I am trying to write a code as efficient as possible and I encountered the following situation:    int foo(int a, int b, int c)  {     return (a + b) % c;  }   All good! But what if I want to check if the result of the expression to be different of a constant lets say myConst. Lets say I can afford a temporary variable.   What method is the fastest of the following:  int foo(int a, int b, int c)  {     return (((a + b) % c) != myConst) ? (a + b) % c : myException;  }    or  int foo(int a, int b, int c)  {     int tmp = (a + b) % c     return (tmp != myConst) ? tmp : myException;  }   I can't decide. Where is the 'line' where recalculation is more expensive than allocating and deallocating a temporary variable or the other way around.

Is it more efficient for a class to access member variables or local variables? For example, suppose you have a (callback) method whose sole responsibility is to receive data, perform calculations on it, then pass it off to other classes. Performance-wise, would it make more sense to have a list of member variables that the method populates as it receives data? Or just declare local variables each time the callback method is called?  Assume this method would be called hundreds of times a second...  In case I'm not being clear, here's some quick examples:  // use local variables class thisClass {     public:         void callback( msg& msg )         {             int varA;             double varB;             std::string varC;             varA = msg.getInt();             varB = msg.getDouble();             varC = msg.getString();              // do a bunch of calculations          }  };  // use member variables class thisClass {     public:         void callback( msg& msg )         {              m_varA = msg.getInt();              m_varB = msg.getDouble();              m_varC = msg.getString();               // do a bunch of calculations         }      private:         int m_varA;         double m_varB;         std::string m_varC;  };


This is a follow up question of this question:   Updating to texlive 2015 (with siunitx 2.6h) seems to have broken the accepted answer. So the question is  How to make siunitx and X column type work together for the very last modification introduced (possibly) in texlive 2015?  Broken MWE  \documentclass{article}  \usepackage{array} \usepackage{tabularx} \usepackage{siunitx}   \begingroup % Allow `_` and `:` in macro names (LaTeX3 style) \catcode`\_=11 \catcode`\:=11 % Internal code of `S` \gdef\tabularxcolumn#1{%     >{\siunitx_table_collect_begin:Nn S{} }%     p{#1}%  <- this is different (is `c` in normal `S`)     <{\siunitx_table_print:}% } \endgroup  \begin{document}  \begin{tabularx}{\textwidth}{p{1.5cm} XXX}      bla & 1.23 & 4.5  & 67.89 \\      bla & 1.2  & 4.50 &  7.89 \\      bla &  .2  &  .50 & 67.8 \\ \end{tabularx} \end{document}   Output error:  ! Undefined control sequence. <template> ...\TX@col@width }\siunitx_table_collect_begin:Nn                                                    S{} \ignorespaces    If you consider that this is a duplicate, I will promptly delete this question as soon as someone will add an up-to-date answer to the other question.

I'm using the tabular features of siunitx (for what it is worth: v1.3 since I'm on TexLive 2009) to align numbers in tables, eg.  \begin{tabular}{ p{1.5cm} S S S } bla & 1.23 & 4.5 & 67.89 \tabularnewline \end{tabular}   and that works perfectly fine.  Now I would like to have this table span a specific width, or rather to have several tables to have the same width. For this I would normally use tabularx  \begin{tabularx}{\textwidth}{ p{1.5cm} X X X } bla & 1.23 & 4.5 & 67.89 \tabularnewline \end{tabular}   Now, is there a way to combine the two? To have the number formatting and alignment features of siunitx inside an automatically resizing table?


If the Planck length is the smallest unit of length that has any physical meaning then is it true to think that all the lengths are multiple of the Planck length?

On a quantum scale the smallest unit is the , which is a discrete measure.  There several question that come to mind:   Does that mean that particles can only live in a discrete grid-like structure,  i.e. have to "magically" jump from one pocket to the next? But where are they in between? Does that even give rise to the old paradox that movement as such is impossible (e.g. )? Does the same hold true  for time (i.e. that it is discrete) - with all the ensuing paradoxes? Mathematically does it mean that you have to use difference equations instead of differential equations? (And sums instead of integrals?) From the point of view of the space metric do you have to use a discrete metric (e.g. the ) instead of good old Pythagoras?   Thank you for giving me some answers and/or references where I can turn to.  Update: I just saw this call for papers - it seems to be quite a topic after all: Is Reality Digital or Analog? FQXi Essay Contest, 2011. , , . One can find some pretty amazing papers over there.


I was wondering what is wrong with the following line:  \(\mathbf{W} \in \mathbb{R}^{\geq{0}, \mathit{R} \times \mathit{N}}\)   I am trying to reproduce this:    But get a:  Undefined control sequence. l.542 ...egative matrices \(\mathbf{W} \in \mathbb                                                   {R}^{\geq{0}, \mathit{R} \...

I am doing my first LaTeX work using TeXstudios and I'm having trouble with an Undefined control sequence.   When I've checked solutions on google it appears as this is caused by typos in the different commands.  However, I have used the TeXstudios implemented menus to generate the codes so it shouldn't be any problem with that.  The code I'm having trouble with is  $x\in\mathbb{R}^{n}$   which I intend to become x belonging to the real numbers with n as an exponent.   I get the error   Undefined control sequence $x\in\mathbb


I have a image below, kinda hard to see but was wondering if anyone has seen this formula and what its from and how to use it.  thx  $$A=\frac{1}{2}\sum\limits_{i=0}^{n-1}(x_iy_{i+1}-x_{i+1}y_i)$$

I was searching for methods on how to calculate the area of a polygon and stubled across this: . $$ \mathop{area} =  \left\lvert\frac{(x_1y_2 − y_1x_2) + (x_2y_3 − y_2x_3) + \cdots                   + (x_ny_1 − y_nx_1)}{2} \right\rvert $$ where $x_1,\ldots,x_n$ are the $x$-coordinates and $y_1,\ldots,y_n$ are the $y$-coordinates of the vertices. It does work and all, yet I do not fully understand why this works.  As far as I can tell you take the area of each triangle between two points. Basically you reapeat the formula of $\frac{1}{2} * h * w$ for each of the triangles and take the sum of them? Yet doesn't this leave a "square" in te center of the polygon that is not taken into account? (Apparently not since the correct answer is produced yet I cannot understand how).  If someone could explain this some more to me I would be grateful.


I want to label my enumeration like SOMETEXT01, SOMETEXT02, ..., SOMETEXT10, etc. I read through a couple of questions and know how to create a counter that adds in leading zeros.  \newcounter{counter} \newcommand*{\getCount}{%   \ifnum\value{counter}<10 0\fi%   \arabic{counter}% } \getCount \setcounter{counter}{10} \getCount   How can I use it with the labeling?  \documentclass[12pt]{article}  \usepackage[T1]{fontenc} \usepackage[latin1]{inputenc} \usepackage{enumitem} \usepackage{ae} \usepackage[pdftex]{graphicx} \usepackage{vmargin} \usepackage{url} \usepackage[absolute,overlay]{textpos} \usepackage[german]{babel}  \newlist{frequirements}{enumerate}{3} \setlist[frequirements, 1]{labelindent=0pt, label*=\textbf{/FR{\arabic*}/},itemindent=0em,leftmargin=*}   \begin{frequirements}     \item \textbf{Do this} \\ You should always be able to do this.     \item \textbf{Validate} \\     After doing this, the user should be able to validate. \end{frequirements}  \end{document}     Output looks like  /FR1/ Do this  You should always be able to do this.  /FR2/ Validate  After doing this, the user should be able to validate.

How to make enumerate list format numbers like this:     REG/001 (content)      REG/002 (content)      REG/003 (content)   I already managed to do the following:   \begin{enumerate}[label=\textbf{REG/\arabic*},leftmargin=*] \item content \end{enumerate}   using   \usepackage{enumitem}   but I don't know how to add leading zeros.


if i browse localhost/visiondms it shows, Fatal error: require_once(): Failed opening required 'C:\xampp\htdocs\visiondms/wp-admin.php' (include_path='C:\xampp\php\PEAR') in C:\xampp\htdocs\visiondms\index.php on line 10 Please tell my what can i do?

I'm trying to install , an open-source Microblogging application on my Windows development server using XAMPP as per the . The website cannot find PEAR, and throws the below errors:  Warning: require_once(PEAR.php) [function.require-once]: failed to open stream: No such file or directory in C:\xampplite\htdocs\laconica\lib\common.php on line 31 Fatal error: require_once() [function.require]: Failed opening required 'PEAR.php' (include_path='.;\xampplite\php\pear\PEAR') in C:\xampplite\htdocs\laconica\lib\common.php on line 31   PEAR is located in C:\xampplite\php\pear phpinfo() shows me that the include path is .;\xampplite\php\pear  What am I doing wrong? Why isn't the PEAR folder being included?


I installed Ubuntu 12.10 on a computer and accessed the wireless network on which I have  primary and secondary computers running on Windows 7.  I can see both computer icons on all computers except I cannot see the Ubuntu computer on the network.   How do I add it to the network?

I have a desktop (Ubuntu 13.04 & Win 7 Home Premium) and a Laptop (Ubuntu 12.04), both having WiFi adapters. I also have a WiFi router connected to internet which both my computers can access.  I want to share files between my desktop and my laptop using WiFi (similar to Homegroup on Windows 7 but without using Ethernet cables).  How do I set-up that?  I want to share files using both OSs, if anyone have have information about sharing files with any of the OS please answer!


When the bootable pendrive is inserted option is asked if ubuntu should be installed or try ubuntu but if pendrive is not connected a message appears claiming no bootable drive found As a result every time i start my pc i need to install it  Plz help !

I had Ubuntu 12.04 Beta installed on my computer. When 12.04 was finally released, I made a bootable USB Flash Drive using Startup Disk Creator.  Then I decided to check if this drive works properly and to reinstall the system on my desktop. I must add, my desktop behaves a bit strange when it comes to bootable USB's, it recognizes them as HDD.  In BIOS I changed priority of boot so USB Flash Drive (recognized as HDD) was first. Successfully booted, I installed Ubuntu. Everything worked fine, but...  Now I cannot boot from my real HDD. Every time I want to boot, I put the USB Flash Drive into my computer, boot, safely remove it and everything works.  What do I need to do to repair boot?


Are there public key schemes that have perfect secrecy? The perfect secrecy notion is defined for symmetric key encryption. If P is a message and C the corresponding ciphertext then the cipher has perfect secrecy if pr(P|C)=pr(P). This equivalently means in terms of entropy that the conditional entropy H(P|C)=H(P). Originally as defined in Shannon's paper the encryption system is not classified as block or stream cipher. In practice it has to be one of the two and the message length is a priori fixed to a maximum. Hence for a public key scheme with the message length fixed perfect secrecy is still meaningful when probability distribution of the maximum length message is considered. In general H(P|C)< H(P). Since all public key schemes are secured in computational sense H(P|C)=0 which means an infinitely powerful adversary can always break the encryption. Can a perfectly secure public key scheme be defined? If there is one which scheme is it?

Assume there is a public-key encryption scheme $(KeyGen, Enc, Dec)$ with perfect correctness (i.e., for all messages M and valid key-pairs (PK,SK), we have $Dec_{SK}(Enc_{PK}(M))=M$).  Will there always be a function $A$ such that for all messages M and valid public-keys PK, $A_{PK}(Enc_{PK}(M))=M$?  In other words, can a computationally unbounded adversary decrypt the message, having only the public key?


