"Far away, in the heavenly abode of the great god Indra, there is a wonderful net that has been hung by some artificer in such a manner that it stretches out infinitely in all directions. In accordance with the extravagant tastes of deities, the artificer has hung a single glittering jewel in each "eye"of the net, and since the net itself is infinite in dimension, the jewels are infinite in number. If we new arbitrarily select one of the jewels and inspect it, we will discover that in its polished surface there are reflected all the other jewels in the net, infinite in number. Not only that, but each of the jewels reflected in this one jewel is reflecting all the others, so there is an infinite reflecting process occurring."    Is the number of jewels + jewel reflections countably infinite or not? How do I prove it?

This question has been asked before, but the title of the post was so general that it received no sufficient answer.  What is the cardinality of the set of jewels and reflected jewels in Indra's Net?   For those who don't know, Indra's Net is a poetic image used in Hindu and Buddhist cosmology to represent the universe. Imagine a grid-like net with a countably infinite amount of intersections and at each intersection there is a jewel. Now, on the surface of each jewel there are reflected images of every other jewel in the net. And since each of these reflected jewels is a copy of the actual jewels, they also have an infinite amount of reflected jewels within them. And within that second level of infinite reflected jewels, each of them also have infinite reflections... and so on, and so on, forever.  Basically, Indra's Net is like the scenario of two ideal mirrors facing each other, only the number of mirrors is countably infinite.  I've been trying to picture this with the number line. The integers could represent the original jewels, and the non-integer rational numbers could represent the first level of reflected jewels. Just pair each integer n with every rational number greater than n but smaller than n+1.  But then, each non-integer rational number would then have to be paired with its own distinct countably infinite group of numbers to represent the second level of reflection, and then every number representing that next level of reflection would in turn need its own distinct countably infinite group of numbers to be paired with, and so on, and so on.   Are there enough real numbers for this? The continuum always surprises me. Thank you.  EDIT: Reading the answers to the first version of this question made me realize how I underestimated the power of the old "1,2,3...".   Now, I have a similar question to my previous one, but I want to change the image of Indra's Net a bit. Imagine the standard image mentioned above, but then project the starting position infinitely "deep down" the levels of reflection so that not only do you see the standard Indra's Net before you, but as you look "outwards" you realize that your position is just one of infinitely many reflections within a larger meta-reflection, which itself is just a one reflection within an even larger meta-meta-reflection, and so on and so on, there being no "actual" jewels to begin with. You can "zoom-in" and "zoom-out" forever in both directions.  Is the cardinality of reflected jewels in this altered Indra's Net also the same as the set of integers?   Thank you.


C# looks great because it is a compiled language which seems to run quite well without too much CPU and does not consume too much memory. And StackOverflow and ServerFault are good examples of an MVC/.Net/C# stack that scales.  C# is also interesting because despite being compiled, it still has a lot of advanced features as a language only found on slower interpreted language.  My server being Linux only (Ubuntu 8.04 LTS), I am wondering if installing Mono in place of the .Net framework is a good idea for production use.  I currently do not have any existing applications using .Net but I am interested in using existing frameworks (like MS MVC).

Has anyone used Mono, the open source .NET implementation on a large or medium sized project? I'm wondering if it's ready for real world, production environments. Is it stable, fast, compatible, ... enough to use? Does it take a lot of effort to port projects to the Mono runtime, or is it really, really compatible enough to just take of and run already written code for Microsoft's runtime?


Dummit and Foote's exercise 14.3.11 asks to prove that $f(x) = x^{p^{n}}-x+1$ is irreducible over $\mathbb{F}_{p}$ iff $n=1$ or $n=p=2$. To prove the 'only if' part, the exercise suggest to prove that if $\alpha$ is a root of $f(x)$, then so is $\alpha + a$ for every $a \in \mathbb{F}_{p^{n}}$. This implies that $\mathbb{F}_{p}(\alpha)$ contains $\mathbb{F}_{p^{n}}$ and that $[\mathbb{F}_{p}(\alpha):\mathbb{F}_{p^{n}}] = p$.   I've proven everything except that $[\mathbb{F}_{p}(\alpha):\mathbb{F}_{p^{n}}] = p$. Can anyone give me some ideas for this? Thanks.

I have a question, I think it concerns with field theory.     Why the polynomial $$x^{p^n}-x+1$$ is irreducible in ${\mathbb{F}_p}$ only when $n=1$ or $n=p=2$?   Thanks in advance. It bothers me for several days.


I have a Unix domain socket (for example /var/run/mysqld/mysqld.sock). I know there is open connection(s) to this socket thanks to lsof -U or ss -xa but I cannot find which process is connected to it.   How can I know which process at the other end?

I want to determine which process has the other end of a UNIX socket.   Specifically, I'm asking about one that was created with socketpair(), though the problem is the same for any UNIX socket.  I have a program parent which creates a socketpair(AF_UNIX, SOCK_STREAM, 0, fds), and fork()s.  The parent process closes fds[1] and keeps fds[0] to communicate. The child does the opposite, close(fds[0]); s=fds[1].  Then the child exec()s another program, child1.  The two can communicate back and forth via this socketpair.  Now, let's say I know who parent is, but I want to figure out who child1 is.  How do I do this?   There are several tools at my disposal, but none can tell me which process is on the other end of the socket. I have tried:    lsof -c progname lsof -c parent -c child1 ls -l /proc/$(pidof server)/fd cat /proc/net/unix   Basically, I can see the two sockets, and everything about them, but cannot tell that they are connected. I am trying to determine which FD in the parent is communicating with which child process.


‘Hard’ /ˈskɛ.djuːl/vs ‘Soft’ /ˈʃɛ.djuːl/  Is one of the two variants    /ˈʃɛ.djuːl/ with ‘sh‑’ (so including [ˈʃɛ.djɫ], [ˈʃɛ.dʒɫ̩], [ˈʃɛ.dʒu.əɫ], [ˈʃɛ.dʒuːɫ]) /ˈskɛ.djuːl/ with ‘sk‑’ (so including [ˈskɛ.dʒu.əɫ], [ˈskɛ.djɫ̩], [ˈskɛ.dʒuɫ], [ˈskɛ.dʒuːɫ], [ˈskɛˌdʒuɫ], [ˈskɛ.dʒʊɫ], [ˈskɛ.dʒəɫ])   more widespread in the US vs UK, or is this just a matter of areas or even single individuals?

Is pronouncing the word "schedule" as "shed-ule" only an upper class thing in the UK? Which pronunciation, "sked-ule" "or "shed-ule" is more faithful to the original etymology of the word, i.e. which came first?


I'm a system administrator in our company. I have purchased some HP servers.  I asked my local vendor to install CentOS on them using original images.  When I went to server room today to install them, I saw some strange label     on every new server.  In addition, program glat-client was installed. After uploading this label, it started spamming the following message every hour:     This copy of GNU/Linux is not activated. You may be a victim of software counterfeiting. See ...... for details.   What does this label mean?

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


Let, $f(z)$ be an analytic function. Then the value of $$\int_{0}^{2\pi}f\bigl(e^{it}\bigr)\cos t dt= ?$$ (a) 0 (b) $2\pi f(0)$ (c)  $2\pi f'(0)$ (d)  $\pi f(0)$. $\mathcal{My}{Attemt}:$  First I put $e^{it}=z$. Then integration becomes $$\int_{|z|=1}f(z)\frac{z+z^{-1}}{2}\frac{dz}{iz}$$ $$=\frac{1}{2i}\int_{|z|=1}\frac{f(z)(z^{2}+1)}{z^{2}}dz$$ $$\frac{1}{2i}2\pi if'(0)=\pi f'(0)$$  But the answer does not match any option. Where my mistake??

$f$ be analytic function, could any one tell me how to find the value of $$\int_{0}^{2\pi} f(e^{it})\cos t \,\mathrm dt$$   I am not able to apply any complex analysis result here, could any one give me hint?


With regards to OOP, how would you describe an interface?  What I mean is, sub-classing can be described as "Has-A", and inheritance could be "Is-A". A member method could be "Can-Do".  Is there any way this could be extended (no pun intended) to describe what an interface does?

Could someone please demystify interfaces for me or point me to some good examples? I keep seeing interfaces popup here and there, but I haven't ever really been exposed to good explanations of interfaces or when to use them.  I am talking about interfaces in a context of interfaces vs. abstract classes.


I installed Ubuntu 13.10, then installed Dropbox from Ubuntu Software Center. Yet starting Dropbox seems to have no effect, and the Dropbox icon doesn't appear in the top-right indicator area like it normally does. Dropbox is apparently running, but the indicator/menu doesn't show up.

I have recently installed Ubuntu  on my machine and everything has been working fine, except I don't see the Dropbox indicator. I have installed and re-installed Dropbox multiple times and can confirm that it's running in the background (with ps -e | grep dropbox).  Does anyone know how to get it back?


when I open the Ubuntu software centre it intermediately closes   What can I do??

After plain installation of Ubuntu 16.04 LTS gnome-software doesn't work. It has opened once with GUI, but installation of Unity Tweak Tool didn't finish.  When starting again, GUI doesn't come up. When opening from terminal, a warning appears, but the application GUI doesn't open.  $ gnome-software (gnome-software:7052): Gs-WARNING: failed to open plugin /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so: /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so: cannot open shared object file: No such file or directory   Does anybody have same experience, and eventually, a solution?    According to the recommendation:  $ dpkg-query -S /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so gnome-software: /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so   Proposed reinstall of gnome-software did not help.    As workaround, use Synaptic Package manager and command line.


I just upgraded an installation of 14.10 x64 that was installed from scratch not long ago. I upgraded from the update manager because it suggested to do so.  It finished successfully and I rebooted.  After reboot I get stuck with a blank screen and I can't type anything. Also, I hear the tamtam sound looping every 5 seconds.  I saw other similar questions with answers but it does not work for me.  I can't ctrl-alt f1. It is not doing anything.  I burned a Ubuntu DVD x64 15.04 and can boot with it but I have no idea what to do next.  Please, if you want to help, I am not familiar with terminal commands.  Thank you.

