Some questions or answers can take a while to write.  For example, I had written a question on , and one day it got silently deleted, meaning I cannot access it any more (luckily I had a backup, without all the links that used to be though).   Why don't you notify the author about the deletion, and send the removed content by email? I find that removing content and leaving no access to it without warning is highly disrespectful to the people who took the time to write it.  Here is the question I had asked that got removed. As you can see, it would have been painful for me to re-write the whole question if I hadn't saved it:     Question: Are there any recent results on the performances of head   tracking devices used to move the mouse cursor in comparison with   traditional mice? (e.g. using Fitts's law)      Question's details: As I use a head tracking device to move the mouse   cursor for efficiency purpose, I was curious to know whether the   Fitts's law can be applied to it (i.e. is not restricted to hands).   Fitts's law says "Fitts' law has been shown to apply under a variety   of conditions, with many different limbs (hands, feet, head-mounted   sights, eye gaze)". The wiki entry has some interesting references:      Errol R., Hoffmann (1991) "A comparison of hand and foot movement   times". Ergonomics, Vol. 34, No. 4, pp. 397-406 >A comparison of hand   and foot movement times. (foot vs hand results are clearly presented)      So, R. H. Y. and Griffin, M. J. (2000) "Effects of target movement   direction cue on head-tracking performance". Ergonomics, Vol. 43, No.   3, pp. 360–376. >Effects of a target movement direction cue on hea...   [Ergonomics. 2000] (head moves aren't used to move a cursor)      So, R. H. Y. and Cheung, K. M., (2002) "Combined and interacting   effects of hand and head movement lags on discrete manual performance   in a virtual environment." Ergonomics, 45, 2002, pp. 105–123. >      (head moves aren't used to move a cursor)      So, R. H. Y., Cheung, K. M. and Goonetilleke, R. S. (1999)   "Target-directed head movements in a head-coupled virtual environment:   predicting the effects of lags using Fitts' law". Human Factors, Vol.   41, No. 3, 1999, pp. 474–486. > Target-directed head movements in a   head-coupled... [Hum Factors. 1999] (head moves are used to move a   cursor but a lag is introduced and there is no direct comparison with   hands. Also I don't have access to the full article.)      I skimmed through them but it seems like none of them address the   performances of a head tracking device to move the mouse cursor.   Furthermore they are pretty old and I don't know to what extent those   results can be extended for hands-free mouse performances. Lastly for   whatever reason most of them seem to focus on lag / delay. Are there   any recent results on the performances of head tracking devices used   to move the mouse cursor in comparison with traditional mice?      The best I have found so far is Ashdown, Mark, Kenji Oka, and Yoichi   Sato. "Combining head tracking and mouse input for a GUI on multiple   monitors." CHI'05 extended abstracts on Human factors in computing   systems. ACM, 2005. Combining head tracking and mouse input for a GUI   on multiple monitors, but results seem preliminary, don't use Fitts's   law, and anyway just use head tracking to switch between different   monitors.      I'm also interested in eye tracking as a mouse and foot mice   performances (Errol R., Hoffmann (1991) gives hints for the latter).   Ideally I would like to have table comparing all these ways to control   the mouse ( hand / head / foot / eye).

When something of yours is deleted (answers, comments, questions, Area 51 proposals) it would be nice to get some kind of notice other than just not being able to find it anymore. You receive notices for everything else that can be done to something of yours, and often relating to something of yours, so why not this?  I've never had anything moved that I know of, but if that doesn't send you a notice I'd say it should too.  If you don't know that this has happened, then one might be tempted to think there was some user or software errors and just post again.


When are you going to recover the ability to make CAPS work like Ctrl. Like in all previous versions?   This is really critical as I am using emacs key-bindings and this is a one huge stopper and forces me to drop Ubuntu, at least until I see it fixed.

Can anyone explain how to swap Caps Lock and Ctrl keys on Ubuntu desktop under Unity. I use it to avoid .


I am doing some asynchronous tasks with http to fetch some data.   When I close the app in the middle of an asynchronous operation, I get an a NullPointerException error. This seems to be happening because the asynchronous task is being competed and onTaskCompleted is called; But the app is already closed.  Does anyone know how to handle this?  I'm running with Android Studio, android version 4.4.2. Galaxy S4.  java.lang.NullPointerException         at com.example.lu.seed_2.Tabs.Tab4$3.onTaskCompleted(Tab4.java:174)         at com.example.lu.seed_2.ArticleAsync.onPostExecute(ArticleAsync.java:36)         at com.example.lu.seed_2.ArticleAsync.onPostExecute(ArticleAsync.java:11)         at android.os.AsyncTask.finish(AsyncTask.java:632)         at android.os.AsyncTask.access$600(AsyncTask.java:177)         at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)         at android.os.Handler.dispatchMessage(Handler.java:102)         at android.os.Looper.loop(Looper.java:157)         at android.app.ActivityThread.main(ActivityThread.java:5356)         at java.lang.reflect.Method.invokeNative(Native Method)         at java.lang.reflect.Method.invoke(Method.java:515)         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)         at dalvik.system.NativeStart.main(Native Method)   As requested, here is the onTaskComplete code  articles = convertJsonToArticles(httpResult.getBody()); articleAdapter = new ArticleAdapter(getActivity().getApplicationContext(), articles);  //<-- APP CRASHES HERE listView = (ListView) getActivity().findViewById(R.id.mobile_list4); listView.setAdapter(articleAdapter); listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {     @Override     public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {         Intent intent = new Intent(getActivity().getApplication(), WebViewActivity.class);         intent.putExtra("_id", articles.get(i).getId());         startActivity(intent);     } }); listView.setOnScrollListener(new AbsListView.OnScrollListener() {     @Override     public void onScrollStateChanged(AbsListView absListView, int scrollState) {      }      @Override     public void onScroll(AbsListView absListView, int firstVisibleItem, int visibleItemCount, int totalItemCount) {         int itemsLeftCount = totalItemCount - firstVisibleItem;          if (itemsLeftCount > 8) {             return;         }          if (isLoadingMore == true) {             return;         }         loadMoreArticles();     } }); listView.addFooterView(footerView); showNotLoading(); v.refreshComplete();

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?


How can I find the polygon and vertices count for all the objects in the scene in Blender 2.9? It used to be on the bottom right corner, but in blender 2.9, its not there. Here is a screenshot. The top screenshot is Blender 2.83, and the bottom one is Blender 2.9. Thanks

I don't see the statistics information that's supposed to be on the status bar running along the bottom of the main window towards the right in version 2.9.


I messed up at some point during modeling and had to reconnect some edges but now I don't have the vertices I need to continue. How can I fix the faces so it fits the rest of the model?

I tried crating faces but it left missing edges. In the end I was left with all the right lines but there was no vertex in the center.    Here's a follow up image in case you're wondering what I mean. Notice how there's no vertex in the center.


Does the anime for hunter x hunter stop in episode 148? I am asking this since there is a scene here on 3:53  and it didn't look like a 1999 anime in Hunter x hunter so I was curious

The Hunter X Hunter anime stopped in episode 148. I wonder why?   Is it because Hunter x Hunter is already finished?


I'm taking abstract algebra right now and I don't know where to begin with this question.

I was told to prove $\gcd(ab,c)=1$ then $\gcd(a,c)=1$.  I picked a number $p$ that goes into $ab$ and $c$, so $ab=px$ and $c=py$. but now what?? I tried $abc=p^2xy$ but then I can't.  Please help me!


Ubuntu (20.04) just keeps changing my audio-output config. I need this pc for work and i need to use my headset for calls and so on. Everytime after a reboot everything is f*** up again and some programs would use the headset, others use the hdmi output. If i change the output via the settings, it does not have an effect, the hdmi output is still used. I have an amd graphics card (Radeon R9 380). Please tell me - how can i disable specific audio interfaces? I only need the line-out and the front-panel line-out - all other options (hdmi/displayport) simply need to go! I tried pavucontrol to disable some interfaces, it does work sometimes but will always be reset after some time. This is really annoying!

At each reboot, PulseAudio sets a sink (in my case, "HDMI Audio Output") as the default.  So, at each reboot, I don't hear any sound, and need to reconfigure the default sink each time to "Analog Output".  How do I remove/disable a specific sink such as HDMI, or set a default sink that overrides the existing sink?


Evaluate   $$\int_{0}^{\pi}\frac{dx}{1+2\sin^2x}$$   My approach $$\Longrightarrow\int_{0}^{\pi}\frac{dx}{1+2\sin^{2}x}=2\int_{0}^{\frac{\pi}{2}}\frac{\sec^{2}x}{1+3\tan^{2}x}dx=\frac{2}{\sqrt{3}}\left[\tan^{-1}\left(\sqrt{3}\tan x\right)\right]_{0}^{\frac{\pi}{2}}$$ $\tan x$ is undefined at $\dfrac{\pi}{2}$.  So I need to solve $\lim_{x\rightarrow\frac{\pi}{2}}$$\left[\tan^{-1}\left(\sqrt{3}\tan x\right)\right]$. I don't know how to solve.

After making u substitution two times, I am getting indefinite integral as $$\int\limits\dfrac{dx}{1+2\sin^2x} = \dfrac{\arctan(\sqrt{3}\tan(x))}{\sqrt{3}}+ C$$  I am stuck at working the bounds because I am getting $0$ but the answer needs to be $\pi/\sqrt{3}$.  I think $\arctan(x)$ is defined in $-\pi/2 \lt x\lt\pi/2$ while making u substitution. However I don't see how to use this observation to my advantage. Can anybody help in getting the answer and understanding whats going on. Thanks !


I want to implement a template in a class file instead of implement all the code in the same file. But the problem is I have a linked error and I don't know what to do in order to solve it ? If you have any idea in order to help it will be graceful.  Main.cpp   #include <iostream> #include <string> #include "Myclass.h" using namespace std;  int main() {     Myclass<int> firstObject;     firstObject.setValue(2);     int nbr = firstObject.getValue();       system("PAUSE");     return 0; }   Myclass.cpp  #include "Myclass.h"   template <class Temp> Myclass<Temp>::Myclass() { }  template <class Temp> void Myclass<Temp>::setValue(Temp a) {     first = a; }  template <class Temp> Temp Myclass<Temp>::getValue() {     return first; }   Myclass.h  #pragma once template <class Temp>  class Myclass { public:     Myclass();     void setValue(Temp a);     Temp getValue(); private:     Temp first; };

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


I'm pretty new to Blender, but I am stuck on one thing: every time I try to move a particular vertex, or edge loop, or whatever, using the Translation Widget or the "G" key, a number of other vertices and edges move as well, as if the rest of the object is reshaping as well.  However, I want to simply move the vertices or edges that I have selected, while keeping all other vertices fixed.  How could I do that?