I have a bash script which is running a python script which is run (or at least trying to be) by cron. I have already given cron full disk access (that gave a different error message). I'm on macOS Big Sur. crontab: * * * * * /Users/JohnG/Desktop/ControlPhone  mail: X-Cron-Env: <SHELL=/bin/sh> X-Cron-Env: <PATH=/usr/bin:/bin> X-Cron-Env: <LOGNAME=JonhG> X-Cron-Env: <USER=JohnG> Message-Id: <20210109053501.1C01930132F58E@Johnys-MacBook.local> Date: Fri,  8 Jan 2021 21:35:00 -0800 (PST)  /Users/JohnG/Desktop/ControlPhone: line 3: adb: command not found Traceback (most recent call last):   File "/Users/JohnG/Desktop/start.py", line 1, in <module>     import pythonmodulex ModuleNotFoundError: No module named 'pythonmodulex'

I have a script that works when I run it from the command line, but when I schedule it with cron I get errors that it cannot find files or commands.  My question is twofold:   When I schedule a cron job using crontab -e, does it use my user ID as the basis for its permissions?  Or does it use a cron user ID of some sort and its related permissions? When a cron job is launched, what is the working directory?  Is it the directory where I specify the script to run, or a different directory?   Here is my cron job:  15 7 * * * /home/xxxx/Documents/Scripts/email_ip_script.sh   Here is the actual script:  vIP_ADDR="`curl automation.whatismyip.com/n09230945.asp`" echo "$vIP_ADDR" sed "s/IPADDR/$vIP_ADDR/g" template.txt > emailmsg.txt ssmtp XXXXX@gmail.com < emailmsg.txt   Here are the errors I get when I view the mail message produced by cron:  sed: can't read template.txt: No such file or directory /home/xxxx/Documents/Scripts/email_ip_script.sh: line 15: ssmtp: command not found   It cannot find the template.txt but it resides in the same directory as the script.  It also cannot run ssmtp, but I can as my user.  What am I missing to get this to work properly?


Serana from Dawnguard DLC is following me when I don't want her to.   I have a stealthy playing style so it's annoying when I constantly have her behind me.   The setting looks like this: She follows me automatically if I open her dialogue she says something about her brother and continues to follow me.   When I press follow me she says: I knew you'd miss me. But when I open her dialogue again it does the same thing.   I'd like to have her operate as the standard npcs with all the normal actions.  Any other npc from Dawnguard doesn't have this problem only Serana. I tried to  turn it off all but all mods I've found don't work!

I told my follower (Serana) to wait. But this is different. I told her to go somewhere and wait so it will activate the enemies. Well it did and I killed them. But Serana seems to be not following me anymore. I can't tell her to follow me. And she is constantly in a squatting position. The only thing I can do is tell her to wait somewhere else to move her. And I can't part ways because I'm doing a main quest and she has to be there. Can anybody give me a tip on what to do?


So. I have windows 7 and Ubuntu right now. And i want to add windows XP too. I did some research and found out that you need to install everything in order from XP to Ubuntu. But i have windows 7 and Ubuntu already. And i want to ask is there a way without re-installing Windows 7 and Ubuntu. P.S.: Thanks to anyone who will reply.

Currently I am using a dual boot with Windows7 and Ubuntu 12.04LTS.  I would like to try Windows8. Not because I like it, but more and more people are using it.  I have created a partition where I would like to install it. I have only one physical drive.  What should I do to create a triple-boot and don't mess up my Ubuntu? This is my primary OS. But occasionally I need my Windows7.


Here is my original /etc/sudoers.d/www file:  Cmnd_Alias WWWCMDS = /home/xxx/shop/update.sh www-data ALL=(ALL) NOPASSWD: WWWCMDS   I simply want to add two additional commands so I RTFM and saw that you just have to comma-separate them.  Cmnd_Alias WWWCMDS = /home/xxx/shop/update.sh,geoipupdate,service memcached restart www-data ALL=(ALL) NOPASSWD: WWWCMDS   But it triggered a syntax error. What am I doing wrong ?

I have one script to allow for one user to run. The string calling it from the command line looks like  ./script path/to/folder -a option='value'   When I try to add it to the other commands in Cmnd_Alias line, sudo blames sudoers file for incorrect syntax. How can I set such commands properly?


I tried Math.round and String.format function to round float/double values.   1) Using Math.round function  Math.round(floatValue* 10.0) / 10.0;   For floatValue 40.55, result is 40.6 //Correct & Expected result.  For floatValue 30.05, result is 30.0 //Incorrect result. Expected result: 30.1  2) Using String.format function  String.format("%.1f", floatValue);   For floatValue 40.55 result is 40.6    //Correct & Expected result.  For floatValue 59.65 result is 59.6 //Incorrect result. Expected result: 59.7  Why same function is behaving differently for different float values.

What I would like is a method to convert a double to a string which rounds using the half-up method - i.e. if the decimal to be rounded is 5, it always rounds up to the next number. This is the standard method of rounding most people expect in most situations.  I also would like only significant digits to be displayed - i.e. there should not be any trailing zeroes.  I know one method of doing this is to use the String.format method:  String.format("%.5g%n", 0.912385);   returns:  0.91239   which is great, however it always displays numbers with 5 decimal places even if they are not significant:   String.format("%.5g%n", 0.912300);   returns:  0.91230   Another method is to use the DecimalFormatter:  DecimalFormat df = new DecimalFormat("#.#####"); df.format(0.912385);   returns:  0.91238   However as you can see this uses half-even rounding. That is it will round down if the previous digit is even. What I'd like is this:  0.912385 -> 0.91239 0.912300 -> 0.9123   What is the best way to achieve this in Java?


I'm trying to install win 7 on dell xps laptop. I burned the win7 on my 16 gb flash with no issues. When installing windows ,"no device drivers were found" error appears. I installed the drivers, and copied to usb, but it is not appearing in "Browse" OPTION, it shows only :   c: RECOVERY D: LOCAK DISK E: CD DRIVE X: BOOT   So my Question is : Why usbs are not appearing so I can select the drivers to be downloaded?

I have an Asus R500VD laptop which came with the preinstalled Windows 8. As actually this computer will be used by my grandmother (and she's only using win 7) I'd like to downgrade it.  Thanks to other thread here, I was able to successfully boot computer from Windows 7 USB stick, but unfortunately during install I got a message:  A required CD/DVD drive device driver is missing. (...)   and I can't get pass it... This is what I've done:   I've downloaded all drivers from Asus Website (), unzip and copied to visible location for windows 7 installation - I've picked each one of them, none has helped. As I belive it's some kind of problem with SATA/RAID/AHCI drivers I went to Intel site and downloaded various "Intel Rapid Storage Technology" drivers - a lot of them were recognized by win7, but none of them helped.   Does anyone have an idea what can I do next? Any help would be really appreciated.


I just typed out a fairly long answer to a question, so it took a little while.  When I tried to post it I found I couldn't.  I refreshed and found the question had been voted to be placed on hold due to being too broad.  A couple of one liner answers had been added before the hold came into effect and I noticed one of them, after another refresh then became a much more detailed answer.  I then noticed it was by one of the users that had voted to place the question on hold for being too broad, which of course prevents further answers.  I wonder if it's a contradiction to allow people to answer questions and vote to close / hold them?  Surely supplying an answer is stating you think the question is worthy of remaining and therefore should be open to attract further answers?  Have I misunderstood this? (I'm new at contributing rather than just gleaning help from the site, so go easy!).

I've noticed quite a few cases () where people not only vote to close a question, but then also answer said question. At best this is just silly, and at worst it is totally hypocritical and seems almost like rep whoring (since often the closers answers are the only ones that remain to be voted on since no new answers can be given).  If you want to close a question, it makes more sense to simply add a comment if you feel the need to say something. This also leaves the option open for the author of the question to delete it if they want to. If the author realizes they've asked a duplicate, or they want to avoid the onslaught of downvotes that can often accompany a closed question, they should be allowed to delete it. However, if any answers to the question have upvotes, the author can't delete it.  So why do people answer and close? Should we try to crack down on this sort of thing, via either new features, clearly stating it in the FAQs, or just getting the word out through commenting when we see it?  EDIT: Just to clarify, I'm asking this in relation to SO, not MetaSO.


I prove that: $$ \begin{pmatrix} 1 & 1\\ 1 & 0 \end{pmatrix}^n =  \begin{pmatrix} F_{n+1} & F_n\\ F_{n} & F_{n-1} \end{pmatrix}$$ I succeeded to prove that by induction, now my question is how it's related with the Euclidean algorithm? Is there a connection?

Let $f_1, f_2,\dots,f_i,\dots$ be the Fibonacci sequence with $f_1=f_2=1$. For any $a,b\in\mathbb{N}$ with $a<b$, suppose the Euclidean algorithm takes $n$ long divisions to compute $\gcd(a,b)$. If $a\le f_j$, then $n\le j-1$, for $j\ge2$.   I want to prove this problem. But I can't see any connection between Fibonacci and Euclidean algorithm. If anyone can give a hint about first step, it will be very thankful.  My guess is to use induction.


Can someone explain the intuition behind this/ what the proof might look for this?  If $f$ is a continuous, real-valued function on $[a,b]$, then \begin{equation} \lim_{n\to\infty} \left(\int_a^b \left|f(x)\right|^ndx\right)^{1/n} = \text{sup}\{\left|f(x)\right| : x \in [a,b]\} \end{equation}  It seems like it's a way of averaging $\left|f(x)\right|$, similar to how the Lyapunov number is an average of all the slopes of an orbit in a dynamical system.

Let $f(x)$ be a continuous real-valued function on $[a,b]$ and $M=\max\{|f(x)| \; :\; x \in [a,b]\}$. Is it true that: $$ M= \lim_{n\to\infty}\left(\int_a^b|f(x)|^n\,\mathrm dx\right)^{1/n} ? $$  Thanks!


I'm an Indian citizen and I am currently a third-year student in engineering. I have been selected to work for  with VLC (VideoLAN) Organisation, which offered me an opportunity to visit their headquarters in Paris in June.  I did not have a passport, so quickly got one and applied for a Schengen visa. During the visa application process, I was asked the purpose of travel. I said attending a conference and tourism. When I got my biometrics receipt, it said my visa had been applied for under the business category. I was a bit surprised, but nothing could be done at that point. After a few days, my passport was returned with my visa refusal letter, stating the reason of refusal as "information provided is unreliable."  After I talked to my mentors at VLC, they agreed to let me try again and visit them in July. I will be applying shortly for my visa would like to know if there is anything else that I should include, apart from the usual documents.

Schengen refusal formulae can be difficult to understand sometimes.  Sometimes an applicant receives a refusal with:       Justification for the purpose and conditions of the intended stay was not reliable.     often accompanied by:       Your intention to leave the territory of the Member States before the expiry of the visa applied for could not be ascertained.   What is meant by this refusal reason?  What are they trying to say?


