I know that the implementation of C++ polymorphism is based on the vtable and vptr. But now I don't understand how the pointer of the base class get the vptr of the derived class. For example:  class Base {     int b; public:     virtual void f() {}     virtual void g() {} };  class Derived: public Base {     int d; public:     virtual void g() {} }; int main() {     Base *b = new Derived();     b->g(); }    In this case, why b can access the vtable of the derived class? If the derived class inherits more than one base class and the derived class overrides the virtual functions of these base classes, then there will be multiple vptr in the derived class.  Derived *d = new Derived(); Base1 *b1 = d; Base2 *b2 = d; Base3 *b3 = d;   So how do these base class pointers get vptr and offset in the vtable?

We all know what virtual functions are in C++, but how are they implemented at a deep level?  Can the vtable be modified or even directly accessed at runtime?  Does the vtable exist for all classes, or only those that have at least one virtual function?   Do abstract classes simply have a NULL for the function pointer of at least one entry?  Does having a single virtual function slow down the whole class? Or only the call to the function that is virtual?  And does the speed get affected if the virtual function is actually overwritten or not, or does this have no effect so long as it is virtual.


Trivial question. What is the most elegant function myfunction that allows to produce the following output?  # myfunction "a b c d" a%0Db%0Dc%0Dd%0D

I have to take a list (loads) of IP addresses in this format:   134.27.128.0  111.245.48.0  109.21.244.0   and turn them into this format with a pipe in-between (IPs made up)  134.27.128.0 | 111.245.48.0 | 109.21.244.0 | 103.22.200.0/22   I think it is a find and replace command like sed but I can't get it to work.


I'm looking for a solution to flatten a variable multi-dimensionaled array to flatten all the values in the last available array to a single Array[] (containing the dataset of each last array in the multidimensional array).  Any help is appreciated!  It differs from other questions   Because the ending result should be a collection of all Arrays containing :  array(     'title' => xx,     'id' => xx )   listed in the different multidimensional arrays. The different items all have fixed keys: title and id.  Sample Base array  $data = array(     array(         'title' => xx,         'id' => xx     ),     array(         array(             array(                 'title' => xx,                 'id' => xx             ),             array(                 'title' => xx                 'id' => xx             )         )     ),     array(         array(             array(                 array(                     'title' => xx,                     'id' => xx                 ),                 array(                     'title' => xx,                     'id' => xx                 ),                 array(                     'title' => xx,                     'id' => xx                 )             )         ),         array(             'title' => xx,             'id' => xx         ),         array(             array(                 array(                     array(                         'title' => xx,                         'id' => xx                     )                 )             )         )     ) );   Should be flattend to   $data = array(     array(         'title' => xx,         'id' => xx     ),     array(         'title' => xx,         'id' => xx     ),     array(         'title' => xx,         'id' => xx     ),     array(         'title' => xx,         'id' => xx     ),     array(         'title' => xx,         'id' => xx     ),     array(         'title' => xx,         'id' => xx     ),     array(         'title' => xx,         'id' => xx     ),     array(         'title' => xx,         'id' => xx     ) );

It's probably beginner question but I'm going through documentation for longer time already and I can't find any solution. I thought I could use implode for each dimension and then put those strings back together with str_split to make new simple array. However I never know if the join pattern isn't also in values and so after doing str_split my original values could break.  Is there something like combine($array1, $array2) for arrays inside of multi-dimensional array?


When I try to print out the method it gives me the wrong value even though when I run it in debug mode in the 2nd last step over it says that array = {1, 2, 6, 24,120} which is the correct output but when I just run the program I get the following output [I@4dd8dc3 I don't understand why the output doesnt work when it says the correct value that I want it to print the step before sout int[] array = {1,2,3,4,5}; System.out.println(productOfPrevious(array));  static int[] productOfPrevious(int[] array){          int[] ar = array;         if (array.length == 1)             return array;          for (int i = 1; i <= array.length - 1; i++){             ar[0] = array[0];             ar[i] = array[i] * ar[i-1];          }          return ar;     }

In Java, arrays don't override toString(), so if you try to print one directly, you get the className + '@' + the hex of the  of the array, as defined by Object.toString():  int[] intArray = new int[] {1, 2, 3, 4, 5}; System.out.println(intArray);     // prints something like '[I@3343c8b3'   But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs:  // Array of primitives: int[] intArray = new int[] {1, 2, 3, 4, 5}; //output: [1, 2, 3, 4, 5]  // Array of object references: String[] strArray = new String[] {"John", "Mary", "Bob"}; //output: [John, Mary, Bob]


I have a runtime error. got this error message:     java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.LayoutInflater.inflate(int, android.view.ViewGroup, boolean)' on a null object reference   studio is pointing at this row:  View view= lI.inflate(R.layout.fragment_frag3,container,false);  public class Frag3 extends Fragment {      ViewPager viewPager;     CardAdapter2 adapter2;     List<String> cardWords;     LayoutInflater lI;      @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container,                              Bundle savedInstanceState) {          View view= lI.inflate(R.layout.fragment_frag3,container,false);         viewPager= (ViewPager)view.findViewById(R.id.vp);         viewPager.setAdapter(adapter2);         viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {             @Override             public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {              }              @Override             public void onPageSelected(int position) {              }              @Override             public void onPageScrollStateChanged(int state) {              }         });         cardWords= new ArrayList<>();         cardWords.add("x");         cardWords.add("y");         cardWords.add("z");          adapter2= new CardAdapter2(getActivity(),cardWords);          // Inflate the layout for this fragment         return view;     }   }    Adapter:  public class CardAdapter2 extends PagerAdapter {     private Context mContext;     private List<String> cardWords;     private LayoutInflater layoutInflater;      public CardAdapter2(Context mContext, List<String> cardWords) {         this.mContext = mContext;         this.cardWords = cardWords;     }      @Override     public int getCount() {         return cardWords.size();     }      @NonNull     @Override     public Object instantiateItem(@NonNull ViewGroup container, int position) {         layoutInflater= LayoutInflater.from(mContext);         View view= layoutInflater.inflate(R.layout.card_design2,container,false);          TextView title= view.findViewById(R.id.textView2);         title.setText(cardWords.get(position));         container.addView(view,0);          return super.instantiateItem(container, position);     }      @Override     public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {         container.removeView((View)object);     }      @Override     public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {         return view.equals(object);     }   }

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


I want to create a file like this : sshTOhost :  #!bin/bash ssh -D 1500 user@host #enter password (I don't know how)

I need to login to a user that I've created on a remote host running Ubuntu. I can't use an ssh key because the ssh login will happen from a bash script ran within a server that I won't have access to (think continuous integration server like Bamboo).   I understand this isn't an ideal practice, but I want to either set the remote host to not ask for the password or be able to login with something like ssh --passsword foobar user@host, kind of like MySQL allows you to do for logins.   I'm not finding this in man ssh and  I'm open to any alternatives to getting around this issue.


I have a lot of directories that contain some text files and I would copy all files (of all directories) in a new directory. I'm looking for a bash command that do this. How can I do it?

I would like to copy all files with a certain extension that are in sub directories to a different folder. I don't want to maintain the directory structure, I just want to copy all files found to a different folder.  I used this command to do it:  cp `find . -name "*.aac"` /media/moasad/New\ Volume/Media\ files/Avengers/Aud/aac/   However, I noticed that If it runs into folders or files with spaces in them the cp function doesn't know what to do and I get an error something like this:  cp: cannot stat ‘./Temporary_Items/martin/Problem’: No such file or directory cp: cannot stat ‘Files/nav-YCA136843.aac’: No such file or directory   Notice that its one file: ./Temporary_Items/martin/Problem Files/nav-YCA136843.aac  But because of the space in "Problem Files", it's confused.


I have a problem with installing apps from a debian. I open a .deb file in Ubuntu Software and click the "Install" button. for a few seconds it seems to work, with the meter on the install button appearing and rising normally for a split second. then the meter suddenly disappears and the Install button becomes live again and nothing seems to have happened. I click it in rapid sucession, and this app called "waiting to install" appears and it does absolutely nothing after that. So, how do I install a Debian properly!? error: Detailed errors from the package manager follow:  do not know how to install app in state unknown

How do I install a .deb file via the command line?


I am very new to the python and playing around the print statement and found something unexpected. print(0.3 + 0.1==0.4)  ANS : True  but when I tried print(0.2 + 0.1==0.3)  ANS : False   Could Any one explain why is this so? Thanks

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


First of all, my profile picture on  has changed by itself. If I recall correctly, the moment I clicked on the edit link, or when I made a change in one of the fields (not sure), the picture just changed by itself to what appeared to be Identicon.  On other sites, if I try to change my profile picture, I have Gravatar and Identicon options. As far as I can tell, only on Programmers SE, I don't have a Gravatar option, only Identicon. I'd like to use Gravatar on this site just like the others. This was working fine until a few days ago when I made a completely unrelated change to my profile.

Do not know whether someone else observe it or not but today I found my profile Gravatar changed. It is now different than earlier I have. Is it because today I have updated my profile information?        My previous gravatar looks like:


I want to show that $\sin(\frac{x}{2})(\sin(x)+\sin(2x)+...+\sin(nx))=\sin(\frac{nx}{2})\sin(\frac{n+1}{2}x)$  But I'm not quite sure how to start my proof. I tried to expand the left half of the equation but that didn't seem to be the right idea. Help appreciated!

Prove by induction    $$ \sin x + \sin 2x + ... + \sin nx = \frac {\sin (\frac {n + 1} {2} x)} {\sin \frac{x}{2}} \sin \frac{nx}{2} $$   What I have for now: $$  \frac {\sin (\frac {n + 1} {2} x)} {\sin \frac{x}{2}} \sin \frac{nx}{2} + \sin(n + 1)x =  \frac {\sin (\frac {n + 2} {2} x)} {\sin \frac{x}{2}} \sin \frac{(n + 1)x}{2}$$ Letting $y = \frac {(n + 1)x} {2} $   $$\frac {\sin y} {\sin \frac{x}{2}} \sin (y - \frac{x}{2}) + \sin2y =  \frac {\sin (y + \frac {x} {2} )} {\sin \frac{x}{2}} \sin y $$  Then I used $\sin (\alpha + \beta)$ and $\sin (\alpha - \beta)$ formulas, bit they didn't help.


I am searching on the web how to fix the problem with phpmailer going to the spam-box inside outlook(Hotmail).  I tried a lot of things but none of them worked.  $result = $statement->fetchAll();     if(isset($result))     {         $base_url = "http://www.gester.nl/loginsystem2/";  //change this baseurl value as per your file path         $mail_body = "
Hi ".$_POST['user_name'].",

Thanks for Registration. Your password is ".$user_password.", This password will work only after your email verification.

