I am using this account. Today morning I have answered a question on Mathematics Stack Exchange. Suddenly my reputation dropped down. What is the reason for this issue? I am totally disappointed.   This week I was scoring nearly 500+ reputations. I lost everything.   Edit: I got a mail like below.     Hello,      I'm writing in reference to your Mathematics Stack Exchange account:            Due to clear signs of falsified accounts being used to artificially   inflate your reputation, your account has been temporarily suspended   for 7 days.      It is not fair to other users of Mathematics Stack Exchange to allow   users to gain reputation through sockpuppets.      The offending accounts have been removed and the votes invalidated.   Please refrain from this behavior in the future.      Regards, Mathematics Stack Exchange Moderation Team

My account has been , besides the following restrictions:  an account will be locked at 1 reputation the user page will have a visual indication that the account is in timed suspension, and for how long the account holder will be unable to vote, ask, answer or comment  What else does timed suspension prevent me doing? For example, can I still edit my own posts or delete content? And what is a network-wide suspension?


I'm currently creating a short document with a number of projects that are being offered by my school. However, each project has roughly 2-3 citations and are unique to each project.   More to the point, at the end of each project I would like to include a small reference section, is this possible?   Luckily the references will all be from the same .bib file but I'm still not sure where to begin.

I'm really new in using biblatex, compile the sample placed in , but what I get is    1.1 Foo    Some text [B02x ].    1.2 Bar    Some text [B02y ].   Do not get the bibliography by chapters, or the global references.  Really not remains to be done   \documentclass{report}  \usepackage[style=alphabetic]{biblatex}  \addbibresource{references.bib}  \begin{document}  \chapter{First chapter}  \section{Foo}  Some text \cite{childs_temperature}.  \printbibliography  \chapter{Second chapter}  \section{Bar}  Some text \cite{hashemian}.  \printbibliography  \newpage  \printbibliography  \end{document}   And the references.bib    @BOOK{childs_temperature,   title = {Practical Temperature Measurement},   publisher = {Butterworth - Heinemann},   year = {2001},   author = {Childs, Peter R N},   address = {Great Britain},   edition = {1},   isbn = {0 7506 5080 X}   }    @PHDTHESIS{hashemian,   author = {Hashemian, Hashem Mehrdad},   title = {Measurements of dynamic temperatures and pressures in nuclear power plants},   school = {{The University of Western Ontario}},   year = {2011},   type = {PhD {T}hesis}   }   I need to obtain references by chapter and global cited references, but i don't know how compile.


I am recording data every 0.02 seconds and my code to save this information to a tab deliminated file is producing some peculiar results where even though i am adding 0.02 on each time to the time variable it starts being slightly off (i'm aware that when rounded it is essentially the same but it bugs me). How do i get it to look like the corrected data set  output.println(time + "\t" + accelX + "\t" + accelY + "\t" + accelZ); time = time + 0.02;   the output gives me (I left out the other data as it is going in fine)  Time 0.02 0.04 0.06 0.08 0.099999994 0.1199999999   should be  Time 0.02 0.04 0.06 0.08 0.1 0.12

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


Here i have executed the following code and parsed it to date format from form.          Date formatter = new SimpleDateFormat("mm/dd/yyyy");         SimpleDateFormat newFormat = new SimpleDateFormat("yyyy/mm/dd");         Date date = null,sdate=null;         String datef = null;         try {             date =formatter.parse(datestring);             sdate = newFormat.format(date);          } catch (ParseException e) {             e.printStackTrace();         }         ps=conn.prepareStatement("INSERT INTO work_schedule (date) VALUE(?)"); // connection conn defined.     ps.setDate(1,(java.sql.Date.valueOf(sdate)));   The above code throws a null pointer exception , i tried executing query in my sql workbench query works good.  Please let me know if i have made any error in the above code.

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 have an laptop that is ~ 4 years old. It has 2 hard drives - one is used for the OS and the other for data.  I'd like to upgrade the OS drive with an SSD to make it run faster, but i was wondering whether i would have to install the OS (Windows 10) all over again, or whether there's an easier option ?

I've taken the plunge and bought an SSD and want to move my existing Windows installation over. The current hard disk is 500Gb, but I've trimmed the contents down to about ~40Gb. I'm transferring it across to a 100Gb SSD and looking for the easiest way just to copy everything across and set the SSD up as a boot device.  I've looked at a few tools like Macrium Reflect, but they don't seem able to restore to a smaller drive. Do I need to go for something like  to do this? I'm trying to avoid scary Linux-based boot utilities if possible, does anyone know of an easier way?


I need to be able to use Ubuntu on different computers with my external hard drive, with varying devices. And it needs to be a full (normal..ish) install. (No bootable+overlayfs persistence for me!)  I'll probably be using computers with an i386 architecture, but the 32/64-bit could change.  Or, I'll just hope for the best and just repart my drive and install.

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


I want to create liveUSB on part of my flash stick. I made a partition with GParted and downloaded .iso file of Ubuntu 19 from the official website to mount with gnome-disk-utility.  I noticed that the iso file has "amd64" in the name. But I intend to use this USB not only on amd computers!  Is that important? Will the live USB work on PC with Intel/other processor?

I was told that computers with more than 2 gig's memory need a 64 bit operating system to utilize all RAM.  Is the 64bit Ubuntu download really JUST for AMD processors? I am asking because the disk image I downloaded says AMD64.  So will my new Intel 2.3Ghz Core i3 Dual Core processor work with 64 bit Ubuntu?  It runs the 64bit version of Windows without any qualm.


When I plug some devices into my computer they go through the Windows "Driver Software Installation" phase.  These devices were previously plugged into my computer and drivers installed.  Why does this still happen and takes much longer than before?

Let's say I have a mouse. I plug this mouse into slot 1 out of 4 on a computer. It goes through the new device detected and all of that, which is fine. But if I come back later with the same mouse and plug it into say slot 3, it does the detecting all over again! Why is this?


How do I know how many questions I can ask per day or per month? How do I increase these limits?  I mean, at the moment, how do I know, how many more questions I can ask?  And, suppose I reached some limit -- then how do I know when it will be removed?

Is there a limit on how many questions I can ask per day? Per hour? Per other time unit?  Related Questions:


When I set in .bashrc something like:  alias="docker stop $(docker ps -aq)"   or  alias="echo $(ls -l ~)"   obviously never refreshes the command output in $(), so is an string...  So, my question is, there is any way to refresh the command output used as variable ?

From the bash manual     The rules concerning the definition and use of aliases are somewhat   confusing. Bash always reads at least one complete line of input   before executing any of the commands on that line. Aliases are   expanded when a command is read, not when it is executed. Therefore,   an alias definition appearing on the same line as another command does   not take effect until the next line of input is read. The commands   following the alias definition on that line are not affected by the   new alias. This behavior is also an issue when functions are executed.   Aliases are expanded when a function definition is read, not when the function is executed, because a function definition is itself a   compound command. As a consequence,   aliases defined in a function are not available until after that function is executed. To be safe, always put alias definitions on a   separate line, and do not use alias in compound commands.   The two sentences "Aliases are expanded when a function definition is read, not when the function is executed" and "aliases defined in a function are not available until after that function is executed" seem to be contrary to each other.  Can you explain what they mean respectively?


Me and my friends all have the same WiFi but cant connect to each others Minecraft LAN worlds.

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?


It should be possible to have multiple UV maps for one mesh, but I cannot figure out how. I cannot rename the default UVMap either. The given answer does not really seem to apply. For example, he sets the name manually but I cannot figure out how I should do that.

So, as a newbie relatively new to blender, I started doing some texture mapping (blender internal Render). I created a texture for the main object and a couple of transparent decals to decorate it. (basic effects made in GIMP). Simple stuff, just to know how it works.  After unwrapping, having 2 UV maps made, creating both new material and textures, enabling UV mapping coordination I always end up with:  - all - 1 faces of the cube being covered nicely in the main texture  - 1 face covered in blank material with a decal in the middle of it  - the whole thing partly coated by a huge "stain" of a decal  So, the problem is that I can't layer textures correctly. Is there a way to have one texture covering everything and more transparent ones on top of it? I am working on a bigger project right now and having this ability would be useful


I'm in the process of applying to graduate programs in a field unrelated to music. I write, record, and perform original music in my free time. Normally I would not mention this in a personal statement; however, one of the programs I am applying to has an additional statement where I am to discuss ways in which I would add to the diversity of the school. I do have material I hope to discuss that falls within normal parameters of relevance, but I am wondering if it would also be appropriate (or rather, not obviously inappropriate) to mention my creative projects? I would obviously attempt to mention them in a way that demonstrates personality traits about me (creativity and drive), rather than just an irrelevant aside.  Any help would be appreciated. Please let me know if there's any additional info I can provide.

And if they should, I assume that these things should go on a resume under something like "Activities and Community Service". I mean I consider being able to sight read music to play at my Church as a significant feat (how many people can do that?) and might sway one person on an admissions committee if he or she enjoys music and understands how hard one must have worked to accomplish this.   Badminton?.... perhaps not so much


Today I cam across the following exercise:  exercise  Let $\alpha: \mathbb R^n \rightarrow \mathbb R^n$ be a map with $\alpha^p=1$ for some prime $p$. Show that $\alpha$ has a fixed point.  origin  I found the exercise somewhere in my notes. The setting was roughly orientation and the orientation bundle.  approach  For my approach, of course I assumed that $\alpha$ has no fixed point and just as in the Brouwer fixed point theorem I obtained a map $\mathbb R^n \rightarrow \mathbb S^{n-1}$. But now I don't know how to continue. I especially have trouble using the assumption that $\alpha^p=1$.  Any hint or help for this exercise is welcome!  Sincerely Slin  Edit  This indeed is a duplicate of   The answer uses some more advanced theory. I am interested how to do it the way it is suggested in Bredon's "Topology and Geometry". I cannot make the connection between $\mathbb R^n$ and coverings.

I am asking if whether or not a finite group acts freely (as homeomorphisms) on $\mathbb R^n$.  To answer in the negative, it suffices to show: for any homeomorphism $f$ such that $f^d=\text{id}_{\mathbb R^n}$, then $f$ has a fixed point.  I am looking for a complete self-contained answer.


Both a power series and a Fourier series can be used to approximate a function.  How do you use these differently?

Both  and  are means to represent functions in a different form.   What is the connection between these two? Is there a way to get from one to the other (and back again)? Is there an overall, connecting (geometric?) intuition?


