If you manually declare code to be XML, code within CDATA is still highlighted, even though it should be treated as text.  Example:  <element test="test">       <![CDATA[

Lorem ipsum

]]> </element>

I noticed that sometimes my code gets highlighted in different colors when rendered.   What is syntax highlighting? How does it work? Why isn't my code being highlighted correctly? How do I report a bug or request a new language? How do I use syntax highlighting? What languages are currently available on Stack Exchange?


I was a user of ubuntu 8 or whatnot a couple of years ago,nowadays I've been working with Ubuntu 14.04 for some time and I've picked up the habit of putting my thoughts into a simple gedit document. However, as the system tends to crash every once in a while for absolutely no good reason (Toshiba is one, though), I often forget to save the document before I am forced to restart the computer. I can see the back up file right below the original one, yet when I try to open it it will try to find a program to do it, yet quite unsuccessfully. Is there anyone out there who can help me, por favor?

So, I just finished off the first part of an important task for school and today when I was going to continue, the document with my notes were gone. The only fragment I've got left of my file is the back up file, which doesn't show in the folder where I saved the document, but I can search for it.  Is there anyway which allows me to open the back up file, save it as a text file and continue my task? I don't really have the time for running restoring tools, which never has helped me in a satisfactory way anyway.  I wrote the document in gedit and my version of Ubuntu is 12.10.


I have a bash script which must call another bash script which varies per-user in order to get some configuration information, like so:  somescript:  #!/bin/bash ${HOME}/.ssconfig echo "Hello, ${VARIABLE}!"   ~/.ssconfig  #!/bin/bash VARIABLE=world   Which, instead of giving me Hello, world! as expected, gives me Hello, ! How can I pass variables up from a script to the one that called it?

I've written the following script to set some environment variables when needed.  #!/bin/sh export BASE=/home/develop/trees echo $BASE export PATH=$PATH:$BASE echo $PATH   Below the command and the results I can see on my terminal: the script runs, but the variables are not set at the end.  ~$: ./script.sh /home/develop/trees /bin:......:/home/develop/trees ~$: echo $BASE  ~$:    What's wrong? Thanks in advance. Mirko


There is a summation in analysis of an algorithm which is the following:  $$\sum_{h=0}^{\infty}{\dfrac{h}{2^h}} = \dfrac{1/2}{(1-1/2)^2} = 2$$  But I don't can't solve this. I would be appreciated if anyone can solve this.  thanks.

I would like to know: How come that  $$\sum_{n=1}^\infty n x^n=\frac{x}{(x-1)^2}$$  Why isn't it infinity?


I would like to evaluate the following integral $(a>0)$      $$\int_{-\infty}^{\infty}\frac{\exp\left(-a x^2\right)}{x^2+b^2}dx.$$   I've have tried integration by parts, putting $e^{-ax^2}=u$, but I come across with this integral  $$\int_{-\infty}^{\infty}\exp\left(-a x^2\right)\arctan\left(\frac{x}{b}\right),$$  and I don't know how to do it. Could you help me?

I would like to evaluate in a closed form the integral  $$\int_{\mathbb{R}}\frac{\exp(-x^2)}{1+x^2}\,\mathrm{d}x$$  I tried various methods :    integration by parts some changes of variables ($y=x^2$, $x=\tan$) residue calculus (but the factor $\exp(-x^2)$ forbid to send the contour to infinity) developping $\exp(-x^2)$ or $\frac{1}{1+x^2} $ in power series (but in both cases one cannot exchange sum and integral)   Does anyone knows if this integral is known, or how to evaluate it ? At least I would like to find an exact expression.  The reason for me to believe that a closed form exists is that this integral arose in a problem of probability where I expect - if I haven't made any mistake previously - a very simple expression.


In plane pendulum problem, we can calculate its period using elliptic integration.  In SHO problem, we use approximation such that $\theta\ll 1$ and get the period, $2\pi\sqrt{l/g}$.  Is there another way of explaining that the period of pendulum (no approximation) is larger than the period of SHO without considering elliptic integration?

Suppose you have a physical . It is true that as amplitude increases, the period increases. Can we demonstrate this fact without explicitly finding the period (which is pretty involved and pretty messy) in:    an intuitive fashion,  rigorously?


Say I have a function that accepts multiple jQuery objects:  workWithThreeObjs($('.content'),                   $('h1'),                   $('input[type=button]'));   I define my function like this:  function workWithThreeObjs(p, h1, buttons) {     ... }   Inside this function, I want to apply border to all of them like this  $(p, h1, buttons).css(...);   How do I do that? Right now it only applies to p.   My function code does not control what is passed into it, so I cannot change the selectors used to create the arguments. I must operate only on the jQuery objects provided.

How do you combine two jQuery search results? eg:  var $allFoos = $('.foo'),     $allBars = $('.bar')     $allFoosAndBars = $allFoos + $allBars;   Obviously, I just made up that last line, but I hope it makes it sorta clear what I mean. To be clear, the example is greatly simplified, and it could be any arbitrary sets i'm talking about, so $('.foo, .bar') is not what I'm after.


I am using OpenGL to render some cubes and I have managed to get around 10 cubes rendering however I now want to abstract the code out into classes. I have started with the vertex array object.  I have looked through the code and followed it through to the shader making sure vertex data gets where it needs to.  #include "cube_vertex_array.h"  cube_vertex_array::cube_vertex_array(float* vertex_buffer, const std::string& texture_file) {     GLCall(glGenVertexArrays(1, &va_ID));     GLCall(glBindVertexArray(va_ID));  GLCall(glGenBuffers(1, &vb_ID)); GLCall(glBindBuffer(GL_ARRAY_BUFFER, vb_ID)); GLCall(glBufferData(GL_ARRAY_BUFFER, sizeof(vertex_buffer), vertex_buffer, GL_STATIC_DRAW)); GLCall(glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(0 * sizeof(float)))); GLCall(glEnableVertexAttribArray(0)); GLCall(glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)))); GLCall(glEnableVertexAttribArray(1));  GLCall(glGenTextures(1, &texture)); GLCall(glBindTexture(GL_TEXTURE_2D, texture)); GLCall(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT)); GLCall(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT)); GLCall(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)); GLCall(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)); int width, height, nrChanells; stbi_set_flip_vertically_on_load(true); unsigned char* data = stbi_load(texture_file.c_str(), &width, &height, &nrChanells, 0); if (data) {     GLCall(glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data));     GLCall(glGenerateMipmap(GL_TEXTURE_2D)); } else { std::cout << "failed to load texture" << std::endl; } stbi_image_free(data);  GLCall(glBindVertexArray(0)); }  void cube_vertex_array::bind() {     GLCall(glBindVertexArray(va_ID)); }   Also, here is the part of main() that uses this class:  main() { cube_vertex_array cube_1(vertices, "resources/test.png"); cube_1.bind(); while (!glfwWindowShouldClose(window))     {     cube_1.bind();     GLCall(glDrawArrays(GL_TRIANGLES, 0, 36));     }     GLCall(glDeleteVertexArrays(1, &cube_1.va_ID));                                                                              GLCall(glDeleteBuffers(1, &cube_1.vb_ID)); }      I expect to see multiple cubes rendering however this doesn't happen. If I implement the vertex array directly into the main file, the code renders cubes however it does not render anything when abstracted into a class. What could be the problem here?

First off, here is some code:  int main()  {     int days[] = {1,2,3,4,5};     int *ptr = days;     printf("%u\n", sizeof(days));     printf("%u\n", sizeof(ptr));      return 0; }   Is there a way to find out the size of the array that ptr is pointing to (instead of just giving its size, which is four bytes on a 32-bit system)?


I'm sorry for the weird title but i really don't know how to say this. Look: std::array<std::string, 2> names = { "chloe", "tom" };     std::string choice;      std::cout << "Type a name.";     std::getline(std::cin, choice);      std::for_each(choice.begin(), choice.end(), [](char& c) {         c = ::tolower(c);         });      for (int i = 0; i < names.size(); i++) {         if (choice == names[i]) {             std::cout << choice;         }     }  This code lets the user input a name and if the name is inside the names array it gets printed. What i want to do is that as soon as the user types a correct name (chloe for example), even without having to press enter the program recognizes it as correct and proceeds.

I can never remember how I do this because it comes up so infrequently for me. But in C or C++, what is the best way to read a character from standard input without waiting for a newline (press enter).  Also ideally it wouldn't echo the input character to the screen. I just want to capture keystrokes with out effecting the console screen.


I have been taught many things about how to structure code. For instance, nouns translate to classes (Eg, class Dog, class Banana). Something that objects have translate to variables inside the class. (Eg, a dog has a name so name would be a variable inside the Dog class.) I've also been taught that abstract nouns translate to abstract classes, eg, ChessPiece would be an abstract class and king, pawn etc would inherit from it.  How do interfaces work like this? I never find myself using interfaces and I want to because I heard that you should design towards an interface.

This may be a generic OOP question. I wanted to do a generic comparison between an interface and an abstract class on the basis of their usage.   When would one want to use an interface and when would one want to use an abstract class?


I tried all the tutorial on the internet, but no working. I have this simple setup with alpha texture on top of a shader And it became blank after exporting

I used node textures in a mesh I exported to .FBX.  I then imported it into Unreal Engine 4 and it didn't import any textures; I clicked the Upload Textures option in Unreal Engine.  Is there something I'm doing wrong or is it Blender?


In the older versions of blender, you could group objects and they would be treated like one object. In blender 2.8, groups have been replaced with collections. The collections are not treated as one object. How do you select a collection like you would a group?

In the Blender Guru Donut tutorial he made a sprinkle for a donut. He copied that sprinkle and made a smaller version of it. He Shift selected both and made a group with the shortcut Ctrl+G. When I do the same it assigns both sprinkles into a collection. I have read that the layer system is redone completely. So when I make a group out of the two objects, is it the same as a group and where can I see that group?


I used QuarkXpress years ago when freelancing on a temporary basis with a local printer/publisher, when I edited manuscripts for local authors and developed the layouts. The version with which I am familiar is Quark 4.1. (A long time ago!) But I am now considering returning to editing and publishing manuscripts, so which is preferable please: QuarkXpress or InDesign? I have a 64-bit PC running Windows 10. I have little to no experience of Adobe as I have never used PhotoShop, as I used the software provided by marketing departments at the time, such as PaintShop Pro. Thank you

I'm looking for jobs all over the interwebs and I keep seeing postings by companies saying that applicants need to be well versed in most Adobe creative solutions softwares and then QuarkXpress.  But, when I look at actual studio ads (small studios looking for a new designer) they only mention strong Adobe skills.  Is QuarkXpress still relevant? Or is it a legacy software that only gets mentioned because at one time in the past it was one of the best softwares to use?  I know this might be a very subjective question, but I'm looking for those who ave been in the design world a lot longer than I have to give me insight (I've only just begun my design career).


