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Harry takes the Hogwarts Express to get to school all the six years when he's attending Hogwarts (with the exception of his second year, of course; but he was trying to get on it) and boards the train from platform 9¾. Are there any wizarding trains other than the Hogwarts Express, and are there any platforms other than 9 ¾ that witches and wizards can take from King's Cross to their world? | In the Pottermore article on it's mentioned that other fractional platforms exist (7 1/2, for instance). Is it ever stated elsewhere where these platforms lead? Perhaps you could get a connection from your hometown by accessing one of these platforms? |
If I were given $\lim_{n\to \infty}(1 + \frac{1}{n})^n$, and asked to solve, I would do so as follows: $$\lim_{n\to \infty}(1 + \frac{1}{n})^n$$ $$=(1 + \frac{1}{\infty})^\infty$$ $$=(1 + 0)^\infty$$ $$=1^\infty$$ $$=1$$ I'm aware that this limit is meant to equal to $e$, and so I ask: why don't I get $e$ when I solve $\lim_{n\to \infty}(1 + \frac{1}{n})^n$? | I am trying to identify what the flaw is exactly when reasoning about a limit such as the definition of $\mathbf e$: $$ \lim_{n\rightarrow \infty}\left(1+\frac{1}{n}\right)^n={e} $$ Now, I know there are ways of proving this limit, such as by considering the binomial expansion of $(1+\frac{1}{n})^n$ and comparing that to the Maclaurin series of $e$. So to make this clear, I am not looking for a proof of the limit definition of $e$. I tried searching for "limit laws/rules" but none of the rules I found described the above case. Hence, I am looking for a specific rule (or perhaps a certain perspective) that will help me realize why the above does not in fact evaluate to 1. My train of thought is as follows: at a first glance, if I wasn't already familiar with what the limit evaluates to, I probably would evaluate the expression inside the brackets first, and then apply the limit to the power. So, $$\displaystyle\lim_{n\to\infty}\frac{1}{n}=0\quad\text{and then}$$ $$\displaystyle\lim_{n\rightarrow \infty}\left(1+0\right)^n=\lim_{n\to\infty}1^n=1$$ Why is my reasoning flawed? |
Let $\alpha,\gamma$ be ordinals and $A$ be a set of ordinals. Then $$\gamma<\alpha+\sup\limits_{\beta\in A}\beta\implies\exists\beta\in A:\gamma<\alpha+\beta$$ This problem arises when I prove the theorem: Let $\alpha,\beta$ be ordinals and $A$ be a set of ordinal. Then $\sup\limits_{\beta\in A}(\alpha+\beta)=\alpha+\sup\limits_{\beta\in A}(\beta)$ I'm almost done except for one minor point: $\gamma<\alpha+\sup_\limits{\beta\in A}\beta\implies\exists\beta\in A:\gamma<\alpha+\beta$. This result seems quite obvious, but I don't know how to prove in spite of several attempts. Could you please shed me some lights on how to prove $\gamma<\alpha+\sup\limits_{\beta\in A}\beta\implies\exists\beta\in A:\gamma<\alpha+\beta$? Thank you very much! | My idea is to prove that $\alpha+ \sup\limits_{β∈A}(β)$ is the supremum of $\{α+β\mid β∈A\}$. While I'm able to prove that $\alpha+ \sup\limits_{β∈A}(β)$ is a upper bound of $\{α+β\mid β∈A\}$, I failed to show that $\alpha+ \sup\limits_{β∈A}(β)\le\gamma$ where $\gamma$ is an upper bound of $\{α+β\mid β∈A\}$. The addition of ordinals is defined as follows $\alpha+0=\alpha$, $\alpha+(\beta+1)=(\alpha+\beta)+1$, and $\alpha+\beta=\sup\limits_{\gamma<\beta}(\alpha+\gamma)$ if $\beta$ is limit. My attempt: For all $\beta\in A,\beta\le\sup\limits_{β∈A}(β)$, then $\alpha+\beta\le\alpha+ \sup\limits_{β∈A}(β)$ and thus $\alpha+ \sup\limits_{β∈A}(β)$ is a upper bound of $\{α+β\mid β∈A\}$. Assume that $\gamma$ is an upper bound of $\{α+β\mid β∈A\}$, then $α+β\le\gamma$ for all $β∈A$. My questions: Please leave me some hints to complete my proof! I meet another proof of this theorem on the Internet: Could you please elaborate on the sentence Since set inclusion is the ordering, the two are equal. I'm unable to understand what this sentence means. Thank you so much for your help! For an ordinal $α$ and a set $A$ of ordinals: $\sup\limits_{β∈A} (α+β) = α+\sup\limits_{β∈A}(β)$ $\sup\limits_{β∈A} (α\cdot β)=α\cdot \sup\limits_{β∈A}(β)$ |
Suppose that $P_1$ and $P_2$ are coprime between them in $\mathbb{K}[X]$. Show that $$ \ker ( (P_1 \times P_2 )(f) )=\ker(P_1 (f)) \oplus \ker(P_2(f)).$$ I tried by starting off by showing that the right hand equality is true, that is $\mathbb{K}[X]$ is indeed equal to $\ker(P_1 (f)) \oplus \ker(P_2(f))$. My first attempt was to show that $$\ker(P_1 (f)) \cap \ker(P_2(f))= \{ 0 \} .$$ But I got nowhere. I think I could have used the Bezout theoreme, that is: If $P_1$ and $P_2$ are coprime, then $\exists U,V \in \mathbb{K}[X]$ so that $P_1U(X) + P_2V(X)=1$ But nothing comes to my mind. | I have a question related to the Primary Decomposition Theorem for a vector space under a linear transformation. The following question is a direct corollary of this theorem. However, I wish to prove it without calling upon theorem. I am currently studying for a comprehensive exam and ran across this question. I never really felt comfortable with the proof I saw of the Primary Decomposition Theorem so I hoping with your help with this problem I will understand this particular problem and better understand that proof as I believe their proofs will be essentially the same techniques. Question: Suppose we have a linear transformation $T: \mathbb{R^n}\to \mathbb{R^n}$ with minimal polynomial $m(x)=f(x)g(x)$ and $f(x),g(x)$ are relatively prime. Show that we can write $\mathbb{R^n}=M\oplus N$ where $M$ and $N$ are $T$-invariant subspaces s.t $f(x)$ is the minimal polynomial for $T|_M$ and $g(x)$ is the minimal polynomial for $T|_N$. So I know that I want to use $M=ker(f(T))$ and $N=ker(g(T))$ but after that I really don't have much. Since this isn't a homework problem for a class I am essentially looking for someone to present me a proof of this simpler question and walk me through their logic so that I can hopefully understand the general theorem and its proof. Thanks in advance for the help! |
In order to remind myself when I try to use shopt in Zsh instead of setopt, I created the following alias, testing it first at a shell prompt: $ alias shopt='echo "You\'re looking for setopt. This is Z shell, man, not Bash."' Despite the outer single quotes matching and the inner double quotes matching, and the apostrophe being escaped, I was prompted to finish closing the quotes with: dquote > _ What's going on? It appeared that the escaping was being ignored, or that it needed to be double-escaped because of multiple levels of interpretation... So, just to test this theory, I tried double-escaping it (and triple-escaping it, and so on) all the way up until: alias shopt='echo "You\\\\\\\\\\\\\\\\\\\\\\'re looking for setopt. This is Z shell, man, not Bash." ' and never saw any different behavior. This makes no sense to me. What kind of weird voodoo is preventing the shell from behaving as I expect? The practical solution is to not use quotes for echo, since it doesn't really need any, and to use double quotes for alias, and to escape the apostrophe so it is ignored when the text is echoed. Then all of the practical problems go away. Can you help me? I need resolution to this perplexing problem. | I recently learned about , but am having trouble making it work with relatively sophisticated commands. For example, I would like to ask watch to run the following command on zsh every three seconds*: for x in `command_1 | grep keyword | cut -d' ' -f1`; do command_2 "word[word=number]" $x; done as you can see the line above includes single quotes, double quotes, among other special characters. So I tried: watch -n 3 "for x in `my_command | grep keyword | cut -d' ' -f1`; do command2 "rusage[mem=7000]" $x; done" but then I got: no matches found for x in !@#$# ....; done I tried other combinations without success. Here's one of those attempts: watch -n 3 "for x in $(bjobs -w | grep pre_seg | cut -d' ' -f1); do bmod -R "rusage[mem=7000]" $x; done" which also results in a similar error. Any ideas how to make this work? *I would also be intersted in solutions that work on bash |
I have a program written in C#, console application. A .exe file is created and when executing the command window opens, writes the output and closes as usual. My problem is that I may need to see the output in the cmd (not always). Is there any command (as I call my exe file through cmd in order not to close the command prompt that specific time only)?? | My problem is that in Windows, there are command line windows that close immediately after execution. To solve this, I want the default behavior to be that the window is kept open. Normally, this behavior can be avoided with three methods that come to my mind: Putting a pause line after batch programs to prompt the user to press a key before exiting Running these batch files or other command line manipulating tools (even service starting, restarting, etc. with net start xy or anything similar) within cmd.exe(Start - Run - cmd.exe) Running these programs with cmd /k like this: cmd /k myprogram.bat But there are some other cases in which the user: Runs the program the first time and doesn't know that the given program will run in Command Prompt (Windows Command Processor) e.g. when running a shortcut from Start menu (or from somewhere else), OR Finds it a little bit uncomfortable to run cmd.exe all the time and doesn't have the time/opportunity to rewrite the code of these commands everywhere to put a pause after them or avoid exiting explicitly. I've read about changing default behavior of cmd.exe when opening it explicitly, with creating an and manipulating its content in these locations: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Command Processor\AutoRun HKEY_CURRENT_USER\SOFTWARE\Microsoft\Command Processor\AutoRun (The AutoRun items are _String values_...) I put cmd /d /k as a value of it to give it a try, but this didn't change the behaviour of the stuffs mentioned above at all... It just changed the behaviour of the command line window when opening it explicitly (Start-Run-cmd.exe). So how does it work? Can you give me any ideas to solve this problem? |
Sorry, I know this is probably simple and covered in another post but I couldn't find it so: I want to iterate through two lists and then store a result in an array based on the position of the inputs. So, for example: z = np.array(len(xlist), len(ylist)) for x in xlist: for y in ylist: z[index of x, index of y] = f(x,y) Thanks! | How do I access the index in a for loop like the following? ints = [8, 23, 45, 12, 78] for i in ints: print('item #{} = {}'.format(???, i)) I want to get this output: item #1 = 8 item #2 = 23 item #3 = 45 item #4 = 12 item #5 = 78 When I loop through it using a for loop, how do I access the loop index, from 1 to 5 in this case? |
I am looking for a way to quickly switch between keyboard apps while using gboard. My phone is a redmi 5. For e.g if I am writing a message I prefer gboard. But when I have to write code I want to quickly switch to hackers keyboard app. Incidentally on the latter I have the option to jump back to gboard... I want to be sure that there is no option on gboard to do the same. | I have two languages on Gboard and when I want to switch between them, I have to press the globe button. Is there anyway to switch language by swiping spacebar? I've seen this feature on Samsung Keyboard and I was wondering if it's available on the new Gboard. |
I heard that $e$ can be defined as the limit as n approaches infinity of $(1 + 1/n)^n$, but I also heard that $e$ is also defined as the sum of the reciprocals of the factorials from $0$ to $\infty$. How are these the same? | How can it be proved that the Euler constant equals the limit of the sum of all $\frac{1}{k!}$ when $k$ goes from $0$ to $+\infty$ ? |