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


I know that $\mathbb{F}_7=\mathbb{Z}_7$, and the all possible solutions of $x^6-1=0$ over $\mathbb{Z}_7$ are 1~6, so if we let the root of equation $x^6-3$ as $t $ then the solutions of $x^6-3=0$ is $t$~$6t$, which shows that all the solutions are not in $\mathbb{Z}_7$. However I can't say that $x^6-3$ is irreducible by this fact(since there could exist 2 or more degree polynomial divides $x^6-3$.) Is it irreducible over $\mathbb{Z_7}$? Why?

I want to find a splitting field of $x^{6}-3$ over $\mathbb{F}_{7}$. I learned that Finite field containing $\mathbb{F}_{7}$ is the form of $\mathbb{F}_{7^m}$ and it is normal extension. So I've tried to find smallest m containing a single root of $x^{6}-3$. If  $x^{6}-3$ is irreducible in $\mathbb{F}_{7}$, then $\mathbb{F}_{7^m}$ is splitting field of  $x^{6}-3$. But I don't know where I should start. Even, I cannot prove that $x^{6}-3$ is irreducible. For polynomial of degree less than 3, there is a method to determine whether it is irreducible or not. But this is not the case. And the try using Gauss' Lemma and Eisenstein is failed, because I cannot find ring $R$ of which field fraction is $\mathbb{F}_{7}$. Is it wrong approach for this kind of question?


I tried to prove the following statement using complete induction but I couldn't manage to solve it because I got a complex notation eventually. The statement is the following:  $$\sum_{k=1}^nk^3 = \left(\sum_{k=1}^n k\right)^2$$  I hope someone can help me out!

How can I prove that     $$1^3+ 2^3 + \cdots + n^3 = \left(\frac{n(n+1)}{2}\right)^2$$    for all $n \in \mathbb{N}$? I am looking for a proof using mathematical induction.  Thanks


Why does a UK-US-UK ticket not cost the same whether booked in the US or UK?   I have both US and UK credit cards, so it doesn't matter to me, but it seems absurd that the LGW-TPA-LGW ticket I just bought for less than $700 on the AA US site would have cost almost £800 on the AA UK site, a difference of almost $300.  Note I am NOT comparing a UK-US-UK trip to a US-UK-US trip. This is for the identical flights on the same days and times from LGW to TPA to LGW.

Based on the question , I got curious. Is there a guide or resource that describes how the price of a ticket is determined?  When you search you often see curious effects like cheaper tickets for a flight from A to B with a layover compared to a direct flight. This seems counter-intuitive from an outsider's perspective since you fly twice. Also one way tickets more expensive than 2 ways.  It can be a short set of rules. Something that helps someone to get started with finding good prices. I know these can be very complex and they probably change over time and over airline interests but there is probably a simplified set of rules that can be enunciated.


I tried to install wine from terminal i this is what i got:  liquid@liquid-desktop:~$ sudo apt-get install wine [sudo] password for liquid:  Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  wine : Depends: wine1.6 but it is not going to be installed E: Unable to correct problems, you have held broken packages.

Occasionally, when I'm installing stuff, I get an error like the following:  Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  package1 : Depends: package2 (>= 1.8) but 1.7.5-1ubuntu1 is to be installed E: Unable to correct problems, you have held broken packages.   How can I resolve this?


I've just installed Ubuntu 18.04. After a few minutes I noticed my bandwidth is remarkably low. I installed nethogs and realized /usr/lib/snapd/snapd is consuming my internet.   Questions:   How can I disable it? It really stops me from using the internet. Can I disable snap package system when installing Ubuntu?   Thanks a lot,

Is it possible to disable autorefresh in snap? This  says that Snaps are updated automatically in the background to the latest version, every day. Some snaps (e.g. vlc) are built daily, and it makes no sense to install them every day.


I tried to install Ubuntu by dual booting it with windows 10 technical preview. but when I started to install it I found that there was no option in Ubuntu 14.10 to dual boot it with windows 10. so plz can anyone help to dualboot ubnutu 14.10 with windows 10 technical preview.

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


In haskell ghci, "it" means last successful command, which can be used in next command arbitrarily as per need. Is some thing like this exist in python, not asking for history (reverse-i-search)

In many symbolic math systems, such as Matlab or Mathematica, you can use a variable like Ans or % to retrieve the last computed value. Is there a similar facility in the Python shell?


I was wondering if there was a tidy way to use reflection to instantiate a bunch of properties in a class, with a constraint that the property types to instantiate should only inherit from certain classes, and what if one of these classes has a generic type parameter.  For example.....  public class Control {     public string Name => "Test Name"; }  public abstract class BasePage<T> { }  public class HomePage : BasePage<HomePage> { }  public class LoginPage : BasePage<LoginPage> {     public Control Test { get; set; } = new Control(); }  public class LoginLinkPage : BasePage<LoginLinkPage> {     public Control Test { get; set; } = new Control(); }  public class UserPage : HomePage {     public Control Test { get; set; } = new Control(); }  public class Pages {     public UserPage UPage { get; set; }     public LoginPage LPage { get; set; }     public LoginLinkPage LLPage { get; set; } }    Is it possible to instantiate all the properties in Pages in a single method? And allow for more properties to be added and instantiated assuming they inherit from either BasePage<T> or HomePage?  This is what I have so far, but it only checks the subclass of the property type is homepage...  class Program {     public static void InitializeControls<T>(T page)     {         var pageType = typeof(T);          var properties = pageType.GetProperties().Where(p => p.PropertyType.IsSubclassOf(typeof(HomePage)));          foreach (var property in properties)         {             property.SetValue(page, Activator.CreateInstance(property.PropertyType));         }     }      static void Main(string[] args)     {         var pages = new Pages();          InitializeControls(pages);          Console.WriteLine(pages.UPage.Test.Name); // "Test Name"         Console.WriteLine(pages.LLPage.Test.Name); // NullReferenceException         Console.WriteLine(pages.LPage.Test.Name);  // NullReferenceException                 Console.ReadLine();     } }   I can't wrap my head around whether it's possible to also do a check for BasePage<T>, if T could be various different types.  I would be open to design changes that might solve this problem.   Thanks,

I have a generic class in my project with derived classes.  public class GenericClass<T> : GenericInterface<T> { }  public class Test : GenericClass<SomeType> { }   Is there any way to find out if a Type object is derived from GenericClass?  t.IsSubclassOf(typeof(GenericClass<>))   does not work.


public static workOrderRecordFormApex SAPgetPicklistValues(string recordTypeId, string objectName,string fieldApiName){         Map<String, String>  piclistValues=new Map<String, String>();         workOrderRecordFormApex objs = new workOrderRecordFormApex();         Httprequest req = new HttpRequest();         String SESSION_ID_START = 'SESSION_ID_START';         String SESSION_ID_END = 'SESSION_ID_END';         String pageContent = Page.SessionId.getContent().toString();         Integer startIndex = pageContent.indexOf(SESSION_ID_START) + SESSION_ID_START.length();         Integer endIndex = pageContent.indexOf(SESSION_ID_END);         String sessionId =pageContent.substring(startIndex, endIndex);           req.setEndpoint(             URL.getSalesforceBaseUrl().toExternalForm() +             '/services/data/v50.0/ui-api/object-info/' +             objectName +             '/picklist-values/' +             recordTypeId +             '/' +             fieldApiName         );         req.setMethod('GET');         req.setHeader('Content-Type', 'application/x-www-form-urlencoded');            req.setHeader('Authorization', 'Bearer ' + sessionId);         Http http = new Http();         httpresponse response=http.send(req);         picklistWrapper obj=new picklistWrapper();         obj=(picklistWrapper)JSON.deserialize(response.getBody(), picklistWrapper.class);         String JSONstr = response.getBody();         JSONParser parser = JSON.createParser(JSONstr);         Map<String, Object> defaultValueMap = (Map<String, Object>)JSON.deserializeUntyped(JSONstr);         for(piclistValues pickVal:obj.values){                          piclistValues.put(pickVal.value, pickVal.label);         }         objs.defaultSAPOrderType = defaultValueMap.get('defaultValue');         objs.sapOrderTypeValues = piclistValues;         system.debug('objs' + objs);         return objs;     }       private static List<PicklistEntryWrapper> wrapPicklistEntries(List<Schema.PicklistEntry> PLEs) {         return (List<PicklistEntryWrapper>)             JSON.deserialize(JSON.serialize(PLEs), List<PicklistEntryWrapper>.class);     }     public class picklistWrapper{         @AuraEnabled public piclistValues[] values;     }     public class piclistValues {         @AuraEnabled public String label;             @AuraEnabled public String value;     }     public class PicklistEntryWrapper{         public String active {get;set;}         public String defaultValue {get;set;}         public String label {get;set;}         public String value {get;set;}         public String validFor {get;set;}         public PicklistEntryWrapper(){                     }              }     @AuraEnabled     public object defaultSAPOrderType {get; set;}     @AuraEnabled     public Map<String, String> sapOrderTypeValues {get; set;}   In my apex class I want to get the picklist value of a field, where the valus is based on the recordtype.The code is working fine, but need to write test class for the same.Above is the apex class. And test class is @isTest private class QuoteComponentCtrl_Test {     @isTest      static void myTestmethod1() {         QuoteComponentCtrl.SAPgetPicklistValues(salesRecordTypeId, 'WorkOrder', 'SAP_Order_Type__c');     } }   In this Im getting error like "Methods defined as TestMethod do not support getContent call". Kindly help me to resolve this

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  How do I unit test code that includes a SOAP or REST-based callout, or indirectly calls code that makes a callout? I'm getting an error saying that callouts are not supported.


is it possible to adjust the automatic background scanning timeperiod? I want to decrease the time period.  Thanks.

Sometimes it takes too long for the network manager to update to see new wireless AP. Is it possible to change the time interval between checks?


A mysterious icon has just shown up in my system tray, a white exclamation mark within a red star:  Nothing happens when clicked or right clicked (including no orange bar underneath like other icons here). How would a user find out (on Ubuntu 18.04) what this is and what it's presumably trying (and failing) to warn about? This is just an example which I'm sure is easily solved, but in general are there any commands or tools that can display information about all current icons in the system tray?