I build many one page websites that dynamically load content through AJAX/jQuery. I keep reading how bad one pagers are for SEO. Regardless, how can you get the most SEO results out of a one page website, without splitting it up into multiple pages?

I'm considering re-designing my personal website to promote my web services in my local area.  My issue is whether to do a one page website with a scroll-to navigation system. What effect does this have on SEO. As i understand it, you set stuff like h1's and meta description on specific page content. How does this work when all of your different content is on one page?


A user wants to , but he can't, because of a delay of 8 minutes. Why must he wait?  See the comment at the bottom of my answer, please.

I hate the new popup "you can accept an answer in 10 minutes". Can you please remove it and let me accept an answer immediately?  I can unaccept it later if a better one appears.


I took a look at the  proposal on Area 51. There was a big link saying "visit the site now!" and out of curiosity I clicked it. To my surprise, I got the regular sign-up screen from Stack Exchange. So, I entered my credentials, expecting to see a warning that only committed users could do this. Instead, I could just join the site, despite never having committed to it, and despite the fact that the site is still in private beta.    I'm guessing this is a bug?

According to Area51,  is still in private beta. But yet I just signed up on it  (already deleted the profile now) despite I didn't commit to the proposal or recieve any mail.  Why did this happen?


I'm not really sure what else to call it, but my goal basically is to create various locations on a map and have them connect with a curved progress bar-like line.  Like this:   I'm familiar with the pen tool and how to make curved lines, but I'm not really sure how to go from a curved line to the picture above.

Here is my MS Paint job on a real bad attempt at what I'm trying to achieve:    I have access to Photoshop and Illustrator CS6, and I want to be able to draw a thick line (that is not straight) and have a pattern within the line show arrowheads within the line to indicate the direction of the line.


I have tried to move windows control buttons using gconf-editor.  It worked partially; Now when windows are not maximied X/Minimize/Maximize buttons are on the right side, but as soon as the windows are maximized it goes back to right. What should I do?  Thanks

I'm fairly excited for Unity, as it looks like a promising new direction for Ubuntu.  However, I do have a concern - will it be possible to use Unity without the global menu?  I have my window manager set to focus-follows-mouse/sloppy focus, and find the productivity gains to be immense. Sloppy focus is incompatible, however, with global menus, as it is possible for the focus to change while you move from window to menu.  Will Unity support an option to use window menus while still using Unity?


I know that if $f:[a,b] \to \mathbb{R}$ is an integrable function such that $f(x) \ge 0,~\forall~x \in [a,b],$ then $$\int\limits_a^b f(x) \mathrm{d}x \ge 0.$$  What happens if we replace the condition $f(x) \ge 0$ by the condition $f(x)>0$? Will the last inequality be also strict?  I tried to use Riemann sums but taking the limit turns $>$ into $\ge$.

In the proof  a strictly positive function in $(0,\pi)$ is integrated over this interval and the integral is claimed as a positive number. It seems intuitively obvious as the area enclosed by a continuous function's graph lying entirely above the x-axis and the x-axis should not be zero. But how can I prove this formally?   If the function is positive over a closed interval apparently  (link goes to page 147 in Theories of Integration by Kurtz and Swarz). This has further confused me. Can someone please clarify my doubt.     Thanks


How can I create this kind of table in html? <th> that has rotated text should automatically set height depended to data in <th>.

Is there a (portable) way to rotate text in a HTML table cell by 90°?  (I have a table with many columns and much text for the headings, so I'd like to write it vertically to save space.)


this is the first question I am posting on stack overflow. So if I have made any mistakes while posting the issue please feel free to tell me. I am developing an application using Mapbox's navigation SDK. I can show the map along with a driving route from source to destination but when I tap on the start navigation button the app is crashing. Logcat showing-> **Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.mapbox.services.android.navigation.ui.v5.NavigationView.onCreate(android.os.Bundle)' on a null object reference at com.mapbox.services.android.navigation.ui.v5.MapboxNavigationActivity.onCreate(MapboxNavigationActivity.java:32) MyCode** @Override public void onMapReady(@NonNull MapboxMap mapboxMap) {     this.mapboxMap = mapboxMap;     mapboxMap.setStyle(getString(R.string.navigation_guidance_day), style -> {          enableMyLocationIfPermitted(style);          button = findViewById(R.id.startButton);         button.setOnClickListener(v -> {                              boolean simulateRoute = true;                 NavigationLauncherOptions options = NavigationLauncherOptions.builder()                         .directionsRoute(currentRoute)                         .shouldSimulateRoute(simulateRoute)                         .build();                  NavigationLauncher.startNavigation(this, options);          });     }); }  MapboxNavigationActivity is a predefined class of Mapbox navigation SDK. By debugging the app, I found that the navigationView object is appearing null and this is the reason for the crash. I don't have an idea why it is null.

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?


Do I need any special license to use Ubuntu in business? I know it's free for home users, but I couldn't find a definitive answer on whether I can use it for business without any special license.

Is  free for business platforms?  Has Ubuntu changed its conditions about using the OS for profit purposes?


It is c# version 8. I have a method Dispatch<T>(T payload) I also have T1:T, T2:T, ... T8:T is it possible to rewrite this: if(data is T1)    Dispatch((T1)data); if(data is T2)    Dispatch((T2)data); ... if(data is T8)    Dispatch((T8)data);  so when someone adds T9:T this part of code do not change at all? I am aware I can use new switch statement, but it is basically the same.

What's the best way to call a generic method when the type parameter isn't known at compile time, but instead is obtained dynamically at runtime?  Consider the following sample code - inside the Example() method, what's the most concise way to invoke GenericMethod<T>() using the Type stored in the myType variable?  public class Sample {     public void Example(string typeName)     {         Type myType = FindType(typeName);          // What goes here to call GenericMethod<T>()?         GenericMethod<myType>(); // This doesn't work          // What changes to call StaticMethod<T>()?         Sample.StaticMethod<myType>(); // This also doesn't work     }      public void GenericMethod<T>()     {         // ...     }      public static void StaticMethod<T>()     {         //...     } }


In my research report, I would like to include both, EPS files to achieve automatic numbering of my compounds in schemes with chemnum and also PNG files to include 3D structures of my molecules. I have tried several approaches, and am able to automatically number my compounds with a latex->dvi->ps->pdf workflow using EPS files for my reactions. However, I am not able to include a PNG file in the same document. What is the right approach for this?  Unfortunately, there is no way to get around the PNG files, as they are made by another programme necessary for visualization.  I have tried this example:      \documentclass[a4paper]{article}     \usepackage[T1]{fontenc} % Modern font encoding     %\usepackage{pstool}     \usepackage{psfrag}     \usepackage[runs=2]{auto-pst-pdf} % Use EPS graphics with pdfLaTeX     \usepackage{booktabs} % Better table layouts     \usepackage[journal=rsc]{chemstyle} % Of course!     \usepackage{geometry} % Easy page layout     \usepackage{lmodern} % Use Latin Modern fonts     \usepackage[version=3]{mhchem} % Formula subscripts using \ce{}     \usepackage{xkeyval}     \usepackage{pst-pdf}     \usepackage{ifplatform}      \begin{document}     Test Test     \begin{figure}     \centering     \psfrag{goldhydrid}{test}     \includegraphics[scale=1.0]{./goldhydrid}     \caption{A Caption}     \label{fig:goldhydrid}     \end{figure}      \end{document}   But I get an error saying:  "Could not create test-pics.pdf. Auxiliary files not deleted."    Ok, after playing around for a while, I could make it work through changing to      \usepackage[crop=off]{auto-pst-pdf}   I also found, that if you're using an EPS file with a text to be substituted by chemnum or psfrag directly, that is very close to the borders of the EPS file, then you might get in trouble with it, because parts of the new text will be cut off. This problem obviously only occurs, if you are using pdflatex but not, if you're using the EPS files directly with a latex->dvi->ps->pdf workflow.  Cheers, Vlad

The following minimal code using the chemnum package was designed to replace TMP1, TMP2 and TMP3 in an eps file made by ChemDraw by numbers:  \documentclass{article} \usepackage{graphicx} \usepackage[runs=2]{auto-pst-pdf} \usepackage{chemnum}  \newenvironment{scheme}{}{}  \begin{document}  \begin{scheme}     \cmpdref{ref:nucleophile1}     \cmpdref{ref:nucleophile2}     \cmpdref{ref:nucleophile3}     \includegraphics[scale=0.6]{aziridineopening} \end{scheme}  \end{document}   A copy of the eps file can be found . Is this problem due to my eps file or my code?


Hello I have a dual boot system with Win10 and Ubuntu 20.04 and I want to open Windows notepad files(text document) in Ubuntu so how to open it?

When I double click on text files, nautilus asks me what I would like to do with them. I find this to be intrusive, as I just want them to open.  How can I fix this?  Note: This question is a "canonical" question on the subject; edit if needed. Note 2: Text files can be HTML, CSS, TXT, and more.


How find this $$\lim_{n\to\infty}\sum_{i=1}^{n}\left(\dfrac{i}{n}\right)^n$$  I think this answer is $\dfrac{e}{e-1}$  and I think this problem have more nice methods,Thank you

I'm asked to find $\displaystyle\lim_{n\to \infty}\sum_{k=1}^n \left(\frac{k}{n}\right)^n$.  It seems that the sum converges.  I managed to prove that $\forall n,1<\sum_{k=1}^n \left(\frac{k}{n}\right)^n<e$  But I don't know how to prove convergence, nor find the value of the limit.


The question asks to find the following limit.  $$\lim_{n\to \infty}\left[\frac{\left((n+1)(n+2)...(n+n)\right)^{1/n}}{n}\right]$$  I tried taking $\log$ but I do not think that we get an L' Hopital form after that.  There is another approach that I tried. I rewrote the expression as $$\lim_{n\to \infty}\left[\left(\frac{n+1}{n}\frac{n+2}{n}...\frac{n+n}{n}\right)^{1/n}\right]$$  If I take $\log$ now, won't the limit be 0? The answer in my book is $4/e$.

I'd like a hint to show that:  $$\lim \frac{1}{n} \sqrt[n]{(n+1)(n+2) \cdots 2n} = \frac{4}{e} .$$  Thanks.