My problem is that I sometimes lose the ability to independently translate or otherwise transform any parts of a single mesh. If I try, for example, to just translate several faces, edges, or vertices, then the entire mesh will stretch and displace itself in order to follow the translation. Or, alternatively, if I try to translate just one face then the whole mesh will move as if I'm translating in Object Mode.  I'm not really sure I know how to describe this problem properly. I don't even know how to reliably reproduce it. It seems to happen to any given mesh at random, and it doesn't stop happening to that mesh unless I delete and remake it.  I assume that I must be doing something wrong to cause this to happen. Does anyone have any ideas? Thanks.


I was perusing the  of GIS to make sure that my next question is on-topic for their site and I noticed something that was rather odd for a graduated site, a link that says        it appears that this is on other Help Pages as well, Meta being one of them.  Is there a reason why this is kept linked? Note that this is not a duplicate of  asking for it to be removed.

When I go to /help/asking on any Stack Exchange site (), there is a link to How to Ask Questions in Private Beta (). It starts with:  Welcome to the private beta for [site] The tone and quality of the questions asked during this temporary private beta are critically important. If the private beta doesn't produce enough high quality expert level questions, it won’t proceed onward to the public beta. To help ensure your site makes it out of private beta, here are some tips:  There is no disclaimer or similar that this is outdated. This may lead to unnecessary confusion. I understand that that it is useful to keep this page in public pages for documentary purposes, as it may be linked in early Meta discussions, but it should:  not be listed in the table of contents (/help/asking) have a disclaimer


I have a problem with my update trigger. I created Order and Order Line Item custom objects, same and related with Opportunity and Opportunity Line Item. When I create an Order, a related Opportunity also created automatically. Their relations are:   Lookup on Order to Opportunity (Opportunities__c) Lookup on Opportunity to Order (Orders__c) Lookup on Order Line Item to Order (Order__c) Lookup on Order Line Item to Product2 (Product2__c) Lookup on Product2 to Order Line Item (Order_Line_Items__c)   When I update a product on Order Line Item, that product doesn't get updated on related Opportunity Line Item. This trigger doesn't update anything but I'm not getting any error. Do you have any idea what am I missing?  trigger OrderLineTrigger on Order_Line_Item__c (after update) {   if(trigger.isUpdate){      List<ID> orderlistid= new List<ID>();     List<ID> pricebooklistid= new List <ID>();     List<Order_Line_Item__c> updatelist=trigger.new;      for(Order_Line_Item__c updatelists:updatelist){       orderlistid.add(updatelists.Order__c);       pricebooklistid.add(updatelists.Product2__c);     }        List<Opportunity> opportunitylist=new list<Opportunity>([Select Id,Orders__c From Opportunity Where Orders__c IN:orderlistid]);       List<PricebookEntry> pricebookentrylist=new List<PricebookEntry>([Select Id,Product2Id From PricebookEntry Where Product2Id IN:pricebooklistid]);     List<ID> opportunityid=new List<ID>();     List<ID> pbeid=new List<ID>();      for(Integer k=0;k<opportunitylist.size();k++){       opportunityid.add(opportunitylist[k].Id);     }      for(Integer l=0;l<pricebookentrylist.size();l++){       pbeid.add(pricebookentrylist[l].Product2Id);     }      List<OpportunityLineItem> oppLists=new List<OpportunityLineItem>([Select UnitPrice, Quantity, PricebookEntryId, OpportunityId, Id From OpportunityLineItem Where PricebookEntryId IN:pbeid AND OpportunityId In:opportunityid]);       for(Integer i=0;i<oppLists.size();i++){        for(Integer j=0;j<opportunitylist.size();j++){          if(oppLists[i].OpportunityId==opportunitylist[j].Id){            for(Integer n=0;n<pricebookentrylist.size();n++){              if(oppLists[i].PriceBookEntryId==pricebookentrylist[n].Id){                for(Integer l=0;l<updatelist.size();l++){                  if(updatelist[l].Order__c==opportunitylist[j].Orders__c && updatelist[l].Product2__c==pricebookentrylist[n].Product2Id ){                    oppLists[i].UnitPrice=updatelist[l].UnitPrice__c;                   oppLists[i].Quantity=updatelist[l].Quantity__c;                 }               }             }           }         }       }     }         update oppLists;   } }

I created Order and Order Line Item custom objects they are similar and related to Opportunity and Opportunity Line Item. When I create an Opportunity, a related Order automatically created, when I add a product to Opportunity Line Item, same product be added automatically to Order Line Item of related Order. I don't have a problem with inserting product but I can't make it update. How to achieve it? This is my code for insert but I couldnt make that product on Order Line Item update, please help me. Thanks.  trigger CreateOrderLineItem on OpportunityLineItem (after insert, before delete) { if(trigger.isInsert){      Map<Id,Product2> proMap = new Map <Id,Product2>([Select Order_line_Items__c From Product2]);     List<Order_Line_Item__c> oliList = new List<Order_Line_Item__c>();          for(OpportunityLineItem opli : [Select opportunityid, Id, pricebookentryid, unitprice, quantity From OpportunityLineItem Where id IN:Trigger.newMap.keyset()])         {                 for(Opportunity oppList : [Select id, Orders__c From Opportunity Where id=:opli.OpportunityId])                 {                                         for(PricebookEntry pbe : [Select pricebook2id, product2id, unitprice, IsActive From PricebookEntry Where Id=:opli.PricebookEntryId])                     {                         for(Pricebook2 pb2 : [Select Id  From Pricebook2 Where Id=:pbe.Pricebook2Id])                         {                         for(Product2 pro : [Select ProductCode, IsActive, Order_Line_Items__c From Product2 Where Id =: pbe.product2id])                         {                             for(Order__c orrList : [Select Id, Opportunities__c From Order__c Where Opportunities__c =:oppList.id])                             {                                 Order_Line_Item__c oli = new Order_Line_Item__c(product2__c=pro.id, Order__c=orrlist.id, UnitPrice__c=opLi.UnitPrice, Quantity__c = opli.Quantity, ProductCode__c=pro.ProductCode, id=pro.Order_Line_Items__c);                                 oliList.add(oli);                             }                         }                         }                     }                 }         }         if(oliList.size()>0)         {         insert oliList;         } }


I am looking to be able to tell how many records, i.e., db-table rows, a jdbc query returns without iterating through the resultset.   I tried -- however didn't work the way I thought it would:          if (rSet.getFetchSize()==0)          System.out.println("no results returned");         while (rSet.next())             System.out.println(rSet.getString("transactionID"));         rSet.next();   The above code snippet prints the first console message, then gets into the loop and iterates to execute the second console message on 1+ results.   How to tell the number of records fetched? what's ResultSet.getFetchSize() for?  //-----------------------------------  EDIT: looking to tell this count without any iterations on the ResultSet. convinced that this isn't possible though. the answers to the referred Q are saying so.

I've executed a JDBC query to obtain a resultset. Before iterating over it, I'd like to quickly find out how many rows were returned. How can I do this with high performance?  I'm using Java 6, Oracle 11g, and the latest Oracle JDBC drivers.


If $\alpha$ and $\beta$ are roots of monic polynomials (not necessarily the same polynomial) in $\mathbb{Z}[x]$, is $\alpha + \beta$?  I know that $\alpha + \beta$ will be the root of some monic polynomial in $\mathbb{Q}[x]$, but I'm not sure if the coefficients will be integers. I've tried to find a counterexample but I've had no success, which leads me to believe it's probably true. I'm not sure how to proceed with a proof.

Suppose $E/F$ is a field extension and $\alpha, \beta \in E$ are algebraic over $F$. Then it is not too hard to see that when $\alpha$ is nonzero, $1/\alpha$ is also algebraic. If $a_0 + a_1\alpha + \cdots + a_n \alpha^n = 0$, then dividing by $\alpha^{n}$ gives $$a_0\frac{1}{\alpha^n} + a_1\frac{1}{\alpha^{n-1}} + \cdots + a_n = 0.$$     Is there a similar elementary way to show that $\alpha + \beta$ and $\alpha \beta$ are also algebraic (i.e. finding an explicit formula for a polynomial that has $\alpha + \beta$ or $\alpha\beta$ as its root)?    The only proof I know for this fact is the one where you show that $F(\alpha, \beta) / F$ is a finite field extension and thus an algebraic extension.


I just want my LaserJet 1000 printer to work with Ubuntu live CD and save the settings.  I am using Ubuntu 12.04 and I thought Ubuntu already had hplip to work with LaserJet 1000 little box. But when I connect the printer it causes an error and won't download the required plugin for my printer.  Any help will be appreciated.

I've already installed hplip, it printed a test page, but it won't print from any program. It shows the printer in the list of printers, and it's checked as the default printer. I've restarted a couple times.   When I plugged the USB cable for the printer into the computer after installing hplip, it said printer detected. Then after a couple seconds it said the printer was ready for use.   When I send something to the printer, a pop-up shows that a document was sent to the printer - but there's a triangle with an exclamation point in it next to the message. A few seconds another pop-up indicates that the printer has completed printing the job but it didn't print anything.


I have two integral questions listed below:  $$\int_0^{\infty} \frac{\ln x}{x^2 + 1} dx \qquad (1)$$ $$\int_0^{\infty} \frac{(\ln x)^2}{x^2 + 1} dx \qquad (2)$$  The first one, I've solved it, by separating the integral into integrals over $0$ to $1$ and over $1$ to $\infty$; with substitution, it becomes zero. But the second one wasn't that easy. Can someone give me help? Wolfram alpha says the answer is $$\frac{\pi^3}{8}.$$

How do I compute      $$\int_0^\infty \frac{(\log x)^2}{1+x^2} dx$$   What I am doing is take   $$f(z)=\frac{(\log z)^2}{1+z^2}$$  and calculating   $\text{Res}(f,z=i) = \dfrac{d}{dz} \dfrac{(\log z)^2}{1+z^2}$ which came out to be $\dfrac{\pi}{2}-\dfrac{i\pi^2}{8}+\dfrac{i\pi}{2}$  Im not too sure how to move on from here. the given answer is $\dfrac{\pi^3}{8}$  Any help will be appreciated. thank you in advanced.


