Actually , I am not believing that $\frac {1}{∞} = \frac{0}{1}$ because simply $0 ≠ 1$ (we get this if we multiple numerator by denominator) , In the other hand it is very very very small , So I am confused

Is infinity a number? Why or why not?  Some commentary: I've found that this is an incredibly simple question to ask — where I grew up, it was a popular argument starter in elementary school — but a difficult one to answer in an intelligent manner. I'm hoping to see a combination of strong citations and solid reasoning in the answers.


Generalized Euclid's Lemma:   Let $a_1,a_2,a_3,...,a_n \in \mathbb{Z}$.  If $p$ is a prime number such that $p | a_1 \cdot a_2 \cdot a_3 \cdot ... \cdot a_n$,  then $\exists i \in \{1,2,3,...,n\}$ such that $p|a_i$.  According to my book, it says the proof can be done by using induction.  How would I go about writing the proof?

How to prove a generalized Euclid lemma par induction after proving Euclid lemma? I want to prove the generalized lemma, to prove by rearranging the product of number and use Euclid lemma as a model. A proof will be nicer if it can use induction principle.


Every time i reboot my laptop i need to open terminal and type sudo chmod 777 /dev/ttyS0to use the serial port.  For configuring Cisco routers I want /dev/ttyS0 to be open when i boot my laptop.  Searched the internet but did not find the answer I am looking for.

My system is Ubuntu 13.04 and it works fine, but I have installed VirtuaBox to run Windows XP, which is essential for me to run an application that dialogues with an alarm setup by a USB-to-Serial adapter.  VirtualBox uses ttyS0 as a Serial port and the communication can start efficiently only if command sudo chmod 666 /dev/ttyS0 is given to Terminal.  Every time I boot Ubuntu, ttyS0 permissions return to the default values and I have to run chmod every time I boot-up.  My question is: how can I change /dev/ttyS0 file permission permanently? If this is not a good practice, are there other manners to solve the issue?


It'd be great if someone checked the proof I did for the following problem:  $f:X\longrightarrow Y$,   $f(\overline{A})\subseteq \overline{f(A)},\forall A\subseteq X \Leftrightarrow f$ continuous  proof:  Suppose $f(\overline{A})\subseteq \overline{f(A)}$ for any $A\subseteq X$ .  Let $C\subseteq Y$ be closed and define $A=f^{-1}(C)$.  $f(\overline{A})\subseteq \overline{f(A)}\subseteq\overline{C}=C$, therefore $\overline{A}\subseteq f^{-1}(C)=A$,  so $A$ is closed.  *Conversely, suppose $f$ is continuous.    Let $p\in\overline{A}$ and let $V$ be an open neighborhood of $f(p)$. Since $f$ is continuous,  $f^{-1}(V)$ is open. On the other hand $p\in f^{-1}(V)$, but since $p\in\overline{A}$ we have that $f^{-1}(V)$ contains points of  $A$. Therefore $V$ contains points of $f(A)$. Since $V$ is an arbitrary neighborhood of $f(p)$, we have $f(p)\in \overline{f(A)}$. So finally, $f(\overline{A})\subseteq\overline{f(A)}$.  Thank you very much!

As a part of self study, I am trying to prove the following statement:  Suppose $X$ and $Y$ are topological spaces and $f: X \rightarrow Y$ is a map. Then $f$ is continuous if and only if $f(\overline{A})\subseteq \overline{f(A)}$, where $\overline{A}$ denotes the closure of an arbitrary set $A$.   Assuming $f$ is continuous, the result is almost immediate. Perhaps I am missing something obvious, but I have not been able to make progress on the other direction. Could anyone give me a hint which might illuminate the problem for me?


This is motivated by a question I saw elsewhere that asks whether there is a real-valued function on an interval that contains no monotone subintervals.   Edit: Note that I am asking for a function whose derivative exists but is not continuous anywhere.

Could someone give an example of a ‘very’ discontinuous derivative? I myself can only come up with examples where the derivative is discontinuous at only one point. I am assuming the function is real-valued and defined on a bounded interval.


I know by intuition that $\omega^{2}\cong\{k-\frac{1}{n}\mid k>0,n<\omega\}$ How can I find a set which is isomorphic to $\omega^3$? I would love to see an example If possible, I would like to see an example for  $\omega^n$ or $\omega^\omega$ aswell.

I need to show that for any countable ordinal $\alpha$ there is a set A $\subseteq \mathbb{Q}$ such that (A, <) is isomorphic to ($\alpha, \in$).  To do it I am supposed to show the following stronger statement by induction on ordinals $\alpha$ < $\omega_{1}$:  Let P($\alpha$) be the statement "For every interval (a, b) with rational endpoints, there is an A $\subseteq$ (a,b) such that (A, <) is isomorphic to ($\alpha, \in$)."  I think that the purpose of breaking $\mathbb{Q}$ into intervals (a,b) is to make $\mathbb{Q}$ a countable set, but I don't see the significance of doing this or how it would make the proof easier.  I feel like I need to define a well-ordered set in (a,b) but I don't know how to do this since if a and b are both negative then there is no least element, so no well-ordering.  I believe that I am supposed to be using transfinite induction? But I don't know how P($\alpha$) implies P(S($\alpha$)) for S($\alpha$) successor of $\alpha$.  Any help would be greatly appreciated... thanks in advance.


If "A xor B _ C" I think "is" would be correct. Since they are otherwise technically uncountable, I would say that "A or B is C". As for the last one, I think I would say "A or B and C are D", but I'm not sure about "A and B or C _ D". By the way, I think English should have brackets or something to isolate otherwise interchangeable groups like you do in mathematics.

I am confused on how to formulate sentences with (n)either...(n)or and the form of verb.  Which sentence is gramatically correct?  "Either my uncle or aunt are visiting me today" "Either my uncle or aunt is visiting me today"  "Neither chocolates nor cake are sufficient for the birthday party" "Neither chocolates nor cake is sufficient for the birthday party"  "Either the dog or the cats are going to the pound" "Either the dog or the cats is going to the pound"


I've been trying to solve the determinant of the Vandermonde-matrix by using Laplace's formula on it (without transforming the matrix first).  It worked out quite well, I could almost instantly factor out the result that I was supposed to get, however not without the weird factor $$ \sum_{k=0}^{n} \prod_{j=0\\j\neq k}^{n} \frac{t_k}{t_k-t_j} $$  For the formula to hold, the factor has to be equal to $1$, and I've tried it for small $n$, however I'm not seeing why exactly this identity has to hold.  Therefore: Why does the identity $$ \sum_{k=0}^{n} \prod_{j=0\\j\neq k}^{n} \frac{t_k}{t_k-t_j} = 1 $$ hold for abitrary $t_i\in\mathbb C$?

If $\lambda_1,\dots,\lambda_n$ are distinct positive real numbers, then  $$\sum_{i=1}^n \prod_{j\neq i} {\lambda_j\over \lambda_j-\lambda_i}=1.$$ This identity follows from a probability calculation that you can find at the  top of page 311 in the 10th edition of Introduction to Probability Models by Sheldon Ross.   Is there a slick or obvious explanation for this identity?   This  question is sort of similar to ; clearly algebra is not my strong suit!


I know back propagation takes derivatives (changing one quantity wrt other). But how this is applied when there is maxpooling layer in between two Conv2D layers? How it gains its original shape when there is padding added?

I have a small sub-question to .   I understand that when back-propagating through a max pooling layer the gradient is routed back in a way that the neuron in the previous layer which was selected as max gets all the gradient. What I'm not a 100% sure of is how the gradient in the next layer gets routed back to the pooling layer.  So the first question is if I have a pooling layer connected to a fully connected layer - like the image below.    When computing the gradient for the cyan "neuron" of the pooling layer do I sum all the gradients from the FC layer neurons? If this is correct then every "neuron" of the pooling layer has the same gradient?  For example if the first neuron of FC layer has a gradient of 2, second has a gradient of 3, and third a gradient of 6. What are the gradients of the blue and purple "neurons" in the pooling layer and why?  And the second question is when the pooling layer is connected to another convolution layer. How do I compute the gradient then? See the example below.    For the topmost rightmost "neuron" of the pooling layer (the outlined green one) I just take the gradient of the purple neuron in the next conv layer and route it back, right?  How about the filled green one? I need to multiply together the first column of neurons in the next layer because of the chain rule? Or do I need to add them?  Please do not post a bunch of equations and tell me that my answer is right in there because I've been trying to wrap my head around equations and I still don't understand it perfectly that's why I'm asking this question in a simple way.


My thesis currently has a few PSTricks and TikZ pictures. It takes a while to compile over  says he has some scripts to automate externalising TikZ pictures.  I'm looking ideally for something that will automatically name sequentially all of my figures, generate the graphics for them and automagically include them. I don't mind if I have to delete them by hand to recompile them if I change the code.  For PSTricks and TikZ please =) cause currently LaTeX is spanned for each PSTricks picture to generate a PDF graphic, and TikZ compilations starts to take up time.  P.S. half way through hte thesis I discovered TikZ but don't have time to redo PSTricks graphics.

Is there a script to automate externalizing TikZ graphics?  (As suggested by Scott )


I've found a fair number of old questions that obviously now belong on Programmers. However, simply voting to close doesn't seem to be doing the trick. Because they are old, no one is looking, and the vote just expires.  Is there a better way to handle these?

Stack Overflow users have been using the "off topic - belongs on SoftwareEngineering.SE" close reason as an alternative to all the other close reasons. It'd be helpful if people actually read the FAQ and the six  before voting to migrate questions like:   , no redeeming value to favorite lists that become argumentative , "help my exact situation" questions are too localized , fails 5 out of the 6 guidelines , fails 4 out of 6 , too localized and too vague , too broad   Absent a reversal of the Stack Overflow community from viewing SoftwareEngineering.SE as the Stack Overflow cesspool, can the "off topic - belongs on SoftwareEngineering.SE" close reason be removed in favor of manual migration by moderators who can actually spend the 10 seconds to determine if the question should be closed outright first?    To say that SoftwareEngineering.SE is such a nebulous place and nobody knows what its scope is as the reason why crappy questions keep getting migrated there is to miss the point. Good questions are good questions on all of the sites, and questions that are too vague, that are too argumentative, too localized, and too broad are universal close reasons. There is no special dispensation for SoftwareEngineering.SE to have bad questions, even if you personally think the questions on there suck.  Even the six subjective guidelines for subjective questions are universal guidelines: they affect all sites. So even if you had no idea what the consequences of using the "off topic - belongs on SoftwareEngineering.SE" close reason were, there are still all of the other close reasons for which bad questions, like the ones above, can be closed.


