.  There needs to be an easy way to flag employers as not following the rules.


I have a javafx application that I packaged and installed on my pc.  The first launch of the application is working fine.  If I keep the application running, is there a way to handle the second launch of application to show the first one like skype for example ?  Thank you so much in advance  Update:  I tested the ManagementFactory example, it's only working on the IDE (I'm using netbeans) but when the application is installed(Windows 8), the class name and the command line are empty ! So the comparison is not good.  For the file locking, I'm already using this approch for protecting a file when the application is launched but it does not throw an exception when launching the second instance ! (Besides, on Oracle forum , they said if there is a power cut, the file will be still locked).  For server socket, I think it's not a good approch because it's a desktop application, so I can't guess which port is not used !

Sometime I see many application such as msn, windows media player etc that are single instance applications (when user executes while application is running a new application instance will not created).  In C#, I use Mutex class for this but I don't know how to do this in Java.


I'm quite new to Linux so could do with a little help.  If there a way to make this work for all subdirectory contents rather than just the current directory?  for f in *\ *; do mv "$f" "${f// /_}"; done

How do you rename all files/subdirs in the current folder?  Lets say, I have many files and subdirs that are with spaces and I want to replace all the spaces with an underscore.  File 1 File 2 File 3 Dir 1 Dir 3   should be renamed to  File_1 File_2 File_3 Dir_1 Dir_3


In AL, if I understand correctly, you can only build your character with 2 books, a PHB and another. If you picked VGM to choose, say, a Firbolg race, then you can't take subclasses from XGtE.  Does that mean that you also can't take spells from that book? You'd only have access to PHB spells?

In Adventurer's League, you can use the Core PHB and one additional source to create your character.  This is clearly stated applying to races and sub-classes (so you can't have a Purple Dragon Knight Goliath, because two separate books), but does it apply to Spells?  Specifically, If I build a High Elf Fighter, and I choose Green Flame Blade as my High Elf cantrip, am I locked into using Sword Coast Adventurer's Guide as my single additional source?


I have $f(x) = x^3 - x + 1$ and $g(x) = x^3 - x - 1$, which are irreducible in $\mathbb Z_{3}[x]$, and the finite fields $\mathbb{Z}_{3}[x] /(f(x)) $ and $ \mathbb{Z}_{3}[x] /(g(x))$. I'm trying to prove that there is a root for $f(x)$ in $\mathbb{Z}_{3}[x] /(g(x))$, but I don't seem to find it.  My strategy has been trying to find a root of the form $a + b\beta + c\beta^{2}$, with $a,b,c \in \{0,1,2\}$ knowing that $\beta$ is the root of $g(x)$ in $\mathbb{Z}_{3}[x] /(g(x))$, but I have failed so far. Any suggestions?

So I want to find the isomorphism $\phi$ that takes $F = \mathbb{Z}_3/\langle x^3 - x - 1\rangle$ to $E = \mathbb{Z}_3/\langle x^3 - x + 1\rangle$.  I understand that these are both finite fields of size 3^3 since $x^3 - x - 1$ and $x^3 - x + 1$ are both irreducible polynomials of degree 3.  I feel like a good start would be to take the subfield $\mathbb{Z_3}$ in $F$ to the subfield $\mathbb{Z_3}$ in $E$.  Or maybe find the right generator of each multiplicative group of size $3^3-1$ of each field and send those to each other.


Today I had to configure some CISCO switches & routers at school, and I used a USB to serial adapter. Unlike on Windows I didn't have to install any drivers; it was recognized immediately.   When I open puTTY through GUI and tried serial /dev/ttyUSB0 I got the following error:  Unable to open connection to /dev/ttyUSB0 Unable to open serial port   I thought I'd give it a try with root permissions sudo putty and it worked, but why!?  If I do have to give root permissions to puTTY what would be the way to do it? I read gksudo is removed from 18.04 and running an app as sudo <> is not recommended.  Thanks in advance!

I have an Ubuntu 11.10 system with 2 users:   The first was created during the installation The second instead was created after. It belongs to the sudoers group.   Now the problem is that when the second tries to use a device ttyUSB0 the following error is returned:  "Could not open serial port /dev/ttyUSB0"   I was able to fix it by using:  sudo chown :second_user /dev/ttyUSB0   However when I disconnect the device and reconnect it the problem comes back.  Is there a way to allow different users to access the devices? I suppose I have to add the user to a specific group. Currently the owner is root and the group is dialout. However I'm not sure about the group and I don't know how to add the user.  Thanks!


I signed up for stack exchange about a year and a half ago, and have it signed in on my phone and can (clearly) ask questions. I want to sign in on my laptop, but it keeps saying that there is no account under any of my e-mail addresses, and none of the external sign ins are associated with my account. Is there any way I can get into my account, or an I just going to have to start over?

I forgot what email I used for my other ploxtic id: how do you find out what my email was?   The account is user:2078229.