I don't know why the following program is generating this error-> clone has protected access in Object. Can't the derived class access the protected methods of the Object class? If I skip this statement cloned.id=(String)id.clone(); the program compiles successfully! class Example implements Cloneable{ String id; void display(){ System.out.println("ID="+id); } public Example clone() throws CloneNotSupportedException{ Example cloned; cloned=(Example)super.clone(); cloned.id=(String)id.clone(); //troublemaker return cloned; } } class CloneInterface{ public static void main(String args[]){ try { Example e1=new Example(); e1.id="a"; Example e2=e1.clone(); e2.id="b"; e1.display(); e2.display(); } catch(CloneNotSupportedException e) { e.printStackTrace(); } } } | The keyword protected grants access to classes in the same package and subclasses (). Now, every class has java.lang.Object as superclass (). Hence I conclude that every class may access java.lang.Object's methods even if they are protected. Take a look at the following example: public class Testclass { public Object getOne() throws CloneNotSupportedException { return this.clone(); } public Object getTwo() throws CloneNotSupportedException { return ((Object) this).clone(); } } While getOne() compiles fine, getTwo() gives Testclass.java:6: clone() has protected access in java.lang.Object return ((Object) this).clone(); I neither understand why getTwo() doesn't compile nor what's the difference (regarding the access of java.lang.Objects members) with getOne(). |
I've heard of certain properties being attributed to things such as dragon tears and scales, are there any established properties for dragon bones in crafting or other applications? | My party recently acquired some dragon bones. We split up the skeleton. I got the head and neck. One got the ribs and front legs. One got the wings and feet and one got the back legs and tail. I bought the rib cage for 125 gp. I don't know if that was a good idea but I did it. I want to know how I can use the neck bones, skull, and ribs. Can anyone tell me what to do in this situation? Someone once suggested I use the ribs to reinforce my shield, but I don't know if that's allowed by the rules. What are the guidelines around what can be done with dragon bones? I know I can just use them for cool decorations, but is there any rules support from getting any kind of benefit out of them? |
I was playing around with the family of sequences $s(x)$ defined for $x > 0$ as $s(x)_0 = x$, $s(x)_{n+1} = \log(1+s(x)_n)$ and I noticed a strange behavior. Specifically, regardless of the choice of $x$, $s(x)_{10^n} \approx 2\cdot 10^{-n}$ as $n$ grows: > let logs x = x : logs (log (1 + x)) > logs 1000 !! 1000 2.0066131337990703e-3 > logs 1000 !! 10000 2.0008131530487204e-4 > logs 1000 !! 100000 2.0000966401761077e-5 > logs 1000 !! 1000000 2.000011198587142e-6 Based on this observation, I am wondering whether $n s(x)_n \rightarrow 2$ for all $x > 1$ and if so, why. | Suppose $x_{1}>0$, and consider the sequence, $\{x_{n}\}$ defined as follows: $$x_{n+1}=\log(1+x_{n}) \quad n\geq 1 $$ Find the value of $\displaystyle \lim_{n \to \infty} nx_{n}$ I am having trouble solving it. One thing is clear, that since $x_{n}>0$ and $x_{n+1} < x_{n}$, we can have a sequence which converges an $f$ which satisfies $f=\log(1+f)$, so that $f=0$. Any way as to how we can proceed from here. |
Let a Pythagorean triple $(\xi,n,\zeta)$.Prove that at least one of $\xi,n$ is divided by $3$ and that at least one of $\xi,n, \zeta$ is divided by $5$. That's what I have thought: We suppose that : 1)$\xi=3n+1 \text{ and } n=3m+1$ 2)$\xi=3n+1 \text{ and }n=3m+2$ 3) $\xi=3n+2 \text{ and } n=3m+2$ and we show that at no of the above cases it is possible that $\xi^2+n^2=\zeta^2\text{ ,because the remainders will be } 2,8,9, \text{ but the only possible remainders that can give } n^2,\text{ divided by } 9, \text{ are } 0,1, \text{ so it is a contradicton.} $ Similarly,we can show that at least one of $\xi,n, \zeta$ must be divisible by $5$. Is the way I thought right?? Is there also an other way? | Show that if $x$, $y$, $z$ are integers such that $x^2 + y^2 = z^2$, then at least one of them is divisible by $2$, at least one is divisible by $3$, and at least one is divisible by $5$. I know that $x,y,z$ are sides of a right-angled triangles. If I start putting values, then I can show, but have no clue about mathematical approach. How do I solve it mathematically, using modular arithmetic? |
The Chancellor undoubtably did some really evil things (and/or made Vader do them) after the scene in question, but given only what happened leading up to this scene I wonder if Windu was in violation of the Jedi code or laws of the Republic by trying to kill Chancellor Palpatine. Chancellor Palpatine was the freely elected leader of the Republic (he was elected to office and his term was extended by a democratic vote). If he had killed anyone or broken any laws, I don't think evidence of that was shown to the viewer, or at least not to Windu, yet Windu: trespassed onto his private property, decided to "arrest" him based on an unsubstantiated rumor that he used "the dark side" (which I have a hard time imagining was against any law anyway), horribly disfigured the elderly man and subsequently decided that Palpatine was "too dangerous to let live" after he defended himself. He attempted to kill Palpatine as he lay writhing in pain and begging for his life. I can understand that this was done to help humanize Anakin's decision to save the Chancellor, but I can't see how Master Windu was representing "good" and the Chancellor or Anakin "evil". It seems like Windu was acting criminally and attempting to commit murder (?). I don't see how Anakin's protection of the Chancellor or the Chancellor's self-defense could be considered evil or unethical. | If the Jedi Order had arrested Palpatine, would the court have declared Palpatine guilty quickly based on proof that he was a Sith? Is there any rule stating that? Notes: The word quickly is important because finding proof of his political crimes would be difficult and time-consuming (it could take decades). I am assuming that the Jedi can prove that Palpatine is a Sith (e.g., using a security hologram of his conversation with Anakin, in which Palpatine declares that he is one). For this question, I am also removing all of Palpatine’s murders of Jedi from the equation. Update: This is a generic question about any Sith, not just Palpatine. In other words, could a Sith introduce himself to the Republic to have a peaceful life demanding protection from the Jedi if the case arises? |
Does anyone know how to find the exact sum of $$ \sum_{n = 1}^{\infty} \frac{(-1)^{n + 1}}{n} $$ I've only taken second semester calculus and don't see how to go about computing this sum. The only way that I know how to find the sum of an infinite series is if it is a geometric series. Using WolframAlpha, I found that the sum for this series is $\log(2)$. | I know that the harmonic series $$\sum_{k=1}^{\infty}\frac{1}{k} = \frac{1}{1} + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \frac{1}{6} + \cdots + \frac{1}{n} + \cdots \tag{I}$$ diverges, but what about the alternating harmonic series $$\sum_{k=1}^{\infty}\frac{(-1)^{k+1}}{k} = \frac{1}{1} - \frac{1}{2} + \frac{1}{3} - \frac{1}{4} + \frac{1}{5} - \frac{1}{6} + \cdots + \frac{(-1)^{n+1}}{n} + \cdots \text{?} \tag{II}$$ Does it converge? If so, what is its sum? |
Have $(U,V)$ be a pair of Bivariate Gaussian variables with mean $0$, variance $1$ and $Cov(U,V) = ρ$ where $0 < ρ < 1$ I'd like help finding the density of $U+V$ So far I have tried to use $P(U+V<=t) = E(P(U+V<=t | V))$ but a am not having much success in advancing. Any help would be appreciated. Note: This is not a homework problem, but a problem I am doing to help study. | Suppose $x_1\sim\mathcal N(2,0.5),x_2\sim \mathcal N(2,3),$ and $x_3\sim \mathcal N(2.5,7)$ with correlations $\rho_{(1,2)}=0.3,\rho_{(1,3)}=0.1,$and $\rho_{(2,3)}=0.4.$ What is the distribution of $x_1+x_2+x_3?$ $x_1+ (3\times x_2)+x_3?$ $x_1+x_2+(0.5\times x_3)?$ Solutions: The distribution of $x_1+x_2+x_3 =\mathcal{N}(6.5,15.275)$. The distribution of $x_1+(3\times x_2)+x_3=\mathcal{N}(10.5,30.077)$ The distribution of $x_1+x_2+(0.5\times x_3)=\mathcal{N}(5.25,8.005)$ But I want to know what is the distribution of $(2\times x_1)-(3\times x_2)-x_3$ and $x_1+x_2-(2\times x_3)?$ The distribution of $(2\times x_1)-(3\times x_2)-x_3$ is $\mathcal{N}(-4.5,41.8407).$ The distribution of $x_1 +x_2-(2\times x_3) $ is $\mathcal{N}(-1,24.1544)$ |
Bender Rodriguez. The lovable robot with a SERIOUS alcohol problem. One thing always perplexed me, though. How does he store everything? How did he get all these treasures? He stored them in his abdomen for years on end. But many of these riches are far larger than his midsection (see the bender to the right, one row back, and the bender one back and one toward the center of the pirate). And we see him do this with his majestic midriff multiple times throughout the series. But how is this terrific thorax possible? In- and Out-Of-World explanations welcome. | Bender often pulls large objects from his torso cupboard, but how deep or how much empty space is he capable of storing? Can he bend space around the perimeters of the frame of his torso's door? If that is the case, does it also bend time? I suppose he might bend in more ways than one... |
I have set of linux folders and I need to get the permissions of the folders numerically. For example in the below directory, I need to what is the permission value of the folder... Whether 755, 644 or 622 etc... drwxrwsr-x 2 dev puser 4096 Jul 7 2014 fonts | In FreeBSD and also in Linux, how can I get the numerical chmod value of a file? For example, 644 instead of -rw-r--r--? I need an automatic way for a Bash script. |
I have a chat client that launches another window when '.play' is sent in. The relevant code follows: BoardFrame bframe = new BoardFrame(); bframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); bframe.setSize(300,600); frame.setVisible(false); bframe.setVisible(true); BoardPanel bpanel = new BoardPanel(); bpanel.setSize(200,500); bpanel.setOrientation('v'); bpanel.setBackground(Color.GREEN); bpanel.paintComponent(bpanel.getGraphics()); bpanel.setVisible(true); bframe.getContentPane().add(bpanel,"Center"); bframe.pack(); BoardPanel is a class that extends JPanel and BoardFrame is a class that extends JFrame. Frame will be deleted, but for now i just set it to not visible. I just dont want to go messing around in those other classes if the solution is a quick one here. Also this is my first post on here so please forgive the hideous formatting. | What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them? What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely? |
Does anyone know the story about an astronaut stranded on an alien planet who discovers an alien habitat or some sort, that slowly transforms him into an alien being in order to survive its toxic atmosphere and to enable him to take in the alien food? | This is a story that was read on BBC radio about thirty years ago, and this is about as right as I can remember it: The human pilot of a spacecraft is doing some reconnaissance on an alien planet. He crashes but survives. For some reason, no one will know where to look for him. He sees something in the distance that looks like a building of some sort. When he gets there, it seems to be a home. Very much like a human home. There's furniture, but it's strange and uncomfortable . There's food, but it's inedible. There's a faucet but what comes out of it seems more like acid. Everything looks as though it should be right, but it's not. He leaves the house, wanders and after a few days is desperate for water. But there isn't any water anywhere. He's close to death, crawling on the ground and then something happens. There are cracks in the soil and there appears to be water bubbling up from perhaps some underground stream. The water revives him. He goes back to the house and tries the food again. It's delicious and he eats enough to gain back his strength. Then he decides to try the water again. It's pure and wonderful. He takes a shower and the last line of the story is how refreshing the water is on his skin and something about him lifting his tail. |
Is it something like they are by default added to every directory created to facilitate movement outside? | when I used ls -a to view hidden files in folder there were 2 hidden files created by default what is the significance of this two files . and ..? ls -a Produces . .. |
Is there a way of taking a snapchat filter off a saved image? Its a leopard nose and ears and would like to know if i can get them off or if any one else could? | I took a great picture of the sky the other day but it was on snapchat and i covered a tree by painting yellow streaks over it on the snap, that's the only pic I saved to my phone but I wanted to know if there was a way to remove the yellow streaking? can it be done with an online program? thanks |
