I hope you are all doing fine! I'm a 14 year old student from the UK, and have been really interested in theoretical physics, but before I reach that I need to build on more basic knowledge. So I set out to learn calculus and some linear algebra, mostly from Khan Academy and 3B1B's videos on the topic. However, I can't find much content for Classical Mechanics online. Are there any websites or maybe textbooks that you can recommend me, so that I can further my knowledge on this subject! P.S. The last time I asked my teacher if he could point me in the right direction, he just told me to keep my head down, but I know I am capable of learning complicated concepts, it is not beyond me :)

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


I have written small program but getting undefined reference error. I'm not getting what I'm doing wrong  #include <iostream>  using namespace std; class A() { private:      static A *m_object;     A()     {         m_object = NULL;     }  public:      static A* getSingleton();      int returnVar()     {         return 45;     }  }; A* A::getSingleton() {     if(A::m_object == NULL)     {        A::m_object = new A();     }     return m_object; } int main() {     cout<<"Hello World";     A *a = A::getSingleton();     cout<<"Address of a"<<&a<<endl;     cout<<"return a"<<a->returnVar()<<endl;     A *b = A::getSingleton();     cout<<"Address of a"<<&b<<endl;     return 0; }   error  /home/main.o: In function `A::getSingleton()': main.cpp:(.text+0x3): undefined reference to `A::m_object' main.cpp:(.text+0x21): undefined reference to `A::m_object' /home/main.o: In function `main': main.cpp:(.text.startup+0x16): undefined reference to `A::m_object' main.cpp:(.text.startup+0x7e): undefined reference to `A::m_object' main.cpp:(.text.startup+0xcb): undefined reference to `A::m_object' /home/main..o:main.cpp:(.text.startup+0xde): more undefined references to `A::m_object' follow collect2: error: ld returned 1 exit status

Can anyone explain why following code won't compile? At least on g++ 4.2.4.  And more interesting, why it will compile when I cast MEMBER to int?  #include <vector>  class Foo {   public:       static const int MEMBER = 1;   };  int main(){       vector<int> v;       v.push_back( Foo::MEMBER );       // undefined reference to `Foo::MEMBER'     v.push_back( (int) Foo::MEMBER ); // OK       return 0; }


In real analysis class, the professor used a basic property to give an easier definition of measurable function, it says:  Any open set $G\subset\mathbb{R}$ has the form $G=\sqcup_i (a_i,b_i)$.  It is an axiom? or how to prove it?   By the way, it seems I need some background knowledge of this kind of set properties. Are there some materials I can refer?

Let $U$ be an open set in $\mathbb R$. Then $U$ is a countable union of disjoint intervals.    This question has probably been asked. However, I am not interested in just getting the answer to it. Rather, I am interested in collecting as many different proofs of it which are as diverse as possible. A professor told me that there are many. So, I invite everyone who has seen proofs of this fact to share them with the community. I think it is a result worth knowing how to prove in many different ways and having a post that combines as many of them as possible will, no doubt, be quite useful. After two days, I will place a bounty on this question to attract as many people as possible. Of course, any comments, corrections, suggestions, links to papers/notes etc. are more than welcome.


As a student in France with a long-term student visa, I want to go from Barcelona airport back to my country. Is it possible or do I have to exit from France only?

I have requested for a French long term (Type D) student visa from a consulate in India. It's a national Type D visa and not a Schengen visa. My question is that can we still go to other Schengen countries on this visa? If not then can we get a Schengen visa from a consulate in France?


Show that the complement of every connected subset of $S^1$ is also connected.   Here $S^1$ means $S^1 = \{(x,y)\in\mathbb{R}^2:x^2+y^2=1\}$.  Can someone give some hints on this? It seems that arcs are the only connected subset of $S^1$. If it is true, the the complement of this subset is also a arc, which of course is also connected. Is this intuition true? Can someone give some hints on how to proceed? Thanks in advance.

Let $A$ be a connected set in $\mathbb{S}^1$. Show that $A^c$ is also connected.  My idea: suppose $A^c$ is not connected. Then, there exist $U,V \subset \mathbb{S}^1$ open and disjoint such that $U \cup V =A^c  $. Therefore $\mathbb{S}^1 = A \cup U \cup V$. If I had that $A\cup U$ was open I could arrive at  contradiction, since $\mathbb{S}^1$ is connected, but I can't say that...


Is there a known solution to:  $$a^2+b^2=c^2+d^2$$  Hopefully the question is clear, if not I do apologize.

I was reasonably certain I've seen this before, but I was wondering how to solve the Diophantine equation  $$a^2+b^2=c^2+d^2$$  I tried a web search and found nothing on this one.  I'm trying to avoid another library trip to a less than local library (maybe I should have taken better notes on that chapter...).  I'm not quite sure how to handle this one.  The only thing I can figure out with this equation, if I remember correctly, is that the sum on either side may only contain prime factors of 2 or odd primes congruent to 1 mod 4.  And if I don't want a and b equal to c and d, the sum can't be prime as I believe a prime congruent to 1 mod 4 can be represented as the sum of 2 squares in exactly one way.  But that doesn't give me any insight into actually solving this problem.


I would like to have GUIDs in my app, in the shape of /[0-9]{32}/, so it could have 12131415... or 1020304010101010101..., each one exactly 32 characters long.  I would like for it to be evenly distributed over the set. By that I mean I don't want the IDs to be used in this order:  10000000000000000000000000000000 10000000000000000000000000000001 10000000000000000000000000000002 10000000000000000000000000000003 ...   I would like for it to feel random:  91837183748159173751758138571830 18281849104849293849185918918905 ...   The way I am thinking about doing this is by just generating all of the numbers up front, and then shuffling the array. But this won't work for large sets of strings like what I have here, it will run out of memory.  So I am not sure what to do instead.  I am doing this in Node.js and will save each GUID as a record to the database as a GUID schema/model with a property/attribute value which contains its actual ID, using Mongoose.  It seems the next best option is to randomly generate a string, and check if it's unique first before trying again. But I've tried this approach before and it seems to exponentially slow down the larger the set gets.  So I'm wondering what the general approach is to generating a large set of numbers like this so that you can pluck one at random and it feels random. I only currently need like 1 trillion of them, but I would like for it to be not 0-1000000000000, but 1 trillion out of the set of 0-99999999999999999999999999999999, seemingly evenly distributed.  Wondering how to accomplish that, either in my specific Node.js/JavaScript/Mongoose situation, or just generally in pseudocode or any procedural language.

I'm trying to create globally-unique identifiers in JavaScript.  I'm not sure what routines are available on all browsers, how "random" and seeded the built-in random number generator is, etc. The GUID / UUID should be at least 32 characters and should stay in the ASCII range to avoid trouble when passing them around.


(or slate) is used in movie primarily for two purposes:   To assist in synchronizing picture and sound (with the help of a ). It makes the editor's life easy. Cataloging of the recordings i.e. designate and mark particular scenes and takes recorded during a production.   I understand it is a crucial and an essential tool which is still used in the film-making process. It has evolved from traditional  slate to the modern  version.  Why hasn't anything better replaced the slate? By better I mean a tool or a technique (an automated one perhaps) which works by itself without an assistance of a human? Something which can fullfil the same purpose of the slate (Cataloging and synchronization while editing).  Or are we just using it for its legacy?

As I understand, modern film and audio are synced using SMPTE timecode which is embedded in the metadata of the respective source files.  Modern clappers also display the timecode, but they still have the clapper bar.  Is it really necessary to actually clap the clapper anymore?


I bought Galaxy S5 from T-Mobile which had Android 4.4 (last year). Back in October I needed Android 5 to test a mobile application (I am a developer) and I installed official S5 Polish ROM which was the only one available in December last year.   Now, I don't need it any more as it does not work perfectly well (but had to stick to it till now).   How can I return my original ROM?

There are several reasons to be looking for a ROM:   Upgrading or downgrading your stock ROM Looking for firmware from a different region/language Flashing a custom ROM for different features, removing bloat, etc.   But where can one find ROMs in the first place?  What sites are likely to have the ROM I need?  ; please add to the wiki answer instead of posting separate answers.  See also:


I have to remove a specific set of words from a string. E.g. following words needs to removed (ooh,aah and etc) from an employee_description. Below query I have tried:  SELECT REPLACE(REPLACE(emp_desc, 'aah', ''), 'ooh', '') from TEST_Table;   It's working fine.  But is there any other Best Way to do this.

I have a string coming from a table like "can no pay{1},as your payment{2}due on {3}". I want to replace {1} with some value , {2} with some value and {3} with some value .  Is it Possible to replace all 3 in one replace function ? or is there any way I can directly write query and get replaced value ?   I want to replace these strings in Oracle stored procedure the original string is coming from one of my table I am just doing select on that table   and then I want to replace {1},{2},{3} values from that string to the other value that I have from another table


designers,  I would like to ask You, where could I find patterns - backgrounds to download it it is possible for free - for businness cards, posters, logos, etc.? I mean, when I create some design and want to place it/put it like in real environment:  for example:   Is there are photoshop files or something like that?  Thank You

I'm always on the hunt for free stock images to use while I design, what are some good resources for images that are under a a royalty free or creative commons licence?


Is there any harm or benefit for having instance methods call static methods to do their work?  If your confused by what I mean, take a look at the example code below.  StripFormatting is an instance method and static method.  If another developer creates an instance of PhoneUtil then all that is needed is for the StripFormatting method to be called on the instance of the object.  If a developer decides not to create an instance of PhoneUtil they can call the static method except this method has a parameter for the PhoneNumber.  public string StripFormatting() {         return PhoneUtil.StripFormatting(this.PhoneNumber); }  public static string StripFormatting(string psPhoneNumber) {         string tsPhoneNumber = psPhoneNumber;         Regex toNotDigit = new Regex("\\D+");         tsPhoneNumber = toNotDigit.Replace(tsPhoneNumber, "");         return tsPhoneNumber; }

ReSharper likes to point out multiple functions per ASP.NET page that could be made static. Does it help me if I do make them static? Should I make them static and move them to a utility class?