Is it possible to pass the template-parameters to a function somewhere else defined? For instance I have the class  Barrier.pp  template<Location L, Knock K> class Barrier {   //...   void checkBarrier( ... )   {     BarrierBest_checkBarrier<L, K>( ... );   }   //... }   Other.cpp  template<Location L, Knock K> BarrierBest_checkBarrier( ... ) {   //Use L and K to do call other function }   As I have it right now the compiler throws a unresolved external symbol for all the possible combinations of the template parameters, that is, BarrierBest_checkBarrier<1,1>, BarrierBest_checkBarrier<1,0>, BarrierBest_checkBarrier<0,1>, BarrierBest_checkBarrier<0,0>  Is there a way to make this work?

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


I want to set the default permissions for newly created directories to have r-x for others and those of newly created files (non-directory files) to have ---.  If I set the umask to 2, directory permissions get r-x but files' get r--.  I couldn't find any way to achieve what I want with umask.  Ultimately, I want others to be able to traverse the directories but not to read the content of the files. I think that is a very reasonable demand but eventually there seems to be no such setting.

In my CMS, I noticed that directories need the executable bit (+x) set for the user to open them. Why is the execute permission required to read a directory, and how do directory permissions in Linux work?


I denote with $\pi_{i}$ i-homotopy group. If I have $X,Y$ CW-complex and $\pi_{i}(X)=\pi_{i}(Y)$ for all $i$. Can I say that $X$ and $Y$ are homotopic equivalent? What type of equivalence is it?

Since it's fairly easy to come up with a two spaces that have different homotopy groups but the same homology groups ($S^2\times S^4$ and $\mathbb{C}\textrm{P}^3$). Are there any nice examples of spaces going the other way around? Are there any obvious ways to approach a problem like this?


Is it possible to get the file name of the most recently created one in a given directory? I wanted to use  but I realized glob can't sort anything. Can I sort the files and then use glob to get the names? How do I do the first step of sorting files by time created?  By the way, I'm working on a centos 7 machine.

What is the best way to get a list of all files in a directory, sorted by date [created | modified], using python, on a windows machine?


I have a Google Sheets where I enter all the results of my beer pong matches with friends. I'd like to see my amount of wins/losses with certain friends. This can be done with   =IF(AND(B2="Won",E2="Stefan",1,0)   Above code adds one point to a cell if I won with the teammate - adds 0 if not. However, so far I have 25 recorded matches, and the list will keep getting new rows. I don't want a column that calculates wins and losses, because I'd like to be able to see my score with up to 10 different people - it'd be too many columns. I'd much rather have the amount of wins and losses in 2 singular cells. I could write the above code into a single cell for each row, but that'd take too much time. I need something similar to:  =IF(AND(B2:B25="Won",E2:E25="Stefan",1,0)  But this above code checks if ALL the rows are equal to "Won" or "stefan". I need it to check the if statement for each row, and then add 1 point for each row that resulted in TRUE.  Anyone knows what I'm looking for?

I have a spreadsheet document with a formula comparing a list of URLs to lists on two other sheets within the document.  I desire to know if each URL on the first list is present on the blocklist, whitelist, both, or neither.  Note that I have used named ranges on all three URL columns (minus the header, e.g. 'sheetname'!A2:A1000').  Here is my current formula:  =if(len(REQUESTS),if(AND(countif(BLOCK,REQUESTS),countif(WHITE,REQUESTS)),"ON BOTH",if(countif(BLOCK,REQUESTS),"Blocked",if(countif(WHITE,REQUESTS),"Whitelisted","Pending addition to a list"))),"")   This works as expected, except that I need to drag it down to each row in the sheet containing the requests.  When I add it to an ARRAYFORMULA, the AND no longer works. Any URL present in both BLOCK and WHITE returns "Blocked".  =ARRAYFORMULA(if(len(REQUESTS),if(AND(countif(BLOCK,REQUESTS),countif(WHITE,REQUESTS)),"ON BOTH",if(countif(BLOCK,REQUESTS),"Block",if(countif(WHITE,REQUESTS),"White","Pending addition to a list"))),""))  Actual location(s)  Working formula               With ARRAYFORMULA neither             Pending addition to a list    Pending addition to a list white               White                         White block               Block                         Block BOTH                ON BOTH                       Block   If it helps, when I swapped the if(White) and if(Block), I get "White" when it is on both.  Any ideas why the addition of ARRAYFORMULA breaks my logic, or an alternative method of getting the formula to repeat as needed?


I have a directory that contains quite a lot of files with names made up of artirst's name and album e.g.:   Now the task is to go through each of the files, create a directory named after artist's name and album the file's name, and move the file into that directory.  The final structure should look like this:   how would I go about doing this with only basic shell commands?

I need to move files by reading their names. I have to move system generated files and the names include a time stamp. I need to move the files by reading the file name by month.  If the file name contains 201601*.txt, then move to 2016/January directory. If the file name contains 201602*.txt then move to 2016/February directory etc.