Using the abstract environment in my article seems to affect the whole document in regard to indentation. What am I doing wrong?  \documentclass[11pt]{article} \setlength\parindent{0pt} % sets indent to zero \setlength{\parskip}{10pt} % changes vertical space between paragraphs  \begin{document}  \abstract{Test test test}  \section{Test}  Test  Test  \end{document}

In the article class, it seems that using the abstract environment has an effect to the rest of the document. More precisely, it seems that it redefines the \linewidth, which equals \textwidth without abstract, is smaller with the abstract. My feeling is that \linewidth is redefined for the abstract environment, but the value is not reseted at the end of the abstract.  Here is a minimal example:  \documentclass{article} \begin{document} \abstract{This is an abstract. This is an abstract.}\bigskip  This is text. This is text. This is text. This is text. This is text. This is text.\\  \rule{\textwidth}{3em} \rule{\linewidth}{3em} \end{document}   The output is not the same if you comment the \abstract line or not.  Do you have the same problem as I do when you compile (if not, I will upload some PDF files to show)? Is this a (known) bug in LaTeX2e? How can we circumvent the problem?  Note: I compile with the pdflatex command, and I use pdfTeX, Version 3.1415926-1.40.10 (TeX Live 2009/Debian).


My babies troubling me and each other . They are 11 mo twins . I have decided to put them in their separate cot into their rooms when they cry and come back to their room once they stop crying. Does this sound cruel ?

We have several questions on this site that deal with infants and toddlers who cry a lot, for various reasons.  Here is an  and , . The topic was raised  but no answer was provided. Perhaps we can find a good answer on our site here.  There are two basic approaches:   Leave the child completely alone until the crying stops. <-- This is what I want to address. Leave the child for only a short moment and then return. Repeat with increasing absences.   Is it likely to harm an infant/a toddler to let him intensively cry until he stops on his own?  To elaborate, I have some additional questions:   At what lower age/development limit would the practice be acceptable, and why? What factors could help determine whether the practice would work on a specific child?   For the purpose of this topic, let me define "crying" as real, full-strength, all-out,  non-verbal mommy-daddy-come-help-me crying, not just whining or whimpering. Every parent knows his child and will recognize when the child really cries -- that is what I mean here.  Also, let me define "harmful" as not just transitory sadness but rather something where one could expect negative mid-to-long-term effects such as trauma, separation anxiety, lack/loss of trust in parents and others.  The crying could be related to bedtime/sleep but also during daytime when the parents aren't near.


The question goes like this: The American Diabetes Association estimates that 5.9% of Americans have diabetes. Suppose that a medical lab has developed a simple diagnostic test for diabetes that is 98% accurate for people who have the disease and 95% accurate for people who do not have it. If the medical lab gives the test to a randomly selected person, what is the probability that the person has diabetes given a positive test?  I'm not exactly sure where to start, but I was thinking about the 98% accurate test of positive for those with diabetes and the 5% inaccuracy of the test stating that you have a positive test when you don't. I do note however that 94.1% of the population don't have diabetes whereas 5.9% do have it, which means that there is a greater stress on the inaccurate test of positive for those that don't have the disease.

I am just learning probability in my Discrete Structures class and am very lost. This is the example given in the book and I have no idea how to solve this problem.   Problem: Suppose one in 1000 people have a certain disease. Suppose medical testing is not perfect (as is the case in real life) and consequently, only 99% of the people with the disease are tested positive. Suppose 2% of the people who don’t have the disease also test positive. What is the probability of actually having the disease, given someone tests positive?  Things I do know:   People with disease = 1/1000 Tested positive with disease = 99/100 People tested positive who don't have disease = 2/100   I'm not sure where to got from here with the information that I know. What are the next steps?


I know the answer is supposed to be 2 but I do not understand. $${\lim_{(x,y)\rightarrow (0,0)}} \frac{x^{2}+y^{2}}{\sqrt{x^{2}+y^{2} +1}-1}$$ I tried using intuition by reasoning that the numerator will be virtually $0$, and as the value under the root will be slightly greater than $1$, the root of a value slightly greater than $1$ will also be slightly greater than one. Then by subtracting $1$ that means the answer will be $0$.   Please explain where the flaw in my intuition is.

$$ \lim \limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} $$  According to my textbook the limit equals $2$.  What I have tried:  Using the squeeze theorem:  $$ \lim \limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1}} \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 2} $$ $$ 0 \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} \le 0 $$  I have also tried to use the squeeze theorem with two other equations and obtained different values:  $$ \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2 - 1}{\sqrt{x^2 +y^2 + 1}} \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2 + 1}{\sqrt{x^2 +y^2 + 1} - 2} $$ $$ -1 \le \lim\limits_{(x,y)\to (0,0)} \frac {x^2 + y^2}{\sqrt{x^2 +y^2 + 1} - 1} \le -1 $$


In the below code, how does Python know to print each letter individually? I really can't wrap my head around it.   for letter in 'Python':    print 'Current Letter :', letter   It knows to split the string 'Python' into 6 individual strings. How does it do that?

In C++, I can iterate over an std::string like this:  std::string str = "Hello World!";  for (int i = 0; i < str.length(); ++i) {     std::cout << str[i] << std::endl; }   How do I iterate over a string in Python?


This is an old problem that deserves a bugfix, but it's getting beyond a joke now and I can't seem to work around it.  I keep getting the dreaded failed To download extra data files error in relation to ttf-mscorefonts-installer:    Repeatedly asking it to try again doesn't help, additionally, repeatedly trying-  sudo rm -rf /var/lib/update-notifier/package-data-downloads/partial/* sudo apt-get --purge --reinstall install ttf-mscorefonts-installer   Isn't working either.  I just get at least one 404 error from one of the sourceforge links that stops it working-  Reading package lists... Done Building dependency tree        Reading state information... Done 0 to upgrade, 0 to newly install, 1 reinstalled, 0 to remove and 20 not to upgrade. Need to get 0 B/29.5 kB of archives. After this operation, 0 B of additional disk space will be used. Preconfiguring packages ... (Reading database ... 352049 files and directories currently installed.) Preparing to unpack .../ttf-mscorefonts-installer_3.4+nmu1ubuntu2_all.deb ... mscorefonts-eula license has already been accepted Unpacking ttf-mscorefonts-installer (3.4+nmu1ubuntu2) over (3.4+nmu1ubuntu2) ... Processing triggers for fontconfig (2.11.94-0ubuntu1.1) ... Processing triggers for update-notifier-common (3.168.2) ... ttf-mscorefonts-installer: processing... ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/andale32.exe Get:1 http://downloads.sourceforge.net/corefonts/andale32.exe [198 kB] Fetched 198 kB in 0s (339 kB/s)                                                 W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/andale32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/arial32.exe Get:1 http://downloads.sourceforge.net/corefonts/arial32.exe [554 kB] Fetched 554 kB in 0s (575 kB/s)                                                 W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/arial32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/arialb32.exe Get:1 http://downloads.sourceforge.net/corefonts/arialb32.exe [168 kB] Fetched 168 kB in 0s (306 kB/s)                                                 W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/arialb32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/comic32.exe Err:1 http://downloads.sourceforge.net/corefonts/comic32.exe   404  Not Found W: Can't drop privileges for downloading as file '/var/lib/update-notifier/package-data-downloads/partial/comic32.exe' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) E: Failed to fetch https://netix.dl.sourceforge.net/project/corefonts/the fonts/final/comic32.exe  404  Not Found  E: Download Failed Setting up ttf-mscorefonts-installer (3.4+nmu1ubuntu2) ...   The specific point at which it fails to download changed - it seems to be a sourceforge reliability problem, but this has now been going on weeks and results in annoying popups as above all the time.  How do we get this fixed and/or how can I work around it for now.

After fresh install 12.04 I && updating apt and system restart, I always get this annoying message after reboot :     Failure to download extra data files      The following packages requested additional data downloads after   package installation, but the data could not be downloaded or could   not be processed.      ttf-mscorefonts-installer      The download will be attempted again later, or you can try the   download again now. Running this command requires an active Internet   connection.   But if I run attempt now, it shows flashing terminal window and like nothing happen. It'll happen again when I restart system.  I found someone have  too, but he haven't replied yet.   I'm a newbie here, please help.


Predators at the top of a food chain, like lions, seem to have a relatively low fertility rate, which fits well to the ecosystem and avoids overpredation. But what is the mechanism that keeps the fertility rate at this level? A mutation that increases fertility among the predators should quickly spread in such a population, eventually leading to an increase of the predator fertility rate followed by overpredation. But it seems that this is usually not the case. What does keep the fertility rate of predators at the level they are?  P.S: Many explanations on population dynamics cite Lotka Volterra, including the existing question on Bio.SE "". Population dynamics predict orbits for the population sizes of predator and prey. Still this does not explain why the fertility rate of predators shouldn't go up.

I've often heard that a population, human or otherwise, will continue to grow as long as there is food available (assuming nothing else is killing them off).  It makes sense: if you have food you can live, and if nothing is hunting you you'll survive to reproduce.  I recently designed a piece of software to simulate an ecosystem, with groups of creatures of different species eating and hunting and reproducing alongside each other.  It was very simplified (each animal had simple attack/defense/speed/stealth values, etc), but something became rapidly apparent: in every simulation the predators overwhelmed the prey, reproducing until their numbers could not be sustained by the herbivores, and leading to an inevitable die-off of both groups.  I could delay the die-off by adjusting different values and initial population counts, but it would always happen eventually.  The predators would eat and breed and eat and breed until the entire system collapsed.  At first I thought it was just the product of my over-simplified system, but it got me thinking: what prevents predators from overpopulating in real life?  It seems like the natural tendency would be for (for example) the sharks to continue breeding and eating until all the fish are gone, or the wolves to eat all the deer, etc.  Obviously some predators have predators of their own, but that's just putting off the question: if the hyenas don't overpopulate because the lions eat them, then what's keeping the lions from overpopulating?  I can't come up with anything that would prevent the apex predators from growing too numerous, then fighting each other over a dwindling prey population, then dying off entirely when there was no more food to find.  Do predator populations self-regulate to prevent putting undo stress on their prey populations?  Or is there some other mechanism to keep the predator hierarchy from becoming top-heavy?


Let's say that I happen by a star that has just burned out and is collasping into a black hole. I seat at infinity to watch it as a Schwarzschild observer. Will I ever see the black hole collapse into a black hole in finite time? Or will only become a black hole in the limit? Does a singlarity form in finite time or infinite time?

Possible Duplicate:          Is black hole formation observable for a distant observer in finite amount of time? Specifically, let's take uniform non rotating distribution of 10 solar masses within solar radius, assume no outward pressure, and calculate its gravitational collapse. I assume distant observer would never witness complete formation of black hole with event horizon corresponding to entire 10 solar masses. What would be observable in finite amount of time, then? For example, would there be a black hole with smaller radius, while the rest of mass is still falling into its event horizon?