I have a list of all premier league teams:  teamlist = ["arsenal", "aston-villa", "bournemouth", "chelsea", "crystal-palace", "everton","leicester-city", "liverpool", "manchester-city", "manchester-united", "newcastle-united", "norwich-city", "southampton","stoke-city", "swansea-city", "tottenham-hotspur", "watford", "west-bromich-albion","west-ham-united" ]   I need to compute all possible team1-vs-team2 pairings.  At present I have the following code:  oppo = 0  for team in teamlist:         print team + "-vs-" + teamlist[oppo]         oppo+=1         print team + "-vs-" + teamlist[oppo]         oppo+=1   which will output:  arsenal-vs-arsenal arsenal-vs-aston-villa   However I need this to go through each team, display all of their possible home game fixtures, then move onto the next team in teamlist, output all of their possible home games fixtures and repeat until all teams are done.

How do you generate all the permutations of a list in Python, independently of the type of elements in that list?  For example:  permutations([]) []  permutations([1]) [1]  permutations([1, 2]) [1, 2] [2, 1]  permutations([1, 2, 3]) [1, 2, 3] [1, 3, 2] [2, 1, 3] [2, 3, 1] [3, 1, 2] [3, 2, 1]


I am trying to prove the following:   The $m$ vectors $x_i$ are linearly independent if and only if the $m \times m$ matrix $A$ defined below is non-singular   $(i,j) \space element \space of \space A = \langle\ x_i,x_j \rangle\ $  I am confused by what this statement is saying, specifically what matrix A looks like. If we have a matrix where   $\begin{bmatrix}\langle\ x_1,x_1 \rangle\ & \langle\ x_1,x_2 \rangle\\ \langle\ x_2,x_1 \rangle\ & \langle\ x_2,x_2 \rangle\ \end{bmatrix}$   Is such a matrix even possible? I considered the one by one case  $\begin{bmatrix}\langle\ x_1,x_1 \rangle \end{bmatrix}$   This one by one matrix doesn't seem possible since whatever value is put into the first entry has to equal the square of itself.   I must be misunderstanding somehow. I considered the possibility that the question was asking to prove the following statement: the column or row vectors of a matrix are linearly independent if and only if the matrix is non-singular. Is this correct and should I go ahead and prove this statement instead? I suppose the notation throws me off.   Any insight or help would be greatly appreciated!

Given a set of vectors $v_1 \cdots v_n$, the $n\times n$ Gram matrix $G$ is defined as $G_{i,j}=v_i \cdot v_j$  Due to symmetry in the dot product, $G$ is Hermitian.  I'm trying to remember why $|G|=0$ iff the set of vectors are not linearly independent.


My question is simple:      What is the best (and secure) way to check image type?   I need it for my website, where I want to upload photos. (allowed extension jpeg, png, gif? )  Thank you ...

I am looking for a way to take a user uploaded image that is currently put in a temporary location ex: /tmp/jkhjkh78 and create a php image from it, autodetecting the format.  Is there a more clever way to do this than a bunch of try/catching with imagefromjpeg, imagefrompng, etc?


When I attempt to create an edge loop, it stops at the corner of the mouth. I want it to continue into the upper lip.      Does anyone know why this is happening?

Alright so I've seen some postings about loop cuts and done some research. I am very new to blender and modeling overall. I am trying to loop cut this concrete barrier. Now I'm following a tutorial and kind of did my own thing in some areas. I cleaned it up following some instructions in another answer here on stack exchange.  I can't for the life of me figure out why I can loop cut around the whole bottom:   ...but not the whole middle:   I see this marked as answered by another question. That question refers to ngons and inside faces. Now once again I'm totally new to this. I looked on the inside. I don't believe I have inside faces or any ngons by the terms I've read online in my research.  Here is a wireframe picture and the inside view:     Maybe I'm missing something the answers on other posts are saying. If so and you know what it is I'd be very appreciative of what it is.


As the title says really. The Boon of the Night Spirit says:  While completely in an area of dim light or darkness, you can become invisible as an action. You remain invisible until you take an action or a reaction. (DMG, Chapter 7, page 232)  If a character did something that they can do as a bonus action (certain spells, dash or disengage for a rogue, etc.), would the invisibility end?

The Warlock invocation One with Shadows grants invisibility until you "move or take an action or reaction." Does taking a bonus action end this invisibility?


I would like to write a script (.sh or similar) that automatically connects to a wifi network when I know the name and password of the network.  Can anyone give me an example of how to do this?  I am having trouble getting wpa supplicant to work.

So basically, I'd like to use iwconfig to connect to my wifi network when I'm not inside X. But I just don't see a way to do it in the man page. Any idea?


I'm trying to install Visual Studio Code, I downloaded deb file and run it. Ubuntu Software was opened but unfortunately when I tried to click install button nothing happened (this is only happening with third-party software). I didn't even get any error message. What can be the problem?

I just downloaded VSCode-linux-x64 from . It's a 62 MB zip file. How can I install it on my Ubuntu system?


When I ran to Nvidia's website to download their 64bit Linux drivers, it downloaded a file named "NVIDIA-Linux-x86_64-319.49.run".  Since this wasn't a file extension I'd seen before, I assumed double clicking would do nothing (Incorrect; it actually tried opening it in a word processor which hilariously meets with a crashed word processor).  I installed new drivers through a terminal.  For future reference, however, assuming this is an archive, and clearly Nvidia expects everyone to be able to crack it open on command, how would I go about making the .run file actually be useful?  Was there a command to decompress it and install the drivers?  Was it a script and I just have no idea how to execute it?  (Very new to Linux; Ubuntu's my first attempt at running a distro since ...oh, RedHat 6.something.  Anyways, so much for context.)

My PC has both Ubuntu and Windows 7 installed. I have installed all my drivers in Windows like Nvidia graphics, motherboard etc. Shall I install them in Ubuntu too?  I looked on the web for my Nvidia drivers and I have found a .run file. How could I install it on my Ubuntu?


I'm trying to read text from a pdf stored in S3. Is there a way to read text from the stream, rather than creating a PDF locally and then converting it.  import boto3 as boto from boto3.session import Session  session = Session(     aws_access_key_id=AWS_ACCESS_KEY_ID,     aws_secret_access_key=AWS_SECRET_ACCESS_KEY )  s3 = session.resource('s3')  obj = s3.Object('my-bucket', 'file.pdf')  text = obj.get()['Body'].read()  print(text)   I've read that this returns a binary string, <botocore.response.StreamingBody object at 0x10d5a0fd0>. But not sure how to get the text from that.  I'm also new-ish to Python.  How do I read this as text so I can parse that text?

Is there any python module to convert PDF files into text? I tried  found in Activestate which uses pypdf but the text generated had no space between and was of no use.


I have broken the hard drive in my Acer laptop, so need to reinstall. I will get a new one, but how can I install Ubuntu? I have a USB with NetBoot on it, but how can I get it to work in the BIOS settings, and boot from it?

I would like to see a full how-to guide on how to install Ubuntu.


I want to prove the following logic equivalence in Coq.  (p->q)->(~q->~p)  Here is what I attempted. How can I fix this?  Lemma work : (forall p q : Prop, (p->q)->(~q->~p)). Proof. intros p q. intros p_implies_q not_q_implies_not_p. refine (not_q_implies_not_p). refine (p_implies_q). Qed.

I am relatively new to Coq. Can anyone show me how to prove the following in Coq?  (P -> (Q /\ R)) -> (~Q) -> ~P


I always liked to use the word "crackers" to refer to people who overcome computer software or security restrictions, as opposed to "hackers," which (supposedly) originally meant people skilled at computing.  A while ago, I used the word in my conversation with a speaker of AmE, who did not know of that use of the word and thought I was using a racial slur.  This could have been a problem since I am not Caucasian myself.  While I could use other words like "script kiddies" to roughly mean what I meant by "crackers," this left me with the following question: is the use of the word "cracker" as a racial slur so common that it cannot be used to refer to certain hackers without causing misunderstanding?  My assumption is that it may depend on where you are: if you are in the Deep South, probably the word is more commonly used pejoratively than elsewhere.  But I don't know that for sure.

My grandmother from Georgia openly refers to herself and other white southerners as "Crackers", and sometimes adds a state as in "Georgia Cracker" or "Florida Cracker". She says it means simple folks who can only afford to eat crackers. I've also heard it refers to a cattle rancher who likes to crack their whip... but of course it invokes the image of a slave-master.  How broadly is this potentially pejorative expression used? Does anyone know where it really came form, or how disparaging it is?


I have a reference with a capital roman II in the title.  When I run bibtex the capital roman II shows as ii.  How does on fix this.  Thanks, Peaches

Titles of articles I'm about to cite contain upper case letters and when using BibTeX it converts them to lower case ones. This happens only in the title and only the first letter conserves its case. For example, when I cite an article about HF, the reader won't know if it is about Hafnium (Hf) or fluorine acid (HF).  I know that I can fix it manually in the .bbl file but I would like to avoid it, or fix it automatically.


Should a very popular question be closed as a duplicate one that is older but extremely less popular?  I ask because  was closed as a duplicate of the older . While they are certainly duplicates, this seemed very wrong to me:   71 answers, 46 votes, 7 favorites versus 18 answers, 4 votes, 2 favorites   In this case personally I would have closed the older less popular question as a duplicate of the newer one. Is there an official etiquette?  (Note: I flagged it for a mod, so it may be re-opened or merged or something else in the near future)

I have seen this many times, a question is being asked because a previous, duplicate question was asked and answered a few years ago and has no longer relevant answers.  The  is to edit the old question, or add new answers to it, but it is not always happening.  I was wondering, should I still mark it as duplicate and vote to close it? Or just leave it as is?


I am getting a p-value of  < 2.2e-16 for my coefficient in R, but I was wondering if I can say in my write up that it is asymptotically zero? Do these have the same meaning? What would I need to say the later?

For some tests in R, there is a lower limit on the  calculations of $2.22 \cdot 10^{-16}$. I'm not sure why it's this number, if there is a good reason for it or if it's just arbitrary. A lot of other stats packages just go to 0.0001, so this is a much higher level of precision. But I haven't seen too many papers reporting $p < 2.22\cdot 10^{-16}$ or $p = 2.22\cdot 10^{-16}$.   Is it a common/best practice to report this computed value or is it more typical to report something else (like p < 0.000000000000001)?


Olympics is the biggest sporting event on earth, but there are still some spots that are not included in the Olympics like Cricket. It is now a much more popular sport over the world but there are still no sign of it becoming an Olympics sport.

How does a sport transition into the Olympics?  What are the qualifications?  Is there a process?


I just had a quick question about a notation I saw.  I know that a $C^2$  function is a function whose second partial derivative exists. But, what does it mean when one writes $C^2(U)$ where $U$ is a subset of $R^n$? Thanks in advance.