Higgs Boson detected at LHC is massive. It has high relativistic mass means it has non-zero rest mass. Higgs Boson gives other things rest mass. But, how does it get rest mass by itself? | If the Higgs field gives mass to particles, and the Higgs boson itself has mass, does this mean there is some kind of self-interaction? Also, does the Higgs Boson have zero rest mass and so move at light-speed? |
What is the rule should the Goalkeeper save the penalty, (as in a case I experienced), the ref blows his whistle then the ball which went away from goal had some backspin on it and slowly proceeded to make its way into the net while the keeper was celebrating winning the shoot out with his team. Objections from the opposing Manager resulted in the kick being taken again and this time they scored and we went from winning to losing the shot out. Anyone know what should have happened? | If, during kicks from the penalty mark, the ball hits the goalpost and lobs outside the penalty area and then returns back into the goal without touching any player, will it be considered a goal or not? Please provide a reference to IFAB laws if possible. |
I have a label that I want to center in the page and I have a parent set to 100% width and the actual element set to a block display and the margin set to auto. If I set the element's width to a small value then it does actually center it, however the element stays static as I resize the window when I want it to adapt to the window size. The element I want to center is under the class "label_" .container { display: block; width: 100%; } .label_ { border: 1px solid red; display: block; color: white; z-index: 11; margin: 0 auto; font-family: "Handlee"; font-size: 50px; } <form> <div class="container"> <label class="label_" for="username">Username</label> <input id="username" type="text" placeholder="Username"> </div> </form> <div class="background"> <img src="background.png" alt=""> </div> <div class="logo"> <img id="amongus" src="amongus.png" alt=""> </div> <div class="red"> <img id="red" src="an871k4o1sn51.png" alt=""> </div> | How can I horizontally center a <div> within another <div> using CSS? <div id="outer"> <div id="inner">Foo foo</div> </div> |
I am trying to add/replace an i element on the i-th list of a list, however, only the last iteration is saved. It would be great to understand why this happens and what a workaround this would be. I'm interested in an output that looks like this: [[[0], [], [], []], [[1], [], [], []], [[2], [], [], []], [[3], [], [], []]], but instead I get this: [[[3], [], [], []], [[3], [], [], []], [[3], [], [], []], [[3], [], [], []]] matrix = [ [ [] * 4] * 4] * 4 print('pre_matrix=',matrix) for m in range(len(a) + 1): matrix[m][0] = [m] print('m={}, matrix[m]={}'.format(m, matrix[m])) print('post_matrix=', matrix) # This is what the response looks like: # pre_matrix= [[[], [], [], []], # [[], [], [], []], # [[], [], [], []], # [[], [], [], []]] # # m=0, matrix[m]=[[0], [], [], []] # m=1, matrix[m]=[[1], [], [], []] # m=2, matrix[m]=[[2], [], [], []] # m=3, matrix[m]=[[3], [], [], []] # # post_matrix= [[[3], [], [], []], # [[3], [], [], []], # [[3], [], [], []], # [[3], [], [], []]] | I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3 The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]] Then I changed one of the innermost values: my_list[0][0] = 5 Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]] which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it? |
Intuitively how does the LASSO method select its variables? Is it based on standard econometrics? | I've been reading , and I would like to know why the Lasso provides variable selection and ridge regression doesn't. Both methods minimize the residual sum of squares and have a constraint on the possible values of the parameters $\beta$. For the Lasso, the constraint is $||\beta||_1 \le t$, whereas for ridge it is $||\beta||_2 \le t$, for some $t$. I've seen the diamond vs ellipse picture in the book and I have some intuition as for why the Lasso can hit the corners of the constrained region, which implies that one of the coefficients is set to zero. However, my intuition is rather weak, and I'm not convinced. It should be easy to see, but I don't know why this is true. So I guess I'm looking for a mathematical justification, or an intuitive explanation of why the contours of the residual sum of squares are likely to hit the corners of the $||\beta||_1$ constrained region (whereas this situation is unlikely if the constraint is $||\beta||_2$). |
I tried removing doubles and nothing happened. Not sure what else to try | While rendering a mesh with smooth shading on, I get a dark region/shadow on certain faces. The effect is more evident when smooth shading is applied to a mesh containing ngons, with the ngons turning black when rendered. The blackening effect is visible in the viewport too. How can I solve this problem? |
I’m 19 and working as a stripper part time right now and I make 60k a year, and I plan on doing so for the next 7 years. I have 15k saved up, but it’s just in a bank account. I’m also in college majoring in nursing. I have scholarships and my parents are paying for the rest of my school costs so I won’t have any student loans. I don’t have any debt or loans or anything, and I’m pretty frugal. I don’t know anything about investing or stocks, so I was wondering what I should do? I’ve heard about Roth IRAs and how it’s beneficial for young workers whose tax brackets will go up later in life, but would it be good for me since nurses make not much more than I’m making right now? What other kinds of options are there for low risk high interest? | I am young, just started my career, and looking to begin investing so I can make my money work for me. I'm still living like I did in college (occasional purchase on myself, but most of it goes into savings) and I would like to take the extra money and invest it. What would you suggest are the best options for me to begin? I was considering getting a personal investor [a financial advisor] for perhaps a year or so, but I've heard that they really are not worth the money. I wanted to get the input of the great minds here. |
I just found a lg box of vacuum packed halibut fillets in my freezer. Been there at least 8 yrs. safe to eat? Worth a lot of money! | How do I know if a given food or ingredient I have is still good, or if I should discard it? How can I best preserve a food or ingredient? This broad question is intended as a "general reference" question to quickly answer many how long will food keep for? questions. Please feel free to edit this question to expand and clarify as needed. |
I have been using model averaging and model selection bases on AIC and BIC for a while. I have recently discover the stepwise regression technique and I found a lots of people critize this methods. Why stepwise regression is to avoid ? Is it just only because you may not capture interaction between variable and therefore loose informations ? Thank you | I would like to implement an algorithm for automatic model selection. I am thinking of doing stepwise regression but anything will do (it has to be based on linear regressions though). My problem is that I am unable to find a methodology, or an open source implementation (I am woking in java). The methodology I have in mind would be something like: calculate the correlation matrix of all the factors pick the factors that have a low correlation to each other remove the factors that have a low t-stat add other factors (still based on the low correlation factor found in 2.). reiterate several times until some criterion (e.g AIC) is over a certain threshold or cannot or we can't find a larger value. I realize there is an R implementation for this (stepAIC), but I find the code quite hard to understand. Also I have not been able to find articles describing the stepwise regression. |
I have a company webpage at "example1.com" and was developing a new webpage at "exemple2.com" (because it was everything already set). When I finished the page, I updated my "example1.com". So, at this time both "example1.com" and "example2.com" had the exactly same code. Couple of day later I disabled my "example2.com" site by removing its DNS configs. But... The root page on google was indexed on "example2.com" and when I removed this domain (and forbidden google to index them at the search console), my root page from "example1.com" didnt get indexed. So... I have all my pages from "example1.com" indexed (about 6 pages), and my root page isnt indexed... I already try the manual index at search console, but nothing until this moment... Any tips on how I can solve this? Or this is one of the cases that I just need to wait a month or so? Thanks!! | This is a general, community wiki question and answer pair intended to address any questions concerning the reasons a site or specific site contents do not appear in search engine results. If your question was closed as a duplicate of this question and you feel that the information provided here does not provide a sufficient answer, please open a discussion on . My site (or specific pages on my site) is not appearing in search engine results. Why isn't my content indexed and what can I do about it? |
I want to perform file operations(fread, fwrite... etc) with a array(char*, but if is possible with any type also will be good). I know that i can do it with sprintf and sscanf, but i no want use these. Why? i are writing a Intel 8080 emulator, and i are writing the RAM, so i will read more that individual chars, read ints and so on. I want use fread and fwrite because you can give them the size of the elements, with sprintf and sscanf you can use format, but i must write code for every type. At this moment i don't have any issues, nor much code, i only want know if my question has a answer, else i will see how convert a array of char to other data type... Resuming, i can use char* as FILE* ?. Sorry for my bat English... | Is there any way to create a memory buffer as a FILE*. In TiXml it can print the xml to a FILE* but i cant seem to make it print to a memory buffer. |
Suppose $f(z)$ is analytic in a neighborhood of the origin and $\sum_{i=1}^\infty f^{(n)}(0)$ converges. Prove that $f(z)$ extends to be an entire function. From the given information I can guess that $f$ has a Taylor extension in the neighborhood of $0$, but how can we say that it is expandable to an entire function? Please tell me how can we prove that $f$ is entire. AS the answers to this question does not provide me satisfactory answer | I recently came across the result that if $g$ is holomorphic in a neighbourhood of a point $z_0$ and $$\sum_{n=0}^{\infty }{g^{(n)}(z_0)} $$ converges then $g $ is an entire function. Now, my doubt is if the above series is absolutely convergent then can we say something more about $g$, like say $g$ is a polynomial? I could not find any non-polynomial entire function( I tried with functions like $e^z$, $\sin z $, et al), whose successive derivatives converge absolutely as series. Any help please? |
I have a type String that looks like '["123", 123, "testing"]'. How do I change that String into type Array? | Given a string of JSON data, how can I safely turn that string into a JavaScript object? Obviously I can do this unsafely with something like: var obj = eval("(" + json + ')'); but that leaves me vulnerable to the JSON string containing other code, which it seems very dangerous to simply eval. |
At first it would seem that if $p{\implies}q$ means "$p$ implies $q$", then if $p$ is false then the entire statement doesn't make sense. It looks like if we have no way of knowing whether $p$ implies $q$ or not, since $p$ was never a real thing in the first place. It would seem that the statement wouldn't have either "true" or "false" value, but rather "undecided". Why did mathematicians decide to give this statement a "false" value? | I am studying entailment in classical first-order logic. The Truth Table we have been presented with for the statement $(p \Rightarrow q)\;$ (a.k.a. '$p$ implies $q$') is: $$\begin{array}{|c|c|c|} \hline p&q&p\Rightarrow q\\ \hline T&T&T\\ T&F&F\\ F&T&T\\ F&F&T\\\hline \end{array}$$ I 'get' lines 1, 2, and 3, but I do not understand line 4. Why is the statement $(p \Rightarrow q)$ True if both p and q are False? We have also been told that $(p \Rightarrow q)$ is logically equivalent to $(~p || q)$ (that is $\lnot p \lor q$). Stemming from my lack of understanding of line 4 of the Truth Table, I do not understand why this equivalence is accurate. Administrative note. You may experience being directed here even though your question was actually about line 3 of the truth table instead. In that case, see the companion question And even if your original worry was about line 4, it might be useful to skim the other question anyway; many of the answers to either question attempt to explain both lines. |