This question is related to this post (accepted answer):  .  After compiling the code below I obtain this outcome:   I have tried several alternatives such as adding backslashes or "&" symbols but I am still unable to obtain the desired results.    Thanks in advance.   \documentclass[a4paper,12pt]{scrreprt}     \usepackage{booktabs}      \begin{document}     \begin{table}     \centering     \begin{tabular}{@{} lcccc @{}} % suppress vertical whitespace at start and end     \toprule     Company& \multicolumn{3}{c}{Exceedances} & No.\ of Obs.\    \cmidrule(lr){2-4}     & \multicolumn{2}{c}{Empirical} & Expected\    \cmidrule(lr){2-3} \cmidrule(lr){4-4}     &standard & standardized\\    % make columns 2 and 3 narrower     &normal   & Student's-$t$\    \midrule     Company 1&1&5&9&13\    Company 2&2&6&10&14\    Company 3&3&11&15\    Company 4&4&8&12&16\    \midrule[\heavyrulewidth] % use "thick" \midrule instead of \bottomrule     \multicolumn{4}{@{}l}{\footnotesize An additional hint about a detail}     \end{tabular}     \caption{Here is the caption.}     \label{labelhere}     \end{table}      \end{document}

I use the following table:  \documentclass[a4paper,              12pt,                                        bibliography=totoc,              index=totoc,             abstracton,              headsepline,             ]{scrreprt}  \usepackage{booktabs}    \begin{document}   \begin{table}[H]\hspace*{-1cm} \centering \begin{tabular}{lcclll} \toprule  Company& \multicolumn{2}{c}{exceedances (empirical)}&exeedances (expected)&no. of obs.\\ \cmidrule(r){2-3}\\ &standard normal&standardized Student's-t&&\\ \midrule Company1&1&5&9&13\\ Company2&2&6&10&14\\ Company3&3&11&15\\ Company4&4&8&12&16\\ \bottomrule \multicolumn{4}{l}{\begin{footnotesize}an additional hint about a detail\end{footnotesize}} \end{tabular} \caption{Here is the caption.} \label{labelhere} \end{table}   \end{document}     Which gives    I have two problems:   The space after the \cmidrule(r){2-3} is too big, how can I change this? The table looks not that good, how can I improve it in general?


I have a data set comprising of responses from approximately 385 people on several variables such as their shopping habits, mode of transport to the shopping centre  etc. I want to do Pearson correlation on the variables (by age, gender, income level etc. of the respondents).  Is there any rule that says what would be the maximum number of tests that can be reliably performed on this data set? I am unsure if "reliable" is the correct term; I mean "valid" or "sound" in this case.  My alpha is 0.05 and I have corrected it using Sidak's method, so the experiment wise error is 0.05 for the 80 tests that I want to perform on this data set.

I have several hundred measurements. Now, I am considering utilizing some kind of software to correlate every measure with every measure. This means that there are thousands of correlations. Among these there should (statistically) be a high correlation, even if the data is completely random (each measure has only about 100 datapoints).  When I find a correlation, how do I include the information about how hard I looked for a correlation, into it?   I am not at a high level in statistics, so please bear with me.


The Hubble Space Telescope is in the news every now and then. How can it photograph galaxies that are millions of light years from Earth?  We can understand that light comes from galaxy and Hubble "catches" it. But does nothing come between the galaxy and Hubble that absorbs or scatters the light over a distance of say 30 million light years? How? Or is there any other concept?

The HUDF used to be the deepest image of the universe ever taken by the Hubble telescope, the furthest star in this image is 59000 light years away.  The star in question:   Now Imagine a light emitting object like a star and an observer like a telescope, 59000 light years apart. I represented everything in 2D, but in 3D I suppose it would be the same but with spheres:    Now picture the photons that the object is emitting, in particle form. They will all have one direction and they will go towards this direction at C, given that there are no massive objects in between their paths:    Notice how the photons have separate paths, because they have different directions, now obviously there should be a lot more photons but for simplicity I drew it like that. My point is, given enough distance shouldn't the probability of hitting a photon be so small that seeing an object becomes nearly impossible? Like so:    Here the observer can detect the photons, but if it was slightly off it wouldn't:    So how can we detect objects so far away? Is there something about light's wave form that I'm not considering, is this how light is emitted at all?  Update:  Looking at other duplicates questions I've seen two answers:  1- There are just too many photons being emitted that the "gaps" are just too small to make any difference.  2- This isn't really how photons are emitted, instead a quantum field is spread out radially and we only detect the photon when we interact with the field.  Does this mean that there are objects that we can't see, even if given enough time for the light to reach us (presumably outside of the current observable universe)?  Or do the gaps not exist at all because of answer number 2?


I'm trying to implement autorelease pool in c++, and have trouble with deallocating. So we have root-class object:  class object {  public:     object() {         retainCount_ = 0;     }     ~object() {         std::cout << "object " << Description() << " is dealocated" << std::endl;     }     /* code with retain/release here */     int retainCount() {         return retainCount_;     }     std::string Description() {         std::stringstream ss;         ss << this;         return ss.str();     }  private:     int retainCount_; };   And some realization:  class Integer : public object {  public:     int i;     Integer(int ii) : i(ii) {}     ~Integer() {         std::cout << "Integer " << Description() << " is dealocated" << std::endl;     } };   And of course release pool class, which works with root-class pointers:  class release_pool {  public:     void insert(object* obj) {         pointers_.insert(obj);     }     void flush() {         std::set<object*>::iterator it = pointers_.begin();         std::set<object*>::iterator tmp;         const int N = pointers_.size();         for (int i = 0; i < N; i++) {             tmp = it;             it++;             if ((*tmp)->retainCount() == 0 ) {                 object* obj = *tmp;                 std::cout << "delete obj: " << obj->Description() << std::endl;                 pointers_.erase(tmp);                 delete obj;             }         }     }  private:     std::set<object*> pointers_; };   main.cpp code for test:  int main () {     release_pool pool;      Integer* obj = new Integer(5);     pool.insert(obj);     std::cout << "before flush: " << obj->i << "\n";      pool.flush();      std::cout << "after flush: " << obj->i << "\n";         return 0; }   After build, I get next:  before flush: 5 delete obj: 0x7f9a84c025d0 object 0x7f9a84c025d0 is dealocated after flush: 5   At the end: destructor of root-class is invoked, but of Integer not. Hence, we have leaked memory, which is allocated for Integer object. Have you any ideas to fix it? How i can delete whole object, not root-part of it.

I have a solid understanding of most OOP theory but the one thing that confuses me a lot is virtual destructors. I thought that the destructor always gets called no matter what and for every object in the chain. When are you meant to make them virtual and why?


I've annoyingly got what appears to be a very 'popular' error. However, in my case I'm supplying the expected parameter and it definitely has a value, so I'm stumped. Here's my code:  public static DataTable MyDataTable(string pd, bool showAll) {     DataTable results = new DataTable("PD results");      string Conn = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;      using (SqlConnection connection = new SqlConnection(Conn))     {         SqlCommand cmd = new SqlCommand("dbo.MyProcedure", connection);          SqlParameter pdParam = new SqlParameter("@i_user", SqlDbType.VarChar);         pdParam.Value = pd;         cmd.Parameters.Add(pdParam);          if (showAll)              cmd.Parameters.AddWithValue("@i_ShowALL", (int)1);         else              cmd.Parameters.AddWithValue("@i_ShowALL", (int)0);          SqlDataAdapter da = new SqlDataAdapter(cmd);          try         {             da.Fill(results);         }         catch (Exception ex)          {             string error = ex.Message;         }      }       return results; }   I've stepped through the code and the error occurs with parameter @i_user. However, when I'm adding the parameter it has a value and I confirmed this when looking at the SqlDataAdapter > SelectCommand >Parameters > Non-Public members > items > [0] {@i_user} > base > value.  Despite having the parameter supplied with a varchar value I get the error      Procedure or function 'dbo.MyProcedure' expects parameter '@i_user' which is not supplied   What am I doing wrong?

I'm getting the error when accessing a Stored Procedure in SQL Server  Server Error in '/' Application. Procedure or function 'ColumnSeek' expects parameter '@template', which was not supplied.    This is happening when I call a Stored Procedure with a parameter through .net's data connection to sql (System.data.SqlClient), even though I am supplying the parameter. Here is my code.  SqlConnection sqlConn = new SqlConnection(connPath); sqlConn.Open();  //METADATA RETRIEVAL string sqlCommString = "QCApp.dbo.ColumnSeek"; SqlCommand metaDataComm = new SqlCommand(sqlCommString, sqlConn); metaDataComm.CommandType = CommandType.StoredProcedure; SqlParameter sp = metaDataComm.Parameters.Add("@template",SqlDbType.VarChar,50); sp.Value = Template;  SqlDataReader metadr = metaDataComm.ExecuteReader();   And my Stored Procedure is:     USE [QCApp]    GO    SET ANSI_NULLS ON    GO    SET QUOTED_IDENTIFIER ON    GO     ALTER PROCEDURE [dbo].[ColumnSeek]         @template varchar(50)    AS    EXEC('SELECT Column_Name, Data_Type     FROM [QCApp].[INFORMATION_SCHEMA].[COLUMNS]     WHERE TABLE_NAME = ' + @template);   I'm trying to figure out what I'm doing wrong here.  Edit: As it turns out, Template was null because I was getting its value from a parameter passed through the URL and I screwed up the url param passing (I was using @ for and instead of &)


I am looking to copy the filename as text from a folder as seen in windows explorer in windows 7, so that i can paste in other editor.  I there any way to achieve this. I don't see any such feature in the context menu.  Note: I am looking for a windows solution, i don't want/can't install new software.

Is there a way to copy the currently selected filename, including the path, to the clipboard? Ideally this would be through the right-click menu.  Some degree of flexibility would be useful, like the ability to copy just the filename, path+filename, filename minus extension, etc. This isn't essential, though, as long as it can copy the path+filename.  The solution must be compatible with Windows XP, Windows Vista and Windows 7.


This is a question that comes in two parts.  First, prove that if $a^{2^{n-1}}\not\equiv1 \pmod {2^{n}}$, then $a$ is even. Second, prove that for any odd prime $p$, if $a$ is odd and $a^{2^{n-1}(p-1)}\not\equiv1 \pmod 2^{n}p$, then $p|a$.  For the first one, I realized I can try proving the contrapositive, and then use induction. Then what should I do next? Fermat's Little Theorem? For the second one, can you split the modulus into $2^{n}$ and $p$? I think this might be a good method. Answers and ideas are welcome!

I would like to prove that  $$a^{2^n}\equiv 1 \pmod {2^{n+2}}$$  I tried induction but could not get it.  Thank you very much!


Do I need to to hyphenate: "It is a locally-injective mapping." where I use locally injective as a term--a concept: "This mapping is locally injective." For example, it is defined in: [Weber14 "Locally Injective Parametrization with Arbitrary Fixed Boundaries"]   Adding some links regarding hyphenating the adverb 'well', which may be relevant: A Well-Known Problem: Hyphens With “Well” Words  Well-Hyphenated Compound Adjectives   "The elements of style" by Strunk and White says: "When two or more words are combined to form a compound adjective, a hyphen is usually required."  The wiki page is quite comprehensive and sounds convincing:

Remarkably low condensation temperature  or  Remarkably-low condensation temperature?  The focus of remarkable is that it is such a low temperature. We are having an office disagreement and any help is much appreciated.


I am sick of the Armor, and I want to wear a purple shirt. In my attempts to remove the armor I have used the select option, gone into stores, and went into my wardrobe. How do I take the armor off?

