So I am trying to understand c++ and so far it has been a hell of a ride! but still fun. I have created a class student and I am trying to create a generic linklist class. In my node class which is supposed to be generic to any data type, I have defined it as such:  **header** #include <iostream> using namespace std; template<class T> class Node{ private:    T *data;   Node *next,*prev; public:   Node(T*);  }; **cpp** #include "node.h" template<class T> Node<T>::Node(T *data){  this->data = data;  next = 0;  prev = 0; } **main** #include "student.h" #include "node.h" int main(){  Student *s = new Student("student",123);  Node<Student> *node = new Node<Student>(s); }   but then I get what I believe it is a linker error which says:  "undefined reference to 'Node<Student>::Node(Student*)"   The following is my Makefile:  output: node.o student.o main.o         g++ node.o student.o main.o -o output node.o: node.h node.cpp         g++ -c node.cpp student.o: student.h student.cpp         g++ -c student.cpp main.o: main.cpp         g++ -c main.cpp clean:         rm *.o output   This should be fairly simple, but there are some concepts that I am missing. I have a Java background and there are so many things you just don't notice like I am noticing in c++. Thanks in advance.

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


I think this is a basic question, but it's hard to wrap my head around.

I thought about it for a long time, but I can't come up some good ideas. I think that empty set has no elements,how to use the definition of an open set to prove the proposition. The definition of an open set: a set S in n-dimensional space is called open if all its points are interior points.


I'm very stuck on this question, I'm not sure where I'm supposed to start. Any help would really help

Let $X\sim N(\mu,\sigma^2)$. Show that $Z=\frac{X-\mu}{\sigma}\sim N(0,1)$ using moment generating functions. \begin{align*} M_Z(t)&=M_{\frac{X-\mu}{\sigma}}(t)\\ &=M_{X-\mu}\left(\frac t\sigma\right)\\ &=e^{-\mu t}M_X\left(\frac t\sigma\right)\\ &=e^{-\mu t}\cdot e^{\frac{t\mu}{\sigma}+\frac{t^2}{2}}\\ &=e^{-\mu t+\frac{t\mu}{\sigma}+\frac{t^2}{2}} \end{align*} I'm not sure how to conclude that $Z\sim N(0,1)$.


I'm trying to update an existing Subscriber in the All Subscriber Table through the API; i've set up the AppId in the App Center and have connected and created Subscribers, but i'm still having issues updating.  What call do I need to be making to do this? These are the ones i've been trying.

Currently, we use Subscriber key= Email Address = Contact Key; We are planning to use Salesforce Contact ID as Subscriber key/ContactKey. Is there a way to mass update Subscriber key value for all our current Subscribers (we have around 250k subscribers)? Also, will we lose all the tracking data about our subscribers? We are mostly concerned about Einstein Optimization data, but we are not sure if Einstein tracks and stores the data based on the Subscriber Key or email address?


The way to earn the 'Analytical' badge is: Visited every section of the FAQ (retired). What does (retired) mean? Does it mean that it is no longer available?

After seeing the Analytical badge, I visited every page in the FAQ.  I waited a few days, then came here to see if I could find any questions about why it never showed up in my profile.  It was then that I read that the badge was no longer working as of June 2013 (I must have missed this by DAYS, darn it!) due to the Help page restructure.    Since the badge is no longer being awarded in the future, but has been awarded in the past, maybe a designation of "(Retired)" next to it might eliminate some confusion?  I think there's another badge that was only given out in Beta that probably deserves that designation as well.  Just a suggestion.


If spellcaster A readies an action to cast time stop as soon as spellcaster B casts time stop, then on spellcaster B's turn they cast time stop, what happens? Who takes extra turns first? Also, can whoever goes first counterspell the other's time stop, and does doing so end their time stop early?

As  suggests, there seems to be a hole in the D&D Basic rules.  Maybe.  The rules for readying an action state:     When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger.   This seems to imply that it is impossible to interrupt a spell in 5e.  If you set your trigger to be "I attack the Wizard when he casts a spell", then you make the attack after the spell has been cast.  Does this mean that spells can no longer be interrupted in combat like they could be in previous editions?


Pro members of stack community have great knowledge to answer most of the queries which are asked by users. Not only I want to subscribe to their every answer and comment they upload I also want to message them if I want a specific answer. Neither of the feature is available.

There has been quite a few times that I wished I could send a message to another user on SO - not ask a question for everyone to see, but just a short message informing them of something or requesting them to do something.  Are there any plans to allow this to happen in the future?  Related:


Maxwell's equations don't seem to have any delay between changes in electric field and changes in the magnetic field.  So, do Maxwell's equations predict light instantaneously reaches a point one light-year away from the source (I think light takes one year to reach that point).  Or, in other words, do Maxwell's equations predict the speed of causality?  I understand the electromagnetic wave oscillates at the velocity $c = \frac{1}{u_0c_0}$, but Maxwell's theory seems to predict that if I flip on a flashlight and there are no obstructions, the light can immediately be detected one light-year away.  For example, the wave function for the electric field is $g(kx-wt)$ for some function $g$. So, at any time $t$ for all distance $x$ the electric field is changing, which seems to violate the speed of causality.  Perhaps, Maxwell's equations do not predict the speed of casuality, and we need to use more advanced theories (I'm guessing relativity) to predict this. I would like to know  if this is the case.  Could anyone tell me (maybe, in the comments) how this is a duplicate question?