Please Open this link to verified your email address - ".$base_url."email_verification.php?activation_code=".$user_activation_code."
Best Regards,
Gester
         ";         require 'class/class.phpmailer.php';         $mail = new PHPMailer;         $mail->IsSMTP();                                //Sets Mailer to send message using SMTP         $mail->Host = 'xxxx';       //Sets the SMTP hosts of your Email hosting, this for Godaddy         $mail->Port = '587';                                //Sets the default SMTP server port         $mail->SMTPAuth = true;                         //Sets SMTP authentication. Utilizes the Username and Password variables         $mail->Username = 'xxxx';                   //Sets SMTP username         $mail->Password = 'xxxx';                   //Sets SMTP password         $mail->SMTPSecure = 'tls';                          //Sets connection prefix. Options are "", "ssl" or "tls"         $mail->From = 'xxxx@mail.com';          //Sets the From email address for the message         $mail->FromName = 'Gester';                 //Sets the From name of the message         $mail->Sender = $_POST['user_email'];         $mail->AddAddress($_POST['user_email'], $_POST['user_name']);       //Adds a "To" address         $mail->WordWrap = 50;                           //Sets word wrapping on the body of the message to a given number of characters         $mail->IsHTML(true);                            //Sets message type to HTML         $mail->Subject = 'Email Verification';          //Sets the Subject of the message         $mail->Body = $mail_body;                           //An HTML or plain text message body         if($mail->Send())                               //Send an Email. Return true on success or false on error         {             $message = 'Register Done, Please check your mail.';         }         else {             $message = 'Mail could not be send.';         }     }   I hope someone could give me a good explanation on how to fix this exactly. Because there are many answers online but they are not accurate.

This is a tricky one and I've always relied on techniques, such as permission-based emails (i.e. only sending to people you have permission to send to) and not using blatantly spamish terminology.  Of late, some of the emails I send out programmatically have started being shuffled into people's spam folder automatically and I'm wondering what I can do about it.  This is despite the fact that these particular emails are not ones that humans would mark as spam, specifically, they are emails that contain license keys that people have paid good money for, so I don't think they're going to consider them spam  I figure this is a big topic in which I am essentially an ignorant simpleton.


I was building this pretty large build on Minecraft Pocket Edition (iPhone), and now that I started playing Minecraft on my Macbook Pro, It's getting hard for me to build on MCPE. I have tried multiple methods to convert MCPE worlds to MC Java, but all have failed (MCToolChest doesn't work for me since I am running on a Mac, which doesn't support Windows). I really don't want to start over, but I could borrow someone else's Windows laptop to perform MCToolChest, though I'll save that as a last resort. Any ideas?

Can I get my Minecraft Bedrock Edition worlds onto my PC to play in regular Minecraft? If so how? I have used iExplorer to transfer files from my iPad but that was no help. Any suggestions?


Can anybody tell me how to fix it?    I'm using Chrome 32.

I have this new problem since 2014 begin. I cant remotely login to this enterprise network for giving them support. Its keep showing this new error.  How to fix it please?    EDIT:


We have that, $x^{n}=0$ for some $n$ $\in$ $\mathbb{Z}_{+}^{*}$.  I want to find some $y$ $\in$ $A$, such that, $(x+u)y=1$,  so that $(x+u)$ is unity of $A$.  Could you help me determine $y$ or show a better demonstration?

If $ua = au$, where $u$ is a unit and $a$ is a nilpotent, show that $u+a$ is a unit.   I've been working on this problem for an hour that I tried to construct an element $x \in R$ such that $x(u+a) = 1 = (u+a)x$. After tried several elements and manipulated $ua = au$, I still couldn't find any clue. Can anybody give me a hint?


Take the list variable num1 = [] and say i also take num1_child = randint(0,100) how do I go about making num1 progressively become a longer list by adding num1_child to the list, as opposed to simply changing it's value every eteration? (I looked at:  but did not fully understand how to implement that in my code)

What's the difference between the list methods append() and extend()?


WebElement myElement = driver.findElement(By.cssSelector(usernameSelectorPath));   usernameSelectorPath is a String variable which I have created in the fields, and I am having the user of the program enter the selector of the username box and store that as usernameSelectorPath. However, when I take that usernameSelectorPath to convert it to a WebElement, I get a java.lang.NullPointerException and I am unable to do it. I think it is because the variable type is a string, and it is a reference variable.   How can I fix this problem and convert String to a WebElement?

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?


when objec is null:  if(object != null && object.string.equals("")) {     System.out.println("no error"); }   it will result in NullPointerException, and why if it checks the first result is false, it still check the second instead of stop check and print "no error"?  sorry for my bad english -_-#


For instance, what would have happened to Harry if the Dursleys never told him anything, if he never received a letter from Hogwarts, or if no one ever told him he was a wizard? Would he just live his live wondering why he sometimes does something strange?

In the Harry Potter universe, young wizards and witches are sometimes born to Muggle parents. In this case, someone from the wizarding world visits them to offer the child their place at Hogwarts.   Anyway, attendance at Hogwarts isn't mandatory because parents can home school their children, but is this true for all children, or only those whose parents can teach them magic?  Would a Muggle-born wizard or witch be left to their own devices, not taught magic or integrated in the wizarding community, basically be left to live as a Muggle?   The only example I know of is Harry (the Dursleys didn't want him to go, but they were intimidated into letting him) but then again he is Harry Potter and there is no other way (even for Dumbledore in-universe) than to make an exception for him.   Do we know what the general rule would be for muggle born wizards and witches, or do we have any clues?


Question:  Is there an equivalent of Nested -ANOVA for data which fails ANOVA requirement?  Is it possible to perform in R?    I am doing an analysis of large data set.   I have three groups (Genotypes: Wild type, Heterozygous , Homozygous mutant). Each group has data from >10 animals. For each animal, I have 500+ independent observations (example: Volume of 500 different retinal cells).   Based on Levene's test between the three groups, I see I cannot do ANOVA. I have decided to do a Welch ANOVA and I do see significant difference. (I used the oneway.test() function.)  As my 500+ observations are nested inside individual animals, I think I should perform nested Welch ANOVA for my data set.  How can I do nested Welch ANOVA in R?  Could you please show me an example with a similar data?  mydata <- read.table(header=TRUE, text= "Tech Rat Protein Janet 1   1.119  Janet 1   1.2996  Janet 1   1.5407  Janet 1   1.5084  Janet 1   1.6181  Janet 1   1.5962  Janet 1   1.2617  Janet 1   1.2288  Janet 1   1.3471  Janet 1   1.0206  Janet 2   1.045  Janet 2   1.1418  Janet 2   1.2569  Janet 2   0.6191  Janet 2   1.4823  Janet 2   0.8991  Janet 2   0.8365  Janet 2   1.2898  Janet 2   1.1821  Janet 2   0.9177  Janet 3   0.9873  Janet 3   0.9873  Janet 3   0.8714  Janet 3   0.9452  Janet 3   1.1186  Janet 3   1.2909  Janet 3   1.1502  Janet 3   1.1635  Janet 3   1.151  Janet 3   0.9367  Brad  5   1.3883  Brad  5   1.104  Brad  5   1.1581  Brad  5   1.319  Brad  5   1.1803  Brad  5   0.8738  Brad  5   1.387  Brad  5   1.301  Brad  5   1.3925  Brad  5   1.0832  Brad  6   1.3952  Brad  6   0.9714  Brad  6   1.3972  Brad  6   1.5369  Brad  6   1.3727  Brad  6   1.2909  Brad  6   1.1874  Brad  6   1.1374  Brad  6   1.0647  Brad  6   0.9486  Brad  7   1.2574  Brad  7   1.0295  Brad  7   1.1941  Brad  7   1.0759  Brad  7   1.3249  Brad  7   0.9494  Brad  7   1.1041  Brad  7   1.1575  Brad  7   1.294  Brad  7   1.4543  ")

I have data that were collected at a number of sites, and each site was located within one of three zones (Lake Ontario, Erie and the St. Lawrence), so I was hoping to do nested ANOVAs to compare between sites and zones. Unfortunately I have an unequal number of sites in each zone (3, 4 and 5 respectively) due to not enough data being collected at a couple sites. Also, my variances and sample sizes are also not equal between sites (sample size running from 3 to 43, I know, terrible!). The total number of observations for all sites was 182. Most sites had around 15 observations  My question is, is it possible for me to do nested analysis of some sort? I can't find much information on nested analysis with unequal variances.  I have tried transforming, the closest I can get to homoscedasticity is with $x_{new}=\frac{1}{(x+2)}$, and that gives me a $p \approx 0.02$


I generate a professional card HTML with JavaScript:  var professionalsCards = ''; $.each(professionalsData, function(i, item) {     professionalsCards += '
';     professionalsCards += '';     professionalsCards += '
';     professionalsCards += '';     professionalsCards += '
'+item.fullname+'
';     professionalsCards += '<input type="hidden" id="professional_uuid" name="professional_uuid" value="teste" />';     professionalsCards += '

'; });  $("div#professionals_list").html(professionalsCards);   When i Populate it with HTML Directly the click function of jQuery work fine:  $(".professional_list_card").click(function(event) {     event.preventDefault();     var professional_uuid = jQuery(this).find("input:hidden");     alert(professional_uuid.val()); });   But, when i insert the HTML with JavaScript the function click of jQuery not work. Then i tried make a function and use onclick, not work too:  function showProfessionalDetails() {     var professional_uuid = jQuery(this).find("input:hidden");     alert(professional_uuid.val()); }   How i control the HTML inserted with JavaScript? Click and Other Events?  Thank You!