The momentum operator is usually defined as  $$\hat p = -i \hbar \frac d {dx}$$  The eigenfunctions of this operator are plane waves  $$\tag{1} \label{1} \psi_p(x) = A \exp\left(\frac{i p x}{\hbar}\right)$$  and they are not square-integrable, i.e.  $$\int_{\mathbb R} | \psi_p(x)|^2 dx = \infty$$  therefore, it is usually said that a free particle with a well-defined momentum is a physical impossibility.  But we have considered a case in which the wavefunction $\psi$ can extend from $-\infty$ to $\infty$. In general, the wavefunction $\psi$ should satisfy the following conditions:  $$\tag{2} \label{2} \psi \in C^0 (\mathbb R)$$ $$\tag{3} \label{3} \int_\mathbb{R} | \psi(x)|^2 dx = 1$$  In the case of an infinite square-well potential  $$V(x) = 0 \ \ \ \text{if} \ x \in [0,L]$$ $$V(x) = \infty \ \ \ \text{if} \ x \notin [0,L]$$  we usually require that   $$\tag{4} \label{4} \psi(x) = 0 \ \ \ \text{if} \ x \notin [0,L]$$  so that \ref{2} implies  $$\tag{5} \label{5} \psi(L)=\psi(0)=0$$  But by applying \ref{5} to \ref{1}, we obtain  $$\tag{6} \label{6} e^{ipL/\hbar}=1=0$$  which is clearly absurd and cannot be valid.  However, in  the authors introduce a self-adjoint extension of the operator $\hat p$ (which they call $P_\theta$) by replacing \ref{5} with  $$\tag{7}\label{7} \psi(L)=e^{i \theta} \psi(0)$$  from which they obtain the "momentum eigenfunctions"  $$\tag{8} \label{8} \phi_n(x,\theta) = \frac 1 {\sqrt{L}} \exp \left(2 i \pi \nu \frac x L \right), \ \ \ \nu = n + \frac{\theta}{2 \pi}, \ \ \ n \in \mathbb Z$$  They conclude with the remark     For a particle in a box, it is often argued that the “physical” wave   function should continuously vanish on the walls $x = 0$ and $x = L$,   ensuring that the presence probability vanishes continuously for $x ≤0$   and for $x ≥ L$. One should realize that the continuity of the   measurable quantity      $$ Pr(0 ≤ x ≤ u) = \int_0^u |\phi(x)|^2 dx, \ \ \ u \in[0,L] $$ is   ensured as soon as the integral $\int_0^L |\phi(x)|^2 dx $ does   converge and does not require any continuity property of $\phi(x)$.   Specializing this remark to the eigenfunctions of $P_\theta$ we   observe that $|\phi_n(x,\theta)|^2$ does not vanish continuously at $x=0$   but nevertheless the physical quantity $$Pr(0 ≤ x ≤ u) = \frac{u}{L}$$ vanishes continuously, as it should, for $u \to 0$.   They also say that the Heisenberg inequlity is not valid for the "momentum eigenfunctions" of Eq. \ref{8}, and indeed we would obtain  $$\sigma_p = 0$$ $$\sigma_x = \frac{L}{\sqrt {12}}$$   From a mathematical point of view, their reasoning is more or less clear to me: if we replace \ref{5} with \ref{7} and restrict ourselves to the interval $[0,L]$, it is possible to extend the momentum operator, making it self-adjoint, and to introduce eigenfunctions for this extended version. But is this reasoning physically meaningful?   In particular, what about the value of the wavefunction outside the interval $[0,L]$? Also, what about the Heisenberg inequality? Is the fact that it is not valid acceptable from a physical point of view?    Update  I don't understand if the authors are implying that the wave function is set to $0$ for $x \notin [0,L]$; if this was the case, shouldn't we have the problem that $Pr(0\leq x \leq u)$ is discontinuous at $u=L$?

Let a (free) particle move in $[0,a]$ with cyclic boundary condition $\psi(0)=\psi(a)$. The solution of the Schrödinger-equation can be put in the form of a plane wave. In this state the standard deviation of momentum is $0$, but $\sigma_x$ must be finite. So we find that $\sigma_x\sigma_p=0$. Is something wrong with the uncertainty principle?


Pages showing on a web server have been replaced with this: are there any particular reason on a LAMP stack server that's showing this?   �R���Mz�Ə�7)nҀ���� lEGy�l��:̑�I���o�B����S%|��Е�sTu�le���b�A}A�����ʹ�1��0�A{�K��ʘӺ�tj����dLI=r�   �PRg����_Lb�R��� Ş�l?�␔�)!��[��F��o��wi&k^�CV(t@p�W2����{h�x�H�GRn�͉�eCb�xԉ����6G�������Q��d27\�ثd�S��=\�F�f*�0�ۣ�OP���5(r�ZߙxQ�Z>�~G�Ae

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


I am seeing mixed answers on other posts so I thought I would ask here.  Is there a way to automate the raster calculator?    I am trying to create a series of inundation maps at fine increments.  It is tedious to do manually, so I would like to write a script that will loop the raster calculator.