Anime film or series from the 80's. There is this hostile extraterrestrial force that attacks the planet. Action takes place in space near the planet and with spaceship battles. The planet sea level is rising (because of global warming?). At some point, someone compares the estimated landmasses with the attackers' planet resulting in a similar area, suggesting that they come from the future.

I'm trying to identify an old anime movie from my childhood. I saw it around the might-eighties.  It was a space opera, and I can recall the following elements:   A big space fleet that is escaping their dying homeworld attacks Earth in order to conquer it. There might have been some time travel paradox or loop involved, like the invading fleet turning out to be from a future Earth or somesuch. Visual element: I believe a flashback (or perhaps a dream sequence) had a rose in it.


It was in an economics paper and I've been searching for it for 20 minutes with no luck.  I've tried detexify and most normal packages. amsfonts  and dsfont  both don't fit the bill

I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out?


was posted a couple of days ago that was blatantly off topic. I do not yet have 3,000 reputation here so I am unable to vote to close a question. Instead I flagged it with the "Blatantly off-topic" reason:    One minute after I flagged it, someone edited the post to make it ask for a site recommendation for where to ask the question that had originally been posted. Now, of course, the question is on topic. The question went through the close review queue and unsurprisingly got three votes to be left open. This caused my flag to be declined.  As I understand it, there is some kind of penalty for having a certain number of flags declined. It seems odd that I could possibly get into this situation by flagging a question for a perfectly valid reason which only became invalid due to a change that was made after I flagged it.  Is this ? Should I not flag posts for closure due to the concern that they might later be edited which will render my flag retroactively invalid?  Here are some screenshots just to show the timeline:   This one shows that I flagged the post at 16:52:38.    This one shows that the post was edited at 16:53:41.    This one shows the three leave open votes over the course of the next hour or so, with the final one coming at 17:59.    And this one shows that the flag was declined at precisely 17:59, i.e. as soon as the review was completed.

Earlier today I flagged this  using the following flag option:     Questions asking us to recommend or find a tool, library or favorite off-site resource are off-topic for Stack Overflow as they tend to attract opinionated answers and spam. Instead,  and what has been done so far to solve it.   If you look at the edit history, shown below, I interpreted the original post's title and body to mean that they were asking for another utility, like SlowCheetah, which is why I flagged it with the rule I stated above.  In addition, I try to do my best to also inform the user that their post does not meet the standards of the site by leaving a comment as you can see on the post.  The poster acknowledged the feedback and updated their question, rendering my flag now invalid.    Ultimately, my flag was declined, which harms me because as we all know declined flags work against a SO user's total flag count:  Reference:      How many flags do I have?      When you start out, you are allotted 10 flags per day. This number may increase to up to 100 flags per day:      You get one bonus flag per 2000 reputation.      You are awarded additional bonus flags when you flag correctly - one bonus flag for every ten net helpful flags (helpful flags minus declined flags).   I only have 8 declined flags, and IIRC, 4 of those are because of situations just like this. So is it fair to negatively affect a member's total flag count, when the flag at the time of submission was accurate?  As such, I propose a new flag status like "Inapplicable', which when used does not affect total flag count, or something similar to this, so that situations like this do not negatively affect a user's flag count.   I understand I still have to have faith that a reviewer or moderator will see the post for what it was at the time the flag was submitted, but at least by adding this option, you provide reviewers and moderator's a means to take action in a fair manner.  I want to continue flagging questions and helping posters as much as I can, I just don't think it's fair to members that spend a lot of time flagging and helping members, to risk reducing their flag count just because of a shortfall of the system and because, let's be honest here, not all moderator's can act at the same level of objectivity, we all have differing viewpoints and interpretations.  I suppose this bothers me more than other issues I've come across on the site because I flag posts to help keep the site focused and free of poor posts and yet receive no reputation for these types of efforts.  The only positive thing you can reap are a few badges, <sarcasm>yay!</sarcasm> or a negatively impacted flag count.  Just doesn't seem fair IMHO when my affects contribute to increasing the quality of posts which is just as important as contributing a quality answer IMO.  And to add, this isn't the first time this has happened to me and many other members of the site.  And yet, nothing has been done about it. Perhaps as a community we start spending a little bit more time little details like this to help keep people feeling positive about their efforts, especially those that aren't measured by reputation.  Thank you for your time,  Cheers.


I understand that static pressure is a scalar quantity as it acts equally in all directions, then by the same reasoning dynamic pressure should be a vector quantity as it only can be measured by opposing the flow.  I understand that the act of opposing the flow will instantly convert dynamic to static but I am asking in theory?   Thanks all the answers ( @Nikos M. ) and assistance , However I am still unclear as to why dynamic pressure (at any instant) is not thought of to be a force acting in a specific direction (perhaps vector is not the right term ?)

I have a final exam tomorrow for fluid mechanics and I was just looking over the practice exam questions. They do not provide solutions. But pretty much I have to define pressure at a point and also say why pressure is scalar instead of a vector.  I am thinking pressure at a point is $P=\lim_{\delta A \to 0} \frac{\delta F}{\delta A}$. Please let me know if I am wrong.   But I do not know at all why pressure is a scalar instead of a vector. I know it has something to do with $d \mathbf{F}=-Pd \mathbf{A}$


to my answer was nice and added example code. It improved the answer. Somehow four reviewers have rejected it! I have since manually added the code to the answer, but the reviews were IMHO ridiculous.  Could the moderators remove any black marks the editor (also asker of the question) got for this incorrectly rejected edit?

A nice user suggested  to . The edit, though very good and desirable, was rejected. I do not understand the reasons, and I did not find a way to contact those people who rejected it. What can I do to re-approve the edit?


I updated my MiKTeX today. Now, I do not get any error without packages but it can not compile my latex files with packages.  Uninstalling and reinstalling both Texmaker and Miktex did not work. I could not find l3regex.sty file on internet.     LaTeX Error: File `l3regex.sty' not found.   My packages:  \usepackage[colorlinks=true, linkcolor = blue, urlcolor  = blue, citecolor = blue, anchorcolor = red]{hyperref}   \usepackage[utf8]{inputenc}   \usepackage[top=1cm, bottom=2cm, left=1.5cm, right=1.5cm]{geometry}   \usepackage{amsfonts}   \usepackage{amsmath}   \usepackage{amssymb}   \usepackage{graphicx}   \usepackage{microtype}   \DisableLigatures{encoding = *, family = * }   \usepackage{coloring}   \pagenumbering{gobble}

I would like to try a package which seems interesting, but it some dependencies are not satisfied.   Here is my minimal example:  \documentclass{article}  \usepackage{pkgloader} \LoadPackagesNow  \begin{document}     pckloader trial \end{document}   And I get the following error: ! LaTeX Error: File 'l3regex.sty' not found.. Therefore, I tried to update my distribution with the linux commands  tlmgr update --self tlmgr update --all   But the package l3regex is still not foundable. Plus, my computer is not lying since l3regex.sty is not in my folder /texmf-dist/tex/latex/*.  So, is it something normal ? How can I workaround this problem ?


So I created my users.... Now for each of there dir's I have to create the following structure.  Users Home Directory / Staff / Info / Personal   Then create a file in each dir called file1.txt, file2.txt, file3.txt   I tried something like mkdir  create "users home directory / staff / info / personal but had no success I also cant find any help from research online. Yes I am very new to Ubuntu!

I know that touch command creates a file:  touch test1.txt   but how I can create a file and its full path?  for example my desktop contains nothing:  ~/Desktop/$ ls ~/Desktop/$   and I want to create 1.txt in ~/Desktop/a/b/c/d/e/f/g/h/1.txt. Can I do this with a simple command like:  $ touch ~/Desktop/a/b/c/d/e/f/g/h/1.txt   instead of create full path manually and then create the file?


I'm encountering problems with biblatex (Biber as backend).  When defernumbers=true is specified references show all as [0] (style=numeric-comp) both in the text and in the numbering of the bibliography section. Without the option references are printed normally but of course numbering in the text follows the order in the bibliography.  TexLive is updated and I'm using TexStudio.  Complete call of package:  \usepackage[style=numeric-comp, defernumbers=true, firstinits=true, hyperref, useprefix, backref, url=false, isbn=false, backend=biber]{biblatex}   Edit: I'm using latest version of biblatex and biber. I run pdflatex then biber then pdflatex 2 times. Now the result do not change despite defernumbers is 'true' or 'false' as the order is alphabetical and not following citing order in the text.  Here the short example:  \documentclass[]{article}  \usepackage{filecontents}  \begin{filecontents*}{123.bib} @book{Aaa2001,     author = {Aaa, A.},     year = {2001},     title = {The \TeX book 1}, } @book{Bbb2002,     author = {Bbb, B.},     year = {2002},     title = {The \TeX book 2}, } @book{Ccc2003,     author = {Ccc, C.},     year = {2003},     title = {The \TeX book 3}, } @book{Ddd2004,     author = {Ddd, D.},     year = {2004},     title = {The \TeX book 4}, } \end{filecontents*}  \usepackage[style=numeric-comp, defernumbers=true, firstinits=true, hyperref, useprefix, backref, url=false, isbn=false, backend=biber]{biblatex}  \addbibresource{123.bib}  \begin{document}  Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua \cite{Bbb2002}.  Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat \cite{Ddd2004}.  Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.    \nocite{*} \printbibliography  \end{document}

I'm facing a problem with biblatex citation order.  Using this configuration:  \documentclass {article} \usepackage[brazil]{babel} \usepackage[utf8]{inputenc} \hyphenation{es-ta-bi-li-da-de} \usepackage{setspace} \singlespacing \usepackage[natbib=true,style=numeric]{biblatex} \addbibresource{frameworks.bib}   Being frameworks.bib this:  @Article{JONHSON88, author = {Ralph Johnson, Brian Foote}, title = {Designin Reusable Classes}, journal = {Journal of Object-Oriented Programming SIGS}, year = {1988}, key = {Johnson:88}, volume = {1}, number = {5}, pages = {22-35}, month = jun }  @book{UML-F:00, author = {Fontoura M., Pree W., Rumpe B.}, editor = {Addison-Wesley}, title = {The UML Profile for Framework Architectures}, year = {2000}, }   The PDF is generated with a text like:  Something about something[4], and moo foo other children[1].   This citation [4] is the first in all text. How can I order this correctly to [1]...[2] ...?


I format my Laptop yesterday and install Windows 10.  I didn't add a license key, but it seems like windows 10 activated automatically.  How was that possible?