I've been told that, from Maxwell's equations, one can find that the propagation of change in the Electromagnetic Field travels at a speed $\frac{1}{\sqrt{\mu_0 \epsilon_0}}$ (the values of which can be empirically found, and, when plugged into the expression, yield the empirically found speed of light)  I'm really not sure how I would go about finding $v = \frac{1}{\sqrt{\mu_0 \epsilon_0}}$ simply from Maxwell's equations in the following form, in SI units --  $$\nabla \cdot \mathbf{E} = \frac {\rho} {\epsilon_0}$$  $$\nabla \cdot \mathbf{B} = 0$$  $$\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}} {\partial t}$$  $$\nabla \times \mathbf{B} = \mu_0 \left( \mathbf{J} + \epsilon_0 \frac{\partial \mathbf{E}} {\partial t} \right)$$  Is what I believe true? (that the speed of propagation is derivable from Maxwell's Equations)  If not, what else is needed?  If so, can you provide a clear and cogent derivation?


I need a regex that will accept only digits from 0-9 and nothing else. No letters, no characters.  I thought this would work:  ^[0-9]   or even   \d+   but these are accepting the characters : ^,$,(,), etc  I thought that both the regexes above would do the trick and I'm not sure why its accepting those characters.  EDIT:  This is exactly what I am doing:   private void OnTextChanged(object sender, EventArgs e)     {     if (!System.Text.RegularExpressions.Regex.IsMatch("^[0-9]", textbox.Text))         {             textbox.Text = string.Empty;         }     }   This is allowing the characters I mentioned above.

I haven't used regular expressions at all, so I'm having difficulty troubleshooting. I want the regex to match only when the contained string is all numbers; but with the two examples below it is matching a string that contains all numbers plus an equals sign like "1234=4321". I'm sure there's a way to change this behavior, but as I said, I've never really done much with regular expressions.  string compare = "1234=4321"; Regex regex = new Regex(@"[\d]");  if (regex.IsMatch(compare)) {      //true }  regex = new Regex("[0-9]");  if (regex.IsMatch(compare)) {      //true }   In case it matters, I'm using C# and .NET2.0.


I've hardly played any D&D, and I'm about to act as a group's DM very soon. I've been doing my 'homework' of course, but I'm running out of time and have difficulties grasping some concepts still.  To the actual question:  Do I combine assets from one's Class with one's Background? When looking into the Class and Background sections while creating a character, you are entitled to some assets.  For example, if I was to create a Bard I am entitled to "(a) a lute or (b) any other musical instrument", and as a character with an "Entertainer" Background I am entitled to "A musical instrument (one of your choice)". So do I get two instruments, or just one?  Thanks, I know this is an awfully noobish question.

I went into character creation assuming yes, but I feel like I'm overdoing it. If I'm doing this right, my Half-Elf Cleric (Nature) with Acolyte Background has:   Two Holy Symbols (from Cleric and Acolyte) Proficiency in seven skills. Fluency in five languages.   I'm just going with my gut here, but something doesn't feel right. When I designed a Tiefling Warlock a while back, I only had two languages and 4 skill proficiencies.  Am I doing something wrong?


I've been dabbling with linear Diophantine equations and came across a rather interesting pattern that I would like to conjecture as true but I have no idea how about to come up with a proof.  Let $ax+by=c$ be the linear Diophantine equation such that $gcd(a,b)=1$. Obviously $1|c$ so there are solutions to the equation. If we consider only positive solution pairs (x,y) for the equation, then the number of ordered pairs that satisfy the equation is equal to (c/a)/b, rounded down to the nearest integer.  Can anyone verify this by counterexample or by proof? Thanks

Given a linear Diophantine equation, how can I count the number of positive solutions?  More specifically, I am interested in the number of positive solutions for the following linear Diophantine equation:  $3w + 2x + y + z = 47$  Update: I am only interested in non-zero solutions.


18.04.1 LTS installed. Latest bluez Bluetooth drivers installed. Lenovo AIO Y910. Bluetooth was working and after a wake after a suspend Bluetooth option to turn it on is greyed out and it says that no bluetooth hardware found and use a dongle. Any ideas?

Bluetooth earphones work fine until sleep. After resuming from sleep however, they appear to connect for a brief moment before disconnecting. On blueman, the error given is Resource temporarily unavailable. This issue arose only after updating to 18.04 LTS.   Here's the terminal output for lsusb:  Bus 001 Device 002: ID 8087:8001 Intel Corp.  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 002 Device 004: ID 1bcf:0002 Sunplus Innovation Technology Inc.  Bus 002 Device 003: ID 04f2:b477 Chicony Electronics Co., Ltd  Bus 002 Device 002: ID 0a5c:21f1 Broadcom Corp. HP Portable Bumble Bee Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub


Good examples would be writing "nite" for "night", "4" for "for", "wimmin" for "women". I guess it also applies to substituting final s with "z", as in "wordz". In the way that . Recently I've seen it a lot in alternative literature and music.  Example sentence: "Nice ... in that album title 'Only Built 4 Cuban Linx'"  I can't find them under . Which is odd, because this sort of rhetorical device seems to me currently more popular than, for example, .  These stylistic devices are different from , in that these are informal contractions, coming from "natural" speech acts like slurring. This question is about deliberate misspelling for artistic or satiric effect.

For example,      Night -> Nite   Through -> Thru   The -> Da   Though -> Tho     Nite even appears in some dictionaries as having the same meaning as night.  What is it called when words are deliberately written incorrectly but the pronunciation and meaning are kept unchanged?


I came across this question in the book Challenge and Thrill of Pre-College Mathematics:     Prove that $\sqrt{2}$ is irrational using induction.   Apart from the fact that this is hardly the usual method for proving this, I have no idea even how to begin. What am I supposed to used induction on?  I suspected that I might use induction to attempt to prove that the decimal places of the expansion of $\sqrt{2}$ do not repeat themselves, but even that seems to elude me. Perhaps we can use induction to prove that there does not exist any rational number which can be $\sqrt{2}$?  Since I am fairly inexperienced in number theory (I'm currently self studying it in high school) please keep in mind  that I know only very basic theory such as some prime theory, modular arithmetic and basic properties of the GCD, etc. I would also ask you to refrain from giving a detailed solution; I would prefer a hint with which I can complete the proof.