I am running Mountain Lion. But unfortunately, I'm having trouble downloading Mavericks Installer from the App Store.  Here is what happens: I search for Mavericks in the App Store, it shows Mavericks. I click on Upgrade. Then it asks for my Apple ID and password. As I enter the credentials, after a few seconds, the same thing happens, again asking for my Apple ID and password and nothing happens.  If my password was wrong, it should have shown a message indicating incorrect Apple ID/password.  What can I do to resolve this issue?

My App Store keeps saying this item is free in the store, that this item will be added to your purchases and it then says cancel or download.   I click download and it won't download and keeps popping up the same message over and over again.  How do I make it stop? I can't download any apps.


I know that we can not use yield in a try-catch block according to the documentation:     A yield return statement can't be located in a   try-catch block. A yield return statement can be located in the try   block of a try-finally statement. A yield break statement can be   located in a try block or a catch block but not a finally block.   I also know that Python has the same .  My question is: Why?  Why does this result in a compiler error? Is there some sort of underlying reason why this isn't allowed?

The following is okay: try {     Console.WriteLine("Before");      yield return 1;      Console.WriteLine("After"); } finally {     Console.WriteLine("Done"); }  The finally block runs when the whole thing has finished executing (IEnumerator<T> supports IDisposable to provide a way to ensure this even when the enumeration is abandoned before it finishes). But this is not okay: try {     Console.WriteLine("Before");      yield return 1;  // error CS1626: Cannot yield a value in the body of a try block with a catch clause      Console.WriteLine("After"); } catch (Exception e) {     Console.WriteLine(e.Message); }  Suppose (for the sake of argument) that an exception is thrown by one or other of the WriteLine calls inside the try block. What's the problem with continuing the execution in catch block? Of course, the yield return part is (currently) unable to throw anything, but why should that stop us from having an enclosing try/catch to deal with exceptions thrown before or after a yield return? Update: There's an  - seems that they already have enough problems implementing the try/finally behaviour correctly! EDIT: The MSDN page on this error is: .  It doesn't explain why, though.


I'm trying to use this code to change sublist value:  sublist = [[1],[1],[1],[]] list = [sublist,sublist] print(list) for i in range(0,2):     list[0][i] = [] print(list)   And in output I see this:  [[[1], [1], [1], []], [[1], [1], [1], []]] [[[], [], [1], []], [[], [], [1], []]]   How to change only value of list[0] without changing of the other list elements? Thanks.

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


I have been doing some problem questions from Matrices, when I encountered the following problem solving which led me to the doubt about what constitutes the "$\mathbf Sufficient Conditions$" for $Det(A+B)=Det(A)+Det(B)$ ? Q. If $A$ and $B$ are two orthogonal matrices of same order, and $\det(A) + \det(B) = 0$, then show that $A + B$ is a singular matrix. A. My approach was writing "$A+B$" as "$A.( I  +  A^{^-1}.B)$" and trying to show that $\det( I + A^{^-1}.B ) = 0$ which is sufficient for $A+B$ to be a singular matrix. I could easily prove that $\det(A^{^-1}.B) = -1$. And then if $Det(A+B)=Det(A)+Det(B)$ I could have shown that $Det(I  +  A^{^-1}.B) = Det(I) + -1 = 0$ But I got stuck at the thought whether if I could even write $\det(A+B)$ as $\det(A)+ \det(B)$. If I take $B=r.A$ for some scalar '$r$', then $\det(A+B)=(1+r)^n.\det(A)$ which is not same as $\det(A) + r^n.\det(A)=(1+r^n).\det(A)$. Or even for that matter, just considering $A=B$ which gives me $\det(A+B)=2^n.\det(A)$ which is not same as $\det(A)+\det(A)=2.\det(A)$. Just wondering if I could find the sufficient conditions which should be getting satisfied in the problem I am solving too.

I am trying to solve following problem.      Let $A, B \in \mathbb{R}^{n\times n}$ be an orthogonal matrices and $\det(A) = -\det(B)$. How can it be proven that $A+B$ is singular?   I could start with implication:  $\det(A)=-\det(B) \Rightarrow B$ is created from $A$ by swapping two lines or columns.   But I am not sure if this implication is correct.


What is difference between these two regarding implementation inside STL. what is the difference regarding performance? I guess when we are traversing the vector in "read only wise", we prefer const_iterator, right?  Thank you.

What is the difference between a const_iterator and an iterator and where would you use one over the other?


I know there are two groups of order $34$. One is obvious $\mathbb{Z}/ (34\mathbb{Z})$, but what is the other? I know it must not be abelian. How do I go about describing it? Extending on Sylow theorems?

I just constructed the semidirect product in Lang, and I'm trying to tie some facts together. From Ash's Algebra, I know that if $p\lt q$ are distinct primes, if $q\not\equiv 1\pmod{p}$, then any group $G$ of order $pq$ is abelian.  Is the converse true, that for any primes $p\lt q$, if $q\equiv 1\pmod{p}$ then there exists a nonabelian group of order $pq$?  One example I found online is that $\mathbb{Z}_3\ltimes \mathbb{Z}_7$ is nonabelian, and here $7\equiv 1\pmod{3}$. I was considering then semidirect products $\mathbb{Z}_p\ltimes\mathbb{Z}_q$ where $q\equiv 1\pmod{p}$ and some homomorphism $\phi\colon \mathbb{Z}_p\to\operatorname{Aut}(\mathbb{Z}_q)$ I calculate that  $$ (1,0)(0,1)=(1+0,\phi_0(0)+1)=(1,1) $$ and $$ (0,1)(1,0)=(0+1,\phi_{-1}(1)+0)=(1,\phi_{p-1}(1)). $$ Is it true somehow that $\phi_{p-1}(1)\neq 1$ in each case to show the group is nonabelian? I guess if it did this would imply $\phi_{p-1}$ is the trivial automorphism, so maybe there's something there? If not, is there a way to show $\mathbb{Z}_p\ltimes\mathbb{Z}_q$ is nonabelian in these cases in general? Thanks.


This question may stem from a misunderstanding of compilers on my part, but here goes...  One can find the following statement in the preface to the first edition of K&R (page xi):     The operating system, the C compiler, and essentially all UNIX applications programs (including all of the software used to prepare this book) are written in C.   (my emphasis)  Here's what I don't understand: doesn't that C compiler have to be compiled itself before it can compile any C code? And if that C compiler is written in C, wouldn't compiling it require an already existing C compiler?!  The only way out of this infinite-regression conundrum (or chicken-and-egg problem) is that the C compiler written in C that K&R are referring to was actually compiled with an already existing C compiler that was written in a language other than C. The C compiler written in C then superseded the latter.  Or am I completely off?

Intuitively, it would seems that a compiler for language Foo cannot itself be written in Foo. More specifically, the first compiler for language Foo cannot be written in Foo, but any subsequent compiler could be written for Foo.  But is this actually true? I have some very vague recollection of reading about a language whose first compiler was written in "itself". Is this possible, and if so how?


I am building internal in my custom module that I am porting to Drupal 8:   I need to get a current language prefix so I can prepend it to the link. I Drupal 7 it was as simple as:  global $language; $prefix = $language->prefix; $mylink = $prefix . '/example/something';   How can do this in Drupal 8?  EDIT: My issue specifically is that I have a language prefix set to NONE for the default language at Home >> Administration >> Configuration >> Regional and language >> Languages >> Detection and selection. (admin/config/regional/language/detection/url)  For the default language, I want the code to return the real prefix, i. e. NONE, not en (the code for the default language, English).

In Drupal 7 the current language is a global variable we can access with   global $language; $langcode = $language->language;    I want to know how can we access the current language in a Twig file in Drupal 8 (in page--front.html.twig for example)?


I'd like to feel more confident setting up mail for my clients with regards to false positives.  Here's what I know:  SPF records are good, but not every spam filter service/software (SFSS) uses them.  reverse DNS (PTR) records are pretty much a necessity.  Open relays are bad. (Here's "other tips" I've read):  the reverse lookup of the IP address of your mail server should resolve to the domain that you're sending mail out from.  your server should say HELO FQDN.of.your.mail.server.com when speaking to other mail servers.  the A host records in MX records should be (or resolve to to the IP address) your FQDN.of.your.mail.server.com   Feel pretty good about 1 and 3.  Here's where I'd like some clarification/suggestions: 2 and 4: I did alot of digging and this seems to be incorrect as most spam-filters are looking for a PTR in general and one that's not generically-assigned by the ISP; it doesn't appear that the domain you send mail out as has anything to do with this (i.e. if you owned two domains you used for mail, you'd need to send out from two IP addresses with PTRs for each?)  This makes sense, but does it care what that FQDN resolves to?  Should it resolve to the IP address that's currently sending said HELO?  Again, another one from various Google searches; don't see how this would work if you used Postini as your gateway service (or any other smarthost for that matter).   And what about sending on behalf of another domain that you're not authoritative for? I have some clients (some.branchdomain.tld) that are required to send mail out as @some.corporatedomain.tld, even though said corporate HQ won't setup a relay/smarthost for them to use.  corporatedomain.tld can create SPF records to show that some.branchdomain.tld is allowed to send mail, but would that still be considering "spoofing", especially if said SFSS doesn't check SPF records?  Should I be concerned about this?

This is a  about how to handle email sent from your server being misclassified as spam.  For additional information you may find these similar questions helpful:                    Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).  Now I want to know what should be done to create "good" emails. I know about reverse lookup etc., but (for example), what about a unsubscribe link with an unique ID?  Does that increase a spam rating?


I've been having issue allowing some special characters and when inserting them into database they are showing up incorrectly.

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


Evaluate: $\int e^x.\sin (x) dx$  My Attempt; $$=\int e^x.\sin (x) dx$$ $$=\sin (x).e^x - \int \cos (x).e^x dx$$ Neither of $\cos (x)$ and $e^x$ is going to vanish although we keep on using By Parts.  How to procced further?

I'm trying to solve the integral of $\left(\int e^x\,\sin x\,\,dx\right)$ (My solution):  $\int e^x\sin\left(x\right)\,\,dx=$  $\int \sin\left(x\right) \,e^x\,\,dx=$  $\left(\sin(x)\,\int e^x\right)-\left(\int\sin^{'}(x)\,\left(\int e^x\right)\right)$  $\left(\sin(x)\,e^x\right)-\left(\int\cos(x)\,e^x\right)$  $\left(\sin(x)\,e^x\right)-\left(\cos(x)\,e^x-\left(\int-\sin\left(x\right)\,e^x\right)\right)$  $\left(\sin(x)\,e^x\right)-\left(\cos(x)\,e^x-\left(-\sin\left(x\right)\,e^x-\int-\cos\left(x\right)\,e^x\right)\right)$  I don't know how to complete because the solution gonna be very complicated.