I have a hard time doing this proof. Can anyone help me? Show that the following pairs of sets S and T are equinumerous by finding a specific bijection between the sets in each pair. $S = [0,1]$ and $T = [0,1)$ | How to define a bijection between $(0,1)$ and $(0,1]$? Or any other open and closed intervals? If the intervals are both open like $(-1,2)\text{ and }(-5,4)$ I do a cheap trick (don't know if that's how you're supposed to do it): I make a function $f : (-1, 2)\rightarrow (-5, 4)$ of the form $f(x)=mx+b$ by \begin{align*} -5 = f(-1) &= m(-1)+b \\ 4 = f(2) &= m(2) + b \end{align*} Solving for $m$ and $b$ I find $m=3\text{ and }b=-2$ so then $f(x)=3x-2.$ Then I show that $f$ is a bijection by showing that it is injective and surjective. |
Could someone please help me. I was wondering if I have to use "that" in the following sentence: I'm sure your friends will likely call you on your birthday. Should there be a "that" between sure and friends? Thank you. | "For someone used to the tiny creatures we get in England it was something of a shock." I think, in this sentence, relative pronouns before some words have been omitted. I know rules of omitting relative pronouns, but in this case I have failed to understand before which words relative pronouns can be placed to understand the sentence perfectly, which has been stated above. Please, explain the rules of omitting relative pronouns with the help of the sentence stated above, so that I can be able to understand this type of sentences easily. You can also use other sentences to explain this fact clearly. Thanks to everyone. |
– Schematic created using In the circuit shown if current is flowing from negative side of battery to positive side how multimeter can know the existence of resistor before electrons in wire hits the resistor? I mean how multimeter measures current before it reaches the resistor? How it knows that a resistor exists? | With the following circuits as examples : and How will the current I know how much to flow? Would any other wave travel first in the circuit and then come back and say so much current should flow? |
I am following a course on stochastic processes. One question is to Calculate $$lim_{n\to \infty} \sum^n_{i=0} e^{-n} \frac{n^i}{i!}$$ I see that it looks like the expected value of $e^{-n} \frac{n^{i+1}}{i!}$ but i don't know how to proceed. I tried to use mathematica but i'm not sure this is correct. Solve[Integrate[E^(-n) n^(i + 1)/Factorial[i], {n, 0, x}] == 1/2 Integrate[ E^(-n) n^(i + 1)/Factorial[i], {n, 0, Infinity}] , x, Reals] Thanks in advance | I'm supposed to calculate: $$\lim_{n\to\infty} e^{-n} \sum_{k=0}^{n} \frac{n^k}{k!}$$ By using WolframAlpha, I might guess that the limit is $\frac{1}{2}$, which is a pretty interesting and nice result. I wonder in which ways we may approach it. |
I'm trying to add a github project to my CV, but I can't add it because it's not actually owned by my "earlz" username, but rather is branched off into its own "team". Although, right now, I am the creator of the repo and only contributor. How can I add this project to my CV? And just for reference, my github name is Earlz, and the project I'm trying to add is this: | On Careers, when you try to add open source GitHub entries, it shows you repos which you own or are owned by an organization which you collaborate on. This would be fine with me; that just means that there isn't any fancy fetching of the project details via the API. However, it isn't possible to add any GitHub projects via the "other" button; it throws the error "Please use our GitHub page (/import/github/88888) to add Github projects.". Which means that I can only link to a small subset of the projects available on GitHub, even though I can link to almost anything else on the Internet via the other option. Could the restriction on GitHub links in the "other" form be removed? It could instead be replaced with a non-blocking "warning" sort of thing. Alternatively, keep a textbox at the bottom of the GitHub repo list where I can enter my own repo. |
Following prepared statement returns no result if I try like search('samsung'). public function search($searchFor) { try{ //connect to db $pdo = $this->_db->connect(); //set up SQL and bind parameters $sql = "select * from item where itemName like '%:searchfor%' or description like '%:searchfor%'"; $stmt = $pdo->prepare($sql); $stmt->bindParam(':searchfor', $searchFor, PDO::PARAM_STR); //execute SQL $rows = $this->_db->executeSQL($stmt); return $rows; } catch (PDOException $e) { throw $e; } } $rows return an empty array. But if I try select * from item where itemName like '%samsung%' or description like '%samsung%; it returns a matched item and works as expected. I found $sql = "select * from item where itemName like :searchfor or description like :searchfor"; $stmt = $pdo->prepare($sql); $stmt->bindValue(":searchfor", "%$searchFor%"); works. I had to use bindValue instead. This was a totally different issue in that the SQL was correct but I used bindParam instead of bindValue (which is the correct method), hence this is not a duplicate. | Here's my attempt at it: $query = $database->prepare('SELECT * FROM table WHERE column LIKE "?%"'); $query->execute(array('value')); while ($results = $query->fetch()) { echo $results['column']; } |
I try to run SP Flash Tool under Ubuntu MATE but after I chmod +x the executable file, I get this error: bash: ./flash_tool: cannot execute binary file: Exec format error bash: ./flash_tool.sh: Permission denied Anyone have any idea why? | I'm trying to run a program, but an error happens like this: bash: ./program: cannot execute binary file: Exec format error The result of file program was: program: ELF-32-bit LSB executable, ARM, EABI4 version 1 (SYSV), dynamically linked(uses share libs), for GNU/LINUX 2.6.16, not stripped How can I fix this error? I'm using Ubuntu 14.04.2 (amd64) with VMware. I also tried with Ubuntu i386, but result was same. |
Today i was working on a problem on a ring with goes as follows. Let A be a ring, prove that any element of A has either $0,1$ or an infinity of left inverses. I think i found a proof of this statement, but the official solution looks nothing like mine. It is said that i should show that if any element has two distinct left inverses then there's an infinity of them (which i did) by considering the kernel of $f:x\rightarrow ax$. My try goes as follow: let $x,y$ be such inverses then for all $p,q\in\mathbb Z$ satisfying $p+q=1$, $px+qy$ is another left inverse, because : $(px+qy)a=p+q=1$. And for all $p\in\mathbb Z$ we have : $px-(p-1)y=(p-1)x-(p-2)y$ that implies $x=y$. Hence there are infinitely many distinct elements of the form $px+qy$. Is my proof flawed ? | There's a theorem of Kaplansky that states that if an element $u$ of a ring has more than one right inverse, then it in fact has infinitely many. I could prove this by assuming $v$ is a right inverse, and then showing that the elements $v+(1-vu)u^n$ are right inverses for all $n$ and distinct. To see they're distinct, I suppose $v+(1-vu)u^n=v+(1-vu)u^m$ for distinct $n$ and $m$. I suppose $n>m$. Since $u$ is cancellable on the right, this implies $(1-vu)u^{n-m}=1-vu$. Then $(1-vu)u^{n-m-1}u+vu=((1-vu)u^{n-m-1}+v)u=1$, so $u$ has a left inverse, but then $u$ would be a unit, and hence have only one right inverse. Does the same theorem hold in monoids, or is there some counterexample? |
I want to use regex on the jsf (.xhtml) page. When i want to use regex i keep getting this error SyntaxError: unterminated parenthetical and my code is var data2 = ($("#data").val()).replace(/User(/g,"{"); I use regex earlier in php pages but never get such error. | I am tired of always trying to guess, if I should escape special characters like '()[]{}|' etc. when using many implementations of regexps. It is different with, for example, Python, sed, grep, awk, Perl, rename, Apache, find and so on. Is there any rule set which tells when I should, and when I should not, escape special characters? Does it depend on the regexp type, like PCRE, POSIX or extended regexps? |
How can one be able to type all contemporary letters in Dutch language on ubuntu or debian using ibus and a standard English qwerty keyboard? E.g., the letter "ó" in the word "vóór" (means "before"). Solutions meeting the following conditions are strongly preferred: A Dutch input module (not German or something else). Installable via a .deb package or Ubuntu package manager. No mouse action is required to input these letters. I am using a standard English qwerty keyboard with ibus input framework. Ibus Preferences -> Input Method -> Add has only a Dutch; Flemish - Belgian module available for Dutch that appears to be unable to achieve what I am asking for (although ö, ô and è can be typed). | Currently I use the character palette applet in gnome panel to put special characters into text. This is okay, but I have to stop typing, select the character I want from the applet and then copy and paste. Is there a way to simply type special characters with different key combinations? If so, how do I do it? |
Consider the angular momentum operator $\hat{L_x}=\hat y\hat{p}_z-\hat{z}\hat{p}_y$ and the potential operator $\hat{V}$ where the potential $\hat{V}=\hat{V}(\hat{r})$ is spherically symmetric. It can be shown that $[\hat {L}_x, \hat {V}] = \hat y [\hat {p}_z, \hat V]-\hat z [\hat {p}_y, \hat V]. $ I tried showing this myself and found that this is only true if $$[\hat y, \hat V]=0 $$ and $$[\hat z, \hat V]=0. $$ Why are the last two equations equal to zero? | I'm trying to show, for the Hamiltonian $H = \vec{P}^2/2m + V(\vec{X})$, that $[\vec{L}^2,H]=0$ if $V(\vec{X}) = V(|\vec{X}|)$, and I pretty much almost have it, there's just one thing I'm getting messed up on. So what I did was: $$ [\vec{L}^2,H] = [L_x^2 + L_y^2 + L_z^2, \frac{\vec{P}^2}{2m} + V(\vec{X})] = [L_x^2 + L_y^2 + L_z^2, \frac{\vec{P}^2}{2m} + V(|\vec{X}|) ] $$ $$ = [L_x^2,\frac{\vec{P}^2}{2m} + V(|\vec{X}|)] + [L_y^2,\frac{\vec{P}^2}{2m} + V(|\vec{X}|)] + [L_z^2,\frac{\vec{P}^2}{2m} + V(|\vec{X}|)] $$ Looking at the $L_x^2$ component: $$ \rightarrow [L_x^2,\frac{\vec{P}^2}{2m} + V(|\vec{X}|)] = \frac{1}{2m}[L_x^2,P^2] + [L_x^2,V(|\vec{X}|)] $$ $$ = \frac{1}{2m}[L_x^2,P_x^2+P_y^2+P_z^2] + [L_x^2,V(|\vec{X}|)] $$ $$ = \frac{1}{2m} \bigg( [L_x^2,P_x^2]+[L_x^2,P_y^2]+[L_x^2,P_z^2] \bigg) + [L_x^2,V(|\vec{X}|)] $$ Now for the momentum parts, that's a lot of tedious work that I won't type up, but at the end of the day, I get that $$ [L_x^2,P_x^2]=[L_x^2,P_y^2]=[L_x^2,P_z^2]=0 $$ and similarly for $[L_y^2,P^2]=0$ and $[L_z^2,P^2]=0$. My problem is this, for this to work out, I need $$ [L_x^2,V(|\vec{X}|)] = 0 $$ and similarly $$ [L_y^2,V(|\vec{X}|)]=[L_z^2,V(|\vec{X}|)]=0 $$ but I don't really understand why that would be the case? Any insight would be appreciated. |
I am trying to get Don't starve for my Samsung Chromebook with Ubuntu and I can't figure out if i can play it since it's a .rar file. If anybody knows please let me know. | How can I install a tarbz2 package. Example: I have downloaded firefox 8 tar.bz2 . I want to know a general method for installation of tar.bz2 package. |
Let $a,b \in \mathbb {Z} $ and let $m$ be an integer greater than $2$. I found a counterexample to the equation $$(a+b)\mathrm {mod} m = a\mathrm {mod} m + b \mathrm {mod} m $$ where $m>2$. But that was only after I thought I had proven that the equation does hold, so I was wondering if someone could point out to me where the flaw is in the following. If we divide $a $ and $b $ by $m $, then we have by the division algorithm $$a=mc+x $$ $$b=md+y $$ Adding the equations together renders $$a+b=me+(x+y) $$ And since $a\mathrm {mod} m + b \mathrm {mod} m= x+y $, then from the third equation, it seemes that the proposition holds. | modular arithmetic How Can I prove (a+b) mod m = (a mod m) + (b mod m)) mod m ? |
If mashed bananas are accidentally left on the counter overnight can they still be used for baking? | If I left food out of the refrigerator for some period of time, is it still safe? If I left it out too long, can I salvage it by cooking it more? |