How do I prove that the square root of 2 is irrational using the principle of mathematical induction?


trigger populateContactEmail on Case (before insert , before update){ Set<Id> setConIds = new Set<Id>();  for(Case  obj : trigger.new){     if(obj.Secondary_Contact__c != null)         setConIds.add(obj.Secondary_Contact__c); }  Map<Id , Contact> mapCon = new Map<Id , Contact>([Select Id, Email from Contact where id in: setConIds]); for(Case obj : trigger.new) {     if(obj.Secondary_Contact__c != null)     {         //Protecting against bad Ids         if ( mapCon.containsKey(obj.Secondary_Contact__c)) {             Contact c = mapCon.get(obj.Secondary_Contact__c);             obj.Secondary_Contact_Email__c = c.Email;         }     } }   }

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  This canonical question is intended to address several classes of common questions by providing a quick summary and links to comprehensive resources:   How do I start writing my first unit test?  How do I unit test this code?  I need help writing this unit test.   Salesforce Stack Exchange looks for detailed, specific questions that the community can help you with, and can't write tests on your behalf. We feel that working with the resources below can help you get started, and we encourage you to make an attempt to write your test and return to SFSE with your specific questions when you encounter challenges you can't resolve.


The word "master" when used in the sense of one thing controlling another thing (as opposed to skill mastery) has become an unword in growing circles. In communities of people who write technical specifications, the concept of one thing (non-human) having control over other things is common. Is there a deanthropomorphized equivalent? Examples:  Master data list -- a primary, singleton, authoritative, commanding list of vendors, accounts, files, etc. which all other lists of same must reference and synchronize to  What I tried:  Authoritative. This word can convey substantially the same meaning. But it is clumsy for having too many syllables for a very common thing: "authoritative vendor list," "authoritative account list". Also it fails to convey active command. You could describe some dictionary as authoritative but you would not say it is commanding. When an entry from a "master data list" is deleted, it is not sufficient that other references to it become invalid, instead every other reference to it must be deleted simultaneously. This is an active change which is propagated by the change above.

I am writing for a fantasy setting, and there needs to be a similar concept of a “master” magician. There is a guild, “apprentice” and “journeyman” still work well, and then there needs to be a step above that for someone who has completed their training. Importantly, a “master” in this sense is just someone who has completed all the training and knows all the things you have to know. They aren’t necessarily the greatest or the best; they’re just just fully qualifed. In its original sense, “masterpiece” just meant something that demonstrated those qualifications, not the greatest work of one’s career (cf. magnum opus). The masterpiece is akin to a doctoral dissertation, a black belt, or what have you—a significant accomplishment, but one that should ideally be the beginning of your career, not its pinnacle. Except there are two problems:  “Masterpiece” is widely used to refer to the pinnacle of one’s career. “Magnum opus” would be better for that, but I can’t change the way people use words. Especially when “master” is paired with “masterpiece,” it leads many readers to thinking the person is among the best in the world, or of all time. I just want someone who is fully qualified and capable rather than a student.  “Master” is currently the subject of debate about its appropriateness, considering the relationship of a master to slaves.   Both of these are problems for me. I would like to avoid them if I can, but to do that, I need a good alternative. So, does anyone have any good suggestions for sentences such as these?    He was an apprentice to the local _____ wizard, Carl.     Upon completing his enchantments and demonstrating the new spell to the guild, she was awarded the rank of _____, able to properly call herself a magician now and sell her spellcasting services.    My goal is to write this story, describe this setting, in such a way that no one has any reason to question the word choice. I want something that captures the meaning I want, doesn’t lead readers astray, and doesn’t lead to anyone feeling uncomfortable or argumentative over something as simple as word choice. If all I have to do to make the story work better for more readers is find another word, I want to find the other word. For the sake of making this a useful question, “master” is off the table. It is patently obvious, I think, that I am aware of it as an option. The purpose of this question is to find other options, so that each may be considered. The word “master” is not an alternative to “master” and is therefore not a valid answer to the question.


I have same problem of this , but I can't comment that because don't have reputation.

I have an account on Stack Overflow and also on Russian Stack Overflow. I can ask questions on Russian Stack Overflow, but it always displays the phrase "Finish registration". I have tried logging in by different methods — Facebook, Google, etc. — but it still says that my registration is not finished. Can someone help me with it? or explain what I should do there to finish the registration?  P.S: I can't write questions in Meta Russian Stack Overflow because it says that my registration is not finished.  P.S.S: I have already tried "Click the "register" link at the top of the page." it brings to the login page with the phrase "Finish signing up by using any of the following options:". I have already tried all options there. I also can't merge them because they already linked.


Well, it seems as if there's no good way to put this (as this question , but ... from the other side of the hill, if that makes sense).  Basically, my question is not about tag creation, but about tag usage or even (god forbid, collective gasp) tag deletion.  Example comparisons: (delineated by spaces)   Flex Flex4 Flex-4 Flex-4.5 Flex4.5 Flex4.5.1 Adobe-Flex Adobe-Flashbuilder Flashbuilder flash-builder   Also consider this dilemma / example:   flash actionscript-3 flash-builder flashbuilder4 [aforementioned flex tags here]    I've found that the only way to get a question regarding Flex to be answered, is to tag it with the following:  Flex Flex4.5 f lash-builder [actual topic of question]  Generally Accepted Problems   Version Tags:   makes "favourite" and "ignored" tags almost useless.  Unless you only know a specific "version" of that programming language (?) gives the question significantly less exposure if the author (in the spirit of not duplicating tags) only uses the language specific tag.    Possible Solutions  Unfortunately, the only solution I can see at the moment is that if versions were (somehow) sub-tags of the actual language tags.  This solution would have serious implementation issues, but it's all I can think of.