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


I have this code sample to Copy files and directories from one location to another. But this exception keep showing every time I run the program. Can anyone please help me find out the error?   Exception in thread "main" java.lang.NullPointerException  public void listFilesAndFilesSubDirectories(String directoryName) throws FileNotFoundException, IOException {     File directory = new File(directoryName);     //get all the files from a directory     File[] fList = directory.listFiles();     for (File file : fList) {         if (file.isFile()) {             //System.out.println(file.getAbsolutePath());             System.out.println("File");              File source = new File("C:\\Users\\Core i3\\Desktop\\Check me\\" + file);             File dest = new File("C:\\Users\\Core i3\\Desktop\\New folder");             System.out.println(source);              InputStream is = null;             OutputStream os = null;             try {                 is = new FileInputStream(source);                 os = new FileOutputStream(dest);                 byte[] buffer = new byte[1024];                 int length;                 while ((length = is.read(buffer)) > 0) {                     os.write(buffer, 0, length);                 }             } finally {                 is.close();                 os.close();             }          } else if (file.isDirectory()) {             listFilesAndFilesSubDirectories(file.getAbsolutePath());              System.out.println("Directory");              File source = new File("C:\\Users\\Core i3\\Desktop\\Check me\\" + file);             File dest = new File("C:\\Users\\Core i3\\Desktop\\New folder");              InputStream is = null;             OutputStream os = null;             try {                 is = new FileInputStream(source);                 os = new FileOutputStream(dest);                 byte[] buffer = new byte[1024];                 int length;                 while ((length = is.read(buffer)) > 0) {                     os.write(buffer, 0, length);                 }             } finally {                 is.close();                 os.close();             }          }     }  }


Had a little doubt in one case. If I have a variable declared in global scope, I know it gets attached to window object.  var var1 = 'Apple';   If I have a variable declared in a function, that variable is in functional scope.  function testFunc() {    var var2 = 'zebra'; }   But if I invoke a function and pass a parameter, I know an assignment operation happens.  eg 1) function testFunct(param1) {         console.log('which scope is param1');       }       testFunct('Mango');   I know assignment operation var param1 = 'Mango'; happens, but where? at invoking place or when invoked? And what is the scope of param1, global or functional.  And if a global variable was declared and passed in invocation,   eg 2)  function someFucntionCall(param) {          console.log('what is the scope of param here');        }        var someVar = 'Merc';        someFucntionCall(someVar);  //global variable declared and passed in function invocation   What is the scope of param here? Bit confused in these, couldn't find proper explanation anywhere.

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


I'm trying to format bibtex entries of type unpublished (for Working Papers) like those of type article. That is, institution + series shall be formatted as if it was the name of the journal.  This is my bibtex entry:  @unpublished{SomeKey,     title = {bst files are difficult},     year = {2015},     author = {Author, Unknown},     series = {Discussion Paper},     institution = {Bibtex-Institute} }   To do so, I'm tweaking the  style:  FUNCTION {unpublished} { output.bibitem   list.label.output   " \harvardyearleft " list.year * "\harvardyearright " * output.nonnull   author "author" item.check   title.field field.used =     { skip$ }     { format.title quote "title" output.check }   if$   institution emphasize output   series emphasize output   new.block   fin.entry }   which outputs  Author, U. (2015), 'bst files are difficult', Bibtex-Institute, Discussion Paper. How do I get rid of the comma between the fields institution and series?  The original function was:  FUNCTION {unpublished} { output.bibitem   list.label.output   " \harvardyearleft " list.year * "\harvardyearright " * output.nonnull   author "author" item.check   title.field field.used =     { skip$ }     { format.title "title" output.check }   if$   new.block   note "note" output.check   fin.entry   write.url }

I just started modifying my ieeetr.bst file.   I was able to switch first and last name for my (journal article) authors in the bibliography. I also wanted to display the Volume and Issue number as 1(1) and not vol. 1, no. 1. So far I only got to 1, (1).  Any ideas how I can get rid off the space and comma?


I'm trying to run a few tests using princomp in R.  In princomp there is a value called loadings, which is supposed to show many things.  One of those things is the proportion of variance explained by each principal component.    For some reason, the principal components using this tool in R always come out such that the proportion of variance is the same for all components!!  For example, try this on the iris dataset:  data = iris[c("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width")] iris_fit <- princomp(data, cor=TRUE)   then, when I print out the loadings, I see this:  iris_fit$loadings  Loadings:              Comp.1 Comp.2 Comp.3 Comp.4 Sepal.Length  0.361 -0.657 -0.582  0.315 Sepal.Width         -0.730  0.598 -0.320 Petal.Length  0.857  0.173        -0.480 Petal.Width   0.358         0.546  0.754                 Comp.1 Comp.2 Comp.3 Comp.4 SS loadings      1.00   1.00   1.00   1.00 Proportion Var   0.25   0.25   0.25   0.25 Cumulative Var   0.25   0.50   0.75   1.00   All of the Proportion Var row is 0.25, meaning that the variance is split evenly across the components.    So, I tried a few other datasets with, for example 2 or 3 features.  And, every time, the Proportion Var is 1 divided by the number of features!  Why is this?  I want to be able to use this for feature selection, and it makes it difficult to select components/features when they are all the same.   Why is this?

Example code:  (pc.cr <- princomp(USArrests))   summary(pc.cr) loadings(pc.cr)  ## note that blank entries are small but not zero   I am getting different outputs from each, and I am not sure I understand what the difference is.  Here is the output:  > summary(pc.cr) Importance of components:                            Comp.1      Comp.2      Comp.3       Comp.4 Standard deviation     82.8908472 14.06956001 6.424204055 2.4578367034 Proportion of Variance  0.9655342  0.02781734 0.005799535 0.0008489079 Cumulative Proportion   0.9655342  0.99335156 0.999151092 1.0000000000   > loadings(pc.cr)  ## note that blank entries are small but not zero  ...                 Comp.1 Comp.2 Comp.3 Comp.4 SS loadings      1.00   1.00   1.00   1.00 Proportion Var   0.25   0.25   0.25   0.25 Cumulative Var   0.25   0.50   0.75   1.00   P.S: how can I get access to the table created by summary(pc.cr)?? (I can't seem to find it in str.)


How i can get all created types of an assembly when it's running ? I used reflexion but it can retrieve all types but not just instantiated types.  Example: After Runing the assembly.exe I want to get  System.Object   10 Instances System.String   102 Instances System.Char[]  10 Instances ....   So how we can do it ?

We need to get all the instances of objects that implement a given interface - can we do that, and if so how?


Which usage of the prefix, "Meta" is correct, "Metaprogramming" or "Meta-programming"? Should the word be hyphenated or not?

Possible Duplicate:          What is the proper way to spell "side dish"? Is it: "side dish" or "side-dish"?  Also, Is it "ham-fried" or "ham fried"?  Basically, when do you use hyphens?


I've made a Pluralsight training course for users of my open source library, as a resource to help answer in detail lots of the most commonly asked questions. You do however need to be a Pluralsight subscriber to watch it which isn't free and I get a small royalty cut when people do watch it.  If someone asks a question on SO about a topic that I address in detail in the training course, is it considered OK for me to give a brief answer outlining the general approach to solving the issue at hand, and then point them to the Pluralsight course if they want a more detailed answer?

I've encountered  on SO. At the end of the answer the user has placed a link to his article on a 3rd party site that requires paid subscription before reading articles. This makes the link totally useless. The answer by itself is useful, however. After my downvote with comment why I did so, there was a bit of flame that ended up with a phrase, the paywalled link is useless only for penniless freeloaders, hence the title. Worse than that. I'm a curious guy, so I went the user's profile and looked at the recent answers. Out of five most recent answers, three contain links to the same site: , , and the least one is useless without the content of the article. I did not look in older answers (), and the pattern makes me thinking that the misleading link was not an innocent mistake, but the entire reason this user's presence on SO is promoting a paid site. Again, by itself there's no crime if the links are attributed well. I've read carefully several articles here on Meta:   - I don't think it should be banned.      But I'm still confused. It is more surprising for me to see not a newbie like myself doing that, but someone with 3 years membership and 14k rep (I'm not kidding!).  So, considering the fact that removing bad links is against the major user's goal here, I'd like to know:  Should I flag the answer (and comments within) as spam? If so, what formal reason to be there? "Soliciting"? Should such links clearly say don't go there unless you have a paid subscription? Am I too sensitive, and it's just an innocent bad habit, or "penniless freeloaders" is a real horrible offense? Am I required to submit my own answer before being eligible for downvoting this particular user? :-)  One more thing. I don't care about the personality of this user simply because you can't bring everyone to reason; legio mihi nomen est, quia multi sumus. What I want is just an ability to distinguish misleading links from valid ones.  UPD After reading the answers and comments, I would like to direct the discussion in the following manner: If you tend to prevent any paywalled links:  What to do with really good answers and a decent reputation that people make while answering? SO can't just throw it away;  If you're up to a free speech paradigm:  @Chris:  @Widor:  Also, how these links are to be attributed?


I am asked to set some photos to 1000 pixel in order to make them smaller using the Irfan View program, but the program only accepts in megapixels. So, how many megapixels is 1000 pixel??

I am trying to find out the definition of a megapixel? Some references on the web place it at 1 million pixels, and other places say it is equal to 2^20 = 1,048,576 pixels.


I previously had 2 apple IDs using (1) Gmail and (2) my university email.  The deletion of (1) was completed, requested on Dec 9, 2019, and completed on Dec 25, 2019.  Now I would like to change the email of (2) into the email I previously used for (1). However, the website said that "This email address is not available. Choose a different address."  May I ask what's the issue of this?  Many thanks!

I have tried repeatedly to change my Apple ID and password without success. I have followed all of the directions trying both my emails and asked for new passwords----no luck whatsoever.


I just started to learn Swing, and I encountered a NullPointerException when I try to use the constraints in adding widgets to my content.  Error Trace:  NullPointerException at chapter.pkg6.ImprovedForceCalculator.<init>(ImprovedForceCalculator.java:56) at chapter.pkg6.ImprovedForceCalculator.main(ImprovedForceCalculator.java:36)   Here is my code:  import java.awt.Container; import java.awt.GridBagLayout; import java.awt.GridBagConstraints; import java.awt.Font;  import java.awt.event.ActionEvent; import java.awt.event.ActionListener;  import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JTextField; import javax.swing.JButton; import javax.swing.JOptionPane;  public class ImprovedForceCalculator {     private JFrame frame;     private Container content;     private GridBagConstraints constraints;      private JLabel massLabel;     private JLabel accelerationLabel;      private JTextField massInput;     private JTextField accelerationInput;      private JButton calculateForce;      private double mass;     private double acceleration;     private double force;      public static void main(String[] args)     {         new ImprovedForceCalculator();     }      public ImprovedForceCalculator()     {         frame = new JFrame();         frame.setTitle("Improved Force Calulcator");         frame.setResizable(false);         frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );          constraints = new GridBagConstraints();          content = frame.getContentPane();         content.setLayout(new GridBagLayout());          massLabel = new JLabel("Enter the mass of the object (m): ");         massLabel.setFont(new Font("Times New Roman", Font.PLAIN, 14));         content.add(massLabel);         constraints.gridx = 0;         constraints.gridy = 0;         content.add(massInput, constraints);          massInput = new JTextField();         massInput.setFont(new Font("Times New Roman", Font.PLAIN, 14));         constraints.gridx = 1;         constraints.gridy = 0;         content.add(massInput, constraints);          accelerationLabel = new JLabel("Enter the acceleration of the object (a): ");         accelerationLabel.setFont(new Font("Times New Roman", Font.PLAIN, 14));         constraints.fill = GridBagConstraints.HORIZONTAL;         constraints.gridx = 0;         constraints.gridy = 1;         content.add(accelerationLabel, constraints);          accelerationInput = new JTextField();         accelerationInput.setFont(new Font("Times New Roman", Font.PLAIN, 14));         constraints.gridx = 1;         constraints.gridy = 1;         content.add(accelerationInput, constraints);          calculateForce = new JButton("Calculate Force");         calculateForce.setFont(new Font("Times New Roman", Font.PLAIN, 14));         calculateForce.addActionListener (new ActionListener(){             public void actionPerformed(ActionEvent e)             {                 try                 {                     mass = Double.parseDouble(massInput.getText());                     acceleration = Double.parseDouble(accelerationInput.getText());                     force = mass * acceleration;                      System.out.println("Force: " + force + " newtons");                 }                 catch (NumberFormatException ex)                 {                     JOptionPane.showMessageDialog(frame, "Please enter a valid mass and/or acceleration");                 }             }         });         constraints.gridx = 0;         constraints.gridy = 2;         constraints.gridwidth = 2;         content.add(calculateForce, constraints);          frame.pack();         frame.setVisible(true);             } }

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?