I am getting a not executed error for a raster calculator.   Here is part of the output:     File "C:\projectTemp\FloodAnalysis\floodxsectionanalysis.py", line   107, in makeSeemless            arcpy.gp.RasterCalculator_sa(Con(IsNull(rasterIn), FocalStatistics(rasterIn,NbrRectangle(3, 3), "MEAN"), rasterIn),   "{0}yrSeemless.img".format(increment))   File "C:\Program Files   (x86)\ArcGIS\Desktop10.2\arcpy\arcpy\geoprocessing_base.py", line   498, in        return lambda *args: val(*gp_fixargs(args, True)) arcgisscripting.ExecuteError: ERROR 000539: Parsing error SyntaxError:   invalid syntax (line 5) Failed to execute (RasterCalculator).   This code I have setup to put into this calculator is:  def makeSeemless(outputPath, increment, rasterIn):     arcpy.gp.RasterCalculator_sa(Con(IsNull(rasterIn), FocalStatistics(rasterIn,NbrRectangle(3, 3), "MEAN"), rasterIn), "{0}yrSeemless.img".format(increment))


Today a letter have appeared in my mailbox in the USA. From what I understand, it is a traffic ticket, from Germany. I just want to know if traffic tickets can be enforced to US Authorities.

Yesterday, 2 pieces of paper have appeared in my mailbox in the USA. From what I understand, it is a traffic ticket, from Germany from Summer trip, which found its way to my address in the USA.  I do not recollect any violations, however the license plate number looks legit; Date and time look legit as well. The image of the driver is, however, too blurry to recognize.  Does the traffic ticket look legitimate? I was not able to find an image of German traffic tickets online.  I would like to be a good guest, and pay it. What are my options? Wire transfer is $50, for a EUR10 fee this is ridiculous.   I was able to locate this site:  Is it legit?


In this story magic is done by writing command-line sort of programs.  In the story the main guy ends up using some magic and ends up making his grandmother or something mad and ends up in hiding.  The whole story ends up with their “familiars”, constructs or AI's that they have created, kinda rebelling.  The main character's name was something like Raven.  There are a couple of characters that are semi-related to some greek mythology gods, but i can't think of which.  Oh, the main character and his family are gods, or something like that, and that's why they can do magic.

I recall being somewhat impressed by a novel I read a few years back – this book may be less than five years old – which featured a college-aged man.  He had a laptop which transformed into a troll goblin that served as his familiar.  In the story's universe, mages had switched to the Internet for most of their magic & communication.  The main character was essentially a magical hacker, and spent much of the book fighting against his evil aunt (I think, I know it was a female relative) with the help of his cousin.  Older forms of magic were also featured, including using special paintings as magical portals, and spells being whistled by wizards.  It features a scene at a gas station where the laptop is disabled by a virus, and the main character whistles a spell to reanimate dinosaurs from the gasoline.  Is this ringing any bells?


The current Ubuntu 20.04 behavior for "Open With Other Application" seems to work differently on the Desktop compared to Files/Nautilus. Example: I configured VS Code IDE to be the default app for text/plain mime type (~/.config/mimeapps.list): [Default Applications] text/plain=code.desktop  Now, a right click -> Open with Other Application on a file foo.bat from the Desktop opens gedit without prompt, Open does not have any effect. If I choose Show in Files, and do the same sequence, it works as expected - Open will directly open in VS Code, Open With asks for the application. I don't really understand this behavior. How can I make Ubuntu behave the same way, regardless the environment, where the file is executed? PS:  This issue is reproducible with other applications.

In Ubuntu 20.04, on the desktop, there is a number of actions I wish I could do, such as, by order of importance :  use keyboard shortcuts such as select all, copy / paste. use drag & drop with icons deactivate the "mouse over" highlight, and restrict the clicking area to only the icon, not the surrounding square  To put it simply, I'd like to have the exact same features as offered by the desktop of Ubuntu 18.04 (probably related to a specific version of GNOME, and not Ubuntu itself). Am I missing something obvious here? I actually see no reason why those actions are removed or deactivated on the desktop, since they all work in any Nautilus window.


Needing to download 'traceroute' for some work that I have to do, I tried to download the package using 'sudo apt-get install'. After looking online, I saw that I might have to update the software but that didn't work either. Any ideas?  ubuntu@ubuntu:~$ sudo apt-get install traceroute Reading package lists... Done Building dependency tree        Reading state information... Done Package traceroute is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'traceroute' has no installation candidate  ubuntu@ubuntu:~$ sudo apt-get install update Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package update   P.S. inetutils-traceroute is not working, therefore I need another answer to be able to download the package.

I'm getting this:  atul@ubuntu:~$ sudo apt-get install traceroute [sudo] password for atul:  Reading package lists... Done Building dependency tree        Reading state information... Done Package traceroute is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'traceroute' has no installation candidate   Can any one tell me how to solve this problem?


I have a 500Gb HDD hard disk in my Laptop, and I want to sell it, so I am asking if I can format it such that no one can recover my old  data, and if yes, How can I do that?  Thanks in advance

I'm planning on selling a USB external hard drive that currently contains an old Ubuntu installation with stored passwords and banking information.  How can I securely erase the drive before selling it?