I'm getting sick of version numbers in tag names (aka version tags). Look,      I just want them all to be just . They are all about JSF. I browse and answer questions about JSF. I don't want to browse in all those different tags. I don't want gold badges for both  and . I can't hammer a duplicate  question because I don't have a gold badge for that. Across years I observed that a version tag is usually only picked by the asker when a "relatively new" or "relatively old" version is being treated in the question. When the "currently mainstream" version is being treated,  or when the asker is "more proficient" in the language, then askers often just pick the versionless . While moving in time, this may cause confusion by future readers when the version isn't explicitly specified anywhere in the question. I try to maintain them by adding/removing the version tag depending on its relevance, and by adding the versionless tag when it's absent. It only feels a neverending story. I'm sure other tag caretakers also have mixed feelings on this. I propose to normalize the version from the tag name:  Ban version numbers in tag names in the model (not in the UI). Add an optional single-choice version field to the Tag entity in the model. Users with edit privileges (no suggested edits please) must be able to change versions. Users with gold tagbadges must be able to add and edit versions. I'd imagine the version edit thing to be reachable via that tag info popover (when you hover the tag). Tags themselves however should look exactly the same, the version just separated with e.g. a hyphen from the tag name.  When in place, migration of existing version tags should be piece of cake. There's apparently already a script in place which recognizes version tags, it could be reused to re-match current tags and extract the version from it into the new version field. The alternative would be to automatically add the versionless tag when a version tag is being used. But this is IMO only tag pollution.  I'm posting this on meta.se instead of meta.so because version numbers aren't only on SO a problem, but on basically all HW/SW related sites.


Is easy to see that we can solve $a^2 \equiv 1 \pmod{311}$ with $a \equiv 1 \pmod{311}$ and $a \equiv -1 \pmod{311}$ but how do we prove that there is no other solution without doing a table of 311 values of $a$.

Let $p$ be a prime. Show that for all integers $x$, $x^2\equiv 1 (\text{mod} \ p) $ if and only if $x \equiv 1 (\text{mod} \ p)$ or $ x \equiv p-1 \ (\text{mod} \ p ). $    I know that I have to prove this both forward and backward. I'm not really sure where to begin


If nothing can travel at the speed of light and light cannot escape the universe, then the rate of expansion of the universe should be equal to the speed of light, why it is not?

just after the Big Bang and before inflation the currently observable universe was the size of a coin. One millionth of a second later the universe was the size of the Solar System, which is an expansion much much faster than speed of light. Can space expand with unlimited speed?


Normally when I press the "g" key everything is smooth. But suddenly as I was working on my model. Everything is moving very jittery and I cant control anything that is happening. The vertices would jump around the point but wont land at the specific area I want. Is there a way I could fix this?

My cursor is moving by every selection by large increments!  Normally when I use Blender, I am able to select and move objects to any coordinate. Now, all of the sudden, when I select an object or mesh the selection moves by an inch or so in each direction.  How do I reset it to normal?


So I was wondering if manipulating differential as fraction is fine.In Physics problems ,usually, what I see is if we have equations of magnetic field ,we consider a magnetic field caused by a small length dl and the magnetic field is dB and integrating over the whole length.it seems we are treating dB as a infintesimal quantity.However ,after browsing for a while,the answer is that the notation dy/dx is not a infintesimal quantity but rather an operation on the function y.I am confused as to how it is valid in physics to treat it as infintesimal quantities.(After learning it,my notion for physics just got crushed and am now confused).I have not learned multivariable calculus yet,but from the arguments I've read ,I found that interpreting them as fractions does not work anymore.But it seems it works fine when in 2 dimensions.In mechanics when we derive equation for rocket motion (ejecting mass) we interpret differential as small quantities (dm) and divide by small time dt.Sorry for the long story... I am confused right now  TL:DR : In physics ,dy/dx can be operated as if it was a small quantity divided by small quantity,though from what I've read it is not supposed to be a ratio.  When does interpreting them work and when does it not. Any help would be very much appreciated ...

In the book Thomas's Calculus (11th edition) it is mentioned (Section 3.8 pg 225) that the derivative $dy/dx$ is not a ratio. Couldn't it be interpreted as a ratio, because according to the formula $dy = f'(x)dx$ we are able to plug in values for $dx$ and calculate a $dy$ (differential). Then if we rearrange we get $dy/dx$ which could be seen as a ratio.   I wonder if the author says this because $dx$ is an independent variable, and $dy$ is a dependent variable, for $dy/dx$ to be a ratio both variables need to be independent.. maybe?


I was just playing Minecraft the other day and I began to wonder. Are there any easter eggs in Minecraft, and if so, what are they?

I was looking at  and I didn't realize that Minecraft had some Easter eggs in it. Besides the Christmas chest Easter egg, and the sheep Easter egg, what else is there?