A red explosion symbol with an exclamation mark appearred on the top bar and then this amber explosion with an arrow, which is shown in the screenshot.  I can't find out what they are for or signifying. Help welcome.


I have the following code which returns a NullPointerException:      private void misaveActionPerformed(java.awt.event.ActionEvent evt) {                                               if(fc.showSaveDialog(this) == JFileChooser.APPROVE_OPTION){     try {         File file = new File(fc.getSelectedFile().getAbsolutePath());         FileOutputStream fos = new FileOutputStream(file);         ObjectOutputStream oos = new ObjectOutputStream(fos);         oos.writeObject(m);         oos.close();     } catch (FileNotFoundException ex) {         jDialog7.setVisible(true);     } catch (IOException ex) {         Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);     }  } }   where variable m is declared as a field of my JFrame. Im a bit of a noob at java and I cant quite pinpoint the source of this exception, my best guess is that variable m is null for some reason. Calling getElementAt for m in the try catch clause returns correctly so m is not null?  This is the declaration of m as a field:  private CarteDeTelefon m = new CarteDeTelefon();   This code:  fc.getSelectedFile().getAbsolutePath()   returns the path correctly, so my question is, what are the possible causes for this exception here?  Stack trace:  Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at javax.swing.plaf.synth.SynthLookAndFeel.paintRegion(SynthLookAndFeel.java:371) at javax.swing.plaf.synth.SynthLookAndFeel.update(SynthLookAndFeel.java:335) at javax.swing.plaf.synth.SynthViewportUI.update(SynthViewportUI.java:167) at javax.swing.JComponent.paintComponent(JComponent.java:780) at javax.swing.JComponent.paint(JComponent.java:1056) at javax.swing.JViewport.paint(JViewport.java:728) at javax.swing.JComponent.paintChildren(JComponent.java:889) at javax.swing.JComponent.paint(JComponent.java:1065) at javax.swing.JComponent.paintChildren(JComponent.java:889) at javax.swing.JComponent.paint(JComponent.java:1065) at javax.swing.JComponent.paintToOffscreen(JComponent.java:5210) at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1579) at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1502) at javax.swing.RepaintManager.paint(RepaintManager.java:1272) at javax.swing.JComponent._paintImmediately(JComponent.java:5158) at javax.swing.JComponent.paintImmediately(JComponent.java:4969) at javax.swing.RepaintManager$4.run(RepaintManager.java:831) at javax.swing.RepaintManager$4.run(RepaintManager.java:814) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80) at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:814) at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:789) at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:738) at javax.swing.RepaintManager.access$1200(RepaintManager.java:64) at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1732) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756) at java.awt.EventQueue.access$500(EventQueue.java:97) at java.awt.EventQueue$3.run(EventQueue.java:709) at java.awt.EventQueue$3.run(EventQueue.java:703) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80) at java.awt.EventQueue.dispatchEvent(EventQueue.java:726) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

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've followed most instructions an clearing boot found on the interwebs, I'm a bit n00bish on linux inwards I use it mostly for web dev testing, but am pretty good at following command instructions ;)  Unfortunately my box seems to be stuck with the /boot full and I can't get my head around the correct steps to get clear it.  I believe I can't clean the boot because kernel 39 is pending install, but I can remove it from pending install because the boot is full?   This is the sequence of steps I attemped:  pedro@lamp01:~$ sudo apt-get autoremove Reading package lists... Done Building dependency tree Reading state information... Done You might want to run âapt-get -f installâ to correct these. The following packages have unmet dependencies.  linux-image-generic-lts-quantal : Depends: linux-image-3.5.0-39-generic but it is not installed E: Unmet dependencies. Try using -f.   pedro@lamp01:~$ sudo apt-get purge $(dpkg -l linux-{image,headers}-"[0-9]*" | awk '/ii/{print $2}' | grep -ve "$(uname -r | sed -r 's/-[a-z]+//')") Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies.  linux-headers-generic-lts-quantal : Depends: linux-headers-3.5.0-39-generic but it is not going to be installed  linux-image-generic-lts-quantal : Depends: linux-image-3.5.0-39-generic but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   pedro@lamp01:~$ sudo apt-get -f install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required:   linux-headers-3.5.0-32-generic linux-headers-3.5.0-27-generic   linux-headers-3.5.0-30-generic linux-headers-3.5.0-28-generic   linux-headers-3.5.0-30 linux-headers-3.5.0-31 linux-headers-3.5.0-26   linux-headers-3.5.0-32 linux-headers-3.5.0-27 linux-headers-3.5.0-28   linux-headers-3.5.0-31-generic linux-headers-3.5.0-26-generic Use 'apt-get autoremove' to remove them. The following extra packages will be installed:   linux-image-3.5.0-39-generic Suggested packages:   fdutils linux-lts-quantal-doc-3.5.0 linux-lts-quantal-source-3.5.0   linux-lts-quantal-tools The following NEW packages will be installed   linux-image-3.5.0-39-generic 0 upgraded, 1 newly installed, 0 to remove and 27 not upgraded. 3 not fully installed or removed. Need to get 0 B/40.7 MB of archives. After this operation, 157 MB of additional disk space will be used. Do you want to continue [Y/n]? Y (Reading database ... 269199 files and directories currently installed.) Unpacking linux-image-3.5.0-39-generic (from .../linux-image-3.5.0-39-generic_3.5.0-39.60~precise1_amd64.deb) ... Done. dpkg: error processing /var/cache/apt/archives/linux-image-3.5.0-39-generic_3.5.0-39.60~precise1_amd64.deb (--unpack):  failed in write on buffer copy for backend dpkg-deb during `./boot/vmlinuz-3.5.0-39-generic': No space left on device No apport report written because the error message indicates a disk full error                                                                               dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.5.0-39-generic /boot/vmlinuz-3.5.0-39-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.5.0-39-generic /boot/vmlinuz-3.5.0-39-generic Errors were encountered while processing:  /var/cache/apt/archives/linux-image-3.5.0-39-generic_3.5.0-39.60~precise1_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) pedro@lamp01:~$   It's a bit odd the autoremove appears to be forcing the install, the current kernel is 37:  pedro@lamp01:~$ uname -a Linux lamp01 3.5.0-37-generic #58~precise1-Ubuntu SMP Wed Jul 10 17:48:11 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux   Can anyone help?  Many thanks, P.

My first issue was when I tried to apt-get update or apt-get upgrade. On upgrade I get the following error:  You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies: linux-image-server : Depends: linux-image-3.2.0-27-generic but it is not installed E: Unmet dependencies. Try using -f.   I tried running apt-get install -f and this was the output(after saying yes on prompt)  (Reading database ... 186183 files and directories currently installed.) Unpacking linux-image-3.2.0-27-generic (from .../linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb) ... Done. dpkg: error processing /var/cache/apt/archives/linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb (--unpack):  failed in write on buffer copy for backend dpkg-deb during `./boot/System.map-3.2.0-27-generic': No space left on device  No apport report written because the error message indicates a disk full error                                                                           dpkg-deb:    error: subprocess paste was killed by signal (Broken pipe) Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.2.0-27-generic   /boot/vmlinuz-3.2.0-27-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.2.0-27-generic /boot/vmlinuz-3.2.0-27-generic Errors were encountered while processing: /var/cache/apt/archives/linux-image-3.2.0-27-generic_3.2.0-27.43_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   I tried running apt-get autoremove and it gives me the same error as apt-get upgrade.  When I run df, I get this for /boot:  /dev/sda1                    233191     230297         0 100% /boot   So, I read elsewhere that I should try to purge old kernels. I checked for what kernels I had with:  $ dpkg -l linux-image-\* | grep ^ii ii  linux-image-2.6.38-13-server  2.6.38-13.52  Linux kernel image for version 2.6.38 on x86_64 ii  linux-image-3.0.0-13-server   3.0.0-13.22   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-14-server   3.0.0-14.23   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-15-server   3.0.0-15.26   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-16-server   3.0.0-16.29   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.0.0-17-server   3.0.0-17.30   Linux kernel image for version 3.0.0  on x86_64 ii  linux-image-3.2.0-24-generic  3.2.0-24.39   Linux kernel image for version 3.2.0  on 64 bit x86 SMP ii  linux-image-3.2.0-25-generic  3.2.0-25.40   Linux kernel image for version 3.2.0  on 64 bit x86 SMP ii  linux-image-3.2.0-26-generic  3.2.0-26.41   Linux kernel image for version 3.2.0  on 64 bit x86 SMP   When I try to remove the oldest with this:  $ sudo apt-get purge linux-image-2.6.38-13-server Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: linux-image-server : Depends: linux-image-3.2.0-27-generic but it is not going to be     installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   How can I free up or extend boot without messing up my installation?


Find $\displaystyle \lim_{x\to 0}\left(x{{\left\lfloor{ \frac{1}{x}} \right\rfloor}}\right)$.   When $x\to0^{+}$ I have  $\left(x{\left\lfloor{ \frac{1}{x}} \right\rfloor}\right)\to 0\cdot \infty$.  When $\to 0^{-}$ I have  $\left(x{\left\lfloor{ \frac{1}{x}} \right\rfloor}\right)\to 0\cdot \infty$.  I have no idea,

Evaluate $\lim_{x \to 0} (x\lfloor\frac{1}{x}\rfloor)$  I'm trying to solve it by using the squeeze theorem but I'm stuck.  I'm looking for a function $g(x)$ such that $g(x) \leq x\lfloor\frac{1}{x}\rfloor \leq x(\frac{1}{x}) = 1$  Can anybody give me a hint?


More than 10 years ago, while traveling, I read one book in a series. I found it in a book exchange.  I think it was about humans in the far future being servants or slaves of an alien race.   The one characteristic of the this alien race is that they remember everything. They hear a story or view something and it is ingrained in their memory, there to stay for the rest of their life and can retrieve every detail at will. Since humans don't have that they are seen as inferior. I think also swords or other sharp weapons played a role.  I remember enjoying it tremendously and wanted to reread it and read the rest of the series, but unfortunately I never found it again.