If you activated a free upgrade to Windows 10 or bought and activated   Windows 10 from the Microsoft Store, you have a digital license for   your device. This means you can reinstall the same edition of Windows   10 that your device has a digital license for without entering a   product key. During reinstallation, if you’re asked to enter a product   key, you can skip this step. Windows 10 will automatically activate   online after the installation is complete.   source:   Does MS digital license 'fingerprint' hardware information  during the free upgrade / activation and store it (at Microsoft) , so that the next re-install queries MS for the fingerprint and activates Windows 10?  Thought the disk drive may change, I expect that none of the other fingerprinted hardware will change.


At the end of Ragnarok, the ship with the surviving Asgardians is stopped by Thanos.  In the beginning of Infinity War, we see that Thanos has killed a large number of Asgardians in his effort to kill half of the universe's population.  However, in this scene, their ship is destroyed and we only see one Asgardian (Thor) who is spared.  We later learn in Endgame that a number of Asgardians were presumably saved by Valkyrie and brought to Earth. The killings of the Asgardians looked total - we didn't see Thanos sparing half of them in IW.  I remember seeing people assume that Valkyrie saved the half of the Asgardians that Thanos spared, but in retrospect that wouldn't make sense.  How would that have gone - did Thanos just appear and say that he'd kill half of them and he'd give the other half the chance to escape, so Valkyrie left with them?  It definitely doesn't look like things went that smoothly.  Or did Thor and Loki see Thanos coming and convince Valkyrie to escape with whoever she could bring?  Why, then, did Thanos kill all of the Asgardians?  Did he?  What exactly happened in between these two movies?

Thor: Ragnarok ends with the remaining people of Asgard aboard a refugee ship that meets Thanos' ship. Avengers: Infinity War opens with      Thanos and his minions having commandeered the ship and several bodies can be seen on the floor.   This begs the question, what happened to these characters:   Korg Miek Asguardian extra #3 Valkyrie


I'm trying to create MBTiles from GeoTIFF datasets (UTM33 projection). I have tried the following command  gdalwarp -of MBTiles -t_srs EPSG:3857 -co "QUALITY=80" tiffs\*.tif  dataset.mbtiles   The result is this error:  ERROR 6: Could not find an appropriate zoom level that matches raster pixel  size Open GDAL Datasets: 1 N MBTiles      -1 65701x77489x3 C:\Data\Testdata\dataset.mbtiles   I also tried to warp each TIF to EPSG:3857 and then creating a .vrt first, and then the following command:  gdalwarp -of MBTiles -co "QUALITY=80" tiffs.vrt dataset.mbtiles   with the exact same result.  I'm completely unable to get it to work, even though the  explicity says that it should work ("The driver implements the Create() and IWriteBlock() methods, so that arbitrary writing of raster blocks is possible, enabling the direct use of MBTiles as the output dataset of utilities such as gdalwarp.")  So the question is, am I missing something in my commands or is GDALWarp and MBTiles simply not supported in GDALWarp?

I am trying to create raster file in the Mbtiles format. I tried , $ gdal_rasterize -ot Byte  -burn 255 -burn 0 -burn 0 -ts 4950 4090 -of MBTiles station.geojson station.mbtiles   I'm using,  $gdalinfo --version : GDAL 2.1.3, released 2017/20/01  Error:  > ERROR 1: Cannot find min and max zoom_level >  > ERROR 6: Could not find an appropriate zoom level that matches raster > pixel size >  > ERROR 6: Only EPSG:3857 supported on MBTiles dataset > 0...10...20...30...40...50...60...70...80...90...100 - done. >  > ERROR 6: IWriteBlock() not supported if georeferencing not set >  > ERROR 6: IWriteBlock() not supported if georeferencing not set >  > ERROR 6: IWriteBlock() not supported if georeferencing not set   EDIT:  $ ogrinfo station.geojson -so -al  INFO: Open of 'stations.geojson' using driver 'GeoJSON' successful. Layer name: OGRGeoJSON Geometry: Point Feature Count: 86 Extent: (-77.272622, 38.766522) - (-76.842038, 39.119927) Layer SRS WKT: GEOGCS["WGS 84", DATUM["WGS_1984",    SPHEROID["WGS 84",6378137,298.257223563,         AUTHORITY["EPSG","7030"]],     AUTHORITY["EPSG","6326"]],  PRIMEM["Greenwich",0,    AUTHORITY["EPSG","8901"]],  UNIT["degree",0.0174532925199433,    AUTHORITY["EPSG","9122"]],  AUTHORITY["EPSG","4326"]] name: String (0.0) marker-color: String (0.0) marker-symbol: String (0.0) line: String (0.0)`


The Disk Utility on my Mac shows 100GB of usage by 'Other'.   I had a look inside ~/Library/Caches, but I did not see anything taking up too much space in there.       I even tried using an app called "Clean my Mac". It didn't do much good.      Here is my question:  How do I find and delete the files that are taking up nearly 100GB of space and are marked as 'other' in Disk Utility.  I am on El Capitan on a 13 inch 2015 MacBook Pro.

Every few days I get notices on my MacBook that it's running or run out of hard drive space. Curiously, restarting the computer will enable me to recover gigabytes of space (this past time, it was able to recover about 2.2GB). However, I can't identify anything in my personal activity that consumed that space.  It's possible that it's a rogue iTunes podcast or a huge software update that my Mac is automatically downloading - would either of these reclaim the space upon a restart?  One possibility that I can think of is that FileVault has some sort of disk leak, allocating but not freeing files. Does this make sense? Is there a tool that I can run to determine where this space is going? Assuming it is FileVault, should I try to disable it? What's the best way to turn of FileVault on a nearly full computer?


$\sum_{k=1}^{n}k\binom{n}{k} = n2^{n-1}$  I have tried both induction and transforming both sides to get equality but no luck  I know that   $\sum_{k=1}^{n}\binom{n}{k} = 2^{n}-1$ and $\sum_{k=1}^{n}k=\frac{n(n+1)}{2}$  p.s: I couldn't find something similar of this kind anywhere. But I thinks it's something that is related to Pascals rule. Please point out little hints, thank you

Proof that $\suṃ̣_{k=1}^{n}k {n \choose k}$ for $n \in \mathbb N$ is equal to $n2^{n-1}$.  As a hint I got that $k {n \choose k} = n {n-1\choose k-1} $.  I tried solving this by induction but, in the inductive step I'm not arriving to the correct result.


My laptop went down a few days ago and I lost my short sound script.  I thought someone here could help me rebuild it.  It was something like this:  Better post:  if sound prog were "pback" the command would be   pback file[s]  #! FILE=$1;  cat FILE | [forgotten command]  #End   Can anybody help me with the command?

How to get speech output from entered text by using command-line?  Also facility to change speech rate, pitch, volume etc using simple command.


I have Ctrl+Alt+T assigned as my keyboard shortcut to launch a Terminal window, but it stopped working after upgrading to 12.10.  I have verified that it is still set in the Keyboard Shortcuts settings menu, and have verified that other shortcuts (e.g. Ctrl+Alt+C to open calculator) work.  I have also tried using assigning different key combinations to Terminal, to see if that helps (it doesn't), e.g. unassigning Ctrl+Alt+C from calculator, and instead assigning it to Terminal. No dice.  Any ideas what might be going on?

I'm using Ubuntu 12.04, and till day before yesterday, the shortcut was working perfectly. But when today I pressed it, it didn't open terminal. The terminal app still works. I am on GNOME3 3.4.2, and I updated recently using apt-get install gnome-shell  The Keyboard shortcuts window shows no problem -    Pls. help, what should I do now?


I just installed Ubuntu 20.04, and I would like to change the tab switching shortcuts from Ctrl + PageUp/PageDown to the more natural Ctrl + Tab / Ctrl + Shift + Tab. How can I do this?

I want to remove Videos and Music from the left side panel. But, I can't seem to find the option to do so. How do you do that?


I often use the pattern 'I appreciate your noticing this' but recently decided it sounds strange, and switched to 'you'. (I do this with different verbs; this is just an example.) Are they both valid?

I assume that the following sentences are grammatically correct:   He resents your being more popular than he is. Most of the members paid their dues without my asking them. They objected to the youngest girl's being given the command position. What do you think about his buying such an expensive car? We were all sorry about Jane's losing her parents like that.   I'm still getting used to this possessive gerund structure. It sounded so weird to me at first. Is the structure used in both formal and informal contexts? Are there any alternative structures that result in the same meaning and are more frequently used? (Examples taken from )


I am creating a series of illustrations for package design. I have had a few issues so far following Live Paint.  I created my image with the brush tool>expand>delete unwanted>Live paint Then I merge the image into one. This is where I get a problem, there appears to be a dotted white line around the outline of my image.  It appears worse on PDF export, see the image for reference.

I converted a raster image to vector in Illustrator CS6 using Image Trace then the Expand option, though when I save as an svg the image looks embossed. I suspect it's due to the layer background being white and the paths not lining up, but I'm unsure how to fix it or prove that theory without manually having to adjust every path.   This is how it looks in Illustrator before I export it:    The image looks like this when saved/exported with art optimized option:


How to cover this code?     Test class Code        @isTest static void getPageNumberListTest(){     Controller controller = new Controller();       controller.TotalPages=10;     controller.getPageNumberList();  }   Conroller Class  public Integer TotalPages { get {        if (setList.getResultSize() <= 10)         this.TotalPages = 1;     if (Math.Mod ( setList.getResultSize(), setList.getPageSize() ) == 0)         this.TotalPages = ( setList.getResultSize() / setList.getPageSize() );     if (Math.Mod ( setList.getResultSize(), setList.getPageSize() ) != 0)      this.TotalPages = ( setList.getResultSize() / setList.getPageSize() )+1;     return TotalPages; } set;    }  public Integer TotalRecords {     get {          this.TotalRecords = setList.getResultSize();         return TotalRecords;     }     set; } public ApexPages.StandardSetController setList { get {     if (setList == null) {          setList = new ApexPages.StandardSetController(Database.getQueryLocator(         [SELECT  Name, Email, Contact_Level__c, AccountID, OwnerID, CreatedByID, CreatedDate FROM Contact]));     }     if (this.PageSize == null) PageSize = 10;      setList.setPageSize(PageSize);        return setList; } set;   }

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  This canonical question is intended to address several classes of common questions by providing a quick summary and links to comprehensive resources:   How is code coverage obtained and calculated? How do I increase my coverage?  Why can't I cover these lines? Why isn't the body of my loop or conditional statement covered?