Suppose I have this method //task1.cpp template <typename T> void printElement(std::ostream &out, T s);  I want to define it later in another file to handle specific types like this: //main.cpp void printElement(std::ostream& out, int value); void printElement(std::ostream& out, std::string_view value);  However when I call this one. It throws me an error: undefined reference to printElement (ostream&, int) int main(){ int a =5 printElement(std::cout, a) }  Note: I can only change things inside task1.cpp . Any suggestions would be greatly appreciated!

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


Does someone know how to make one preg replace from this two? It should cut off: https://, http://, ., . or only www.  preg_replace("/^www\./", "", preg_replace("/https?:\/\/(www\.)?/", "", $hostname, 1), 1);

I'm developing an algorithm to parse a number out of a series of short-ish strings. These strings are somewhat regular, but there's a few different general forms and several exceptions. I'm trying to build a set of regexes that will handle the various forms and exceptions; I'll apply them one after another to see if I get a match.   One of these forms goes something like this:  X (Y) Z   Where:   X is a number I want to capture.  Z is static, pre-defined text. it's basically how I determine whether this particular form is applicable or not. Y is a a string of unknown length and content, surrounded by parenthesis.    Also: Y is optional; it doesn't always appear in a string with Z and X. So, I want to be able to extract the numbers from all of these strings:   10 Z 20 (foo) Z 30 (bar) Z   Right now, I have a regex that will capture the first one:  ([0-9]+) +Z   My problem is that I don't know how to construct a regex that will match a series of characters if and only if they're enclosed in parenthesis. Can this be done in a single regex?


How to hide/remove memtest86 menu entries from Grub2. I have Ubuntu 15.04

I have both Windows 7 and Ubuntu installed on a shared machine. Because a lot of the non-developers use Windows, I'd like to change the boot order to make it easier for them.  Currently the boot order looks like the following:   Ubuntu 11.10 kernelgeneric *86 Ubuntu 11.10 kernelgeneric *86 (safe boot)  Memory test Memory test Windows 7 on /dev/sda6   How do I change the default order so that Windows 7 is at the top of the list?   Windows 7 on /dev/sda6 Ubuntu 11.10 kernelgeneric *86 Ubuntu 11.10 kernelgeneric *86 (safe boot)  Memory test Memory test


I need to change baseoa to quake3. How would I go about doing that?

I have got the directory /home/user/oldname and I want to rename it to /home/user/newname. How can I do this in a terminal?


When Voldemort created Horcruxes, he divided the soul into it. Once he died only soul was present.  Then from where exactly his body came from? Peter Pettigrew used Harry's Blood but whose flesh he used to bring back Voldemort?

In the first book it seems that Voldemort has been reduced to nothing but a ghostly wisp. But IIRC by the fourth book he somehow has a body that is carried around by Wormtail. In the first book he needs someone to inhabit, by the fourth, he can't really move around, but he does have a body back which can hold a wand.  How did this transition happen?


I don't need the desktop and all the functionalities that come with it. Is it possible to replace it with a simple GUI application? So that after login I never see the desktop but instead my own application. What do I have to change to make this happen? I'm using raspbian if this is important.

I would like to make a debian system where you can only open one GUI program at boot, no other graphical interface, no minimize, or any X apart from that program, is there a way to do it on debian if possible, or any other custom distro? I just want to boot open the program and allow the user to only see and use that program.


Long ago I realized that manipulation of derivatives was possible using algebraic quantities. One could take a differential instead of derivatives $$ d[\sin x]=\cos x\ dx $$ $$ \frac{d[\sin x]}{dx}=\frac{\cos x\ dx}{dx}=\cos x $$ My question is about the analog of this process with integrals without a $dx$ for example $$ \frac{\int\sin x}{\int x} $$ Here $\int$ is the inverse of the $d$ operator. There is deliberately no $dx$ so the integrals cannot be evaluated in the traditional sense. This is more the foundation for an idea than anything explicit. Has this been looked at by anyone in the past? Does anyone know of anything similar to this?  edited remarks To clarify, consider $\int \sin x$. Because the input is not a differential but a finite quantity, it is expected that the integral would diverge to infinity. I desire to define how the integral diverges in a way like $$ \int \sin x=f(x)\int x $$ which is analagous to differentials (e.g. $d[\sin x]=\cos x\ dx$) and therefore the fraction $\frac{\int \sin x}{\int x}$ could be evaluated as a finite quantity $f(x)$. I'm not looking for a simple "you can't do that" or the definition of an integral in the conventional sense. I want to know if anyone has explored this unconventional expression or has any insight into how it might be evaluated or even what it means.  Marked as a duplicate, but probably because my new idea goes against what we were all taught in calculus class.

When I was at school and learning integration in maths class at A Level my teacher wrote things like this on the board.  $$\int f(x)\, dx$$  When he came to explain the meaning of the $dx$, he told us "think of it as a full stop".  For whatever reason I did not raise my hand and question him about it.  But I have always shaken my head at such a poor explanation for putting a $dx$ at the end of integration equations such as these.  To this day I do not know the purpose of the $dx$.  Can someone explain this to me without resorting to grammatical metaphors?


Sorry for the newb question. I'm trying to add a repository to my ubuntu machine:  $ sudo curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -  <<EOF >/etc/apt/sources.list.d/kubernetes.list deb https://apt.kubernetes.io/ kubernetes-xenial main EOFE: This command can only be used by root. (23) Failed writing body $ cat <<EOF >/etc/apt/sources.list.d/kubernetes.list > deb https://apt.kubernetes.io/ kubernetes-xenial main > EOF^C  But the command is 'breaking' in half when I try to run it by pasting it into the terminal. I'm having trouble with the cat EOF part of the command. This is the command that I want to run: sudo curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add - cat <<EOF >/etc/apt/sources.list.d/kubernetes.list deb https://apt.kubernetes.io/ kubernetes-xenial main EOF  This is on Ubuntu 20.04 LTS (Focal Fossa). cat /etc/lsb-release DISTRIB_ID=Ubuntu DISTRIB_RELEASE=20.04 DISTRIB_CODENAME=focal DISTRIB_DESCRIPTION="Ubuntu 20.04.1 LTS"  How can I get this working?

I'm on Ubuntu 16 and I'd like to add a neo4j package. I tried in 3 ways all leading to the same error.  These are my attempts:  wget -O - http://debian.neo4j.org/neotechnology.gpg.key | apt-key add -  sudo wget -O - http://debian.neo4j.org/neotechnology.gpg.key | apt-key add -  sudo -i wget -O - http://debian.neo4j.org/neotechnology.gpg.key | apt-key add -   But I always get this error message:  ERROR: This command can only be used by root. --2016-11-04  http://debian.neo4j.org/neotechnology.gpg.key Resolving debian.neo4j.org (debian.neo4j.org)... 52.0.233.188 Connecting to debian.neo4j.org (debian.neo4j.org)|52.0.233.188|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 4791 (4,7K) [application/octet-stream] Saving to: ‘STDOUT’  -                     0%[                    ]       0  --.-KB/s    in 0s         Cannot write to ‘-’ (Broken pipe).


public static void Main() {     Stream s1 = this.GetType().Assembly.GetManifestResourceStream("WindowsApplication1.sudhir.jpg");     Stream s2 = this.GetType().Assembly.GetManifestResourceStream("WindowsApplication1.sunil.jpg");     Bitmap img1 = new Bitmap(s1);     Bitmap img2 = new Bitmap(s2);      if (img1.Size != img2.Size)     {         Console.Error.WriteLine("Images are of different sizes");         return;     }      float diff = 0;      for (int y = 0; y < img1.Height; y++)     {         for (int x = 0; x < img1.Width; x++)         {             diff += (float)Math.Abs(img1.GetPixel(x, y).R - img2.GetPixel(x, y).R) / 255;             diff += (float)Math.Abs(img1.GetPixel(x, y).G - img2.GetPixel(x, y).G) / 255;             diff += (float)Math.Abs(img1.GetPixel(x, y).B - img2.GetPixel(x, y).B) / 255;         }     }      Console.WriteLine("diff: {0} %", 100 * diff / (img1.Width * img1.Height * 3));   Here I'm trying to match the two images and finding their difference but I'm getting this error      Keyword 'this' is not valid in a static property, static method, or static field initializer.   What's wrong and how can I fix this?

I'm trying to use the this keyword in a static method, but the compiler won't allow me to use it.  Why not?


I had developped a program in Java with eclipse using a MariaDb database .  I had imported the jdbc driver jar file of mariadb using build classpath  When I run the program in Eclipse, it's works fine.  But when i build the jar and run the program using the line command java -jar <my program path> I got this error :     Not suitable driver found for jdbc:mariadb   What does I missed ?  EDIT : Problem resolve thanks to this

I am trying to build an executable jar program which depends on external jar downloaded. In my project, I included them in the build path and can be run and debug within eclipse.  When I tried to export it to a jar, I can run the program but I can't when I try to press a button which includes function calls and classes from the external jar. I have edited the environment variables (Windows XP) CLASSPATH to include paths of all the external jar, but it doesn't work.  A point to note is that I got compile warnings while exporting my executable jar, but it doesn't show up any description about the warnings.  Would someone kindly provide a thorough guide on how to include an external jar program using eclipse?


I would like to know how to align paragraphs inside the 'Acknowledge' environment. Follow below a print of the PDF:  Thanks in advance!

I am just curious that the following format looks good to you or not? The preamble I used is just   \documentclass[12pt,a4paper]{article}  \usepackage{amsmath} \usepackage{amsthm} \usepackage{amssymb}   I don't feel it's so good because the first paragraph has no indent but the second does. If the first paragraph is much longer, than it's fine. But if not, it looks strange. Should I leave it, or you have suggestions for this?


I would like to get the camera to slowly rotate around a object and keep facing it. I would to this with key frames but then the camera would travel in strait paths. How could I do this?

I have an object at a fixed position in 3D space. I would like the camera to circle around it while facing it. I want to path of the camera to be circular in 2D, meaning that it does not move up or down.  I need this to be pretty accurate. I don't want to manually set a keyframe every frame for position and rotation. I would like to do this maybe with an expression, not with manual keyframing. I am not sure how to go about this but I think it is going to involve Python as well as some trigonometry.


I've quite a few questions in this regard:   Is there a theoretical limit?  What has been achieved till date?  What is commercially available today?  If there is a sudden exponential increase in price after a certain limit, what limit is that?

Is there such a thing as a maximum aperture that a lens can be open to?  What about a minimum aperture that it can be closed to?  Do these concepts even make any sense?  Is there a lens with the narrowest aperture in the world?  Is there one with the widest?


I'm using Ubuntu 14.04 via Virtual Box on a Windows 7 host. The NIC is a USB to Ethernet adapter.  The  states what can cause "packets dropped by kernel" but it doesn't state what causes "packets dropped by interface".  Can anyone shed some light as to why the interface may be dropping packets? Or how I can find out the reason for it dropping the packets?

Running, either in promiscuous mode or not :   tcpdump -i "$INTERFACE" -vvv -n -XX -S -s0 -e   I got a bunch of lines and this conclusion when I stopped it :  601 packets captured 938 packets received by filter 230 packets dropped by kernel   Why the difference ? Where are the 107 packets missing ? And is it possible at all to get/capture 100% of the packets on the local network - it's just me behind a router ?