It's kind of hard to shop for clothes with a big bullet proof vest on.  Is there a way to take off the armor after missions, or at least hide it?


I just realized that my identicon in the  page has a different color and pattern compared to that in my  page:   Looking at other users profiles didn't show any differences between their ranking and profile identicons. Is this a bug? Update It seems to be an issue with gravatar producing different icons depending on the size of the icon you demand. The hash is actually just the md5 sum of your registered email address.

When I first signed up on a Stack Exchange site and got a profile image, it was this one (see my current user card I'm actually not sure what I look like any more):     Later, I got  and SEDE profiles, and my user image there was a different identicon. Because . I would have a picture of it, but that's the problem. ... Thanks to , I have a picture:     On those two sites, it changed from that purple one to this new one recently:   I don't know when the change happened exactly, but I KNOW I didn't change it (I don't know how to change it, otherwise I would have changed it to my main pink one).  Why did this change? Can I get my other icon back or will I be stuck with this new one?   Also, are the gravatars at Area 51 and SEDE securely generated?    After looking in my profile settings, I really confused (I am seeing my wrong avatar in more and more places since I first posted this.):        Seriously.......    What...?    (I'm using this , but be warned that they will try to IP block you after a certain number of requests to force you to pay... May look for a better alternative later.)


I saw this answer:    where the poster is trying to solicit a user for his product.   His answer though, is on topic and appropriate.     Is this spam?   I'm inclined to think not.  Should we remove/edit user contact info and just leave the product link?  Maybe?  Should we do nothing? ???  I saw related question:  but this is different because I believe this poster is trying to sell something.

Twice now I've seen questions on Stack Overflow where one of my company's products might provide an answer to the question.  One was a slightly vague connection about object-relational mapping, but the other was a specific question about workshop/event management where we have a product which is almost an exact match for the questioner's needs.  Of course the questioner should take a pinch of salt with anything I say about it, but it might be useful to have the product brought to his attention as one possible solution.  What are the rules and guidelines about answering with something I worked on?


My Windows 10 64bit PC has 16GB of physical RAM:  C:\>wmic MEMORYCHIP get BankLabel, DeviceLocator, Capacity BankLabel  Capacity     DeviceLocator BANK 0     17179869184  ChannelA-DIMM0   Also under About your PC it says:  Installed RAM 16.0 GB (15.7 GB usable)   But in Task Manager my memory shows as 83% full. Once in a while some applications get automatically closed because of out of memory issues. So I digged in to check what uses so much RAM. The biggest offender was Firefox with about 800MB of RAM. But that's just not that much. Then I did a tasklist /FO CSV > tasks.csv to sum up all the memory usage, and the result was 6.4GB, which is about 83% out of 7.7GB (assuming that 0.3GB are always reserved for video stuff).  This suggests that even though Windows sees the full 16GB, it only uses 8GB. Or, it uses 8GB for some secret stuff it doesn't want to show in task manager.  Any suggestions on how to investigate this further?

Imagine I have tons of RAM. Let's say 64GB. That's a lot for even gaming PCs. Now the default location of a pagefile in Windows is on the main OS drive, be it HDD or SSD, which are faster in general, but still not as fast as RAM.  Something tells me that disabling the pagefile on the hard drive or creating a virtual RAM drive and letting the pagefile be there could make Windows move all its virtual memory to RAM, and so increase the system's performance, but I'm not very knowledgeable in that area, so that might not be true at all.  I tried both, but I couldn't analyze the results to reach a definite conclusion with my knowledge level in memory things.  Would this work? If not, why?


can you help me with this error: Errors were encountered while processing: virtualbox-dkms I installed Oracle Virtualbox and it's working well. $ sudo apt install ./zoom_amd64.deb [sudo] password for louisro:  Reading package lists... Done Building dependency tree        Reading state information... Done Note, selecting 'zoom' instead of './zoom_amd64.deb' The following packages were automatically installed and are no longer required:   kbuild libgsoap-2.8.91 libvncserver1 module-assistant virtualbox-source Use 'sudo apt autoremove' to remove them. The following packages will be upgraded:   zoom 1 upgraded, 0 newly installed, 0 to remove and 6 not upgraded. 1 not fully installed or removed. Need to get 0 B/45,9 MB of archives. After this operation, 85,7 MB disk space will be freed. Get:1 /home/louisro/zoom_amd64.deb zoom amd64 5.4.57862.0110 [45,9 MB] (Reading database ... 266695 files and directories currently installed.) Preparing to unpack /home/louisro/zoom_amd64.deb ... Unpacking zoom (5.4.57862.0110) over (3.5.392530.0421) ... run post uninstall script, action is upgrade ... Setting up virtualbox-dkms (6.1.10-dfsg-1~ubuntu1.20.04.1) ... Removing old virtualbox-6.1.10 DKMS files...  ------------------------------ Deleting module version: 6.1.10 completely from the DKMS tree. ------------------------------ Done. Loading new virtualbox-6.1.10 DKMS files... Building for 5.8.0-36-generic Building initial module for 5.8.0-36-generic ERROR: Cannot create report: [Errno 17] File exists: '/var/crash/virtualbox-dkms .0.crash' Error! Bad return status for module build on kernel: 5.8.0-36-generic (x86_64) Consult /var/lib/dkms/virtualbox/6.1.10/build/make.log for more information. dpkg: error processing package virtualbox-dkms (--configure):  installed virtualbox-dkms package post-installation script subprocess returned  error exit status 10 Setting up zoom (5.4.57862.0110) ... run post install script, action is configure... Error in file "/usr/share/applications/org.kde.kdeconnect_open.desktop": "*/*" i s an invalid MIME type ("*" is an unregistered media type) Processing triggers for mime-support (3.64ubuntu1) ... Processing triggers for gnome-menus (3.36.0-1ubuntu1) ... Processing triggers for shared-mime-info (1.15-1) ... Processing triggers for desktop-file-utils (0.24-1ubuntu3) ... Errors were encountered while processing:  virtualbox-dkms E: Sub-process /usr/bin/dpkg returned an error code (1)

After the latest Ubuntu updates, I have not been able to open virtualbox, on starting it gives me an error saying the kernel driver is either not loaded or set up properly and that I should reinstall virtualbox-dkms package. After removing virtualbox, and trying to reinstall I get the error below: ERROR: Cannot create report: [Errno 17] File exists: '/var/crash/virtualbox-dkms.0.crash' Error! Bad return status for module build on kernel: 5.8.0-34-generic (x86_64) Consult /var/lib/dkms/virtualbox/6.1.10/build/make.log for more information. dpkg: error processing package virtualbox-dkms (--configure):  installed virtualbox-dkms package post-installation script subprocess returned error exit status 10 dpkg: dependency problems prevent configuration of virtualbox:  virtualbox depends on virtualbox-dkms (>= 6.1.10-dfsg-1~ubuntu1.20.04.1) | virtualbox-source (>= 6.1.10-dfsg-1~ubuntu1.20.04.1) | virtualbox-modules; however:   Package virtualbox-dkms is not configured yet.   Package virtualbox-source is not installed.   Package virtualbox-modules is not installed.   Package virtualbox-dkms which provides virtualbox-modules is not configured yet.  dpkg: error processing package virtualbox (--configure):  dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of virtualbox-qt:  virtualbox-qt depends on virtualbox (= 6.1.10-dfsg-1~ubuntu1.20.04.1); however:   Package virtualbox is not configured yet.  dpkg: error processing package virtualbox-qt (--configure):  dependency problems - leaving unconfigured No apport report written because the error message indicates it's a follow-up error from a previous failure.                             No apport report written because the error message indicates it's a follow-up error from a previous failure.                                                         Processing triggers for menu (2.1.47ubuntu4) ... Processing triggers for bamfdaemon (0.5.3+18.04.20180207.2-0ubuntu2) ... Rebuilding /usr/share/applications/bamf-2.index... Processing triggers for desktop-file-utils (0.24-1ubuntu3) ... Processing triggers for mime-support (3.64ubuntu1) ... Processing triggers for hicolor-icon-theme (0.17-2) ... Processing triggers for gnome-menus (3.36.0-1ubuntu1) ... Processing triggers for systemd (245.4-4ubuntu3.3) ... Processing triggers for man-db (2.9.1-1) ... Processing triggers for shared-mime-info (1.15-1) ... Errors were encountered while processing:  virtualbox-dkms  virtualbox  virtualbox-qt E: Sub-process /usr/bin/dpkg returned an error code (1)  This happens even when I boot from the previous kernel using the grub menu, any help would be very appreciated. I have also tried to use aptitude to remove any conflicting versions of virtualbox from other repositories but still the same issue.


I was doing this  , but when it comes to the part where O should run these commands:  local-server#  ssh -NTCf -w 0:0 87.117.217.27 local-server#  ssh -NTCf -w 1:1 87.117.217.44   It says:  channel 0: open failed: administratively prohibited: open failed   How can I fix that?

When I open this ssh tunnel:  ssh -nXNT -p 22 localhost -L 0.0.0.0:8984:remote:8983   I get this error when trying to access the HTTP server running on localhost:8984:  channel 1: open failed: administratively prohibited: open failed   What does this error mean, and on which machine can you fix the problem?


Sample conversation:     Person 1:  What did you think of the movie?   Person 2:  Well, the acting was great, but the plot was terrible.   What does "well" actually add to the body of the sentence?  I have never heard any sentence spoken or written whose meaning was absolutely dependent on beginning with "well".  It seems akin to an "um" or "uh", serving as a vocal void filler while the speaker collects their thoughts and puts their words together before actually speaking them.  If that's the case, why do people actually type it?  People clearly have time to think about what they're going to say before posting a comment on a blog or replying to an email.  Has it become a sort of accepted language anomaly much in the same way Midwesterners like to say things like "Where did you put it at?"

I've watched two interviews. One with Grace Park, one with Eliza Dushku.  What one can't miss is that Eliza uses an awful lot of garbage words (or what these are called) — um, so, like, you know, actually, I guess, I mean, kind of... — whereas Grace doesn't use them much.  YouTube links:       My questions are:   What is more common to hear in US "on the street" (not on TV)? Does it affect the way the speaker is being considered by audience? (Like, speaking fluently without garbage words → smarter?) Does this differ geographically? What are these words called?


How do I make a bootable usb pen drive to install my windows 10 iso on 15.04?  I'd like detailed instructions with commands and  or possibly a link.

I'd like to create a Windows bootable USB stick, but I don't have a Windows machine with me at the moment to do so. How could I achieve the same using Ubuntu?


drwxr-xr-x. 2 root root 4096 Jun 29 16:44 db drwxr-xr-x. 2 root root 4096 Jun 29 16:44 djproject -rwxr-xr-x. 1 root root   38 Jun 29 16:44 index.html drwxr-xr-x. 2 root root 4096 Jun 29 16:44 jobs -rwxr-xr-x. 1 root root  252 Jun 29 16:44 manage.py drwxr-xr-x. 3 root root 4096 Jun 29 16:44 templates   What is the meaning of those numbers in the second column? Do they have some relation to file and folder permissions? How do I change the numbers?