we are using Postfix 2.11.3 on Ubuntu 15.10  Here is configuration file:  smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)   biff = no   append_dot_mydomain = no   readme_directory = no   smtpd_use_tls=yes   smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache   smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache   myhostname = server.ip-5.ru   alias_maps = hash:/etc/aliases   alias_database = hash:/etc/aliases   virtual_alias_domains =  virtual_alias_maps = hash:/etc/postfix/virtual   myorigin = /etc/mailname   mydestination = $mydomain   mynetworks = 0.0.0.0   mailbox_command =    mailbox_size_limit = 0   recipient_delimiter = +   inet_interfaces = all   inet_protocols = ipv4   home_mailbox = Maildir/   soft_bounce = yes   header_checks = regexp:/etc/postfix/header_checks   smtpd_relay_restrictions = permit_mynetworks, reject_unauth_destination,permit   smtpd_recipient_restrictions = permit_mynetworks,reject_unauth_destination,permit     Now, I send mail to local user from local user inside our domain "ip-5.ru" The send and delivery is successful. name@ip-5.ru -> other@ip-5.ru  If I send mail to local alias connected to remote mailbox, it is also succeessful. name@ip-5.ru -> other@ip-5.ru -> name@gmail.com    The problem come, when I send mail from local user to remote mail box in gmail.com. name@ip-5.ru -> name@gmail.com    I get:   NOQUEUE: reject: RCPT from unknown[xx.xx.xx.xx]: 454 4.7.1 <name@gmail.com>: Relay access denied; from=<name@ip-5.ru> to=<name@gmail.com> proto=ESMTP helo=<[yy.yy.yy.yy]>   I read that we need use SSL for get relay privileges... So why I can relay via local alias? The problem that SSL is very hard for configuration now... I tried to configure it and get much errors...    I want put your attention, that user names and passwords are provided for SMTP authentication, so my server isn't target for spam and unlimited relay, I just want find some way around SSL!  Is it possible to send from local mailbox directly to remote without making alias and without SSL?

This morning, in order to correct a problem with a name mismatch in the security certificate, I followed the recommended steps from , but now, when attempting to send an email from a client (in this case the client is Windows Mail), I receive the following error.     The rejected e-mail address was   'email@gmail.com'. Subject 'This is a   test. ', Account: 'mail.domain.com',   Server: 'mail.domain.com', Protocol:   SMTP, Server Response: '554 5.7.1   : Relay access   denied', Port: 25, Secure(SSL): No,   Server Error: 554, Error Number:   0x800CCC79   Edit: I can still retrieve emails from this account, and I send emails to other accounts at the same domain. I just can't send emails to recipients outside of our domain.  I tried disabling TLS altogether but no dice, I still get the same error.  When I check file mail.log, I see the following.  Jul 18 08:24:41 company imapd: LOGIN, user=user_name@domain.com, ip=[::ffff:111.111.11.11], protocol=IMAP Jul 18 08:24:42 company imapd: DISCONNECTED, user=user_name@domain.com, ip=[::ffff:111.111.11.11], headers=0, body=0, rcvd=83, sent=409, time=1 Jul 18 08:25:19 company postfix/smtpd[29282]: connect from company.university.edu[111.111.11.11] Jul 18 08:25:19 company postfix/smtpd[29282]: NOQUEUE: reject: RCPT from company.university.edu[111.111.11.11]: 554 5.7.1 <email@gmail.com>: Relay access denied; from=<user_name@domain.com> to=<email@gmail.com> proto=ESMTP helo=<UserPC> Jul 18 08:25:19 company postfix/smtpd[29282]: disconnect from company.university.edu[111.111.11.11] Jul 18 08:25:22 company imapd: DISCONNECTED, user=user_name@domain.com, ip=[::ffff:111.111.11.11], headers=13, body=142579, rcvd=3289, sent=215892, time=79   File main.cf looks like this:  # # Postfix MTA Manager Main Configuration File; # # Please do NOT edit this file manually; #  # # Postfix directory settings; These are critical for normal Postfix MTA functionallity; #  command_directory = /usr/sbin daemon_directory = /usr/lib/postfix program_directory = /usr/lib/postfix  # # Some common configuration parameters; #  inet_interfaces = all mynetworks = 127.0.0.0/8 mynetworks_style = host  myhostname = mail.domain.com mydomain = domain.com myorigin = $mydomain  smtpd_banner = $myhostname ESMTP 2.4.7.1 (Debian/GNU) setgid_group = postdrop  # # Receiving messages parameters; #  mydestination = localhost, company  append_dot_mydomain = no append_at_myorigin = yes transport_maps = mysql:/etc/postfix/transport.cf  # # Delivering local messages parameters; #  mail_spool_directory = /var/spool/mail mailbox_size_limit = 0 mailbox_command = procmail -a "$EXTENSION"  biff = no  alias_database = hash:/etc/aliases  local_recipient_maps =  # # Delivering virtual messages parameters; # virtual_mailbox_maps=mysql:/etc/postfix/mysql_virt.cf virtual_uid_maps=mysql:/etc/postfix/uids.cf virtual_gid_maps=mysql:/etc/postfix/gids.cf virtual_mailbox_base=/usr/local/virtual virtual_maps=mysql:/etc/postfix/virtual.cf virtual_mailbox_domains=mysql:/etc/postfix/virtual_domains.cf   # # SASL paramters; # smtp_use_tls = yes smtpd_use_tls = yes smtpd_tls_auth_only = yes smtpd_tls_loglevel = 1 smtpd_tls_received_header = yes smtpd_tls_session_cache_timeout = 3600s  smtp_tls_CAfile = /etc/postfix/ssl/smptd.pem smtp_tls_cert_file = /etc/postfix/ssl/smptd.crt smtp_tls_key_file = /etc/postfix/ssl/smptd.key  smtpd_tls_CAfile = /etc/postfix/ssl/smptd.pem smtpd_tls_cert_file = /etc/postfix/ssl/smptd.crt smtpd_tls_key_file = /etc/postfix/ssl/smptd.key  smtpd_sasl_auth_enable = yes  smtpd_sasl_security_options = noanonymous  smtpd_sasl_local_domain =  broken_sasl_auth_clients = yes  smtpd_sender_restrictions =         permit_sasl_authenticated         permit_mynetworks  smtpd_recipient_restrictions =         permit_sasl_authenticated         check_recipient_access hash:/etc/postfix/filtered_domains         permit_mynetworks         reject_unauth_destination   As a side note, my employer wants to be able to send emails from clients (Thunderbird and Outlook) both from within our local network and outside it.


I'm given: $4x+51y=9$.  I am given a hint that when we use $4x=9 \pmod{51}$ we get $x = 15 + 15t$, and also if we use the congruence $51y=9 \pmod 4$ we get $y=3+4s$. They say it's handy to then find the relation between $s$ and $t$.  I have no idea how they got those suggestions and I need to know how to do that too.  I'm really stuck :(

So, a question in Elementary Number Theory by David M. Burton:     Problems 4.4      2(a) Using congruences, solve the diophantine equation 4x + 51y = 9       Hint: $4x \equiv 9(mod \ 51) $ gives $ x = 15 +51t$, whereas $ \ 51y \equiv 9 (mod \ 4)$ gives $y = 3+4s $. Find the relation between $s$ and $t$ From this hint, I substitute $ x = 15 +51t$ and $y = 3+4s$ in the given equation $4x + 51y = 9$ to get the relation $s = -t-1$ and using which I can get the solutions $ x = 15 + 51t, \ y =-1-4t$ But we know that the solutions of $ax \equiv b (mod \ n)$ is equivatent to the solutions of the diophantine equation $ax -ny = b$, so, solutions of $4x \equiv 9(mod \ 51) $ is equivalent to solutions of the equation $4x-51y=9$ whereas, solutions of $51y \equiv 9(mod \ 4) $ is equivalent to solutions of the equation $-4x+51y=9$ Now, my question is: as, the above equations $4x-51y=9$ and $-4x+51y=9$ are different, then what is the point of substituting $ x = 15 +51t$ (solution of $4x-51y=9$) and $y = 3+4s $ (solution of $-4x+51y=9$) in the given equation $4x+51y=9$ to find a relation between $t$ and $s$ ? Isn't it absurd as $ x = 15 +51t$ and $y = 3+4s $ are solutions of two different equations? Can anyone please explain this? PS: I did it like this $4x \equiv 9(mod \ 51) $ gives $ x = 15 +51t$ and by substituting it in $4x+51y=9$ we get $y=-1-4t$


I want to create an array which has 20 elements and each element holds different integer numbers from closed interval [0-19].    Here is the codeblock:  #include<stdio.h> #include<stdlib.h> #include<time.h> #define SIZE 20  int main()  {     srand(time(NULL));      int array[SIZE]={0}, arrayhold[SIZE]={0}, hold, i;      for(i=0;i<SIZE;i++)      {         hold = rand()%20+1;          if(arrayhold[hold]==0)         {             array[i]=hold;             arrayhold[hold]++;         }         else          {             while(arrayhold[hold]!=0)                 hold = rand()%20+1;              array[i]=hold;         }     }      for(i=0;i<SIZE;i++)      {         printf("array[%d]=%d\n",i,array[i]);     } }        When I run the program, the output gives array[random]=1 for many times, but it never gives array[random]=3 (just for example).

I'd like to generate unique random numbers between 0 and 1000 that never repeat (i.e. 6 doesn't show up twice), but that doesn't resort to something like an O(N) search of previous values to do it. Is this possible?


I read this in the late 80's early 90's as a long paperback novel. The earth hits a cosmic string, humans DNA is damaged. The main character is a "White Card" his DNA is pure. He is a slave/worker for someone who recognizes that he is a white card and is trying to make him into a "Protoman". He kills the guy and tangles his body in a fishing net to give the appearance that it was an accident. He escapes. The rest I don't remember much.

I read a futuristic sci-fi book in the 1980's (maybe the 70's), about an overweight orphan who lived in slums, known as "the rat" (not the stainless steel rat), who was conscripted into space military service (in chapter 1). He was trained and became a powerful warrior and teamed up with others, and towards the end may have overthrown the governing beings.


Is There A Command I Can Use To Turn Off The Screen On My Laptop Running Ubuntu 20.04

I am using xfce desktop in ubuntu 12.04 and added the shortcut keys in order to turn off my monitor.  The command "xset dpms force off" works fine in terminal.  But when it added in the keyboard shortcuts, the monitor turns off a second then turns on immediately.     So how can I turn off the monitor using hotkeys?


def indexes(word, letter):     acc=[]     for i in word:         for g in letter:             if g in i:                 acc.append(word.index(i))     return acc   if i call the function indexes("mississippi","s") the following is returned:  [2, 2, 2, 2]   So, the function returns the correct amount of letters, but it only returns the first index of where "s" is found and fills the list with that index. Any reason why the list doesn't return the index of each "s"?

Given a list ["foo", "bar", "baz"] and an item in the list "bar", how do I get its index (1) in Python?