For a music therapy experiment, I have to use several crystal glasses with water and different cylindrical shapes, and make them vibrate and produce different sounds. Is there a math formula that binds together the radius of the glass, the level of the water (or the volume occupied), and the frequency that produces the sound? Thanks in advance.

A wine glass filled with water (approximately half or a quarter), when you use a wet finger and rub the top of the wine glass, the wine glass will produce a sound. I heard that it is because of the "stick and rub" effect ... Can you explain this effect or other principal that cause this sound to be produced?  how much water is least needed to produce a sound? What and why is the relationship between the quantity of the water and the pitch of the sound? Will the sound produced be greater if we use a denser or less dense liquid than water?  Thx for explaining :D


Hello I am trying to understand how Python's pass by reference works.  I have an example:  >>>a = 1 >>>b = 1 >>>id(a);id(b) 140522779858088 140522779858088   This makes perfect sense since a and b are both referencing the same value that they would have the identity. What I dont quite understand is how this example:  >>>a = 4.4 >>>b = 1.0+3.4 >>>id(a);id(b) 140522778796184 140522778796136   Is different from this example:  >>>a = 2 >>>b = 2 + 0 >>>id(a);id(b) 140522779858064 140522779858064   Is it because in the 3rd example the 0 int object is being viewed as "None" by the interpreter and is not being recognized as needing a different identity from the object which variable "a" is referencing(2)? Whereas in the 2nd example "b" is adding two different int objects and the interpreter is allocating memory for both of those objects to be added, which gives variable "a", a different identity from variable "b"?

Why does the following behave unexpectedly in Python?  >>> a = 256 >>> b = 256 >>> a is b True           # This is an expected result >>> a = 257 >>> b = 257 >>> a is b False          # What happened here? Why is this False? >>> 257 is 257 True           # Yet the literal numbers compare properly   I am using Python 2.5.2. Trying some different versions of Python, it appears that Python 2.3.3 shows the above behaviour between 99 and 100.  Based on the above, I can hypothesize that Python is internally implemented such that "small" integers are stored in a different way than larger integers and the is operator can tell the difference. Why the leaky abstraction? What is a better way of comparing two arbitrary objects to see whether they are the same when I don't know in advance whether they are numbers or not?


My visit aim to meet my sister and nephews, as they had not travel to my home last 10 years. Because my little nephew is ill and that disease  called autism spectrum disorder (ASD). He needs his mom special care at all time. I have also my mom in my home country she  is ill and is suffering asthma, allergy, and arthritis. I have done my engineering degree and start my own business. Iam the first carer of my old mom here in my home country. I have presented that during my trip my sister( married) here in my country   will take care my mom  for some days. My father has been died. I have submitted property detail , my car, house detail etc. Now if i want to reappear then what steps are necessary for explaining ECO that i am a genuine visitr and come back after my trip

I have applied recently for a general visitor visa to the UK to spend 10 days during Christmas with my British unmarried partner and it has been turned down.   The Entry Clearance Officer stated on his refusal notice the following:     I note that you have never previously travelled to the UK or any country with similar immigration requirements and you therefore do not have a history of travel and compliance to consider.      You have submitted an employment letter to confirm your occupation in KSA but I am required to also assess your personal, domestic and economic circumstances in determining whether you are genuine visitor travelling to the UK for the period and purpose you state.      You claim an income of SAR ........ per month which equal ........ GBP and from the evidence submitted this appears to be your sole source of income.   I note that this monthly income is reflected on your bank statements. However, the bank statement you have presented show a recent large deposit that are in excess of your stated income and inconsistent with the account history. You haven't provided evidence toward the origin of this recent deposit and in the absence of reasonable evidence I am not satisfied that these bank statements accurately reflect your personal circumstances.      In view of the above, I am not satisfied you have demonstrated that your circumstances are as you claim and therefore I am not satisfied that you're travelling to the UK for the period and purpose you stated. 41(i)and(ii).   Its true that I have deposited that sum of money right before I apply and it was a commission I received from work earlier this month.   So, could you please give me your advice on the above as I am planning to apply again soon. and how to avoid my application being refused again?


How do we evaluate the infinite nested radical  $  \sqrt {2+ \sqrt {3+ \sqrt{4+ \sqrt{5+\cdots}}} } $ $\space $?   Please help   N.B. :- It is not a duplicate

It is an interesting task to try finding the limit of nested square root expressions.      $$\lim_{n \to \infty}\left( 1 + \sqrt{2 + \sqrt{3+ ... + \sqrt {n + \sqrt{n+1}}}}\right)$$   How to solve this one?


Is there another type of motion other than SHM that has this property? How would one systematically find the general form of the motion that respects this constraint?

The  asks what shape a hill should be so a ball slides down in the least time.  The  asks what shape yields an oscillation frequency that is independent of amplitude.  The answer to both problems is a cycloid.  Is there an intuitive reason why these problems have the same answer?  Proposed operational definition of "intuitive":  Imagine modifying the problem slightly, either to the  (tunnel through Earth), or by taking account of the finite radius of the ball.  If the answer to the original question is intuitive, we should easily be able  to tell whether these modified situations continue to have the same brachistochrone and tautochrone curves.


I just upgraded my Ubuntu 17.04 to 17.10 and I found that it is no longer accepting password in the gksudo nautilus password window. I get this error instead  (nautilus:18063): Gtk-WARNING **: cannot open display: :0 not connect: Connection refused

I installed Ubuntu 17.10. Now I am having trouble with gksu:  $ gksu -dg synaptic No ask_pass set, using default! xauth: /tmp/libgksu-HgUjgQ/.Xauthority STARTUP_ID: gksu/synaptic/8760-0-alex-XPS-15-9530_TIME4974977 cmd[0]: /usr/bin/sudo cmd[1]: -H cmd[2]: -S cmd[3]: -p cmd[4]: GNOME_SUDO_PASS cmd[5]: -u cmd[6]: root cmd[7]: -- cmd[8]: synaptic buffer: -GNOME_SUDO_PASS- brute force GNOME_SUDO_PASS ended... Yeah, we're in... Unable to init server: Could not connect: Connection refused (synaptic:8767): Gtk-WARNING **: cannot open display: :1 xauth: /tmp/libgksu-HgUjgQ/.Xauthority xauth_env: (null) dir: /tmp/libgksu-HgUjgQ   If I don't use -g, the password dialog is disabled. So looks like a problem with creating a tty for root.  Any advice?


Prove that for any set $X$ we have the $|X| < |\mathcal{P}(X)|$ (power set of $X$)  How would you prove this using the definitions of bijection, surjection, and injection?  Also, does this mean when we have the empty set $X = \{\}$, then $|X| < |\mathcal{P}(X)|$ as well? Would they not be equal?

I am trying to prove the following statement but have trouble  comprehending/going forward with some parts! Here is the statement:     If $A$ is any set, then  $|A|$ $<$ $|P(A)|$   Here is what I have so far:  We need to show that there is an injection from $A$ to $P(A)$ but not a surjection.   A natural choice for an injection is the function $ f(x)$ $=$ $\{x \}$, which in plain English, takes any element $x$ (that is in $A$) and sends it to the one-element set $\{x \}$. Thus $f(x)$ is injective!  To show that there is no surjection, for the sake of contradiction, assume there is a surjection. Here is where I start to have trouble. Surjectivity means that every element of the co-domain is mapped to an element of the domain, correct? Consequently, in this particular case, we are "matching" sets (from $P(A)$) to elements (from $A$) right?  If the above is correct, my problem arises here. I am not sure how to prove that $f$ is not surjective. Unfortunately, I am easily confused by notation so please explain in English.  Thank you in advance!! :)


Suppose there is a question, "How to get started with applying item response theory and what software to use?"  Suppose the top-rated answer cites my name and work a couple of times.  Suppose all answers discuss software, which is what the question asked about.  Suppose I have a new piece of software, and I tell people about it, as this was what they asked.  Suppose my answer gets immediately deleted by a moderator with a message, "We're glad to have you, but unfortunately this isn't the place for such a description of your software." Did the person even read the original question, in the first place? Would he or she be qualified to understand the value of an immensely complicated psychometric package being released, free of charge, to the community?  And -- what can you do?  And -- who and how defines "overt"? How is a single recommendation of a freely available software package, provided as an answer to a question about such packages, on a page that discusses packages top to bottom, "overt"?

It's    that posting links to your own website is ok, but should there be a line drawn? There were several spam flags today for 's recent posts, presumably because they all link to his website. Initially I disagreed because his answers seem for the most part relevant to the question, but then I looked into it more and realized there's three things that set this apart from most of the related cases that have come up:   This isn't an occasional thing -- he's posted  in the last year This isn't a random blog he writes for a fun, it's a for-profit company he  and makes money promoting I'm not willing to go through all 412, but from the sample I checked, he generally doesn't mention that the products he's recommending are his own. The site is linked from his profile, but most people aren't going to check that   Is all this considered acceptable use, or are the spam flags accurate?


I have a simple question that why positive and negative charges attract each other? We always learn that there is always a reason behind this. Can anyone tell me the actual reason behind this?

I know plus pushes another plus away, but why, really, do they do that? On the other hand, molecules of the same type are attracted to each other. I find that weird.  I do know some stuff about four universal forces. But why in general the general "rule" is that opposite charges pull each other?   Yes, I do realize this could be connected to very basic stuff that science is still trying to figure out, and can be traced to the Higgs,  but still, there must be something to tell.


I have an account on  and I am able to post questions but I don't know to log out. How can I do that?

Per the title, where is the logout button?  All the existing questions I can find refer to the previous design of the site, where hovering over your name in the top bar brought up a menu.