I need to be able to activate apps on my iPad without human interaction. We have tried dropping batteries onto the screen but that only works if dropped within a few inches. Is there any material in existence that can activate a touchscreen without human involvement, nor through the use of a stylus?

I want to robotically touch an iPhone screen without any human intervention.   I've done some experiments but have not found a reliable solution. It seems even styluses that work through gloves still rely on the capacitive characteristics of the human body.    Carrot held by human works Carrot held in plastic clamp doesn't Pogo Stylus works held by human and held by human through clothes Stylus does not work held in plastic clamp.  Stylus works held in plastic clamp attached to human through clothes via jump lead. Stylus held in plastic clamp with jump lead dangling off seems to work most the time.   Is it possible to mimic the human element using capacitors and other components? What signal does the capacitive screen need to be triggered?  Thanks


Where did you get that chipset/ (anything you want IT to be) from?  Where did you get that chipset/ (anything you want IT to be)?   What's the difference in the two sentences? What's the significance of the preposition "From" in the first sentence?

Is the following sentence correct? I have some doubts about "category where ... fall into" phrase.     It is the category where most of the processed data falls into


I want to create the following image in TikZ/PGFplots.  Questions such as  are a good start, but I am not clear how to modify them to include row labels. A straightforward addition of rows, such as below, only gives an error.   \documentclass{standalone} \usepackage{colortbl} \usepackage{pgfplots} \usepackage{pgfplotstable}  \pgfplotstableset{     /color cells/min/.initial=0,     /color cells/max/.initial=1000,     /color cells/textcolor/.initial=,     %     % Usage: 'color cells={min=<value which is mapped to lowest color>,      %   max = <value which is mapped to largest>}     color cells/.code={%         \pgfqkeys{/color cells}{#1}%         \pgfkeysalso{%             postproc cell content/.code={%                 %                 \begingroup                 %                 % acquire the value before any number printer changed                 % it:                 \pgfkeysgetvalue{/pgfplots/table/@preprocessed cell content}\value                 \ifx\value\empty                     \endgroup                 \else                 \pgfmathfloatparsenumber{\value}%                 \pgfmathfloattofixed{\pgfmathresult}%                 \let\value=\pgfmathresult                 %                 % map that value:                 \pgfplotscolormapaccess                     [\pgfkeysvalueof{/color cells/min}:\pgfkeysvalueof{/color cells/max}]                     {\value}                     {\pgfkeysvalueof{/pgfplots/colormap name}}%                 % now, \pgfmathresult contains {<R>,<G>,<B>}                 %                  % acquire the value AFTER any preprocessor or                 % typesetter (like number printer) worked on it:                 \pgfkeysgetvalue{/pgfplots/table/@cell content}\typesetvalue                 \pgfkeysgetvalue{/color cells/textcolor}\textcolorvalue                 %                 % tex-expansion control                 % see https://tex.stackexchange.com/questions/12668/where-do-i-start-latex-programming/27589#27589                 \toks0=\expandafter{\typesetvalue}%                 \xdef\temp{%                     \noexpand\pgfkeysalso{%                         @cell content={%                             \noexpand\cellcolor[rgb]{\pgfmathresult}%                             \noexpand\definecolor{mapped color}{rgb}{\pgfmathresult}%                             \ifx\textcolorvalue\empty                             \else                                 \noexpand\color{\textcolorvalue}%                             \fi                             \the\toks0 %                         }%                     }%                 }%                 \endgroup                 \temp                 \fi             }%         }%     } }  \begin{document}      \pgfplotstabletypeset[     color cells={min=0,max=0.8,textcolor=-mapped color!80!black},     /pgfplots/colormap/greenyellow,     /pgf/number format/sci,row sep=crcr, ]{     \phantom{A} a   b   c   d\\     a 5e-1    8e-1    4.4e-2  1e-3  \\        b 0.050   -0.300  -0.200  -0.100 \\     c -0.20   0.1 0.100   0.200\\     d 0.005   0.300   0.40    0.800\\     d 0.8 0.030   0.050   0.70\\ } \end{document}

This is a follow-up question to:  (where also the code is taken from)  What I want to achieve (Excel draft):    What I got so far (see code at bottom):    What is missing:   Axis description with "Some Text" Removing the "xxx" hack to get the first column being recognized as strings   Possible solution for removing the "xxx" hack: I found that "automatic column numbering" was done here:  and my dream solution would be not only incorporating it to my heatmap but also extending it with "automatic row numbering".  Current Code:  \documentclass{standalone} \usepackage{colortbl} \usepackage{pgfplots} \usepackage{pgfplotstable}  \pgfplotstableset{     /color cells/min/.initial=0,     /color cells/max/.initial=1000,     /color cells/textcolor/.initial=,     %     % Usage: 'color cells={min=<value which is mapped to lowest color>,      %   max = <value which is mapped to largest>}     color cells/.code={%         \pgfqkeys{/color cells}{#1}%         \pgfkeysalso{%             postproc cell content/.code={%                 %                 \begingroup                 %                 % acquire the value before any number printer changed                 % it:                 \pgfkeysgetvalue{/pgfplots/table/@preprocessed cell content}\value                 \ifx\value\empty                 \endgroup                 \else                 \pgfmathfloatparsenumber{\value}%                 \pgfmathfloattofixed{\pgfmathresult}%                 \let\value=\pgfmathresult                 %                 % map that value:                 \pgfplotscolormapaccess                 [\pgfkeysvalueof{/color cells/min}:\pgfkeysvalueof{/color cells/max}]%                 {\value}%                 {\pgfkeysvalueof{/pgfplots/colormap name}}%                 % now, \pgfmathresult contains {<R>,<G>,<B>}                 %                  % acquire the value AFTER any preprocessor or                 % typesetter (like number printer) worked on it:                 \pgfkeysgetvalue{/pgfplots/table/@cell content}\typesetvalue                 \pgfkeysgetvalue{/color cells/textcolor}\textcolorvalue                 %                 % tex-expansion control                 % see http://tex.stackexchange.com/questions/12668/where-do-i-start-latex-programming/27589#27589                 \toks0=\expandafter{\typesetvalue}%                 \xdef\temp{%                     \noexpand\pgfkeysalso{%                         @cell content={%                             \noexpand\cellcolor[rgb]{\pgfmathresult}%                             \noexpand\definecolor{mapped color}{rgb}{\pgfmathresult}%                             \ifx\textcolorvalue\empty                             \else                             \noexpand\color{\textcolorvalue}%                             \fi                             \the\toks0 %                         }%                     }%                 }%                 \endgroup                 \temp                 \fi             }%         }%     } }  \begin{document}       \vrule\pgfplotstabletypeset[%     color cells={min=365,max=375,textcolor=black},     /pgfplots/colormap={orangewhiteorange}{rgb255=(255,170,0) color=(white) rgb255=(255,170,0)},     /pgf/number format/fixed,     /pgf/number format/precision=0,     col sep=comma,     columns/xxx/.style={reset styles,string type}%     ]{%%%%%%%         xxx, 0, 1, 2, 3, 4, 5, 6         0, 370.8, 371.2, 371.1, 370.9, 371.2, 371.6, 372.0         1, 370.4, 370.3, 370.4, 370.7, 370.8, 371.4, 371.5         2, 370.9, , 370.7, 370.9, 370.8, 371.2, 372.1         3, 371.0, , , 368.1, 371.1, 368.8, 371.3         4, 370.9, , , , 371.1, 371.4, 371.4         5, 371.7, , , , , 371.1, 371.4         6, 372.0, , , , , , 371.2     }\vrule \end{document}   Any help is appreciated!


Consider the sequences $\{x_n\}_{n=1}^\infty$ and $\{y_n\}_{n=1}^\infty$ satisfying the following properties:         $0<y_1<x_1$   $x_{n+1}=(x_n+y_n)/2$ for all $n\ge2$   $y_{n+1}=2x_ny_n/(x_n+y_n)$ for all $n\geq 2$      I would like to prove that $\lim_{n\to\infty}x_n=\lim_{n\to\infty}y_n=\sqrt{x_1y_1}$. Here's my proof. Is it correct?     $x_2$ is the arithmetic mean of $x_1$ and $y_1$, while $y_2$ is their harmonic mean. Since the former mean is always larger, $x_1>x_2>y_2>y_1>0$. By extension:   $$x_1>x_2>x_3>\dots x_n>x_{n+1}>y_{n+1}>y_n>\dots y_3>y_2>y_1>0$$   Thus $\{x_n\}$ and $\{y_n\}$ are monotone and bounded; by the monotone convergence theorem they converge to a finite limit.      Let $\lim_{n\to\infty}x_n=x$ and $\lim_{n\to\infty}y_n=y$. Then $x=(x+y)/2$ as $n$ goes to infinity, so $x=y=L$.   Moreover, $x_1y_1=x_2y_2=x_3y_3=\dots=x_ny_n=x_{n+1}y_{n+1}=L^2$, so $L=\sqrt{x_1y_1}$. $\blacksquare$

We define the Arithmetic-Harmonic mean of $a,b \in  \mathbb{R_+}$ such that  \begin{gather*} a_{n+1} = \frac{1}{2}(a_n + b_n) \\ b_{n+1} = \frac{2a_{n}b_{n}}{a_{n} + b_{n}} \end{gather*}  Let us also assume that $a \neq b$. I am trying to prove that the limit of these sequences exist, they are equal to each other, and as $n \rightarrow \infty$, the limit is equal to $\sqrt{ab}$, the Geometric Mean of a,b.   This is stated by mathworld here:   Since I have proven that AM $\geq$ HM, with equality only holding at a = b, we can see that $a_1 \geq a_{2} \geq ... \geq a_n$. In the same vein we have $b_1 \leq b_{2} \leq ... \leq b_n$.  How can I rigourously show that these are monotonic sequences bounded above and below resepctively and therefore converge to each other?  Secondly, can anyone give me a hint as to how I can show that this sequence converges to the Geometric Mean?


I've tried for a while myself from first principles and applying various rules, but always end up going in circles. I've gotten as far as  $$ y = a^x $$ $$ \frac{dy}{dx} = a^x \left( \lim_{x \rightarrow 0} \frac{a^h-1}{h} \right) $$  but I have no idea how I should go about cancelling the $h$ in the denominator. Any help is appreciated.

I've been trying to think for the past few days how one could differentiate $a^x$ based on the definition that $a^n$ is repeated multiplication, $a^{n/m}=(\sqrt[m]a)^n$, and $a^x$ is the completion of the above function by continuity.  With a bit of algebra, the problem quickly reduces to finding the derivative at $0$:  $$\lim_{h\to0}\frac{a^h-1}{h}\tag{1}$$  And that limit's really got me stumped. Since you'll obviously have to use the definition in some way, I thought I'd replace $h$ with $\frac{1}{n}$ and use the $n$-th root definition:  $$\lim_{n\to\infty}n(\sqrt[n]a-1)\tag{2}$$  Of course, just because $(2)$ exists doesn't automatically imply $(1)$ exists, but it might be a first step. Even $(2)$ has me stumped, though.