I've been asked a question by a student - it's off the beaten track, and I am struggling to get a definitive answer, even off other physics teachers... If we have an open tube, so open at both ends, how can we end up with a standing wave being formed in this tube? How can the initial wave reflect back and cause the formation of a standing wave? I have my own ideas - but i am never happy with going with what i think, i always try and get the idea validated and hopefully approved! Cheers, Marc' | We know that standing waves are created when any wave traveling along the medium will reflect back when they reach the end. But in an open organ pipe, there is nothing to oppose the wave and reflect it back. So then how are standing waves created in such a case? In standing waves where is the pressure greater, at nodes or anti-nodes? |
I've been seeing a surge in the number of "Crawled - currently not indexed" pages in search console recently. Screenshot below: When I look in detail to URLs one by one, I see that some of them are crawled but not fetched, like below: Site's average response time to googlebot seems to be in the range of 200-300 ms. What can be a reason for these crawls but no fetches? | This is a general, community wiki question and answer pair intended to address any questions concerning the reasons a site or specific site contents do not appear in search engine results. If your question was closed as a duplicate of this question and you feel that the information provided here does not provide a sufficient answer, please open a discussion on . My site (or specific pages on my site) is not appearing in search engine results. Why isn't my content indexed and what can I do about it? |
I am trying to bake texture for a model, and I get the infamous error "No objects or images to bake to". I have done a lot of googling to try and solve this, and in particular I have read pretty much every post related to that on this forum. It does not help and I still get the error. Here below are some details - please ask for more if necessary. Any help would be hugely appreciated. Set up: I have an obj file, in the same folder as an mtl file along with a jpg picture for the texutre. Import: I open up Blender 2.7 on Linux, default mode, delete the cube and subsequently import the obj file; I can see it alright and I recenter it. Texture: in the materials and texture tabs, I select the jpg image for texture, so that when I set the viewport shading to texture I see the texture on the 3D model view. Bake: making sure that coordinates is set to UV and that Map is set to UVMap in the Mappin dropdown menu of the Texture tab, I then go to the Render tab to the Bake dropdown menu. I click the Bake to Color vertices and choose Texture in the rollout. Clicking bake then yields the error. Details: I make sure that the object is selected, both in the 3D viewport and in the Outliner. In the latter, the icons are on (the eye, the pointer and the camera). I have also been careful enough to open up a second subwindow for the UV/Image editor, and in there I select the jpg image for texture that is in the folder, and I can see the UV map alright. Also, this is all with the Blender Render engine, not with cycles. What I have in mind after all this, and the reason I want to do it, is that I ultimately want to export the model to a ply file in a way that all vertices are listed together with an RGB color for each vertex, which is impossible currently (because color/texture is associated to faces of the mesh and not to vertices), even if I tick the "include vertex color" option in the ply export. Thanks a looot in advance. I am absolutely out of resources here. Gustavo Edit: the thread is different I believe. My question is more specific. However the answer to that thread does include what I was missing: adding a set of vertex colors under the object data tab. | This is frustrating for me. The UV-textures to vertex cols add-on doesn't seem to work despite the specific instructions. Any other tutorials I can find are either very old or very poor. I'd like to know how to do this in Blender 2.79. I need vertex colors in my ambient occlusion for use in Shader Forge. |
var ninja = (function(){ function Ninja(){}; return new Ninja(); })(); Why is the function above encapsulated in parentheses and why is there a (); at the end? I think it's a constructor function because of the (); at the end, but why is the object wrapped in parentheses? | How would you explain JavaScript closures to someone with a knowledge of the concepts they consist of (for example functions, variables and the like), but does not understand closures themselves? I have seen given on Wikipedia, but unfortunately it did not help. |
I've installed it, I can run it via the terminal, I also can find it via search (comes up as untitled - Sublime Text) and lock it to the launcher, but when I right click a file and try to choose sublime as the application it's not in the list. I've tried setting it as default via the instructions given , but that didn't help. I've set it as the default editor for git commits, but that doesn't work either. I've checked that it's in the path: subl sits in /usr/bin and echo $PATH returns: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin Anyone having the same issue? | I am running Ubuntu 15.10. My /usr/share/applications/sublime_text.desktop contains the following: [Desktop Entry] Version=1.0 Type=Application Name=Sublime Text GenericName=Text Editor Comment=Sophisticated text editor for code, markup and prose Exec=/opt/sublime_text/sublime_text %F Terminal=false MimeType=text/plain; Icon=sublime-text Categories=TextEditor;Development; StartupNotify=true Actions=Window;Document; [Desktop Action Window] Name=New Window Exec=/opt/sublime_text/sublime_text -n OnlyShowIn=Unity; [Desktop Action Document] Name=New File Exec=/opt/sublime_text/sublime_text --command new_file OnlyShowIn=Unity; When I right-click on a markdown file (xxx.md) in Gnome Files (formerly "Nautilus"), I cannot see "Sublime Text" as a choice, even when I select "View All Applications". I even tried adding %F to the lines Exec=/opt/sublime_text/sublime_text -n and Exec=/opt/sublime_text/sublime_text --command new_file in the [Desktop Action Window] and [Desktop Action Document], respectively, but it did not change anything. I even ran sudo update-desktop-database. What am I doing wrong? |
I am having a code that says: #include<stdio.h> typedef struct string{ char *ch_ptr; }str_t; #define newdef(a,b) \ char a ## sumthing[b * sizeof(str_t)]; \ str_t *a = (str_t *)a ## sumthing main(){ newdef(input,5); /* some lines of code */ } Optional changes to code: #include<stdio.h> typedef struct string{ char *ch_ptr; }str_t; #define newdef(a,b) \ char a ## sumthing[b * sizeof(str_t)]; \ str_t *var1 = (str_t *)a ## sumthing main(){ newdef(input,5)="Hello"; printf("%s\n",input); /* some lines of code */ } Can anyone explain what this code segment means? Is input in this code a string (hope not) or a variable? If a variable then why doesn't the compiler throw an undeclared variable error? | As mentioned in many of my previous questions, I'm working through K&R, and am currently into the preprocessor. One of the more interesting things — something I never knew before from any of my prior attempts to learn C — is the ## preprocessor operator. According to K&R: The preprocessor operator ## provides a way to concatenate actual arguments during macro expansion. If a parameter in the replacement text is adjacent to a ##, the parameter is replaced by the actual argument, the ## and surrounding white space are removed, and the result is re-scanned. For example, the macro paste concatenates its two arguments: #define paste(front, back) front ## back so paste(name, 1) creates the token name1. How and why would someone use this in the real world? What are practical examples of its use, and are there gotchas to consider? |
My Area51 site proposal, , just got into commitment phase two days ago. Why does it show that I have 69K reputation, when I actually have 9.7K? | What does the total reputation field on Area51 represent? It's obviously not the total of the user's reputation on the various sites, as that is the number listed as user reputation. |
I learned that it's common to do dimensionality reduction before clustering. But, is there any situation that it is better to do clustering first, and then do dimensionality reduction? | I am trying to perform document-level clustering. I constructed the term-document frequency matrix and I am trying to cluster these high dimensional vectors using k-means. Instead of directly clustering, what I did was to first apply LSA's (Latent Semantic Analysis) singular vector decomposition to obtain the U,S,Vt matrices, selected a suitable threshold using the scree plot and applied clustering on the reduced matrices (specifically Vt because it gives me a concept-document information) which seemed to be giving me good results. I've heard some people say SVD (singular vector decomposition) is clustering (by using cosine similarity measure etc.) and was not sure if I could apply k-means on the output of SVD. I thought it was logically correct because SVD is a dimensionality reduction technique, gives me a bunch of new vectors. k-means, on the other hand, will take the number of clusters as the input and divide these vectors into the specified number of clusters. Is this procedure flawed or are there ways in which this can be improved? Any suggestions? |
I am locked out of my Samsung Galaxy y Duos Lite and I have forgotten my password. USB debugging is not turned on. Is there any way to backup my sms onto my pc?? | I have an Android device which is running Android 4.0.3 (or something like that). My little brother decided to try and guess my lock screen pattern the other day, and ended up locking me out. I have since been unable to log back in to the tablet using my Google Account details. I provided the correct login details, however it says they are incorrect. Could this be connected to the fact I have no internet connection? I have no internet connection as the device is WiFi only, and the WiFi is currently turned off. I cannot turn it on, as I am locked out. How can I log back into my tablet without wiping the user data? |
Suppose $f_{-a}(x)$ is the pdf for $N(-a,\sigma^2)$ and $f_{a}(x)$ is the pdf for $N(a,\sigma^2)$. Let $f(x)=0.5f_{-a}(x)+0.5f_{a}(x)$ be the mixture density. Is $c=0$ the unique center for $f(x)$ in the sense that $f(x)=f(2c-x)$ for any $x$? My guess is that it is the unique center, but I don't know how to rigorously show it. Thanks! | I am trying to show that the central moment of a symmetric distribution: $${\bf f}_x{\bf (a+x)} = {\bf f}_x{\bf(a-x)}$$ is zero for odd numbers. So for instance the third central moment $${\bf E[(X-u)^3] = 0}.$$ I started by trying to show that $${\bf E[(X-u)^3] = E[X^3] -3uE[X^2] + 3u^2E[X] - u^3}.$$ I am not sure where to go from here, any suggestions? Is there a better way to go about proving this? |
I started by converting the following $\sum_{n=0}^\infty \frac{n^3}{n!}$ into $$\sum_{n=1}^\infty \frac{n(n-1)(n-2)}{n!} + \frac{3n(n-1)}{n!} + \frac{n}{n!}.$$ Did i get it right and where should I go from here ? | I have to find the sum of the following series: $$\sum\limits_{n=1}^\infty \frac{n^3}{n!}$$ I know how to prove the convergence of this series, but how do i find the sum. I can't use the properties of derivation or integration of the series, i have to do it using the definition that a series converges iff it's sequence of partial sum converges. |