I am new to Java and I am trying to code a calculator. The numbers are not calculating and I am not sure why that is happening.  Here is my code:  import java.util.Scanner;  public class Calculator {     public static void main(String[] args){          System.out.println("Type in any 2 numbers: ");         Scanner math = new Scanner(System.in);         int number = math.nextInt();         int num2 = math.nextInt();          System.out.println("Which operation would you like to use? (+,-,*,/)");         String oper = math.next();          if (oper == "+"){             int total = number + num2;             System.out.println(total);         }         else if (oper == "-"){             int total = number - num2;             System.out.println(total);         }         else if (oper == "*"){             int total = number * num2;             System.out.println(total);         }         else if (oper == "/"){             int total = number / num2;             System.out.println(total);         }     }  }

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


The problem comes from a problem sheet of an introductory math course by Oxford. It is question 1 in . I don't study there I'm just curious and want to try. Given $n$ positive numbers $x_1, x_2,\ldots,x_n$ such that $x_1+x_2+\ldots+x_n\le 1/3$, prove by induction that $$(1-x_1)(1-x_2)\cdot\ldots\cdot(1-x_n)\ge 2/3.$$ My attempt: For $n=1$, $$x_1\le1/3$$ $$-x_1\ge-1/3$$ $$1-x_1\ge1-1/3$$ $$1-x_1\ge2/3$$  (Incorrect) Assume $(1-x_1)(1-x_2)\cdot\ldots\cdot(1-x_k)\ge2/3$ for some $k$. For $n=k+1$, $$ \left\{  \begin{array}{c} x_1+x_2+\ldots+x_k\le1/3\qquad(1)\\  x_1+x_2+\ldots+x_k+x_{k+1}\le1/3\qquad(2)  \end{array} \right.  $$ $(2)-(1):$ $$x_{k+1}\le0$$ $$-x_{k+1}\ge0$$ $$1-x_{k+1}\ge1$$ Then$$(1-x_1)(1-x_2)\cdot\ldots\cdot(1-x_k)(1-x_{k+1})$$ $$\ge2/3\cdot1$$ $$\ge2/3$$ But it looks like a paradox because $(1)$ and $(2)$ can't be true at the same time. For $n>1$, I cannot make the given inequality into the desired one. They are just not equivalent.  I'm looking for a hint. Sorry but I think they are not grading it now. Thank you. Edit: Reply to Kavi Rama Murthy: When $n=2$, $$x_1+x_2\le1/3$$ $$1-x_1-x_2\ge2/3$$ Then $$(1-x_1)(1-x_2)=1-x_1-x_2+x_1x_2$$ $$\ge(2/3)+x_1x_2$$ $$\ge2/3$$ For $n=k+1$, given that $$x_1+x_2+...+x_k+x_{k+1}\le1/3$$ and apply the $n=k$ case with $x_1,x_2,...,x_k+x_{k+1}$, $$(1-x_1)(1-x_2)\cdot\ldots\cdot(1-x_k-x_{k+1})$$ $$=(1-x_1)(1-x_2)\cdot\ldots\cdot[(1-x_k)(1-x_{k+1})-x_kx_{k+1}]\ge2/3$$ Then $$(1-x_1)(1-x_2)\cdot\ldots\cdot(1-x_k)(1-x_{k+1})\ge2/3+x_kx_{k+1}(1-x_1)(1-x_2)\cdot\ldots\cdot(1-x_k)$$ $$\ge2/3$$ Reply to ΑΘΩ:  (Replaced with the empty $I$ case) When $I$ has $1$ element, $${\displaystyle \prod_{i\in I}^{1} (1-x_i)}=1-x_i\ge1-{\displaystyle \sum_{i\in I}^{1} x_i}$$  When $I$ has $0$ element, $${\displaystyle \prod_{i\in I}^{0} (1-x_i)}=1$$ Looking at RHS, $$1-{\displaystyle \sum_{i\in I}^{0} x_i}=1$$ Then $${\displaystyle \prod_{i\in I}^{0} (1-x_i)}\ge1-{\displaystyle \sum_{i\in I}^{0} x_i}$$ Assume ${\displaystyle \prod_{i\in I}^{k} (1-x_i)}\ge1-{\displaystyle \sum_{i\in I}^{k} x_i}$. When $I$ has $k+1$ elements, $${\displaystyle \prod_{i\in I}^{k+1} (1-x_i)}$$ $$=(1-x_{k+1}){\displaystyle \prod_{i\in I}^{k} (1-x_i)}$$ $$\ge(1-x_{k+1})(1-{\displaystyle \sum_{i\in I}^{k} x_i})$$ Looking at RHS, $$1-{\displaystyle \sum_{i\in I}^{k+1} x_i}$$ $$=1-{\displaystyle \sum_{i\in I}^{k} x_i}-x_{k+1}$$ $$=1-x_{k+1}-{\displaystyle \sum_{i\in I}^{k} x_i}$$ $$=(1-x_{k+1})(1-\frac{{\displaystyle \sum_{i\in I}^{k} x_i}}{1-x_{k+1}})$$ Since $1\ge1-x_{k+1}$, $$1-\frac{{\displaystyle \sum_{i\in I}^{k} x_i}}{(1)}\ge1-\frac{{\displaystyle \sum_{i\in I}^{k} x_i}}{(1-x_{k+1})}$$ $$(1-x_{k+1})(1-{\displaystyle \sum_{i\in I}^{k} x_i})\ge(1-x_{k+1})(1-\frac{{\displaystyle \sum_{i\in I}^{k} x_i}}{1-x_{k+1}})$$ $${\displaystyle \prod_{i\in I}^{k+1} (1-x_i)}\ge1-{\displaystyle \sum_{i\in I}^{k+1} x_i}$$ In the problem, given ${\displaystyle \sum_{i\in I}^{k+1} x_i}\le1/3$, $${\displaystyle \prod_{i\in I}^{k+1} (1-x_i)}\ge1-(1/3)$$ Then $$(1-x_1)(1-x_2)\cdot\ldots\cdot(1-x_k)(1-x_{k+1})\ge2/3$$