The aliens in this book are an humanoid alien mercenary race, fighting for some other aliens, against humans?.   The Ker are the fighters, the sen are the wise ones, and the kaa the family/non-fighters.  Their clan gets almost wiped out because both their employers and humanity fear them, and the last survivors head towards their race' home planet, together with a human captive, who learns about their ways.  The other aliens are some blob-like aliens with little genetic variety.  Ring any bells?


What books an undergraduate needs to study to get a clear conception of rotational physics? I want books which are solely dedicated to rotational physics.

What are some good books for learning the concepts of Kinematics, Newton laws, 2D Motion of Object etc.?


As SE grows, lots of communities grow using it. Why not? So far, so good. As SE grows, lots of people find answers for their problems just being forwarded here by different search engines. Halleluja. As they get more and more solutions here, they want to reciprocate and give answers. Or they want to get help here by asking questions. And then they face moderation, close requests, migrations and alike. Let me introduce you , a user I kept an eye on for a week. He asked a question, thanked for all replies, stayed humble and helpful in his replies. He still could not grasp the differences between stackoverflow.com, programming.stackexchange.com and superuser.com. He could not keep up with our rules and did rage quit. Finally my question after this long prologue: How could we be more welcoming? How could we ease the learning curve? Is there really such a big gap between discussing issues through code (stackoverflow) or concepts and design (programming)? Is it a bigger difference than say the [c#] and the [java] tags? Am I the minority who has to jump between communities back and forth to ask and answer questions? Probably there is no clear answer to this, but I hope I made a difference just by you - my reader - reading this question.

There is a distinct decline in the level of civility on all the sites here.  Some of this is due to new users coming in and posting spam and other nonsense, but the off-topic and downvote buttons are doing a pretty good job of keeping this under control. Unfortunately, a lot of this is coming from more experienced users, and the site's built-in moderation system does not (and probably cannot) handle this very well.  Folks are rushing to pound new users down with "this belongs on meta!", "this is off topic", "this is a duplicate!" and "read the Help!". (Which is correct, but should be done nicer) All this, of course, is accompanied by a flurry of downvotes.  This is not very welcoming to new users who don't know about meta, the Help, or what counts as off-topic. Now I am not proposing that we just allow off-topic, meta, or duplicate questions.  However, I think we could be gentler in the way we express these sorts of things.  Explain what meta and the FAQ are and provide useful links.  Just using please and thank-you when asking folks to read the FAQ or post something on meta would be an improvement.  I also think we could rein in the downvoting a bit.  Not that we shouldn't vote stuff down, but unless a new user's post is clearly spam, voting it down to -1 or -2 should be sufficient to send a message without piling on. I like Stack Exchange and I want it to become a resource for everyone, not just an elitist site for high-rep users on the sites.


In , The whole serie is centered around "". Through the show there are questions about what they are and what they can do.  At first,  (The Emissary) think of them as "The wormhole aliens". The more we go through the show the more we see that Sisko slowly change his vision about these Prophets.  I know it starts a little sooner then this but, in  (season 5, episod 10):      Sisko uncover an ancient Bajoran artefact wich seemed to have "led"  him to it, latter in the episod, Sisko starts to have vision and he  literally embraces his role as The Emissary   In  (season 6, episod 21) :       and  are being "possessed" by the   (Sisko) and The Prophet (Kira).   In  (Season 6, episode 26):      Dukat comes across an ancient Bajoran artifact, he breaks it while  chanting a sort of incantation and then the spirit of a  Pah-Wraith enters him.   In  (season 7, episode 1):      Sisko learns that a Prophet came to earth in the exact purpose of  created him as the future Emissary.   There is a number of other examples but I think these 4 will suffice. After reading this (and knowing that these creatures live outside linear time):  Is there any final statement as exactly what these creatures are and (if so) what kind of technology are they using and again just how far their powers extend ?

So, within the DS9 universe, there were the Prophets that lived within the wormhole.  What sort of beings were they?  What were their powers?


How can I retrieve the message-only from a fatal error message in php store it as a variable.  I'm running a script which I believe has some custom error reporting on it when it runs. When the function fails, I get this:  <b>Fatal error</b>:  Uncaught exception 'functionName' with message 'the was an error' in 'filepath.php line 10'   I have error reporting turned on like this:  <?php error_reporting( E_ALL ); ini_set( "display_errors", 1 ); ?>   However, I'd like to store the error message as variable that I can use in a more user-friendly way.  So far I've tried this:  $var = error_get_last(['message']); echo $var;   But it doesn't display anything.  Any help is much appreciated.

I can use set_error_handler() to catch most PHP errors, but it doesn't work for fatal (E_ERROR) errors, such as calling a function that doesn't exist. Is there another way to catch these errors?  I am trying to call mail() for all errors and am running PHP 5.2.3.


I am looking for a young adult book, probably written in the late 60's to mid 70's, it was a dystopian future where people seemed to be set in for specific roles.  The main character, a boy, wanted to be a farmer or gardener, while society was dictating he should be something else.  There was something about a food shortage, or control of food, such that him being a farmer or gardener was somehow forbidden.  I can't really recall more than that.  Mostly the story was about how the boy learned secretly how to raise plants and with another (perhaps a girl) escaped the place he lived.  I know not much to go on, but it's one I recall liking when I was young but can't remember more of the story.

I'm hoping someone can identify this young-adult/children's sci-fi book. I read it in 1996-1997, but I remember thinking it was written in the 1980s.   The main character was a boy (maybe in his early teens) and over the course of the book he gained a female companion of the same age. I think the boy and his father had a vegetable garden growing in their basement, but it was illegal for them to grow their own food so they hid the trapdoor to the basement under their refrigerator. The boy's father was an important scientist (or something of that nature) and he goes missing (taken by the evil government?) and the boy has to find him.   There is a scene where the boy is at school and is sent to the school counselor or doctor to be given an anti-depressant or tranquilizer pill, the counselor (a male) is sympathetic to the boy and tries to help him and the girl to find the boy's father (and possibly the girl's parents too?). There was also a scene where the boy and girl go to an abandoned building/warehouse to meet someone who can give them information on their parents (maybe they meet each other for the first time at the building?). It seems like there was also a mention of golf clubs in relation to the boy's father and a mention of Crackerjack rings in relation to the girl, but I know a Crackerjack ring played a part in another book I read around the same time so I could be confused:).   Sorry this is so long, I only read part of the book and would like to find out how it ends.


To solve Partial Differential Equations, I installed FEniCS on a virtual environment. To use FEniCS, I have to use the Dolfin Library and I wish to know, how to install this library. I tried the following options but didn't get through: 1. pip install dolfin  ERROR: Could not find a version that satisfies the requirement dolfin (from versions: none) ERROR: No matching distribution found for dolfin   2. sudo apt-get install dolfin  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package dolfin  I am new to using Ubuntu and installing packages, it would be great if someone could help me out getting rid of this (in a Jupyter Notebook): import dolfin  ModuleNotFoundError                       Traceback (most recent call last) <ipython-input-17-c13f418a68dc> in <module> ----> 1 import dolfin  ModuleNotFoundError: No module named 'dolfin'

I am new to Ubuntu and I've been trying to run the first fenics tutorial, but I keep getting an error that says: No such file or directory. I downloaded this first program and it is in the downloads folder of my computer, but I can't seem to be able to access it on Ubuntu. Is there anyway that I could get this file from Ubuntu?


I hate to spam and reopen old issues but this is urgent!!  I am experiencing an identical problem to the one in:   My internal drive can format to everything except APFS, I have tried troubleshooting via linux, and simple disk utility. Fsck and first aid both report no problems and this is driving me insane!! help desperately needed!

I’ve recently ran a semi-routine clean install on my 2018 MacBook Pro. This involves the following steps (in the given order):   Creating a USB installer with the latest macOS Mojave 10.14.2. Booting into the USB (Pressing Option key on boot). Using the Disk Utility, erasing the Disk and formatting it as APFS with a GPT Partition scheme. Using the Terminal, unmounting the disk diskutil unmountDisk disk0, where disk0 is the internal NVME drive. Using the Terminal, running gpt destroy disk0 where disk0. Using the Terminal, running diskutil zeroDisk disk0. Once that process is complete, I use the Disk Utility application to reformat as APFS, and install macOS.   Nothing super crazy, maybe a little redundant in steps, maybe a little overkill, maybe a little unnecessary.  Recently, however, on the final step where I format it as a APFS drive, it fails in creating the APFS container and says Internal State Error. It appears to first format as Mac OS Extended (Journaled) then create an APFS container, then add a APFS Volume. It fails when adding a Volume with An internal error occurred.  I have tried many things, including:   Securely erasing the drive diskutil secureErase 0 disk0. Simply zeroing the disk again diskutil zeroDisk disk0 (I’m not sure what the actual difference between these two are). Reformatting the drive as other things, such as ExFAT / FAT / MacOS Journaled, then trying to format as APFS. Reformatting the drive through the command line instead: diskutil eraseDisk JHFS+ NAME disk0 → diskutil apfs createContainer /dev/disk0s2 → diskutil apfs addVolume disk0s2 APFS NAME (It fails here with Error starting APFS Container creation: The given disk is not an APFS Container Reference (-69630), even though I just made a container there. Also, trying to add a volume to where it actually made the container (i don't know what it does this) diskutil apfs addVolume disk24 APFS NAME also fails with Error: -69624: Unable to add a new APFS Volume to an APFS Container Reformatting the drive using this: diskutil eraseDisk APFS NAME disk0 Restarting and trying these again. Using a different installer than the USB (The one from Command + R, Command + Shift + R, and whatever the other combo is), and trying these again.   All end up at the same thing - the final step fails. I would expect especially after a secure wipe that the drive would be removed from whatever state it was put in, or that if it was a bug with the 10.14.2 installer, that it still wouldn’t happen again in the High Sierra installer. In Disk Utility, I’m left with the following structure:  - APPLE SSD AP(...) // “Container disk24” takes up all space      - Container disk24 // or some other number. “Used” is 207.2MB and “Free” is 1TB.   Please note even though I can format as JHFS+, it won’t let me install the OS to such a formatted volume. The installer tells me this computer forces me to only install on APFS formatted volumes.  Any direction is greatly appreciated. I have never had such a silly problem before. Also, note that I have no Time Machine backup.