I'm currently running Ubuntu 13.10 on a minimac through a refit partition (500gb mac - 1.5 tb linux). Today I took an apple upgrade to OSX Maverick which was fine and when I tried to boot back into Linux, the refit screen opened, offering me apple or ubuntu. I selected ubuntu and got 'No bootable device -- insert boot disk and press any key. Any help will be appreciated.

I have a mac that is running a dual boot with OSX and Ubuntu. I am using rEFIT. I just updated my OSX to the new OSX Mavericks, but when i restarted my computer and tried to enter Ubuntu from rEFIT I just got an error message saying error: unknown filesystem.  How can I solve this? Where is the problem, is it GRUB or rEFIT?


I'm planning to take a phd-level Algebra class this fall semester and so I want to spend some of the summer going through a good first book.  The phd course will assume knowledge of undergrad Algebra.  Is there something like a "baby Rudin" / gold-standard book for Algebra?    Is there also an easier book with both lots of exercises and solutions?    Thanks,

Last semester I picked up an algebra course at my university, which unfortunately was scheduled during my exams of my major (I'm a computer science major). So I had to self study the material, however, the self written syllabus was not self study friendly (good syllabus overall though).  The course was split up into 3 parts, group theory, ring theory and field theory. As a computer science major we only had to study the first 2.  Now that I passed the exam for this course I want to study the field theory part ( which covers Galois theory, etc).  So, now I want to ask whether any of you know any good books on abstract algebra, which lift off at basic ring theory and continue to more advanced ring theory and to finite fields, Galois theory, ...  Please keep in mind that I am not a math major, and that I would like books which are suited for self study (thus a lot of examples and intuition).  Thanks in advance!


Can I say "I am good AT math" or "I am good IN math".Are there rules for these or I can use eithe. And do they differ in meaning if I use AT or IN?

In a document I found the following sentence:     listeners are more accurate at understanding speech spoken in their own accent...   Would it be an error to use "in" instead of "at"?  Actually in this case "at" sounds better than "in", but in general before verb is "at" always used?


Redhat has a log you can look at after yum installs packages on your system. Is there an equivalent log to that in Ubuntu?

I would like to know where I can find the logs for the following package managers:   Synaptic Package Manager Ubuntu Software Center The logs when using the terminal with apt-get


There's a person named Khushwant Singh in a story. He and his grandmother are friends. There's a question asked in my book: What is the 'turning point' in the story? And my answer begins something like this: 'The turning point' in the lesson refers to the turning point in Khushwant Singh's and his grandmother's friendship. Now here's where I get confused. Did I use the apostrophes properly? If I didn't use it properly, how should I use it properly?

Which option is grammatical?        There will be readings from Nikki Giovanni’s and Alice Walker’s writings.   There will be readings from Nikki Giovanni and Alice Walker's writings.      Saying it out loud the latter sounds right, but looking at it the former looks better.


I have a requirement for a custom number system in C# which goes as following:  A - 1 B - 2 ... Z - 26 AA - 27 AB - 28   I've made a function that converts from arbitrary strings to numbers like this:      private const int Min = 'A';     private const int Max = 'Z';     private const int Base = Max - Min + 1;      private static int GetCharValue(char c)     {         if (c < Min || c > Max)             throw new ArgumentOutOfRangeException(nameof(c), c, $"Character needs to be between '{Min}' and '{Max}', was '{c}'.");          return c - Min + 1;     }      public static int GetStringValue(string s)     {         char[] chars = s.ToCharArray();         int[] values = new int[chars.Length];         for (var i = 0; i < chars.Length; i++)         {             values[i] = GetCharValue(chars[i]);         }          int position = 1;         int value = 0;         for (var i = values.Length - 1; i >= 0; i--)         {             value += position * values[i];             position *= Base;         }          return value;     }   I've tested it to be working for up to AAA (not rigorously, just skimming over the output of printing them all). However, I can't for the life of me figure out how to write the reverse function. In other words, I need 1 to return A, 26 to return Z and 27 to return AA. The "problem" is that this number system has no 0, so it doesn't easily convert to any base. For instance, if A was 0, then AA would also be 0, but it's not. So how do I solve this?

How do you convert a numerical number to an Excel column name in C# without using automation getting the value directly from Excel.  Excel 2007 has a possible range of 1 to 16384, which is the number of columns that it supports. The resulting values should be in the form of excel column names, e.g. A, AA, AAA etc.


Without plotting graph prove that $f: \mathbb{R}\to \mathbb{R}$ $$f(x)=\sin x+x$$ is an Onto function  Let $y_0$ be any number in codomain Then we require atleast one $x_0$ in Domain such that $y_0=\sin x_0 +x_0$  Now since $\sin x_0$ is bounded in $\left[-1 \:\: 1\right]$  we have   $$x_0=y_0-\sin x_0$$  hence there is an $x_0$ in Domain. So $f$ is surjective. But i feel something missing in this proof? Any other way to prove?

Prove that the function $f:\mathbb R\to \mathbb R$ defined by $f(x)=x+\sin x$ for $x\in \mathbb R$ is a bijective function.    The codomain of the $f(x)=x+\sin x$ is $\mathbb R$ and the range is also $\mathbb R$. So this function is an onto function. But I am confused in proving this function is one-to-one. I know about its graph and I know that if a function passes the  horizontal line test (i.e horizontal lines should not cut the function at more than one point), then it is a one-to-one function. The graph of this function looks like the graph of $y=x$ with sinusoids going along the $y=x$ line. If I use  a graphing calculator at hand, then I can tell that it is a one-to-one function and $f(x)=\frac{x}{2}+\sin x$ or $\frac{x}{3}+\sin x$ functions are not, but in the examination I need to prove this function is one-to-one theoritically, without graphing calculators. I tried the method which we generally use to prove a function is one-to-one but no success. Let $f(x_1)=f(x_2)$ and we have to prove that $x_1=x_2$ in order fot the function  to be one-to-one. Let $x_1+\sin x_1=x_2+\sin x_2$ But I am stuck here and could not proceed further.


You can post a link to an android market application by useing a link that looks like:     market://search?q=pname:package    While browsing the market, is it possible to find an app's package name? Or is there a convenient way to get or share a link to a market app? Is there any way to post a link to a market app that normal (non-android) browsers can make use of?

When posting app links, I'm always using a link on Cyrket or AppBrain -- becuase I can't get a link to anything in the official Android Market.  But I have seen some links out there for use w/ Android itself ( ''market://'' protocol ):  market://details?id=de.schildbach.oeffi   (as seen @ )  Is it possible to web-link to apps in the Market so that a non-Android user can link to the appropriate Market page in a non-Android web browser?


So I have a pointer SparseMatrix *mat which holds values of the sparsematrix in a triplet format from a file. After I get the values, I would like to be able to just print it out using a print function I created in the SparseMatrix() class. However, I realize that this works if it wasn't a pointer and just 'mat'. I feel like this is something simple but I just cannot wrap my head around it. Any suggestions? Forgive me if this is an extremely noob question. Also, the reason I'm even using a pointer in the first place is because I am trying to visualize a sparsematrix using QT and my professor had given the basic backbone of the code. In that code, a private variable, SparseMatrix *mat was given.

I know references are syntactic sugar, so code is easier to read and write. But what is the difference between a pointer variable and a reference variable?


I don't know what the big { thing is called so can't search and when tried and write in LaTeX and didn't find this expression or structure in word either.

How to write this Piecewise function using LaTeX?  I tried $ \begin{array}{cc}   \{ &      \begin{array}{cc}       0 & x\leq 0 \\       \frac{100-x}{100} & 0\leq x\leq 100 \\       0 & 100\leq x     \end{array} \end{array} $  but it didn't work perfectly, the bracket "{" looks small, see:


Given that  $A$ and $B$  be  $n \times  n$ matrices   over  $\mathbb{C}$. Then choose the correct options      $(1)$ $AB$  and $BA $  always  have the same set  of eigenvalues      $(2)$ If $AB$ and $ BA$ have  same  set   of eigenvalue  then AB = BA      $(3)$ If $A ^{-1}$  exist  then $AB$ and $BA$  are  similar      $(4)$ The rank of $AB$  is always  same  as the  ranks  of $BA$   My attempt:   I thinks all option $1,2,3,4$  will be  correct if   take $A=B= I$  Any hints/solution will be appreciated   Thank you!

Let  $A$ and $B$  be matrices over $\mathbb C$. Then,          $AB$  and $BA$   always have the same set of eigenvalues.      If  $AB$  and  $BA$  have the same set of eigenvalues then $AB=BA$.           If  $A^{-1}$   exists then  $AB$  and $BA$   are similar.     The rank of  $AB$  is always the same as the  rank of   $BA$ .       Suppose $AB=BA$ Let $x$ be the eigen vector of $A$ corresponding to the eigenvalue $a$. $$ABx=BAx=aBx \implies Bx$$ is the eigen vector of $A$. If the eigen space corresponding to the eigen values of $A$ is one. Then, $Bx=\lambda x \implies x$ is the eigen vector of $B$. So $AB$ and $BA$ have same set of eigen values. statement is false. Am I correct? I don't know, How to judge the statement. I don't know, How to judge the statement. Statement is false, I could obtain the counter examples.   Please check my answers. Please help me.


Not referring to militaries or governments, but for other organizations or shops that needs an IT infrastructure (who doesn't nowadays). Similar to  question, but purely in regard to hardware and/or services, such as servers, storage, email services, etc.  I don't imagine it's cut and dry for every org, because every organization is different. Should they consider:   Size of the org and what resources are required Whether or not the org has in house IT support Recurring cost of replacing hardware vs. hardware 'subscription' Of course there are security concerns, such as 'Is this service from <provider> compliant with <security standard> If going with a hosted option, what's the exit strategy if all of a sudden the agreement can't go forward, for whatever reason. Options for backups, with either choice.   There's of course more to consider than just cost. I ask this because you have small 1-2 employee shops that need services such as email or file services, all the way up to huge organizations, but those huge organizations aren't IT shops, their production may be basket-weaving or something, should they invest in a private infrastructure to host their basket-weaving drawings, documents and the like? How is that a value add for them?  Update  Not necessarily cloud, colocation is an option as well.

Currently I have a web app running where I have 9 VPS servers connected to a Load Balancer. As my web app has been getting traffic, I've been purchasing new VPSs to handle the load. Managing so many of them is pretty annoying and I don't really have time to learn Puppet/Chef.   I am wondering, would I get more output if I purchase say 2 high end dedicated servers assuming that my Ubuntu/Apache config would be cloned over to them? Is there any way to estimate the gains/loses in hit/sec that I would get? Right now most of my VPSs are 8GB ram with low CPU priority.   This is my level of volume right now:   Often times I have spikes of up to 2k/sec. My VPS system seems to cap at around ~850/sec.  Would going dedicated by the next logical step?