How can I change the font of all of my \addchap{ } (chapters) to the font "Times" and the size of it (preferably \large and bold)?  The List of Figures, List of Tables and the Table of Contents should also have the same structure, as described above.  Here an example of my code. (If you need more of the code please tell me, I might have missed something).  \documentclass[12pt,chapterprefix]{scrreprt} % for bigger size of text  \usepackage{times} \usepackage[english]{babel} \renewcaptionname{english}{\listfigurename}{Figures} \renewcaptionname{english}{\listtablename}{Tables}  \begin{center} \listoftables \end{center} \begin{center} \listoffigures \end{center} \renewcommand{\figurename}{Figure} \renewcommand{\listtablename}{Tables}   \usepackage{titlesec} \titleformat{\section}[block]{ \Large \filcenter}{}{1em}{}%\sffamily \titleformat{\subsection}[hang]{\filright \itshape }{}{1em}{}  %\titleformat{\chapter}[hang]{\filright \bfseries }{}{1em}{} <- if that code is used, yes the size changes, but my "Chapter [Number]" (see picture) disappears on the page itself but not in the toc.  \begin{center} \tableofcontents\thispagestyle{empty} \end{center   %chapter in toc and on page (numbering) \renewcommand*{\raggedchapter}{\centering} \renewcommand*{\chaptermarkformat}{\chapappifchapterprefix{\nobreakspace}\thechapter\autodot:\enskip}  \let\originaladdchaptertocentry\addchaptertocentry \renewcommand*{\addchaptertocentry}[2]{%   \IfArgIsEmpty{#1}     {\originaladdchaptertocentry{#1}{#2}}     {\originaladdchaptertocentry{\chapappifchapterprefix{\nobreakspace}#1\autodot}{#2}}% } \RedeclareSectionCommand[   tocentrynumberformat={\def\autodot{:}},   tocdynnumwidth ]{chapter}  \begin{document} \addchap{Introduction}\setcounter{page}{1} % unnumbered chapter

Is there a possibility to change the font-style in the table of contents? Everything I wrote down in my document was written with Times. However, the ToC does not have the same font family. Is there a way to change the font of the ToC to Times New Roman? Thank you : )    \documentclass[a4paper, fontsize=11pt]{scrbook} \usepackage{geometry} \geometry{a4paper, top=25mm, left=25mm, right=25mm, bottom=20mm, headsep=10mm, footskip=12mm}  \usepackage[ngerman]{babel}  \usepackage[T1]{fontenc}        \usepackage[latin1]{inputenc} \usepackage{acronym}      \usepackage{anyfontsize}  \begin{document}  \tableofcontents  \chapter{Test} Is there a possibility to change the font-style in the table of contents? Everthing I wrote down in my document was written with Times. However, the ToC does not have the same font family. Is there a way to change the font of the ToC to Times New Roman?  \end{document}


I am using sshd on Ubuntu 16.4 LTE and I am trying to configure my sshd so that when a user is connected fo too much time not doing anything he'll get disconnect by the ssh server.

I can't seem to find an answer to this simple question, which I need for some compliance documentation.    On a default install of CentOS 6.5 (OpenSSH 5.3p1-94.el6), after how long of being idle will a user's SSH session be terminated?  I believe the following can be set to increase the idle timeout, but they are commented out by default.  $ grep -i alive /etc/ssh/sshd_config #TCPKeepAlive yes #ClientAliveInterval 0 #ClientAliveCountMax 3   Also, is there a command to dump a list of the current sshd settings?  I don't see anything in man sshd.


I am iterating an IEnumerable from EnumerateFileSystemEntries where the act of getting the next element could throw an access denied exception. So I wrap it in a try but I don't want to stop iterating just because one element in the middle is bad. There are more elements that are good after the bad one. So I put a continue in my catch but that's not valid. Is there a way to do what I am failing to do here? paths = Directory.EnumerateFileSystemEntries(RootDirectory, SearchPattern, SearchOption); try {     foreach (var path in paths)     {         // Do something with the paths     } } catch (Exception ex) {     Debug.Print(ex.Message);     continue;    // ERROR: "No enclosing loop out of which to break or continue" }  I have gone through every answer in 3 duplicate posts. They all suffer from the same problem. The only solution I have seen is to port my application to .NET core which is a long process:  If you came here looking for a FrameWork based solution, abandon all hope. Nobody here will help you. If you do come up with a good answer you can't even add it because all of the other posts have flawed solutions accepted.

I am trying to display a list of all files found in the selected directory (and optionally any subdirectories). The problem I am having is that when the GetFiles() method comes across a folder that it cannot access, it throws an exception and the process stops.  How do I ignore this exception (and ignore the protected folder/file) and continue adding accessible files to the list?  try {     if (cbSubFolders.Checked == false)     {         string[] files = Directory.GetFiles(folderBrowserDialog1.SelectedPath);         foreach (string fileName in files)             ProcessFile(fileName);     }     else     {         string[] files = Directory.GetFiles(folderBrowserDialog1.SelectedPath, "*.*", SearchOption.AllDirectories);         foreach (string fileName in files)             ProcessFile(fileName);     }     lblNumberOfFilesDisplay.Enabled = true; } catch (UnauthorizedAccessException) { } finally {}


Hi I am trying to adapt the excellent VBA that was posted previously to go through data and take all lines with the same id in column 1 and add them all into one row for each. Trying to get from this:    To this    but the adapted code below only ever combines 2 rows even if there are more than two with the same id in column 1.  Sub CombineInvoices() Dim currentRow As Long Dim currentCol As Long Dim LastRow As Long LastRow = Cells(Rows.Count, 1).End(xlUp).Row  currentCol = 4 For currentRow = LastRow To 2 Step -1     If Cells(currentRow, 1) = Cells(currentRow - 1, 1) Then         Range(Cells(currentRow, 1), Cells(currentRow, 4)).Copy Destination:=Range(Cells(currentRow - 1, currentCol + 1), Cells(currentRow - 1, currentCol + 4))         Rows(currentRow).EntireRow.Delete     End If Next currentCol = currentCol + 4 End Sub   All help really gratefully received.

I have data like so:  1001NCCN    3618127 1001NCCN    208478 1001NCCN    207316 1001TEMN    409889 1001TEMN    801651 1001TEMN    273134 1001TEMN    208478 1001TEMN    207316   I need to transpose/combine the rows that have matching values in the first column with a final result like so:   1001NCCN    3618127 208478  207316       1001TEMN    409889  801651  273134  208478  207316   I looked at Pivot Tables, and filtering but neither seemed like they can give me what I need.  Is there a way to do this within Excel?


So when I take pictures of lamps or any kind of lighting on a house. I get this white-out around the fixture. I would like to know what setting or what i need to do to be able to "see the bulb" without having the white out effect.  Not sure if this makes sense or not , but...  Thank you Michael ALlen

I am quite new to photography and was looking into how I can take better indoor photographs, particularly around night time.  I'm currently in a hotel room for the night and decided to try and take a picture of my room to test out my tripod which I haven't used before. However I noticed no matter what I set my camera settings to the artificial lights (particularly the lamp on the left, image attached) just appeared very washed out. You can't tell any detail about the lamp shade all you can see is just some sort of light but not much to it.  I tried a variety of fstop/shutter speed settings and tried a variety of ISO settings but they all appeared pretty much the same unless I massively underexposed the image.  Given that I wondered whether the solution would be to take a HDR image or take a normal exposure and an underexposed image and blend them later? I understand that artificial light like this can be very hard and harsh but I wondered if there's a way of improving the result with looking away from it?  I wasn't trying to take any particular special picture here but just test out my camera a bit more but this was the first thing I noticed and I didn't know how to fix it. Any tips would be greatly appreciated.


I am looking for a step-by-step solution to the following infinite sum:  $\sum_{i=0}^\infty \frac{i^n}{4^i}$  I know that I can find the solution to something like this:  $\sum_{i=0}^\infty \frac{i^2}{4^i}$  by starting with the geometric series and its closed form:  $\sum_{i=0}^\infty x^i = \frac{1}{(1-x)}$  and by differentiating both sides by x then multiplying both sides by x and repeating (perform differentiation by x followed by multiplication by x) i can get:  $\sum_{i=0}^\infty i^2x^i = \frac{x(1+x)}{(1-x)^3}$  at which point I just set x = (1/4) and the RHS evaluates to 20/27.  But I am unsure of what to do when the power of i in the series is set to n, instead of a constant like 2 or 3

For computing the present worth of an infinite sequence of equally spaced payments $(n^{2})$ I had the need to evaluate  $$\displaystyle\sum_{n=1}^{\infty}\frac{n^{2}}{x^{n}}=\dfrac{x(x+1)}{(x-1)^{3}}\qquad x>1.$$  The method I used was based on the geometric series $\displaystyle\sum_{n=1}^{\infty}x^{n}=\dfrac{x}{1-x}$ differentiating each side followed by a multiplication by $x$, differentiating a second time and multiplying again by $x$. There is at least a second (more difficult) method that is to compute the series partial sums and letting $n$ go to infinity.  Question: Is there a closed form for  $$\displaystyle\sum_{n=1}^{\infty }\dfrac{n^{p}}{x^{n}}\qquad x>1,p\in\mathbb{Z}^{+}\quad ?$$  What is the sketch of its proof in case it exists?


I understand that a calculation such as 0.0375 + 0.0375 + 0.0375 results in 0.11249999999999999.  If I were to continually add '0.0375' to a double variable in a for loop (x times), would you find that the result at each iteration gradually becomes more and more inaccurate due to the issues with floating point precision?  I can tolerate an approximation such as the one shown above, but can't have a result which continues to deviate from the actual result as the number of iterations increases.  EDIT:  I've run the following test (with several values):  std::cout.precision(17);  double t = 0.42300*783698177;     std::cout << std::fixed << t << std::endl;  double g = 0; for (int y = 0; y < 783698177; y ++){     g = g + 0.42300; }  std::cout << std::fixed << g << std::endl;   As I suspected, as the number of iterations increases, the more likely (or simply the more) the result deviates from the actual value.   Has anybody else observed this?  Although I feel I understand why this is happening, could somebody provide an intuitive (or basic mathematical) explanation for why this occurs?

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


i'm having some difficulties in PHP pdo queries.Here's a example of the query im trying to make  public function admin_hoca_onay($data){ global $pdo; if($data["islem"] == "genelkaldir" || $data["islem"] == "puankaldir" || $data["islem"] == "girdikaldir"){   $durum = "0";  } elseif($data["islem"] == "genelonay" || $data["islem"] == "puanonay" || $data["islem"] == "girdionay"){   $durum = "1"; }  $query = "UPDATE defter SET :islem=:durum WHERE hoca=:hoca"; $stmt = $pdo->prepare($query); $stmt->bindParam(":islem", $data["row"]); $stmt->bindParam(":durum", $durum); $stmt->bindParam(":hoca", $data["hoca"]); $result = $stmt->execute();  if($result){   return 1; } else{   return 0; } }   as you can see there in my query theres a part like :islem=:durum i know that we can insert variables in query with bindParam but im not sure if this kind of a thing work.