I'm creating a program to find the standard deviation of an ArrayList of double values given by the user. I am to provide a string on the command line to indicate whether I want the mean (mean), or the standard deviation (std). However, I am having difficulty giving those strings to the command line.      This is the error I'm getting:  > Exception in thread "main" java.lang.NumberFormatException: For input string: "std"         at java.base/java.lang.NumberFormatException.forInputString(Unknown Source)         at java.base/java.lang.Integer.parseInt(Unknown Source)         at java.base/java.lang.Integer.parseInt(Unknown Source)         at StatDriver.main(StatDriver.java:28)          public static void main(String[] args) {            Scanner input;           ArrayList<Double> data;           int dataSize;           String userInput = "";            // Determine the appropriate array size.           if (args.length > 0) {              dataSize = Integer.parseInt(args[0]);           } else {              dataSize = 15;           }            // Create the array.           data = new ArrayList<Double>(dataSize);            // Read values from the terminal.           input = new Scanner(System.in);           while (input.hasNextDouble()) {              data.add(input.nextDouble());           }            // Calculate and display the results.           if(args[0] == "mean") {               System.out.printf("Mean: %.2f\n", Stats.mean(data));           }           else if (args[0] == "std") {               System.out.printf("StdDev: %.2f\n", Stats.stdDev(data));           }           else {               System.out.printf("Mean: %.2f\n", Stats.mean(data));                }        }     }

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


my physics textbook says that If two bodies stuck together after the collision and move as a single body with a common velocity then the collision is said to be perfectly inelastic collision.  Consider an example,when a mud ball is thrown on a wall, both of them (ball and wall) do not move but both of them stuck together. will this collision be considered perfectly inelastic? Further my teacher said that momentum is conserved in each kind of collision, but i don't see any momentum after the collision of mud ball and wall, hence two cases arises:   My teacher is wrong The system is non-isolated (law of conservation of momentum is applicable to an isolated system)   Where the things went wrong?

Almost in every book on physics, there's an example of conservation of momentum when the ball that is moving horizontally in the air, hits some massive wall. They claim that the return speed of the ball when it bounces off is the same as it was before the hit. If there were no external forces acting on the system (or their net force was zero) that would be fine. But in this case, there is a gravitational force acting on the ball, and because there is no surface underneath it, there's no normal force and therefore it doesn't "cancel out" the gravitational force. So my question is, why they say that the momentum conserved? Do they neglect the gravitational force or what? I'm quite confused.


While going through some source code that heavily mixes C and C++, I came across the following (slightly modified to protect the work of the company, the meaning remains the same):  /*  * Typedefs of void are synonymous with the void keyword in C,  * but not in C++. In order to support the use of MY_VOID  * in place of the void keyword to specify that a function takes no  * arguments, it must be a macro rather than a typedef.  */ #define MY_VOID void   What is the difference between typedef void MY_VOID and #define MY_VOID void in this specific context?    I don't believe this is a duplicate of  because it asks specifically about the implications in regards to function signatures, rather than a much more general "what's the difference".

I have the following code:  typedef void VOID; int f(void); int g(VOID);   which compiles just fine in C (using gcc 4.3.2 on Fedora 10). The same code compiled as C++ gives me the following error:  void.c:3: error: ‘<anonymous>’ has incomplete type void.c:3: error: invalid use of ‘VOID’   Now, this is something in external library and I would like the owner to fix that problem. So I have a question - does C++ standard forbids this construct? Could you give me a pointer/citation? The only thing I can recall is that function declaration with (void) to signal empty parameter list is deprecated in C++, but I don't understand why typedefed VOID does not work.


So, I have a little problem with my website. I have a footer which won't stay at the bottom of the page if I happen to have little or no text on the page, but If i have enough info/text to cover a page or more, then it stays at the bottom nicely!  I've tried many things but can't find the right parameters. Can anyone help please?  Here is the code to it, I've stripped the unnecessary code of my page and left with the main bits that has to do with the footer etc..    Just to let you guys know, I've tried this:  { position: relative; bottom: 0; }   Although that fixes the problem for the footer when there is no text but if there is more text then it sort of stays in the middle (fixed)?  Thanks again.

I have a simple 2-column layout with a footer that clears both the right and left div in my markup.  My problem is that I can't get the footer to stay at the bottom of the page in all browsers.  It works if the content pushes the footer down, but that's not always the case.


I know that the word "infomation" is always singular in English. However, is it grammatically correct to use "are" when refering to sum of different categories of information (e.g., in the following sentence)?  "In this approach, the semantic and location information are obfuscated independently of each other."

Context: I am writing a short text to explain the main differences between Spanish passive sentences with "ser" and "estar", one of which is verb choice: sometimes the adjectival form should be chosen, and sometimes the participle form should. Those are generally the same, but sometimes they differ. The problematic sentence goes like:     Some examples where the participle and the adjectival form differ are: [and a list follows]   In a previous , it was explained that the noun (form) can be either in singular or plural. Because the noun was a general thing, I decided to go with the singular form, but then a verb followed (differ). Now, my question is:    Should the verb be conjugated in third person singular (differs) or plural (differ)?   Common sense tells me that it should be a plural (since there are two forms), but "differ" after "form" doesn't sound right (or does it?). I know I could just change form to forms, but I would like to keep it singular. Besides, I really am interested in knowing how the verb should be conjugated in this kind of phrases when the noun is to be kept in singular.


I learnt that in LASSO regression, there is this $\lambda_{min}$ which is given by  $$\lambda_{min} = \text{max}_j|\sum_t y_t X_{tj}|$$ in which $y$ is the response, $X$ is the matirx of predictors.  So, when you plug this $\lambda_{min}$ into the objective function  $$\text{argmin}_{c \in \Bbb R^{M}} (\Vert y - Xc \Vert_2^2 + \lambda_{min} \Vert c \Vert_1)$$ the vector of regression coefficients $c$ will be a zero vector.  My questions:   What is the intuition of this $\lambda_{min}$? I am not focusing on a rigorous mathematical proof, I just want to intuitively understand this $\lambda_{min}$ so I can use this with more confidence, say for feature selection.  Does this $\lambda_{min}$ apply to other cost function like MaxAE other than squared reconstruction error?    I just learned this $\lambda_{min}$ while reading a research paper. However, I haven't found a definition of this in a textbook. Any references will be appreciated.