The following is an excerpt from Folland's Introduction to Partial Differential Equations:  Let the open set $\Omega\subset{\mathbb R}^n$, and $k$ be a positive integer. $C^k(\Omega)$ will denote the space of functions possessing continuous derivatives up to order $k$ on $\Omega$, and $C^k(\overline{\Omega})$ will denote the space of all $u\in C^k(\Omega)$ such that $\partial^{\alpha}u$ extends continuously to the closure $\overline{\Omega}$ for $0\leq|\alpha|\leq k$.  As I understand, an extension means that there exists $\widetilde{\partial^{\alpha}u}$ which is defined on $\overline{\Omega}$ and $\widetilde{\partial^{\alpha}u}|_{\Omega}=\partial^{\alpha}u$. And "extends continuously" means $\widetilde{\partial^{\alpha}u}$ is continuous with respect to the relative topology on $\overline{\Omega}$.  Here are my questions:        How do people usually do such extension?   When does such extension exist and when does not?   Let $\Omega$ be an open subset of ${\mathbb R}$. Is there any   non-trivial counterexample such that   this kind of extension does not exist?


I don't remember ever installing an app called 'SIM Toolkit'. Can someone be stalking my phone with a SIM Toolkit?

I've had this app (SIM Toolkit) since forever and can't seem to find a way to remove it.    (Click image to enlarge)


Here my question is straight forward. I registered a domain about 2 months ago and started my brand new blog. Later on, I found that the domain I registered was an expired one which was originally registered in 2015. Now when I submitted my site to google webmaster tools, under crawl errors it shows some links that I haven't submitted or listed in my sitemaps.      My questions ->  1) Will this affect my SEO?   2) How to remove those broken links which do not currently exist. I marked them as fixed but after few days they again appear.  3) Still, my blog doesn't rank within the first 200 results. I'm worried if the first owner has done something stupid(Blach hat SEO) and blacklisted the domain with Google. If so can I clear it as I'm a new owner?  I need help from an expert. I can't find these on my own. Thanks in any help.

Does it make any difference for SEO benefits to buy dropped and already available domains other than backorder domains that are expiring soon?  I heard somewhere that whois gets deleted after being dropped. But I didn't find any confirmation if it's true or not.  Anybody can tell me if there are benefits of one against the other, if yes what?


I was on my smartphone today(win7) browsing SO trying to kill some time. One of the things I noticed was when I posted a reply to a comment, it wouldn't post. I kept trying and trying and couldn't figure out why. Then I remembered the minimal character limit(I don't remember how many off-hand), so I typed in a sentence and it posted.  So to a new user who doesn't know about the character limit(or forgets it for that matter), and doesn't get a visual warning as to why the post wasn't accepted, so right would right off the bat assume SO doesn't work on their mobile device.  Perhaps the powers that be can find a solution to this.   I'm not saying this is a bug or top priority situation, but some point it wouldn't hurt to address it. Maybe just a single sentence line saying minimal # characters just above or below the textarea when posting on mobile.

In the mobile theme on Android 2.3.5, comments that do not meet the minimum length will fail to post but no feedback message is displayed to the user.  The submit button changes to its active state, but nothing else happens.


Does this "as" change the meaning or correctness of this sentence?     This is considered as socially desired.   This is considered socially desired.   Are both of them grammatically correct? Why or why not?


How can I write  in latex? Which command should I use?

I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out?


I am trying to figure out how to use views to list out ALL my taxonomy terms that are grouping node titles. Example:  Taxonomy Term 1 - Node Title 1 - Node Title 2  Taxonomy Term 2 - Node Title 3  Taxonomy Term 3 -Message: There are currently no Node titles at this time, please check back  Taxonomy Term 4 - Node Title 4 - Node Title 5   like :


I am trying to draw up some finite state machines with TikZ. However, when I compile the following code it puts my labels into the regular document rather than in the nodes. Can someone explain what I am doing wrong?   \documentclass[12pt]{article} \usepackage{tikz}  \begin{document}  \begin{center} \begin{tikzpicture}[scale=0.2] \tikzstyle{every node}+=[inner sep=0pt] \draw [black] (15.6,-19.2) circle (3); \draw (15.6,-19.2) node {$q_1$}; \draw [black] (15.6,-19.2) circle (2.4); \draw [black] (33.9,-19.2) circle (3); \draw (33.9,-19.2) node {$q_2$}; \draw [black] (17.49,-16.883) arc (132.7489:47.2511:10.695); \fill [black] (32.01,-16.88) -- (31.76,-15.97) -- (31.08,-16.71); \draw (24.75,-13.54) node [above] {$1$}; \draw [black] (7.9,-19.2) -- (12.6,-19.2); \fill [black] (12.6,-19.2) -- (11.8,-18.7) -- (11.8,-19.7); \draw [black] (14.277,-16.52) arc (234:-54:2.25); \draw (15.6,-11.95) node [above] {$0$}; \fill [black] (16.92,-16.52) -- (17.8,-16.17) -- (16.99,-15.58); \draw [black] (30.9,-19.2) -- (18.6,-19.2); \fill [black] (18.6,-19.2) -- (19.4,-19.7) -- (19.4,-18.7); \draw (24.75,-18.7) node [above] {$0$}; \end{tikzpicture} \end{center}  \end{document}   This is the output that I am getting from the above code.

I have the following Tikz picture:  \begin{tikzpicture}   \node (a) {A};   \node [below=2cm of a] (b) {B}; \end{tikzpicture}   When I compile this code with PDF-LaTeX, I get the expected result: "B" appears 2 cm below "A".  When I compile the exact same code with plain LaTeX, in the DVI file, "A" and "B" are in the same position, mashed together.  In the PS file, after another re-compilation, they appear correctly again.  Is there some way or workaround to work with PGF/Tikz with positioning straight with the DVI preview?


I want to delete all page indexed in google and use url seo to index my page again using url seo and delete old urls. I tried  <meta name="robots" content="noindex">   but does not work.  for example i'm using mybb platform and thread urls is:        after install google seo plugin my thread url is:        I want to update google and replace old url with new url. or delete all google indexed page in bulk.  please help.. thanks in advance

I have used so many things like url removal request and deleted the pages etc., but still the errors are shown in my webmaster tools.  How can I remove the urls completely from Google?


I already see the lodash documentation but I don't know what function do I need to use to solve my problem. I have array  const arr = [   {name: 'john'},   {name: 'jane'},   {name: 'saske'},   {name: 'jake'},   {name: 'baki'}  ]   I want to add {name: 'ace'} before saske. I know about splice in javascript, but I want to know if this is possible in lodash.

I am looking for a JavaScript array insert method, in the style of:  arr.insert(index, item)   Preferably in jQuery, but any JavaScript implementation will do at this point.


Find all nonnegative integer that $2^{2^n}+5 $ is a prime number.  For $n=0$ we have $7$ - correct For $n=1$ we have 9 - false For $n=2$ we have 21 - false For $n=3$ we have 259 ...  Maybe any ideas how to do it in general?

I'm a little lost on how to do this problem. It looks a lot like the definition for the Fermat numbers: $F_n = 2^{2^n} + 1$, however I'm not sure how to use that in order to find all of the primes of the form: $2^{2^n} + 5$.


The following proof is given in my notes: Write the complex integral $\int_a^bf(t)dt = Re^{i\theta}$ where $$ R=\int_a^bf(t)dt. \quad(1) $$ On the other hand, $$ R=\int_a^be^{-i\theta}f(t)dt.\quad(2) $$ Write $e^{-i\theta}f(t)=U(t)+iV(t)$ where $U(t)$ and $V(t) $ are real-valued functions. Then because R is real,  $$ R=\int_z^bU(t)dt\quad(3) $$  But now, $$ U(t)= Re\ e^{-i\theta}f(t) \le e^{-i\theta}f(t)=\vert f(t)\vert\quad(4) $$ Therefore, from the properties of real integrals, $$ \int_a^bU(t)dt\le\int\vert f(t)\vert dt $$ which proves the desired result.  I have trouble figuring out how each of the numbered equations actually hold. After writing the integral as $\int_a^bf(t)dt = Re^{i\theta}$ How can we say that (1) and (2) hold. (3) sort of makes sense as R has to be real.

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


I am currently benchmarking my 3.0 USB Flash drive both fragmented and defragmented.  My initial setup consisted of Crystal Disk Mark and a flash drive with no files on it.  I recorded the output several times and took an average.  Then, I fragmented the drive using PassMark Fragger and checked the defragmentation level with Defraggler.  For a test with around 80% fragmentation, the write speeds actually got FASTER  how could this be?

"Fragmentation happens to a hard disk over time as you save, change, or delete files."    I understand with harddisks there is a moving disc that has to spin and seek for files. When the files are fragmented it has to look at several different locations on the disk thus taking much more time compared to if all the files were in one similar location on the disk.   Flash disks don't having moving parts, so the gains from defragmenting should be minimul correct?  So we can agree USB drives can become fragmented... But is there ANY* / realworld performance benefits from defragmenting them?


The About Me field in the user profile doesn't have Markdown enabled, so for instance, if you leave empty lines, they don't count, and instead you have to use <br>.  At least make it so that newlines are not ignored, it's really annoying, having to put with html tags, in a simple "about me" field.  Related question:

If you have such a good way to do formatting in questions/answers why isn't it used for the "about me" section on the profile page?  It looks easy to make and adds just a little bit more consistency.


I can't think of great examples on the net (comparisons to draw, that is). You've seen the feature before though. You are making an edit to something--say, a setting. And when you make the change, there is a quick transparent modal with the 'loading' circle animation (or a flashing disk or something), and the word 'Saving', or something similar. This appears on screen for maybe half a second, one second? Then it goes away, and there is a fade-out box near the saved feature that says 'Saved', or 'Successful', and it fades out over 5 seconds or something...  So, despite sounding like a teenage girl in the explanation (like, totally), have I explained it well enough?   My question here is, what are implementation ideas/examples for this? I'm looking both at user experience patterns/thoughts, and also implementation thoughts.   We're on DOJO framework, so really we can do anything from an animated GIF and CSS transitioned box to something fancy and javascript-y (as long as it's doable within DOJO--I don't want to use jQuery, for example).   Thanks for your contributions!

I'm currently in the process of developing a Windows Application which produces Word Documents. In the program there is the ability to save your progress (different to the "Save as a Word Document" option). This option "Save Current Progress" saves your progress, there is no user input, except the action of clicking the button (i.e. they don't have to specify a file location). When designing the functionality for this button I researched other instances of "Save" buttons in programs. Most of them resemble floppy disks, and on clicking them there is no feedback (except the subtle visual cue of mouseover and click on the button itself). i.e. there is no alert window saying "you have saved" nor does the button change to signify a saved state. The problem is that in my application this could be confusing. In Microsoft Word (for instance) it is the most natural thing to click the save icon and know it has saved, without any positive feedback. However in my application it confuses users and they say that they "don't know" that what they've done has actually saved anything. The icon is different to the Word one. It resembles a hard drive with an arrow pointing down onto it.  However, surely the thought process should be the same. I'm going to change the functionality so that the icon changes to that of a tick momentarily to give positive reinforcement that the status has saved, but I'm interested as to why the two scenarios differ so much. Update As per some of the suggestions here I have created this graphic to switch states when the user saves.