I need to use filtered subscription using lightning:empAPI for Push Topic notifications. But it does not work with Id filter after records page refresh (F5) whereas when it subscribes on the first place the notifications are coming in. Does it mean that only one active filtered subscription has to exist for the record and user session? If so how can I unsubscribe prior the component is reloaded and new subscription is initiated during refresh (F5). <aura:attribute name="channel" type="String" default="{!'/topic/QuoteProcessing?Id=' + v.recordId}"/> <!--<aura:attribute name="channel" type="String" default="/topic/QuoteProcessing"/>--> <aura:handler name="init" value="{!this}" action="{!c.doInit}" closable="false"/> // doInit just executes helper.subscribe helper.subscribe(component, event); // helper.subscribe subscribe : function(component, event) { const empApi = component.find('empApi'); const channel = component.get('v.channel'); const replayId = -1; //var Qchannel = '/topic/QuoteProcessing?Id='+component.get('v.recordId'); // Subscribe to an event //console.log('Qchannel '+Qchannel); empApi.subscribe(channel, replayId, $A.getCallback(eventReceived => { console.log('Received event ', JSON.stringify(eventReceived)); $A.get('e.force:refreshView').fire(); var toastEvent = $A.get("e.force:showToast"); toastEvent.setParams({ mode : "dismissable", message : "Processing - "+eventReceived.data.sobject.ProcessingStatus__c, type : "info", duration : 8000 }); toastEvent.fire(); })) .then(subscription => { console.log('Subscribed to channel ', subscription.channel); console.log('subscription ', JSON.stringify(subscription)); component.set('v.subscription', subscription); }); empApi.onError($A.getCallback(error => { console.log('EMP API error from subscribe: '+ JSON.stringify(error)); })); } PushTopic query contains Id and the field I am changing in SELECT clause. Subscription is established but notifications are not coming. | I have a very simple component: PushTopicTest.cmp <aura:component implements="flexipage:availableForAllPageTypes" access="global"> <lightning:empApi aura:id="empApi"/> <aura:handler name="init" value="{!this}" action="{!c.onInit}"/> </aura:component> PushTopicTestController.js ({ onInit: function(component, event, helper) { var empApi = component.find("empApi"); empApi.setDebugFlag(true); empApi.subscribe("/topic/AccountChanges?Id=0011t0000033C9QAAU", -1, function(message) { console.log("Event Received : " + JSON.stringify(message)); }); } }) I also have PushTopic created like this: What I am trying to do, is to only receive events for specific record Id. Based on documentation this should work: "/topic/AccountChanges?Id=0011t0000033C9QAAU", but it doesn't. "/topic/AccountChanges" works though. I've tried Id='0011t0000033C9QAAU' aswell, but no luck. Do you know if it is possible at all? |
I like the way the author Igor Sokolnikoff numbers his sections and equations, and would like to mimic this style in my own book. The section number is never reset. For example chapter one ends with section 17, and chapter two begins with section 18. Also equations are numbered according to section, not chapter, as (17.1), (17.2), etc. I am using MikTex, pdflatex Thank You! | Some document elements (e.g., figures in the book class) are numbered per chapter (figure 1.1, 1.2, 2.1, ...). How can I achieve continuous numbering (figure 1, 2, 3, ...)? And vice versa: Some document elements (e.g., figures in the article class) are numbered continuously. How can I achieve per-section numbering? \documentclass{book}% for "vice versa" variant, replace `book` with `article` \begin{document} \chapter{foo}% for "vice versa" variant, replace `\chapter` with `\section` \begin{figure} \centering \rule{1cm}{1cm}% placeholder for graphic \caption{A figure} \end{figure} \end{document} Bonus question: Is it possible to adjust the numbering of the sectioning headings themselves? Can I, e.g., switch from per-chapter to continuous numbering of sections in the book class? |
How did their spaceship escape the black hole Gargantua? | Some things have confused me about the black hole in Interstellar. Namely: How did Cooper ever leave the black hole once he was inside it? How was Cooper able to suspend in the tesseract? Something allowed him to decelerate. How was the AI machine able to send Cooper messages considering messages are EM waves and a black hole's gravity is such that it will suck EM waves into the singularity? |
System: macOS Sierra 10.12.6 Raw input(example): . ├── f1.md ├── f2.md ├── f3.md ├── f4.txt ├── f5.csv └── f6.doc 0 directories, 6 files In a test folder, there are 6 files. Expected output: . ├── all.tar ├── f1.md ├── f2.md ├── f3.md ├── f4.txt ├── f5.csv └── f6.doc 0 directories, 7 files Trying and Problem: tar -cvf all.tar f1.md f2.md f3.md f4.txt f5.csv f6.doc Though I get the result from the above method but I have to inputing all file names and the compressed file name, which is inconvenient. For example , I can select all files and right click, then choose compressed option without inputing all.tar (I don't mind the .tar filenames.) Hope: command-line method without inputing specific file names. | Is it possible to use tar to compress a folder without giving the filename of the archive to store in? Normally you use: tar -zcvf prog-1-jan-2005.tar.gz /home/jerry/prog I want to do something like tar -zcvf /home/jerry/prog and have it create prog.tar.gz |
I'm not sure what to do here. It seems like Morera's Theorem, but even then I'm not sure how to choose the triangular path. | This is a problem from Complex Variable (Conway's book) 2nd ed. (Section 4.4) 9. Show that if $f: \mathbb{C}\to\mathbb{C}$ is a continuous function such that $f$ is analytic off $[-1,1]$ then $f$ is an entire function. I already have a solution by Morera's theorem that split this problem in 5 cases. I think this solution is too long and I'm trying to solve this using a different approach. Any ideas ? |
We already have one developer license, but want to buy one more developer license. Is it possible under the same Apple ID? We want to buy one more license under same company name, same Apple ID. Basically Apple ID (having agent role) is legal owner. So under the same Apple ID, we wanted to buy a 2nd license. If no, what are the alternate ways? | we already have one developer license. Now we want to buy one more developer license. Is it possible under the same AppleID? We want to buy one more license under the same company name , same apple Id, basically apple ID(having agent role) is legal owner. So under same apple id wanted to buy 2nd license. If no what are the alternate ways... Please note Entity Type: Company / Organization |
I am a bit confused about the creation of SPF records. I have my hosting domain: hosting.mydomain.com, this is the hostname of the actual server running postfix etc. I have configured my DNS like this: mydomain.com @ A 1.2.3.4 (mail server IP) @ MX 10 mail.mydomain.com @ TXT v=spf1 mx a a:hosting.mydomain.com ~all hosting A @ mail A 1.2.3.4 (mail server IP) Now do I need to include the a:hosting.mydomain.com in my SPF record? And when I have another domain on the same server configured like this: otherdomain.com @ A 9.8.7.6 (web server) @ MX 10 mail.otherdomain.com @ TXT v=spf1 mx a ~all mail A 1.2.3.4 (mail server IP) Does this SPF record need to include a:hosting.mydomain.com I am running Webmin/Virtualmin but hosting the DNS external. When I send email through the webmail the sender is always hosting.mydomain.com. Are these SPF records correct? | This is a about setting up . I have an office with many computers that share a single external ip (I'm unsure if the address is static or dynamic). Each computer connects to our mail server via IMAP using outlook. Email is sent and received by those computers, and some users send and receive email on their mobile phones as well. I am using to generate an SPF record and I'm unsure about some of the fields in the wizard, specifically: Enter any other domains who may send or relay mail for this domain Enter any IP addresses in CIDR format for netblocks that originate or relay mail for this domain Enter any other hosts which can send or relay mail for this domain How stringent should SPF-aware MTA's treat this? the first few questions i'm fairly certain about... hope i have given enough info. |
If I throw a clock towards a black hole, its time slows down, it is redshifted, and according to many theories it never reaches the event horizon from my point of view. How is it then, that a star can fall into a black hole, and be observed to do so by me (by its emission of gravitational waves)? | I've read a lot of conflicting answers in these forums. However, today saw the awesome announcement of gravitational waves. Two black holes merged: Not only that, they merged FAST. In 1/5th of a second revolving around each other 250 times a second. The entire event was quicker than a heartbeat. Moreover, we observed this happening as distant outsiders. So now we can say for sure: Objects approaching the event horizon DO NOT appear to slow down Black holes CAN merge in a finite (and quick) amount of time And all this is wrt a frame of reference far, far away To quote the NYTimes article: One of them was 36 times as massive as the sun, the other 29. As they approached the end, at half the speed of light, they were circling each other 250 times a second. And then the ringing stopped as the two holes coalesced into a single black hole, a trapdoor in space with the equivalent mass of 62 suns. All in a fifth of a second, Earth time. However, everything I've read so far has let me to believe that an outside observer should never be able to measure the collision happening in a finite time. So what exactly is happening here? I must have read at lest 5 different versions of this so far everywhere in these forums over the past several years. |
There are a lot of free videos on . For example list. There are also a lot of free Webinars that are open to every one. I do not have access to internet at all times. I would like to watch some videos offline. Do you know what is the format of these videos, and how can I download them? | I am trying to download a Flash video, so I can try to convert it to a normal DVD. (.) Is it possible to download this video? If so, how could I do this? |
On English Language & Usage, I noticed that even the user has hats. In its case, how is the hat it is wearing selected? | Why does ? And more importantly: why does she not wear them? Please, show some goddamn holiday spirit! Can we get Community to wear her hats, either randomly or through popular vote? |
I'm looking into tax free shopping in Japan and I noticed that if I decide to buy consumables tax free then I cannot eat them on the spot. From my understanding, if I buy consumable products at these stores they will give me a sealed bag with my consumables which I have to wait until I leave the country to open it. Why can't I just open up the bag when I leave the store? What is the reason to have that tax free rule implemented? Edit: I explained the situation more in detail to differentiate between buying from a duty free spot in the airport than tax free shops. If they work the same way let me know. | I am not one for buying things in airports but recently my wife asked me to get her an alcoholic beverage while flying from the USA to Ireland (JFK-DUB). I made the purchase in JFK and was surprised to be told I had to collect it when departing for my flight as I board the plane. The sales assistant's English wasn't their best so I may have misheard and my Yorkshire twang may have thrown her, but I was somewhat surprised as to why I couldn't carry the bag myself to the plane. Is there a law that prevents me from carrying my purchase to the plane or is this an added service I was charged, which I was duped into paying? When boarding the plane there were several others who had to pick up their sealed duty free bags (why sealed?) so it wasn't just me. No explanation was given. |
I'm looking for a DVD authoring application for Ubuntu 19.04 DeVeDeNG works, but I'm not happy with the main menu. Bombono works great in 18.04, but not 19.04. Any other suggestions for an application that works in 19.04? The question is not duplicated because it is a question after DVD authoring and not DVD burning. | I have tried countless cd/dvd burning software on ubuntu 12.04 and none of them work for me, any ideas guys? I've tried tovidgui, bombono dvd,and mestelix, they are all so very confusing is there any program like dvdflick that is just straight to the point? |
I'm new to Python, so please bear with me. Why isn't Python throwing an error when it compiles the following code. def b_search(left, right): while left <= right: mid = left + (right-left)//2 if nums[mid] == target: return mid if nums[mid] < target: left = whatever else: right = mid-1 return -1 Wondering how there's no error even though 'nums' isn't defined, and neither is 'whatever', nor 'target'. Thanks! | What exactly are the Python scoping rules? If I have some code: code1 class Foo: code2 def spam..... code3 for code4..: code5 x() Where is x found? Some possible choices include the list below: In the enclosing source file In the class namespace In the function definition In the for loop index variable Inside the for loop Also there is the context during execution, when the function spam is passed somewhere else. And maybe pass a bit differently? There must be a simple reference or algorithm somewhere. It's a confusing world for intermediate Python programmers. |