Let $(a_n)_{n \in \mathbb{N}}$ a sequence of real numbers with $0 \leq a_n \leq 1$ for all $n \in \mathbb{N}$.  I want to prove the following inequality using mathematical induction:  $\prod \limits_{k=0}^{n}(1-a_k) \geq  1- \sum\limits_{k=0}^{n}a_k$.  It's obviously true for $n=0$.  $n \rightarrow n+1$  Assume that it's true for n. Then one has:  $\prod \limits_{k=0}^{n+1}(1-a_k) = (1- a_{n+1}) \prod \limits_{k=0}^{n}(1-a_k) \geq (1- a_{n+1}) (1- \sum\limits_{k=0}^{n}a_k) = 1- \sum\limits_{k=0}^{n}a_k - a_{n+1} + a_{n+1} \sum\limits_{k=0}^{n}a_k = 1- \sum\limits_{k=0}^{n+1}a_k + a_{n+1} \sum\limits_{k=0}^{n}a_k=...$  How to go on?


In  ,( page 3),Author solved heat equation using Fourier transformation method ,such that he come up to $u(x,t)=f(x)*g(t)$ with  $$\hat{g}(\omega)=e^{-4 a\pi^2 \omega^2 t}$$ and $f(x)$ is given , He claimed finally that $g$ is given by $$g=\dfrac{1}{4\pi \sqrt{a\pi t}}\exp\Big(\frac{-x^2}{16a\pi^2 t}\Big)$$.I understood all steps given in this paper but I can't show that $g=\dfrac{1}{4\pi \sqrt{a\pi t}}\exp\Big(\frac{-x^2}{16a\pi^2 t}\Big)$ using its Fourier transform which is given by $\hat{g}(\omega)=e^{-4 a\pi^2 \omega^2 t}$ ,I have used the definition of Fourrier transform of $g$ such that $$ \hat{g}(\omega)=\int_{-\infty}^{\infty}g(t)\exp(-2i\pi \omega a x)dx $$ in order to integrate by part but I can't come up to the Author formula in that paper , Any help ?

I need to calculate the Inverse Fourier Transform of this Gaussian function:  $\frac{1}{\sqrt{2\pi}} exp(\frac{-k^2 \sigma^2}{2})$  where $\sigma > 0$, namely I have to calculate the following integral: $\int{\frac{1}{\sqrt{2\pi}} \exp(\frac{-k^2 \sigma^2}{2})} \exp(ikx) dk$.  How can I do that? If I am not wrong (in which case please correct me) the result should be $\frac{1}{\sqrt{2\pi}\sigma}exp(\frac{-x^2}{2\sigma^2})$...but I don't know how to get there!


Writing an Apex class to make REST Callouts to several API endpoints (Jira, , and Zendesk). Methods on the class will be invoked daily by the Apex Job Scheduler. Jira was easy to setup using Named Credentials using my Jira username and a token. Tempo gives me two options:  Using the REST API as an individual user where I create a token that I can use to make requests. Note: I'm not getting a code first and then getting this token. I just get the token. Using the REST API as an application developer (OAuth 2.0) - I'm trying to pull data administratively, not create a web app where users authorize my app to access their data.  This code works using approach 1 (but embedding credentials in code is not good): Http http = new Http(); HttpRequest request = new HttpRequest(); DateTime todaysDate = System.today().addDays(-1); String todaysDateStr = todaysDate.format('yyyy-MM-dd'); request.setEndpoint('https://api.tempo.io/core/3/worklogs?updatedFrom=2020-08-30'); // request.setEndpoint('callout:Tempo/core/3/worklogs?updatedFrom=2020-08-30'); request.setMethod('GET'); request.setHeader('Content-Type', 'application/json'); String TOKEN = 'REPLACE_WITH_ACTUAL_TOKEN'; request.setHeader('Authorization', 'Bearer ' + TOKEN); HttpResponse response = http.send(request);  Wondering what the correct setup would be as a Named Credential in Salesforce (Identity Type, Authentication Protocol, etc.). I wouldn't think I would need to provide a Certificate. Any thoughts?

I want to be able to make callouts to JotForm, but they do not support OAuth and username/password is insufficient for their API. ; for reference, here are the 3 auth options:        Authenticate with Query Parameters   Authenticate with HTTP Headers   Authenticate with Javascript SDK      Basically, they provide an API Key and want me to include an apikey parameter in the header. I don't want to hard code it, I don't want to store it as plain text in custom settings/metadata, and this isn't a managed package. Is there any way to securely store/authenticate from Salesforce, ideally using a Named Credential?  I'd love to be able to just have a Named Credential that is just a securely stored, obscured API Key...


I am not an expert in this field. I have seen documentaries on the Universe and have a basic idea of how black holes come to existence. When black holes form from supernovae they have a initial mass which is a factor of the progenitor's mass. My question is how do they evolve to the million/billion solar mass monsters lurking in galaxies?   In the same vein how do we explain the supermassive black holes in very old galaxies formed immediately after the big bang? Did they form immediately after the big-bang?