So I'm trying to solve some CTL formulas on a given system using model-checking. I'm trying several different solvers; some of them only accept LTL as input, but have some nice partial-order reductions built-in that I would like to use and should perform well on my systems that feature heavy interleaving. We know the intersection of LTL and CTL is non-empty (e.g. invariants lie there) but do you know of an algorithm to determine if a CTL formula can also be expressed in LTL, and to translate it if so ?

The Baier and Katoen textbook references this paper     E. M. Clarke and I. A. Draghicescu. Expressibility results for   linear-time and branching-time logics, pages 428–437. Springer Berlin   Heidelberg, Berlin, Heidelberg, 1989.   to say that, given a CTL formula P, if there exists an equivalent LTL one, it can be obtained by dropping all branch quantifiers (i.e. A and E) from P.   Is there a syntactic criterion that provides a guarantee that if a CTL formula passes the test, then an equivalent LTL formula does exist?


Nonrelativistic QM can be applied to bound states like a hydrogen atom. QFT is used for free particles (whatever one means by particles) that shortly interact with each other and are free again after the interaction. Can QFT also be used for bound states?

Is there a theorem that says that QFT reduces to QM in a suitable limit? Of course, it should be, as QFT is relativisitc quantum mechanics. But, is there a more manifest one? such as Ehrenfest's theorem which dictates the transition from QM to Classical Mechanics.  I am curious as the basic object in QM is wave function whereas the basic object in QFT is quantized operator, which looks very different, and wondering how the comparison works.  (Of course, I am aware that QFT can calculate corrections for Coulomb potential energy, which may seem to be a transition from QFT to QM, but I want one more manifest than that.)


is related, but different. Here I'm asking if there is a paradox and if my attempt at resolution has merit, and if not where exactly does it fail. Attempt at resolution poses a scenario in which motion of the lab frame is safely assumed to be zero and inertial.    The Earth rotates a full cycle every 24 hours. Alhpa Centauri is 4 light years away. The Newtonian formula for speed of an object moving in a circle is $$\vec{v}=\vec{\omega}\times \vec{r}$$  Where $\vec{v}$ is velocity along the circle, $\vec{\omega}$ is angular velocity and $\vec{r}$ is distance from axis of rotation.   Using the above numbers, we get $v=(2 \pi/24hrs)\times 4lyrs=(\pi/3)(lyrs/hr)$  $$\frac{1 lyr}{1hr}=\frac{1\times c \times 8766hrs}{1hr}=8766c$$  This means $v=(\pi/3)(8766c)>c$, an impossibility.   Does Alhpa Centauri hit superluminal speeds in any coordinate system ? I'm skeptical, based on the following.   Possible Answer  Consider a frame, spinning in the lab about its z-axis, that axis being oriented towards Alpha Centauri. Consider another Cartesian frame not rotating in the lab. Set up a "light clock" in the lab consisting of a light beam bouncing between two mirrors, one on the floor, one on the ceiling, separated by a distance $L$.   The  motion of the light beam moves perpendicularly to the direction of relative motion. So the distances along the z axis are expected to be preserved. The same principle applies to distances along the r-axis. In addition, a light beam moving radially in ward or outward for one frame should have the same motion in the other. It could be detected and this probably null, not only by the above argument, but arguments from isotropy.  Let primes represent measurements in the rotating frame, unprimed, the non-spinning lab frame. By the above, Then for one half tick of the lab's clock $r_0=r_0'$, $\Delta{z}=\Delta {z'}=L$:  $$c\Delta t=L$$ $$c^2(\Delta t')^2=r_0^2 d\theta'^2+L^2$$  Swapping out $L$, and with some algebra:  $$\Delta t'^2=\frac{(\Delta{t})^2}{1-\frac{r_0^2\omega'^2}{c^2}}$$  Where $w'=d\theta'/dt'$. So there is a formula for time dilation.   Letting $\Delta{t}=L/c:$  $$\Delta t'^2=\frac{L^2}{c^2-r_0^2w'^2}$$  Divide both sides into $L^2=\Delta{z'}^2=\Delta z^2$.  $$\frac{L^2}{(\Delta t')^2}=c^2-r_0^2w'^2$$  $$r_0^2w'^2=c^2-\frac{L^2}{(\Delta{t'})^2}$$  So:  $$r_0^2w'^2+\frac{L^2}{(\Delta{t'})^2}=c^2$$  The first term on the left side of the equation represents angular motion. The second term represents motion along the z axis.   $$(\frac{\Delta{z'}}{\Delta{t'}})^2=c^2-r_0^2w'^2$$  The total squared distance traveled according to the rotating frame is $c^2\Delta{t'}^2$. From this we subtract the vertical squared distance traveled, then divide by $\Delta{t'^2}$ to get the sum of the square of the components of other contributors to velocity:  $$v_{alt}^2=\frac{w'^2r_0^2L^2}{c^2-r_0^2w'^2}\frac{1-w'^2r_0^2/c^2}{(L^2/c^2)}=w'^2r_0^2$$  So regardless of any object's position away from the common axis, the square of either component will be less than $c$. So Alpha Centauri is not traveling at the speed of light however far away it might be or however rapidly the earth rotates.

We may choose a non-rotating earth as our reference frame and ask ourselves: how about the planetary and stellar motions. A star at a distance of 10 million light years would turn around the earth in 24h with a velocity of 10^18 m/s.   A friend once told me that actually articles have been published delving into this problem, e.g. to prove that fictitious forces emerge from the choice of such a bizar reference frame that ensure that the earth is still (somewhat) flattened at it's poles.  Questions:  1) Does anybody know of such a publication?  2) I know that even such speeds of 10^18 m/s are not in contradiction with relativity because a limiting velocity only exists for exchange of information, which apparantly does not occur. Still: could anybody explain why such bizar velocities are allowed?


I am working on a django project where I'm suppose to check a date with today's date and if it's difference is of 1 month then there should happen something. Is there any method or any thing that can help me pls do help me.

I've been working on a web app using Django, and I'm curious if there is a way to schedule a job to run periodically.   Basically I just want to run through the database and make some calculations/updates on an automatic, regular basis, but I can't seem to find any documentation on doing this.  Does anyone know how to set this up?  To clarify:  I know I can set up a cron job to do this, but I'm curious if there is some feature in Django that provides this functionality.   I'd like people to be able to deploy this app themselves without having to do much config (preferably zero).  I've considered triggering these actions "retroactively" by simply checking if a job should have been run since the last time a request was sent to the site, but I'm hoping for something a bit cleaner.


We have requirement to restrict access of Sync DE using custom Role Setting to some users , is it possible to restrict access of Synchronized DE in Email Studio and Contact Builder using Role and permission or with some other way?

Can we denied permission for synchronized data extension in Salesforce Marketing Cloud, My requirement is, I don't want to allow users to access synchronized data extension either in contact builder or in Subscribers.


I am having trouble characterizing the types of alternating with-differing-period harmonic series which converge. For example, $\sum_{n\in \mathbb{N}} (-1)^n\frac{1}{n}$ converges, but what about $1+\frac{1}{2} - \frac{1}{3} + \frac{1}{4} + \frac{1}{5} - \frac{1}{6} + \frac{1}{7} + \frac{1}{8} - \frac{1}{9} \dots$ ($2$ positive terms and $1$ negative term). Can we characterize how far the gaps can be between negative terms?

Does the following variant of the harmonic series converge? If it diverges (which I think it does), can I know if it diverges to $\infty$ or has no limit?  Note that the series is not alternating in the classical sense of the word. $$1 + \frac{1}{2} -\frac{1}{3} + \frac{1}{4} + \frac{1}{5} - \frac{1}{6} + \dots$$  The generic term of the series would have to be something like,  $$a_n = \left\{\begin{array}{ll} -\frac{1}{n}, & \text{if } 3 \mid n  \\ \;\, \,\, \frac{1}{n}, & \text{otherwise}\end{array}\right.$$ I'm not sure if it's very helpful. The terms divisible by 3 are negative, and the others are positive.   Is there a way to decide and prove whether an alternating series of this sort (e.g. with a period other than 2) converges? Or one where terms are positive or negative according to some other rule?  Almost all convergence tests I've come across are generally limited to either simple alternating series or where all the terms are positive.


With the following code the Section Title  "Section" appears twice in the header -- once for the first page, once for the other three pages. It seems to me that this is a bug.  \documentclass{beamer} \usetheme{Luebeck} \begin{document} \begin{frame} \section{Section} Text 1\pause\\ Text 2 \end{frame} \begin{frame} Text 3\pause\\ Text 4 \end{frame} \end{document}

I'm making a Beamer presentation. I need to show some notes on a second screen, so I'm using pgfpages.  Whereas, when I put a section, it appears 2 times :/ Here, it's a minimal code with the problem. Have you any idea ?  \documentclass{beamer} \usepackage[latin1]{inputenc} \usepackage[T1]{fontenc} \usepackage[francais]{babel}  \usepackage{pgfpages} \setbeameroption{show notes on second screen=right}    \begin{document} \begin{frame} \tableofcontents \end{frame}  \begin{frame} \section{test} toto \end{frame}  \end{document}   Thanks !