I want to write a shell script that accepts a URL and an output markdown file, and adds that URL plus some metadata to the end of that file. It is possible that this script is invoked concurrently, resulting in concurrent echo $some_multiline_thing >> files.  Per this , this can result in corrupt data being written to file. How do I synchronize the writes so that the appending writes all happen but atomically? (The order of the appends doesn't matter to me.)  Update: I found a half-baked solution  function sync-append() {     local file="$1"     local text="$2"      local lock_fd     {         exec {lock_fd}>>$file         flock -x "$lock_fd"         echo "$text" >> $file     } always {         exec {lock_fd}>&-     } }   This solution relies on zsh's always, which may not be invoked (with, e.g., kill -9).

I have a bash script that makes a cURL request and writes the output to a file called resp.txt.  I need to create an exclusive lock so that I can write to that file and not worry about multiple users running the script and editing the text file at the same time. Here is the code that I expect to lock the file, perform the request, and write to the text file: ( flock -e 200 curl 'someurl' -H 'someHeader' > resp.txt ) 200>/home/user/ITS/resp.txt  Is this the correct way to go about this?  My actual script is a bit longer than this, but it seems to break when I add the flock syntax to the bash script. If someone could explain how these file descriptors work and let me know if I am locking the file correctly that would be awesome!


I have lots of dump files in 2 different directories that need to be uploaded using rsync, I want to run rsync for each dump file simultaneously to save time.  Dump Files:  Dir1:  -  /u05/expdpdump/exppdb/dir1/NoTDE_CDB_FULL1_01.dmp -  /u05/expdpdump/exppdb/dir1/NoTDE_CDB_FULL1_02.dmp -  /u05/expdpdump/exppdb/dir1/NoTDE_CDB_FULL1_03.dmp -  /u05/expdpdump/exppdb/dir1/NoTDE_CDB_FULL1_04.dmp  Dir2:  -  /u05/expdpdump/exppdb/dir2/NoTDE_CDB_FULL2_01.dmp -  /u05/expdpdump/exppdb/dir2/NoTDE_CDB_FULL2_02.dmp -  /u05/expdpdump/exppdb/dir2/NoTDE_CDB_FULL2_03.dmp -  /u05/expdpdump/exppdb/dir2/NoTDE_CDB_FULL2_04.dmp   Following rsync Command to run for each dumpfile from each directory in the background:  rclone sync /u05/expdpdump/exppdb/NoTDE_CDB_FULL_01.dmp NoTDE_Mig1:IC_dbbackup_config_datapump_xxxxxx   I managed to get the desired output to run rsync for each file, however, i want to track the start and end time for each file as well as overall elapsed time for the rsync jobs running in background.  using time in for loop will provide only elapsed time for each file, however i also need overall elapsed time of Start and End Time after completing all jobs   dumpdir1="/u05/expdpdump/exppdb/dir1"  for i in $dumpdir1/*.dmp do      echo " time rclone sync  $i NoTDE_Mig1:IC_dbbackup_config_datapump_v00rcfh_iad3p2 &" done  dumpdir2="/u05/expdpdump/exppdb/dir2"  for i in $dumpdir2/*.dmp do     echo " time rclone sync $i NoTDE_Mig1:IC_dbbackup_config_datapump_v00rcfh_iad3p2 &" done```

I'm confused about the difference or advantage (if any) of running a set of tasks in a .sh script using GNU parallel  E.g. 's answer:  parallel ./pngout -s0 {} R{} ::: *.png   rather than say looping through them putting them in the background &.  E.g. 's answer:  #copied from the link for illustration for stuff in things do ( something   with   stuff ) & done wait # for all the something with stuff   In short are they just syntactically or practically different? And if practically different when should I use each?


After updating Firefox this morning to 58, it fails to play any sounds (eg. YouTube plays without sound or Google Calendar events sounds). With the as of yesterday most recent version (57.0.4?), everything worked fine. I now get the message      To play audio, you may need to install the required PulseAudio software. []   The link there isn't of any help, as it just suggests to make sure that PulseAudio (which is required from version 52) is correctly installed. As I said, it worked fine with version 57, and I can play sounds with PulseAudio like this:  paplay /usr/share/sounds/freedesktop/stereo/message.oga   Any suggestions?  I'm running Ubuntu 17.10 (GNU/Linux 4.13.0-31-generic x86_64) with xmonad, no flash installed and the only things that updated since yesterday were Firefox and keybase.

I would like to install the restricted extras package, which I didn't select during the install. How can I do that?        is a meta-package that installs:         Support for MP3 and unencrypted DVD playback   Microsoft TrueType core fonts   Flash plugin   codecs for common audio and video files


I was reading through the . What does the following passage refer to?        Some premium or additional features of Stack Overflow (including without limitation Stack Overflow for Teams) may require a payment obligation for access and use. You are solely responsible for ensuring that your payment obligations, if any, remain current and not in arrears. In the event Stack Overflow charges for features you will be clearly notified of the terms of any payment obligations and provided the opportunity to refuse such obligations before you incur any charges. Please note, however, that your refusal to accept payment obligations may result in your inability to access or use certain premium or additional features of Stack Overflow.      What "premium or additional features" exactly cost money?

I once , but that was . Now, , and they have , but where's the business model? The  its own Q&A about its site (since it wasn't included in the ), and just about the only dig in there that halfway has merit is the business model dig:  We switched to a premium model to keep out of the Venture Capital business (been there, done that, got the t-shirt). Companies like StackExchange couldn't do it without the VC cookie jar. Where's the model? Huh, Spolsky? (I’m sorry. Did that slip out?)  It hurt, but I can't help but wonder if they're on to something.  How would Stack Overflow Internet Services pay back the VCs? Ad revenue alone?  There is only one 'paid' product, Stack Overflow careers, but it doesn't seem like that could sustain a business as large as Stack Overflow (Joel once mentioned on his blog that his jobs board brought in an extra million a year in revenue). So what does Stack Overflow do when the VC cash runs out? Is this a get-big-and-take-the-company-public maneuver? Is that the only viable business model for Stack Exchange? Edit: With the size of Stack Overflow's team, it isn't a stretch to say that payroll is at least $2 million  a year, probably as much as 4 when you think about benefits (average 120K for a developer in New York City; x2 for benefits/taxes/all-that-other-good-stuff). Office space can't be cheap, so how long does $6 million last before you need another VC infusion?


Let $$S \subset N_{100}= \{1,2,3,4, \dots, 100 \}$$ with $|S|=51$. Then prove for any such $S$ it is possible to select two numbers from $S$ such that one is a multiple of other.  I wasn't able to proceed. How should I start. I think it needs Pigeon Hole Principle.

I want to prove that if you choose $101$ numbers from the set $\{1,2,3,4,\dots ,200\}$, there are always two numbers such that one divides the other with no remainder. The prove should involve the "pigeonhole principle".  I am not sure how to define the pigeonholes and how to define the pigeons. Any assistance with the proof will be most appreciated.  Thank you.


I am writing a script to download build and install a bunch of packages. Building sometimes takes a while, and installing requires root priviledges:  make; sudo make install  What happens alot is that when a build takes a while I need to keep entering my password. I want to be able to only enter it once. I could call the script with root access, but then (as I understand it) every call it makes will be with root priviledges. I don't want this because then, eg., many files and folders get created that can't be deleted without root access.   so what is the best way to do this?

Data   I want operator users on this machine to mount their own cifs shares The sudoers file already contains the /bin/mount -t cifs //*/* /media/* -o username=* command for all operators I want the users to mount a cifs share through a script typing the password only once, not twice. The sudo password and the cifs password are identical.   What I already have  This script works:  #!/bin/bash sudo 'mount -t cifs //192.168.1.1/home /media/$USER/home -o username=$USER'   ...but it requires the users to type the same password twice!     Once for sudo Once for the mount itself   This would also work:  #!/bin/bash echo -n Password:  read -s szPassword echo $szPassword | sudo -S sh -c 'echo $szPassword | mount -t cifs //192.168.1.1/home /media/$USER/home -o username=$USER'   ...but this would require me to allow all operator users to be able to sudo sh (major security problem)  Question  How to mount a cifs share in bash¹ without putting sh in the sudoers file nor creating a permanent/temporary file???  Note 1: no python, perl, C, Go, ... please? Note 2: I know I can just remove the password through the sudoers file, but I'm trying to tighten security, not loosen it, without giving up convenience...


I suppose this is an extension to   First off, I'm presuming that new users cannot answer their own questions? Is this correct?  So they can self answer, but I've seen quite a few occasions where they don't!  In this  the user, has edited the question to include an answer. I've seen this quite a lot. I've always flagged this as      Unclear what your asking   For me, the user editing the question in this manner invalidates the question. Is this the correct thing to do?  Could/should we make the answer my own question link more obvious?  Did have a quick browse about meta but couldn't see anything specific to this scenario.

Reference question:   Sometimes users solve their own questions, which is great. Sometimes they say they've solved it and move on, which is not so great. The above question is middle-ground: the user posted an answer to his own question, but as an edit to the question instead of as a real answer.  Should any action be taken in such a case? The obvious solution is to copy the edit into a real answer. But is this the right solution? In this case, the answer is a little hidden and there are no other answers, so it appears on the unanswered list.     Related:


Let $ S=\{A=[a_{ij}] : AB=BA \, \forall B \in M_{n×n} \},$ then $\text{dim}(S)$ equals to?

Let $p$ be a prime number. Let $M$ denote the ring of $2 \times 2$ matrices over the field $F$ of $p$ elements. For $A \in M$, let $C(A)$ denote the set of those matrices $B \in M$ such that $AB = BA$. What are the possible values of the dimension of $C(A)$ over $F$ for $A \in M$?  What I know is this: Given a square $n \times n$ matrix $A$ over a field $F$, it is always true that $A$ commutes with any $B=p(A)$, where $p(x)$ is a polynomial with coefficients in $F$. Now, because of the theorem of Cayley-Hamilton, the matrix $A$ is root of its  characteristic polynomial (which has degree $n$), so that means that every power of $A$ larger than $n-1$ can be written as a linear combination of powers up to $n-1$. For, our case, it means that: $C(A)=B=p_0I+p_1A$, where $p_0,p_1 \in F$.  So, that means $ 2\le \dim(B)\le 4$ (cases where $p_0=0$ and $p_1=0$). Is this correct? But what about $p$ prime - what it has to do with anything?