I want to learn about the meaning of values for example first line;  drwxr-xr-x 2 ataka root 4096 2008-11-04 16:58 ataka   is ataka here the owner of directory ?  kioutsovkm@orkide:/users/lnxsrv2/ee$ ls ataka  aydinoglu  izgordu  kioutsovkm  kocaogluo kioutsovkm@orkide:/users/lnxsrv2/ee$ ls -l total 20 drwxr-xr-x 2 ataka     root 4096 2008-11-04 16:58 ataka drwxr-xr-x 2 aydinoglu root 4096 2008-11-04 16:58 aydinoglu drwxr-xr-x 3 izgordu   root 4096 2009-09-29 11:59 izgordu drwxr-xr-x 2 root      root 4096 2008-11-04 16:58 kioutsovkm drwxr-xr-x 4 kocaogluo root 4096 2010-06-10 03:41 kocaogluo kioutsovkm@orkide:/users/lnxsrv2/ee$


Recently given a laptop with Ubuntu 12.1 installed alongside Windows 7.  Can only access Ubuntu, which is fine for everyday use (LibreOffice, Firefox, etc.) but there's an authentication password required to install the 500+ updates, and when trying to run anything in terminal, it asks for "quiz's" password.  It won't allow me to go into root mode to bypass the password (if that's even a real thing?).  I'm completely new to Linux, but am fascinated at the capabilities and would like to mess around some more, but keep getting stopped by these passwords.  What do I have to do?  Uninstall and re-install?  How does one do that if I don't even have access to the Windows 7 OS because it is password protected as well?  Thanks in advance for any information and help.

I'm working on a Ubuntu system, and my client has completely forgotten his administrative password. He doesn't even remember entering one; however it is there.  I've tried the suggestions on the website, and I have been unsuccessful in deleting the password so that I can download applets required for running some files. Is there a solution?


So I'm trying to test to see if my deckOfCards Array is going to print out properly. Here is the code   public class Deck {     private static final String face[] = {"Ace", "Two", "Three", "Four", "Five", "Six", "Seven",                                              "Eight", "Nine", "Ten", "Jack", "Queen", "King"};     private static final String suit[] = {"Spade", "Club", "Diamond", "Heart"};     private static final Card deckOfCards[] = new Card [52];      public Deck(){         int suitCount = 0;         int faceCount = 0;         int faceValue = 0;         for(int i = 1; i < deckOfCards.length; i++){             deckOfCards[i].setSuit(suit[suitCount]);             deckOfCards[i].setFace(face[faceCount], faceValue);             suitCount++;             faceCount++;             faceValue++;             if(suitCount == 3){                 suitCount = 0;             }             if(faceCount == 12){                 faceCount = 0;             }             if(faceValue == 13){                 faceValue = 1;             }         }     }   As you can see I've defined the face and suit in an array, and I want to assign them to their proper value, however when I try to run it, I get a nullPointerException at the line deckOfCards[i].setSuit(suit[suitCount]);  I cannot seem to figure out why it giving me this error, when I debug it, it seems to initialize all the fields, yet when it gets there it crashes.

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


I've just started out with coding and I'm looking at making a simple Higher/Lower game. I have a random start number, and a new number set up when the 'higher' or 'lower' buttons are clicked. What I want to say though is....  If the person clicks the higher button: If NewNumberLbl is greater than round1numberlbl. then do something. Thing is im getting the issue of not being able to say  If {NewNumberLbl.Text > Round1NumberLbl.Text} {}   because I'm getting the error:     Error    1   Operator '>' cannot be applied to operands of type 'string' and 'string'   so how do I go about fixing this and making it into a type int?  Ps I was trying to create new int's , associate them with the ints within the random number methods and then call them instead?  HELP!  public Round1() {     InitializeComponent();     RandomNumber(0, 12);     NewNumberLbl.Visible = true; }  public void RandomNumber(int min, int max) {     int num = new Random().Next(min, max);     Round1NumberLbl.Text = num.ToString(); }  public void RandomNumber2(int min, int max) {     int num2 = new Random().Next(min, max);     NewNumberLbl.Text = num2.ToString(); }  private void Round1HBtn_Click(object sender, EventArgs e) {     //RandomNumber2(0, 12);     //if (newNumber >= originalNumber)      //{      //} }

How can you check whether a string is convertible to an int?  Let's say we have data like "House", "50", "Dog", "45.99", I want to know whether I should just use the string or use the parsed int value instead.  In JavaScript we had this  function. If the string couldn't be parsed, it would get back NaN.


When I run single-core computations on my 10-core iMac Pro, the CPU does not reach the advertised Turbo Boost of 4.5GHz but rather 3.8-3.9GHz. See plot:    I am running a Mathematica code using only one kernel (note that there are 20 kernels as the CPU supports Hyper-threading). The room temperature is 24ºC and the fans are going at the minimum speed. Anyone knows why? Note that I am not asking what Turbo Boost is but rather why it is not performing as advertised by .   it is said that the Turbo Ratios can be found using Console.app. Is this still possible in Mojave? I could not find AppleIntelCPUPowerManagement.

The new MacBook line has a new turbo boost added to the processor:     2.3GHz Quad-core Intel Core i7, Turbo Boost up to 3.3GHz   What exactly does this mean? From what I've heard, the processor can runs above the clocked speed for a short period of time.  How does it work?


So I made this simple java program using IntelliJ IDEA, and I was about to export it as .exe file but I can't find the option. How do I do this? Is it even possible?

If I have a Java source file (*.java) or a class file (*.class), how can I convert it to a .exe file?  I also need an installer for my program.


how can we prove countable function like:  If $f : X \to Y$ is a function and $A$ is a countable subset of $X$, then $f(A)$ is countable.

One of my homework problems asks to prove that if $f:X\to Y$ is a function and $A$ is a countable subset of $X$, then $f(A)$ is countable.  I believe I have a valid proof by partitioning the set A into equivalency classes based in image under $f$. Then using that partition as domain for a choice function $C_f$ back to $A$. So now the function $f$ restricted to the domain (range $C_f$) $f|_{range(C_f)}$ maps to $f(A)$ 1-1 and onto. Therefore  $$|f(A)|=|range(C_f)|\leq |A|=\aleph_0$$ $\therefore f(A)$ is a countable set. $\quad \blacksquare$  My problem is that I used the axiom of countable choice $AC_\omega$ in my proof but that isn't a part of the course I am taking. Does anyone have a simpler proof or one that does not involve Choice?


I have hosted Minecraft servers from time to time; I know how to do it.  Now suddenly people can't seem to join my server. I am talking about a LAN server now because I need to port forward if I want people from all over the world to join me. Before, everyone on my internet could join me. I used Hamachi so my friends could join me from their homes sometimes, too. Now people can't seem to join me, but I can join their servers.  This happened about 1-2 weeks ago now.  Can anyone please tell me either what is wrong or how to fix this problem? I would be so greatful if anyone could.

My LAN server won't let my cousin join me or me join my cousin. It won't show up on the multiplayer screen - it keeps saying "scanning for LAN servers" but it never finds it. I am at his house and we use different computers but it won't connect. How can I fix this?


Show that $GL_n(\mathcal{F})$ is a finite group if and only if $\mathcal{F}$ has a finite number of elements.  These are my thoughts.  The order of the group $GL_n(\mathcal{F})$ is $|GL_n(\mathcal{F})| = n^2$ because the matrices in the set are $n.n$ matrices and which would mean each matrix has $n^2$ entries.   I thought of somehow arguing $\mathcal{F}$ has $n^2$ elements which would show it's finite. Perhaps I need to show $\mathcal{F}$ is a finite. Could you clarify if I'm on the right track or not. Could you help get started on th right track on what the main idea of this proof? I'm stuck and don't if my assumptions are right and how to use them.

I would like to know if my proof below is correct.       Problem Show that $GL_n(\mathbb{F})$ is a finite group iff $\mathbb{F}$ has a finite number of elements.   Solution   If $\mathbb{F}$ is a finite field and say $\vert \mathbb{F} \vert = m$, then the set of all $n \times n$ matrices, which is a superset of $GL_n(\mathbb{F})$, where the elements comes from $\mathbb{F}$ has cardinality $m^{n^2}$. Hence, $\vert GL_n(\mathbb{F}) \vert < m^{n^2}$ and thereby $GL_n(\mathbb{F})$ is a finite group. If $GL_n(\mathbb{F})$ is a finite group, note that for every non-zero element $a \in \mathbb{F} -\{0\}$, the matrix $aI_{n \times n}\in GL_n(\mathbb{F})$, where $I_{n \times n}$ is the identity matrix with the multiplicative identity along the diagonal. This means $\vert \mathbb{F} \vert \leq GL_n(\mathbb{F}) + 1$ and thereby $\mathbb{F}$ is a finite field.     Thanks


Is there any possible way to unlock a locked question? Like, for example, say you seen an old question on Stack Exchange which is locked but they won't unlock it?

A post can be locked.   What does it mean to lock a post? Who can lock a post? When should a post be locked?


I am a Canadian citizen who is going to be visiting extended family in the US. However, on the side, I might also be applying for jobs so that I can at least get an interview.  I am highly aware that Canadian Citizen would need a TN or H1-B visas to work in the US.   However, is it ok for me to just enter the US with my Canadian passport as a visitor in order to intentionally visit extended family while, on the side, apply for jobs in order to get an interview?  ( Moreover, once the prospective employer who interviews me wants to hire me,  I can just go back up to the US-Canadian border in order to get my TN or H1-B visa with all the proper supporting documentation )    Does the aforementioned scenario sound legal?

If I am visiting the US with a tourist visa, can I look for a job in the US?