Scientists have found very bright source of light which they call  and the are found to be . So these black holes are so massive that they cannot be formed by a supernova. So how are these formed?


I find myself basing my trips on whenever there's a cheap flight, rather than setting a specific date to have a vacation.  However, it makes it hard for me to do this if I can't search for the cheapest flights regardless of date.  Is there a way to do this?    Edit :  I'm from Australia and Australia-specific or international suggestions will both work. However, for the sake of this question as a generic one, I would ask for you to leave any tools you know of regardless of origin, so it might help future viewers.

Several airline and trip planning sites will allow you to check "I am flexible with my dates" or a similar option.  Is there any way to also search more broadly for location?  For example, if you wanted to leave from YYZ or YKF and arrive at any airport in California, can a search for such flights be done somehow?  I ask because when I plan plane trips, I want the lowest price.  I'm OK with leaving a day or two later if I save $200 (same with the return trip).  There are 3 airports within 80 km of me, I'll leave from the one with the cheapest flight. And I'm also OK with changing the trip to spend time exploring San Francisco instead of lying on the beach near San Diego, and that sort of thing.  Normally this would take dozens of searches, but I'd like to see it all at once.


When I try to login in Ubuntu, It login and freeze in desktop screen. When I try to solve this I refer , my problem is solved with small trouble.After this I restart and login into Ubuntu it login and shows same login screen. So I search something about "login loop" I referred . I installed unity desktop and reboot and then restarted my ubuntu still my problem is not solved. I hope lot of you faced this problem if yours is solved. Please share your solutions with me to retrieve my ubuntu OS.  Thanks, Ami

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


I am not sure if this is correct but, if I am not mistaken, a unions is a [StructLayout(LayoutKind.Explicit)] structure where 2 or more elements are on the same field offset.  So if I have this:  typedef union _FILE_SEGMENT_ELEMENT {     PVOID64 Buffer;     ULONGLONG Alignment; }   would this be in C# as:  using System.Runtime.InteropServices;  [StructLayout(LayoutKind.Explicit)] public struct FileSegmentElement {     [FieldOffset(0)]     public IntPtr Buffer;     [FieldOffset(0)]     public ulong Alignment; }   or is this incorrect?

I'm translating a library written in C++ to C#, and the keyword 'union' exists once. In a struct.  What's the correct way of translating it into C#? And what does it do? It looks something like this;  struct Foo {     float bar;      union {         int killroy;         float fubar;     } as; }


I requested Imgur to remove a copyrighted image on the Imgur website which was originally posted on Math Stack Exchange.  This request has been ignored for a long time now. This image has been removed from the Math Stack Exchange question but is still existing in the link ... . Even the Stack Exchange help (contact form) has been unanswered yet. How to have this image removed?

I want to remove some photos from , because they are breaking my privacy (they contain my personal information). How can I do that or who should I ask to do that?


Let $(e_1, ..., e_n)$ be the standard $\Bbb Z$-basis of $\Bbb Z^n$. Let $x_1,..., x_n$ be elements of an abelian group $G$.   I want to prove that there exists a homomorphism $f$ $:$ $\Bbb Z^n$ $\rightarrow$ $G$ such that $f$$(e_i)$ $=$ $x_i$ for all $i$ $\in$ $\Bbb N$.   Please help me..

Let $(e_1, ..., e_n)$ be the standard $\Bbb Z$-basis of $\Bbb Z^n$. Let $x_1,..., x_n$ be elements of an abelian group $G$. Prove that there exists a homomorphism $f$ $:$ $\Bbb Z^n$ $\rightarrow$ $G$ such that $f$$(e_i)$ $=$ $x_i$ for all $i$.   Can anyone please help me out here?


5 random numbers were recorded: 100,32,76,52,17. If we know that these are elements of random sample took from set {1,2, ..., N}, how do we estimate the parameter N?

Suppose that I observe $k=4$ tanks with serial numbers $2,6,7,14$.   What is the best estimate for the total number of tanks $n$?   I assume the observations are drawn from a discrete uniform distribution with the interval $[1,n]$. I know that for a $[0,1]$ interval the expected maximum draw $m$ for $k$ draws is  $1 - (1/(1+k))$. So I estimate $\frac {k}{k+1}$$(n-1)≈$ $m$, rearranged so $n≈$ $\frac {k+1 }{k}$$m+1$.  But the frequentist estimate from  is defined as:  $n ≈ m-1 + $$\frac {m}{k}$  I suspect there is some flaw in the way I have extrapolated from one interval to another, but I would welcome an explanation of why I have gone wrong!