Let $k$ be a field of characteristic zero, $x,y$ commuting variables over $k$.  Question 1: Is it possible to characterize all ideals of $k[y,y^{-1}]$ and of $k[x,y,y^{-1}]$?  I guess that the answer to $k[y,y^{-1}]$ is simpler than the answer to $k[x,y,y^{-1}]$?  Question 2: Is it possible to characterize all maximal ideals of $k[y,y^{-1}]$ and of $k[x,y,y^{-1}]$?  Example: (1) $I= \langle \frac{x}{y},x \rangle= \langle x \rangle$ is maximal in $k[x,y,y^{-1}]$? (2) $J= \langle x,y \rangle$ is not maximal in $k[x,y,y^{-1}]$, since $1=y^{-1}y \in \langle x,y \rangle$, so $J=k[x,y,y^{-1}]$. Thank you very much!

Suppose that $k$ is an algebraically closed field. Then what do the prime ideals in the polynomial ring $k[x,y]$ look like?   As far as I know, the maximal ideals of $k[x,y]$ are of the form $(x-a,y-b)$ where $a,b\in k$. What can we say about the prime ideals? Are there similar results? And what about $k[x,y,z], k[x,y,z,w]$ and so on. Would someone be kind enough to give me some hints or referrence on this topic? Thank you very much!


I'm looking to texture something like this..Can I find these online or do I have to custom make them?

I'd like to know how this text gets adapted onto these 3D models. Could it be a PNG  which gets mapped. Or is this text pre planned how it would be layout onto the model? what's the method involved in this technique? Would the text layout need to be the same ratio done with a graphic editor like Photoshop or Illustrator? and have the mesh modelled in the same metric unit so the text can later fall correctly in place? All information is appreciated, unfortunately my college instructors are really lame in giving information....  Thank you.


Eigenvalue of triangular matrix are elements in diagonal.  Now, consider the following matrix with eigenvalue $-5$ and $4$: $$\begin{bmatrix}        -4 & 2 \\         4 & 3 \\         \end{bmatrix}$$ Now if I do row operation $R_2\to R_2-(-R_1)$ and convert above matrix to following $$\begin{bmatrix}        -4 & 2 \\         0 & 5 \\         \end{bmatrix}$$ The eigenvalue of this is $-4$, $5$  First one is correct, what is wrong with the second one?

I know that elementary row operations may change the eigenvalues of a matrix, but if these operations don't change the determinant, why should change the eigenvalues??  Thanks


Many questions have been asked about specific bugs and problems with global hotkeys, media keys, etc. especially in Ubuntu 14.04. I'm still having difficulty troubleshooting them though, so I wanted to clarify some basic background information about how they work.   Which general process(es) or packages are involved in detecting and/or responding to global hotkeys / shortcuts?  For a regular Ubuntu 14.04 installation, is this built in to Unity? (Honestly I'm a bit confused about the relation between Gnome and Unity, but it seems like Gnome is somehow still involved?) Aside from the "Keyboard" dialogue under "System Settings", are there other settings or configuration files that effect them?

Much as I like Unity and Gnome, getting global keyboard shortcuts and mouse clicks "right" is a source of continual frustration.  We have:   The "settings" dialogs for keyboard and mouse The ccsm tool with chainsaw-like ability to shred your system Unity tweaks (another obscure application) gconf-editor Kernel configuration to access consoles through Ctrl-Alt-Fx I don't know what else.   Recently, I tried to re-assign Super-L to lower a window rather than lock the screen for my 14.04 setup.  We already have Ctrl-Alt-L to lower the screen anyway, I don't need a second shortcut.  But after trying several tools to re-assign the key, I just gave up.  Several layers of assignment all implemented the "same" shortcut, but it isn't easy to figure out which one(s) are actually causing the system to respond as it is.  Without that information, it is hard to reconfigure.    This is a crazy-making setup that makes Linux harder to use than Windows for the average user: Too many arcane ways to set things up, and then a tangle of confusion trying to figure out why anything happens as it does.  How I long for the good old days of fvwm, the simple window manager that could assign any key or mouse click combination to do anything in any context, and the entire configuration was in a single .fvwmrc file! Using Fvwm as the only holder of system-wide shortcuts make life simple, but the multi-layer approach makes Microsoft's regedit seem simple!  It would be wonderful if there were a simple script that could search all the system and user-specific files for a keyword, and report where keypress and mouse-click events matching a pattern are configured.  Ideally, it would support a "universal" keypress and mouse-click description syntax or a GUI, and parse and match that in each of the many configuration files.  A bonus would be if the script could print out a suggestion how to manage the setting with the least potential for inadvertent misconfiguration (for example, helping the user avoid using ccsm when it isn't needed).


Assume that we have some count data $x_{1}, \dots, x_{n}$, which take values $\{1, \dots, m\}$ and we have some estimator of the probability mass function, $\hat{\mathbf{p}} = (\hat{p}_{1}, \dots, \hat{p}_{m})$. The Brier score originally defined as $$ BS = \frac{1}{n}\sum_{i=1}^{n}||\mathbf{I}_{i} - \hat{\mathbf{p}}||_{2}^{2} = \frac{1}{n}\sum_{i=1}^{n} \sum_{j=1}^{m}(I_{i,j} - \hat{p}_{j})^2, $$ where $\mathbf{I}_{i} = (0, \dots, 1, \dots, 0)$ is a vector in $\mathbb{R}^{m}$, with value $1$ is at the $t$-th position from the beginning of the vector, if $x_{i} = t$, for $t \in \{1, \dots, m\}$ and all $i=1,\dots, n$. Is it possible and does it improve something if we use $L_1$ distance instead of $L_2$? I mean the following modification: $$ \tilde{BS} = \frac{1}{n}\sum_{i=1}^{n}||\mathbf{I}_{i} - \hat{\mathbf{p}}||_{1} = \frac{1}{n}\sum_{i=1}^{n} \sum_{j=1}^{m}|I_{i,j} - \hat{p}_{j}|. $$

Yesterday's question  got me curious about probability scoring. The  $$\frac{1}{N}\sum\limits _{i=1}^{N}(\text{prediction}_i - \text{reference}_i)^2$$ is a mean squared error measure. Does the analogous mean absolute error performance measure $$\frac{1}{N}\sum\limits _{i=1}^{N}|\text{prediction}_i - \text{reference}_i|$$ have a name, too?


I've been aware about the difference of wp_query and query_posts. I just want to know what impact does both query methods to the performance of the page? Which query method makes the page load quicker or slower?

It seems like half the tutorials in the  and around the blogosphere use  and half use . They all do similar things, so when should I use one over the others?


My understanding of who has diamonds:   All moderators have diamonds on the sites they moderate and their respective meta Stack Exchange employees have diamonds      Right now, there are a lot of new diamond moderators across the network, with more being added in the near future.  Stack Exchange has also been doing a lot of hiring lately, which means there are a lot of newish ex officio diamond moderators as well.    I think it would be helpful if there was a way to differentiate between moderators and employees across the SE sites.   A couple of examples of where it would have been helpful:   On betas, right after opening: users see people with diamonds and wonder where these moderators came from—it would be clearer if they were easily identified as employees. On MSO, when (for instance) someone responds to a feature request. It's useful to know if that response is from, say, the programmer who's currently working on that exact code versus a volunteer mod who has an opinion that something is/isn't/will never happen.     Suggested solution: Give employees a different symbol.     Possiblilities:      ♢   ❖   ◇   ◆   ▰   ∆   ∇   ⍚   ␎   ◈   ♠   ♣   ♥        Suggested but unusable:      ⧗   ⧱   ⸭   ⟐   ⧓   ⧗   ⧫   ⧱   ⧎   ⎆   ⎏   ⎐   ⎑   ⎒   ⬙   ⬘   ⬗   ⬖       Misc thoughts:   The super-coolest kids on the block would be those with both symbols. Someone would need to verify that there are no users on any site whose user name ends with the new symbol (and keep people from changing their user name to have it). While these symbols are all valid Unicode characters, some of them might not be visible on all browsers (IE, I'm looking at you…). Those that aren't visible on all supported browsers should be ruled out.

Given that not all employees have a diamond:     All Stack Overflow employees aren't given a moderator diamond; the Community team has tightened up internal policies regarding who gets one and who doesn't. [...] —      can we have some visual indication that they are an employee?  This was  back in 2011, but declined. However, the situation appears to have changed now with fewer employees being given a diamond.  That way when they post on a meta site we know that it's somewhat "official".  Failing that please ensure that everyone includes the fact they're an employee in their profile given that  to add employee to their profile pages was also declined.


I sent a postcard 2 weeks ago from Germany to Beijing. I bought 2 x 0.45€stamps, and put it in a Deutsche Post box.   Is there any way to know how long does it take for the postcard to arrive the destination? I couldn't find any information online.

Three and a half weeks ago I was in Poland and I sent a letter (actually, a postcard in an envelope) home (in Russia) to my family, but the letter still hasn't been delivered. I know that parcels from eBay and AliExpress are usually delivered in 30 days or even more, but that's a parcel from China - while in my case, it's a letter.  Is it common to wait for a letter for so long considering not that large distance between countries? Is there any way to know about the status of my letter if I don't have any receipts left?  By the way, there was a blue sticker on the envelope saying "priority" - so, I guess, it has to go faster than usual?


I was recently asked a question by my colleague: Can we use multiple LINEAR regression for a binary classification problem?  Will the regression model be equally good as a classification model or it is not advisable at all to use multiple regression for a classification problem.  The dependent variable(y) is 0 or 1 and the model used is multiple linear regression. Is it correct to do so?

Given a binary classification problem, is there any inherent difference (or advantage) to using a classifier (say a logistic regression) and a regression, where the classes are denoted by 0 and 1 (or any two numbers)? Further, say, after running the regression, one can learn to optimize the 'cutoff' point (maybe not 0.5 in this example, but it turns out better to cut at 0.45).