Background  An edit on one of my posts was suggested. I reviewed and rejected it. I looked up the user and saw similar minor (approved) edits I @commented the user to ask him/her to do more substantial edits  Question But I am not sure if a @comment will reach the user. What if there are multiple users with the same displayname? How does the system know whom sending the comment? So the question is: What participation in a post leads to a @notification?  The user must be the poster or a commentor a previous editors? a (rejected) reviewer? a closer? a deleter? ... doesn't matter? All with the same name get the notification?

How do the comment replies (aka "pinging users") work?  Who can I send an @reply to? How do I respond to a specific user when entering my comment? Will they be notified? What do people mean when they talk about "pinging" another user?  Related:


I have a university table that consists of prospective student information.  I need to populate the email address column and the format is first_name.last_name@su.edu.    I have been trying to used the CONCAT method but every time I execute the code I run into an error stating that 'invalid number of arguements'.  SELECT CONCAT(first_name, '.', last_name, '@su.edu') AS prospect_email FROM prospect;   The expected output should be first_name.last_name@su.edu.

What is the string concatenation operator in Oracle SQL?    Are there any "interesting" features I should be careful of?    (This seems obvious, but I couldn't find a previous question asking it).


I'm trying to choose my own items instead of just following a guide, but keep struggling with understanding when to use Blood Thirster or Blade of the Ruined King (or vice versa) on Marksmen champions. Since they are ranged, at least Ravenous Hydra is not an option (though, it would be great if answers included how to pick between all 3 for melee ADCs).  I tend to go for BotRK on champs with on-hit stacking effects like Varus, Twitch etc. and lean towards BT for those with good AS steroid like Jinx. For Lucian I was going BotRK as it synergizes with his ult, then I see a guide and its recommending BT (then I realized, its probably to get higher damage for his passive double AAs?)  I am not looking for a list of recommendations on what to build for each champion - rather, hoping to get explanations on what kind of thought process to use when itemizing. e.g. I've heard Vayne has different builds where you choose one or the other depending on skill order.

Effects:  +25 attack damage +15% life steal +40% attack speed Passive  Unique: Your attacks deal 5% of the target's current health in physical damage (60 max vs minions and monsters). Active   Unique: Drains target champion, dealing 15% of the champion's maximum Health in physical damage and healing you by the same amount. Additionally you steal 30% of their movement speed for 4 seconds - 60 second cooldown. (500 range)  Cost: 3200g VS.   Effects:  +70 attack damage +12% life steal Passive: Gain +1 attack damage and +0.2% life steal per kill (maximum +30 attack damage and +6% life steal). Half of the bonuses are lost upon death.  Cost: 3200g What is better for what situations, and when should you build BT instead of BotRK and Vice Versa. Which provides more lifesteal, the only variable being the stats of the weapon? I find myself constantly questioning my decision on which weapon to get and would really love some in depth answers. Would be great if any examples given were given from the ADC side of the house.


some quick back ground:   I recently sold my shares in a company I started to accept a great position with a large company.   It was a cross country move for me and my family. Once my property sells back where I left I will be in a position to pay off almost all of my debt right away, and be able to pay the rest within 1.5 years with the new pay scale.   That being said, here is my hang up:  I have about the same amount of debt in a vehicle loan @ 0% as I do in a student loan @ about 6%. Cash flow is a bit of a concern at least initially while we settle into our new home.   The payment on the vehicle is $645/month and the student loans are $225/mo. The other thing to consider is the vehicle is far beyond what I need now and I have about $8500 in equity in it (but i kind of love the vehicle lol)   I am looking for some opinions on which loan i should satisfy now and which one I should wait to pay until 2017. or if I should dump the vehicle and regroup?

Within the past year my wife and I have paid off approximately $40,000 in debt - from her car loan, my two student loans, and other misc debt (new refrigerator, hardwood floor install). I had a car lease expire so I went to purchase a new one and got a 5 year, 0% interest loan, with approximately $20,000 left.  My wife has her doctorate in healthcare and, unfortunately, the student loans racked up and has about $90,000 over the next 26 years.  Based on my estimates we're slated to pay off her student loans within 7 years. We both work full time and I do freelance consulting work on the side. I currently have enough (after taxes) saved from my freelance work to pay off my car or put it towards her student loan.  Which way is better? Should I pay off my car loan and put the $400 per month towards her student loans? Or should I keep paying the car loan and put all our extra money towards her student loans?


In the year 2000, someone probed the 3 dimensional quantum dots using a new condition which is important in semi conductor physics. But they basically solved the Schrodinger equation for ground state and discussed the consequences.  I have extended their work for general case , i.e, one can calculate "higher" state energy using those calculations. Also, I have pictured how the wave function looks like at higher states.  But I think that I have done just Math & some computations.     My query is : Is this result publishable owing to the fact that I am a Junior year student and I did this work without any adviser.

I am a bachelor student majoring on computer engineering and working on robotics. Last year as a part of my research, I worked together with a student and one teacher as a supervisor, so we published our article for conference together. But later we finished our research and all of us left the team. Now I am working on other research problem by myself and got some results and want to publish it. But this time I am alone, I have no supervisor on that research problem or any student partner. So I'd like to ask can I submit a paper for conference/journal by myself? P.S. My current research project has no relationship with old one.


I am modeling some furniture and got a problem with flat shading of a surface. I first draw a rectangle, where the texture and shade were OK. After cutting two holes though, the shading got weird. Could you help me with this issue?

I tried to manipulate a cube with the Boolean modifier. I tried to cut out an edge of the cube with a cylinder. Also, the shading result looks awful in FLAT SHADING mode, so I turned on SMOOTH SHADING.   Has anyone an idea how to achieve a better result. (I also cut out a Sphere first, this made the result less awful).   I used Blender Internal and rendered with smooth shading for smoothness.  Using flat shading looks okay, except the "round" cutouts :/  Face normals are okay.  First image is smooth shading.    EDIT: User Pisurquatre suggested the EdgeSplit modifier, works perfect to me (Maybe a little tweaking here and there):


I am building a GLM Model that predicts whether there will be a claim in a certain policy or not. So target variable is either 0 or 1, so my choice of GLM was Binomial, and link function was Logit. In the data I also have an Exposure column, which has values greater than 0 but less than or equal to 1. 1 means that the policy has experience of 12 months, and 0.5 would mean that the policy has experience of 6 months. How do i include this information in my GLM? Should I just use offset on exposure, or use log of exposure? Please suggest.

I am replicating an analysis that models tree mortality data. Data are structured such that forest sites are revisted at some random interval, which is recorded. It is then determined if a tree lived or died over that random interval, generating 0 1 mortality data (if a tree dies, it gets a 1 in the dependent variable). The interval between initial and final observation varies continuously, from 5-15 years. This is relevant, as the more time that passes, the more likely a tree will die.   Here are some pseudo data for R:  mort <- c(0,1,0,0,0,0,0,1,1,1,1,0,1,0,0,0,0,0,0,0,1,0) interval <- runif(length(mort), 5, 15) pollution <- rnorm(length(mort), 25,5) data<- data.frame(mort, interval, pollution)   I am trying to replicate an analysis which uses a logistic regression model for binary mortality data using the the logit transformation. Authors then model how pollution affects tree mortality rates. In the manuscript the authors write, "because recensus is not annual, we relate annual mortality probability, pi, of tree i to the observed binomial data on whether that tree lived or died Mi via a Bernoulli likelihood,    where ti is the time interval between successive censuses."  My question: How would I implement this using the glm function, or something analagous, in R? Note: I understand modeling this as a hazard function would also be appropriate, but it is not what I am interested in.


I would like to list the keywords for my thesis on the format:   First Keyword, 2. Second Keyword, 3. Third Keyword, ...   But not had to type the numeration manually, so the command would be like:  \mykeywodslist{First Keyword,  Second Keyword, Third Keyword}   Then calling the command:  \printmykeywordlist   Would print them like:  1. First Keyword, 2. Second Keyword, 3. Third Keyword

I have the latest version of the enumitem package and I'm trying to use different labels for enumerate lists which are set as normal lists and enumerate lists which are set inline. However, it doesn't seem to work (one customization overwrites the other), and I've already asked a question about this where it turned out to be due to a bug.  However, I still can't get it to work. I have the following MWE:  \documentclass{article} \usepackage[inline]{enumitem}  \setlist[enumerate,1]{%   label=\arabic*., } \setlist*[enumerate,1]{%   label=(\roman*), }  \begin{document}  \begin{enumerate}   \item item 1   \item item 2   \item item 3 \end{enumerate}  \begin{enumerate*}   \item item 1   \item item 2   \item item 3 \end{enumerate*}  \end{document}   and what I get is:    Either I don't understand how to use the \setlist to get this to work, or the bug still remains. I can't figure out which.


My memory stick was left in some flood water. I've tried drying it out using rice.  Will this USB drive memory stick damage my computer if I try to use it?

So a few months ago I accidentally spilled a little water on a few of my usb flash drives. I really want to test and see if they work, but before I do, I just want to make sure that there's no risk of damaging my computer. I'm pretty sure it's fine, but I just got a new laptop and would hate to ruin it over something stupid.


I saw several examples of user defined macros using \newcommand (without the *), and examples with \newcommand*.  Trying both in my test documents doesn't show any difference.  So why the asterisk?  What are its functions?  Should I care about it or not?  Here's a simple MWE to play with, in case it is usefeull here:  \documentclass[11pt,letterpaper,twoside]{book} \usepackage{lmodern} \usepackage{amsmath} \usepackage{mathtools}  \newcommand*{\bigs}[1]{\vcenter{\hbox{\scalebox{1.25}{#1}}}} % Why the *?  \begin{document}  Blabla bla bla blabla :     \begin{equation}         c \, \bigs( 1 + (x - y^2)(a + b) \bigs) = \tfrac{3}{4}.     \end{equation}  \end{document}

I just spotted someone use \newcommand* in an answer and realised that I'd never quite sorted out in my head what the star (asterisk) was there for.  (This one is practically impossible to search for on the internet so this is a good place to record the answer!)