Question:  Why was this marked as a duplicate?  The referenced question asked nearly a year later than this question.  In fact I'm not even sure that they are identical at all.    I was working on a homework problem which stated:     Let $X$ be a normed linear space with two norms $\|\cdot\|_1$ and $\|\cdot\|_2$.  Assume that $\|x_n - x^1\|_1\to 0$ for some $x^1\in X$ if and only if $\|x_n - x^2\|_2\to 0$ for some $x^2\in X$.  Show that $\|\cdot\|_1$ and $\|\cdot\|_2$ are equivalent.   At first I errantly misinterpreted the question as $x_n\to x$ in $\|\cdot\|_1$ if and only if $x_n\to x$ in $\|\cdot\|_2$.  UPDATE:  I found a way to go directly from the convergence condition to equivalence of norms.  So I don't need to prove that the sequences converge to the same limit in this way (since it now follows from equivalence of norms).  I won't erase anything though, as the answer from Andres below may be helpful to someone else.  Now that I realize my mistake I'm trying to fix the proof.  Since the conclusion I'm trying to prove (that the norms are equivalent) implies that the limits in either norm must agree, I know that must also be true, even though it's not given in the question.  After failing to prove this extra condition, I am getting suspicious that it might be needed as a hypothesis after all.  Can anyone confirm or refute this?  My attempt:  Taking $\alpha = \dfrac12\min\left(\|x^1 - x^2\|_1, \|x^1 - x^2\|_2\right)$,  I let $B_{1} = \{x\in X : ||x - x^1||_{1} < \alpha\}$ and let $B_{2} = \{x\in X : ||x - x^{2}||_{2} < \alpha\}$.  Now suppose for a contradiction that there is some $x\in B_{1}\cap B_{2}$.  Then $||x - x^{1}||_{1} < \alpha$.  And $||x - x^{2}||_{2} < \alpha$.  I want to use this to prove $||x^{1} - x^{2}||$ (in either norm) is less than $2\alpha$ (which would give me a contradiction).  But I keep ending up with these floating $||x - x^{2}||_{1}$ or $||x - x^{1}||_{2}$ terms that I can't do anything with:  $ \begin{eqnarray*} ||x^{1} - x^{2}||_{1} &\leq& ||x^{1} - x||_{1} + ||x - x^{2}||_{1}\\ &<& \alpha + ||x - x^{2}||_{1} \end{eqnarray*} $  and   $ \begin{eqnarray*} ||x^{1} - x^{2}||_{2} &\leq& ||x^{1} - x||_{2} + ||x - x^{2}||_{2}\\ &<& ||x^{1} - x||_{2} + \alpha \end{eqnarray*} $

I'm working on an exercise from functional analysis.  Let $E$ be a vector space and $\|\cdot\|_1$ and $\|\cdot\|_2$ be two complete norms on $E$. Now suppose that $E$ satisfies the following property:  $\bullet$ if $(x_n)$ is a sequence in $E$ and $x,y\in E$ such that $\|x_n-x\|_1\to 0$ and $\|x_n-y\|_2\to 0$, then $x=y$.  Now we want to show that the norms $\|\cdot\|_1$ and $\|\cdot\|_2$ are equivalent.  My idea is as follows: If for any $n>0$, there is an element $x_n\in E$ such that $\|x_n\|_1>n\|x_n\|_2$. Then consider $(\frac{x_n}{\|x_n\|_1})_{n\geq 1}$. Clearly, $(\frac{x_n}{\|x_n\|_1})_{n\geq 1}$ converges to $0$. However, I cann't get a contradicition from this. Maybe my idea is wrong.   In fact, I even don't konw how to show that a Cauchy sequence in norm $\|\cdot\|_1$ is also a Cauchy sequence in norm $\|\cdot\|_2$.   Anyone can give me some hints or a counter example? Thank you very much.


echo $PATH returns a different result than the PATH variable I define in .bashrc. .profile is empty.  What else could be modifying the PATHvariable?  The directories listed are all things I would have entered (i.e., not done by software), probably after having read something online, but I don't remember where.  This question is for macOS Mojave, not OS X Mountain Lion. Yes, the answers are the same, but the questions are not.

I've recently installed  on my Mac and it's complaining that /usr/bin occurs before /usr/local/bin in my $PATH variable, meaning that system-provided programs will be used instead of those installed with Homebrew.  My .bashrc is configured in a set of separate files, as per this . This means that ~/.bash_profile looks like this:  if [ -f ~/.bashrc ]; then   source ~/.bashrc fi   ~/.bashrc looks like this:  source ~/bin/dotfiles/bashrc   and ~/bin/dotfiles/bashrc looks like this:  . ~/bin/dotfiles/bash/env . ~/bin/dotfiles/bash/config . ~/bin/dotfiles/bash/aliases   ~/bin/dotfiles/bash/env, which is where I set my $PATH variable, looks like this:  export EDITOR="kom" export PATH=some/path/at/start:usr/local/bin:/Users/jim/pear/bin:~/bin:/Users/jim/.gem/ruby/1.8/bin:/Users/jim/bin/bashscripts:some/path/at/end:$PATH   I've added some/path/at/start and some/path/at/end for debugging purposes, since when I try echo $PATH I get this:  /opt/local/bin:/opt/local/sbin:/Users/jim/bin:/opt/local/bin:/opt/local/sbin:some/path/at/start:usr/local/bin:/Users/jim/pear/bin:/Users/jim/bin:/Users/jim/.gem/ruby/1.8/bin:/Users/jim/bin/bashscripts:some/path/at/end:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin  That is, there's a load of other stuff being loaded into the $PATH variable that I can't control in the configuration I've outlined above. Any ideas as to where this stuff is loaded from, so that I can go about changing it and moving /usr/local/bin before /usr/bin?


Untill now I used everytime to filter, grep command  [root@host tests]# cat e 1 2 3 4 5 [root@host tests]# cat e | grep -Ev '2|3' > filtered.txt  [root@host tests]# cat filtered.txt 1 4 5 [root@host tests]#   But right now I have a large file that needs to be filtered with hundred of strings from another file. How can I do it?

I have a couple of big text files and in the file UNIQS.txt I have a list of strings to grep from another file. The code I use is  grep -f UNIQS.txt EEP_VSL.uniqs.sam > UNIQ_templates.sam   which does nothing - the file generated is empty. But when I do  grep -F -f UNIQS.txt EEP_VSL.uniqs.sam > UNIQ_templates.sam   it works correctly. This confuses me because I didn't think grep would interpret the entries in UNIQS.txt as regexp patterns without quotes and slashes and so on being in the file (which there aren't). Is it the case in general that if you are getting the patterns from a file then it will automatically think that they are regexp patterns?  Edit: In the UNIQS.txt file, there are newline separated strings of the form  HWI-ST365:215:D0GH0ACXX:2:1101:10034:186783   (called template names) and the file EEP_VSL... tab separated columns, with about 14 columns and the first column is the template name, so basically I want to extract the line corresponding to each template in the file.


If I allow two bodies of different masses to fall freely from same height towards the earth, how can I prove that the acceleration produced in both was constant and equal to gravity.

I'm far from being a physics expert and figured this would be a good place to ask a beginner question that has been confusing me for some time.  According to Galileo, two bodies of different masses, dropped from the same height, will touch the floor at the same time in the absence of air resistance.  BUT Newton's second law states that $a = F/m$, with $a$ the acceleration of a particle, $m$ its mass and $F$ the sum of forces applied to it.  I understand that acceleration represents a variation of velocity and velocity represents a variation of position. I don't comprehend why the mass, which is seemingly affecting the acceleration, does not affect the "time of impact".  Can someone explain this to me? I feel pretty dumb right now :)


Say there are projectiles aimed at a monk that don’t quite beat the AC, leading to a missed attack, but the roll was close to hitting (only falling short by 3-5).  Can monk use Deflect Missiles to catch the projectiles and throw them back at the attacker in a new Attack action?

The description of the monk's Deflect Missiles feature says:     [...] you can use your reaction to deflect or catch the missile when you are hit by a ranged weapon attack.   If the attacker misses with the attack roll, am I able to use Deflect Missiles (hence, catch the projectile)? Or does the description imply otherwise? What if I want to catch the projectile intentionally?


I saw a comment by Asaf Karagila a while back that remarked on the elements of $\pi$.  I'm aware of how natural numbers get said to have elements in set theory, such as $3$ having the elements $\{\}, \{\{\}\}, \{\{\}, \{\{\}\}\} \}$.  This doesn't quite make it clear to me how rational numbers have elements also, but I'll forego that here. It seems even less clear to me that a number like $\pi$ or $e$ would have elements.  I thought for a moment that using the terms of an infinite series used to compute $e$ might work, but on further reflection this seems suspicious, since it seems that different non-terminating series could get used to compute $e$, as holds for $\pi$. What are the elements of $e$?

This question is essentially a paraphrase of a  (deleted) question, which talks about a comment by Asaf Karagila about the "elements of $\pi$".  I'm aware of how natural numbers can be , so for example $3$ may be viewed as the set $\{\:\emptyset, \{\emptyset\}, \{\emptyset, \{\emptyset\}\}\:\}$, so has elements $\emptyset, \{\emptyset\}, \{\emptyset, \{\emptyset\}\}$. This seems pretty concrete and natural. I can see that we can adapt this to deal with the integers, by for example adding in a second empty set as a "marker" element (so $-3$ corresponds to $\{\:\emptyset, \emptyset, \{\emptyset\}, \{\emptyset, \{\emptyset\}\}\:\}$). I can also see that we can adapt this "marker" idea to deal with the rational numbers (which are pairs of integers, and we "mark" the top one and the bottom one in a certain way). However, I am already getting nervous here as this seems much more synthetic than how we viewed the natural numbers. Anyway. It not clear to me how a number like $\pi$ or $e$ can have elements. One way might be to view these numbers as limits of sequences, and so as lists of rational numbers. However, this seems suspicious as these numbers are limits of multiples sequences, so this does not give me a canonical set which represents these numbers, but instead a family of sets. Is this OK, or is my reasoning broken? So what I want to ask is:  What are the elements of $e$?  Or, more subtly, does this question make sense, or should we remove the word "the" from it?


Maybe someone can help me with this. I have a MYSQL table with first name and last name. Some rows were added with last name in the first name column and first name in the last name column. How can I flip these. I tried a simple update SET firstname = lastname, lastname = firstname but that doesn't work. Any help would be great.

I have a MySQL table with coordinates, the column names are X and Y. Now I want to swap the column values in this table, so that X becomes Y and Y becomes X. The most apparent solution would be renaming the columns, but I don't want to make structure changes since I don't necessarily have permissions to do that.  Is this possible to do with UPDATE in some way? UPDATE table SET X=Y, Y=X obviously won't do what I want.    Edit: Please note that my restriction on permissions, mentioned above, effectively prevents the use of ALTER TABLE or other commands that change the table/database structure. Renaming columns or adding new ones are unfortunately not options.


I'm stuck with one problem of my homework:   "Show that $\phi\left(t\right) = {\rm e}^{−\left\vert\,t\,\right\vert^{\,\alpha}}\,, t \in {\mathbb R}$, is a characteristic function only for $0 \leq \alpha \leq 2$".  I'm trying with Polya's criterion but I cannot use it since the second derivative depends on t and it shouldn't $\left(~\mbox{it should be bigger than zero on}\ {\mathbb R}_{+}~\right)$. So, i tried with Bochner’s theorem, and again I cannot understand why it should be positive definite only for 0 ≤ α ≤ 2.   Could someone give me an idea on how to solve this problem?  Infinitely thanks

I'm preparing a lecture on stable distributions, and I'm trying to find a simple explanation of the following fact.  Suppose we are trying to come up with stable distributions.  From the definition, it's clear that a distribution is stable iff its characteristic function $\phi$  satisfies $\phi(t)^n = e^{i t b_n} \phi(a_n t)$.  The normal distribution, with chf $\phi(t) = e^{-t^2/2}$ clearly satisfies this with $b_n = 0$, $a_n = \sqrt{n}$.  This suggests that we look for distributions with chfs of the form $\phi(t) = e^{-c |t|^\alpha}$.  For $0 \le \alpha \le 2$, this is indeed a chf, and there is a nice proof in Durrett's book, constructing it as a weak limit using Lévy's continuity theorem.  But:     For $\alpha > 2$,  is there a simple reason why $\phi(t) = e^{-c |t|^\alpha}$ cannot be a chf?   Breiman's Probability proves a general formula for the chf of a stable distribution, using a representation formula for infinitely divisible distributions, but it's  more work  than I want to do for this.