I have this XQuery for my extended event session which works fine but when I try joining the plan_handle to dm_exec_query_plan to get the query plan, it says      Msg 257, Level 16, State 3, Line 1 Implicit conversion from data type   varchar to varbinary is not allowed. Use the CONVERT function to run   this query.   If I convert to varbinary, this is the error I receive.     "Msg 569, Level 16, State 5, Line 1 The handle that was passed to   dm_exec_query_plan was invalid. "   If I manually pass the handle into the DMF, it works just fine. This is how it looks like in varchar format (after adding the 0x)     0x06000700f9971028f01033ae0300000001000000000000000000000000000000000000000000000000000000   SELECT         q.Time         ,q.[CPU (ms)]         ,q.[Duration (s)]         ,q.[SQL Statement]         ,q.plan_handle FROM ( SELECT         data.value(     '(/event[@name="sql_statement_completed"]/@timestamp)[1]', 'DATETIME') AS [Time]         ,data.value(        '(/event/data[@name=''cpu'']/value)[1]', 'INT') AS [CPU (ms)]         ,CONVERT(float, data.value('(/event/data[@name="duration"]/value)[1]', 'BIGINT')) / 1000000         AS [Duration (s)]         ,data.value(         '(/event/action[@name=''sql_text'']/value)[1]', 'VARCHAR(MAX)') AS [SQL Statement]         --,data.value('(/event/action[@name=''plan_handle'']/value)[1]', 'varchar(4000)')       AS [PlanHandle]         ,'0x' + CAST(data.value('(/event/action[@name="plan_handle"]/value)[1]', 'varchar(4000)') AS varchar(4000)) AS plan_handle     FROM (         SELECT             CONVERT(xml, event_data) AS data         FROM sys.fn_xe_file_target_read_file         ('H:\SQLskills\EE_ExpensiveQueries*.xel', 'H:\SQLskills\EE_ExpensiveQueries*.xem', NULL, NULL)     ) entries     )q     CROSS APPLY sys.dm_exec_query_plan(plan_handle)

I've been keeping a log of expensive running queries, along with their query plans, in a table to allow us to monitor trends in performance and identify areas that need optimising.  However, it's come to the point where the query plans are taking up too much space (as we're storing the entire plan against each query).  I'm therefore attempting to normalise the existing data by extracting the QueryPlanHash and QueryPlan to another table.  CREATE TABLE QueryPlans (     QueryPlanHash VARBINARY(25),     QueryPlan XML,     CONSTRAINT PK_QueryPlans PRIMARY KEY     (       QueryPlanHash     ) );   As the definition of the query_plan_hash in sys.dm_exec_query_stats is a binary field (and I'll regularly be inserting new data), I was using VARBINARY for the data type in my new table.  However, the insert below fails...  INSERT INTO QueryPlans     ( QueryPlanHash, QueryPlan ) SELECT queryplanhash, queryplan FROM (     SELECT        p.value('(./@QueryPlanHash)[1]', 'varchar(20)') queryplanhash,       QueryPlan,       ROW_NUMBER() OVER (PARTITION BY p.value('(./@QueryPlanHash)[1]', 'varchar(20)') ORDER BY DateRecorded) rownum     FROM table     CROSS APPLY QueryPlan.nodes('/ShowPlanXML/BatchSequence/Batch/Statements/StmtSimple[@QueryPlanHash]') t(p) ) data WHERE rownum = 1   ....with the error  Implicit conversion from data type varchar to varbinary is not allowed. Use the CONVERT function to run this query.   The problem is that the query plan hashes are already in binary format, however stored as VARCHAR in the XML Query Plan e.g.  0x9473FBCCBC01AFE   and CONVERT to BINARY gives a completely different value  0x3078393437334642434342433031414645   I tried changing the value definition in the XQuery select to binary, but then it returned no values.  How would I extract the value of 0x9473FBCCBC01AFE from an XML query plan as a VARBINARY, rather than a VARCHAR?


Electromagnetic waves are photons or photons cause electromagnetic waves ? Its said that when charges are accelerated we get electric and magnetic field that carries energy but then they say that this energy is transferred in the form of photons so its confusing.

At the end of this nice video (), she says that  is a chain reaction of electric and magnetic fields creating each other so the chain of wave moves forward.  I wonder where the  is in this explanation. What is the relation between electromagnetic wave and photon?


My question is about OpenStreetMap place labels in QGIS, and how to keep them at a similar size when exported to as they appear in the software. I realise variations of this question have been asked before and it used to be an issue with the OpenLayers plugin but I have yet to find a workable solution.  I am having issues with losing the scale of labels of my backdrop mapping when exporting my QGIS print template to a PDF. I need the labels to maintain their size seen in both the map view (screenshot 1) and print template (screenshot 2). However when I export, the labels shrink to a unusable size (screenshot 3).         Does anyone know a work around to this issue?   I have found you can lower the DPI in the print template export setting which produces larger labels, however this also lowers the resolution of the map to a near unusable level.     Someone had similar problems:   However I have tried this solution (screenshot 4) and unfortunately I don't see any change in the label size to the output? (screenshot 5)      I am not sure if I am putting in this new parameter the URL correctly or not?

I am trying to export images from the QGIS print composer, the exported image has a basemap that is loaded from an XML file following . The export doesn't look at all like the image I see in the print composer see below and I'm trying to understand why.   What I'm trying to do is simply make a decent looking map without obvious tiling with readable labels. Perhaps I have to use a satellite only image and remake with my own labels. The map is a HERE nokia hybrid map   This is a jpeg at 150 dpi, note the tiny labels in comparison to the screenshot at the bottom .   This is a png export at 300 dpi, which is standard for the print composer, note the labels, and tiles.    Finally, this is a screenshot of the map as it looks in the print composer with the labels readable at this zoom scale.


here is my code:  <select id="List" name="UserType" onChange ="hide">        <option value="0" disabled="disabled" selected="selected">Tipo de Usuario</option>        <option value="1" onclick="hide">Administrador</option>        <option value="2" onclick="hide">Moderador</option>        <option value="3" onclick="hide">Usuario Comun</option> </select>   when i click some value (not zero) in the the drop down, i need remove the first item from this (Tipo de Usuario).  Some code in javascript able to do that?

How do I remove items from, or add items to, a select box? I'm running jQuery, should that make the task easier. Below is an example select box.  <select name="selectBox" id="selectBox">     <option value="option1">option1</option>     <option value="option2">option2</option>     <option value="option3">option3</option>     <option value="option4">option4</option>     </select>


-- Our Situation --  We haven't been able to get do-release-upgrade to run on our Ubuntu 16.04 LTS systems in the past few weeks.   We have 100+ machines to upgrade. Have read the other solutions and none of them work so far (eg:     ) - that is except for the "brute force" method of manually changing the distro in /etc/apt/sources.list[.d/]* .. I'm not a fan of this method as it seems overly messy and not particularly friendly.   Is do-release-upgrade broken on 16.04LTS ? do-release-upgrade worked sometime mid last year, and now it isn't..   -- Some info.. --  * Require a command line based solution as we need to automate this.   We will be updating over 100 machines * None of the existing solutions get do-release-upgrade to work.     sudo do-release-upgrade     sudo do-release-upgrade -d     sudo do-release-upgrade -c * update-manager-core package is installed * File /etc/update-manager/release-upgrades has:     [DEFAULT]     #...     Prompt=lts  * File /etc/update-manager/meta-release has:     # default location for the meta-release file     [METARELEASE]     URI = https://changelogs.ubuntu.com/meta-release     URI_LTS = https://changelogs.ubuntu.com/meta-release-lts     URI_UNSTABLE_POSTFIX = -development     URI_PROPOSED_POSTFIX = -proposed     /etc/update-manager/meta-release (END)   -- Error Messages --    do-release-upgrade :         Checking for a new Ubuntu release         No new release found.   do-release-upgrade -d :         Checking for a new Ubuntu release         Upgrades to the development release are only          available from the latest supported release.    do-release-upgrade -c :         Checking for a new Ubuntu release         No new release found.   UPDATE #1   * Machines are running : Ubuntu 16.04.6 LTS  * Machines are updated every day by cron (apt update+upgrade)  * /etc/apt/sources.list.d/ubuntu.list has :     deb archive.canonical.com/ubuntu xenial partner

There are now errors when updating and I cannot install most software due to a corrupted  /etc/apt/sources.list   file. Is there a copy I can download to replace it?  The file would be for Ubuntu 12.04 (Final Beta) in the United States.


"Orphaned cycles" may not be exactly the correct term for what I'm trying to describe.  Here is an example of what I'm trying to describe in code:  public class Container {     private Container otherContainer;     public void setContainer(Container otherContainer) {         this.otherContainer = otherContainer;     } }  public class Main {     public static void main(String[] args) {         doStuff();     }     public static void doStuff() {         Container c1 = new Container();         Container c2 = new Container();         c1.setContainer(c2);         c2.setContainer(c1);         //c1 and c2 now each hold a reference to each other,         //will they be garbage-collected once this method falls out of scope?     } }   Given a graph of references in memory containing a cycle, can the JVM garbage collect the memory references once the cycle is unreachable by code?  Or is this a memory leak?

Given an aggregation of class instances which refer to each other in a complex, circular, fashion: is it possible that the garbage collector may not be able to free these objects?  I vaguely recall this being an issue in the JVM in the past, but I thought this was resolved years ago.  yet, some investigation in jhat has revealed a circular reference being the reason for a memory leak that I am now faced with.  Note: I have always been under the impression that the JVM was capable of resolving circular references and freeing such "islands of garbage" from memory.  However, I am posing this question just to see if anyone has found any exceptions.


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


In forms, some uses only name as one  field and some uses first name, middle name and last name, separate field for all. It is increasing number of clicks also then why people use that.  Which practice is good?

I am entertaining the notion of a single field for name entry on our scheduling web app. I think this is an excellent case for a "forgiving format" to make it easy to enter their names quickly. I would label it and possibly put additional placeholder text guiding the user. Like this:    It's important to catch first and last name correctly because it gets saved in our contact database that we provide to our users. However, people could enter "Joe De Maggio" or "Dr. Chopra" or "Ms Sally Ann Mc Dumont". The possibilities are many.  Is this choice wise? Is the engineering worth the UX? Does anyone know a plugin that tackles this?