I'am trying to derive mathematically the lowest $\lambda$ at which all coefficients are zero, reffering to the Exercise 2.1 of the book .  The result should be $\lambda_{min}=\max_j |X_j^Ty|$. I hope this isnt a duplicate, because it is also discussed . However my math skills are very restricted, so I don't understand the solution. I hope that someone can help me to understand the mathematical details behind the derivation.  The LASSO is defined as:  $\min_\beta \frac{1}{2}||y-X\beta||_2^2 +\lambda||\beta||_1$  My approach was following the KKT-conditions, we get  $X^T (y-X\hat{\beta})=\lambda s$  with $s$ as the subgradient.  $\beta=0$ leads to  $X^Ty=\lambda s \Leftrightarrow \frac{X^Ty}{s}=\lambda$  And here im stucking. How I can get from there to this $\lambda_{min}=\max_j |X_j^Ty| $  EDIT: The Exercise question of the book is: "Show that the smallest value of  such that the regression coefficients estimated by the lasso are all equal to zero is given by"  $\lambda_{max}=|\frac{1}{N}\langle x_j,y\rangle|$  EDIT2: Source of the KKT-Condition


I came across this question on Stack Overflow: , which has one comment by user . I  hovered over his name link and saw that he has just the 1 rep.  In the , Comment Everywhere privileges require 50 rep. Soerium is not OP of question.

On this question on Super User …    … there is a comment:  Yes, it is possible. Check out this question: apple.stackexchange.com/questions/447/… –   The interesting thing is that:  The user has 1 reputation There was no migrated / deleted answer The question itself was not migrated The user is registered The user does not have any associated network account, therefore no network profile The mods .   Why were they able to post a comment?


I'm trying to create an array containing plot elements (from the CircuiTikZ package but it's incidental) some of which writes are on multiple lines . As I want the texts to be centered vertically and horizontally, I went with this code: \documentclass[border=2mm]{standalone}  \usepackage{array,multirow,makecell,hhline} \setcellgapes{1pt} \makegapedcells \newcolumntype{R}[1]{>{\raggedleft\arraybackslash }b{#1}} \newcolumntype{L}[1]{>{\raggedright\arraybackslash }b{#1}} \newcolumntype{C}[1]{>{\centering\arraybackslash }b{#1}} \usepackage[utf8]{inputenc} \usepackage[siunitx, european, straightvoltages, cute inductors]{circuitikz}   \begin{document} \begingroup \makegapedcells \setcellgapes{3pt} \tikzset{every picture/.style={baseline=-0.5ex}} \begin{tabular}{|C{4cm}|C{4cm}|C{3cm}|} \hline Composant & Code & Image résultant\\ \hline amplificateur opérationnel anglo-saxon & node[op amp]{} & \begin{circuitikz}                     \draw (0,0) node[op amp]{};                   \end{circuitikz} \\ \cline{1-3} amplificateur opérationnel européen & node[en amp]{} & \begin{circuitikz}             \draw (0,0) node[en amp]{};          \end{circuitikz} \\ \cline{1-3}    amplificateur opérationnel entièrement différentiel & node[fd op amp]{} & \begin{circuitikz}                         \draw (0,0) node[fd op amp]{};                             \end{circuitikz} \\       \cline{1-3}    amplificateur d'instrumentation & node[inst amp]{} & \begin{circuitikz}                         \draw (0,0) node[inst amp]{};                             \end{circuitikz} \\              \cline{1-3}    amplificateur d'instrumentation avec résistance & node[inst amp ra]{} & \begin{circuitikz}                         \draw (0,0) node[inst amp ra]{};                             \end{circuitikz} \\      \cline{1-3}            \hhline{|=|=|=|}     \end{tabular} \endgroup \end{document}  My problem is that for a line (the 4th), the text is no longer vertically centered but it is placed at the top of the cell (I also have the impression that the vertical centering of the other lines is not not very correct). How can I solve this problem? Thank you

In a document, I would like to vertically align cell text. The only problem is that my array is contained in a begin {circuitikz} so the few tests I was able to do (with begin {center} in particular) don't work. Can you help me ? \documentclass[border=2mm]{standalone}  usepackage{multirow} \usepackage[utf8]{inputenc} \usepackage[siunitx, european, straightvoltages, RPvoltages]{circuitikz} \begin {document}  \begin{circuitikz} \node at (0,0)  {\begin{tabular}{|c|c|c|c|} \hline Type & Composant & Code & Image résultant\\ \hline \multirow{7}{*}{Alimentation} & pile & to[battery1] & \begin{circuitikz} \draw (0,0) to[battery1] (2,0);\end{circuitikz} \\ \cline{2-4}  & source de courant & to[isource] & \begin{circuitikz} \draw (0,0) to[isource] (2,0);\end{circuitikz} \\  \cline{2-4}  & source de tension & to[vsource] & \begin{circuitikz} \draw (0,0) to[vsource] (2,0);\end{circuitikz} \\  \cline{2-4}  & source sinusoidale & to[sV] ou to[vsourcesin] & \begin{circuitikz} \draw (0,0) to[sV] (2,0);\end{circuitikz} \\  \cline{2-4}  & source sinusoidale & to[sV] ou to[vsourcesin] & \begin{circuitikz} \draw (0,0) to[sV] (2,0);\end{circuitikz} \\  \cline{2-4}  & source créneau & to[sqV] ou to[vsourcesquare] & \begin{circuitikz} \draw (0,0) to[sqV] (2,0);\end{circuitikz} \\  \cline{2-4}  & source triangulaire & to[tV] ou to[vsourcetri] & \begin{circuitikz} \draw (0,0) to[tV] (2,0);\end{circuitikz} \\  \hline \end{tabular} }; \end{document}