In a particular scenario where there is a tie for same three of a kind.   Two players -   User1 with 10h and 6d  User2 with 10d and 4c  On table 10c, 10s, Kc, 3h, 2d  Who wins?   Note: h/d/s/c = Hearts/Diamonds/Spades/Clubs

player A : 4,4 player B : A,10 board : K,K,Q,Q,2  Which player wins? I guess Player B but player A claims he has a pair of 4 which is a bigger kicker. who is correct?


my if - then statement results to false even though the condition is true  I've tried casting values to doubles      dblCompare = CDbl(rng1.Offset(0, -12).Value2)     If dblTotal = dblCompare Then         'If the values match, then record the Unique IDs in Columns AI:AN         Range(Cells(m, 35), Cells(m, 35 + k - 1)) = arr     End If   dblCompare = 114954.48 and dblTotal = 114954.48.  However, the statement results to false and the pasting of the array into the Range is completely skipped.  Sometimes the if-then statement results to true and the contents of the array is pasted into the range, but sometimes it doesn't.  VBA appears to be very buggy.  All I can think of is that dblCompare needed to be type cast to a Double.  My declarations:   Option Explicit Sub Find_Recs()     Dim i As Integer, j As Integer, k As Integer, m As Integer     Dim strSearch As String     Dim dblTotal As Double, dblCompare As Double     Dim rng1 As Range, rng2 As Range     Dim arr As Variant ' ' 'code here ' ' End Sub

I have trouble comparing 2 double in Excel VBA  suppose that I have the following code  Dim a as double Dim b as double a = 0.15 b = 0.01   After a few manipulations on b, b is now equal to 0.6  however the imprecision related to the double data type gives me headache because  if a = b then  //this will never trigger end if   Do you know how I can remove the trailing imprecision on the double type?


I just took accepting answers for granted on Stack Exchange, but then I came across Quora, a Q&A site that doesn't have accepted answers (Just to be clear, I'm not suggesting that we make Stack Exchange like Quora - there are tons of reasons why SE >> Quora - but we should be open to other ways of doing things). So, I thought about the pros and cons of accepting answers. What I have here is not an exhaustive list, but just what I came up with off the top of my mind just now. Cons of Accepting Answers  The best answer isn't always accepted. Often, the accepted answer and highest voted answer are not the same. For questions with 20 views, this is okay, but on many popular questions, the accepted answer isn't the highest voted. In my opinion, the highest voted answer is the best answer, since I value the community's opinion above that of the OP. There are cases where this isn't true, but the vast majority of the time, it is. The Accepted Answer goes to the top. I wouldn't have any problems with point 1, except that the accepted answer is always at the top. I think that the best answer should be at the top, because some people don't scroll down below it (myself included, oftentimes). Accepting seals the question. What I mean is that to accept an answer to a question is almost the same as closing it. People may still go to it and look at it, but definitely fewer. It reduces the traffic. It discourages better answers. Accepting an answer doesn't mean it is the best possible answer, it just means that it satisfies the OP. But since accepting an answer seals the question, a person who can provide a better answer is unlikely to stroll along and give that better answer.  Pros of Accepting Answers You guys already know these, so I'll just go over a few of them briefly:  In many cases, the "right" answer is showcased by sending it to the top of the list. The answerer of the "right" answer is rewarded with 15 rep. New users can reward helpful answers, if they don't have upvoting privileges yet.  Possible Solutions I'm not sure how to solve the problems of accepted answers without abolishing them - but I think the pros, primarily the first two, outweigh the cons - which is why I'm asking this question here. How can we fix the problems with accepting answers without getting rid of all the benefits?

In the Stack Exchange voting system, we have two classes of votes: standard up / down votes that anyone can cast, and special  that only the asker can.   Although accepting an answer does not always pin it at the top of the answer list, that green check mark does  about the correctness of the answer. This gives a single person much greater weight than the rest of the community. That green check mark can seem confusing to visitors, who see  or  answers marked as being correct. I've heard this from several friends recently who were surprised when they came across factually wrong answers that had been downvoted, yet still had that check mark next to them.  Moderators regularly field flags from even more experienced users who demand that the accepted answer be changed from one that is incorrect or even harmful to another. We decline these, because we're not supposed to be making technical judgments like that and because we have no way of accepting answers on behalf of the asker. However, these flags do show that some people have problems with the presentation of accepted answers vs. the community voting on all the others.  There's also all the fun that came with arguments over accept rate, and people badgering askers to accept their answers.   Questions on the Stack Exchange network are intended to be broadly useful, to help out many others in the future beyond the person asking the question. If that's our goal, why should the person asking the question have any more say than the rest of the world? If it's a broadly applicable question, why should one person be able to highlight something as correct simply because they asked it first?  I guess what I'm asking is: if we did away with accepted answers, converting them to upvotes where appropriate, and only let community voting sort out the best answers, would we lose something important? I thought I'd ask after reading  to , because I wasn't sure how I felt about accepted answers anymore.


I am trying to run the jmx file through java code and got below exceptions:  INFO    2016-09-01 11:35:53.876 [jmeter.e] (): Listeners will be started after enabling running version INFO    2016-09-01 11:35:53.896 [jmeter.e] (): To revert to the earlier behaviour, define jmeterengine.startlistenerslater=false INFO    2016-09-01 11:35:53.899 [jmeter.u] (): Setting Locale to en_US  Exception in thread "main" java.lang.NoClassDefFoundError: com/thoughtworks/xstream/converters/ConversionException     at com.staples.mobilautomation.JMeterFromExistingJMX.main(JMeterFromExistingJMX.java:22) Caused by: java.lang.ClassNotFoundException: com.thoughtworks.xstream.converters.ConversionException     at java.net.URLClassLoader.findClass(URLClassLoader.java:381)     at java.lang.ClassLoader.loadClass(ClassLoader.java:424)     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)     at java.lang.ClassLoader.loadClass(ClassLoader.java:357)     ... 1 more   Please help me to get closure.

I am getting a NoClassDefFoundError when I run my Java application.  What is typically the cause of this?


The Windows (10) Installer directory is massive, over 25Gb for me.  Is there anything that can be tidied up here?  Also, what's it for?  Follow up  As removing it seems like a bad thing can I store it somewhere else?  It definitely doesn't need to be on the SSD.

Has anyone successfully deleted the Windows Installer files successfully before? They are taking up 35.1% of my total hard drive space.  Which ones are needed and which ones can be purged?  In order to see this folder, I had to unhide system files by going to Windows Explorer > Organize (dropdown) > Folder and Search Options > view tab > uncheck ==> Hide protected operating system files (Recommended).  I used WinDirStat program to get these percentages. To see the image in full size, open it in a new tab.  I was told by someone that you should not delete these files, but then I found a utility--Windows Installer CleanUp Utility (very old version) that deleted these.  But it doesn't run on Windows 7.  If anyone has a later version that they found works, please let me know the path.


I remember a series of 7(?) YA books I read in the mid 90's about a boy who started to attend magic school.  At the end of the first book he was expelled for doing something dangerous related to a summoned demon, but was promoted to journeyman wizard.  The rest of the series is him traveling around and training his magic, I distinctly remember the second book he went to learn healing magic.  He was friends with an acrobatic non-magic girl who I want to say was named Lyre or Lyra.  In the final 7th book there's a fairly big war and the main character is magically outclassed by the enemy wizard, but the acrobat friend saves him.

When I was younger (11-12 years old, so the early 2000s) I once read a story where a young boy, who may have been either a young prince or a squire of some sort, is recruited by a wizard and taken to a city to train as a mage.  I seem to remember him living in dorms with the other children at this school, until he gets into difficulty with another of the boys in the dorm. He is kicked out of the dorms and ends up living above a blacksmith shop (I think).  I remember it being the first book in a series of books of which there were about 3 out at the time. I think one of the stories was about the boy going to a tower to do something or other.  Does anyone have any idea what this book series is? I haven't been able to find it for years now but it was a story I really loved.


Yet another question of which is larger: $70^{71}$ or $71^{70}$. I solved it by observing that $f(x)=\frac{\ln(x)}{x}$ is decreasing for all $x>e$ since $f'(x)=\frac{1-\ln(x)}{x^2}<0$ for all $x>e$. Then we have $$ \begin{align*} \frac{\ln(70)}{70}>\frac{\ln(71)}{71} &\iff 71\ln(70)>70\ln(71)\\  &\iff \ln(70^{71})>\ln(71^{70})\\ &\iff e^{\ln(70^{71})}>e^{\ln(71^{70})}\\ &\iff 70^{71}>71^{70}. \end{align*} $$ I briefly search for similar problems along this idea, but didn't really find much in other ideas about how to solve this. So I open this to the group: how else might this be proved?  EDIT: So this problem is a specific case of the more general problem I apparently duplicated. However, we can extend the duplicate problem by allowing real number inputs as opposed to just integer inputs. Thus $x^{(x+1)}>(x+1)^x$ for all reals $x>e$. This is proved following the exact same proof I gave above with the appropriate substitutions: $$ \begin{align*} \frac{\ln(x)}{x}>\frac{\ln(x+1)}{x+1} &\iff (x+1)\ln(x)>x\ln(x+1)\\  &\iff \ln(x^{(x+1)})>\ln((x+1)^{x})\\ &\iff e^{\ln(x^{(x+1)})}>e^{\ln((x+1)^{x})}\\ &\iff x^{(x+1)}>(x+1)^{x}. \end{align*} $$ Thanks for the input everyone!

I aim to show that $$(n+1)^n<n^{(n+1)}$$ for all $n \geq 3$. I tried induction, but it didn't work. What should I do?


Let A, B and B' be subspace of a vector space of V of finite dimensions for which $A\cap B = A \cap B'$ , A + B = A + B' and B subset of B'. Then B = B'. Hint (Use Grassman's Identity) I don't know how to start ta proof, or how to manipulate ta grassman identity

I encountered this question in a document I found on a  google search, it bugged me because my perception keeps telling me I'm wrong no matter what I do.     Let $U$, $W$ and $Z$ be subspaces of a vector space $V$ and the following conditions are satisfied:         $U + Z = W +Z$     $U \cap Z = W\cap Z$     $U \subset W$           Prove that $U=W$   So I tried proving by contradiction that $U$ is not equal to $W$,  by saying there exists some vector $w \in W \setminus U$ and  if $w \in W \cap Z$ then $w \in U \cap Z$ which means $w \in  U$. At this momment my mind is shouting  "This isn't it", and I think I should be using a different approach.