I am trying to send email from PHP using SMTP but every time I am getting emails in my spam. I searched on google and got some solution but still I am getting email in spam. Would you help me in this?  //$mail->isSMTP();                                      // Set mailer to use SMTP  $mail->Host = 'smtp.gmail.com';                       // Specify main and backup server $mail->SMTPAuth = true;                               // Enable SMTP authentication $mail->Username = 'abc@gmail.com';                   // SMTP username $mail->Password = '***';               // SMTP password $mail->SMTPSecure = 'tls';         // Enable encryption,'ssl' also accepted $mail->Port = 587;                                    //Set the SMTP port number - 587 for authenticated TLS $mail->setFrom('abc@gmail.com', 'admin');     //Set who the message is to be sent from $mail->addReplyTo('abc@gmail.co', 'First Last');  //Set an alternative reply-to address $mail->addAddress($to, 'user');  // Add a recipient $mail->isHTML(true);                                  // Set email format to HTML $mail->Subject = 'Hello'; $mail->Body    = "  <title>HTML email</title>   Create your password here  "; if(!$mail->send()) {    echo 'Message could not be sent.';    echo 'Mailer Error: ' . $mail->ErrorInfo;    exit; }

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


I have a Nvidia Geforce GTX 770 and use 2 BENQ 1080p monitors. I would like to mirror my other screen (Television 1080p) with one of my BENQ screens.  I have read something about saving the config file and put some code into it. First I would like to know something about the config saving and if it's safe for my GPU.  Also, how do I save the config because I have already got the mirroring done but it doesn't save. I had read in the Terms that it's normal but possible??? Please could someone explain that to me?

Is it possible to have 2 extended monitors and get the third being a mirror of one of the two extended?   I'm pretty sure it's not possible through the interface but it may be possible through commands or configuration file.  If it's seems weird for you, here is my setup :    2 monitors, pretty classic working with dual monitor 1 big TV that I use as a projector to show things off to people (on meetings for example)


This is a little confusing to see and explain. Let's take . Someone posted a link to an answer in the Tavern, and that link got oneboxed:    This works fine. There's nothing amiss here. Then that chat message was, in turn, , and it got oneboxed, and so we also saw that original oneboxed link to the answer. At this point though, the link inside goofs out:    A mysterious and undesirable "chat.meta.stackexchange.com//" has appeared. As you can imagine, , so it's not some clever forwarding scheme that's been implemented. ( does not appear to exacerbate the problem.) Probably that undesirable portion of the URL should be thanked for its eagerness to help, and then disinvited from future links.

So if you try to onebox a onebox from a different chat server, . Basically, it generates this URL:    Now, obviously that isn't right. I've also tested this , and I'm assuming it's broken on chat.SO too. Can this be fixed?


I'd like to build a list of all the people who email me but can't figure out a way of doing it.  Tools such as Xobni offer a list, but it is not possible to select the data from the 'analytics'.  How can I harvest this data?  EDIT: Needs to be recursive from root inbox folder

I've got to send a bulk email out to a bunch of people in reply to emails they sent me. I've got all the original emails stored in a single outlook folder. I want to extract all of the reply addresses from the emails in that folder so I can send an email to all of them.  The article  shows you how to export the FROM address of these emails, however a large amount of them came from a web service that sends emails 'on behalf of' the person I'm trying to mail to. So I need the reply-to address, and the export wizard doesn't do that.  Does anyone have a tip on how to do this? This is Outlook 2007 on Exchange 2010.


I have started answering on Stack Overflow two months ago, and I'm giving up a lot of my free time.  What benefit I will get on a personal and professional level by answering on Stack Overflow?  Does it at least improve my knowledge?

I want that too - motivation to answer programming-related questions. What is yours?


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

In Texas Hold'em poker, there are some cases where a particular card, often called kicker, acts as a tiebreaker between players to determine who wins the pot, or if the pot has to be shared.  For some combinations such as three or four of a kind, there is no doubt: the kicker is the 5th card of the chosen combination, and determines the winner.  Example     Alice has 7 and 10   Bob has 7 and K   On the board are 7, 7, 2, 3, 4   In that case, both have a three of a kind. But because Bob has a king and Alice only a 10, he wins.  Most of poker websites explaining the rules clearly mention the role of the kicker applying to three of a kind and double pairs. But much fewer say something about colors, straights and full houses, and I found many contradicting answers. I also asked the question to some used online poker players and they also gave me contradicting answers.  I have tried to search for official tournament rules, but most of them only explain what happens with bad behaviors, bad deals, incorrect or confusing betting, showing cards when you shouldn't, acting when it's not your turn, etc. without mentioning subtleties about combinations at all.  To simplify my question, I will take three examples; I think it's better to start with examples before getting to the general answer if one exists. So, what's happening in the following 3 examples? Could you give a more generalized answer?  Example 1 - Flushes     Alice has 2♣ and 3♣   Bob has 4♣ and 5♣   On the board are 6♣, 8♣, 10♣, 2♥, 5♦   Contradicting answer 1: it's a tie, because the highest card included in the flush is the 10, which everybody chooses to include in their 5 showdown cards. Contradicting answer 2: Bob wins, because he has the greatest private card that is part of the flush  Example 2 - Straight     Alice has 6 and K   Bob has 6 and J   On the board are 4, 5, 7, 8, 10   Contradicting answer 1: it's a tie, because the greatest card in the straight is the 8 for both Alice and Bob Contradicting answer 2: Alice wins, because she owns an extra king, compared to the jack of Bob  Example 3 - Full house     Alice has 3 and 7   Bob has 3 and 6   On the board are 3, 3, 2, 2, 5   Contradicting answer 1: it's a tie, because one is supposed to choose only five cards to make a combination, and a full house is already five cards. There couldn't be any kicker, and thus their showdowns are strictly equals. Contradicting answer 2: Alice wins because of her extra 7, compared to the 6 of Bob  Thank you very much for your answers.  Note: I'm unable to post next to you, so I edit my own post; strange not be able to answer to an answer.  Ok, So if I summarize what you are saying :   In the flush case, Bob wins because at some point, their hand differs. Technically, I can continue comparing the highest private card to decide who wins. I had it correct. In the straight case, if the highest card of the straight is public, then it's technically always a tie, no matter what the players had as second private card (asuming that only one of the two cards was part of the straight). In a full house if both players have the same triplet and the same pair, it's always a tie, no matter what the players had as second private card (assuming again that only one of the two was part of the full house).   Please confirm me that what I summarized is correct.  Thank you for your answer.


How the cost function of logistic regression given below is derived ?  Here Sigmoid function is used for logistic regression. After heavy search on internet i have come up here to put on my question , no other question on this portal talks about it so please don't mark it as duplicate.

There is a statement that maximizing the likelihood is equivalent to minimizing the cross-entropy.  Are there any proof for this statement?


Let $f(x)\in \mathbb{Q}[x]$ be a polynomial of degree $n>0$. Let $p_1, p_2, \dots ,p_{n+1}$ be distinct prime numbers. Show that there exists a non-zero polynomial $g(x)\in \mathbb{Q}[x]$ such that $fg=\sum_{i=1}^{n+1} c_ix^{p_i}$ with every $c_i\in \mathbb{Q}$.

Let $f \in \mathbb{Q}$ be a polynomial of degree $n>0$. Let $p_1,p_2,p_3..p_{n+1}$ be distinct prime numbers. Show that there exists a non-zero polynomial $g \in \mathbb{Q}[X]$ such that $fg=\sum_{i=1}^{n+1}c_iX^{p_i} $ with $c_i \in \mathbb{Q}$.  If I want to find a polynomial then it must be of degree $p_{n+1}-n$. So I assumed a polynomial $g=\sum_{i=1}^{p_{n+1}-n}b_iX^{i}$.  Multiplying $f$ & $g$ and equating the non-prime power coefficents to $0$ where our variables are $b_i's$ (they are $p_{n+1}-n+1$ in number) and we have $p_{n+1}-n+1$ equations. One solution is all $b_i=0$ and in this case it is zero polynomial.   How do I proceed further? Is there another way to prove it?


Using bash command syntax:  echo "The*quick*brown*fox"|sed s/*/\\n/g  I get the desired output:  The quick brown fox   However in script:  IN_TXT="The*quick*brown*fox" OUT_TXT=$(echo $IN_TXT|sed s/*/\\n/g) echo $OUT_TXT   I get whitespaced: The quick brown fox  What am I doing wrong?

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


select * from Answers where AnswerName like '%No [DETAILS REQUIRED]%'   The above-given query does not return any results while there is an entry in the column "AnswerName " with the exact text as "No [DETAILS REQUIRED]"

I am trying to filter items with a stored procedure using like. The column is a varchar(15). The items I am trying to filter have square brackets in the name.  For example:  WC[R]S123456.  If I do a LIKE 'WC[R]S123456' it will not return anything.  I found some information on using the ESCAPE keyword with LIKE but I do not understand how to use it to treat the square brackets as a regular string.


When trying to install some applications via Ubuntu software centre I am getting the error:  cannot install libfreetype6:i386   So I tried to install it via terminal, and got this result:  bfalcon@lappy:~$ sudo apt-get install libfreetype6:i386 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: gnome-keyring : Depends: gcr (>= 3.4) but it is not going to be installed indicator-bluetooth : Depends: unity-control-center but it is not going to be installed or                                 gnome-control-center but it is not going to be installed or                             ubuntu-system-settings but it is not going to be installed                    Depends: gnome-bluetooth but it is not going to be installed or                             ubuntu-system-settings but it is not going to be installed indicator-network : Depends: unity8 (>= 8.00+14.10.20140806) but it is not going to be installed libfreetype6:i386 : Depends: libpng12-0:i386 (>= 1.2.13-4) but it is not going to be installed qtcontact5-galera : Depends: address-book-service (= 0.1.1+14.10.20140930-0ubuntu1) but it is not going to be installed signon-ui : Depends: signon-ui-x11 but it is not going to be installed or                   ubuntu-system-settings-online-accounts (>= 0.4) but it is not going to be installed  E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.   I have tried a searching around a bit, but haven't come up with any solutions.

I am not sure what caused this error, but here is what the whole error says, and also this is sitting as a notification, and preventing me from updating any software using Update Manager - Please provide some assistance or tell me how to figure out what to do to fix it.  Could not calculate the upgrade  An unresolvable problem occurred while calculating the upgrade.  Please report this bug against the 'update-manager' package and include the following error message: 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.'