Edit: This is not a duplicate of the linked question since I am using explicit instantiation and only a specific type of member functions do not link (others do).  The following code compiles but doesn't link and I don't understand why. It is explicitly instantiating the Vector class to limit the number of possible arguments for T and therefore hides the definition of Vector<T> in a .cpp file.  // fwd_decl.hpp #pragma once template<typename T> struct Vector; // Forward declare Vector to be used in other headers  // Vector.hpp #pragma once #include "fwd_decl.hpp"  template<typename T> struct Vector {     template<typename U> // To allow for other types than T to be used     Vector operator+(const Vector<U> & other) const;     T x;     T y;      // more stuff.. };  // Vector.cpp #include "Vector.hpp" template<typename T> template<typename U> Vector<T> Vector<T>::operator+(const Vector<U> & other) const {     return { static_cast<T>(x + other.x), static_cast<T>(y + other.y) }; } template struct Vector<int>; // Explicitly instantiate Vector<T> with int  // main.cpp #include "Vector.hpp" int main() {     Vector<int> b = Vector<int>{ 2, 3 } + Vector<int>{ 4, 5 }; }   The error I'm getting is:  1>main.obj : error LNK2001: unresolved external symbol "public: struct Vector<int> __thiscall Vector<int>::operator+<int>(struct Vector<int> const &)const " (??$?HH@?$Vector@H@@QBE?AU0@ABU0@@Z)   I'm compiling with VC++ 17 in VS 15.9.4.  Note that calls to members of Vector<int> that are not function templates do link normally.

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


I wrote my code and i want return multiple values in :   public int[] getResult(){ return geneticAlgorithm(cost,profit,gens,turns,cmax);   but when i use this show me eror:  Exception in thread "AWT-EventQueue-0" java.lang.UnsatisfiedLinkError: knapsacproject.algorithm.geneticAlgorithm([I[IIII)[I at knapsacproject.algorithm.geneticAlgorithm(Native Method) at knapsacproject.algorithm.getResult(algorithm.java:39)   my code :   package knapsacproject; public class algorithm {   public native int [] geneticAlgorithm(int[] cost, int[] profit,int cmax, int gens, int turns);  static  { try {            System.load("C:/Users/Desktop/dp/KnapSacProject/src/knapsacproject/helo.dll");   System.out.println("loaded successfully"); } catch (Exception e){ e.printStackTrace();  }  }  protected int[] cost, profit, result;  protected int gens, turns, cmax;  public algorithm(int[] cost,int[] profit, int gens ,int turns , int cmax ) { this.cost=cost; this.profit=profit; this.gens=gens; this.turns=turns;   this.cmax=cmax;      }    public int[] getResult(){  return geneticAlgorithm(cost,profit,gens,turns,cmax);   }   public static void main (String[] args ) {      }   }   So How do I return multiple value or How do I fix this?

I want to return two objects from a Java method and was wondering what could be a good way of doing so?  The possible ways I can think of are: return a HashMap (since the two Objects are related) or return an ArrayList of Object objects.  To be more precise, the two objects I want to return are (a) List of objects and (b) comma separated names of the same.  I want to return these two Objects from one method because I dont want to iterate through the list of objects to get the comma separated names (which I can do in the same loop in this method).  Somehow, returning a HashMap does not look a very elegant way of doing so.


Part A is in the title, Part B is here: Is it true that $(k, n+k)= d$ if and only if $(k, n)=d$?  I am still working on the Part A.   What I have so far:  if $(k, n)= 1$ then $1|k$, $1|n$ and $1|(n-k)$  if $(k, n+k)=1$ then $1|k$, $1|n+k$ and $1|((n+k)- k) \to 1|n$  I was under the impression that if $d|a$ and $d|b$, that $d|(b-a)$.  Is this false? What more should I be doing to tackle part A?

(a) Prove $(k,n+k)=1$ iff $(k,n)=1$. (b) Is it true that $(k,n+k)=d$ iff $(k,n)=d$? (all variables are integers, (a,b) means gcd(a,b))  For (a), I can only get so far.  $(k,n+k)=1\ \Rightarrow\ kq_1+(n+k)q_2=k(q_1+q_2)+nq_2=1$.  Note that we don't yet have that theorem (from a different class) that says something like if $d=(a,b)$, then $d$ is the smallest (or is it biggest) number which can be made by $ak_1+bk_2$, (which I'm not quite sure how it would help, anyway). So I'm stuck.


I'm trying to find the orbits of the Frobenius homomorphism $\phi_p: a \to a^p$ on $\mathbb{F}_{p^4} / \mathbb{F}_p$. I can see there are $p$ 1 orbits corresponding to the action on $\mathbb{F}_p$ but I think there are also some order 2 and 4 orbits but I'm having trouble finding how many of each there are.  This is part of an argument on trying to show how many irreducible polynomials of degree 4 there are over $\mathbb{F}_p$ because I think this number should correspond to how many order 4 orbits there are, as then the polynomial with roots in that orbit should be irreducible.  Thanks

I know that for every $n\in\mathbb{N}$, $n\ge 1$, there exists $p(x)\in\mathbb{F}_p[x]$ s.t. $\deg p(x)=n$ and $p(x)$ is irreducible over $\mathbb{F}_p$.     I am interested in counting how many such $p(x)$ there exist (that is, given $n\in\mathbb{N}$, $n\ge 1$, how many irreducible polynomials of degree $n$ exist over $\mathbb{F}_p$).   I don't have a counting strategy and I don't expect a closed formula, but maybe we can find something like "there exist $X$ irreducible polynomials of degree $n$ where $X$ is the number of...".  What are your thoughts ?


I have an web server with CentOS 6.7 installed. Now I aqquired a new computer and want to make it to run the web server but it is hard to fresh install and copy all the content (hundreds of websites). Can I move the hdd from old server on the new server? And if something does not work can I switch the hdd Back? Is there any risk? Both are 32 bit systems. Thanks!

I know that it can, in some circumstances, be difficult to move a Windows installation from one computer to another (physically move the hard drive), but how does that work on linux? Aren't most of the driver modules loaded at bootup? So theoretically would it be that much of a hassle?  Obviously xorg configs would change and proprietary ATI drivers and such would have to be recompiled (maybe?). Is there more to it than I'm thinking of?  Assume the 2 computers are from the same era, ie both i7s but slightly different hardware.  Update: Thanks for the answers. This is mostly for my own curiosity. I have my linux system up and running at work, but eventually I'd like to move to a computer that I can get dual video cards into so I can run more than 2 monitors. But not any time soon


In my constructor, I have to initialize the _socket. But initializing the socket can throw an exception. How can I catch and process the exception ?  Thanks ! Here my code:   tftp_server::tftp_server(unsigned short port_number) : _socket(_io_service, udp::endpoint(udp::v4(), port_number)) {         //... }

Here's a curious one. I have a class A. It has an item of class B, which I want to initialize in the constructor of A using an initializer list, like so:  class A {     public:     A(const B& b): mB(b) { };      private:     B mB; };   Is there a way to catch exceptions that might be thrown by mB's copy-constructor while still using the initializer list method? Or would I have to initialize mB within the constructor's braces in order to have a try/catch?


I can show that $(x^m-1, x^n-1) \subseteq (x^{(m,n)} - 1)$, but I am stuck with the other inclusion. i.e. showing there exist polynomials $p, q \in \mathbb{Z}[X]$ such that $p(x)(x^m-1) + q(x)(x^n-1) = x^{(m,n)}-1$. I can't use Bezout's identity because $\mathbb{Z}[X]$ is not a PID. I computed some examples but I can't see a general patttern. e.g. \begin{align} (x^5-1) - (x^3 + x)(x^2-1) &= x-1 \\ (x^2-1)(x^5-1) -(x^4+x^2+x)(x^3-1) &= x-1 \\ (x^4-1) -x^2(x^2-1) &= x^2-1 \end{align} Thanks in advance.


I am doing a PhD and I have submitted an article to be peer-reviewed 9 months ago to a certain journal. I haven't got any response yet from the journal, their server indicates the "Under review" status.  The problem is, I cannot wait more longer since the acceptance of the article is a requirement to validate my PhD.  Do you think I can stop the reviewing process and send it to another journal? What if I sent it to another journal at the same time? Or, would the reviewing process speeds up if, e.g. I pay for the open access?  EDIT:  I forgot to mention that the status cited above stipulates that:     At least one Reviewer has accepted to review the submisѕion, however the required number of reviews for the submisѕion have not yet been received.   I have provided 5 names for the peer-reviewing process of my article, and mentioned that 1 potential reviewer from another university should not review it (because of competitive reasons).

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 have:         std::vector<std::unique_ptr<Zombie>> zombie;         for(unsigned j=0; j < zombie.size(); j++)         {                   if(bullet intersects zombie)               {                                zombie.erase(zombie.begin()+j)               }         }  I would like to delete specific object/s in vector of unique pointers. Above example works, but my lecturer said that this way doesn't guarantee that all proper objects will be deleted. I have spent  long time to figure it out somehow, but I don't have idea how to do it.

I want to clear a element from a vector using the erase method. But the problem here is that the element is not guaranteed to occur only once in the vector. It may be present multiple times and I need to clear all of them. My code is something like this:  void erase(std::vector<int>& myNumbers_in, int number_in) {     std::vector<int>::iterator iter = myNumbers_in.begin();     std::vector<int>::iterator endIter = myNumbers_in.end();     for(; iter != endIter; ++iter)     {         if(*iter == number_in)         {             myNumbers_in.erase(iter);         }     } }  int main(int argc, char* argv[]) {     std::vector<int> myNmbers;     for(int i = 0; i < 2; ++i)     {         myNmbers.push_back(i);         myNmbers.push_back(i);     }      erase(myNmbers, 1);      return 0; }   This code obviously crashes because I am changing the end of the vector while iterating through it. What is the best way to achieve this? I.e. is there any way to do this without iterating through the vector multiple times or creating one more copy of the vector?


I found an Omega Shield, it has no limit and a guy dropped it on multiplayer. It's a Tiadore and all I hear is an Atlas Omega Shield. It says Alpha and that other thing. I can keep all my items and any level can use it.  Is it hacked?

In a recent multiplayer game, one of my teammates dropped an odd shield the likes of which I'd never seen.  They stood there and kept shooting at it for awhile, so I presumed they meant for me to pick it up.  The shield card stats are below:   Name:  Ironclad Omega Manufacturer:  Pangolin Rarity:  Pearlescent Capacity:  214748 Recharge Delay:  10 Flavor Text:  I stand unvanquished!  The Alpha and that other thing. Value:  $9,999,999   When I equip the shield, however, my shield's maximum charge doesn't match the card's stats - it tops out at 2147483647!  Additionally, it seems the shield never actually depletes - no matter how many hits I take, it stays maxed.  I'm effectively invincible!  In the same multiplayer game, I noticed one team member (not sure if it was the same) was an "Omega" class.  So, this got me to thinking there might be more "Omega" type equipment to find.  Is there more equipment like this (weapons, grenade mods, COMs)?  Or did I just pick up someone's hacked shield?  If there is more, where and how can I find it?