Out of all of the nucleoside triphosphates what makes ATP the most used? Is it its structure? The amount of energy it contains? Why is GTP not used as much? What is the deal with the other nucleoside triphosphates (dATP, dGTP, dTTP, dCTP, UTP, CTP)? Are there any artificial NTPs that can substitute for ATP? (like something that could cure Cyanide poisoning or a disease/illness that somehow de-functionalizes the Electron Transport Chain)

Why is ATP the most prevalent form of chemical energy storage and utilization in most cells?


have a project in java(a pacman game) which uses some external files, for example a .txt for the level design and some images for the pacman and ghosts. Right now i have them all under the  and access them as follows:  Scanner s = new Scanner(new File("level1.txt"));  image = ImageIO.read(new File("PM0.gif"));   The project works fine if i run it through eclipse, however when i export it to a .jar executable it wont load any file properly. What is the simplest way to have these resources properly packaged and loaded? I am new to java programming(this is my first project) and i got very confused from some previous answers to this question(and none of them worked).

I know the file needs to be where the getClass().getResource(filename) can find it, but I don't know where that is.  I'm interested both in where to put the files on the filesystem itself, and how to go about using Eclipse's functionality to set up the resources.


I am not a pro at Mac / OS X. But I know my way around.  I just installed OS X El Capitan. However when I first started up, my harddisk used 30GB with 'other'. With time the capacity just keeps shrinking. If I just stare at the screen, I just see the available space drop and drop. Until it hits Zero Bytes at capacity.   Does anyone know what I can do about this? I cannot seem to find anything on this on Google.   The only thing it returns on my keywords are things like how to remove temporary files, re-index size with Spotlight, Startup in safe mode. None of these things seem to work.    @Edit 22:02 06-04-2016  I have checked Activity Monitor and got the following results:   I have sorted on Bytes Written, that does not seem very strange.  However if I check the Graph Data Written below it gives:   As you can see the data Written is around 8.33 GB and a few minutes later already 10 GB,.. I checked; 'sudo fs_usage -f filesys' this keeps trying to get some attribute lists from mdworker? Don't know if that is normal?    @Edit 20:30 07-04-2016 With 'sudo fs_usage -f filesys' I see that the following processes write;   nsurlsession nsurlstorage IMRemoteUrlC cfprefsd   With using Daisy Disk App I see the following:   So the private and library grows a bit, however the Core grows massively. I see that it produces a 'core dump' of around 528 mb every now and then. This tells cores is a folder for a core dump;    What/why is this happening? (Like the post I have set the core dump limit to 0 and it seems to have stopped generating.)    PS: This is not a duplicate of , I do not have time machine / Backups turned on.

Here's my problem: over the past couple days I did a really good clean out of my computer and managed to free up several gigabytes of data and was hovering around 233+ gb of free space.   Then in the last couple of days I noticed my trash file was taking a really long time to empty (I don't know if this is part of the problem but wanted to mention it just in case).  Last night I noticed I was missing quite a lot of space on my drive, it was around 205 gigs now. I discovered I had accidentally set some large torrent files to be on my main drive instead of an external. No matter, I figured! I would just delete them and start them over on the external. But my disk space didn't seem to change. So I rebooted - after all I had recently used Photoshop and that tends to hog a bunch of space and I don't get it back until I reboot.  I rebooted and there was still the same ~205 gb of free space. I was very confused. I was even more confused when I checked "About My Mac" and saw that it was telling me that in actual fact I only had around 90gbs of free space. THE HECK!?  I did notice that my "backups" were surprisingly high - 119gb in fact. This was especially curious since I have a time machine drive (time capsule) thats supposed to be backing up hourly. I did get a message this morning telling me it was full, but isn't it supposed to clear itself out?  Running WhatSize (it's still running by the way) I see that my .MobileBackups folder is a gargantuan 134gb! I thought these were temporary! For when I'm not connected to Time Machine (WHICH I AM!)  What in the hell is going on? How did I magically lose close to 25 gigs? And how the hell do I get it back?


When I switch my Nikon D750 from sRGB to the Adobe RGB color space in the Photo Shooting menu, how does it affect the content of my NEF files? I understand what would happen to JPEGs, but the camera manual is not clear whether this setting affects raw files or not.  Also, I am interested in how this or a similar setting affects raw files in other recent Nikon and Canon cameras.

I shoot RAW essentially 100% of the time, and have the in-camera color space setting at AdobeRGB (sRGB is also offered). The raw converter in turn is set to produce sRGB output files. As I understand the process, the general flow is for raw shooting: raw sensor data readout (including A/D conversion), compression, write to a raw file, then in post-processing rather than in-camera apply color space/color temperature/etc; for JPEG shooting: raw sensor data readout, apply color space/color temperature/etc, JPEG compression, write to memory card (in camera).  Hence, when a colleague said that I should leave the camera set to sRGB for best/consistent results despite using the camera's raw format, it didn't really make much sense to me. I have mulled it over for a while now and it still doesn't really make any sense.   seems to support my view of the differences in the data recorded in RAW and JPEG modes, respectively.  I did find , but the answers there seem to focus more on the difference between AdobeRGB and sRGB. My question is, when shooting RAW, does it ever matter (except for the image preview) whether the camera is set to sRGB or AdobeRGB? If it does, then why, and in what situations? Is my understanding of the "raw" format processing chain flawed?  In case it matters, I have a Canon EOS 50D.


Update 1: this question is not a duplicate - the Python question happened to be locked, but my question is about closing in general and not historical locks. Here is another example that was closed:   Update 2: I see that the Ruby question has been deleted because I mentioned it. Deleting the evidence does not make this question a duplicate. Here's another example:   I'm genuinely curious. I want to know which Python IDEs are popular and come highly recommended. I understand that there is not a single correct answer to this question, but it's still a valid (and very popular) question.     Closing the question prevents anyone else from answering, but it still appears in search results and does not prevent additional comments. So to state this another way, how does preventing people from answering a question, while still keeping it visible, improve Stack Overflow?

Historical locks are sometimes applied to questions.   What is a historical lock? What is the purpose of a historical lock? How are questions affected by historical locking? When is it appropriate to lock a question for historical reasons?  When is it not appropriate? How do I request a historical lock for a question? What should I do if I notice a serious problem with a historically-locked question or one of its answers?


I have $$P(x | \lambda_1, \lambda_2) = \mathcal{N}(\mu + L_1 \lambda_1 + L_2 \lambda_2, \Sigma)$$  and a Gaussian prior for $$P(\lambda_1) = P(\lambda_2) = \mathcal{N}(0, I)$$.  My task is to compute $$p(x | \lambda_1)$$ and I know the answer should be $$p(x | \lambda_1) = \mathcal{N}(\mu + L_1 \lambda_1, L_2 \Sigma L_2^T)$$.  I present below the steps I took and where I got stuck:  $\begin{align*} p(x | \lambda_1) &= \int p(x | \lambda_1, \lambda_2) p(\lambda_2) d\lambda_2 \\ &= \int const \cdot exp\big[(\hat{x} - L_2 \lambda_2)^T \Sigma^{-1} (\hat{x} - L_2 \lambda_2) + \lambda_2^T \lambda_2\big] d\lambda_2 \end{align*}$  Where $\hat{x} = x - \mu - L_1 \lambda_1$. I process the exponent and get the following: $\begin{align*} & (\hat{x} - L_2 \lambda_2)^T \Sigma^{-1} (\hat{x} - L_2 \lambda_2) + \lambda_2^T \lambda_2 \\ =& \hat{x}^T \Sigma^{-1} \hat{x} - 2 \hat{x}^T \Sigma^{-1} L_2 \lambda_2 + \lambda_2^T (L_2^T \Sigma^{-1} L_2 + I) \lambda_2 \end{align*}$  but I do not know how to proceed further. I have the notes for the solution for the exercise, but I do not understand it.  Below they also have $\lambda_1^T \lambda_1$ because the wrote $p(x | \lambda_1) = p(x | \lambda_1, \lambda_2) p(\lambda_1) p(\lambda_2)$ and then integrated $\lambda_2$ out, but I thought that's not necessary.    Help would be greatly appreciated.  Thank you!

I am trying to understand how 'completing the square' method is used to determine mean and co-variance of multivariate Gaussian distribution but I am not able to make much sense of the following step $$−((x−μ)^TΣ^-(x − μ))/2 = −(x^TΣ^−x + x^TΣ^-μ + const)/2$$ where x and μ are vectors and Σ is co-variance matrix.  What does this step indicate and how is it derived?   P.S. I am not well versed with linear algebra which might be a reason for not being able to comprehend this fully, if you can point me to certain properties from linear algebra that are being used here, that will be very helpful


The number of elements in $\mathbb{Z}_{11}$ satisfies $x^{12}-x^{10}=2$.     I don't know how to start it.

How many elements $x$ in the field $\mathbb{ Z}_{11}$ satisfy the equation $x^{12} - x^{10} = 2$?