Why is ch pronounced as "Q", as in choir, and are there any other instances where ch is used as the letter "Q"? | Is there a rule to understand how the group "Cha" has to be pronounced? "Character" sounds with a hard first syllable, while "Charm" sound softer, but I don't find how to tell which sound to use before earing someone saying the word. It could be because of the double consonant "rm" vs "ra"? Or is it just a matter of knowing the rule for every single word? EDIT: More specifically, let's talk about UK English pronunciation. |
$\vec F=m\vec a$ ,for moving object with 10 $km/s$ in a constant manner ,where acceleration is zero. ie No force on object ? | As a layman, i can calculate approx "displacement" just by observing the moving object. And accurately by using a simple "scale". Similarly, again, I can calculate angle from origin by using displacement in $x$ and $y$ dimensions. Similarly I can use a stopwatch and scale to understand velocity. But when I read about , first of all it confuses with the english word "force", we use in real life. To some extent I am sure, it has nothing to do with that. So exactly what is it in the real sense. How can a layman, see force as, just like he can see displacement or angle? Or force is just a quantity defined by physicists to simplify the combinations of $ma$, they might be facing every time. And thus came up with term "force" ( which is similar in spelling to english word in oxford dictionary). And lastly, why not force has just been called as something proportional to mass and it's displacement or velocity. Why something at the level of change of velocity has been used to define it. |
For example, given the differential equation $\dfrac{\mathrm{d}y}{\mathrm{d}x}=y\tag*{}$ We do, $\dfrac{\mathrm{d}y}{y}=\mathrm{d}x\tag{*}$ At which point we go and integrate both sides. Is there a rigorous justification for being able to go to $(*)?$ | I see an equation like this: $$y\frac{\textrm{d}y}{\textrm{d}x} = e^x$$ and solve it by "separating variables" like this: $$y\textrm{d}y = e^x\textrm{d}x$$ $$\int y\textrm{d}y = \int e^x\textrm{d}x$$ $$y^2/2 = e^x + c$$ What am I doing when I solve an equation this way? Because $\textrm{d}y/\textrm{d}x$ actually means $$\lim_{\Delta x \to 0} \frac{\Delta y}{\Delta x}$$ they are not really separate entities I can multiply around algebraically. I can check the solution when I'm done this procedure, and I've never run into problems with it. Nonetheless, what is the justification behind it? What I thought of to do in this particular case is write $$\int y \frac{\textrm{d}y}{\textrm{d}x}\textrm{d}x = \int e^x\textrm{d}x$$ $$\int \frac{\textrm{d}}{\textrm{d}x}(y^2/2)\textrm{d}x = e^x + c$$ then by the fundamental theorem of calculus $$y^2/2 = e^x + c$$ Is this correct? Will such a procedure work every time I can find a way to separate variables? |
Cannot really figure out how to create such a list: 1) List item 2) List item 3) List item Here's what I have to use so far: \begin{enumerate} \item[1)] List item \item[2)] List item \item[3)] List item \end{enumerate} Without these [1)]..[3)] dots appear instead of parentheses. | Is there a guide out there on how to customize the enumerate and itemize instances in my code? (I'm using the Memoir class in LaTeX for Windows, and I have the enumitem package included.) I want to mess with the margins and spacings to make my lists look a little less "LaTeX-default"... |
I am tasked with generating an email address for new users in our environment who may have special characters (such as an umlaut and accents) in their full names. While some email systems can handle these characters I am being told to generate email addresses that can convert these characters to a standard ASCII format. So for example, John Señior would be created as john.senior@... and Jane Fraü would be created as jane.frau@... Has anyone found a regex expression or library that can handle such a requirement. UPDATE - I am planning on performing the replacement in PowerShell, but could use any Windows compiled libraries as well. | I'm trying to convert some strings that are in French Canadian and basically, I'd like to be able to take out the French accent marks in the letters while keeping the letter. (E.g. convert é to e, so crème brûlée would become creme brulee) What is the best method for achieving this? |
How do I add a new empty line to the beginning of a file under MacOS and Linux? I have tried the below command and it produces a new line character under MacOS sed -i.bak '1s/^/TESTe\n/' test.py | I've been looking around sed command to add text into a file in a specific line. This works adding text after line 1: sed '1 a\ But I want to add it before line 1. It would be: sed '0 a\ but I get this error: invalid usage of line address 0. Any suggestion? |
Let $\mathcal{M}_{n,p}(\mathbb{K})$ be the set of matrices $n\times p$ with coefficients in $\mathbb{K}$. Let $A\in\mathcal{M}_{n,p}(\mathbb{Q})$. We suppose there exists a non zero solution $X\in\mathcal{M}_{p,1}(\mathbb{R})$ to $AX=0$. ($0$ denotes $[0]_{p,1}$) Show that there exists a non zero solution $X'\in\mathcal{}_{p,1}(\mathbb{Q})$ to $AX'=0$ PS : This is NOT a duplicate of , which gives a zero solution in my case. I've tried building up the system of linear equations linked to $AX=0$. I got the result for simple small square matrices, but I can't manage to generalize it to all the matrices. | Let $A ∈ M_{m\times n}(\mathbb{Q})$ and $B ∈ \mathbb{Q}^m$. Suppose that the system of linear equations $AX = B$ has a solution in $\mathbb{R}^n$. Does it necessarily have a solution in $\mathbb{Q}^n$? Where do I start? I feel I can use this to : $$x_i=\frac{1}{a'_{ii}}\left(b'_i - \sum_{j=i+1}^{k} a'_{ij} x_j \right).$$ Here is a thought that just crossed my mind, but I'm not sure if this is legal: Suppose $Y\in \{\mathbb{R}\setminus \mathbb{Q}\}^n$ and $Y'\in\mathbb{Q}^n$ are solutions to $AX=B$. Then $AY=AY'=B$, or $A(Y-Y')=A(Y+(-Y'))=0$, but addition between $\{\mathbb{R}\setminus \mathbb{Q}\}^n$ and $\mathbb{Q}^n$ is . . . |
(i) $Y^\emptyset$ has exactly one element, namely $\emptyset$, whether $Y$ is empty or not, and (ii) if $X$ is not empty, then $\emptyset^X$ is empty. How do you prove these statements to be true? | Let $ D = 2^\mathbb{N} $, i.e., D is the set of all sets of natural numbers. What's the meaning of this definition? Intuitively, I would suggest that $ D = \{1,2,4,...\} $ but the explanation "set of all sets" leads me to the guess that this is wrong. |
Execute permission can be reasoned as a special program access control mechanism. The search permission on the other hand is described like this in the POSIX specification for an error code for open [EACCES] Search permission is denied on a component of the path prefix, or ... and for fchdir [EACCES] Search permission is denied for the directory referenced by fildes. Why is search permission mandatory for `cd'ing or traversing down a directory? What security rationale was there? Why does it has to be separate from read permission? | In my CMS, I noticed that directories need the executable bit (+x) set for the user to open them. Why is the execute permission required to read a directory, and how do directory permissions in Linux work? |
In how many ways can you arrange all letters in the word MISSISSIPPI so that 1) all four I’s are together? 2) two P’s are NOT next to each other? 3) no two I’s are next to each other? | "How many ways are there to arrange the letters in the word 'MISSISSIPPI' in such a way that there are no three consonants in a row?" I am thinking like this. The following are 'slots' for the letters of our word: _ _ _ _ _ _ _ _ _ _ _. There are 21 consonants in total (English). The first slot as 21 possibilities, the second also has 21, but the third has only 5 possibilities. So how many ways can I place vowels within this word... I don't know. I can try to enumerate all of the place the I's can go, but there has to be a better way than doing that. |
I've tried placing tainted blocks, fibrous taint, all of it. What do I do? | I'm trying to make taint spread to a certain area in my world, as in, to a small NPC structure. Is there any way I can do this? I even tried using MCEdit to set the biome, but there's no "enter biome ID" thing, and Tainted Land isn't listed. |
I am a foreign student with a Canadian Resident Permit. I intend to travel back to my country for a holiday and will come back to Canada to pursue my study. My flight to my country (Zambia) is through Seattle in the USA where I need to change plane. Do I need a US visa to transit even though I am not getting out of the airport? | In Europe usually you don't need to go through immigration to change planes (unless you are entering/exiting Schengen). Is it the case in the US as well? May I catch a connecting flight on one of the US airports if I don't have US visa? |
I recently bought a bunch of new hard drives, servers and other items. What is a good way to stress test the hard to ensure it won't crash in the first week? I've read and heard that if hardware is to break it will be within the first week typically | Here's what would be ideal: A list of all the hardware components potentially found on one's computer A method (or list of methods) for testing each of these The accuracy of these methods My personal requests are: -How to test your motherboard -How to test your wireless receiving apparatus -How to test CD/DVD-RW drive -How to test your laptop battery -How to test your Heat sink(s)? -How to test the effectiveness of your fan(s) Favorite answers: OS-independent tests which GUARANTEE the concerned hardware works PERFECTLY |
I am posting this question from my Windows desktop, because as of this morning my laptop is no longer even an internet accessible device, and doesn't even seem to think it's supposed to be an internet accessible device. My OS is Ubuntu 14.04, 64 bit. The laptop is an Asus X551CA, and I got it in 2013 April. Last night, I installed a routine Ubuntu update. I then restarted my computer. This morning, I have no internet. Like, at all. When I open up Firefox, every single tab says it failed to load the requested page. At the top right corner of the screen, there isn't even an internet icon. I tried connecting my ethernet cable, but it didn't even react at all. I tried restarting like three or four times. It doesn't help. The internet is still missing. I tried the following terminal commands, as suggested by responders to . sudo service networking restart sudo service networking force-reload sudo dhclient sudo apt-get update Each one returned errors. The first one returned this. stop: Job failed while stopping start: Job is already running: networking The second one returned this. reload: Job is not running: networking The third one returned this. avahi-daemon stop/waiting And the fourth one, after spitting out a large wall of text, then returned this. W: GPG error: http://deb.opera.com stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 63F7D4AFF6D61D45 I have no idea what to do. It's the very end of the semester, and I have a research project that I need to complete by the end of monday. So it is, to say the least, absolutely imperative that my internet be working soon. Please, please help. | When I started my laptop, there was no network service, and also no network icon in the top bar. It gives an error when I start OS like "Sorry, Ubuntu 14.04 experienced an internal error". When I click details, it says the error is occurred in the executable path usr/sbin/NetworkManager. Also, when I try to enter Network in the System Settings, it says "the system network services are not compatible with this version" How can I solve this shocking issue? p.s. I didn't install any third party packages/apps related with networking. Only system updates are installed. |
Let $f$ continuous at $[0,2]$ with $f(0)=f(2)$.Check if there are $x_{1},x_{2} \in [0,2]$ such that $x_{1}-x_{2}=1$ and $f(x_{1})=f(x_{2})$ . How can I do this? | Let $f \in C[0,1]$ and $f(0)=f(1)$. How do we prove $\exists a \in [0,1/2]$ such that $f(a)=f(a+1/2)$? In fact, for every positive integer $n$, there is some $a$, such that $f(a) = f(a+\frac{1}{n})$. For any other non-zero real $r$ (i.e not of the form $\frac{1}{n}$), there is a continuous function $f \in C[0,1]$, such that $f(0) = f(1)$ and $f(a) \neq f(a+r)$ for any $a$. This is called the Universal Chord Theorem and is due to Paul Levy. Note: the accepted answer answers only the first question, so please read the other answers too, and also this answer by Arturo to a different question: This is being repurposed in an effort to cut down on duplicates, see here: . and here: . |