I am trying to work out how good my particular model is at explaining some observed data.  The problem here is that the observed data takes the form of averaged (mean) values for each of my predictive scores.  When performing a simple correlation, I get a really high R-squared value (and this is repeated for independent data sets), which I am assuming means that there is a consistent relationship between my predictive value and the observed data.  However, if I want to estimate how much of the variance in observed data I explain with my predictive score, how would I do this with averaged observed values?  My underlying concern is that although I have a good correlation in all cases, there may be many underlying factors that also drive my observed data that are simply being 'averaged out' within each category, and as such, my r-squared value is meaningless.  Just as an example, if my underlying observed data was: x<-c(3,4,3,2,1,6,5,7,5,4,9,7,8,10,11) And my predictive score for these values is: y<-c(1,1,1,1,1,2,2,2,2,2,3,3,3,3,3)  I get r-squared of 0.911.  However, if I average my observed data (which is all I can measure in my case), I would get: x1<-c((13/5),(27/5),9) y1<-c(1,2,3) R-squared = 0.997  Thus telling me that my predictive score explains almost all of the variation in the observed data, when a better representation above (x vs y) tells me I am explaining 91% of the variation.  Thanks.

Let's say I perform linear regression on some data that produces the following $R^2$: $\text{RSS} = 1966815.13$ $\text{TSS} = 2145213.91$ $R^2 =  0.083$ Now let's say I bucket (take the average of successive equal size windows) the data and perform the exact same linear regression. This time the $R^2$ is: $\text{RSS} = 1187.56$ $\text{TSS} = 4758.32$ $R^2 =  0.75$ What have I just done here? I clearly haven't improved the explanatory power of the model over the original data, yet I've hacked the $R^2$ by averaging. What's the bias / variance argument of why this occurs? A graphical representation:  Edit: I've reduced the total variance of the data, but the bias remains unaffected. When (if ever) is this a valid statistical approach?


One month ago, I have submitted a paper in a journal under Taylor and Francis. 3/4 days later after the submission,  the status changed to "under review" and till now the status remained unchanged. I am in a hurry and need to get the final decision as soon as possible. What can I do to speed up the process? Should I send an email to the editor? How long it will be in "under review" stage?

I submitted a paper to a journal, and I suspect that it is handled too slowly.   How can I decide whether my suspicion is correct? What handling times should I expect? Given some expected handling times, when should I act? How much leeway should I give? How should I act? Whom should I contact and what should I (roughly) write?   Note that I am interested on how I should approach this situation in general, and do not seek specific numbers for my specific situation. I am therefore looking for general answers that are independent of such factors as the field or individual journal (but mention them if they are relevant factors).  This is a canonical question on this topic as per . Due to its nature, it is rather broad and not exemplary for a regular question on this site. Please feel free to improve this question.


I am all new to python and I just got to know methods I am using python 3.7.0 64 bit and I want to know what is the difference between methods and functions. but please in very very basic explanation because I am also all new to programming.

Can someone provide a simple explanation of methods vs. functions in OOP context?


I am not sure if I did this correctly but downloaded Ubuntu, but not sure if it is the right one. I'm using a Dell Inspiron duo 1090 an old lap top that I believe is nine years old! It has been converted to Windows 10 BUT is super slow!!! I have used Ubuntu before at Amazon in Cape Town and it was great and quick and very user friendly!! Can somebody please, kindly tell me how can I install Ubuntu in this old computer? I bought from e-bay about a month ago. I though am not a PC whiz and haven't a clue what to do?

I would like to see a full how-to guide on how to install Ubuntu.


I own about 100 domain names. Most of them are unused, but I have them all set up to point to the same server so that I can serve a redirect to my main domain name.  Right now, I'm using A records for each domain to point to my server. I'm about to change servers, which means I'll need to change IPs. Using Google Cloud DNS (or any DNS provider), is there a way to use some sort of root CNAME or variable so that I don't have to change the IP 100 times?  I'd love to be able to update a single domain's A record, and then see the rest update automatically, but I don't see a way to make a CNAME record on a non-subdomain, only an A record.

This is a  about DNS server administration.   I have one hundred or so domains. All of these domains need to be configured identically, but it seems like a huge waste of time to have to configure a new zone and/or zonefile for every one of these domains. There has to be a better way to automate this!  I think I'm on to something...if I create a zone called ., or use some other feature in my DNS software to always return a specific IP when an A record is requested, this seems to get me pretty close to my desired end result. My server is responding authoritatively to the requests and it's so much easier to manage!  This was working great until nameserver validation software started checking these domains. I figured out that I can make most of the errors go away by adding NS records, but my software won't let me put more than one SOA record in the same zone file.  How do I work around this multiple SOA record problem?


Honestly I don't know how to come up with a way to explicitly write a surjective homomorphism $\phi: S_4 \to S_3$  What I do know (which is what I did):   Showed that $S_4/H \cong S_3$, where $H$ is a normal subgroup of $S_4$. Since $|S_4/H| = \frac{|S_4|}{|H|} = |S_3| \implies \frac{24}{|H|} = 6 \implies |H| = 4$. Since a normal subgroup can be written as the union of (some) of the conjugacy classes of (in this case) $S_4$, I write them down and found out (after proving that $H$ is indeed a subgroup) that $H = \{e, (12)(34), (13)(24), (14)(23) \}$, which is the Klein-$4$ group (I didn't know about Klein groups before this problem (: ). Then by the theorem of homomorphisms $\exists$ surjective homomorphism $\phi: S_4 \to S_3$, such that $\mathrm{Ker}(\phi) = H$.   And here I'm stuck. By googling I found material ( and ), where showed that the (surjective) homomorphism exists (if I didn't misunderstood what it's written there) by conjugating the elements of $H$ by those of $S_3$. But   On what basis they decided that conjugation is a good idea to show that the homomorphism exists? From what it's written there (if possible) how can one write down and explicit function $\phi$ or it's not necessary?

Let $S_4$ be a symmetric group on $4$ elements, $V_4$ - its subgroup, consisting of $e,(12)(34),(13)(24)$ and $(14)(23)$ (Klein four-group). $V_4$ is normal and $S_4/V_4$ if consisting of $24/4=6$ elements. Hence $S_4/V_4$ is cyclic group $C_6$ or a symmetric group $S_3$ (really, there are only two groups consisting of $6$ elements). It is easy to see, that an order of each element of $S_4$ is $1,2,3$ or $4$. So, $S_4/V_4$ is isomorphic to $S_3$.  My question: how to build the isomorphism explicitly?


I have wifi usb adpter. It has a RTL8188EUS, it is the WN725N from TP-LINK.  I'm running ubuntu server 20.04. I have tried to install a bunch of driver, but they are not able to compile, I think it is too old for the  linux generic headers, at least I read it at a blog or something. If I type in lsusb it shows up. I'm really new to ubuntu. Can anybody send a working driver for this? OS: Ubuntu Server 20.04 Chipset: RTL8188EUS Adapter TP-LINK WN725N Edit: Dear guy who linked the other post, that is the one that is not working for me.

I'm trying to install driver for my newly bought USB Wifi adapter. I tried installing driver provided in the CD that came with the adapter, it gave me this error  error: implicit declaration of function ‘init_timer’; did you mean ‘_init_timer’? [-Werror=implicit-function-declaration]   init_timer(ptimer);   ^~~~~~~~~~   _init_timer   The driver name in the provided cd is      RTL8188EUS_linux_v4.1.4_6773.20130222   so I tried installing all the driver available on internet with name of rtl8188EUS or rtl8188EU but nothing worked. Either they give an error like above or they just don't work. I think it is because my kernel version is      5.0.0-25-generic   and they all work with some old kernel version. Please guide me how do get rtl8188EUS driver working on my Ubuntu 18.04.2 lts.


Very often, I see non-static variable in 'nested' classes (not exactly inner class kind of nested but class composition) being accessed via the dot notation.   Eg.  int a = getClassA().classB.classC.x; where    getClassA() return an object of type Class A and x is the variable we are interested to access.  classB is a variable in ClassA.  classC is a variable in ClassB.  x is a variable in ClassC.  However, when I tried to recreate a similar test scenario, I get NullPointerException error.  Code  public class Main()  { public static void main(String[] args) {  int a = getClassA().classB.classC.x; } }  public class ClassA  { ClassB classB; }   public class ClassB  { ClassC classC; }   public class ClassC  { int x = 1; }  //Class Main, A, B and C are in separate files.   Add-on  Read somewhere that in c# there is auto implemented property. For the example above, Class A will be   public Class A { private ClassB _classB;  public ClassB classB { get {     if (_classB == null) _classB = new ClassB();     return _classB; } set {_classB = value; } } }   So, ClassB is instantiated as it is accessed via the dot notation. Is there something similar in Java?  Appreciate any help on this.   Thank you.

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 a view with 2 relations with the store for 2 different entities. I want to filter the view with the store id for the 2 relationships. I created 2 context filters in the views. You must use the first context filter OR the second. How to do this ? If 2 filters are added, there are no results

I have a Content Type named "Match" which has a local and visitor. Both are node references to a Content Type named "Team".  In Views I need to ask for matches of a specific team, no matter if that team is the local or the visitor. In contextual filters I can set a value for "local" and for the "visitor" each one in particular. So I guess I need an OR condition in this case.  Does anyone know how to solve that problem?  Edit: I found  module already but that's the problem, my website is too big and currently in production so we don't want to have problems because of bugs or something.


So I'm new and I'm using Cycles rendering. The problem is that when I render I get white particles all over the image. I learned that MIS helps out with that, but I don't know how to apply it as I am using Emission on material.(I am not using any lamps and I know that they have this option) currently using 2.79 as I find it easier to navigate. Is it possible to fix it with nodes? or at least someway else.

I know that this question is a bit old or maybe overdone, but I'm running the latest edition of Blender and when I use the Cycles engine I get really fuzzy results and I can't find a simple, non-compromising solution to the quality.  I don't know exactly what I'm doing wrong here, but I'm sure others share my frustration.  Leaving everything in default settings, I started a new project and switched to the Cycles render.  I duplicated the cube and set colors for two Diffuse BSDF shaders, then went ahead and made walls and a floor all sharing the same diffuse shader.  I made two windows to emit blue light.  The screenshot has gaps between the walls because of the setup:  I'm aware that it's considered very incomplete and many have come to terms with some amount of noise, but is this normal?  Furthermore, with default settings or not, I can't change the amount of noise produced.  Supposedly, using "progressively refine" in the rendering tab should make it refine itself indefinitely, however Cycles only counts to 10 refines and then stops, creating a render which is a pixel-perfect match of the ordinary rendering method when it's completed.  I understand that there are tricks that can be used to reduce noise, but at the cost of extra processing time and usually small quality conflicts, like blurring.  My question essentially boils down to is this Cycles' current limit?


I have an HTML form that I am trying to upload an image through.  <form id="imageform" method="post" enctype="multipart/form-data" action='upload.php'>     Upload image <input type="file" name="file" id="file" /> </form>  <div id='preview'> </div>   I want to use JavaScript to upload run upload.php, so the page does not have to refresh. I then want to display the output in #preview.  $(document).ready(function() {      $('#file').live('change', function() {         $("#preview").html('');         $("#preview").html('Uploading...');         $.post("upload.php",$("#imageform").serialize(), function(data){             $("#preview").html(data);         });     }); });    However, I get many errors like these within the div. I know that the data isn't being sent through, but how can I fix it?  Notice: Undefined index: file in /path/upload.php on line 14   I've searched through things on Google, but I have been receiving the same issue.