Why can't I pass the table name to a prepared PDO statement?  $stmt = $dbh->prepare('SELECT * FROM :table WHERE 1'); if ($stmt->execute(array(':table' => 'users'))) {     var_dump($stmt->fetchAll()); }   Is there another safe way to insert a table name into a SQL query? With safe, I mean that I don't want to do  $sql = "SELECT * FROM $table WHERE 1"


Find the minimal polynomial of the 18th root of unity and the Galois group of $\mathbb{Q}(z_{18})$ So the minimal polynomial is $x^6-x^3+1$ and i checked online and it is correct. Now for the galois group it is isomorphic to $(Z_{18})^*\approx(Z_9)^*\approx Z_6$. Thus it is cyclic. Its generators are $z_{18}\to z_{18}^5$ and $z_{18}\to z_{18}^{11}$

Question 1: For $n \in \mathbb{N}$ explain why $\mathbb{Q}(\zeta_n)$ is Galois over $\mathbb{Q}$   We must show that it is normal and separable.   $\mathbb{Q}(\zeta_n)/\mathbb{Q}$ is normal since it is a splitting field for $X^n-1 \in\mathbb{Q}[X]$ (I think... Is this correct?).  It is separable because it is of characteristic $0$  Question 2: $Gal(\mathbb{Q}(\zeta_n)/\mathbb{Q}))\cong \mathbb{Z_n}^*$  Is this because the primitive nth root of unity $\zeta_n$ acts as a generator for a cyclic group? I am unable to fill out a decent proof on this.   Thanks for your help


I know that 2 qubits are entangled if it is impossible to represent their joint state as a tensor product. But when we are given a joint state, how can we tell if it is possible to represent it as a tensor product? For example, I am asked to tell if the qubits are entangled for each of the following situations:   $$\begin{align} \left| 01 \right>\\ \frac 12(\left| 00  \right> + i\left| 01  \right> - i\left| 10  \right> +  i\left| 11  \right> )\\ \frac 12(\left| 00 \right> - \left| 11  \right>)\\ \frac 12(\left| 00  \right> + \left| 01  \right> +i\left| 10  \right> +  \left| 11  \right> )  \end{align}$$

The Bell state $|\Phi^{+}\rangle = \frac{1}{\sqrt{2}}(|00\rangle + |11\rangle )$ is an entangled state. But why is that the case? How do I mathematically prove that?


Basically I have the problem seen in the image below (sorry for blurring the text, but the problem should be easily seen). I have a section, followed by some text, and then on the next page a figure is right at the beginning, and then a new section right after, so no extra text available to go onto this page I imagine.   And as you can see the white space between the section title and the text just looks stupid. Any idea how to fix this ? I would much rather that all next were aligned at the top, and then the white space was at the bottom.

I'm writing my bachelor-thesis and have a couple of small sub-sub-sections explaining conversions, like in the following  \subsubsection*{Assignment}  This document only explains non-compound assignments. The other kind, i.e \texttt{a += b}, is supported by the language too, but is not yet implemented.   \begin{itemize} \item If the first is an \texttt{auto} variable, no conversion takes place when assigning       the right hand side to the variable designated by the left hand side.  \item Otherwise, an assignment conversion takes place converting the given value to the type       of the designated variable.  \item Assignment requires an lvalue as the left hand side, and yields an lvalue result.  \end{itemize}  \subsubsection*{Multiplication} % ...   But latex renders it quite ugly with much space in between the items. I think it does so to fit the whole page. How can I tell it not to do so? Is what I'm doing right at all?


Hi I am trying to create a app where I am will be displaying map in a fragment using SupportMapFragment but I am getting NullPointerException. Here is the full error code   java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.SupportMapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference at obs.sharemytable.fragment.Search.onCreateView(Search.java:49) at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617) at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:145) at android.app.ActivityThread.main(ActivityThread.java:6918) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)   Search.java:  public class Search extends Fragment{   GoogleMap mGoogleMap;    public static Search newInstance() {         Search fragment = new Search();         return fragment;     }     @Nullable     @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {          final View view = inflater.inflate(R.layout.search_layout, null, false);           SupportMapFragment mapFragment = (SupportMapFragment) this.getChildFragmentManager()                 .findFragmentById(R.id.map_container);         mapFragment.getMapAsync(new OnMapReadyCallback() {             @Override             public void onMapReady(GoogleMap googleMap) {                 mGoogleMap = googleMap;                  // Add a marker in Sydney and move the camera                 LatLng sydney = new LatLng(-34, 151);                 mGoogleMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));                 mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));             }         });          return view;     } }   search_layout.xml  <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical" android:layout_width="match_parent"     android:layout_height="match_parent"     android:background="@android:color/white">      <include         android:id="@+id/searchToolbar"         layout="@layout/toolbar" />     <com.google.android.gms.maps.MapView         xmlns:android="http://schemas.android.com/apk/res/android"         android:id="@+id/map_container"         android:layout_width="match_parent"         android:layout_height="match_parent" >     </com.google.android.gms.maps.MapView>  </LinearLayout>   Can someone figure what mistake I have done here.

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'm currently trying to convert a floating point value to an integer while preserving the decimals(long story short user input needs to be in decimal form but I can't keep the variable as a floating point because rounding errors). I do this with this code:  c = initial * 100;   In this example, "c" is the int and "initial" is the floating point. The problem is, C will get the very basic multiplication wrong somehow, 4.2 returning as 419 instead of 420. I don't really know how to fix this - I assume it must be another issue with floating point rounding errors.


I'll use a concrete definition of a dihedral group $D_{2n}$ which emphasizes its group structure:      $D_{2n}$ consists of distinct elements $r_0,...,r_{n-1},s_0,...,s_{n-1}$ so that for any $i \in \mathbb{Z}$ we have $r_{i + n} = r_i, s_{i + n} s_i$ and for any $i,j \in \mathbb{Z}$ we have $r_ir_j = r_{i + j}, r_is_j = s_{i + j}, s_ir_j = s_{i - j}, s_is_j = r_{i - j}$.   It's easy to see that all $r_i's$ commute in $D_{2n}$, hence the only elements for which it is possible not to commute are $s_i$ and $s_j$ or $r_i$ and $s_j$.  $s_is_j = s_js_i$ whenever $i - j \equiv j - i \bmod n$ and $r_is_j = s_jr_i$ whenever $i + j \equiv i - j \bmod n$, hence $D_{2n}$ is noncommutative if and only if either   there is $0 \leq j < n$ so that $n\nmid 2j$, or there are $0 \leq i,j < n$  so that $n\nmid 2(i - j)$.   Using this result, it's not hard to establish that $D_2$ and $D_4$ are abelian.  I wonder how we can use this to prove that $D_{2n}$ is not abelian for $n \geq 3$. I'm not interested in a possible geometric proof.

Is it true that a dihedral group is nonabelian?  I'm not sure if the result is true. I checked it for some lower order and I think the result may correct.   But I failed to prove/disprove the result.


I have two tables: CITY (~50000 rows) and COUNTRY (~220 rows). THere is a task, to provide which city is in which country via VIEW? And if you are able to use materialized view, is it better?  I wrote current query:  CREATE VIEW cc as SELECT ct.NAME AS "country", c.NAME AS "cty" FROM CITY c JOIN COUNTRY ct ON cnt.CODE=c.COUNTRY;   It gives me the information I need, but I didn't realize any difference bitween normal view and materialized one. Which is relevant?

What is the difference between Views and Materialized Views in Oracle?


I have encountered a really weird situation. Im developing a software, to which I want to add a feature to confirm email, so basically, it sends an ajax request to my server and server responds with a key, this key will be also sent in the email within a link. This key is saved as a variable and then I add a setInterval, which runs a link, which by the key responds if the user has clicked the link or not. The data is stored in mysql. That everything works perfectly fine with one little issue. The AJAX responses do not update and just keep the old value although when I open the checking link in my browser the response is indeed different, does anybody have any thoughts what might by causing this issue?         $.ajax({             url: "http://...&em=" + email,             type: "GET",             success: function(rese){                 if(rese === "E1") {                 }else{                     var checker = setInterval(function(){                         $.ajax({                             url: "http://...&key=" + rese,                             type: "GET",                             success: function(resee){                                 alert(resee);                             }                         });                     }, 3000);                 }             }         });  Edit - Server responses: so, the data is updated in the moment, when user does click the link, the value changes to "yes", while normally, it would respond with just "no", but anyway, ajax keeps alerting me with no, even when i just have updated the value straight in the database

It looks like if I load dynamic content using $.get(), the result is cached in browser.  Adding some random string in QueryString seems to solve this issue (I use new Date().toString()), but this feels like a hack.   Is there any other way to achieve this? Or, if unique string is the only way to achieve this, any suggestions other than new Date()?


My friend and I recently purchased Rainbow Six: Siege on Steam. However I have a very limited data plan so I can't download. Can I copy the game contents from his PC to mine?

I have just bought a new computer and I have everything migrated over except for my Steam games.  I looked in Program Files/Steam/ and I found a folder full of the games I have downloaded, but I do not know if it is safe to just copy these folders from one computer to another (seeing as a lot of other applications will not work if you do this), or is there another recommended way?  I don't really feel like re-downloading all my games. I don't have the time nor bandwidth to download 20GB over a 1.5mbps connection.  Is it possible to contact Valve and get a disk with the games on it?


I set a PIN screen lock on my Sony ST21i (Android 4.0) and forgot the code. No encryption, no root, and the phone won't show up a "Forgot PIN?" button. How to regain access to my phone? There is no important information in it, so any solution that deletes all data is fine. Help!  Edit: Didn't work:   Android Device Manager Trying to boot into "recovery mode" using various key combinations found online

I have an Android device which is running Android 4.0.3 (or something like that).  My little brother decided to try and guess my lock screen pattern the other day, and ended up locking me out.   I have since been unable to log back in to the tablet using my Google Account details. I provided the correct login details, however it says they are incorrect. Could this be connected to the fact I have no internet connection?  I have no internet connection as the device is WiFi only, and the WiFi is currently turned off. I cannot turn it on, as I am locked out.  How can I log back into my tablet without wiping the user data?