P.S: You are going to see a lot of code cause I think they all should be shown. Please, don't get angry with me. Hello, the task is to output vectors and maps in a specific style to improve readability. I am using VS studio and I have the following 3 files in one project: main.cpp with the content: #include "Output.h"  int main() {     std::vector<int> vector1 = { 1, 34, 5, 1, 487 };     std::vector<double> vector2 = { 1.34, 5.1, 4.87 };     std::cout << "vector1: " << vector1 << std::endl;     std::cout << "vector2: " << vector2 << std::endl;      std::map<int, int> map1 = { {1, 1}, {2, 4}, {3, 9}, {4, 16} };     std::map<int, double> map2 = { {1, 1.1}, {2, 2.2}, {3, 3.3} };     std::cout << "map1: " << map1 << std::endl;     std::cout << "map2: " << map2 << std::endl;     return 0; }  Output.h with function names: #ifndef OUTPUT_ #define OUTPUT_  #include <iostream> #include <vector> #include <map> #include <utility> #include <string> #include <sstream>  template<typename First, typename Second> //pair output std::ostream& operator<< (std::ostream&, const std::pair<First, Second>&);  template<typename vector_type> //vector output std::ostream& operator<< (std::ostream&, const std::vector<vector_type>);  template<typename First, typename Second> //map outtput std::ostream& operator<< (std::ostream&, const std::map<First, Second>);  template<typename Container> //output map and vector in the specific format std::string Output(const Container&, const char&);  #endif  Output.cpp with the function bodies: #include "Output.h"  template<typename First, typename Second> std::ostream& operator<< (std::ostream& out, const std::pair<First, Second>& pair1) {     return out << "{" << pair1.first << ", " << pair1.second << "}"; }  template<typename vector_type> std::ostream& operator<< (std::ostream& out, const std::vector<vector_type> vector1) {     return out << "{ " << Output(vector1, ',') << " }"; }  template<typename First, typename Second> std::ostream& operator<< (std::ostream& out, const std::map<First, Second> map1) {     return out << "{ " << Output(map1, ',') << " }"; }  template<typename Container> std::string Output(const Container& c1, const char& Sign) {     std::stringstream output;     bool First_element = true;     for (const auto& c : c1) {         if (!First_element) {             output << Sign << " ";         }         First_element = false;         output << c;     }     return output.str(); }  Everything looks pretty good, but I can't compile main.cpp this way (I don't know why, maybe something's wrong with the IDE or I did not link the files properly). Specifically, it gives: 8 lines of 1>main.obj : error LNK2019: unresolved external symbol "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<<int>(class std::basic_ostream<char,struct std::char_traits<char> > &,class std::vector<int,class std::allocator<int> >)" and similar errors, fatal error LNK1120: 8 unresolved externals. Now, if I #include Output.cpp instead of Output.h, it works perfectly fine: no problems with the compilation and it outputs the expected result. I know it is not a good idea to include .cpp files, but why the first version of main.cpp doesn't work, and what could be the reason it did not compile? Actually, in the beginning, it all was in one main.cpp file and it worked properly, so no problem with the code itself. I just decided to divide it into separate files. Thank you!

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.)


He lives in Utrecht, Netherlands and the Netherlands would be my port of entry and exit, as well as the country I spend the most time in. My friend would have to go through so much hassle for giving the sponsorship letter and previous salary slips.  Besides, he just had an accident a few weeks ago and hasn't been working and I don't want to trouble him by making him do all these formalities. Is it okay if I just book the hotels for the sake of applying for the tourist visa and then cancel the bookings? Do they follow up on such things? I need advice quickly.

My route trip is Prague-->Berlin-->Vienna. I want to change the route to be Prague-->Berlin-->Paris.  Additionally, I already got my Schengen Visa, but after that I found a good deal in another hotel.    Can I change the first hotel I will visit before I travel?  If yes, is that going to cancel my visa or anything like that? Also I planned to go to Vienna and go back to my home from there. Can I change it and go to Paris instead?


So i read about the Zener diode voltage regulator circuit in the The Art of Electronics book, it made no sense to me, then I read about it in this  which was helpful but I still don't get it:         – Schematic created using   How is it reglating the voltage exactly?! and why is the diode "reverse biased" (I guess it means connected in reverse) which doesn't conduct current unless a very high reverse voltage is applied?  If for example the input voltage is 12V, what would be the output voltage and current? and what would be the voltage and current values through the diode?

I'm having trouble understanding the simple voltage regulator that can be built using a zener diode (from section 2.04 in the Art of Electronics).  I know that it would be better to use amplifiers, et cetera, but I'm just trying to understand how this circuit works.      I don't really understand how the circuit works, but I am guessing that when a load is applied to the output, it drains current from the source (Vin) and thus causes the voltage to drop?  How does the zener diode help to maintain the voltage and thus make this circuit act as a regulator?


Let $G$ be a group and let $a, b$ be elements of $G$ such that: i) $\langle a\rangle\cap\langle b\rangle={\{1}\}$ ii) $ab=ba$ II) $|a|=m, |b|=n$ Show that $|ab|=l.c.m (|a|,|b|)$ Idea: Note that $a^m=1,\; b^n=1,$ let's do $k=l.c.m (|a|,|b|)$ (least common multiple), $|ab|=w,$ hence $(ab)^k=a^kb^k=1,$ then $k$ divides $w$, How can I prove that $ w $ divides $ k $? Thanks so much for reading.

If $a, b \in G$ commute   , show that  $o(ab) \mid\operatorname{lcm}(o(a), o(b))  $.  (Hint: Let $L=\operatorname{lcm}(o(a), o(b))$ and prove that $(ab)^L =e$.    ??  So I know that  *Suppose a has order n ,and b has order m ; that is, a^n=e and b^m=e   Then, since G is abelian, we have $(ab)nm=^{nm}=(a^nma^{nm})(b^nmb^{nm})=((a^n)^m))(^m\cdot (b^m)^n))=e^n=e$.  Now, the order of ab may be smaller, but it must divide $     nm=\operatorname{ord}(a)\cdot\operatorname{ord}(b)$.*  how iHow I can answer this question?


I am trying to log transform time series data of Inflation. However, there is one negative value. I have added the constant 1 to all my values and the log transformed.  loginfl <- log(infl_ts + 1)   Will this affect my analysis?  I am planning to tun predictions on this data.

I have analysed my data as they are. Now I want to look at my analyses after taking the log of all variables. Many variables contain many zeros. Therefore I add a small quantity to avoid taking the log of zero.   So far I've added 10^-10, without any rationale really, just because I felt like adding a very small quantity would be advisable to minimize the effect of my arbitrarily chosen quantity. But some variables contain mostly zeros, and therefore when logged mostly -23.02. The range of the ranges of my variables is 1.33-8819.21, and the frequency of zeroes also varies dramatically. Therefore my personal choice of "small quantity" affects the variables very differently. It is clear now that 10^-10 is a completely unacceptable choice, as most of the variance in all the variables then comes from this arbitrary "small quantity".  I wonder what would be a more correct way of doing this.  Maybe it's better to derive the quantity from each variables individual distribution? Are there any guidelines about how big this "small quantity" should be?  My analyses are mostly simple cox models with each variable and age/sex as IVs. The variables are the concentrations of various blood lipids, with often considerable coefficients of variation.  Edit: Adding the smallest non-zero value of the variable seems practical for my data. But maybe there is a general solution?  Edit 2: As the zeros merely indicate concentrations below the detection limit, maybe setting them to (detection limit)/2 would be appropriate?


I spend most of my time on the culture and religion Stack Exchange sites.  I'd like to think I've done my fair share of reviewing.  Here on M.SO, I keep seeing questions about 'failing audits.'  I can't for the life of me remember actually even seeing if I've been audited!  So, three questions:   Is automated Review Auditing part of all graduated sites, or just SO? How do I know if I had one? How do I know if I passed?

I completed recently a few review audits, some of them I passed, some I failed.  Is there a place I could (easily) find these results?


I am new to this. Just got this message below and I cant figure out how to fix it  Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt --fix-broken install' to correct these. The following packages have unmet dependencies:  libasound2 : Depends: libasound2-data (>= 1.1.8-1) but 1.1.3-5 is to be installed E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).   Thanks a lot

After upgrading from 10.04 to 12.04 I am trying to install different packages.  For instance ia32-libs and skype (4.0).  When trying to install these, I am getting the 'Unable to correct problems, you have held broken packages' error message.   Output of commands:  sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   After running this:  sudo dpkg --configure -a foo@foo:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.


I was convicted on a marijuana possession charge in 2010. I received nine months in county jail and three years probation sentence. I completed without incident. I have never been in any other trouble. My conviction was reduced to a misdemeanor and dismissed.    Do I need to apply for a visa?   What are the chances of being denied?   I am planning on attending a wedding in 2019 in Wales.

I have a friend with a criminal record who wants to go to London with me and I'm trying to determine if that is actually a possibility.  This friend was convicted of a class A misdemeanor on Dec 14, 2011 for theft. The court disposition was deferred so they weren't sentenced to any jail time (although they were in jail shortly following their initial arrest and prior to their being bonded out). They were, however, placed on probation for two years.  Since they were never actually sentenced to jail time it seems like, per , that their visiting the UK shouldn't be a problem.


How do I find out how many people use a particular PPA.  I see on a particular PPA ;  Package build summary A total of 108 builds have been dispatched for this PPA. Completed builds 108 successful 0 failed  Does that mean only 108 people have added this PPA to their sources list and installed the package?

I'd like to know how many downloads of a given package in a PPA there have been since it was first published.  I remember there was  about it about getting these metrics on the web UI, but as far as I know, it never got implemented.  But I think the number of downloads can nevertheless be obtained via the  if I'm the owner of that PPA. Any pointers?


looking for a sci-fi book I read most likely in the 90’s.  Probably not published before the 70’s, certainly not newer than 2000. Set in the future. Main character was some sort of private investigator, or law.  Possibly looking for a missing woman or importance? Was physically biomechanically modified/enhanced. Bio metallic muscle fibers, futuristic Kevlar (cut and bullet/projectile resistant skin, but not resistant to lasers), eyes were “shined” (something like the Riddick character from Pitch Black movie/Riddick series). Eyes sensitive to UV/IR light, protectors mounted under skin in cheek bones. Retractable silver biomechanic sharp long teeth, claws (both hands and feet). Length of teeth when enhanced hinders his talking. When his “enhanced” mode is triggered, Adrenalin and chemicals flood his body and metabolism races. Massive energy/calorie demands. One part of the story I remember is he escapes from some sort of captivity (possibly on a space ship) using his abilities (strength claws, etc.). Uses lots of energy, nothing to eat, passes out due to low calories, has some sort of alien artifact ring on his finger at the time. Unknown to him it “heals” him of his injuries and helps him not starve by drawing in the energy from the grass in the clearing in the woods where he passes out in. Wakes up to large brown dead grass circle around him. I think this is all near the beginning of the novel. Wish I had more, thx for the help!

I have very vague impressions of a book I must have read as a child/teenager in the 1980s (so probably published in the UK in the 1970s or early 1980s).  It featured a man who had been technologically enhanced with special powers that he could activate only for short periods (probably because they took a lot of energy), possibly by tonguing one of his teeth.  They gave him:   Much faster reactions; everything around him slowed down. Greater strength/speed. Metal fingernails/claws. Possibly some sort of enhanced vision, too.   I think it described him engaging these powers as: He activated. or similar.  He may have been a mercenary type, who had paid a lot for them; they were rare or unique.  I don't recall any plot or other characters; it was probably a techno-action story.  (No magic, armies, warrior races, telepathy, vampires, or mutants, and I don't recall aliens or space travel.)  It may have been part of a short series of 2 or 3 books.  I'm afraid this isn't much to go on!  I'd completely forgotten about this book until recently, and my impressions are very hazy, so any of the above could be wrong.  (I remember enjoying it, though.)  I've not found anything I recognise on this site, or others; nor in lists of adult and young-person's SF for that period (so it probably wasn't a big-name author).  Does it ring any bells for anyone?