I was taught of using this, now there is a little problem:
text
                           My Js:  function hideMyText() {     $('#mytext').hide(); }   so I did as I was told, but the text flickers now. It is visible for a brief of moment, then disappears. How to make it run immediatly? I know I should hide it with CSS - but its possible to have a different task to do (like here, highlight a text: )

When embedding JavaScript in an HTML document, where is the proper place to put the <script> tags and included JavaScript? I seem to recall that you are not supposed to place these in the <head> section, but placing at the beginning of the <body> section is bad, too, since the JavaScript will have to be parsed before the page is rendered completely (or something like that). This seems to leave the end of the <body> section as a logical place for <script> tags.  So, where is the right place to put the <script> tags?  (This question references , in which it was suggested that JavaScript function calls should be moved from <a> tags to <script> tags. I'm specifically using jQuery, but more general answers are also appropriate.)


I'm making a button for my website. I want to align the button in the middle of the screen with flexbox. But it's not working properly :( It's what I tried.   <!DOCTYPE html> <html lang="en">   <head>     <meta charset="UTF-8" />     <meta name="viewport" content="width=, initial-scale=1.0" />     <title>Document</title>     <style>       body {         display: flex;         justify-content: center;         align-items: center;       }        #click-btn {         background-color: #00ff6b;         border-radius: 100px;         border: none;         font-size: 50px;         padding: 20px;       }        #click-btn:active {         background-color: #00d358;         font-size: 45px;       }     </style>   </head>   <body>     <button id="click-btn">Click Me</button>   </body> </html>    I applied the display flex property to body tag. Result:  I wanted vertical align and horizontal align, but only horizontal align is working. What I want:  Any solution for this?

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


I am building an online game that works with images. The user has to guess who's in the altered image that the website displays. So far so good just that if the user does a google search for the image he can find the answer within seconds.   How should I alter the image in order to get it off the google images search?  EDIT: The images I use are already available on google. eg: Barrack Obama. We use images of well known people in our game. That's why I wanted to edit them and avoid the google search

I am planning to make a game, where I give the user an anime related image and they have to guess where its from.  However, most of the images, specially from popular anime are easy to use on Google reverse search to find and pin point the anime.  I've tried to see if I could make so it would not recognize the image but unhappily my tricks were not good enough.  Original image:    Grey-scale with horizontal flip:    Watermarking:    Puzzling the image with grey-scale:    Grey-scale with horizontal and vertical flip worked for this image but doesn't always work:    Also the above mentioned methods are rather easy for people to guess the anime.  I would like to know if there any good trick, that I could use on my images to make so it would not work on reverse search engines and yet not be so overcomplicated that I can implement on my program.  For example grey-scale, cropping, flipping are rather easy things to achieve in C#.


I'm confused about the index in python. This is my problem: number = "1234567" print(number[-3:1:-3])  Output: 5 Why did the output is only 5 and not 52? When the starting position is in the number 5 and the end position is in the number 1(Am I right?). From the right(SINCE IT IS NEGATIVE SO REVERSE) i count from 5 then skipped 2 spaces then the number 2 should also be included.

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


I am having issues trying to parse / grep / pcregrep potentially multiple line environment variable values from the output of the env system command.  I am trying to get just the variables that start with a certain prefix that may or not be multiple lines.  So far I have been trying variants of this (with a lookahead):  env | pcregrep -M '^PREFIX_\S+\=[\S\s]+(?=^\S+\=.*$)'   But the above returns everything.  I think it is because the middle pattern is greedy with newlines, but I don't know how to get around that.  My problem is that I have no known end pattern, except the start of another variable pattern.  Does anyone know how I might be able to accomplish this task?  Thanks for any information you can provide!

I have this gigantic ugly string: J0000000: Transaction A0001401 started on 8/22/2008 9:49:29 AM J0000010: Project name: E:\foo.pf J0000011: Job name: MBiek Direct Mail Test J0000020: Document 1 - Completed successfully  I'm trying to extract pieces from it using regex. In this case, I want to grab everything after Project Name up to the part where it says J0000011: (the 11 is going to be a different number every time). Here's the regex I've been playing with: Project name:\s+(.*)\s+J[0-9]{7}:  The problem is that it doesn't stop until it hits the J0000020: at the end. How do I make the regex stop at the first occurrence of J[0-9]{7}?


I am sorry if I am posting this question here; I thought that since I am looking for historical evidences of successful people in mathematics, so may not this question be an opinion-based one. And also not duplicate as it is not about getting PhD at later age or the like.    I am 30 years old; I have studied physics to masters degree, even though I liked physics but I left it mostly because I didn't find any strong talent to do a great thing in physics and I thought that I can achieve it in mathematics. It's been a few months that I have started mathematics from scratch and I am spending average 14 hours a day learning maths. Though I have found mathematics more fascinating than any other things but my strong stimulus to go ahead especially as a self-learner is hope to do a ground-breaking research and be successful in that.   My questions are:  1- Will my mind be biologically too old to do comparable to what Fields medalists or other brilliant people have done or maybe more (like Perelman's work)?   2- Would you let me know even one person in history who started or turned to maths at their 30s or late 20s, but did famous works?  Some notes:    My question is not about getting a PhD in late ages or be successful in finding an academic position (including research), although soon or late I have to get a PhD in math as well, especially because of being in math community and other advantages. BTW, works that are not considered breakthrough or even writing books in math for students are as invaluable as e.g. Perelman's work, I believe. Please consider that my questions are not about comparisons.      There were some people in history who got their academic degrees at old ages but they were 'in' mathematics from theirs youth or even childhood; so examples of these people aren't relevant since by starting math now I mean that I am 30, and I am just starting undergraduate books in maths.  Physics is not math or even close! For example, I learnt differential forms in general relativity texts but it was just about 10 pages in 430-page physics text. And now I see that almost everything in a simple topology text is new for me.    Thanks to everyone for reading and taking the time for the great responses. Really appreciate it!

I'm sorry if this question goes against the meta for posting questions - I attached all the "beware, this is a soft-question" tags I could.  This is a question I've been asking myself now for some time. In most areas, there's a "cut off age" to be good at something. For example, you're not going to make the NHL if you start playing hockey at 20. It just won't happen.  So my question then, how late is too late to start studying math and make a career out of it? By "start studying math" I mean, to really try to understand and comprehend the material (as opposed to just being able to do well in a formal, intuitional environment).   I don't mean this from a "do what you love, its not too late" motivational perspective. I mean this from a purely biological perspective; at approximately what age has your brain's capacity to learn effectively and be influenced by your learning stop? When does the biological clock for learning new math run out?  My reasoning for asking this question is (for those who care): I love math. Really I do. But , having spent the first 21 years of my life in sports/video games/obtaining a degree in a scientific field which I care nothing of/etc, despite all my best attempts at trying to learn math, am I just too late starting to ever actually be good enough at it to make it a career? I've almost completed my second degree (in Math), but find that in many cases, despite how I look at a problem, I lack the intuition to comprehend it. I'm going to single him out (sorry), only as an example, but Qiaochu Yuan is my age.   Note 1: If this question isn't a suitable post, I won't be offended at all if you vote to close - I know this question borders what's acceptable to ask.  Note 2: Thanks to everyone for reading and taking the time for the great responses. Really appreciate it!


I have come across heap errors while loading a large dataset into Jena. `Is there some way by which I may allocate the JVM(Java) a large heap space.   I know I can achieve this by making changes into eclipse.ini. But is there some way by which I may increase the Java heap size using command line in linux (I using a 64GB RAM server: running 12.04 Ubuntu LTS server)?  The error which I am getting due to less heap space is: exception in thread main gc overhead limit exceeded.  Also how can I find the maximum amount of heap space which I can set for my systems  I tried export JAVA_OPTS= -Xms4096m -Xmx4096m but ended up getting the error: bash: export: -Xms4096m': not a valid identifier bash: export:-Xmx4096m': not a valid identifier

I am writing a client-side Swing application (graphical font designer) on Java 5. Recently, I am running into java.lang.OutOfMemoryError: Java heap space error because I am not being conservative on memory usage. The user can open unlimited number of files, and the program keeps the opened objects in the memory. After a quick research I found  and others saying on Windows machine the JVM defaults max heap size as 64MB.  Given this situation, how should I deal with this constraint?  I could increase the max heap size using command line option to java, but that would require figuring out available RAM and writing some launching program or script. Besides, increasing to some finite max does not ultimately get rid of the issue.  I could rewrite some of my code to persist objects to file system frequently (using database is the same thing) to free up the memory. It could work, but it's probably a lot work too.  If you could point me to details of above ideas or some alternatives like automatic virtual memory, extending heap size dynamically, that will be great.


When Alex Jones is imprisoned in the makeshift shower/bath torture area made by Keller Dover. He says during one scene “I’m not Alex.” But then he says “I waited but he never came” “ I just wanted to play but he never came” .... this part confuses me, who is Alex referring to when he says “he never came?” Is this is real dad? Another kid who was kidnapped? If anyone can help explain who is the “he never came” that would be awesome. Thanks

While captured in the "wooden" prison in Prisoners, Alex Jones says: "I waited but he never came". Who is he referring to?


In publications the wording often resembles the following: "We found that our results followed what we found in our previous research."  I am now writing a publication alone, with no co-authors.  Is it bad form to use "my" in place of "our" in such cases?

Which personal pronoun is appropriate in single-author papers - 'I' or 'we'? Could the use of 'I' be considered egotistical? Or will the use of 'we' be considered to be grammatically incorrect?


I was watching The Force Awakens and there is a line uttered by Han Solo in the film in regards to Rey's comment regarding the Jedi.  She has been on Jakku for a long time and she is very young, so it makes sense that she is out of the loop when it comes to the time line thirty years before.  But Han says, when Rey says, "The Jedi were real!",       Han:  "I used to wonder about that myself.  Thought it was a bunch of mumbo jumbo..."   And we know that he was not really a believer in the Force.  But how could he not know that the Jedi were real.  He was 10 at the time of Revenge of the Sith and he must have grown up with the Old Republic so he must have heard stories of the Jedi "Betrayal" of the Republic once the Empire took over and must have heard about the Jedi being wiped out.  Also, as Chewbacca knew Yoda, how would he not believe that they were real?  This seems far fetched...

I always wondered why Admiral Motti and Governor Tarkin in the movie  insinuate that the Force is an old, dead religion?  :     The Jedi are extinct, their fire has gone out of the universe. You, my friend, are all that's left of their religion.   :     Don't try to frighten us with your sorcerous ways, Lord Vader. Your sad devotion to that ancient religion has not helped you conjure up the stolen data tapes, or given you clairvoyance enough to find the rebels' hidden fortress...   Tarkin, as human, must be around age 50, so, if in Episode IV Luke is about 20, when he was just born at the end of Episode III, Tarkin must have been around 30, so a perfect young man in a Galaxy that used to know Jedis, Jedi Council, Force etc..  Why, 20 years later, he just looks like someone who never saw a Jedi/Sith? Also, besides from Force sensitives (Obi-Wan, Yoda, Vader, the Emperor), nobody else looks like they ever heard of the Force ... that's really weird, isn't it?