An exercise from Hungerford's Algebra.     Let $\mathbb Q$ be the field of rational numbers and $R$ any ring. If $f,g:\mathbb Q\rightarrow R$ are homomorphims of rings such that $f=g$ on $\mathbb Z$, then $f=g$ on $\mathbb Q$.   The hint given by author asks me to show $f(1/n)g(n)=g(1)$, which is easy to check, and hence $f(1/n)=g(1/n)$, where I get stuck because I think $nf(1/n)=ng(1/n)$  may not imply $f(1/n)=g(1/n)$ since $R$ can have character $\neq0$.  Can anyone help me to figure it out?

I have two ring homomorphisms $f,g\colon \mathbb{Q}\to X$. I know that $f=g$ on the integers. How can I show that $f$ and $g$ agree on the rationals?   My attempt:  let $x,y \in \mathbb{Z}$, $y\neq 0$.  $$\begin{align*} f(x/y)&=f(x)f(1/y) &&\text{because }f\text{ is a ring homomorphism}\\  &=g(x)f(1/y) &&\text{because }f\text{ and }g\text{ agree on the integers} \end{align*}$$  I do not know how to rewrite $f(1/y)$ so that I can replace it with $g(1/y)$. Any hints will be much appreciated. Thanks.


I'm currently considering switching totally to Ubuntu. The only thing holding me back is whether or not my photos, music, word processor, and other document files will open in Ubuntu. For example, I have done important files I created in open office on my windows computer. Will they open on open office in Ubuntu? Will my images and photos be displayed the same as they did in windows?  I apologize if this question has been answered previously. I searched, but was unable to located any discussion that addressed my specific question. I am a complete novice when it comes to Linux, but I look to learning more.  Thanks.

Can I open Microsoft Word and Excel files with Ubuntu?


I want to install php7.4-soap on my Ubuntu 20.04 machine, so I ran sudo apt-get install php7.4-soap But I get following error: Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  php7.4-soap : Depends: php7.4-common (= 7.4.3-4ubuntu1) but 7.4.5-1+ubuntu19.10.1+deb.sury.org+1 is to be installed E: Unable to correct problems, you have held broken packages.  How can I deal with this error?

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


What is the difference of  LinkedList<String> l1 = new LinkedList<String>(); List<String> l2 = new LinkedList<String>();   Why does l2 type don't have method addFirst while l1 type have method addFirst? even though they are both  hold a LinkedList object? Contrary to what I read from Gosling's "The Java Programming language" which states that the object will be what you made it to be, in this case I made it a LinkedList with new LinkedList() even though it is of type List  How should I properly declare then?  Collection<String> c = new LinkedList<String>(); List<String> c = new LinkedList<String>(); LinkedList<String> c = new LinkedList<String>();

I have seen this mentioned a few times and I am not clear on what it means. When and why would you do this?   I know what interfaces do, but the fact I am not clear on this makes me think I am missing out on using them correctly.   Is it just so if you were to do:  IInterface classRef = new ObjectWhatever()   You could use any class that implements IInterface? When would you need to do that? The only thing I can think of is if you have a method and you are unsure of what object will be passed except for it implementing IInterface. I cannot think how often you would need to do that.   Also, how could you write a method that takes in an object that implements an interface? Is that possible?


There's no fences at the boundary of Forbidden Forest. Students can (and, do) get inside, but they are atleast intelligent animals to be careful and avoid entering the forest. But, it's not true for deadly animals wandering in the forest (). What prevents them from coming into Hogwarts campus and attack students? Is there an enchantment in place for the protection?

We know there is a wide range of dangerous creatures in the Forbidden Forest, from small to large.  The Forbidden Forest is also not far from Hogwarts and we've seen proof, in The Chamber of Secrets, that the spiders from the forest were in Hogwarts and were fleeing Hogwarts for the Forest after the opening of the Chamber of Secrets.  With all the bad nasty creepy crawly things in the Forbidden Forest, and it being so close to a school, what prevents these darklings from leaving the Forest and creeping into (or invading) Hogwarts?  There's no mention of anything magical that Harry and friends feel when they enter or exit the forest.  And how are the spiders able to get past this protection?


Given a phrase in the middle of which TeX will place a return carriage, if we place this phrase within a \colorbox, TeX no longer places the return carriage and the phrase protrudes in the margin. Is there a way around this or am I missing something trivial?

LaTeX has soul. ConTeXt, of course, , where you can put sweet hightligher under your text for free!    In the pictured example, you can see highlights that not only highlight, but that do it with cool edges that look so good, you can smell fumes! The fearless author says he'll show how that was done in another post; this one shows only how to lay down a straight, yellow box. But, it is possible to do word-wrapped highlighting with cool-shapped boxes within ConTeXt, presumably.  The trouble for me is that getting into the ConTeXt world is steep climb right now, given the state of documentation and the flux of changes, so I need to continue with LaTeX. But the real problem is that now I can't live without the Organic-Looking Highlights of Awesomeness in that picture!  As I said, Non-Organic-Looking Highlights of the Ordinary are easy with the soul package:  \hl{Some awesome text that word wraps fine.}   It just taunts me on the page with its straight lines. So, if I sacrifice word wrapping, I can use PGF/TiKz and create the following macro:  \newcommand\hl[1]{%     \tikz[baseline,%       decoration={random steps,amplitude=1pt,segment length=15pt},%       outer sep=-15pt, inner sep = 0pt%     ]%    \node[decorate,rectangle,fill=navcolor,anchor=text]{#1\xspace};% }%   Which creates something like this:    Now, my color is too dark and my randomness needs adjusting, but you see that a similar effect could be achieved.  My trouble is that I don't understand TeX enough to dig into the Soul package and add the TiKz/PGF goodness that it so sorely needs. So, I leave it to you guys. Anyone want to tackle this?   Or is it yet another piece of fruit, just a touch out of reach, that shall have to wait until ConTeXt settles down?


How to clean my desktop?  I tried to install pspp for my statistic exam. After rebooting, my desktop has many files like that. How to fix that? I have used Tweaks but cannot do it.

As of now, my desktop has begun showing the contents of my home folder (~) instead of the contents of ~/desktop. I must have changed something, but I have no idea what, or what I was doing exactly when it happened.  How do I re-point gnome to the right folder?  I'm running Ubuntu 11.04.


I would like to refer to another reference in a bibliography item. It should look like the following in the bibliography:  [30] Author (Year), Cited in [12].   How do I achieve this?

In BibTeX, I need to cite another entry as a note/comment of a first one, something like:  @article{Paper1, author = {Author A.}, journal = {The Journal of XX}, number = {1}, pages = {4252}, year = {2000}, note = {see updated results in \cite{Paper2}    } }  @article{Paper2, author = {Author B.}, journal = {The Journal of YY}, number = {2}, pages = {1}, year = {2001} }   Could you give a suggestion in doing this?  I think my need is not really fitting to what proposed here:


I am standing on the surface of some planet. Gravity is described via General Relativity with some static metric (e.g. the Schwarzschild metric, so static means no time dependence, but the metric may vary from place to place). I send a blue photon up to my friend, who is x meters above me in some tower (we are both at rest relative to each other). He measures the photon and finds out it is red. We both conclude that a gravitational redshift occured. However, where did the energy go? In GR there is no gravitational energy so the photon did not trade "light energy" with potential energy.  I found several threads about this, but often they viewed this topic from a cosmological point of view where the metric does depend on time and thus Noether does not work to argue for a conservation of energy. Arguments without cosmology used the explanation via potential energy (which is not a thing in GR, as far as I know). So, since the metric is still time independent the energy should be conserved according to Noether.  What is going on?  Edit: On the Einstein thought-experiment in the linked question:  This does not explain why energy is not conserved from a mathematical or physical point of view. This could also be viewed as a reason why you can not turn photons into matter (and vice versa) without losing energy.

In the gravitational redshift, the frequency of photons radiated from some source is reduced. As the energy of a photon is given by $\hbar\omega$, if the frequency is reduced where is the lost energy?


This is bank account class:  namespace BankAccount {     public abstract class BankAccount     {         protected static int numberOfAccounts = 100001;         private double balance;         private string owner;         private string accountNumber;          public BankAccount()         {             balance = 0;             accountNumber = numberOfAccounts + "";             numberOfAccounts++;         }          public BankAccount(string name, double amount)         {             owner = name;             balance = amount;             accountNumber = numberOfAccounts + "";             numberOfAccounts++;         }          public BankAccount(BankAccount oldAccount, double amount)         {             owner = oldAccount.owner;             balance = amount;             accountNumber = oldAccount.accountNumber;         } } }   This is Checking account class:  namespace BankAccount {     class CheckingAccount : BankAccount     {         int fee = 15;         public CheckingAccount(string name, double amount)         {            base.BankAccount(name, amount);         }         public new bool Withdraw(double amount)         {             double totalAmount = amount + fee;             return base.Withdraw(totalAmount);         }     } }   For, base.BankAccount(name, amount); I am getting error,      'BankAccount' does not contain a definition for 'BankAccount.'    Bank account is the base class and checking account inherits the base class.  and when I remove the base keyword it says:      Non Invokable member cannot be used as a method.   In the main, I created an object, I want to accept a value in Main - a string and a double and then send it to CheckingAccount class and CheckingAccount constructor should run and then send the values to BankAccount constructor and do the calculations.  How can I fix the error      'BankAccount' does not contain a definition for 'BankAccount'   . ? Thanks,

If I inherit from a base class and want to pass something from the constructor of the inherited class to the constructor of the base class, how do I do that?  For example, if I inherit from the Exception class I want to do something like this:  class MyExceptionClass : Exception {      public MyExceptionClass(string message, string extraInfo)      {          //This is where it's all falling apart          base(message);      } }   Basically what I want is to be able to pass the string message to the base Exception class.