I accidentally put 2 cups of water in one box of strawberry cake mix, and i was only supposed to put 1 cup. I dont have any extra boxes to start over with, and the consistency of it is too thin! How can i fix it?

I added too much water in my box cake mix and I already mixed the 2 together. What can I do to save the cake? Could I add another box of cake mix to the batter?


I am trying to install Ubuntu 16.04 LTS on an external Toshiba 3.0 2TB hard drive, but after the install my computer will not boot to the hard drive. The computer doesn't even recognize the hard drive at all.  I have reformatted the drive using Windows and Ubuntu. I have reinstalled Ubuntu several times using the the automatic partitioning and by manually setting up the partitions myself. Nothing seems to work.   I also have changed my boot order to boot from USB before HDD in the UEFI options.  Does anyone have any ideas as to why my computer is not recognising the drive?   Thanks for your  time!

OS: Windows 7. I want install Linux Ubuntu on portable external Hard Drive USB 2.0. I read a variety of methods, but I'm confused by contradictory advices and methods. Actually, installing Ubuntu on anything other than clean PC looks much more complicated than installing Windows. I need to have Ubuntu package + Python 2.7 + C compiler installed. My external hard drive is partially filled, I need to keep all files.   Will Ubuntu run entirely on external hardrive, without writing anythinhg to Windows system folders and to registry?  Can anyone post detailed guide how install Ubuntu on external hard drive?


Can anyone please tell me the difference where to use union and where to use uinon all in mysql

What is the difference between UNION and UNION ALL?


Sauron, Morgoth's first and foremost lieutenant, had a fair form which was lost only when Illuvatar pulled Numenor down into the sea with Sauron's fair form was trapped within it, such that Sauron's spirit was forced to abandon it. It seems to be suggested that all Ainur possess one.  Being somewhat evil since the beginning, does Morgoth possess a fair form at all? Does he still possess it?

Is Morgoth, the original enemy in J. R. R. Tolkien's Middle-earth ever visually described? I envisage him as a bigger, meaner version of the physical Sauron, but I cannot find any reference in The Simarillion.


Ubuntu boot takes to long to boot, about 1.5 min!! Dell LATITUDE E7440 , intel core-i5 , 8GB RAM output of systemd analyze blame : 26.917s plymouth-quit-wait.service                                                                16.000s NetworkManager-wait-online.service                                                        14.935s dev-sda1.device                                                                           11.647s snapd.service                                                                              9.628s udisks2.service                                                                            9.148s networkd-dispatcher.service                                                                8.924s dev-loop10.device                                                                          8.598s dev-loop16.device                                                                          8.595s dev-loop11.device                                                                          8.517s dev-loop3.device                                                                           8.469s dev-loop1.device                                                                           8.426s dev-loop8.device                                                                           8.062s dev-loop12.device                                                                          7.863s dev-loop0.device                                                                           7.611s dev-loop14.device                                                                          7.248s accounts-daemon.service

I have seen many videos that make Ubuntu faster, but these methods only make desktop performance faster.  I am looking to make my computer boot faster. Is their anything I can do to make Ubuntu boot significantly faster?


Suppose that $Y\subset X$ are connected spaces and suppose that $A$ and $B$ are separation of $X-Y$. Prove that the union $Y\cup A$ is connected.  I want to prove by contradiction.Firstly I assume there exists a separation of $Y\cup A$,say $C\cup D$ .Then since $Y$ is connected,then $Y$ must belong to $C$ or $D$. Whithout loss of generality,we can suppose $Y\subset C$.I guess $C\cup B$ and $D\cup A$　should be the separation of $X$.But I don't know how to prove it in formal mathematics.

If $(X,\mathcal{T})$ is a connected space, and $Y$ a connected subset, and $X\setminus Y=A\cup B$ for separated sets $A$ and $B$, then why is $A\cup Y$ connected as well?  Thank you kindly.


I know how to show $a_n$ diverges, or $b_n$. I know the sum of two convergent limits is the sum of the limits. But how do we show that two divergent limits are divergent?

if $A_n \longrightarrow \infty $ and $B_n \longrightarrow \infty $  then $(A_n+B_n) \longrightarrow  \infty$.  How do you prove it?


I live in the Netherlands as a student and have a valid resident permit. I intend to travel to the US and I have an Indian passport. Is it possible to apply for a visa here through the Indian Embassy?

I'm currently residing in a country other than my own, and am planning a business trip to the USA for a week. Being a Bulgarian citizen, I do not qualify for the ESTA visa waiver program, unlike other EU countries.  The US embassy in Sofia lists a  which they inexplicably describe as "really quite easy". Unfortunately, some of the steps involved would be a major inconvenience for me, as I'm not residing in the country currently, particularly the interview and the visa/passport delivery.  I was hoping it could be possible to apply for a visa from the country of current residence rather than my own, but I wasn't able to find any information on the US embassy's webpages concerning this.


I'm working with Spring to manage the life cycle of my beans. I'm trying to use @Autowired or @Resource annotations to make successful ioc but i'm always getting the famous NullPointerException.  My interface.      /**      * @author Soufiane NAJAH      *      *       */     public interface ITokenService {          public String obtainToken();     }   The implementation.      @Service     public class ITokenServiceImpl implements ITokenService {          // TODO NAJ : Déplacer l'url vers le fichier properties         private static String tokenRequestParameters = "http://localhost:8080/****/****/*****?grant_type=******&client_id=*****&"                 + "client_secret=*****&username=******&password=*******";          private static String access_token = "";          public String obtainToken() {              try {                 URL url = new URL(tokenRequestParameters);                 HttpURLConnection conn = (HttpURLConnection) url.openConnection();                 if (conn.getResponseCode() != 200) {                     throw new RuntimeException("Failed: HTTP error code: "                             + conn.getResponseCode());                 }                 BufferedReader br = new BufferedReader(new InputStreamReader(                         (conn.getInputStream())));                 // System.out.println("OutPut from the server ......");                 JSONObject myObject = new JSONObject(br.readLine());                 // System.out.println("access_token " + myObject.get("value"));                 access_token = (String) myObject.get("value");             } catch (MalformedURLException e) {                 e.printStackTrace();             } catch (IOException e) {                 e.printStackTrace();             }             // System.out.println(access_token);             return access_token;         }   The call to my object      public abstract class GenericWebServiceClientImpl implements             GenericWebServiceClientInterface {          private static final long serialVersionUID = 1L;          protected Client client;         protected WebTarget baseTarget;         private boolean initialized = false;          @Autowired         private ITokenService tokenService;          public GenericWebServiceClientImpl() {             init();         }   My web.xml              <listener>             <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>            </listener>        <context-param>         <param-name>javax.faces.DATETIMECONVERTER_DEFAULT_TIMEZONE_IS_SYSTEM_TIMEZONE</param-name>         <param-value>true</param-value>     </context-param>     <context-param>       <param-name>javax.faces.STATE_SAVING_METHOD</param-name>       <!-- valeur initiale "server" changee en "client" car server provoque erreur ViewExpiredException -->       <param-value>client</param-value>      </context-param>         <context-param>             <param-name>contextConfigLocation</param-name>             <param-value>                 WEB-INF/web-context.xml             </param-value>         </context-param>   My webContext.xml      <?xml version="1.0" encoding="UTF-8"?>     <beans xmlns="http://www.springframework.org/schema/beans"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"         xsi:schemaLocation="http://www.springframework.org/schema/beans              http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">          <import resource="classpath:spring/applicationContext-security.xml"/>      </beans>   My applicationContext-security.xml      <context:annotation-config></context:annotation-config>     <context:component-scan base-package="ma.net.s2m.service.rs.client.token"></context:component-scan>   I have no idea where the problem is.

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?


Let $N$ be a $2\times2$ complex matrix such that $N^2=0$. Prove that either $N=0$ or $N$ is similar over $\mathbb{C}$ to  $$\begin{pmatrix}0&0\\1&0\end{pmatrix}$$

Let $A$ be a $2\times 2$ complex matrix such that $A^2=0$. Prove that either $A=0$ or $A$ is similar over $\mathbb{C}$ to $$\left(\begin{array}{cc} 0 & 0 \\1 & 0 \end{array}\right) $$


I hold a short stay visa issued by Switzerland. In my itinerary, I mentioned Zurich as the first port of entry. But, I would like to change my travel plan with Paris as the first port of entry and then to Switzerland (Zurich) where I stay for longer duration. Shall I be permitted?

In case, if I get a multiple-entry Schengen visa in one of the embassies in Ukraine, Kyiv - should my first trip be to the country which issued the visa?  Any there any requirements of this sort? Does this condition vary depending on embassy which issued the visa?  What are the possible consequences on not visiting that country first? Does it somehow depend on country where the embassy is (i.e. non-Schengen and not EU members)?


We define a Projective space of a vector space as follow :   Given a vector space $V$ over a field $\mathbb{K}$,   its associated projective space $\mathbb{P}(V)$ is by definition :  $\mathbb{P}(V) = V - \{0\}/\sim$ where $\sim$ is the equivalence relation    $u \sim v$ iff $u = \lambda v$ for $u, v\in V - \{0\}$ and $\lambda \in \mathbb{K}$.  In particular,  The real projective space  $\mathbb{R} P^n$  is   the quotient space of $\mathbb{R}^{n+1}-\{0\}$ by the equivalence relation defined  on $\mathbb{R}^{n+1}-\{0\}$ by  $$x\sim y \iff y=tx$$  for some nonzero real number $t$, where $x,y\in\mathbb{R}^{n+1}-\{0\}$. Geometrically, two nonzero points in $\mathbb{R}^{n+1}$ are equivalent if and only if they lie on the same line through the origin, so $\mathbb{R} P^n$ can be interpreted as the set of all lines through the origin in $\mathbb{R}^{n+1}$.  In other hand,  For two  real vector spaces $V$ and $W$, the  Tensor-Product $V \otimes W$ is the  Quotient space $K^{V\times W} / R(V,W)$, where $R(V,W)$ is generated by the vectors  \begin{align*}  (v,\lambda w) - \lambda (v,w) & \\ (v,w+w')-(v,w)-(v,w') & \\ (\lambda v,w) - \lambda(v,w) & \\ (v+v',w)-(v,w)-(v',w) & \\ \text{and} \quad K^{V\times W} := \{f: V\times W \rightarrow\ K\}. &  \end{align*}  for any basis $(v_i)_{i\in I}$ of V and $(w_j)_{j\in J}$ of W, $(v_i\otimes w_j)_{i\in I,j\in J}$ is a basis of $V\otimes W$, so any $a\in V\otimes W$ is a linear combination of some vectors $v_i\otimes w_j$. And a tensor of type $(n, m)$ is an element of $V^{\ast \otimes m} \otimes V^{\otimes n}$. For example,  - A tensor of type $(0, 0)$ is a scalar. - A tensor of type $(1, 0)$ is a vector.  How can Intemperate geometrically the tensor product of two projectifs space ? What is interpretation of the tensor product of  two Grassmannians ?  Thanks in advance.