Possible Duplicate:        OK, So I am somewhat new to the idea of OOP in JS.   What is the difference between these two snippets of code written below:  function animal(){     this.name = 'rover';     this.set_name = function(name){          this.name = name;     } }     function animal(){     this.name = 'rover'; } animal.prototype.set_name = function(name){     this.name = name; }   They both do the same thing, so what’s the difference?

What's the difference between  var A = function () {     this.x = function () {         //do something     }; };   and  var A = function () { }; A.prototype.x = function () {     //do something };


Current URL:  example.com/renault-cars/duster/  What is the possibility of gaining an SEO advantage after optimizing above URL to?  example.com/renault/duster  Optimizations:   Removed unnecessary "-cars" keyword.  Removed unnecessary "/"

Does it make any difference to SEO ratings what-so-ever if your url has a trailing slash:  http://www.example.com/some/slug/paths/   as opposed to one that does not:  http://www.example.com/some/slug/paths


I have to create 3 class (Card, Deck and Tester) to play a game of card. The rules are easy, just compare two cards randomly from the deck and whichever one is higher is the winner. It runs for the entire deck. Here's my card class (I exclude my comments)  public class Card { private int value;  private String suit;   public Card(){      value =1;      suit = "clubs"; } public Card(int n, String s) {      n = value;      s = suit; } public int getValue() {       return value;  } public void setValue(int n) {      if ((n >0) && (n<14)) {         n = value;     }     else {          return;     } } public String getSuit() {      return suit; // return the string } public void setSuit(String s) {      if ((s.equals("clubs") || (s.equals("hearts") || (s.equals("diamonds") || (s.equals("spades")))))){         s = suit;     }     else {          return;     } } public int rank() {      int rank=0;     int suitVal=0;     if (suit.equals("clubs")) {          suitVal =1;     }     else if(suit.equals("diamonds")) {          suitVal =2;     }     else if(suit.equals("hearts")) {          suitVal =3;     }     else if(suit.equals("spades")) {          suitVal =4;     }     rank= (4*(value-1)) + suitVal;      return rank;    }   }    Deck class:  import java.util.ArrayList;       public class Deck {             int[] value= {1,2,3,4,5,6,7,8,9,10,11,12,13};             String[] suit= {"clubs", "diamonds", "hearts", "spades"};             public ArrayList<Card> card = new ArrayList<Card>();        public Deck() { // make default constructor             for (int a=0; a< value.length; a++) {             for (int b=0; b< suit.length ; b++){                  card.add(new Card(value[a], suit[b]));            }     } }   public Card drawCard() {     int number = (int) Math.random()* (card.size());     Card temp = card.get(number);     card.remove(number);     return temp;     }     Tester:  public class Tester {  public static void main(String[] args) {      Deck deck1 = new Deck();     Card x = deck1.drawCard();     Card y = deck1.drawCard();      int point1=0;     int point2=0;     int player=x.rank();     int comp=y.rank();     for (int i=0; i<52; i++) {         if (player > comp) {             point1++;         }         else {             point2++;         }     }     if (point1 > point2) {         System.out.println("Player is the winner");     }     if (point1 < point2) {         System.out.println("Computer is the winner");     }  }      When I run it it says "Null pointer Exception" and point at line 42 of Card class and line 14 of Tester class. Please help

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?


Was Captain Archer's "Enterprise" ever mentioned or acknowledged on the original series of Star Trek (or any series prior to when "Star Trek: Enterprise" was made)? Even if it wasn't actually mentioned, from the evidence of the earlier (broadcast-wise) shows, is it actually possible that a previous starship called "Enterprise" could exist?  I am wondering whether this was a complete ret-con, and since Kirk's "Enterprise" had no letter following it (and the following ones did), it would seem to suggest that the writers had intended that this was the first of its name.

With the obvious exception (for the most part) of the 2012 film, Star Trek movies and TV series generally stay pretty true to canon in terms of in-universe history.  So I began to wonder, as I'm now watching through the Enterprise series, if any of the people, places, or things from the prequel series were ever talked about in earlier works?  Was there ever mention of Jonathan Archer, the NX-01, a Temporal Cold War, or any other foundational elements of the Enterprise series before that series was produced?  Or were all these pieces covered solely within the Enterprise timeline?  NOTE:  I'm not looking for any crossover episodes where Enterprise just happens to cover some well-known element of Star Trek universe history.  I'm looking for anything to show that the Star Trek universe had historical information about core series components like the NX-01, Jonathan Archer, et. al. before Enterprise was created - something that shows, for example, that "Jonathan Archer" wasn't just pulled from a hat when the creators were looking to name the captain of Starfleet's first Enterprise.


I have mototrbo radio software (server) running on a PC with internet access. I need to install a client on another PC in a different town, and have this PC looking at the information on the other one.  I have been told I need a fixed IP address at the server end.  Is this true and if so is there any way to do this without having a fixed IP line installed seperately.  Apologies for my lack of knowledge....

How can a computer with dynamic IP work as a WebServer?


Lately my computer CPU temp has been higher while idle than usual. I started looking around in Task Manager to see what's sucking up the CPU. At first Windows Explorer was hogging it. After a few restarts and file scans to fix corrupt files Windows Explorer no longer hogs it. However, COM Surrogate now uses CPU a lot. I read that Windows Explorer creates COM Surrogate to help it.  Anyway, after some more google searches, I read that dllhost.exe may be a problem and malware can often be found in a dllhost.exe file. So I go to Resource monitor, and sure enough there are two dllhost.exe programs running. One uses a lot of CPU, the other not so much. In C:\Windows\System32 I found suspicions looking dllhst3g.exe    Does this look like a problem, or not to worry about it? If so, how can I fix? I ran a full scan using Windows Security and all it found was Cheat Engine Malware, which I read is installed by Cheat Engine's installer. They have both been blocked. I have not run Microsoft Defender Offline but would be the next step. I am afraid of it taking another 4 hours like the full scan did.

What should I do if my Windows computer seems to be infected with a virus or malware?  What are the symptoms of an infection? What should I do after noticing an infection? What can I do to get rid of it? how to prevent from infection by malware?   This question comes up frequently, and the suggested solutions are usually the same. This community wiki is an attempt to serve as the definitive, most comprehensive answer possible. Feel free to add your contributions via edits.


For instance, when someone asks for you to fix their computer or their cell phone and you just say that you don't how to solve that problem, even if you do know.

I was reading an online editorial a week or so ago in which its author employed an awesome word, the meaning of which was "to intentionally and deliberately withhold information [essential to the endeavor at hand, with the underlying purpose of misleading others by its omission]". Yeah, all of that in one word.  Alas, I can't seem to find the editorial online anymore, I've now I forgotten the word!


I have two identical objects in my Unity scene. When I change the texture of one, the texture is changed on the other, almost as though the first one is a prefab. Why is this happening and how can I treat them independently?  Steps taken:   Import .obj file and two .png files Drag object into scene Look at the object in the hierarchy (where the list of all objects in the scene is) It has a child called pSphere1 pSphere1 has a mesh renderer with 2 materials on it - RedGold and pSphere1Mat It also has two components controlling each of these materials In those control components, I can select a shader from the dropdown and I can also select a texture. For either one of them, if I change the texture say to PolkaDots, both objects have their materials changed, instead of only the one I am working on.

I'm working on a Unity's Project and I want to modify a prefab, more precisely I want to change the texture of a prefab. The problem is that my modification is applied also to other prefabs. I read on the documentation how each of the buttons labeled Select, Revert and Apply works, and what I understood is that the modification should update only the selected prefab.  Here is the  which I read.  What am I missing?  PS: I'm not the author of the project, I have to apply some modifications only.


I can log in to the server and connect to the instance of SSMS in the server but I can't connect to the same instance from other servers using ssms. how can I fix this?

I have created a C# application which uses a SQL Server database. I have other computers connected to me and to each other in a workgroup. I have shared my C# application with others. When they open the application they get the error      A network related or instance-specific error occured while establishing a connection to SQL Server. the server was not found or was not accessible   But the application is working fine on my PC. The connection string I am using is   Data Source=ASHISHPC1\SQLEXPRESS;Initial Catalog=ACW;User ID=ash159;Password=ashish159   which is stored in a .config file.   The application is working fine on my PC. What must I do? I have enabled the TCP/IP in the server but the same error persists. Some change in connection string or something else?


I am writing a paper which will eventually include several of (my own) computer-generated illustrations.  However, I have found a similarly-styled image in another paper (not mine) which clearly and attractively explains a preliminary point that I am trying to make.    Is it appropriate to use this image (with credit, of course) as an inset in my own paper?  I am genuinely not sure.  I have heard of people who avoid this practice so much that they will reproduce almost exactly the same image on their own, but I am not sure if this is strictly necessary.

So, I've seen a really nice figure in a paper; what's the best way to 'get a copy'?  Will it be on the publisher's website? Do I need to draw my own version? Email the author?  And, finally, how does the answer vary for (a) those wishing to republish the figure in their own work, (b) those not wishing to publish the figure e.g. for student coursework.


Are the datum and the ellipsoid the same? What is a Datum?     The Earth is shaped like a flattened sphere. This shape is called an   ellipsoid. A datum is a model of the earth that is used in mapping.   The datum consists of a series of numbers that define the shape and   size of the ellipsoid and it's orientation in space. A datum is chosen   to give the best possible fit to the true shape of the Earth.  in this   article....

What's the difference between a projection and a datum?


I got stuck a little bit and I could use some help. Thanks in advance for your time!     Let $f_n$ be a sequence of continuous functions and $f_n$ uniformly converges to $f$.   Prove that f is also a continuous function.