I am using the SE app. Clicking on the achievement button I see a line stating " SE xxxx -10 user removed ".   I did very little activity on that SE and received very few upvotes.  I was never unpolite nor involved in sensitive topics or debates, especially because the SE topic in itself is unlikely to led to misbehaviour.   Does it really means that I have been removed and especially it is normal to be removed without warning or a more explicative notification?   Can I contact the moderator(s) of a specific SE and, if yes, how?

Message appearing when a user was removed.     It seems I lost 1765 reputation points on Stack Overflow yesterday. The reason given in my history is "removed", with the description of "User was removed ()". I don't understand what that means. What caused this?


I would like to add a subtitle to a chapter with the format \scshape and make it appear in the table of contents with the same format. Something like this:

I have several chapter titles that I would like to combine with subtitles, typeset in italics.  For example,      Chapter Title      A very fine chapter indeed …   Now, I found an approach on how to do this , introducing a new \Chapter command, which now looks like this:  \newcommand\Chapter[2]{   \chapter[#1: {\itshape#2}]{#1\\[2ex]\Large\itshape#2} }   This somewhat works (although it breaks TextMate's auto-recognition of chapters), but I would like these subtitles to also be visible in the Table of Contents.  Like so:     Chapter Title                                                                                1      A very fine chapter indeed …   Is there any way to achieve that? Note that my LaTeX fu is pretty limited, so I'm not sure where to even start.


I used sudo apt-get install ns2 to install ns2. I want to know where are the above mentioned directories stored on my system?

I want to know where I can find my installed application when I installed it on Ubuntu using package manager.  I installed RabbitMQ and ran locate rabbitmq which gave me following result:  /home/anupamg/.m2/repository/com/rabbitmq /home/anupamg/.m2/repository/com/rabbitmq/amqp-client /home/anupamg/.m2/repository/com/rabbitmq/amqp-client/1.7.2 /home/anupamg/.m2/repository/com/rabbitmq/amqp-client/1.7.2/_maven.repositories /home/anupamg/.m2/repository/com/rabbitmq/amqp-client/1.7.2/amqp-client-1.7.2.jar /home/anupamg/.m2/repository/com/rabbitmq/amqp-client/1.7.2/amqp-client-1.7.2.jar.lastUpdated /home/anupamg/.m2/repository/com/rabbitmq/amqp-client/1.7.2/amqp-client-1.7.2.jar.sha1 /home/anupamg/.m2/repository/com/rabbitmq/amqp-client/1.7.2/amqp-client-1.7.2.pom /home/anupamg/.m2/repository/com/rabbitmq/amqp-client/1.7.2/amqp-client-1.7.2.pom.lastUpdated /home/anupamg/.m2/repository/com/rabbitmq/amqp-client/1.7.2/amqp-client-1.7.2.pom.sha1 /home/anupamg/Downloads/rabbitmq-server-generic-unix-2.4.0.tar.gz


I understand that an array is being declared in line 3.  Line 6 queries the array. But how? I don't see any variable being passed around.  $(function(){      var currencies = ["stack", "over", "flow"];      // setup autocomplete function pulling from currencies[] array     $('#autocomplete').autocomplete({         lookup: currencies,         onSelect: function (suggestion) {         $('#outputcontent').html(thehtml);         }     });  });   Autocomplete Search:

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


My professor argues that one of the fundamentally unique properties of Quantum Mechanics is that the imaginary unit i is not removable (you can't avoid using it, unlike in other areas of physics like AC circuits where it is merely a convenience).   However, I'm not convinced. Isn't the reason i appears in the schrodinger equation that the equation needs to relate the wavefunction to its derivative? For convenience, we represent the wavefunction as a (possibly infinite) linear combination of complex exponentials, and this makes taking the derivative extremely easy which is where the factor of i comes from. However, can't complex exponentials always be replaced by sines and cosines? Wouldn't there be some way to state schrodinger's equation without using i as a result? The i merely represents the phase shift between the wavefunction and its derivative, so it makes the schrodinger equation much easier to write down (it would be more difficult to write a differential equation with an explicit phase shift). However, I don't see why a version of the schrodinger equation communicating the phase shift directly rather than by using i would be any less correct. Can you provide an argument for why the use of complex numbers is essential in quantum mechanics?

I am trying to understand how complex numbers made their way into QM. Can we have a theory of the same physics without complex numbers? If so, is the theory using complex numbers easier?


I cannot remember my network wifi password to set up another device.  Is there a way to see the password on my iPad since it is connected to my personal wifi?

I've previously connected to a wifi network on my iPhone but I've no way of finding out the password. So is there any way to view saved wifi passwords on the iPhone?


I am talking about this post :    The user seemed to be able to post two answers without deleting one. Is this correct or some mismatch ?

I was really surprised with the way Stack Overflow question  was answered. One user had posted two answers ( and ) instead of using the "Edit" option on any one of the posts. The most surprising thing is the upvotes. The answers posted by the user got three upvotes for both of the answers. Is this the correct way of using the answering mechanism?  Please provide your thoughts.


I recently read an online discussion about .  To be honest, I'm confused.  What's the bottom line there?    For a specific statement, say,     Foobar is 3.45 (with CI = [3.08, 3.82] at 99% confidence level)   my understanding is that if the experiment/measurement is done many times by drawing different random samples, then 99% of the times, the CI deduced based on each of the random sample will contain the true value of population statistic.  But what exactly does the specific CI of [3.08, 3.82] mean? Is there any positive logic statement that can be made that use [3.08, 3.82] as a parameter?

I know roughly and informally what a confidence interval is.  However, I can't seem to wrap my head around one rather important detail:  According to Wikipedia:     A confidence interval does not predict that the true value of the parameter has a particular probability of being in the confidence interval given the data actually obtained.     I've also seen similar points made in several places on this site.  A more correct definition, also from Wikipedia, is:     if confidence intervals are constructed across many separate data analyses of repeated (and possibly different) experiments, the proportion of such intervals that contain the true value of the parameter will approximately match the confidence level   Again, I've seen similar points made in several places on this site.  I don't get it.  If, under repeated experiments, the fraction of computed confidence intervals that contain the true parameter $\theta$ is $(1 - \alpha)$, then how can the probability that $\theta$ is in the confidence interval computed for the actual experiment be anything other than $(1 - \alpha)$?  I'm looking for the following in an answer:   Clarification of the distinction between the incorrect and correct definitions above. A formal, precise definition of a confidence interval that clearly shows why the first definition is wrong. A concrete example of a case where the first definition is spectacularly wrong, even if the underlying model is correct.


I am attempting to create a string that is used with HTML. But the scope of what I am attempting is completed in javascript. My code is not returning the way my mentor has desired, so I am at a bit of loss.  My function is called toQueryString, which accepts an object and returns a string with each key and value separated by a = and each pair separated by a &. If the value is an array, add another pair to the string with each value.  My code is:  function toQueryString(obj) {   var key = Object.keys(obj);   var value = Object.values(obj);   var result = ``;   for (let i = 0; i < key.length; i++) {     for (let j = 0; j < value.length; j++) {       result += key[i] += `=` + value[j] + `&`;     }   }   return result; }  toQueryString({"bar": [ 2, 3], "foo": 1 }) // "bar=2&bar=3&foo=1"   This returns:  'bar=2,3&bar=2,3&=1&foo=2,3&foo=2,3&=1&'   but should return this:  bar=2&bar=3&foo=1   Can anyone help me figure out what is broken?

Just wondering if there is anything built-in to Javascript that can take a Form and return the query parameters, eg: "var1=value&var2=value2&arr[]=foo&arr[]=bar..."  I've been wondering this for years.


Suppose f is a function from X to Y and g is a function from Y to Z. Prove the following: g o f is one-to-one, then f is one-to-one.  How would I start such a problem.

The Problem:  Let $X, Y, Z$ be sets and $f: X \to Y, g:Y \to Z$ be functions.  (a) Show that if $g \circ f$ is injective, then so is $f$.  (b) If $g \circ f$ is surjective, must $g$ be surjective?  Where I Am:  So, I really have trouble with these, for some reason. I can draw pictures and make sense of the problems, but writing down proofs is very difficult for me.   Basically, for (a), I ended up with some complicated statement involving an implication implying another implication and then tried to derive a contradiction. It just got so convoluted that I couldn't make sense of it anymore, and I know there's a quick, elegant way to show it.  For (b), I know that $g$ need not be surjective. Once again, though, proving it directly from definitions has given me a bit of a headache.  Any help here would be appreciated. Thanks in advance.  The Proofs!  Ok, I did it. Thanks for the help, everyone! Let me know if there's anything wrong with these proofs, or if they could bet any better.  (a) Suppose $f$ is not injective. Then $$ f(x_1)=f(x_2) \implies x_1 \ne x_2 \text{        }(*).$$ Let $f(x_1)=y_0=f(x_2)$ and let $g(y_0)=z_0$. Then $$ (g \circ f)(x_1) = (g \circ f)(x_2) = g(y_0) = z_0. $$ Since $g \circ f$ is injective, $$ (g \circ f)(x_1) = (g \circ f_2) \implies x_1 = x_2. $$ However, this contradicts $(*)$. Therefore, $f$ must be injective.  (b) Suppose $g$ is not surjective. Then  $$ \forall y \in Y, \exists z \in Z \text{ such that } g(y) \ne z \text{         }(**).$$  Since, $g \circ f$ is surjective,  $$ \forall z \in Z, \exists x \in X \text{ such that } g(f(x)) = z \text{       } (***). $$  Let $f(x) = y$. Then,  $$ g(f(x)) = g(y) = z. $$  Because of $(***)$, this is true for all $z \in Z$, which contradicts $(**)$. Therefore, $g$ must be surjective.


What's the general equation of a curve after a rotation about the origin?  Specifically, what's the equation (either piecewise or implicit) of the unit parabola after a counterclockwise $45^{\circ}$ rotation?    I feel the generalised rotation matrix should be all I need but I can't figure out where to go from here :(

Assuming I have the graph of a function $f(x)$ is there function $f_1(f(x))$ that will give me a rotated version of the graph of that function?  For example if I plot $\sin(x)$ I will get a sine wave which straddles the $x$-axis, can I apply a function to $\sin(x)$ to yield a wave that straddles the line that would result from $y = 2x$?


I observed in case of Mi phones like Redmi Note 4 & Mi Max2.  We’re not able to disable Google Apps like Chrome, Play Music, Play Movies & TV, etc.  Please let me know, how to disable Google apps?