Okay so basically, what I want to do, is convert the decimal part of number(678.5123) which is 0.5123 into a whole number(5123). However, if you run the code yourself, you'll see that it stops and it outputs 51229999999 etc. Basically, it's wrong, and I don't know why. Any insights as to where I screwed up and why would be very much appreciated. #include <stdio.h> #include <math.h> int main() { int omg, numTimes = 10; double thisIs, holderThis, number = 678.5123; thisIs = number - floor(number); printf("%lf\n", thisIs); int x = (floor(thisIs) == thisIs); while (x != 1) { x = (floor(thisIs) == thisIs); thisIs *= 10; printf("%lf %lf\n", thisIs, floor(thisIs); } while(number - floor(number) != 0) number *= 10.00; printf("%lf", thisIs); return 0; } | Consider the following code: 0.1 + 0.2 == 0.3 -> false 0.1 + 0.2 -> 0.30000000000000004 Why do these inaccuracies happen? |
How can I see a read out of my CPU or in general how much my laptop is overheating? I tried this () where all the temperature info is shown when you type "sensors", but I'm not getting anything - I have Ubuntu 14.04 and I don't know anything about it so what can be the problem? I also noticed I can't run new programs like Blender (donloaded as as ZIP so it doesn't require instalation). How can I check if I have a limited version of the OS because I believe it shouldn't work like this. Here's the program folder - I'm just plain confused, please help! | How do I get the CPU temperature? |
Given an enum parameter list as PHP string, eg $list = "'A', 'B'" how to verify this is 1) valid and 2) safe? What kind of characters are allowed in an enum? Can I verify this with a regex? | If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example: $unsafe_variable = $_POST['user_input']; mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')"); That's because the user can input something like value'); DROP TABLE table;--, and the query becomes: INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--') What can be done to prevent this from happening? |
Before line break After line break An empty line between two sentences usually gets me a line break without any additional spacing. For some reason, on the second page of the same chapter, there is additional spacing after each line break and also more spacing after \\. Why is that? Is TeX somehow trying to fill the page before the following section? I'd like to constantly have no extra spacing after line breaks and \\. | Here is the thing, I have always used a blank space between paragraphs in order to tell latex that there is a new paragraph. But there is someone I work with very often that keeps using \\ to break a line after a paragraph... This is really annoying so I wanted to know if there is a real advantage of using \\ over just leaving a space. Note that I am not referring to the paragraph environment, but to the simple term paragraph. |
I searched through many discussion on Physics Stack Exchange about "Why observation cause collapse of wave function?" and I am totally confused. Is it already solved by modern quantum physics? I know that the real cause is act of measurement. So collapse of electron wave function is caused by interaction between this electron and photon from detector used for measurement? It sound quite clear for me, that the "interaction" cause collapse, am I right? So where is the catch? Because there are so many discussion about it, some peoples points that consciousness cause collapse... I don't where the real problem is if the answer is so simple: "interaction"? From the other hand, if we send photons to interact with electron, without measuring it, will it still cause collapse? UPDATE, after marking as duplicate: I know that the act of measurement cause collapse of wave function. Basically measurement means probing sample electron with photon and that interaction cause collapse, am I right? So what about other particles in environment, will those particles cause wave function collapse? Going one stop further: In double slit experiment with electron, if we don't measure electron state but rather than that we interact with if via laser - bombard it with photons, still there are no measurements! Will it cause collapse of electron wave function? | In one of the first lectures on QM we are always taught about Young's experiment and how particles behave either as waves or as particles depending on whether or not they are being observed. I want to know what about observation causes this change? |
We already have loads of prior duplicate data in our salesforce.com records. Say close to 5000 among 100000 records . Our new requirement states to prevent any new data being saved as another duplicate to 100000 ones that are already existing. I tried using a workflow, but only duplicate data to ones created after the work flow is getting prevented, isn't working for the ones prior. Also we have fields A and B to be jointly unique for this to be a duplicate. Suggestions are welcome. | I need to see an apex code of trigger, on say object 'Account' to prevent any new records from saving. Existing records do have duplicates but we cannot clean/ remove the data, as the requirement has come midway. The unique feature applies to 2 fields say A(picklist) and B(text) of object Account, (concatenated) where A is a picklist, having values 1,2,3,4 where we need only values (TEXT) 1,2,3 of A to be unique alongside (concatenated with) text field B, and not the value 4. Again, the requirement is to prevent any new records from saving which match any of the existing records. Duplicates within the existing records can be ignored. Thanks in advance. |
How is free body diagram of a block on an inclined plane different than that of a vertical circle (string connected to a block doing circular motion in vertical direction) and a banked road Because there are two types of results in both cases:- T(tension)/N(Normal Reaction) cos [some angle]= mg And Mg cos[some angle]= N/T !() | Normally, if an object of mass $m$ is inclined to the horizontal at an angle $b$, we set the reaction force of the object on the inclined plane as $R = mg\cos{b}$ (if we resolve the force of gravity so the line of action coming out of the plane is perpendicular to it). However in circular motion*. it's assumed that $R\cos{b} = mg$. In the example above, one would have to do this in order to arrive to the correct answer, instead of $R = mg\cos{b}$. Using $R = mg\cos{b}$ seems natural enough, as I am resolving vertically, however, both equations would produce two different values for $R$. Why is this? To show what I mean: If we set the reaction force in this question as $mg\cos{a}$, then the centripetal force will be $mg\cos{b}\cos(\pi/2-b) = mg\cos{b}\sin{b} = \frac{1}{2}mg\sin(2b)$ Whereas If we use $R\cos{b} = mg$, $R = mg\sec{b}$ and the centripetal force will be $mg\sec{b}\sin{b} = mg\tan{b}$. This will end up with two different values for the radius of the circular motion, and hence two different final answers. *In the circular motion questions I've seen in my mechanics module |
Is somehow possible to run Ubuntu with both graphics cards like in Windows ? I tested Linux Mint and he recognized both graphic cards and at details about my computer it was showing them both, but in Ubuntu only shows Intel (integrated).I like Ubuntu and I wish I could use both cards on it because I need power on video and photo editing. I apologize if the question is stupid, I'm new in the Linux world. My computer (Acer 5755g from 2011) details are : Procesor : Intel® Core™ i5-2410M CPU @ 2.30GHz Ram : 8 GB Video : Nvidia 540m 2gb and Intel (integrated) Hdd : 650 GB. OS : Ubuntu 13.04 the 64 bit version. | I am considering buying a Dell XPS 15 laptop. The laptop has a Nvidia 420m card which should work with Linux but I keep reading that the Nvidia Optimus technology isn't supported on Linux. I am not really interested in switching from Nvidia to Intel to save power but need to know that the Nvidia card will in fact work if I installed Ubuntu. If anyone has experience using a Nvidia card with Optimus technology or even better the exact laptop in question (Dell XPS 15 with 1GB NVIDIA® GeForce® GT 420M) it would be great. A major problem holding people back from adopting Linux is this sort of hardware issue. I am a long term Ubuntu user and supporter who can't afford to make a mistake with a purchase like this. I don't want to spend £500+ to find I have no graphics acceleration because Windows 7 is not an option. |
I occasionally open an incognito window on my just to check if there are any interesting questions on tags I have ignored. Today a large number of negatively-scored posts have been edited, and when I visited the homepage I saw only 3 posts, instead of the expected 15 (see image below). Checking against the most recently active questions page, these 3 are the only non-negatively rated questions in the most recently active 15 questions. Does it make sense to filter out the negative questions after picking the set of 15? It seems counter-intuitive to me, and I would instead expect to see the most recently active 15 questions that are not negative. (It also doesn't look great to show a potential new user just 3 questions; the site looks a bit abandoned.) | At the moment questions on the homepage are loaded by the top N most recent and then ones with a score of -4 or less are filtered out. This doesn't make much difference for a user who is logged in but consider anonymous users; their home page is only 15 questions in length. If someone was to edit several posts that bump to the top with a score of -4 or less then the home page looks tiny. At the moment on SFF, for example, the homepage for anonymous users only shows 9 questions: At one point it only showed 3 questions (a few weeks back): Can the filtering logic be changed to before the questions are loaded to appear on the homepage? |
I am on the bash shell and I want the output of a command to appear directly in the command prompt that appears after the command has executed ! Example of what I envision it, to illustrate my idea: locate create_tables.sql|MAGIC_command user@localhost:~# /usr/share/doc/phpmyadmin/create_tables.sql Now, using comman dsubstitution like this sudo $(locate create-tables.sql) works but immediately executes the output, I'd like to be able to edit it before. Is there a way? | I managed to do this echo -n "command" > /dev/tty1 The letters appear, and the cursor moves, but they are "ghosts" – if you hit Enter, nothing happens (they are not in stdin). Edit: In the middle of the below screenshot, you see why I see the use of this. (The line with a red caption, right below the line with a yellow caption.) As it is now, you are not really "editing" the note text; you are just asked to write a new text, which will replace the text of the note you are (not really) editing. Thus, I thought it could be remedied by simply pasting the old text into the tty: if the user hits enter, no modification is made. (This program is in Perl/MySQL, but I thought it would be more interesting to ask for a general solution than "how do I do this in Perl".) Edit 2: Here is the Perl code, that uses the C code below (works exactly as intended), as well as a new screenshot – hopefully this will clarify things beyond doubt :) Again, look at the middle of the screenshot, where the edit is made to the note text - this time around, the old text is there, for example if you just wanted to fix a typo, you won't have to retype the entire note text. my $edit_note_text = $edit_note_data[2]; print BOLD, RED, " new text: ", RESET; system("writevt /dev/tty \"$edit_note_text\""); my $new_text = <$in>; $new_text = fix_input($new_text); my $set_text = "UPDATE notes SET note = \"$new_text\" WHERE id = $edit_note_id"; $db->do($set_text); |
If a system requires a patch that I found upstream, how can I tell which version of an Ubuntu package contains the commit that includes that patch? | Let us consider the example of Clang. ABI compatibility of Clang diverged from GCC5 and compiling things with Clang became quite a challenge in Ubuntu 16.04. At some point, . Clang 3.8 is also available in Ubuntu repos, and when I add myself and update source list and try to install Clang-3.8, the version from Ubuntu repos gets installed as the latest (apt is set to always prefer the highest version). Without trying to compile code with it to see what happens, is there a good way to check if that patch is already in the Ubuntu repos or not? |
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