P | Q | P->Q  T | T | T (That makes sense)  T | F | F (That makes sense)  F | T | T (Why the anwser is T?)  F | F | T (Why the anwser is T?)

Provided we have this truth table where "$p\implies q$" means "if $p$ then $q$":  $$\begin{array}{|c|c|c|} \hline p&q&p\implies q\\ \hline T&T&T\\ T&F&F\\ F&T&T\\ F&F&T\\\hline \end{array}$$  My understanding is that "$p\implies q$" means "when there is $p$, there is q". The second row in the truth table where $p$ is true and $q$ is false would then contradict "$p\implies q$" because there is no $q$ when $p$ is present.  Why then, does the third row of the truth table not contradict "$p\implies q$"? If $q$ is true when $p$ is false, then $p$ is not a condition of $q$.  I have not taken any logic class so please explain it in layman's terms.       Administrative note. You may experience being directed here even though your question was actually about line 4 of the truth table instead. In that case, see the companion question  And even if your original worry was about line 3, it might be useful to skim the other question anyway; many of the answers to either question attempt to explain both lines.


I can see that , where you can’t hear the vowel in the ‑man syllable.  But sometimes it is pronounced /pəʊs(t)mæn/  — with a noticeable /æ/ vowel like in the word man — as heard in the  from more than fifty years ago.   Why is postman sometimes pronounced differently in different times, places, or situations?   What is the real pronunciation of the word?

It seems that in the words Englishman, Frenchman, and Scotsman, the ‑man part is pronounced /mən/ (just like in Roman).  Whereas in snowman, the ‑man part is pronounced /mæn/ (just like in no man).  Why is it that when ‑man is appended to snow‑ to make snowman, the pronunciation of the man part doesn’t change?    Wouldn’t it logically follow for it to be pronounced /ˈsnowmən/ not /ˈsnowˌmæn/?


How can I get a reference to the class in a static method? I have following code: class A:     def __init__(self, *args):         ...     @staticmethod     def load_from_file(file):         args = load_args_from_file(file)         return A(*args) class B(A):     ...  b = B.load_from_file("file.txt")  But I want to B.load_from_file return object of type B, not A. I know if load_from_file wouldn't be a static method I could do def load_from_file(self, file):         args = load_args_from_file(file)         return type(self)__init__(*args)

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


I have a bunch of point lights and directional lights. Instead of checking the light type in the fragment shader and then branch for either point light calculation or directional light calculation, is it more efficient to use two separate programs, one for point lights and one for directional lights?  (Using deferred shading in OpenGL 3.3)

I am doing some 3D demos using OpenGL and I noticed that GLSL is somewhat "limited" (or is it just me?). Anyway I have many different types of materials. Some materials have ambient and diffuse color, some materials have ambient occlusion map, some have specular map and bump map etc.   Is it better to support everything in one vertex/fragment shader pair or is it better to create many vertex/fragment shaders and select them based on currently selected material? What is the usual shader strategy in OpenGL or D3D?


I want to turn an old ubuntu laptop into a minecraft server supposed to run within my home. Minecraft is in place, I can fire it up and see the gui and run it in a terminal as well.  Laptop IP is 192.168.0.22 and according to server.properties the port is 25565 but when I enter these information into minecraft pe on my phone I am unable to connect to the server.  My goal is just to let this run within our home no public access is needed. But what am I missing?

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


I was learning Threads , and I'm stuck up on this program, why is this resulting in NPE? why do the threads not run?  here's my code:  class Chicks {         synchronized void yack(long id) {         for(int x = 1; x < 3; x++) {             System.out.print(id + " ");             Thread.yield();         }     } } class ChicksYack implements Runnable {     Chicks c;     public static void main(String[] args) {         new ChicksYack().go();     }     void go() {         c = new Chicks();         new Thread(new ChicksYack()).start();         new Thread(new ChicksYack()).start();     }     public void run() {         c.yack(Thread.currentThread().getId());     } }

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?


Given this HTML:

     Copy This Text	     <button type="button">Copy</button>

     When the user clicks on that button, how can I copy the the text from first TD tag to clipboard?

What is the best way to copy text to the clipboard (multi-browser)? I have tried: function copyToClipboard(text) {     if (window.clipboardData) { // Internet Explorer         window.clipboardData.setData("Text", text);     } else {         unsafeWindow.netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");         const clipboardHelper = Components.classes["@mozilla.org/widget/clipboardhelper;1"].getService(Components.interfaces.nsIClipboardHelper);         clipboardHelper.copyString(text);     } }  But in Internet Explorer it gives a syntax error. In Firefox, it says unsafeWindow is not defined. A nice trick without using :


I would like to know, which console command shows me the current proprietary amdgpu driver version installed. Somehow -after a bit of research- it is a bit of a secret.

I am using Ubuntu 18.04 LTS (Bionic Beaver).  by this command   uname -r   I got the version of current kernel used in my Ubuntu.  4.19.0-041900-generic    I would like to know more detail, such as the type of the version of file system, VFS, device drivers, etc contained in the kernel.  Is there a command line tool for that? or I have to check this out on launchpad.net?


I have my work flow with validation rule and eventho I am trying to not fire when those ownerId are submitting it. it still does   OR(      Owner.Id <> "00516000006OnYB" ,      Owner.Id <> "005G0000002YHAe" ,      Owner.Id <> "005G0000005Foy2" ,      Owner.Id <> "00516000006Tdoh" ,      Owner.Id <> "005G0000004qehs" ) &&  Order_Paperwork_Complete__c = TRUE

I have a requirement where a certain field can be edited without the validations firing for a particular user. Now I tried to write rule like LastModifiedId != '005000000000000AAA' but the validation was still firing. Then I realized that until the record saves, the LastModifiedId does not change and the validations still fire, as the LastModifiedId would not be updated to the exempted User.   Is there any workaround or a way to check the Id of the User who is currently editing the record?


If a function $f: \mathbb{R}\to\mathbb{R}$ is continuous and $f(x+y) = f(x) + f(y)$ for all $x,y\in\mathbb{R}$, then what is this function $f(x)$?

I need to find all functions $f:\mathbb R \rightarrow \mathbb R$ such that $f(x+y)=f(x)+f(y)$. I know that there are other questions that are asking the same thing, but I'm trying to figure this out by myself as best as possible. Here is how I started out:  Try out some cases:  $x=0:$ $$f(0+y)=f(0)+f(y) \iff f(y)=f(0)+f(y) \iff 0=f(0) $$ The same result is for when $y=0$  $x=-y:$ $$f(-y+y)=f(-y)+f(y) \iff f(0)=f(-y)+f(y) \iff 0=f(-y)+f(y)\iff \quad f(-y)=-f(y)$$ I want to extend the result of setting $x=-y$ to numbers other that $-1$, perhaps all real numbers or all rational numbers. I got a little help from reading other solutions on the next part:  Let $q=1+1+1+...+1$. Then  $$f(qx)=f((1+1+...+1)x)=f(x+x+...+x)=f(x)+f(x)+...+f(x)=qf(x)$$ I understood this part, but I don't understand why this helps me find all the functions that satisfy the requirement that $f(x+y)=f(x)+f(y)$, but here is how I went on:  Thus  $$f(qx)=qf(x)$$ and it should follow that $$f \bigg (\frac {1}{q} x\bigg)= \frac{1}{q}f(x)$$ where $q\not =0$, then it further follows that  $$f \bigg (\frac {p}{q} x\bigg)= \frac{p}{q}f(x)$$ where $\frac{p}{q}$ is rational, and lastly it further follows that  $$f (ax)= af(x)$$ where $a$ is real. Thus functions of the form $f(ax)$ where $a$ is real satisfies the requirement of  $f(x+y)=f(x)+f(y)$.  I don't know how much of what I did is correct\incorrect, and any help would be greatly appreciated. Also is there any way that I can say that functions of the form $f(ax)$ where $a$ is real are the only functions that satisfy the requirement of  $f(x+y)=f(x)+f(y)$? Or do other solutions exist?  Again, thanks a lot for any help! (Hints would be appreciated, I'll really try to understand the hints!)


The first hyperoperation $H_1(a, b) = a + b$ is addition, and is defined over the complex numbers. The second hyperoperation $H_2(a, b) = ab$ is multiplication, and is also defined over the complex numbers. The third hyperoperation $H_3(a, b) = a^b$ is exponentiation, and can be analytically extended from the natural numbers to the complex numbers for most complex bases $b$ and exponents $p$. The same is true for tetration $H_4(a, b) = \ ^ab$ and higher-rank hyperoperations.   My quesiton is then can the rank variable be extended to the rational/complex numbers: do there exist fractional-ranked and complex-ranked hyperoperations $H_n(a, b)$, where $n \in \mathbb{Q}$ or $n \in \mathbb{C}$?

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


Checking , it's not explicit how a migrated question will be ordered in the newest queue at the destination exchange, based on the time it was asked, or based on the time it was migrated.  I'm pretty sure it's the time the question was asked -- so if a question is migrated after 2 hours, it will be 2 hours back in the queue at the other end as well.

I noticed  was on the Programmers.SE for a day or so without any answers.  So, I answered it.  Not long after that, it was migrated to SO.  I was surprised to find that it was not located on the first several pages after being migrated.  It seems that it's .  A large reason for putting new questions at the top of the list is so that enthusiastic answerers can jump at the ones that interest them right out of the gate.  However, a question that's migrated is nearly hidden from these most eager answerers, because the question jumps immediately to a sad page that is normally full of questions that people have either answered or deliberately passed over.  Should newly-migrated questions get a chance at being displayed prominently along with their newly-posted counterparts?  EDIT: To be clear, I am not asking what the current behavior is (which has already been asked and answered in another question). I am asking if the current behavior best serves the SO community.


I have the following image set in sharedlatex:  \begin{figure}[h] \includegraphics[width=17cm]{sensors} \centering \caption{Sensor framework} \end{figure}   What is the best way to set this image as landscape? It is set as default in sharedlatex as portrait, but since the image is too big for it is not readable.