I am trying to remove the Facebook and Messenger apps from my Asus Zenphone Laser 2.  Unfortunately, in both cases, I seem to be unable to find the option to fully delete them from the device. I have disabled them, but the app management screen now shows the following:     How can I fully delete/uninstall them?


In Revenge of the Sith, Palpatine orders clone commanders to execute 66 which is to kill the Jedi as their are now traitors to the Republic but why didn't the Clones kill Anakin since he is a Jedi.

. When activated, troopers would immediately perceive Jedi as a threat and kill them.  Since Anakin was a Jedi until around the time of the Order, how did the troopers know not to kill Anakin?


I am a new Ubuntu user with 12.04 lts and stepped away from my computer for a month and forgot my password.   Using this forum I attempted to reset my password using a root line upon booting in grub, I followed instructions to find I was getting results that no one else had gotten. asking for reset options that I didn't understand how to use, it said the the argument was invalid, So I found a way to delete my encrypted password in a nano list. I was able to log in but Sudo still seems to recognize a Password and even thought my user account profile says "none" after password I can't seem to do anything.  I don't know what else to do, hopefully it can be fixed. the long explanation was to show my inexperience and give light to any mistakes made.  Thank you

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?


I am looking for a way to combine 2 / potentially more columns into 1 column, where all values (text) of the source columns are combined with each other (covering all possible combinations of the values from the 2 columns):     Column 1 Column 2 Column 3     Value 1a Value 2a Value 1a + Value 2a   Value 1b Value 2b Value 1b + Value 2a   Value 1c Value 2c Value 1c + Value 2a     Value 1a + Value 2b     Value 1b + Value 2b     Value 1c + Value 2b     Value 1a + Value 2c     Value 1b + Value 2c     Value 1c + Value 2c

I have two columns such as:  a   1  b   2  c    and I need to combine them like:  a   1 a   2 b   1 b   2 c   1 c   2   Is it possible with a formula?


I am trying to get the user input using the following code but on running it gives the error that Arrayindexoutofbounds. Don't know what is the problem.  public static void main(String[] args) {     int T = Integer.parseInt(args[1]);     PercolationStats stats = new PercolationStats(             Integer.parseInt(args[0]), T);     double mean = stats.mean();     StdOut.println("mean = " + mean);     double stddev = stats.stddev();     StdOut.println("stddev = " + stddev);     double d = (1.96 * stddev) / Math.sqrt(T);     StdOut.println("95% confidence interval = " + (mean - d) + ", "             + (mean + d)); }

During development (and for debugging) it is very useful to run a Java class' public static void main(String[] argv)  method directly from inside Eclipse (using the Run As context menu).  Is there a similarily quick way to specify command line parameters for the run? What I do now is go to the "Run Dialog", click through the various settings to the tab where I can specify VM and program arguments and enter them there.  Too many steps, plus I do not want to mix the more permanent runtime configuration settings with the one-off invokation parameters. What I want instead is to check a box somewhere (or have a separate menu item "Run as Java application with command line") and then be prompted for the commandline every time (with a nice history).


I'm writing a paper now and I have the format problem as shown in the following snip   I follow the latex code for the table   \documentclass[sigconf]{acmart} \begin{table}[h] \centering \begin{tabular}{|c|c|c|c|c|} \hline    Brand & community & Neutral\_Average & Negative\_Average & Positive\_Average  \\ \hline    Apple & NEWS & 1.45 & 2.93 & 2.72 \\ \hline    Apple & Amazon & 0.069 & 0.39 & 0.71 \\ \hline    Apple & Twitter & 17.11 & 11.36 & 12.06 \\ \hline  Huawei & Amazon&0.076 & 0.20 & 1 \\ \hline  Huawei & Twitter& 13.56 & 5.3 & 10.58 \\ \hline  Huawei & NEWS&1.034 & 1.73 & 1.75 \\ \hline   Samsung & NEWS & 1.03 & 1.83 & 3.37 \\ \hline   Samsung & Twitter & 10.82 & 4.52 & 11.62 \\ \hline   Samsung & Amazon & 0.093& 0.35& 1.1 \\ \hline      \end{tabular} \caption{Average Brand Sentiment Per Community} \label{brand_senti_community} \end{table}

I have a table that I want to insert on a page, but at least one (perhaps both) of the following conditions are met:   The table is too wide to fit within the text block or page. That is, I'm exceeding some horizontal restriction. The table is too tall to fit within the text block or page. That is, I'm exceeding some vertical restriction.   What are my options to make this table fit? If it doesn't fit, regardless of my attempts, what other options exist?


Is there a stopwatch, so that I can measure time taken for different commands for BASH shell?

I'm trying to measure the execution time of a process that I call via the command line (i.e., I want to find out how long it takes to for the process to finish). Is there any command that I can add to the command calling the process that will achieve this?


So I'm using an older workstation Dell Precision 490 with the 3.0 dual core Xeon 4gb ram running a Quadro FX4600.  I dabble in Linux and know enough to be dangerous but am not fluent in command line shenanigans.  I installed the NVidia 340.107 drivers through the Software & Updates method. From what I've researched thats is correct and most up to date driver for my card.  After rebooting though I get some fascinating display art, glitches, text scrambling, etc.  Eventually the machine will lock up briefly, the screen will go blank for a few seconds, then come back on and everything appears to run smoothly from then on.  I've tried searching for the solution but other threads symptoms didn't appear to match my own.  Anyone able to explain whats going on, and how I could fix/prevent the start up glitch?

NB: Nvidia has released an official fix; please see ,  and/or .  Upon waking up Ubuntu 16.04 from Suspend, the following graphical glitches appear around all windows, context menus, and similar:      This is currently known to affect the following NVIDIA cards running the proprietary drivers:  NVIDIA GeForce 610M, driver version 375.39, 340.102 NVIDIA GT 630M, driver version 375.39 NVIDIA GTX 650, driver version 375.39 NVIDIA GT 740M, driver version 378.13 NVIDIA GTX 745, unknown driver version NVIDIA GTX 850M, driver version 375.39, 378.13 NVIDIA GT 940M, driver version 375.39 NVIDIA GTX 950M, unknown driver version NVIDIA GTX 960M, driver version 378.13 NVIDIA GTX 970, driver version 375.39 NVIDIA GTX 970M, driver version 375.39 NVIDIA GTX 980 TI, unknown driver version NVIDIA GTX 1060, driver version 375.26, 375.39, 378.09 NVIDIA GTX 1070, driver version 378.09  The above above list has been sourced from reports from other users here on AU,  thread, and  thread. NB: This is be no means an exclusive list. It probably effects nearly all Nvidia cards.  Furthermore, this issue has been replicated on a clean install where the only change was a software update and the installation of the latest NVIDIA drivers.  What is going on, and how can it be resolved?


I have two radio buttons with the same name but different values. I have to check before I submit my form that value selected id correct otherwise give message to user.   Here is my HTML code:        <input type="radio" name="directed" value="1" id="directed_yes">    Yes
      <input type="radio" name="directed" value="0" id="directed_no">    No   	   Here is my JQuery that i tried to use:  var directed = $('input[name=directed]').each(function(){   alert($(this).val()) });   This code gave me all values for elements with the same name, I just need selected value. After that I have to check if that value is valid before submitting the form. If anyone know how to get just selected value please let me know. Thanks.

I have two radio buttons and want to post the value of the selected one. How can I get the value with jQuery?  I can get all of them like this:  $("form :radio")   How do I know which one is selected?


p203 of the 5e PHB indicates that     A character can use a component pouch or spell casting focus in place of the components specified for a spell. But if a cost is indicated for a component, a character must have that specific component before he or she can cast the spell...   So, if I'm starting out as a Knowledge Domain cleric, I get Identify as a level 1 Domain spell - normally this requires "A pearl worth at least 100 gp and an owl feather."  I'm assuming that a holy symbol would stand in in place of the feather, but I still need the pearl to cast?

In D&D 5E, if you have a focus (like bards have instruments and clerics have holy symbols) for your spell casting do you need to pay for materials?


Let $S_1:=\{(x,y\in\mathbb{R}^2:x^2+y^2=1\}$ and $S_2:=\{x,y\in\mathbb{R}^2:\max\{|x|,|y|\}=1\}$ be endowed with subspace topologies induced by the usual topology on $\mathbb{R}^2$.  Then open sets in $S_1$ and $S_2$ are unions of open intervals in $S_1$ and $S_2$ respectively.  Partition $S_1$ into four arbitrary non-empty disjoint open sets $A,B,C,D$ and four distinct points, $a,b,c,d$.   Similarly, partition $S_2$ into four disjoint open sets $A',B',C',D'$ and four points $(1,1), (1,-1), (-1,-1), (-1,1)$, where $A'$ is the right vertical side of the square, $B'$ is the bottom side of the square, etc.  Let $f:S_1\rightarrow S_2$ be a function such that $f(A):=A',f(B):=B',f(C):=C',f(D):=D'$, and $f(a):=(1,1),f(b):=(1,1),f(c):=(1,1),f(d):=(1,1)$.   It seems that $f$ is bijective and continuous, and $f^{-1}$ is also continuous, but I can't give a rigorous proof.

Can we find a homeomorphism from the square $Q_2$ of side length $2$ centered on the origin and the unit circle $S^1$?  We can easily define a map $r:Q \longrightarrow S^1$ by  $$(x,y) \mapsto  \bigg(\frac{x}{\sqrt{x^2+y^2}},\frac{y}{\sqrt{x^2+y^2}} \bigg)$$ which is a radial projection onto the unit circle, but how can we define $r^{-1}$ and show that it is continuous?   Thoughts  I think we may define the inverse map as   $$(x,y) \mapsto \bigg(\frac{x}{\sqrt2\max{│x│, │y│}} , \frac{y}{\sqrt2\max {│x│, │y│}}\bigg)$$At least intuitively this maps to a square, and the $\frac{1}{\sqrt2}$ term scales appropriately. However, how can we demonstrate these are continuous maps, thus demonstrating that $Q_2$ and $S^1$ are homeomorphic?  Any help would be appreciated. Regards, MM.


What is the size (sizeof(How_Many_Bytes)) of the following structure, given the following machine  parameters:   sizeof(char) == 1; sizeof(int) == 4; sizeof(long) == 8; sizeof(char *) == 8;    Integer values must be aligned.   typedef struct how_many_bytes {   long s;   char c, e;   int i;   char *d;  } How_Many_Bytes;    I thought it would be 4+1+1+(2+4)+8 = 20 bytes but when I run on my machine I get 24 bytes. I wonder why?