I'm running Ubuntu 11.10 64-bit, and I cannot execute .run files. I get a message saying that there is no application installed to open the file.

My PC has both Ubuntu and Windows 7 installed. I have installed all my drivers in Windows like Nvidia graphics, motherboard etc. Shall I install them in Ubuntu too?  I looked on the web for my Nvidia drivers and I have found a .run file. How could I install it on my Ubuntu?


I am trying to upgrade from 18.10 to any possible version with the aim of ultimately getting to 20.04.  Any help or tips would be greatly appreciated.  I have tried the following so far:  Run the basic Update Manager in graphical and command line modes and got this error:  "An upgrade from 'cosmic' to 'eoan' is not supported with this tool".  (Eoan is 19.10) Tried playing with /var/lib/update-manager/meta-release to change paths but it looks like the underlying repositories have been removed Removed update manager and tried reinstalling per another URL and now i cannot reinstall that at all.  Is there anyone who can help please?  I would really really prefer not to wipe everything out and reinstall if possible.

I'm trying to upgrade from 18.10 to 19.10, using sudo do-release-upgrade however I only get an error: An upgrade from 'cosmic' to 'eoan' is not supported with this tool. I performed the steps to update my sources.list to point to old-release server, as suggested here:  This did not help. I get the same error.


Hi I executed this command sudo adduser username sudo and am wondering how do I take that username out from being able to execute sudo.  I checked the sudoers file but the username that I added thru the command line is not in there.  Does anyone know what command should I execute to take out the username? Thank you.

I added a user account to the admin group and discovered I added wrong user. So I now have to remove the account from the admin group.   How can I remove an account from a group without deleting the user?


I have been learning java recently and is using eclipse as IDE. But , I am not able to make a .exe file with that . all I get is jar file which I know can be executed on the window machine. My question is that can I use Visual studio and create .exe program or for that matter any software for Microsoft Windows using Java ?

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


I have a problem with getText() method. When I run this app and enter any number, also 9 it displays vcx. Is my if statement invalid or what?  public class Quadratic extends Fragment {  @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,         Bundle savedInstanceState) {     View rootView = inflater.inflate(R.layout.fragment_quadratic, container, false);        // layout     Button calc = (Button)rootView.findViewById(R.id.calcbtn); //main  button     final EditText etfx2 = (EditText)rootView.findViewById(R.id.etfx2); // x^2 etf      final TextView tbefs = (TextView)rootView.findViewById(R.id.tbefs);        calc.setOnClickListener(new View.OnClickListener()     {          public void onClick (View v){             String a= etfx2.getText().toString();               if(a=="9")             {                 tbefs.setText("asd");}             else             {                 tbefs.setText("vcx");             }           }      });     return rootView; }}

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


Suppose that $f: \mathbb{R^+}\to \mathbb{R}$ satisfies $\lim_{x\to \infty} (f+f')(x)=0$. Show that $\lim_{x\to \infty} f(x)=0$.  This is one solution I found to this problem.  Solution: If $x=a$ is in the domain of the function $f$, then by the generalized mean value theorem applied to the functions $e^x f(x)$ and $e^x$, there exists $c\in (a,x)$ such that $\frac{e^x f(x)-e^a f(a)}{e^x -e^a}=\frac{e^c f'(c)+e^c f(c)}{e^c}.$ This yields $\frac{e^x}{e^x -e^a} f(x)-\frac{e^a}{e^x - e^a}f(a)=f'(c)+f(c)$. Taking limits as $c$ tends to infinity we have,  $\lim_{c\to \infty}\frac{e^x}{e^x -e^a} \lim_{c\to \infty}f(x)-\lim_{c\to \infty}\frac{e^a}{e^x - e^a}\lim_{c\to \infty}f(a)=\lim_{c\to \infty}[f'(c)+f(c)]$. But $c\lt x$, thus we obtain $1 \cdot \lim_{x\to \infty}f(x)-0\cdot f(a)=\lim_{c\to \infty}[f'(c)+f(c)].$ Hence, since the right hand side is equal to $0$, it follows that $\lim_{x\to \infty}f(x)=0.$  Taking a close look at this solution, however, I think it may not be correct since the $c$ used in the answer is actually a function of $x$ and it may not make sense to take $c\to \infty$. I mean how do we know that there will always be such a $c$ greater than any given positive number? Is this solution correct? If so, how can my question be answered? I would greatly appreciate any help.

If $$\lim_{x\to\infty}(f(x)+f'(x))=l$$ then prove that $$\lim_{x\to\infty}f(x)=l \text{ and } \lim_{x\to\infty}f'(x)=0 $$    I assume four cases $$\begin{array}{c|c|c|c|}   & f(x) & f'(x) \\ \hline \text{1} & \infty & -\infty \\ \hline \text{2} & -\infty & \infty \\ \hline \text{3} & l & 0 \\ \hline \text{4} & 0 & l \\ \hline \end{array}$$ and elimination(1,2,4) of not possible cases can give the answer(3).    My work is not a correct/perfect or flaw proof.What would be a correct one or is this correct.


I have values in a column named Date as a nvarachar data type in the form of mmddyy and want to convert the values to a date datatype in the form of yyyy-mm-dd. What sql colde can I use to convert the value? example 02121955 -> 1955-02-12

I have a CSV file that has dates written like this: 250909,240909 and they get stored in a SQL Server database as varchars.  How do I get it to convert them into dates so that it gets displayed like this: 25/09/09, using the dd/mm/yyyy format?  At the moment I can get it to convert, but it converts it like this: 2025/09/09, meaning it is using the yyyy/mm/dd format which is wrong, seeing that the first column is the day and second the month and third the year.


In the , the Homunculus's hit points are given as:     Hit Points equal to five times your level in this class + your Intelligence modifier   Is this calculated as \$(5\times level) + {Int Mod}\$ or \$5\times (level + {int mod})\$?

An abjuration wizard's Arcane Ward states:     [...] The ward has hit points equal to twice your wizard level + your Intelligence modifier.   So how many hit points is this supposed to be?  \$ (2 \times WizardLevel) + INT_{mod}\$  or  \$2 \times (WizardLevel + INT_{mod})\$ ?  I feel like the phrasing hints toward the first calculation, but it's still somewhat ambiguous.


I am confused between the gravitational pull and the air friction on the moon. Let me give you an example,  I have learned that the greater the mass of the body the more gravitational force it generates.  The other point is, On the moon, there is no  air friction so if we drop a feather and a hammer, both will reach the surface simultaneously.  My question is, The mass of the Hammer is clearly more than that of feather. Shouldn't it be pulled toward Moon faster than the feather due to greater gravitational pull?  How come, the gravitational pull be constant from the moon for all the object regardless of their mass?

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


I'm new to blender, and am working on a large "cyberpunk" skyscraper that needs a ton of windows. I applied some basic materials nodes that randomized the emission values to each window as a separate object, which works great.    However, the problem is that the picture shown is only a small fraction of the building, and when I'm putting the parts of the building together, the object count is reaching the thousands, and my computer slows to a crawl. Is there possibly an alternative to randomize whether each window is on or off that will remain once I combine them into a single object, or at least in bigger pieces? Maybe have each window be randomly assigned one of two materials? Any help would be greatly appreciated!

I am trying to get color variation and to bake it in a single mesh but the Object Info Random only works if i separate the meshes. Is there an alternative way to get the same result with the meshes combined, they aren't attached between them.


Is there something intrinsic about the structure of space that gravity is proportional to 1/r^2 instead of, for example,  1/r^2.143 ?  What makes the exponent turn out to be a nice even number?

When I was in the university (in the late 90s, circa 1995) I was told there had been research investigating the $2$ (the square of distance) in the Newton's law of universal gravitation.  $$F=G\frac{m_1m_2}{r^2}.$$  Maybe a model like   $$F=G\frac{m_1m_2}{r^a}$$  with $a$ slightly different from $2$, let say $1.999$ or $2.001$, fits some experimental data better?  Is that really true? Or did I misunderstand something?


I have multiple folders and each one have around 175 files in it.  file names are like   1.wav 2.wav 3.wav ...... 175.wav    I have to rename them as   A1.wav A2.wav A3.wav ...... A175.wav    In other words I have to append Letters in previous file names.   I am wondering if there is a easy way to do this.    Ubuntu Version is 16.10

One of the ways I quickly rename files in Windows is   F2 > Rename > Tab (to next file) > Rename ...   But in Ubuntu/Nautilus, I can't tab to next file. But being on Linux, I think there must be a command line alternative.  However, sometimes, I may want more control over how to rename specific files. In that case, perhaps its better to be able to tab to the next file


I'm learning c# and on many MSDN pages related to c# I came across the terms like O(n) log of O(n). for e.g.     in Remarks there is statement as" This method is an O(n) operation, where n is Count."   My Query -> I want to know what does general meaning of O(n) operation here, and what are the resources to know more about this notation?

I'd prefer as little formal definition as possible and simple mathematics.


I know that $|p(\mathbb{N})|>|\mathbb{N}|$, and that $|\mathbb{R}|>|\mathbb{N}|$, and I wonder whether $|p(\mathbb{N})|>|\mathbb{R}|$ or not.  What I tried so far: I found the function from $\mathbb{R}$ to $p(\mathbb{Q})$ defined by $f(x)=\{q\in \mathbb{Q}|q<x\}$, which I am quite sure to be injective function, but not onto. As $|\mathbb{Q}|=|\mathbb{N}|$, also $|p(\mathbb{Q})|=|p(\mathbb{N})|$, so I inferred that $|p(\mathbb{N})|\ge |\mathbb{R}|$. But are they equal?  In this, $p(A)$ is the power set of A, denoted also by $2^A$ and defined as is the set of all subsets of A.

Is $2^{|\mathbb{N}|} = |\mathbb{R}|$? If so, how?  I was reading the Wiki page on the , and it says "Moreover, $\mathbb{R}$ has the same number of elements as the power set of $\mathbb{N}$", but I don't see how this is true?  I feel like it has something to do with binary, but I'm not too sure how it works? Do I have to show a map of all reals can be done in binary? I'm just very confused, and any advice would be appreciated!


In the photoelectric effect, a light ray of sufficient wavelength causes electrons to be released from metal surfaces. By what process do photons do that?  In my textbook, I have seen that  the photon transfers it's whole energy to the electron as a part of elastic collision and so the electron receives the whole energy and comes out.  But I want to know how does a photon transfers energy and how does the electron comes out?

It's a common understanding that atoms emit or absorb light when the energy of the photons is equal to the the difference in the energy levels in the atom. What I don't understand is how does an electron absorb light inside an atom? Is it that the atom as a whole absorbs light or the individual electrons absorb the light packets? Also I would like to know, what does one mean when you say that an electron absorbs photon. How does an electron absorb a photon??