Given a 7 sided dice, 2 players roll it independantly simultaneously and when a player rolls a '6' he gets a prize.  What is the probability of the first player getting a prize before the second?  So my solution is to sum over all the turns j in which player 1 could win, and make the second player lose all these turns:  $$P(A) = \sum_{i=1}^{\infty}(6/7)^{j-1}*(1/7)*(6/7)^j = 0.461$$ My question is if my solution is correct, and if so, why is the probability so low? It seems to me that either player 1 wins before the 2nd or the other way around, and the probability of them playing forever is 0, so it should be 0.5?

Question: Players A and B play a sequence of independent games. Player A starts and throws a fair die and wins on a "six". If she fails then player B throws the same die and wins on a "six" or fails otherwise. If she fails then player A gets the die and throws again, and so on. The first player to throw a "six" wins. Find the probability that player A wins.  Here is what I have done:  A wins right away: $\dfrac{1}{6}$  A fails B wins: $\dfrac{5}{6}\times \dfrac{1}{6}$  A fails B fails A wins: $\dfrac{5}{6}\times \dfrac{5}{6}\times \dfrac{1}{6}$  Unlike another similar question which the player B can win on "five" and "six" after player A fails on the first throw, in this case, the games do not seem to have an endpoint. How should I calculate the probability that player A wins then?


My friend is staying with me in the United States for 2 months. He is visiting me from Japan. He wants to work for Japan while being a tourist here to help me pay the bills. He found an online job, which is located in Japan. Can he do this online job while physically present here in the United States, for Japan, get money deposited into his account from the company physically present in Japan, and then use that money here inside the United States without breaking any employment laws?

I would like to travel in the USA for a period of 3 - 6 months. But I want to spend some time working for my employer (remote work) and getting paid by the employer. Is this possible under a tourist visa (B1/B2)?  I hope this is OK since I will not be getting paid by a US employer. I am in the IT trade so all that I will be needing is my own laptop and a connection to the internet. The money I earn would actually help me pay for the expenses I get during the holiday.


I have a comma-separated file which has numeric and string columns. String columns are quoted and can have comma in between the quotes. How do I identify the columns with FS =","?  Sample records  "prabhat,kumar",19,2000,"bangalore,India"   In  it should be  $1 = "prabhat,kumar" $2 = 19 $3 = "2000" $4 = "bangalore,india"   Setting FS="," is creating the problem.  Input is:  "prabhat,kumar",19,2000,"bangalore,India","ABC,DEF","GHI",123,"KLM","NOP,QRS" "prabhat,kumar",19,2000,"bangalore,India","ABC,DEF","GHI",123,"KLM","NOP,QRS"   Output should be:  "prabhat,kumar"|19|2000|"bangalore,India"|"ABC,DEF"|"GHI"|123|"KLM"|"NOP,QRS" "prabhat,kumar"|19|2000|"bangalore,India"|"ABC,DEF"|"GHI"|123|"KLM"|"NOP,QRS"   Code I am trying:  awk -F"," '{for(i=1;i<=NF;i++){if(i%NF==0){ORS="\n"} {if($i ~ /^\"/ || $i ~ /\"$/) {a=a OFS $i;j++;{if(j%2==0){sub(/^\,/,X,a); print a;j=0;a=""}}} else {print $i}}} {ORS="|"}}' ORS="|" OFS=, p.txt

I work with CSV files and sometimes need to quickly check the contents of a row or column from the command line.  In many cases cut, head, tail, and friends will do the job; however, cut cannot easily deal with situations such as  "this, is the first entry", this is the second, 34.5   Here, the first comma is part of the first field, but cut -d, -f1 disagrees. Before I write a solution myself, I was wondering if anyone knew of a good tool that already exists for this job.  It would have to, at the very least, be able to handle the example above and return a column from a CSV formatted file.  Other desirable features include the ability to select columns based on the column names given in the first row, support for other quoting styles and support for tab-separated files.  If you don't know of such a tool but have suggestions regarding implementing such a program in Bash, Perl, or Python, or other common scripting languages, I wouldn't mind such suggestions.


How can we get the list of user those who have the read permission on the Case sObject?

Since I couldn't think of how to write this query off the top of my head, I thought it might be worth sharing. How can I query which Profiles have Read permission on a specific object? I knew it would have something to do with ObjectPermissions and PermissionSet, but had to look up the documentation for both to piece it together.


In  it says that an offside-positioned player is penalised for offside if they have considered to have gained an advantage by      by playing the ball or interfering with an opponent when it has:         rebounded or been deflected off the goalpost, crossbar, match official or an opponent   been deliberately saved by any opponent      If a defender attempts to intercept a ball that has been played to an offside-positioned attacker who is through on goal, but miskicks it directly into the attacker's path, does this count as a deliberate save?  If this is the case, is the attacker penalised for being in an offside position?