I would like to upload a file asynchronously with jQuery.     $(document).ready(function () {     $("#uploadbutton").click(function () {         var filename = $("#file").val();          $.ajax({             type: "POST",             url: "addFile.do",             enctype: 'multipart/form-data',             data: {                 file: filename             },             success: function () {                 alert("Data Uploaded: ");             }         });     }); });  File <input type="file" id="file" name="file" size="10"/> <input id="uploadbutton" type="button" value="Upload"/>     Instead of the file being uploaded, I am only getting the filename. What can I do to fix this problem?


$\lim \limits_{x \to 0}x\sin\left(\frac{1}{x}\right)$   I need to find and prove this limit.  I can easily plug it into wolfram alpha, but I want to make sure I learn something.  It's been 3 years since my Calculus 2 course and I just cannot remember how to tackle this one.  Hints?

Evaluate the limit: $$ \lim_{x \to 0 } = x \cdot \sin\left(\frac{1}{x}\right) $$  So far I did:   $$ \lim_{x \to 0 } = x\frac{\sin\left(\frac{1}{x}\right)}{\frac{1}{x}\cdot x} $$  $$ \lim_{x \to 0 } = 1 \cdot \frac{x}{x} $$  $$ \lim_{x \to 0 } = 1 $$  Now of course I've looked around and I know I'm wrong, but I couldn't understand why. Can someone please show me how to evaluate this limit correctly? And tell me what I was doing was wrong.


How can I show that $\mathbb{Z}_2$$\times$ $\mathbb{Z}_2$ and  $\mathbb{Z}_4$ are not isomorphic?   I don't even know how to start  Thanks for any help

In trying to understand why there are two sets of groups of order 4.  I know that there exists the Vierergruppe of $\mathbb{Z}_2 \times \mathbb{Z}_2$ and the group $\mathbb{Z}_4$ but I do not understand why they are not isomorphic


I am able to display textarea  using jquery but unable access id of that textarea so that i can add on mouse events to textarea.  I tried this example on stackoverflow, it's not working for me     $('#foo').on('click', function() {       $(this).replaceWith('<textarea id="copy">' + $(this).text() + '</textarea>');        $('#copy').click(function() {           $(this).select();       });   });   Below is my code.   First text will be displayed in "disp" once user want to edit,if he clicks on disp field it should turn into textarea. Here i am able to change disp to textarea, unable to add mouse events.    $( ".disp" ).click(function() {     $( this ).replaceWith( '<textarea >' + $( this ).text() + '</textarea>'  ); })   how to add mouse events on textarea which is displayed by jquery?

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


I like to learn linux based operating system. If not, what are the steps to make it work in this device? I am really interested in getting Ubuntu touch in my phone. I rooted my phone and i had tried custom roms also.

With the announcement of the Ubuntu Phone OS I'd like to know what phone (and tablet) models are supported at this time.  Note from foss & Oli: We are making this the master question for all future "Will this work on <insert random tablet/phone/device here>?!" questions


Are there any best practices for configuring a Maintenance Plan in SQL Server 2008?  Currently, I'm removing database backups and transaction logs greater than 40 hours old, then backing them up.  Problem I've seen is that the transaction log is still very large.  Should I be including a Shrink Database Plan task?

This one seems to be a common question in most forums and all over the web, it is asked here in many formats that typically sound like this:  In SQL Server -  What are some reasons the transaction log grows so large? Why is my log file so big? What are some ways to prevent this problem from occurring? What do I do when I get myself on track with the underlying cause and want to put my transaction log file to a healthy size?


I want to limit 1 connect per 5 seconds using IPTABLES for people, which are connecting to port "12871/12881". I was trying to find rule for it, but ineffectively. It must be like a "queue" of connects - for example 1 connect per 5 seconds.  I had here discussion:   but Im not able to reply on this account, previous was unregistered and logged me out.


I would like to know if it's possible to create an alias (on my .zsh_aliases) to launch a command from the graphical session to a tty (does not matter 1 or 6 ...) ? I tried with for example cmatrix:     alias matrix='sudo chvt 1 && cmatrix -B'  and it will open the tty 1 but launch cmatrix on the current shell (on the Xsession). (I have a zsh shell on Debian 10)

Suppose you have a terminal emulator (T1) open with a PID of 6350.  From another terminal, type this command (C1):  echo "ls\n" > /proc/6350/fd/0   This writes ls and the new line in T1 but does not execute it. Why?  I also tried using cat|bash with echo "ls\n" > /proc/catid/fd/0 but it is still not executed.  How can I echo the command into another terminal and have the command executed?  possible answer :  $ mkfifo toto; $ bash < toto; $ echo "ls" > toto;   In this case you cannot write anymore directly in the terminal (everything is displayed the same way the command (C1) displayed thing in this terminal.


Normal AES-GCM generates an authentication tag at the end of encryption. I want to decrypt it while it is still being encrypted. This would be useful to send, encrypt, receive and decrypt a large file (for example) in one go.  This would also be useful for other things like for video streams or encrypted calls. How could I do that? Switching to CBC seems like a bad idea.

I am now studying AES encryption for real-time video streaming. It seems that Netflix uses the AES-GCM (or CBC + MAC) mode for real-time video encryption and authentication. With MAC authentication, the client can only get the MAC message after the whole video is encrypted and authenticated. After that, the client can verify and play the video. However, if the client wants to play the video immediately (without receiving and decrypting the whole video), how can the client verify the MAC message?  I guess the video stream may be divided into many small slices. The server will encrypt and authenticate those slices one by one. At the receiving side, the client will verify, decrypt and play slice_1, then slice_2 ,then slice_3 and so on.  I am not sure whether my guess is right. Could someone please give me some advice? How does the real video provider's server do this kind of secure video stream transmission? If my guess is right, what is the typical size of video slices, or it is dynamic?


I installed a python package libxmlsec1 using sudo spt-get install libxmlsec1. I got the installation to be successful but when I try to import it in the python command line iam getting an import error. Please help me in sortin out the error.

Hi I am unable to download a python module dm.smlsec.binding 1.0b3. The following error is what I get. I have attached my log file please help me sorting out  ------------------------------------------------------------ /usr/local/bin/pip run on Thu Jul 18 12:23:36 2013 Downloading/unpacking dm.xmlsec.binding Running setup.py egg_info for package dm.xmlsec.binding Traceback (most recent call last):   File "<string>", line 16, in <module>   File "/tmp/pip-build-student/dm.xmlsec.binding/setup.py", line 199, in <module>     **setupArgs   File "/usr/lib/python2.7/distutils/core.py", line 112, in setup     _setup_distribution = dist = klass(attrs)   File "/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg/setuptools/dist.py", line 260, in __init__   File "/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg/setuptools/dist.py", line 284, in fetch_build_eggs   File "/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg/pkg_resources.py", line 569, in resolve     dist = best.get(req.key) pkg_resources.VersionConflict: (lxml 2.3.2 (/usr/lib/python2.7/dist-packages), Requirement.parse('lxml>=3.0')) Complete output from command python setup.py egg_info: Traceback (most recent call last):   File "<string>", line 16, in <module>   File "/tmp/pip-build-student/dm.xmlsec.binding/setup.py", line 199, in <module>     **setupArgs   File "/usr/lib/python2.7/distutils/core.py", line 112, in setup     _setup_distribution = dist = klass(attrs)   File "/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg/setuptools/dist.py", line 260, in __init__   File "/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg/setuptools/dist.py", line 284, in fetch_build_eggs   File "/usr/local/lib/python2.7/dist-packages/setuptools-0.6c11-py2.7.egg/pkg_resources.py", line 569, in resolve     dist = best.get(req.key) pkg_resources.VersionConflict: (lxml 2.3.2 (/usr/lib/python2.7/dist-packages), Requirement.parse('lxml>=3.0')) ----------------------------------------  Command python setup.py egg_info failed with error code 1 in /tmp/pip-build-student/dm.xmlsec.binding  Exception information: Traceback (most recent call last):   File "/usr/local/lib/python2.7/dist-packages/pip-1.3.1-py2.7.egg/pip/basecommand.py", line 139, in main     status = self.run(options, args)   File "/usr/local/lib/python2.7/dist-packages/pip-1.3.1-py2.7.egg/pip/commands/install.py", line 266, in run     requirement_set.prepare_files(finder, force_root_egg_info=self.bundle, bundle=self.bundle)   File "/usr/local/lib/python2.7/dist-packages/pip-1.3.1-py2.7.egg/pip/req.py", line 1057, in prepare_files     req_to_install.run_egg_info()   File "/usr/local/lib/python2.7/dist-packages/pip-1.3.1-py2.7.egg/pip/req.py", line 236, in run_egg_info     command_desc='python setup.py egg_info')   File "/usr/local/lib/python2.7/dist-packages/pip-1.3.1-py2.7.egg/pip/util.py", line 662, in call_subprocess     % (command_desc, proc.returncode, cwd)) InstallationError: Command python setup.py egg_info failed with error code 1 in /tmp/pip-build-student/dm.xmlsec.binding


I recently reformatted my hard drive, so I downloaded QGIS so I could install it again. But now that I have, I seem to be missing all of my geoprocessing tools. Normally there were quite a few available from the drop-down Vector menu. Now there are only a handful. Also, I can't find the processing toolbox that I used to use, not sure what that was called but it seems to be missing now. It was where you could access all of the geoprocessing commands including GRASS.

I'm missing all the usual processing tools in the Vector menu in QGIS 2.16 (eg vector overlay, analysis, etc). They do appear in the processing toolbox but there's no sign of them in the Vector menu. Has anyone come across this issue?


I recently got in a road accident and my laptop fell (HP Pavilion p045TX, Win 10 and Ubuntu dual boot). I booted it up and it started showing the automatic repair screen. I booted it in Ubuntu and It started fine. I restarted it again and I got the "Hard Disk not detected error". After that it never detected the hard disk and only made clicking sounds.   Is there any hope of repairing it or recovering the data? Is there something wrong with the head? I guess if the platters were broken, It would have never booted in the first place. Any help would be appreciated.

Upon bootup I have a drive that will spin up click and few times then spin down.  I have a spare drive (same model number) I attempted to transfer the heads from with no luck, HOWEVER, the heads from the bad drive work fine in the spare drive.  Swapping the PCB has no effect either.  So although it seems to spin up fine, could the problem be with the platter motor?


Apologies if this has been posted before, but none of the cases seem to match mine exactly and I don't want to mess anything up. After removing my bootcamp partition I am missing about 250Gb from my disk that was previously allocated to the bootcamp partition. I'm using a 2017 iMac with a 1TB Fusion drive. Can anyone offer any help?

So I removed bootcamp and now there is a partition called "free space" that I can't remove.  Here is my output from diskutil list:    Here is the screenshot from disk utility showing the partitions:    And here is the error I get when I try to remove "free space":    Heres the output when I run   sudo diskutil apfs resizeContainer disk0s2 0


I have an Windows 7  laptop and I am using it almost everyday. Then last night, I am using it as usual, then suddenly all programs stop responding, only the mouse cursor is moving. Then after sometime, it turned off. I opened it then I noticed that the splash screen "Acer" shows up longer than before, then this message appear:     Copyright (C) 2000-2010 Broadcom Corporation      Copyright (C) 1997-2000 Intel Corporation      All rights reserved.      PXE-E61: Media test failure, check cable.      PXE-M0F: Exiting Broadcom PXE ROM   Then a second message appears:     Operating system not found   I checked the BIOS. The hard drive model and serial number is missing. I also saw HDD 0: in the boot order second to the CD Drive. I suspect that cable of the hard drive is faulty. After sometime, I was able to boot the OS two times last night and able to backup some files. But later on, same problems occur: programs not responding, powers down, same error messages.  Do I have the right speculations? Any help what to do?