This code works even though contactID is not in scope at the time of the query. Can anyone explain what is going on here?  String query = 'SELECT Id FROM Contact WHERE '; if (true) {     String contactID = '0031C00002s6r7aQAA';     query+='Id=:contactID'; } List<Contact> cons = (List<Contact>)Database.query(query); System.assertEquals(1,cons.size(),'1 contact');

After I posted this question, I found a similar post that seemed to answer it: . I'll leave this in place for now, as I am not sure how to mark my own question as a duplicate  In attempting to debug a SOQL query error, I encountered a strange behavior with Database.query and bind variables. Specifically, when I run this code:  String userQuery = 'SELECT Id FROM User'; if (true) {     List<String> firstNames = new List<String>{'James','Joe'};     userQuery += ' WHERE FirstName IN :firstNames'; } Database.query(userQuery);   the Database.query statement executes with no errors, despite the fact that the variable firstNames does not exist in its context. However, when I add an else clause:  String userQuery = 'SELECT Id FROM User'; if (true) {     List<String> firstNames = new List<String>{'James','Joe'};     userQuery += ' WHERE FirstName IN :firstNames'; } else {     List<String> firstNames; } Database.query(userQuery);   I receive a null object reference exception. It seems like Salesforce is checking to see if the variable is only declared once beforehand and, if so, uses its value in the context it was declared. This seems strange to me, so I was wondering if anybody here has any insight into what is going on under the hood.


Harry, Hermione and Ron possess a reserve of polyjuice potion when they go in search of Horcruxes.  It takes months and they use it three times:   to go to the Ministry of Magic, to go to Godric's Hollow, to go to Gringotts.   Would this mean the potion always keeps its properties/potential  as long as you haven't added the hair of the person you're turning into.

Do we know how long potions (in general, or at least specific ones) are potent (no pun intended) in Harry Potter canon?  E.g. do they last a couple of hours? Minutes? Years?   I seem to vaguely remember some comments of Snape's about Wolfesbane potion therfore I think at least some information exists.


The machine was pretty slow already. However I decided to execute sudo apt-get update.  However the update stopped at 90% updating some trigger.  So I decided to log out and re login with user. However the system didn't let me log on any more.  So I decided to log on with an alternative user and triggered the update again, same message:   Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?   Then I tried a shutdown. Now I just see the Ubuntu logo and white/red dots moving from left to right.  This machine is important for me, what's the best thing to do for me now?  Should I just switch off power and reboot?  Your help is very much appreciated!

I get this error when trying to use apt-get:  E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?     How can I fix this?


My 32 bit debian (version: Debian GNU/Linux 8) installation is suddenly giving me the following messages when I run apt-get update.  W: Failed to fetch http://ftp.nl.debian.org/debian/dists/jessie-updates/InRelease  Unable to find expected entry 'main/binary-i386/Packages' in Release file (Wrong sources.list entry or malformed file)  E: Some index files failed to download. They have been ignored, or old ones used instead.   The funny part is that I did not add any additional sources. Here is my /etc/apt/sources.list file. It's default.  #  # deb cdrom:[Debian GNU/Linux 8.7.1 _Jessie_ - Official i386 NETINST Binary-1 20170116-10:07]/ jessie main  #deb cdrom:[Debian GNU/Linux 8.7.1 _Jessie_ - Official i386 NETINST Binary-1 20170116-10:07]/ jessie main  deb http://ftp.nl.debian.org/debian/ jessie main deb-src http://ftp.nl.debian.org/debian/ jessie main  deb http://security.debian.org/ jessie/updates main deb-src http://security.debian.org/ jessie/updates main  # jessie-updates, previously known as 'volatile' deb http://ftp.nl.debian.org/debian/ jessie-updates main   Now I don't know how to solve this. Can this file somehow gets corrupted? Can I revert it back? What should I do to fix this?

I'm using a docker image as a base for my own development that adds the jessie backports repository in its Dockerfile and uses that to install a dependency. This image uses the following command to add the repository:  echo "deb http://ftp.debian.org/debian jessie-backports main" >> /etc/apt/sources.list   The problem is that fetching packages from the backports repository now  fails with the following error (this used to work previously):  W: Failed to fetch http://ftp.debian.org/debian/dists/jessie-backports/main/binary-amd64/Packages 404  Not Found  W: Failed to fetch http://deb.debian.org/debian/dists/jessie-updates/main/binary-amd64/Packages  404  Not Found   I looked on that server, and those paths are indeed not present there.  I tried to figure out on the Debian backports site whether this particular repository should still be available, and I didn't find any indication that this was deprecated or something like that.  Is this a temporary issue with the repository, or is the jessie-backports repository not available anymore? And if this is not a temporary issue, what options do I have to use this or an equivalent repository without upgrading to the newer Debian stable version?


I do understand that Lorentz transformations became as a rotation of coordinates as of a hyperbolic rotation. But what is its advantage over real vector? What is the new thing that it introduces and what problems does it fix or ease?

When I learned about the Minkowski Space and it's coordinates, it was explained such that the metric turns out to be $$ ds^{2} = -(c^{2}dx^{0})^{2} +(dx^{1})^{2} + (dx^{2})^{2} + (dx^{3})^{2}   $$ where $ x^0,x^1,x^2,x^3 $ come from $ x^{\mu} : \mu = 0,1,2,3 $, and $ c $ is the speed of light. The first resource I had access to--I have to do a bit of digging for the exact paper--of course addressed that this invariant takes the tensor form: $$ ds^2 = g_{\mu \nu}dx^{\mu}dx^{\nu} $$ as well. This two things I've seen in all of my texts and online resources regarding resources. The element in question that varies between authors, is the time coordinate, $ x^0 $. When it was first explained to me, it was using the standard Cartesian representation for the spatial portion of the coordinates, and the time coordinate was labeled as $ x^0 = ict $. Squaring gives $ (x^0)^2 = -c^2t^2 $, and applying differential calculus, we get $ (dx^0)^2 = -c^2dt^2 $. Sensible and expected to have the tensor formula spit out the Minkowski Metric. The author then later explicitly states the coordinates are $ x^0 = ict, x^1=x,x^2=y,$ and $x^3 = z$.  My questions is then, why is it most authors on the subject omit the imaginary unit on the time coordinate? For example, .   The only reason I can fathom omission is if the author is using metric signature $ [+,-,-,-] $, where I started off learning the theory with signature $ [-,+,+,+] $ which may be the reason seeing the time coord with no imaginary unit seems dissonant to me. All help appreciated!  Edit: After reading the other answers, my questions is now one of why and how (mathematically) do we obtain the Minkowski Metric Signature. More specifically the one element with a different sign.


One nice feature would be if the source code was automatically hidden when the question is too big, and clicking on something be able to make the code visible.  In  people are asking a lot of data, so the question is currently huge and hard to get an overview. This feature would allow people to see the question from a high-level point-of-view, and see the code as they feel they should.

It would be great to have the option to fold code snippets, entire questions and answer posts on a user basis and allow defining some generic foldable regions within the question/answer editor.  Non generic folding info could be stored in cookies perhaps to move the storage/processing requirement to the client side.  Definable folding can take any free and safe HTML tag or other multi character trick (<>Fold this<>)


i try to install Novell Designer 4.0.1 on Ubuntu.  But i get the error message:  Preparing to install... Extracting the JRE from the installer archive... Unpacking the JRE... Extracting the installation resources from the installer archive... Configuring the installer for this system's environment...  Launching installer...  ./install: 2468: exec: /tmp/install.dir.4347/Linux/resource/jre/bin/java: not found   What could i do to get the installation working?

After running:  sudo add-apt-repository ppa:ferramroberto/java sudo apt-get update sudo apt-get install sun-java6-jre sun-java6-plugin sun-java6-fonts   I try to setup a software sybase sudo ./setup.bin but I get the following problem:  exec: 2508: /tmp/install.dir.30906/Linux/resource/jre/bin/java: not found


Iam looking at the datasheet of a dual MOSFET (.) which contains 2 drain pins and 1 source pin for each MOSFET.  What is the purpose of having 2 drains, when there is only 1 source pin?  Is it for increased current capability? Since drain current is same as source current, shouldn't the source pin be also 2 pins?

The  comes in a 6-pin package, 4 of which are connected to the drain, and only 1 to the source. Why this difference? The source sees the same current as the drain, doesn't it?


I am doing a simple operation of a multiplication and a division in the following manner in Java.  100 * 44907280.59 / 44907280.59;   I was expecting it to give me 100, but it was giving me 99.999999....  I tried searching Google for the related help, but I could not get any. And if I remove the multiplication part and just divide like below  44907280.59 / 44907280.59;   the result I see is 1.0  Can someone please explain me what is going on here?

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


I found this inequality on twitter and I can't seem to prove the statement.  Prove that for $a,b,c > 0$ that   $$ \frac{a+b+c}{2} \geq \frac{ab}{a+b} + \frac{ac}{a+c} + \frac{bc}{b+c} $$  After an hour (and a crick in my neck) I've only been able to turn it into   $$ a^3(b+c)+b^3(a+c)+c^3(a+b)-2abc(a+b+c) \geq 0 $$  and I'm not even sure if that's much better.

If $a,b,c$ are positive real numbers, not all equal, prove that  $$\dfrac{bc}{b+c}+\dfrac{ca}{c+a}+\dfrac{ab}{a+b}<\dfrac{a+b+c}{2}$$  Progress: $\frac{bc}{b+c}-\frac{b+c}{2}=$


Text gets overlaid on top of itself and unreadable when scrolling the "Similar questions" dropdown when Asking a question.  Steps to reproduce:   Start typing the question title. "Similar questions" list gets populated. Scroll the "Similar questions" list - OK Go back to the question title and refine it. Scroll the "Similar questions" list - text is overlaid when scrolled!?   Tested Firefox v72.0.2 and v73.0  Doesn't seem to be a problem in Chrome/Opera.  Close and reopen the dropdown does resolve the issue.