I am level 10 in Pokemon GO and I caught two of the same Pokemon very recently, both of which can be evolved three times.   One Pokemon has a CP of 210 with a moveset of power (10,15). I also have another of the same Pokemon with CP 140 with a moveset of power (10,25).   I need to decide what to evolve. Some people tell me go with CP and the others tell me look at the "bar" (which I do not understand how I can derive implications on what to derive by looking at the Bar above the Pokemon's head because the bar is same for all of that type of pokemon except it is further down for the one with higher CP). Moreover, others tell me I need to evolve both first to see which one is better.   What should one consider before evolving and when should I use the power up button?

When activating the evolution for a caught Pokemon, it seems to amplify the Combat Power (CP). Thus it seems most beneficial to evolve your Pokemon with the highest CP, if you have multiple of the same kind.   But what I am not sure about is whether it makes an efficiency difference if you spend candies and dust to boost CP before evolving, to gain more from the amplification? Or is it more efficient to just evolve without spending, and then using the leftover candies afterwards, since they now give a bigger CP boost per candy?   I only tested with a Rattata so far, which gained +8 CP per candy before evolving, and +15 CP afterwards. I collected no numbers on the amplification efficiency though, and now ran out of materials for further testing.  Or maybe it is a balanced calculation and makes no difference at all? I would love to have some insight on that.    Some data I collected thus far: (GPC = CP gain per candy)  79 CP Weedle (GPC 6) evolved to: 84 CP Kakuna (GPC 6), evolved at 90 CP to: 297 CP Beedrill    Note: The max-CP "half circle" in the profile stayed filled roughly at the same relative position throughout the evolutions.


When I try to render an image operating in from the info menu, it will not make a still render, it seems to render the same still image over and over like an animation not stopping, it renders it then instantly start´s to render again. and it will not render it in the tmp on c: that it usually does, for some odd reason in cycles it render´s a still picture but in blender´s own render not !  i have set it to render from frame 1 to 1 but does not help . what could be a reason for this behavior ?

Every time I render an image and try to save it, it just disappears. How do you exactly save a render? I am using a mac.


I'm need to separate out this table as follows:    I've heard this may be possible using a CURSOR function? Can anyone help please?  Select id, tag from mytable

Using SQL Server, how do I split a string so I can access item x?  Take a string "Hello John Smith". How can I split the string by space and access the item at index 1 which should return "John"?


Why is it that in the plural spelling of many nouns (thief, leaf, life, knife, etc) with an ending consonant of 'f', the 'f' is replaced with a 'v' while other words such as 'chief' (chef, handkerchief) retain the 'f'?

The plural form of leaf is leaves, although according to  leafs is also correct. Dwarf can be pluralized as either dwarfs or dwarves. Conversely, the words roof and safe are pluralized as roofs and safes.  Is there any logic underpinning these variations? Is there a historical trend where words that were previously pluralized as -ves are now being increasingly pluralized as -fs?


We all have seen and know of Euclid’s proof by contradiction, but I’m wondering if there is such thing as a direct proof? Also, the theorem isn’t posed as an “if-then” statement, so I can not even imagine how an alternative proof would be structured.

This question relates to a discussion on . Euclid's proof of the infinitude of primes is an indirect proof (a.k.a. proof by contradiction, reductio ad absurdum, modus tollens). My understanding is that Intuitionists reject such proofs because they rely on the Law of the Excluded Middle, which they don't accept. Does there exist a direct and constructive proof of the infinitude of primes?


I don´t know if the canon specifies whether a muggle can or can´t enter Diagon Alley , someone asked if Diagon Alley can be accessed through the sky, and apparently it´s possible.   What would happen then if a muggle entered Diagon Alley?

Courtesy of , I found the a bit of  (currently un-cited):  The Leaky Cauldron The pub serves as a way of entering into Diagon Alley from the Muggle world for Muggle-borns and their parents (both of whom, until the first letter from Hogwarts, have no magical knowledge or means of entering). The rear of The Leaky Cauldron opens onto a chilly little courtyard, in which a particular brick must be tapped three times to open a path to Diagon Alley.  But from what I can see, Muggleborns and their parents wouldn't be able to enter from Leaky Cauldron, because - based on what I can tell - that requires one to use a wand:  He {{Hagrid}} tapped the wall three times with the point of his umbrella. The brick he had touched quivered – it wriggled – in the middle, a small hole appeared – it grew wider and wider – a second later they were facing an archway large enough even for Hagrid, an archway on to a cobbled street which twisted and turned out of sight.  Is there some canon information confirming the Wikipedia assertion that Muggle parents and not-yet-wand-owning Muggleborns could enter Diagon Alley from the courtyard behind Leaky Cauldron?


The sequence of events were the following:   I answered a . At the time of posting, I noticed a comment directing to a . Rather than keeping my answer under the (newly posted) duplicate, I deleted it and posted it under the duplicate source.   After a while, I noticed my  came up as an automated flag under the . This doesn't seem appropriate since, well, I'm biased and all...    Related:

I was able to see , which has been flagged as not an answer, while going through the review tools. Is this supposed to be possible, or is this a glitch? If it's meant to be possible - what's the point of it? Surely being the OP I'm going to be biased and most likely wish to choose to disagree with the flags...    update:   I've been able to select "flag or disagree" and then say "I disagree"...   So, would there be some gaming involved here, if I was to agree with the flag, then delete my own answer (would I get a helpful flag for that), then undelete it (still leave my answer there)...?  However, as expected, it now appears to have disappeared from the queue as expected (or at least I assume it has, as it hasn't appeared in the 50 from multiple page reloads anyway...)  And here it is in flag history:


I have a doubt regarding the usage of article in the sentence given in the title.

The Punjab is a rich state.   Is it correct to use the before Punjab?


The site selector, inbox, and achievements dropdown are all part of a group; when I open one, I can mouse over another to open it. However, the winter bash dropdown is not included. I cannot switch between the original dropdowns and the winter bash dropdown just by hovering over their respective buttons.  Not only does this severely degrade my experience, but the poor dropdown feels excluded. Can we promote inclusivity by adding the winter bash dropdown to the code that lets us mouseover to switch?

If you click on the Stack Exchange menu or the inbox menu or the achievements/reputation menu, you can then move the mouse between those three menus without any additional clicks.  This behaviour does not appear to be applying to the Winterbash menu (or the "help" menu for that matter, but that's on the other side of the bar).  Could we get this sorted, since otherwise the behaviour is a little inconsistent, with extra clicking on a menu bar where in all other circumstances clicking would close the menu!


often i forget i'm not in edit mode and i will press 1, 2, or 3. If you're in object mode it will hide all the collections i'm working with. Alt+H doesn't seem to unhide them and i have to manually make them visible again in the outliner. Is there another efficient way to work to avoid this problem?

I was creating a project in blender 2.8. I unintentionally pressed the 1 button, and now only one of the objects (each object is inside a collection) appears on the screen. All other objects are hidden.  How can I see the collections again? I don't want to loose all the work of the previous hours.  Besides, something as basic as that should have documentation. One hour of search in google, stackoverflow, and the blender 2.8 documentation for terms like "unhide collections" or "show all collections" or "unhide objects" do not return any working solution. This was a basic feature of blender 2.7. What happened?  Obs: Alt+H does nothing.


Students in an undergraduate course often have no choice of a textbook for the subject and are expected to buy the book recommended by the instructor. The expectations can be advisory or mandatory. Given the degree of control that an instructor has over their undergraduate students, especially freshmen and sophomores, is it ethical to use a textbook authored by the instructor in an undergraduate course? Does such requirement not constitute a conflict of interest?  P.S. I understand that practically this is done times and again, but I would like to sense the general feelings.

This question was suggested to me by  which asked about the practicalities, but attracted many comments about the ethics.  So this question is to ask about the ethics directly.  Suppose I have written and published a textbook, and I want to use it as the text for a course I am teaching.  I receive royalties from each copy of my book that is sold, so if my students are required to buy my textbook for the course, I will make some money.  Is it ethical to do so?  Well-reasoned opinions would be useful answers, but even more useful would be pointers to institutional policies, professional codes of ethics, etc, that address this issue.  Of course, there are many ways to avoid profiting from the sale of my book to my students.  If my contract with my publisher allows it, I could distribute PDFs to my students, or have the university bookstore print out copies and sell them at cost.  Another approach I've heard of is to compute how much I earn in royalties on each copy, and refund that amount from my pocket to each student who buys a copy.  Or, use my royalty earnings to buy pizza for the class.  Certainly these are nice gestures, but I would like opinions on whether they are ethically required.  Edit: To address some questions that have arisen in the comments:   This question is hypothetical.  I haven't published any textbooks myself and have no immediate plans to do so.  In any case, my personal preference would be to make the book available to students for free, if at all possible.  So I've phrased this question in the first person for rhetorical convenience only. I had intended the question to be only about the potential financial conflict of interest that could arise if I make money by assigning my own book.  Some of the answers feel that it is improper for me to assign my own textbook at all, whether I make money or not, but I don't think this point of view is prevalent within the academic community.  If it happens that my book (as a pithy but now-deleted comment put it) "blows", I think most would agree that my decision to assign it is pedagogically unfortunate, but not unethical.   I don't literally mean that students would be required to buy the book, only that they'd be expected to have it.  I might assign readings or homework problems from the book, so that the student needs access to the book in order to do them, but they could certainly achieve this by getting a used copy or borrowing from a friend.  But probably most students would buy new copies anyway, since that is the most convenient way.


I'm often wondering, whether gaming on Linux is better or gaming on Windows is better?   I often watch most youtubers says "Gaming on Linux is Sucks, Windows is better.", but somewhere I see some youtubers says "Gaming on Linux is better."  Which is better for gaming Linux or Windows?

What are the pros/cons switching from Windows 7/8 to Ubuntu?  I mainly develop software and play games.  I obviously don't play games on my laptop that's why I give Ubuntu a try. But the whole OS looks great and I recently discovered PlayOnLinux.  How big is the performance hit from Windows games?  What if the game supports DX11 and has tessellation, does PlayOnLinux translate DX11 to OpenGL?


1.Have you phoned your sister?      2.Did you phone your sister?   What is the difference between the above two sentences? (Do they sound similar?)

I already knew that we use the present perfect for an action in the past with a result now. Consider the following questions:   "I'm looking for Paula. Have you seen her?" "I'm looking for Paula. Did you see her?"   Is there any difference between these two questions for this specific action (verb)? What is the result of "seeing" action which can't be represented by simple past?