I have a figure I'm trying to insert which is in landscape and I'm using the following (snipped) code:  \documentclass[12pt, oneside]{book} \usepackage{graphicx} \usepackage{wrapfig} \usepackage{lscape} \usepackage{rotating} \usepackage{epstopdf}  \begin{document}  \begin{figure}[ht]     \includegraphics{../figures/pics/DivLibPropProfile}     \caption{Property profile of the diverse library compared to the compound pool.}     \label{fig:PropProf} \end{figure}  \end{document}   When I compile this with pdfLaTeX the output behaves as I'd expect – page in portrait with the caption at the bottom but the figure in the "wrong" orientation.  However when I compile using LaTeX, the page is turned landscape with the figure now in the correct orientation but with the caption at what is now the left of the page rather than under the figure, which you should get using \begin{landscape}.    When I do use the landscape environment and compile with LaTeX the caption the whole page is turned upside-down and everything is wrong.  Any ideas how I can get the correct orientation of landscape figure on landscape page with the caption under the  (attached for reference)?  I also need to use LaTeX rather that pdfLaTeX for another package to function.


I'm travelling to Orlando, then travelling to 2 other states on my trip via airplanes—how do I enter these on my ESTA application?

My friend has informed me there is a mandatory field for a 'US point of contact' (name and phone number) when he was applying for his ESTA. I don't see how they could make this mandatory as most tourists won't know any US residents.   I'm wondering if he is confusing 'contact name in the US' for an actual US resident when it is most likely wanting to know who is the group contact while on holiday?  He's insisting that it means US resident and I can't seem to persuade him otherwise!


After clicking on the bottom left 9 dots icon, aka Show Applications, there is a launcher. I can't find its actual name.  The text under the icons is truncated to the width of the icon, truncating almost every application name, and it's making the launcher very uncomfortable to use.  What can I do to see the application names entirely ?

This question has been asked before but that was over 6 years ago and I'm hoping to get a more updated answer.     Basically when I search for an application, if the name is too long it's shortened with an ellipsis (...). I want to know how to change it so that the whole name is displayed. Example:   I hope it's OK to ask for an updated answer.  I'm using Ubuntu 17.10 with GNOME Shell 64-bit.


I have a British Airways booking from GLA to FCO with a stopover in LHR (booked as a single booking).  The booking was a reward booking made with Avios points.  My issue is that I will now be in London on the date of the first leg and therefore only require the second leg.  If I don't fly the first domestic leg, will the second leg to Italy be automatically cancelled?  Also, if I contact them beforehand, would there be additional charges in changing the flight?  Many thanks in advance for any answers.

I've a friend that booked a round-trip journey. He booked A-to-B and B-to-A. Somehow he needed to be earlier at location B, so he took a train and did not take the flight from A to B.  When he went to the airport to take the "back home" flight (B-to-A), he was informed that his ticket was canceled because he did not take the A-to-B flight. They canceled the ticket and sold it to someone else.  Is this normal? The company said it was their right to do so, and he could not get the flight back. The company was Iberia.


I've seen some previous questions about transferring points between sites. They are usually quite unequivocally answered that points should not be transferrable, for fairly obvious reasons such as reputation as a programmer not being equivalent to that of a cook.  However, I would like to request that it be possible to bounty points on any site. When setting bounties, there doesn't seem to be a good reason not to allow points from other sites to be used because you are not misrepresenting your own reputation.  I could imagine a problem if it was possible to accumulate disproportionate reputation on some sites and use that as currency elsewhere. I do not think this is generally the case - it is easiest to accumulate points on the larger sites anyway, where the points themselves are most 'trusted'.

Here's one to get shot down: How about letting bounties to be set using the reputation gained through the use of another site? So, for instance, I'm a programmer with a high Stack Overflow rep who hates using computers. Wouldn't it be useful for me to be able to exchange some of my excess Stack Overflow credit to incentivise a question on Super User?   Or perhaps I'd like to highlight a question on Meta Stack Overflow, but I don't spend my time there.


#!/usr/bin/env bash # set -x  readonly err_code=256  my_function () {     return $err_code }  my_function  echo $? # print 0   If the err_code exceed the 255, all the top bits will be dropped just like unsigned byte, how to explain this? Is there any feature document for this? I googled a lot w/o luck.  Thanks!  UPDATE:  Okay, I got it, it doesn't just happen only in shell but Unix-based system, the shell function is also called by command substitution. Thanks for linked questions!

If yes, on which operating system, shell or whatever?  Consider the following java program (I'm using java just as an example, any language would be good for this question, which is more about operation systems):  public class ExitCode {     public static void main(String args[]) {         System.exit(Integer.parseInt(args[0]));     } }   Running it on Linux and bash, it returns always values less equal 255, e.g. (echo $? prints the exit code of the previous executed command)  > java ExitCode 2; echo $? 2  > java ExitCode 128; echo $? 128  > java ExitCode 255; echo $? 255  > java ExitCode 256; echo $? 0  > java ExitCode 65536; echo $? 0     EDITED: the (only, so far) answer below fully  explain what happens on UNIXes. I'm still wondering about other OSes.


I come from the windows world trying to switch to Linux. Sorry for the naïve question but is there something like "common Linux commands"?  For example in Windows, the command line is pretty limited, but it is common between all windows. So if you know what the dir or mkdir command does and what switches it takes, you can use any version of Windows and be sure that your BATCH files work.  In Linux however, if I understand correctly there are many ways to do the same thing. For example for editing files you may use EMACS or VIM. Even the shells have a wide variety (is bash the de facto standard?)  From what I understand so far, the command line is way more flexible (and versatile) than Windows CMD. Something like Busybox promises to pack a whole lot of commands in one project. Anyway, this is all too overwhelming, so I was wondering if there is a small set of Linux commands that are common between all systems and I can carry on my daily tasks on every Linux machine regardless of its distro.

I would like to know which are the standard commands available in every Linux system.  For example if you get a debian/ubuntu/redhat/suse/arch/slackware etc, you will always find there commands like:  cd, mkdir, ls, echo, grep, sed, awk, ping etc.  I know that some of the mentioned commands are shell-builtin but others are not but they are still always there (based on my knowledge and experience so far).   On the other hand commands like gawk, parted, traceroute and other quite famous commands are not installed by default in different Linux distributions.  I made different web searches but I haven't found a straight forward answer to this.  The purpose is that I would like to create a shell script and it should make some sanity checks if the commands used in the script are available in the system. If not, it should prompt the user to install the needed binaries.


I expirienced  virus attack on my laptop. It attacks through the browser. Browser console opens automatically and some strange script starts to execute. I stopped the internet right there. No harm is made yet but I am afraid to go online. Please can you suggest what should I do now. Note that I am using kaspersky internet security. The virus is able to breach that which is scary.

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.


Based on my “pay no tax” research I found this gift law. I think I’m on the right track and would like clarification because, I literally detest the government for very good reasons; not the least of which their employees murdered my son and destroyed my family without consequence. So, to give them even one penny is unacceptable to me.  Can I teach children an invaluable skill for free and provide a website or PayPal link for anyone who appreciates the result of my gift to their child and wishes to gift me money (or maybe they don’t have a child but believe in my revolutionary contribution to the future) as they see fit, up to $10K?

If somebody gives me reasonable advise or share important to me information.   Being attentive I would like to make a little gift or give some little (<100$) amount of money (cash/wire/online) for that   How it would be classified by IRS?   Which obligations originate with this matter for me and my party?  How to do this in a most comfortable way to my party?


Is there anybody who knows how to solve the following?  Qn1: Show that for any integer n ≥ 0, one has gcd( n!+1, (n+1)!+1 ) = 1  Qn2 :Why is it that the greatest common divisor of any two integers a,b∈Z is defined as the unique non-negative integer gcd(a,b)∈Z, where Z is ≥ 0 such that:  {ar + bs ∈ Z : r,s∈Z} = gcd(a,b)*Z

I guess the canonical proof to this problem is attained using the Euclidean Algorithm (I've seen some posts like this already). I came with this proof, based on gcd definition and some divisibility properties. I'd like to know if it seems correct to you.  Proof:  Let $d$ be a common divisor of both terms. Then $n! +1$ = $d$.$s$ and $(n+1)! +1 = d.t$, for $s, t$ in $\Bbb Z/{0}$. Therefore $(n +1)n! + 1 = n.n! + n! + 1 = n.n! + d.s = d.t$, and it follows that $d|n.n!$. Now, since $n=d(t-s)/n!$, $d|n$. Then $d$ must divide 1 ($n! + 1 = d.s$), and $|d|$ = 1. Being $d'$ another common divisor, it is clear that $d'$ must divide 1 also, and therefore it does divide $d$, so we have $d = gcd(n! + 1, (n+1)! +1) = 1$


The question is  find the remainder when $\begin{vmatrix} { 2014 }^{ 2014 } & { 2015 }^{ 2015 } & { 2016 }^{ 2016 } \\ { 2017 }^{ 2017 } & { 2018 }^{ 2018 } & { 2019 }^{ 2019 } \\ { 2020 }^{ 2020 } & { 2021 }^{ 2021 } & { 2022 }^{ 2022 } \end{vmatrix}$ is divided by 5. While googling, I found this answer  but unfortunately I don't have the skill level to understand that answer. It says I'll have to use Fermat's little theorem() but I can't figure out how to apply it in this question.

Find the remainder when the determinant $\begin{vmatrix} { 2014 }^{ 2014 } & { 2015 }^{ 2015 } & { 2016 }^{ 2016 } \\ { 2017 }^{ 2017 } & { 2018 }^{ 2018 } & { 2019 }^{ 2019 } \\ { 2020 }^{ 2020 } & { 2021 }^{ 2021 } & { 2022 }^{ 2022 } \end{vmatrix}$ is divided by $5$.   I'm aware that this problem has a number-theoretic solution involving congruence relations. But considering that this was asked as a multiple-choice question in a test, what should be the best way to approach problems like this?  The options were $(a)\quad1\quad (b)\quad2\quad (c)\quad3\quad (d)\quad 4$