Originally posted on Stack Overflow:   Requirements to reproduce:  Windows 7 x64  Firefox 71.0 x64  Steps to reproduce:   Go to the ask question section Write something to the title field Start scrolling similar questions Change the title field Start scrolling the similar questions again


I got this note from a literary agent and am curious about usage of the word suicide. I had written, "my father was a suicide." Which sounds a little archaic but wanted to avoid saying "committed suicide" and/or "Killed himself." She wrote: Suicide should not be used in place of personhood – you don’t say “was a car accident” or “was an aneurysm” What do you think?

One of the examples in my English composition book (for learning to write my language's sentences in English) was "Why he committed suicide under such a good circumstance is an unsolved question.", but what I would have written would have been "Why he suicided...".  What's the difference between "commit suicide" and "suicide"?  (I think I saw 'commit suicide' more than just 'suicide', and the spell checker of Google Chrome says that 'suicided' is not a  word, even though I think it .)


So I've recently tried out marshmallow and kind of like the adopted storage idea as I never find myself removing the micro sdcard.   I'm curious though if there is a smooth way to upgrade to a bigger or better sdcard later on. Right now I would probably attempt to rsync with adb to a PC and insert a new card, format it and rsync back. I'm not very confident this will work however.     Perhaps it's faster to mount both cards in linux using this method:  and sync them there.

I've got a Moto G 2014 LTE running CM13. When I found out about the whole 'adopt SD card as internal storage' thing, I was quite excited, as the actual internal storage on this phone is tiny. I set up a 16gb micro SD, the biggest I had at the time, and have been using it with minimal problems.  Fast-forward to this day, and I now have a 64gb micro SD that I want to use instead of the 16gb one. However, I'm at a loss as to the best way to copy the data over onto the new one, or if it's even possible. The ideas I've got so far include:   Titanium Backup all [system] apps, factory reset, format new SD and then restore (should work, but a massive pain) NANDroid the SD card onto a USB OTG stick, then restore to the new one (pretty sure this is a bad idea and won't work, but...) Copy all the stuff onto my computer via my phone through a file manager of some sort (I have a linux/linux/windows triple boot, so file format isn't a problem), format the new SD into phone, and copy back (can't be that simple, can it? Hidden/inaccessible files?) Copy the files onto USB OTG with a root file explorer app, reformat the SD as portable, format the new one as adopted, and then copy them back (could work, except for the point below)  with the command adb shell sm set-force-adoptable true, use a root browser to copy all the data over from the old SD, format the old SD as external and remove it, and take the new SD and put it in the SD card slot (seems overly complicated, and also suffers the below pitfall)   The other thing that worries me is mount points: will the apps with externally-stored data know to look at the new SD card for it? Will I have to remount it in a specific location with the shell each boot (or use an init.d script perhaps)? I suppose that it can always be accessed through /sdcard or /storage/emulated/0, but I'm not 100% sure what goes on behind the scenes.  I've got recent NANDroid backups, so if anyone can eliminate the options that definitely won't work (or say which one[s] probably will), I can try them and report back in case someone stumbles across this question in the future.  EDIT: So, my phone further bit the dust and got to the point where it got into a pretty major bootloop. Ended up having to flash a whole new ROM. As such, I probably won't be able to test the full image/decryption/etc. method that I was originally planning. However, I will write up what I've discovered so far in case anyone wants to take up this particular method in the future:   Image the old SD with dd as follows: sudo dd if=/dev/mmcblk0 of=~/SDCardBackup.img, where /dev/mmcblk0 is the location of the sd card as obtainable through lsblk Restore the image you just made to the NEW sd card : sudo dd bs=4M if=~/SDCardBackup.img of=/dev/mmcblk0 (you may have to unmount it first) From here on in, I was following  (thanks @beeshyams!) tutorial, which explains the next steps way better than I ever could have done. The plan was to decrypt the storage and resize the main partition with gparted. I had no idea whether it would work or not, but I felt it was worth a try. However, when I came to run the actual decryption command using the key I'd extracted, I got an error (which I believe was my shoddy linux skills more than anything).   As I say, I have no idea if the above method would work or not even if everything did go to plan. Also, feel free to correct any of my commands above if I mis-typed them (I'm on Windows currently, so this is all from memory.) If this info helps anyone, then good. But until then,  should work fine.  Thanks, Jackdafish


I m a citizen of india..I want to go pashupatinath darshan kathmandu by flight with my family and return from there by flight I don't have a passport ..I have a driving licence (maharashtra) And pan card ,adhaar card also have..my wife's have aadhar card and pan card ..my child's aadhar card and school id..4 years old My father's age 74 they have voter ID card and aadhar card pan card..my mother 55 also have voter ID and aadhar card pan card Can I travel to pashupatinath mandir.kathmandu by flight in April..

I'm a citizen of India and I'm travelling to Nepal by air. Is an Aadhaar Card a valid document used for travelling to Nepal by air?


Someone thought that in both AotC and RotS R2-D2 should have rockets built into his side legs, but if he still had the thrusters in ANH and beyond he never visibly used them- was there ever an explanation to why?

In :     Artoo butts the golden droid over the edge and steps off himself, tumbling toward the sand.   But in :     ARTOO uses his rocket jets to fly up and into the factory.   Why didn't R2-D2 use his jets in RotJ instead of ending feet up in the sand?  Update: I am looking for an in-universe explanation.


I'd like to show an image (png, preferably) in my panel. Does anyone know if this is supported through labels or template_XX UIPanels?

I have created an add-on but I can't apply my own icon to the operators in this add-on.   Is there any easy way to implement this?   Or do I need to add the icon to an SVG file?


No info available in datasheet  After going through the answers I got some additional doubts:  Why is the sense pin only there for high side MOSFET? Why is the current rating different for high side and low side MOSFET in datsheet?

On MOSFETs with multiple source pins, is the so-called "Kelvin-connected source pin" connected any different internally? Or is it just like every other source pin?   EDIT: Just to be clear, I am not asking what the Kelvin connection is for. I'm asking whether it is physically implemented any differently than the other source pins or whether it is just an extra regular, old source pin.


I'm using Ubuntu 16.04 in VirtualBox.  I would like to unpack a tar.gz in my root (/) folder but I can't paste any file in it or even create a new folder in the file browser.  I can do that with command line when I use sudo but when I use right click I don't have access to create new folder or paste... I have sudo privilege so I don't really understand.   I think it can by done with terminal because with mkdir I've been able to create a folder, but I can't write in this folder.   Does anybody have any clue about it?

I've got a problem with Nautilus in Ubuntu 12.04 LTS.  When I run the command gksu nautilus /, the password ask box appears and I type my super-user password, then the password box disappears and Nautilus is not opened.  When I try to open Nautilus as a normal user in with the command nautilus, the folder is opened.  When I try in terminal   $ sudo nautilus   I got the following error  $ sudo nautilus /  ** (nautilus:8523): WARNING **: Command line `dbus-launch --autolaunch=2c8ce9b7da2257c2609b749700000007 --binary-syntax --close-stderr' exited with non-zero exit status 1: Autolaunch error: X11 initialization failed.\n Could not parse arguments: Cannot open display:   How can I fix this error?


I have written a file writer and a file reader class in which you put data into and use it by file reader in another class methods. The type of my variable defined in Account class is integer.To write it in file, I change the type as String(because I have my other variables as String)...when I want to use that variable in my method in Account class, I can not compare it with the local variable(which is filled by user).It gives me a "NullPointerException" error. Can anyone help me with this?(The code is just a summary)  public class Account {     int PIN; public void meth_name(){     int pin;      if(PIN == pin)       } }  public class filewriter {      public void met_name(){         ....         fw.write("PIN: "+ Integer.toString(PIN));     } }

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?


Something set up firefox on windows machine to start and go to certain url as user logins into system.   In process explorer I see, that Firefox is started as "firefox.exe -osint -url "somenastything" and cmd window flashing briefly as I login. I can see pid of the parent, which is (4300) or something. I enabled event history in task scheduler, but from the logs, I don't see process with corresponding pid. How does this thing managed to auto-start then?

Hi and sorry for the ambiguous title...  I have a few programs that should run at startup which are 'properly' configured to do so via adding shortcuts to the startup directory:  C:\Users\[me]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup  However I have (at least) 4 programs which are also starting up, which I can't find where they are configured or how to disable them.  I have tried to find them in the above folder, as well as in the 'startup' section of 'msconfig'.  The programs include:   Skype (for which I have disabled 'start when windows starts' in its options) Thunderbird (for which I cannot find any option to run-at-startup) Task manager (as above) and some anonymous call to javaw (can't find any more details but it fails anyway)   The other strange thing is that it seems like these (at least skype and thunderbird) are running 'as administrator' ... i have deduced this because I am unable to use the file-drag-and-drop feature in both (which is a known problem when running 'as administrator').  If someone could guide me to where these extra programs are configured to run-at-startup I would be very greatful!  ps. my user account has the administrator role.  EDIT: preferrably without another 3rd party tool...


I install ubuntu 14.04 on my old laptop but wifi doesn't work and when i use fn+f2 keys for wifi nothing change. sometime when i boot xp and use wifi and boot ubuntu again wifi led still run but wifi doesnt work.  I can connect to net with ethernet cable  I try some instruction in some  site but nothing change like:   sudo apt-get remove --purge bcmwl-kernel-source  sudo apt-get install linux-firmware-nonfree   please help me sorry for my bad english.  lspci -knn | grep Net -A2 05:00.0 Network controller [0280]: Broadcom Corporation BCM4311 802.11b/g   WLAN [14e4:4311] (rev 01) Subsystem: Dell Wireless 1390 WLAN Mini-Card [1028:0007] Kernel driver in use: b43-pci-bridge

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


When i try to click on the button several time then i encountered this error. Below are the error in logcat: E/AndroidRuntime: FATAL EXCEPTION: main     Process: com.example.huiiy.myapplication, PID: 3933     java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.start()' on a null object reference         at com.example.huiiy.myapplication.Activity9$13.onClick(Activity9.java:288)         at android.view.View.performClick(View.java:5712)         at android.view.View$PerformClick.run(View.java:22514)         at android.os.Handler.handleCallback(Handler.java:751)         at android.os.Handler.dispatchMessage(Handler.java:95)         at android.os.Looper.loop(Looper.java:154)         at android.app.ActivityThread.main(ActivityThread.java:6141)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)  Below are the coding of my application:     iv_33.setOnClickListener(new View.OnClickListener() {         @Override         public void onClick(View view) {             MediaPlayer ivbsound = new MediaPlayer();             ivbsound = MediaPlayer.create(Activity9.this,R.raw.ivbutton);             //          MediaPlayer ivbsound = MediaPlayer.create(Activity9.this,R.raw.ivbutton);             ivbsound.start();             int theCard = Integer.parseInt((String) view.getTag());             doStuff(iv_33, theCard);         }     });


In the following sentence, shouldn't "among" be used instead of "between?"  It has been determined between all three departments that the science department is the most appropriate department to be in charge of this assignment.