I have a the following problem with my laptop. Suddenly, one morning I went to start it and when it gets to the logon screen, the screen just shows random horizontal lines, totally indecipherable. But I can still log in, and shut it down, by just using key combinations, I assumed it was a hardware problem, but wait... ... I can still see the BIOS screen fine, I can still get to recovery mode, that is also fine. I even can boot into a recovery USB (Hirens), screen still totally fine. So I assume now it is not a hardware problem now but windows. I tried with an external monitor, no change. Tried rolling back windows to earlier version, but only managed to uninstall last "quality update" no joy. Then I tried to reset windows, twice, both times, screen works fine, but then at some point during install it just prints the weird lines on the screen again. I tried removing one ram stick at a time, either way I still get the same problem when I restart. Other info:  the screen garbage looks like the horizontal lines are out of sync, I can see the mouse moving, but it spread out in tiny lines all over the screen. Normally I actually only get black screen, the only way to see the garbage is to plug in the external monitor cable, otherwise the laptop screen stays black. Nothing ever shows on the external. Acer aspire E 15 (E 571 32nu)  Next things I am going to try are: installing ubuntu or similar, if that works then I will stick with that, really I only need this laptop for Teams, VPN and remote desktop. OR Maybe the windows reset was the wrong method, and it is just reinstalling the same broken/incompatible drivers. Could someone point me in the direction of a how-to, that lets me install earlier version of windows (without losing my licence).

Every time Windows 10 runs updates (which I see no way to control), it updates my graphics driver.  I like the old one because it is faster.  So, I have to reinstall it.  This is getting to be a pain.  Is there any way to stop Windows 10 from updating it again?


Can  kill a creature with protection from black? My friend says it can't because protection gives it complete defense from black.

Example 1) Let's say I have some random creature with protection from white, and my opponent plays , a white card with the effect "Destroy all creatures." Can my creature with protection from white be destroyed by a white card that isn't actually targeting it specifically?  Example 2) I was playing a match with a friend where I had  on the field against his 3 zombies. Is he able to declare his zombies as blockers even though Elite Inquisitor has "protection" from zombies?  If he can declare them as blockers, does protection mean that no damage is dealt by the zombies to  Elite Inquisitor?


I'm pretty new to GIS, but hope I'm moving in the right direction.  I have a layer of the county map of LA, which is divided into communities and a layer of the building coverage of the county.  The building layer contains a large amount of data, so it takes a long time to render making visual analysis difficult.  It seems to me that the way to deal with this is to break the building layer into 353 much smaller layers based on community (there are 353 communities in the attribute table).  In that way I'm thinking that if a have a community_buildings layer for each community I can make them visible as needed without bogging down ArcMap.    It seems to me that what I would want to do is a spatial join on the communities layer to the buildings layer and then break that result into a 353 different layer based on communities, but I don't know how to accomplish the second part which is splitting one layer into multiple layers based on an attribute.    Below is the graphic of the data sets to get a feel for what I'm talking about.  Hopefully I'm moving in the right direction, but if I'm not can someone reorient me?

I have a feature class with over 2,000 features, and I need to make them all individual feature classes based on a field.   Is there a way to do this?


Can anyone please guide me to number the reactions separately from equation numbering, while using chemformula package.

I want to cross-refer a chemical reaction and to write chemical reactions I am using  \usepackage{chemformula}   to cite I am using  \usepackage{cleveref}   I want to cross-refer reactions using \cref{label}. How can I do it?  MWE  \documentclass[a4paper,oneside,12pt,openright]{book} \usepackage{amsmath,amssymb} %for typing the mathematical equations and symbols \usepackage[utf8]{inputenc} % input encoding \usepackage{csquotes} %for using quotes command:\hyphenquote \usepackage[T1]{fontenc} % font encoding \usepackage{etoolbox,ragged2e,siunitx,mathtools} \usepackage{indentfirst} % paragraphs \usepackage[paper=a4paper,left=22mm, top=22mm, right=15mm, bottom=22mm]{geometry} %paper geometry  total={170mm, 257mm} \usepackage{graphicx} %for figure \usepackage{array} % for matrices \usepackage{pgfplots} % for plots \usepackage{caption} %names of figures and tables \captionsetup[figure]{list=yes} \captionsetup[table]{format=plain,labelformat=simple,labelsep=period}% \usepackage[list=true,listformat=simple]{subcaption} \pgfplotsset{width=10cm, compat=1.9} \usepackage{color} %colors in document \usepackage{xcolor}  \usepackage[english]{babel}% base language and spacing \frenchspacing \renewcommand{\baselinestretch}{1.2} \usepackage{mathrsfs} \usepackage{chemformula} \usepackage{cleveref} \begin{document} I want to cross refer following reaction  \ch{2H2+ O2 -> 2H2O}  As per above \cref{label} water is formed.  \end{document}


I downloaded Ubuntu 16.04.1 LTS today and I tried to dual boot it with window 7, but when I start installing Ubuntu there is no option to install Ubuntu alongside window 7.  I have 119 gb allocated. How can I install as dual boot?

Whenever I startup from the LinuxLive USB, and try to install Ubuntu 12.04, it only gives me two options instead of the usual 3 or 4. My options are "Replace Windows 7 with Ubuntu" and "Something Else". Whenever I go into "Something else", it looks extremely confusing. How do I install it side-by-side while using the "Something else" section? These are my partitions.   /dev/sda /dev/sda1 ntfs (104Mb, System Required Partition) /dev/sda2 ntfs (1000097Mb, Windows 7 Partition)   Or should I try reinstalling my installer on a CD rather than USB and maybe then it will have the "Install alongside" function?


My ubuntu 18.04 is broken due to an issue     Now I am planning to reinstall ubuntu from USB. I have booted from live USB and was able to backup my home folder by mounting the drive and copying it to an external hard drive.   My question is can I somehow also backup my installed packages and settings from the live USB or can I reinstall ubuntu without overwriting my data or at the very least can I somehow get a list of my installed packages and libraries?

If I want to make a backup of everything I have done since the fresh install of Ubuntu, what are the possible options? What all should I backup? I want to get all the settings that I changed, all the packages I installed, etc.


I reformatted an old desktop of mine to boot Ubuntu 13.04, which I will be using as a mini-server to host VPSes. It will become a headless server that I will be putting in my closet when I finish configuring it. I will simply use VNC software to connect to it when need be.  The desktop does not have a built-in WiFi adapter, so I purchased a Linksys AE2500 Dual-Band Wireless-N USB Adapter. I bought this back when the desktop ran Windows 7. I was wondering where I should start to find any drivers, or anything really that will allow me to get this adapter working on Ubuntu. Note there is no internet connection to the desktop, and I can't connect it with an Ethernet cable. I do have another laptop with internet if I need to download and transfer any files via flash drives.  I am extremely inexperienced with Linux and this project is one way I'm trying to learn about it.

I have a Linksys AE2500 made by Cisco and was wondering if it will work or run with no "hiccups".


What happens if a Linux, let’s say Arch Linux or Debian, is installed with no swap partition or swap file. Then, when running the OS while almost out of RAM, the user opens a new application. Considering that this new application needs more RAM memory than what’s needed, what will happen?  What part of the operating system handles RAM management operations, and can I configure it to behave differently?

I was running a shell script with commands to run several memory-intensive programs (2-5 GB) back-to-back.  When I went back to check on the progress of my script I was surprised to discover that some of my processes were Killed, as my terminal reported to me. Several programs had already successively completed before the programs that were later Killed started, but all the programs afterwards failed in a segmentation fault (which may or may not have been due to a bug in my code, keep reading).  I looked at the usage history of the particular cluster I was using and saw that someone started running several memory-intensive processes at the same time and in doing so exhausted the real memory (and possibly even the swap space) available to the cluster.  As best as I can figure, these memory-intensive processes started running about the same time I started having problems with my programs.  Is it possible that Linux killed my programs once it started running out of memory?  And is it possible that the segmentation faults I got later on were due to the lack of memory available to run my programs (instead of a bug in my code)?


I want to replace all the 4 dots(....) in my String with new line (\n) by using regex in the replace method.  orange...apple....banana --> should be pirnted as:  orange apple banana   I have tried the following:  get : function(value) {  value = value.replace(/(...)/g, '\n');  return value; }   and   value.replace(/(\r\n|\n)/g, '....')    --> should retrieve 'orange....apple....banana'

I am tired of always trying to guess, if I should escape special characters like '()[]{}|' etc. when using many implementations of regexps.  It is different with, for example, Python, sed, grep, awk, Perl, rename, Apache, find and so on. Is there any rule set which tells when I should, and when I should not, escape special characters? Does it depend on the regexp type, like PCRE, POSIX or extended regexps?


Evaluate 1/(1+2) + 1/(1+2+3) + 1/(1+2+3+4)... + 1/(1+2+3+4...+100)  This is a math competition question that I have tried solving for a long time as I can't use a calculator. What is the simplest way of solving this question without using a calculator?

How do I simplify the following series $$1 + \frac{1}{1+2}+ \frac{1}{1+2+3}+ \frac{1}{1+2+3+4} + \frac{1}{1+2+3+4+5} + \cdot\cdot\cdot + \frac{1}{1+2+3+\cdot\cdot\cdot+n}$$  From what I see, each term is the inverse of the sum of $n$ natural numbers. Assuming there are $N$ terms in the given series, $$a_N = \frac{1}{\sum\limits_{n = 1}^{N} n} = \frac{2}{n(n+1)}$$ $$\Rightarrow \sum\limits_{n=1}^{N} a_N = \sum\limits_{n=1}^{N} \frac{2}{n(n+1)}$$ ... and I'm stuck.  I've never actually done this kind of problem before (am new to sequences & series).  So, a clear and detailed explanation of how to go about it would be most appreciated.  PS- I do not know how to do a telescoping series!!


When some people pronounce the word "getting", it sounds to me like they're saying something like "get'n". Is that some kind of dialect?

Further to the question I posted today about the meaning of the expression, “treat somebody pretty ugly,” which appeared in New York Times’ article (September 17) titled “Rick Perry, Uber Texan,” I wonder about implications of the term, g-dropping, a question I earlier put aside. The term g-dropping appears at the beginning of the article:  YOU think of Rick Perry, you think of Texas. And more Texas. Perry the cowboy coyote-killer, the lord of the Texas job-creation machine, the g-dropping glad-hander with a “howdy” for every stranger in the room. He barely exists in the national mind outside of the Texas connection.  I understand g-dropping means the habit of dropping g in pronouncing –ing.  However, what does this trait represent?  That is, what sort of people  habitually drop g's? I've heard Texans drawl. Does g-dropping represent a particular talking style, character of speakers, educational background, regionality, or something else?  If not, why did the author insert the term, g-dropping, in describing the character of a Presidential candidate?