My computer no longer boots Windows or the installed operating system. Instead, I may get this error:  PXE-E61: Media test failure, check cable -or- Check cable connection!  PXE-M0F: Exiting PXE ROM.   and/or one of the following messages or similar:  Operating System not found  No boot device available- No bootable devices--strike F1 to retry boot, F2 for setup utility  No bootable device -- insert boot disk and press any key  No Boot Device Found. Press any key to reboot the machine  Default Boot Device Missing or Boot Failed  Reboot and Select proper Boot device or Insert Boot Media in selected Boot device   What does this mean and what can I do?     This question comes up often and the answers are usually the same. This post is meant to provide a definitive, canonical answer for this problem. Feel free to edit the answer to add additional details.


Is it possible to know whether any and all statements are true, false, or undecidable under standard mathematical axioms, e.g. ZF?

This is a variant of  and  (but is not asked or answered in either of those threads).  Call a formula $\phi$ provably undecidable if $ZFC$ proves that ($ZFC$ is consistent) $\Rightarrow$ ($\phi$ is independent of ZFC). Now, (assuming that $ZFC$ is consistent) are there statements which are undecidable but not provably so ?  Here is another way to put it. Call a statement $\phi$ weakly decidable if ZFC can either prove that $\phi$ is true or prove that $\phi$ is false, or at least prove the implication ($ZFC$ is consistent) $\Rightarrow$ ($\phi$ is independent of ZFC).  Thus, the continuum hypothesis is weakly decidable in ZFC, and the axiom of choice is weakly decidable in ZF. On the other hand, it is not known today if the existence of an inacessible cardinal is weakly decidable.  The original question can then be rephrased as, are some statements not even weakly decidable ?


I have a new web-admin and he mistakenly ran chmod -r 755 /etc to try and disallow our shell users from reading any other files. As a result, SSH on our server does not work. How can we fix this?

See Also:          I changed file permissions recursively on the root directory / by executing sudo chmod -R / 777, and after that my system won't boot (I'm getting a lot of "permission denied" errors).  Please help.


We have two players, lets call them A and B, a fair die is rolled and if either player gets a 5 or a 6 they win, but if they get a 2,3 or 4 the game continues (until someone gets a 5 or a 6). If two 1's come up in a row the game ends in a draw, if A roll's first find the probability that A wins ?  I have considered the case where there are no draws ie getting a 1,2,3 or a 4 continues the game and this is simply an infinite geometric series. s.t   $P(A)=\frac{2}{6} + (\frac{4}{6})^2\times \frac{2}{6} +(\frac{4}{6})^4\times \frac{2}{6} +... $  but I am not sure how to do this when we consider draws?

Suppose there is a fair six faced dice, and you roll it once at each round. The rule is as follows: 1). If you roll 1 or 2 at an odd-number round, you win the game and the game ends immediately. 2). If you roll 1 or 2 at an even-number round, you lose the game and it ends immediately. 3). If you roll 3 at any round, then it is a draw and the game ends immediately. If two consecutive $3$'s appear then the game ends immediately in a draw. 4). Otherwise the game goes on.   Now, what is the probability that you will win the game?  I attempted to compute the probability of winning at the 1,3,5,...-th round separately and sum them up. However, due to rule 3) it is ever more complicated to compute this for large round numbers.  Another attempt was to calculate the probability of stopping at each round and to get a closed form expression for this sequence, but this is also hard, because it depends backwards on the previous rounds in an endless manner.  Simply put, if we only consider 1) and 2), or only consider 3), the problem isn't hard, but a combination of the three really messes things up.  Can anyone help? Thanks in advance.  EDIT: I'm very sorry for the mistake when I transcribed rule 3), I have corrected it.


I recently came across the following argument regarding the uniqueness of the zeros of a complex polynomial.   Please note that the proof that a complex polynomial of degree $m$ has $m$ zeros has been established at this point. The following is also not the complete proof of the uniqueness of the roots. I just want to focus on a particular passage from the proof that I need help clarifying.  Consider the following equation of two factorizations of the same complex polynomial of degree $m$, where $z, \lambda_i, \tau_i\in\mathbb{C}$, for $i=1\dots m$:  $$\left(z - \lambda_1\right)\left(z - \lambda_2\right)\dots\left(z - \lambda_m\right) = \left(z - \tau_1\right)\left(z - \tau_2\right)\dots\left(z - \tau_m\right)$$  Therefore, all $\lambda_i$ and $\tau_i$ are the zeros of the polynomial. Moreover, substituting $z=\lambda_i$, the resulting equation implies that $\lambda_i = \tau_j$ for some $j \in \left\{1\dots m\right\}$. To make it simple, let's relabel $\tau_j$ so that $\lambda_i = \tau_i$.  Now, consider $i = 1$. Dividing both sides by $z - \lambda_1$, we get  $$\left(z - \lambda_2\right)\dots\left(z - \lambda_m\right) = \left(z - \tau_2\right)\dots\left(z - \tau_m\right)$$  for all $z\in\mathbb{C}$ except possibly $z = \lambda_1$.   So far, with the exception of the word "possibly", it has been straight-forward and obvious to me. However, what comes next in the argument puzzles me:  "Actually, the equation above [after dividing by $z - \lambda_1$] holds for all $z\in\mathbb{C}$ because, otherwise, by subtracting the right side from the left side, we would get a non-zero polynomial that has infinitely many zeros."  That passage is a part of the proof of theorem 4.14 in "Linear Algebra Done Right", third edition (S. Axler).  Why would the alternative case imply a non-zero polynomial with infinitely many roots? Could someone please kindly show me?  Thank you.

I am reading "Linear Algebra Done Right". Right now I am stuck with the uniqueness part of Corollary 4.8, Existence and Uniqueness polynomial factorisation in the form of $p(z) = c(z-\lambda_1)(z-\lambda_2)...(z-\lambda_m)$.  It is stated that if there are two factorisations of $p$, $(z-\lambda_1)(z-\lambda_2)...(z-\lambda_m) =(z-\tau_1)(z-\tau_2)...(z-\tau_m)$. We can divide both sides by $(z-\lambda_1)$ as one of the $\tau$ must equal $\lambda_1$.  Here comes the confusing part for me: After division, we get $(z-\lambda_2)...(z-\lambda_m) = (z-\tau_2)...(z-\tau_m)$ for all $z \in C$ except for possibly $z=\lambda_1$. Actually the equation above must hold for all $z \in C$ because otherwise by subtracting the right side from the left side we would get a nonzero polynomial that has infinitely many roots.  I understand a finite polynomial can't have infinitely many roots, but need elaboration on bolded part, like why it suddenly(?) holds for $z=\lambda_1$, and how comes the theoretical nonzero polynomial has infinitely many roots.


I have to show that  $$\int_{0}^{\infty}\frac{x^2}{1+x^5}dx = \frac{\frac{\pi}{5}}{\sin(\frac{2\pi}{5})}$$  I know how to solve almost every polynomial integral. However, this one is not even and I can not see how to prove this. I try different kinds of parametrization. I tried the semicircle from $[0,\frac{pi}{2}]$, from $[0,\frac{\pi}{4}]$ and so on. I still can not solve this integral. I know the residue theorem and also I know that I have to consider the roots of unity of the equation and the solutions are:  $$z_k = e^{i\frac{n\pi}{5}}, n = 1,3,5,7,9$$ for $k = 1,2,3,4,5$  If I use the following parametrization for $R > 1$  $$\gamma_1(t) = t, t \in [0,R]$$ $$\gamma_2(t) = Re^{it}, t \in [0,\frac{2\pi}{5}]$$ $$\gamma_3(t) = -te^{i\frac{2\pi}{5}}, t \in [0,R]$$  Then using L'hopital to simplify the calculation of the residues we can note that the only residue in the first quadrant is $e^{i\frac{\pi}{5}}$.  Then $$\int_{\gamma}f(z) =  2\pi i \mbox{ Res}(f,e^{i\frac{\pi}{5}}) = \frac{2\pi i}{5e^{\frac{2\pi i}{5}}}$$  Also,  $$\int_{\gamma}f(z) = \int_{0}^{R}f(t)dt + \int_{0}^{\frac{2\pi}{5}}f(Re^{it})iRe^{it}dt - \int_{0}^{R}f(te^{i\frac{2\pi}{5}})e^{i\frac{2\pi}{5}}dt$$  As $R \to \infty$,  $$ (1 - e^{\frac{6\pi i}{5}})\int_{0}^{\infty}f(t)dt = \frac{2\pi i}{5e^{\frac{2\pi i}{5}}} $$  Therefore $$ \int_{0}^{\infty}f(t)dt = \frac{2\pi i}{(1 - e^{\frac{6\pi i}{5}})5e^{\frac{2\pi i}{5}}} $$  Still I can not get the correct answer. Why ?

I've been looking at  $$\int\limits_0^\infty  {\frac{{{x^n}}}{{1 + {x^m}}}dx }$$  It seems that it always evaluates in terms of $\sin X$ and $\pi$, where $X$ is to be determined. For example:  $$\displaystyle \int\limits_0^\infty  {\frac{{{x^1}}}{{1 + {x^3}}}dx = } \frac{\pi }{3}\frac{1}{{\sin \frac{\pi }{3}}} = \frac{{2\pi }}{{3\sqrt 3 }}$$  $$\int\limits_0^\infty  {\frac{{{x^1}}}{{1 + {x^4}}}dx = } \frac{\pi }{4}$$  $$\int\limits_0^\infty  {\frac{{{x^2}}}{{1 + {x^5}}}dx = } \frac{\pi }{5}\frac{1}{{\sin \frac{{2\pi }}{5}}}$$  So I guess there must be a closed form - the use of $\Gamma(x)\Gamma(1-x)$ first comess to my mind because of the $\dfrac{{\pi x}}{{\sin \pi x}}$ appearing. Note that the arguments are always the ratio of the exponents, like $\dfrac{1}{4}$, $\dfrac{1}{3}$ and $\dfrac{2}{5}$. Is there any way of finding it? I'll work on it and update with any ideas.    UPDATE:  The integral reduces to finding   $$\int\limits_{ - \infty }^\infty  {\frac{{{e^{a t}}}}{{{e^t} + 1}}dt} $$  With $a =\dfrac{n+1}{m}$ which converges only if   $$0 < a < 1$$  Using series I find the solution is     $$\sum\limits_{k =  - \infty }^\infty  {\frac{{{{\left( { - 1} \right)}^k}}}{{a + k}}} $$


Let $X$ be an integer-valued $rv$ with $\mathrm{pgf}$ $P(s)$ (probability generating functions) and suppose that $\mathrm{mgf}$ $M(s)$ (moment generating functions) exist for $s∈(-s_0,s_0),s_0>0$. How can we proof that $M(s)$ and $P(s)$ are related??

I am confused between the two terms " probability generating function" and "moment generating function." How do those terms differ?