Let $f$ be a function from a metric space $X$ to a metric space $Y$. Show that if $f$ is uniformly continuous on $X$ then $f$ is continuous on $X$. Show that the converse is not true.  Uniform continuity definition:  $∀ε>0:∃δ>0:∀p,q∈X:d_{X}(p,q)<δ⟹d_{Y}(f(p),f(q))<ε$  Continuity definition:  $∀ε>0:∀p∈X:∃δ>0:∀q∈X:d_{X}(p,q)<δ⟹d_{Y}(f(p),f(q))<ε$  I wonder if these proofs are correct and if they are formal enough?    Uniform continuity ⟹ Continuity   Let $f$ be uniformly continuous. Fix $ε_{0}$, obtain $δ_{0}(ε_{0})$ (as a function of $ε_{0}$), fix any $p_{0}$ and $q_{0}$ and we know that:   $d_{X}(p_{0},q_{0})<δ_{0}⟹d_{Y}(f(p_{0}),f(q_{0}))<ε_{0}$   If we want to prove that $f$ is continuous at $p_{0}$, we fix $ε_{0}$ and we pick the same $δ_{0}$ as above and fix any $q_{0}$ and we are assured by 1. that   $d_{X}(p_{0},q_{0})<δ_{0}⟹d_{Y}(f(p_{0}),f(q_{0}))<ε_{0}$   Since $p_{0}$ was arbitrary, $f$ is continuous at $X$.     Continuity $\color{red}{\implies}$ Uniform continuity   Let $f$ be continuous. Fix $ε_{0}$, fix any obtain $p_{0}$ and $p_{1}$, obtain both $δ_{0}(ε_{0},p_{0})$ and $δ_{1}(ε_{0},p_{1})$ (not necessarily equal), fix any $q_{0}$ and $q_{1}$ and we know that:   $d_{X}(p_{0},q_{0})<δ_{0}⟹d_{Y}(f(p_{0}),f(q_{0}))<ε_{0}$  $d_{X}(p_{1},q_{1})<δ_{1}⟹d_{Y}(f(p_{1}),f(q_{1}))<ε_{0}$   For $f$ to be uniformly continuous, if we fix $ε_{0}$, obtain $δ$, fix any $p_{0}$, $p_{1}$, $q_{0}$ and $q_{0}$ we must have that:   $d_{X}(p_{0},q_{0})<δ⟹d_{Y}(f(p_{0}),f(q_{0}))<ε_{0}$  $d_{X}(p_{1},q_{1})<δ⟹d_{Y}(f(p_{1}),f(q_{1}))<ε_{0}$   But those two implications need not hold for the same $δ$ as shown above. Suppose we pick $δ_{0}$ and w.l.o.g. we suppose $δ_{0}>δ_{1}$. Then it could be the case that   $δ_{1}<d_{X}(p_{1},q_{1})<δ_{0}$  but we cannot conclude ⟹$d_{Y}(f(p_{1}),f(q_{1}))<ε_{0}$.  Therefore, continuity does not imply uniform continuity.


There is problem installing Ubuntu on my computer.   Error : Failed to load ldlinux.c32   This error occurs when it starts to boot.

This is the third time I've tried to install Ubuntu Server 14.04.03 64-bit on the same laptop, and each time it caused different problems.  Each time I wrote the same iso image to a USB flash drive by using a different application and OS.   Universal USB Installer (pendrivelinux.com) from Windows WinImage writer from Windows built-in image writer from Linux Mint 17.2    The iso image is the same in all three cases, the USB flash drive is the same, and the laptop is the same. However each time the installation of Ubuntu gave me different installation options. For example, the last time I installed Ubuntu, it didn't show all the packages to choose while installing (Basic Ubuntu server, etc.).


How to prove the following   If $g\circ f$ is one-to-one and $f$ is onto, then $g$ is one-to-one.  Any assistance would be appreciated.

Let $f:A\rightarrow B$ and $g:B\rightarrow C$ be functions, prove that if $g\circ f$ is injective and $f$ is surjective then $g$ is injective.  I need advise or correction if something is incorrect with my proof. Thank you beforehand.  We must show that $g$ is injective, i.e for $x,y\in B, g(x)=g(y)\implies x=y$  Let $x,y\in B$ such that $g(x)=g(y)$. Because $f$ is surjective there exists $a,b \in A$ such that $f(a)=x$ and $f(b)=y$  $\implies g(f(a))=g(f(b))$  $\implies g\circ f(a)=g\circ f(b)$  $\implies a=b$ (by injectivity of $g\circ f$)  $\implies f(a)=f(b)$  $\implies x=y$  Would appreciate any correction in proof writing also!


I found that planting lollipops will increase the growth rate up to 100 and that you generate triple that with the dust you find. Also lolligators help make more. What else is there and how does it affect growth rate?

I have pumped my lollipop rate to 100/s, but it took a long time to go from 99 to 100. Is it even possible to get higher or should I stop?


Let $m,n\in\mathbb{Z}_{>0}$ and let $k[\textbf{z}]:=k[z_{ij}\ |\ 0\leq i\leq m,\ 0\leq j\leq n]$ be the polynomial in ring in the $(m+1)\times (n+1)$ free variables $z_{00},...,z_{mn}$. Consider the homogeneous ideal $$ I=\left(z_{ij}z_{i'j'}-z_{ij'}z_{i'j}\ |\ 0\leq i,i'\leq m,\ 0\leq j,j'\leq n\right). $$ Can one show by elementary means that $I$ is radical? I already know that the vanishing locus of $I$ is irreducible, so if $I$ is radical then it is automatically prime.

I want to prove the  over a field are prime ideals. To be concrete:      For simplicity, let $I=(x_{11}x_{22}-x_{12}x_{21},x_{11}x_{23}-x_{13}x_{21},x_{12}x_{23}-x_{13}x_{22})$ be an ideal of the polynomial ring $k[x_{11},\ldots,x_{23}]$. I have no idea how to prove that $I$ is a radical ideal (i.e. $I=\sqrt{I}$). Could anyone give some hints?   Generally, let $K$ be an algebraically closed field, then $\{A\mid\mathrm{Rank}(A)\leq r\}\subseteq K^{m\times n}$ is an irreducible algebraic set (I first saw this result from ). And I tried to prove this by myself, then I have proved it (when I see the "Segre embedding").      But I have no idea how to show that the "determinantal ideals" are radical ideals (I hope this is true). BTW, is the statement that the determinantal ideals over a field are prime ideals true ?   Thanks.


Consider the function $f:\mathbb R\to \mathbb R$ and $g:\mathbb R\to \mathbb R^+$ (in that question $\mathbb R^+$ is a set of nonnegative real numbers). And let define for any $x$ in domains of this functions $f(x)=x^2$ and $g(x)=x^2$. And if we look at set-theoretical definition of function it seems this functions must be equal, because $f$ contains all elements of $g$ and vice versa. But $f$ is not surjective but $g$ is. Isn't it a contradiction ? Or maybe I made a mistake and this functions are not equal, so are this functions equal ?

When do two functions become equal?  I have stumbled over this definition of equality of functions in elementary real analysis.     Let $X$ and $Y$ be two sets. Let $f:X\rightarrow Y$ and $g:X\rightarrow Y$ be two functions. $f=g$ iff $f(x)=g(x)$ for all $x\in X$.   Of course, this definition is so standard and I have no problem with it. However, as far as I know, this definition is actually a theorem. It can be proved in ZFC set theory. A function is just a set of ordered pairs (with some conditions). Two sets are equal if they have the same elements (the Axiom of Extensionality). With this assumption, one can prove the above definition. However, the proof does not require that the ranges of $f$ and $g$ have to be the same.   Suppose that the ranges are different, let's say $f:\mathbb{R}\rightarrow\mathbb{R}$ defined by $f(x)=x$ and $g:\mathbb{R}\rightarrow\mathbb{C}$ defined by $g(x)=x$. If we consider these functions as sets of ordered pairs, then they are just the set $\lbrace (x,x):x\in\mathbb{R}\rbrace$. Thus they are equal by the Axiom of Extensionality. However, the equality also requires that if objects $a$ and $b$ are equal, then any property which is true for $a$ is also true for $b$. In this case, we know that $f$ is a surjective, but $g$ isn't. Thus $f$ should not be equal to $g$ and hence a contradiction. But this is not a proof by contradiction to show that the ranges must be equal, everything assumed here is just axioms of ZFC and what is equality itself. So it looks like it is inconsistent.  I have searched similar questions in this website, but there is no question or answer that relate to this. The most related answer would be $f$ and $g$ must have the same range so there would be no problem. But logically, this is just an additional assumption to restrict the ability to compare two functions. If they don't have the same range, then you can't compare it, or there will be a paradox. The problem for this answer is, it doesn't solve the above paradox. It just restricts itself to the situation that the paradox won't arise, but the inconsistency is still there.  Lastly, I found another way to solve this problem in a set theory book. In the book, when one considers surjection, one have to specify which set the surjection is over. For example, one has to say whether it's surjection over $\mathbb{R}$ or surjection over $\mathbb{C}$. In this case, the paradox won't arise because $f$ and $g$ are both surjective over $\mathbb{R}$ and not surjective over $\mathbb{C}$. Thus the surjective property are the same for $f$ and $g$. The only problem for this answer is, if one consider the property of 'surjection over its range' instead, then this property is true for $f$ but not for $g$, which implies that $f\neq g$ again.  When do two functions become equal in general? Can anyone clarify this for me?  Thank you in advance.


It is a small sensor which activates relay when there's dark.  I just want that circuit to work with 5Vdc or 6Vdc.

I've implemented above circuit and it was successful.  The given circuit needs 12VDC to run properly.  I want to run this circuit on 5-6VDC or 9VDC whichever is possible. I know I have to change resistors but not confirmed which to use.  Also if I use 9V battery only to activate 6V relay for 8hrs daily, for how many days will that battery work?


I'm trying to find  Triangular numbers that are also square. So $m^2=\frac{n(n+1)}{2}$ I don't want the actual answer with the solution but I'd like to  solve the problem myself : I need some clues to take me on the right track.

I'm reading Stopple's A Primer of Analytic Number Theory:     Exercise 1.1.3: Which triangular numbers are also squares? That is, what conditions on $m$ and $n$ will guarantee that $t_n=s_m$? Show that if this happens, then we have:      $$(2n+1)^2-8m^2=1,$$      a solution to Pell's equation, which we will study in more detail in Chapter $11$.   I thought about the following:  $$\begin{eqnarray*}   {t_n}&=&{s_n} \\    {\frac{n^2+n}{2}}&=&{m^2} \\    {n^2+n}&=&{m^2}  \end{eqnarray*}$$  I've solved for $n$ and $m$ but I still have no clue of how to proceed. I've looked at the book's solution and the solution is as follows:   $$\begin{eqnarray*}   {\frac{n(n+1)}{2}}&=&{m^2} \\    {n(n+1)}&=&{2m^2} \\    {\color{red}{4n(n+1)}}&\color{red}{=}&{\color{red}{8m^2}} \\   {4n^2+4n+1-1}&=&{8m^2} \\   {(2n+1)^2-1}&=&{8m^2} \\ \end{eqnarray*}$$  In the red line, he multiplies the equation by $4$, I don't understand why to do it nor how the condition is achieved.