This is an exercise from Matsumura 2.4  $A$ is a non-trivial ring. If $A^n\cong A^m$, then $n=m$; prove this by reducing to the case of a field. (Note that there are counter-examples to this for non-commutative rings.)  What is the counter example and reason that I do not expect rank being well defined for the noncommutative case? Does it have anything to do with left ideal and right ideal might not be the same? So one may have one rank through left maximal ideal and another rank through the right maximal ideal?

I'm aware that over a commutative ring, two free finitely generated modules of finite rank are isomorphic if and only if they have the same rank.   I'm trying to understand a curious example of why this does not hold over a noncommutative ring.      Let's take $M=\oplus_{i\in\omega}\mathbb{Z}$. Then let $R=\text{End}(M)$, which is not commutative. Then $R\cong R^2$ as left $R$-modules.   It seems like one could possibly make a basis of $R$ using only endomorphisms which act on the even or odd coordinates of elements of $M$, which might suggest such an isomorphism. Is there a clear proof of why $R\cong R^2$?


about Person of Interest already asked why everyone else but Root called the Machine "she" rather than "it". But in this question I'm more concerned about why Root actually calls it a "she", rather than a "he". I am asking about Root because she started calling it "She" and others have simply followed the trend, as indicated by the answers to the previous question.  I understand that Root considers the Machine an intelligent being, even superior to humans. Later, she says she has an intimate relationship with the Machine. So, that helps me understand why she doesn't refer to it as "IT". Still why simply not refer to it as "He"?

On Person of Interest, most people on Team Machine refer to it as "she". To me, that's sort of clear for Root, not so clear for Finch and even less clear for others. Why do they do that?  P.S. I don't recall perfectly, but Samaritan is mostly called "it" and not "he". But should it be a "he" in contrast to the Machine?


Let $M$ be a manifold , and $\pi_1(M)=\mathbb{Z}$. then can we say, the double covering of $M$ exists and is unique?

Is there any reference or simple proof to show that the group $\frac{\mathbb{C}\times SL(n,\mathbb{C})}{2\mathbb{Z}}$ is double cover of $GL(n,\mathbb{C})$.


Let $A ∈ M_n$. If $A^2 = I$,    show that   $$\operatorname{rank} (A + I) + \operatorname{rank} (A − I) = n$$   I know that $x^2=1$, $x^2-1=0$, and so $(x-1)(x+1)=0$. So  depending on this formula, how I can complete my solution to this question   or how can I use  anther methods to solve it. Any one could help me please?

If $A^2 = I$ where $A$ is an $n\times n$ matrix, then why is $\operatorname{rank} (A+I) + \operatorname{rank} (A-I) =n$.   I am not sure why this seems to be true.


The variance of a sample can be defined as $$s^2 = \frac{1}{2}\frac{1}{n(n-1)}\sum_{i}\sum_{j\ne i}\left(x_i - x_j\right)^2$$  Apart from the factor of $1/2$, this can be paraphrased verbally as     The variance is the average of the squared distances between pairs of distinct data points   Mathematically, this is equivalent to the "usual" definition of variance, $s^2 = \frac{1}{n-1}\sum \left(x_i -\bar{x} \right)^2$.  Conceptually, however, it seems (to me) quite different, in two respects:   This definition makes no reference to the mean value $\bar{x}$; we are not measuring how far apart points are from the mean, but rather how far away points are from one another. The factor of $n-1$ in the denominator -- which is well-known to be a source of confusion for students (see, e.g., ) -- appears naturally because there are $n(n-1)$ ordered pairs of distinct data points $(x_i, x_j), i\ne j$.  No need for either hand-waving justifications about "cushioning" the sample variance, or for complicated calculations of estimator bias.   Again, just to be clear, I understand why the standard definition of $s^2$ includes a denominator of $n-1$, and I understand that the double-sum definition above is mathematically equivalent to the standard definition.  What I would like to know:  Are there contexts (pedagogical or otherwise) in which the alternate definition of variance (as a double-sum over pairs of data points) is more commonly referred to?  Are there any textbooks, for example, that take this as the primary definition?

I was asked today in class why you divide the sum of square error by $n-1$ instead of with $n$, when calculating the standard deviation.  I said I am not going to answer it in class (since I didn't wanna go into unbiased estimators), but later I wondered - is there an intuitive explanation for this?!


This is an English test item: The human eye is nature's most fantastic organ, and the high degree of development of human society probably depends upon ......... . a) developing of this organ b) the development of this organ Which choice is correct? And why is the other one not correct? Thanks

Could anyone explain when to use a noun or a gerund?  Are these sentences correct? What is the difference between usage of gerund and noun there?        I worked on the improvement of the article.   I worked on the article improving.   I worked on the improving of the article.                The investment idea was published.   Investing idea was published.


A few days ago, I upgraded my Windows 8 Lenovo U410 ideapad to Windows 8.1, and it proved to be a terrible mistake. It seems like the only visible change that it has made is adding the start button. Meanwhile, it disabled my audio, and I had to go and reinstall drivers from Lenovo's website. Even worse, it is completely blocking me from running Ubuntu in any way possible.  I have my hard disk partitioned into three main partitions: 100GB for Windows (in NTFS); 100GB for Ubuntu (in ext4...I think); and a 550GB storage drive (in NTFS). Then on start up, the Ubuntu GRUB screen ( one) would come up and I would be able to choose between booting into Ubuntu and Windows 8. However, now after the update, I boot straight into Windows 8.1, and cannot access the Ubuntu file system.  This wouldn't be that big of a problem, if it wasn't for the fact that three almost-finished Honors English papers are on there, and I NEED them. So first I tried booting into the Ubuntu partition from the bios, which didn't work, and neither did trying to boot into it from the "Use a Device" menu in the Windows "Advanced Startup" menu. Next, I tried moving the Ubuntu partition to the first spot in the boot sequence, and starting up my computer again. When that had no effect, I created an Ubuntu USB drive, and went through all the same steps (this is what the answers to questions similar to mine recommend). Again, no result. I've also noticed that even after changing the boot sequence in the BIOS, Windows Boot Manager forces itself back to the front.  I'm at a loss for what to do, and I really need those English papers, so any help is MUCH appreciated. Thank you for reading this far, and thanks in advance for any advice.

I have a Sony VAIO S series with Windows 8 preinstalled, and I installed Ubuntu 12.10 on a new partition. When the PC boots Grub is display, and I can choose between Windows 8 (didn't worked at the beginning, had to change Grub settings) and Ubuntu 12.10. When I select Ubuntu 12.10 everything is OK, but when I use Windows 8, and I restart Grub isn't displayed anymore (Windows 8 boots immediately).  I booted a Ubuntu 12.10 LiveUSB, used efibootmgr, and found out that Windows 8 (each time it boots) changes EFI default bootloader from Grub to Windows Boot Manager.  How do I change this in Windows 8? I read something about bcdedit, but it does not work or I don't know how to use it...


Do I download the games to hard drive?     How much is the service?   Does Steam OS make the experience better or what?

What exactly is Steam? Isn't it DRM?  What can I do with it?


First of all: I am new to maven. I made my first maven Application and successfully tested it within the IDE. The build was always successfull and everything worked like a charm.  Now I want to export the project as an executable jar with the dependencies built in, but I am not quite sure why it is not working.  I added the following to my pom file, as that was what I found on various answers to a similar question  <build>         <plugins>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-jar-plugin</artifactId>                 <version>2.4</version>                 <configuration>                     <archive>                         <manifest>                             <addClasspath>true</addClasspath>                             <mainClass>com.pwc.scfa.pensareautomatio3.Main</mainClass>                         </manifest>                     </archive>                 </configuration>             </plugin>         </plugins> </build>   I understand that this specifies the main class for the JVM to start, as the IDE does not set this automatically.  I located the jar in the targets directory, copied it to another directory and tried to execute it.  Sadly the following errors are thrown:      Can you please give me a hint, where I might have gone wrong? That would be great. (I am using NetBeans, if that is of any help.)  Here is my StackTrace:  C:\Users\scfa\Desktop>java -jar PensareAutomatio-1.1.jar Error: A JNI error has occurred, please check your installation and try again Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/poi/openxm l4j/exceptions/InvalidFormatException         at java.lang.Class.getDeclaredMethods0(Native Method)         at java.lang.Class.privateGetDeclaredMethods(Unknown Source)         at java.lang.Class.privateGetMethodRecursive(Unknown Source)         at java.lang.Class.getMethod0(Unknown Source)         at java.lang.Class.getMethod(Unknown Source)         at sun.launcher.LauncherHelper.validateMainClass(Unknown Source)         at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source) Caused by: java.lang.ClassNotFoundException: org.apache.poi.openxml4j.exceptions .InvalidFormatException         at java.net.URLClassLoader.findClass(Unknown Source)         at java.lang.ClassLoader.loadClass(Unknown Source)         at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)         at java.lang.ClassLoader.loadClass(Unknown Source)         ... 7 more   Thanks :)

I want to package my project in a single executable JAR for distribution.  How can I make a Maven project package all dependency JARs into my output JAR?


I have a list like this  lst = [1,3,5]  and a major list like lost =['the' , 'cat' , 'thinks' , 'you' , 'are' , 'crazy' ]  I want to delete elements in second list based on indexes in the first one . It means i have to remove 'cat' , 'you' and 'crazy' . The problem is if i use : lost.remove(lost[1]) lost.remove(lost[3]) lost.remove(lost[5])  First problem is its not gonna work out! Because as we remove the first element the length of the list(named lost) decreases and in that way we will remove wrong elements. Second problem is the list named(lst) will not always be [1,3,5] . Its gonna change in length and in elements . How can i fix the problem?

Is it possible to delete multiple elements from a list at the same time? If I want to delete elements at index 0 and 2, and try something like del somelist[0], followed by del somelist[2], the second statement will actually delete somelist[3].  I suppose I could always delete the higher numbered elements first but I'm hoping there is a better way.


Is there any update on if there is a fix to get the keyboard working. I have tried installing the latest kernel.

My dad bought a Surface laptop for me. Can run Ubuntu on it? I tried and the keyboard does not work, so is there any version available that solves this problem?