Today I was cut off in the middle of the following sentence:     Between Cook, Strauss, and Pietersen—   My friend said I was wrong. He said that for more than two entities, among/amongst are used, and that between is only for two entities.   I vaguely remember some rule like this, but I asked him to hear the whole sentence, which was:     Between Cook, Strauss, and Pietersen, they’ve notched up 56 centuries in Test cricket.   Should I have used among here? Seems correct to me to use between, but my friend was certain.   Another friend pointed out the following sentence:     I’m still choosing between Harvard, Yale, and MIT.    Certainly among doesn’t seem to fit here, and she, to me, was correct in using between.


Can you recommend to me good references on this action? From basics to more advanced stuff.

I'm interested in learning about topological QFT including Chern Simons theory, Jones polynomial, Donaldson theory and Floer homology - basically the kind of things Witten worked on in the 80s. I'm looking for pedagogical reviews rather than original articles. Though these things sit at the interface of mathematics and physics I'm interested in them more as a physics student. I remember someone asking for a suggested . The suggested papers were almost uniformly rigorous mathematics written by mathematicians. I am not looking for something like that.


Going out to bulk buy tomorrow and stock up on a few things Butter being one of many. How long can butter be stored in the refrigerator? We want to maximize our stock but not waste anything.

How do I know if a given food or ingredient I have is still good, or if I should discard it?  How can I best preserve a food or ingredient?     This broad question is intended as a "general reference" question to quickly answer many how long will food keep for? questions. Please feel free to edit this question to expand and clarify as needed.


I'm seeing in GWT a bunch of request of removal of pages, which weren't submitted from someone in my organization. I'm referring to the tab under Google Index->Remove URLs. Does it include any user-requested removals? How does someone submit such a request? It allows me to cancel a request (which I didn't submit in the first place) how does that make any sense?

Take a look at the following screenshot I took from Google Webmaster Tools "Remove URLs" page:   None of these were performed by me or others who have access to GWT.  How do these removal requests happen without us doing any requests?  Why is that happening?  How to stop that or is there any point in stopping that?


I am facing a weird Java behavior in following code (it lists folder with 1 sub folder, 2 .mp4 files, and 1 .mp3 file). I am trying to asign different icons to video and other files:      private void fill(File f) {     File[]dirs = f.listFiles();      this.setTitle("Current Dir: "+f.getName());      List<Item> dir = new ArrayList<Item>();      List<Item> fls = new ArrayList<Item>();      try{          for(File ff: dirs)          {              Date lastModDate = new Date(ff.lastModified());             DateFormat formater = DateFormat.getDateTimeInstance();             String date_modify = formater.format(lastModDate);             if(ff.isDirectory()){                   File[] fbuf = ff.listFiles();                 int buf = 0;                 if(fbuf != null){                      buf = fbuf.length;                 }                  else buf = 0;                  String num_item = String.valueOf(buf);                 if(buf == 0) num_item = num_item + " item";                 else num_item = num_item + " items";                  //String formated = lastModDate.toString();                 dir.add(new Item(ff.getName(),num_item,date_modify,ff.getAbsolutePath(),"directory_icon"));              }             else             {                 String ext = "";                  ext=getFileExtension(ff);                 Log.d("Zox","'"+ext+"'");                 if(ext!="mp4"){                     Log.d("Zox","'"+ext+"'");                     Log.d("Zox","FU");                 }                 else {                     fls.add(new Item(ff.getName(), ff.length() + " Byte", date_modify, ff.getAbsolutePath(), "file_icon"));                 }             }          }   I get the following output:  08-09 18:54:08.219 11057-11057/com.piandro D/Zox: 'mp4'  08-09 18:54:08.219 11057-11057/com.piandro D/Zox: 'mp4'  08-09 18:54:08.219 11057-11057/com.piandro D/Zox: FU  08-09 18:54:08.219 11057-11057/com.piandro D/Zox: 'mp4'  08-09 18:54:08.219 11057-11057/com.piandro D/Zox: 'mp4'  08-09 18:54:08.219 11057-11057/com.piandro D/Zox: FU  08-09 18:54:08.229 11057-11057/com.piandro D/Zox: 'mp3'  08-09 18:54:08.229 11057-11057/com.piandro D/Zox: 'mp3'  08-09 18:54:08.229 11057-11057/com.piandro D/Zox: FU  The key code part is:              String ext = "";              ext=getFileExtension(ff);             Log.d("Zox","'"+ext+"'");             if(ext!="mp4"){                 Log.d("Zox","'"+ext+"'");                 Log.d("Zox","FU");             }             else {                 fls.add(new Item(ff.getName(), ff.length() + " Byte", date_modify, ff.getAbsolutePath(), "file_icon"));             }   and condition and action are nonsense, just for debugging purpose. Why Java doesn't recognize String match?

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


Moderators can undelete comments that have been deleted.  This is useful; it allows us to purge a big pile of comments and then undelete the two that added value.  It also lets us undo accidents (hello, moderating on a phone :-) ).  There is one exception to this: if the author of a comment deleted it, mods can't undelete.  That makes sense; we allow people to take back their words without risk of having them come back later.  I've just bumped into a second exception: I came across a comment that was deleted by a single flag, because the comment contained a magic keyword.  The comment also contained useful information, so I tried to undelete it -- and couldn't.  The author of the comment wanted it there (this wasn't a retraction).  A moderator wanted it there.  But a user who is neither was able to prevent me from recovering the comment.  The regular expression behind this expedited flag-deletion is not perfect.  It can't be; it's only a regex.  Sometimes human judgement is needed.  Not all uses of "accept" are bad, and not all occurrences of "+1" mean there's not also something valuable in the comment.  Some users are actively hunting for these comments and flagging them.  They're using scripts, not their own judgement, but even if they were looking at individual comments, they sometimes make mistakes.  Please fix this.

No, you can't hocus pocus a comment to be banished to the outer realms of the ether, but there is a short list of words that, if contained within a comment, cause the comment to be removed after a single flag.  Remember when we had a problem with folks brow beating other users about their accept rate? Well, guess what word was tossed into the magic cauldron? That's right, accept(ing).  Earlier today on Judaism, someone wrote a comment that began with:     I'm not accepting that [point totally irrelevant to the green check mark]   It was flagged, and deleted instantly. This isn't a huge problem in and of itself, though we might want to examine if we still need to fire on that particular phrase - the problem here is that a moderator could not undelete the comment. The only time a mod should be preventing from undeleting a comment is if the comment author was the one that deleted it.  Tagging this as a bug as I'm reasonably certain it's just an oversight.  To reproduce:   Leave a comment with a magic word Flag it as a non mod Preform the diamonding ritual, channel the cosmos as a non-developer Weep, as the ashes of your toils lay in ruins before you, powerless to return them to former glory.   Saying please and reloading the page had no effect, so I don't think this is due to the INTERCAL rewrite that we just finished.   Note that this (and the linked question) talk about the "accept" example, but the bug report is about mods not being able to undelete.  Removing "accept" from the list of magic words doesn't fix this bug, just changes one way it's triggered.


I want to create a Virtual Machine of macOS High Sierra using VirtualBox 6.1 on my  mid 2014 MacBook Pro that's running macOS.   How do I do that?   I already installed VirtualBox.  How do I create the VM of macOS High Sierra now?

I’m trying to install macOS Sierra on VirtualBox, but can’t seem to make it work. For reference, here are the steps I took.   Downloaded the Install macOS Sierra app from the App Store. Used the inbuilt media creation executable, CreateInstallMedia on a disk image. Created a new VM with the default settings for an OS X El Capitan, plus 128 VRAM. Since VirtualBox refused to accept the DMG, I tried splicing out the InstallESD. VirtualBox now accepted it, but wouldn’t boot. I tried to boot through rEFInd, but still no luck. I tried to patch it both ways (base system and ESD) with iesd. No luck. When booting to GParted LiveCD, it flat-out refused to discover any of the installer CDs.   How can I patch the installer to work with VirtualBox? I don’t want to use pre-patched versions of either the installer or an existing installation, as though to avoid piracy.


don't get mad please as I always don't share a MWE. Actually, I am working on a LaTeX file which has several themes associated to it and so it is a bit difficult to put up a MWE.  What I wanted to inquire is that how to Slightly Tab a complete paragraph horizontally. I am using \quad and it just tab the first line but not the rest of the lines of the paragraph.

How do I indent a whole paragraph at the same distance from my left margin, with the simplest command or environment?


I know that similar questions have already been asked and there are answers describing that in the situations describe below forward declaration is not enough. However, these answers do NOT tell WHY it is not enough. Therefore, I don't think that this is a duplicated question.  I have some difficulties to understand why the compiler has to see the definition of a data type (a foward declaration is not sufficient) in the following situation:  Let's consider we have a simple "main.cpp" as shown below, which does absolutely nothing except including the header file "MyClass.hpp"  #include <MyClass.hpp>  int main(int argc, char **argv) {     return 0; }   Now, let's consider that the content of "MyClass.hpp" looks as follows:   #include <vector>  class Data1;  class MyClass { public:     MyClass();                                      // default constructor     MyClass(MyClass const & p_other);               // copy constructor     MyClass(MyClass && p_other);                    // move constructor     ~MyClass();                                     // destructor     MyClass & operator=(MyClass const & p_rhs);     // copy assignment     MyClass & operator=(MyClass && p_rhs);          // move assignment private:     Data1 *            m_a; // forward decl. always OK     Data1              m_b; // forward decl. always not OK     std::vector<Data1> m_c; // forward decl. OK if MyClass is not instantiated };   MyClass contains several member variables:    "m_a" is a pointer to "Data1",  "m_b" is an instance of "Data1", "m_c" is a vector with elements of type "Data1".    The definition of "Data1" is neither included in "MyClass.hpp" nor in "main.cpp". It is just forward declared.  The compiler never has a problem with member variable "m_a", it doesn't require its definition for compiling "main.cpp" -- even if we would intantiate "MyClass".  Because we are not instantiating "MyClass", the compiler also doesn't have a problem with member variable "m_c". It also does not require the definition of "Data1" in this case.  However, the compiler has a problem with member variable "m_b":     Impl1.hpp:16:24: error: field 'm_b' has incomplete type 'Data1'   My simple question is: why?  Please consider that we have user-defined default constructor, copy constructor, move constructor, a user-defined destructor, and user-defined copy assigment operator and move assignment operator, i.e., the compiler doesn't have to generate code for any of these constructors/methods. So for what purpose does the compiler need to see the definition of "Data1" when compiling only "main.cpp"?  Does anybody know the answer?

I am looking for the definition of when I am allowed to do forward declaration of a class in another class's header file:  Am I allowed to do it for a base class, for a class held as a member, for a class passed to member function by reference, etc. ?