First of all, I am very comfortable with the tensor product of vector spaces. I am also very familiar with the well-known generalizations, in particular the theory of monoidal categories. I have gained quite some intuition for tensor products and can work with them. Therefore, my question is not about the definition of tensor products, nor is it about its properties. It is rather about the mental images. My intuition for tensor products was never really geometric. Well, except for the tensor product of commutative algebras, which corresponds to the fiber product of the corresponding affine schemes. But let's just stick to real vector spaces here, for which I have some geometric intuition, for example from classical analytic geometry.   The direct product of two (or more) vector spaces is quite easy to imagine: There are two (or more) "directions" or "dimensions" in which we "insert" the vectors of the individual vector spaces. For example, the direct product of a line with a plane is a three-dimensional space.  The exterior algebra of a vector space consists of "blades", as is nicely explained in the .  Now what about the tensor product of two finite-dimensional real vector spaces $V,W$? Of course $V \otimes W$ is a direct product of $\dim(V)$ copies of $W$, but this description is not intrinsic, and also it doesn't really incorporate the symmetry $V \otimes W \cong W \otimes V$. How can we describe $V \otimes W$ geometrically in terms of $V$ and $W$? This description should be intrinsic and symmetric.  Note that  basically asked the same, but received no actual answer. The answer given at  discusses where tensor products are used in differential geometry for more abstract notions such as tensor fields and tensor bundles, but this doesn't answer the question either. (Even if my question gets closed as a duplicate, then I hope that the other questions receive more attention and answers.)  More generally, I would like to ask for a geometric picture of the tensor product of two vector bundles on nice topological spaces. For example, tensoring with a line bundle is some kind of twisting. But this is still some kind of vague. For example, consider the Möbius strip on the circle $S^1$, and pull it back to the torus $S^1 \times S^1$ along the first projection. Do the same with the second projection, and then tensor both. We get a line bundle on the torus, okay, but how does it look like geometrically?  Perhaps the following related question is easier to answer: Assume we have a geometric understanding of two linear maps $f : \mathbb{R}^n \to \mathbb{R}^m$, $g : \mathbb{R}^{n'} \to \mathbb{R}^{m'}$. Then, how can we imagine their tensor product $f \otimes g : \mathbb{R}^n \otimes \mathbb{R}^{n'} \to \mathbb{R}^m \otimes \mathbb{R}^{m'}$ or the corresponding linear map $\mathbb{R}^{n n'} \to \mathbb{R}^{m m'}$ geometrically? This is connected to the question about vector bundles via their cocycle description.


The objective of clustering analysis is to group data with similar characteristics in clusters, but in this case, I want to find the most unrelated data to group into clusters.  In my particular case I have 100 weather stations during one year with a 1hr interval, and I want to group the most similar weather stations(I performed this step with K-means using the correlation distance via Matlab, but I can use R or python). But now, I want to perform the inverse, i.e., group in the same cluster unrelated (with no correlation) weather stations .  This is possible? If yes, how? Or, should I use others techniques to execute my idea?   Thanks in advance!

The objective of clustering analysis is to group data with similar characteristics in clusters, but in this case, I want to find the most unrelated data to group into clusters. In my particular case, I have 100 weather stations during one year with a 1hr interval, and I want to group the most similar weather stations(I performed this step with K-means using the correlation distance via MATLAB, but I can use R or Python). But now, I want to perform the inverse, i.e., group in the same cluster unrelated (with no correlation) weather stations .  Is this possible? If yes, how? Or, should I use others techniques to execute my idea?  The main idea is to use the groups to prove a concept often used in wind power designated as statistical power smoothing effect (). Basically, there is a statistical power smoothing effect in the wind power data, if you considered data with different features (e.g., different weather conditions). I want to use this grouping to show if I carefully grouping my weather stations (that will be transformed in wind power), then I can minimize the fluctuations. So far I applied k-means algorithm to select the weather stations with the same behavior, and now I want to explore the opposite. Probably, the technique that I need is not clustering, but so far I search and nothing came up.  @Pere: Yes, I also expected what you mentioned. Can you provide some reference to understand how I can compute the correlation inverse distance?  @Dougal: I want diverse groups, as in the normal cluster.  To be honest the goal was to split the data in the same number of the "normal" clustering, in my case 9.  @ Pere: Thank you for the example. But I didn't achieve the expected results since, in my case, some clusters are very close to the ones obtained with the "normal" cluster. Probably it is better to try a trial and error test (adding/removing weather stations) to understand the weather stations that I should combine to smooth my signal.


Proof by induction: $n! > n^2$ for $n\ge 4$  Basis step: if $n=4$  $4\cdot3\cdot2\cdot1 > 4^2$  $24 > 16$  I don't know how to do the inductive step.

How can I show that $n^2<n!$ for all $n\geq 4$ Step 1 For $n=1$, the LHS=$4^2=16$ and RHS=$4!=24$. So LHS$<$ RHS. Step 2 Suppose the result be true for $n=k$  i.e., $k^2<k!$ Step 3 For $n=k+1$ $(k+1)^2=k^2+2k+1$ What will be the next step?


How do I delete all these menus? I can't see my model.

I would like to close some view windows that I opened accidentally.  See the image below:    Edit: another note: I tried searching for the solution, but only found things like "Join Area", which don't seem to work in this situation.


In a remote shell, how can I find the domain name of the computer from which I logged into the remote machine? Example: My local machine is mi.pona.com. On this machine I run ssh toki@sina.pona.com  to login into the remote machine sina.pona.com. In the shell  which opens (running on the remote machine) I want to find out from which computer I logged in, so I want to get the result "mi.pona.com". Is there a command for this?

I often work on one of available to me Linux/HP-UX servers (let's say it is server1) and then do  ssh server2 ((let's say it is server2)) and start working on another Linux/HP-UX server. Then I can connect another server ((let's say it is server3) and start working on it. While working on server3 how to get in command line information from what server I came from?   So on server3 I want to get information that I came from server2 and on server2 I want to get information that I came from server1? What is a command or utility for it?


I've given a dataset of N samples like: (x,y) (-100,1), (-90, 30), (-50,60), (-10,90), (0,100), (10, 90), (30, 20),(100,4)  Now I would like to determine how well the data fits a perfect gaussian (normal) distribution. For that reason, I want to fit a gaussian curve to the data and in an additional step compare the estimated gaussian with the "perfect" gaussian. Any ideas how to achieve this in C++, Boost or Eigen functions?   I'm quite stuck here. Is this even a good approach? What I actually want is a measure of how well the data follows a gaussian distribution shape.

I have read somewhere in the literature that the Shapiro–Wilk test is considered to be the best normality test because for a given significance level, $\alpha$, the probability of rejecting the null hypothesis if it's false is higher than in the case of the other normality tests.  Could you please explain to me, using mathematical arguments if possible, how exactly it works compared to some of the other normality tests (say the Anderson–Darling test)?


Stackoverflow seems to have roughly 30 new questions per 5 minues. But when I pick one of these questions to answer it, it takes some time to write a good answer, sometimes 10 or 20 minutes, and when I submit, it often happens that there is already an answer, maybe not as extensive as mine but with the same satement.  I don't want to write faster answers with less quality, but once I want to be the first answering to a question :-)  Do other people also have this 'problem' and how do you deal with that?

I feel like there's a problem with Stack Overflow, as the number of people prowling it increases.  Each question's answers are sorted by descending score and then by descending time of posting. This means that if a person sits down and answers a question in a long, thorough way, going through every nook and cranny, once they post their answer, it will already be one of about seven different ones, some of which have already been upvoted. This wouldn't be a problem if those answers were as thorough as the one this guy's posting, but they usually aren't. Some of them are downright wrong, some aren't even answers to the question asked because their poster didn't bother to read the question all the way through.  This causes a problem I like to call Stack Overflow's Fastest Gun in the West Problem. I've come to a point where I'd rather just send a short, simple, correct explanation, than to go and do some proper research, write a whole blog post about it or even make sure the code I post even compiles, just so it will be noticed, as opposed to the incorrect ones.  I'm sure I'm not the only one doing this and that it despairs many people from even trying to answer questions.  I've long ago learned to try to always raise a problem with a solution in hand, rather than just say "This is a problem, handle it," so my question, after this long tirade, is:     How do you think this can be changed? What would you change in Stack Overflow to make this problem go away without hurting the site?   I promise to vote on answers I like, even if it takes you a long while to post them. :)


How to handle the 'underscore' and the special character in latex listing. I am working on a simple prolog style code   \begin{lstlisting}[label=LE, name=R_E]     $\alpha_{1}$ = *M1*  °h1°(^A^, ^B^) :- °b1,1°(^B^, ^A^), °b1,2°(X).     $\alpha_{2}$ = *M2*  °h2°(^A^, ^B^) :- °b2,1°(^B^, ^A^), °b2,2°(X). \end{lstlisting}   This produces an output as shown below:     Below is my latex listing command:  \lstset{language=Prolog, numbers=left, numberstyle=\scriptsize, numbersep=3pt, basicstyle=\scriptsize \ttfamily, tabsize=3, captionpos=t, stepnumber=1, frame=lines, breaklines=true, showspaces=false, commentstyle=\scriptsize\ttfamily \color{mygreen}, moredelim=**[is][\color{vc}]{°}{°}, % To use text color inside a listing, we use a dilimiter moredelim=**[is][\color{kw}]{*}{*}, moredelim=**[is][\color{darkgreen}]{^}{^}, %moredelim=**[is][\color{cyan}]{<?}{?>}, keywordstyle=\color{cyan}, morekeywords={type,value,href,xmlns,owl,/owl,rdf,/rdf,date,source,start,id,name,language,as, refersTo}, morecomment=[s]{<!--}{-->}, morecomment=[s][\color{grey}]{<<}{>>} escapeinside={}  }   But its not printing the character 'α' nor the underscore next to it. Similaryl, also next to 'h' and further 'b'

I want to use math mode in lstlisting. How do I do that? How to put tab in this mode?  \begin{document}  \begin{lstlisting}[frame=single]                % Start your code-block module main() enumerated States {$S_0$,$S_1$,$S_2$,$S_3$} integer c; initial : c = 0 and States = $S_0$; endmodule \end{lstlisting}  \end{document}