Why does the sizeof operator return a size larger for a structure than the total sizes of the structure's members?


I don't understand the following behavior:  to verify, I have a fresh default/standard wp installation (no themes, no plugins)  I change in settings the permalink structure to "post name".  I create two pages and call them eg "sub1" and "sub2".  now I create a 3rd-page "test" with "sub1" as the parent.  so the link .../sub1/test works as expected but if I call .../sub2/test (which does not exist) I would expect a 404. instead, I can see a 301 and the page "test" under .../sub1 is displayed.  I tested this on many different WordPress installations (and versions) it seems to be the default behavior with permalink set to "post name"  but technically that's a wrong implementation.  is there a reason for this implementation and is there a way to "correct" this with some hooks ???

hey all! i have an odd problem with URL routing. when i request a URL that doesn't exist, e.g. , wordpress correctly returns a 404. however, if that URL is a prefix of a post or page name, it instead returns a 301 redirect to the post or page.  for example, if i have a post on 10/1/2010 named Food Post, it will return a 301 with Location:  (my permalink structure). likewise, if i have a page named Food Page, it will return a 301 with Location: .  you can see this in action on my live site,  . e.g.  redirects to  .  turning off permalinks (ie switching to "default") fixes it, for both posts and pages, but naturally i don't really want to do that.  i see this on three different installations, all wordpress 3.0.1 and apache 2.2, two ubuntu lucid/mysql 5.1 and one freebsd 7.3/mysql 5.0. i've deactivated all plugins and removed everything from my .htaccess except the lines for wordpress below, verbatim, but no luck.  RewriteEngine On RewriteBase / RewriteRule ^wordpress/index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /wordpress/index.php [L]   thanks in advance...


When I was studying about minimal polynomials and polynomials I came across the following theorem. Theorem: Let $p(x) \in \mathbb{F}[x]$ be a non-constant monic polynomial. Then $p(x)$ is a unique (up to order) product of irreducible polynomials. Can someone please help me to understand why they say as "up to order"? In certain other places also I've come across such phrases like "up to isomorphism" etc. What is implied by saying "up to...something"? Thanks a lot in advance.

I have begun seeing the phrase "up to" a lot after taking abstract algebra. I usually can figure out what means in context.  For example, $\mathbb Z_4$ equals the set of rotations of a square, up to isomorphism.  I just don't really understand why we use it and what it actually means. The way I interpret it is sort of that, if "isomorphism" were a person, then $\mathbb Z_4$ would equal the rotations of a square, if it were up to them.  Another explanation I've seen on Wikipedia is that $A=B$, up to $x$ means that $A$ would equal $B$ if it weren't for $x$. That just doesn't make sense to me considering the first example I gave.  I hope this isn't too vague of a question, but it seems like the phrase itself is a bit vague. I guess I'm trying to find a casual understanding of how to use the phrase.


friend's      I have to parse the description from url,where parsed  content have few html tags,so how can I convert it to plain text.

Is there a good way to remove HTML from a Java string? A simple regex like replaceAll("\\<.*?>", "")   will work, but things like &amp; wont be converted correctly and non-HTML between the two angle brackets will be removed (i.e. the .*? in the regex will disappear).


When I play the game it works perfectly fine but it shows an error in the console when pressing buttons but it is still working just causing a bit of lag.   This is the error: NullReferenceException: Object reference not set to an instance of an object uiManager.Update () (at Assets/Scripts/uiManager.cs:31)  using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.UI; using UnityEngine.SceneManagement;  public class uiManager : MonoBehaviour {  public Button[] buttons; public Button resume; public Button pause; public Text scoreText; public Text hiScore; public Text newHighScore; public Text optionsResetPrompt; int score; bool gameOver;  // Use this for initialization void Start () {     pause.gameObject.SetActive(true);     resume.gameObject.SetActive(false);     gameOver = false;     score = 0;     InvokeRepeating("scoreUpdate", 0.5f, 0.25f);     hiScore.text = PlayerPrefs.GetInt("highscore").ToString(); }  // Update is called once per frame void Update () {     scoreText.text = "" + score; }  void scoreUpdate(){     if (gameOver == false) {         score += 1;     }   } public void gameOverActivated(){     gameOver = true;     pause.gameObject.SetActive(false);     resume.gameObject.SetActive(false);     foreach (Button button in buttons) {         button.gameObject.SetActive(true);     }     int highestScore = PlayerPrefs.GetInt("highscore", 0);     if (score > highestScore){         PlayerPrefs.SetInt("highscore", score);         newHighScore.gameObject.SetActive(true);         }  }  public void Play() {     SceneManager.LoadScene("level1"); }  public void Menu() {     SceneManager.LoadScene("Menu");     if (Time.timeScale == 0)     {         Time.timeScale = 1;     } }  public void Reset() {     PlayerPrefs.DeleteKey("highscore");     optionsResetPrompt.gameObject.SetActive(true); }  public void Options() {     SceneManager.LoadScene("Options"); }  public void Retry() {     SceneManager.LoadScene(SceneManager.GetActiveScene().name);     if (Time.timeScale == 0){         Time.timeScale = 1;     } }  public void Pause() {      if (Time.timeScale == 1) {         Time.timeScale = 0;         pause.gameObject.SetActive(false);         resume.gameObject.SetActive(true);         foreach (Button button in buttons)         {             button.gameObject.SetActive(true);         }     }  } public void Resume() {       if (Time.timeScale == 0) {         Time.timeScale = 1;         pause.gameObject.SetActive(true);         resume.gameObject.SetActive(false);         foreach (Button button in buttons)         {             button.gameObject.SetActive(false);         }     } } }

Since many users are facing the NullReferenceException: Object reference not set to an instance of an object error in Unity, I thought that it would be a good idea to gather from multiple source some explanation and ways to fix this error.  Symptoms I am getting the error below appearing in my console, what does it mean and how do I fix it?  NullReferenceException: Object reference not set to an instance of an object


Are ought and ought to used in American daily speech ? Are these words common in American English? Maybe there is any other alternativs which are being used in American English?

Do native speakers still use "ought to" in daily conversation?  I haven't seen "ought to" used on any social or news ... websites.  I only read about it in English grammar books.    :        :        UPDATE:   Is "ought to" still used by native speaker of American English? Is "ought to" still used by native speaker of British English?


Even in empty space virtual particles can constantly pop in and out of existence in pairs, when 1 of the pair fall into the black hole while the other escape this is hawking radiation but black hole feeds on virtual particles so I am confuse when people says black hole lose mass via hawking radiation. Are they mistaken or did I wake up on the wrong side of bed?

I was reading Brian Greene's "Hidden Reality" and came to the part about Hawking Radiation. Quantum jitters that occur near the event horizon of a black hole, which create both positive-energy particles and negative-energy particles, produce the so-called Hawking radiation. However, I do not understand why only the negative-energy particles are being absorbed into the black hole, while the positive-energy particles shoot outward. Shouldn't there be 50/50 chance that each type of particle is being absorbed by the black hole? Also, the book mentions that a negative-energy particle would appear to an observer inside the black hole as positive. Why?


Yes, it's a small issue. But, it occurs in many areas of the Stack Exchange Sites.  I found this issue in  Question with one view   In the review History Page    Rest of the things are on the hover messages, I've tried them on both Firefox and Chrome.   See the below screenshots,        Do we need to fix this type of issues?  I think, Yes.

As seen at:           Update: I'm 101% sure the down votes were due to the lack of free hands.    Update 2: likes me, like me not, like me, likes me not... yeah !


I am currently using Ubuntu 16.04. There is something in Xubuntu that I love, and it's an option to minimize an open application as an icon on the desktop.    When I was a Windows user I used a program that minimized programs as thumbnail on the desktop. This option is very useful when you have lots of programs open. I was wondering if there's any option to bring this feature to Unity?

On Irix's  4Dwm, there was an ability to minimise windows into a box (contrary to the task bar used by modern window managers). I have seen this also on an old HPUX.  See the "console" square in the linked image:    Is it possible to accomplish on Ubuntu, either with a plugin or maybe some  window manager other than Unity?


I have read through all the posts really but still not able to figure this out. I want to pass the no. of hours that are input on the VF Page back to the controller. Basically, user should be able to update the no. of hours on his saved Timesheet. Below is my VF Page -  <apex:page standardController="Project_Timesheet__c" extensions="i3_ProjectTimesheet_Controller_Edit" sidebar="false"> <apex:inputText value="{!TSHours}" label="Hours" id="TSHours"/>    Below is my extension     public class i3_ProjectTimesheet_Controller_Edit {  public i3_ProjectTimesheet_Controller_Edit(ApexPages.StandardController stdController)  {         CurrentTS = (Project_Timesheet__c)stdController.getRecord();         CurrRecId = ApexPages.currentPage().getParameters().get('Id'); TSRecord = [Select Contract__c, Assigned_To__c, Account__c, Project__c, ProjectPhase__c, Hours__c, Comments__c, Date__c from Project_Timesheet__c where ID = :CurrRecId]; } public decimal TSHours  {   get {         return TSRecord[0].Hours__c;         }    set; } public PageReference Save() {   system.debug (TSHours); }   What am I missing?

Im having a VF page it has some text fields and one button . On clicking the button , the values in the text field should be passed to the controller class to save in the database . Can this be achieved . If yes , direct me .


Since I can remember, my Windows 7 always shows 6 icons for fictitious Removable Disks. They aren't a problem, really - when I insert a real USB stick, it shows as yet another icon (but working).  But they are a mystery, and I've always wondered where they come from, why are there 6 Removable Disk icons for disks that don't really exist.  If I try to open any of them, I only get this dialog saying:     Please insert a disk into Removable Disk K:     So where do these icons come from? I most definitely don't have 6 USBs attached to my computer, or anything like that.

I've recently had some "Removable Disk" listings mysteriously appear along with my other drives. Clicking on one of them results in a dialog box:     Please insert a disk into Removable Disk (G:). "Properties" has no usable data.   How do I delete these "Removable Disk" listings?  Computer Local Disk (C:) Data2 (D:) DVR (E:) BD-ROM Drive (F:) DVD Removable Disk (G:) Removable Disk (H:) Removable Disk (I:) Removable Disk (J:) Maxtor .5GB Set 2 LR Sec (K:) LR3 Set3 Pri Seagate2TB (L:) Grn Mxtr .5GB Bkup of Mxtr .5GB (M:) Maxtor .5GB Set 2 LR Primary (N:) Removable Disk (O:)