In situations that you want to talk/write about a noun that is the name of a specific instance (like FAQ) of a common noun (like page) which one is correct:   common noun + specific noun like the page FAQ specific noun + common noun like the FAQ page   I have seen both of the above. I know that FAQ page (grammatically called noun adjunct) is more common but I want to know if both are grammatically correct. What is the first one grammatically called? There are a lot of similar cases like:   the site Stackoverflow vs. Stackoverflow site the library Struts vs. Struts library the column Modify Date vs. Modify Date column the button Cancel vs. Cancel button   To clear my gray area, it's worth mentioning that the specific noun is not always a proper noun like the following examples:   the word stack vs. stack word (stack is not a proper noun) the compound noun "chicken soup" vs. "chicken soup" compound noun ("chicken soup" here is not considered the name of a food but just a sample of a compound noun so it is a proper noun)

Is there any rule of where to place the name of a brand/movie/book (before or after the noun)?   I would usually put it before the noun if the name has only one word. Examples:   The "Apple" brand is worth billions of dollars. The "Cambridge" dictionary is very good.   But I am not sure when the name has more than one word. Examples:   The movie "The Untouchables" / "The Untouchables" movie is great! The website "Stack Exchange" / "Stack Exchange" website is popular.


I am very new to c++ so forgive me if I have overlooked something simple. I have a class Circle:  class Circle: public Shape{ protected:      //string name;      Point focus;      float radius; private:  public:     virtual void calculateArea();     virtual void calculatePerimeter();     Circle();     Circle(Point p, float r);   };  I have two constructors, one of which is the default which I have overloaded:  Circle::Circle() {     Point p(1,1);     focus = p;     radius = 10;     name = "Circle";     calculatePerimeter();     calculateArea();     cout<<"default circle"<<endl; } Circle::Circle(Point p, float r) {     focus = p;     radius = r;     name = "Circle";     calculatePerimeter();     calculateArea(); }   In my main I try to create two circles one using the each constructor, however the Circle being created with Circle() never gets created. I cannot for the life of me figure out why? There are no error messages or anything.  int main{     Circle circle(a, 3.3);     Circle c2(); }

Is there any good reason that an empty set of round brackets (parentheses) isn't valid for calling the default constructor in C++?  MyObject  object;  // ok - default ctor MyObject  object(blah); // ok  MyObject  object();  // error   I seem to type "()" automatically everytime. Is there a good reason this isn't allowed?


If I have two Javascript date objects how can I see if my selectedDate is at least one hour into the future? Ex. if its 3PM, the selectedDate needs to be at least 4PM  var selectedDate = //somedatetime object var currentDate = new Date(); // includes current time   if (selectedDate is before currentDateTime + 1 hour) {     // return false }

Can someone suggest a way to compare the values of two dates greater than, less than, and not in the past using JavaScript? The values will be coming from text boxes.


I just finished The Matrix Reloaded. Not for the first time, though this run through of the trilogy is very enlightening. Every piece of it makes sense to me so far except at the end. When The Neb is destroyed by the bomb sent by the machines, the machines attack Morpheous, Trinity and Neo. Neo then destroys them with some kind of EMP like attack. How is this possible? How do his powers exist outside of the Matrix?

In the Matrix, why did Neo have magic powers in the real world? For example,   (1) Those scenes where he blows up those robots purportedly with his mind.  (2) That one where he has no eyes but can see.


I know all of special relativity but I also know it is not enough to study GR. The mathematics is very complex. I have “Spacetime and Geometry” by S. Caroll. He has described it GR well enough but I do not know some of the maths signs and symbols he uses. So what are the prerequisites I need to have in maths. Is there a book that covers those math topics? Or is ther a book on GR that is simple enough for me to understand? Please help.

This question recently appeared :     Slashdot posts a fair number of physics stories. Many of us, myself included, don't have the background to understand them. So I'd like to ask the Slashdot math/physics community to construct a curriculum that gets me, an average college grad with two semesters of chemistry, one of calculus, and maybe 2-3 applied statistics courses, all the way to understanding the mathematics of general relativity. What would I need to learn, in what order, and what texts should I use? Before I get killed here, I know this isn't a weekend project, but it seems like it could be fun to do in my spare time for the next ... decade.   It seems like something that would be a good addition to this site: I think it's specific enough to be answerable but still generally useful. The textbook aspect is covered pretty well by , but beyond that: What college-level subjects in physics and math are prerequisites to studying general relativity in mathematical detail?


It really interest me one thing. Approximately how many people uses Ubuntu and linux in general? Since it has cc 1,50% market share. How much downloads Ubuntu has?

Was just wondering if there is any solid data available as to how many people are using ubuntu. I was also interested in the attrition rate with ubuntu users, etc.


The following question is from a quiz I took a few weeks ago and got incorrect, but the answer wasn't provided:     Consider the following code, which contains no compile errors:  String secret = "Ellie"; Scanner kb = new Scanner(System.in); System.out.println("Guess which name I'm thinking of:"); String guess = kb.next();  if (guess == secret) {     System.out.println("Wow! You're smart!"); } else {     System.out.println("Wrong!");     System.out.println("You guessed: " + guess);     System.out.println("The correct answer was: " + secret); }       Suppose the user enters "Ellie" at the prompt.   What output would result, and why that output and not the other output?   Here was my incorrect answer:     The output would be the else statement "WRONG!" because of the capitalization of the letter 'E'. A solution to this would be   to either change the String secret to "ellie" as well as the user's guess, or one can write in the ignoreCase keyword to   String secret.   The program actually outputs "Wrong", I tested it.  Aside from simply knowing the answer, could someone really explain this to me so I can understand the concept better?

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?