I was refereeing a 10 year old's junior game today and this situation happened. The home team's defender attempted to  pass from their own half to their forward who was in an offside position beyond the halfway line.  I was going to blow the whistle but the ball deflected off an away defender and then went to the originally offside attacker who put the ball wide.  I viewed this as onside at the time because the ball struck the away team player, however now I think it was offside because at the time of pass, the home player was offside.  Is this offside or not?


let $f:[-1,1]\to \mathbb{R}$ be a continuous function such that $\int_{-1}^{1}f(t)dt=1$ then find $\displaystyle \lim_{n\to \infty} \int f(t) \cos^2nt   \mathrm{d}t$. My method: I have solved the problem by choosing $f(t) =\frac12$. And the answer I get is also $\frac12$. But I want to know, without choosing this type of example, is there any other general proof? Thanks in advance

Given that $f\colon [-1,1] \to \mathbb{R}$ is a continuous function such that $ \int_{-1}^{1} f(t) \ dt =1$, how do I evaluate the limit of this integral: $$\lim_{n \to \infty} \int_{-1}^{1} f(t) \cos^{2}{nt} \,dt$$   What I did was to write $\cos^{2}{nt} = \frac{1+\cos{2nt}}{2}$ and substitute it in the integral so that I can make use of the given hypothesis of $\int_{-1}^{1} f(t) \ dt =1$. So the integral becomes,   \begin{align*} \int_{-1}^{1} f(t)\cos^{2}{nt} \ dt = \int_{-1}^{1} f(t) \biggl[\frac{1+\cos{2nt}}{2}\biggr] \ dt  &  \\  \hspace{3cm} = \frac{1}{2}\int_{-1}^{1}f(t) \ dt + \int_{-1}^{1} \frac{f(t)\cos{2nt}}{2} \ dt \end{align*}  But I don't really know how I can evaluate the second integral and also I can't realize as to why that integral condition on $f$ has been assumed. Moreover without assuming that condition on $f$ is it possible to evaluate this integral? If yes, then what would the answer be?


On a mac, when you enable 'Other' on the login screen so that network accounts can log in, the large circular image that comes along with it is a gray silhouette of three heads.  Where is this image on the hard drive?  I'd like to swap it out with something else.

In Mac OS, when you have your login screen configured to show a list of users (as opposed to a username/password text box combo), each user is accompanied by a large circular image.  This is alternately known as a 'User Picture' or a 'Login Picture'.  All users have such an image even if they are the generic gray silhouette image.  Furthermore, when you enable network users to log into your mac, and have the login screen configured to show a list of users, the User Pic that accompanies the 'Other...' user is a special login picture, which is a gray silhouette of three individuals, like so:    I would like to change this image so that I can have a more fun picture for the students in my school to click on when they want to login with their network account.  I do not know how to do this.  One idea I had, and it was admittedly something of a brute force idea, was to find that image on the hard drive and replace it with a picture of my choice.  The image seems to be this one:  /System/Library/CoreServices/CoreTypes.bundle/Content/Resources/Everyone.icns   However, overwriting that file with a normal image had no effect on the login screen, so I am thinking that either, 1. that isn't really the file being used, or 2. it is the correct file but something else needs to change in addition to over writing it with a different image.  To clarify: I am solid on changing the user picture for normal users and I have a script in place already to do so. I do not need help with that.  It is the 'Everyone' image, or the gray silhouette of three heads, that accompanies the 'Other...' prompt on the login screen that I would like to change.  The "Bounty Goal" is to replace the 'everyone' image on the login screen with one of my choosing.  This is not the same thing as providing a login pic for an individual who has signed in by clicking on the Other link.  Thanks in advance for solving this!!


Let $N$ be a cyclic normal subgroup of a group $G$ and $H$ is any subgroup of $N$.      Prove $H$ is a normal subgroup of $G$     Guessinng that exists $a\in G$ where $\langle a\rangle=N$ of some order.  $H \subset N$, $ H$ is a subgroup of $N$.  $gH =Hg \equiv g h_1 =h_2 g \equiv g a^{k_1} =a^{k_2}g $.  *Not sure  if on the right track just spit balling *

Exercise 11, page 45 from Hungerford's book Algebra.     If $H$ is a cyclic subgroup of $G$ and $H$ is normal in $G$, then every   subgroup of $H$ is normal in $G$.   I am trying to show that $a^{-1}Ka\subset K$, but I got stuck. What I am supposed to do now?  Thanks for your kindly help.


Yesterday I came across the following sentence, using "french" fries in lowercase, in an exercise book for non-native speakers of English:  We ordered two "french" fries and two apple pies.  So I have googled "(f)rench fries" in lowercase. To my surprise, l have found out that both styles are used, lowercase and uppercase. My question is: which style is more appropriate in formal writing?

Is the "B" in Brussels Sprouts capitalized?  What about the "F" or "F's" of French Fries?  I suppose it's not standard to capitalize "F" in french fries... In that case what is the proper way to write it? Please cite sources.


When I get connected to internet then I open system monitor to track the speed and total uploads and downloads. When I get disconnected and then connected to the network then in system monitor the total uploads and downloads is started from 0. Is there any way by which I can make it continue it to run and according to my need I can refresh it any time I need.    Kidly help me. If what I need cannot be accomplised by system monitor then if possible then provide an alternative option. Thanks.

I have only one minute system monitoring in my current setting.  I would like to have longer scale.   How can you have longer timeline of network history in 14.04?


how you can show the total page number of your document in the footer on each page, i.e. show a “page # of ##” instead of the default “page # of #”. However, , it does not explain how to do that in a KOMA class. It has been suggested to ask a new question. I use scrlttr2 for a letter, so I'd like to do the same. So how can I do it there?

I saw the answers to a , but the accepted answer won't take effect in a KOMA-script class.   \usepackage{lastpage} ... \cfoot{\thepage\ of \pageref{LastPage}}    I am using scrartcl and lastpage. The default page numbering is just the page number itself. I want it to be currentPage / totalPages. How do I modify it?


In the following sentence:     Furthermore, the tools require intensity data provided by an external software which, along with possible file conversion, increases the total execution time.   Should increase(s) be singular or plural?

I was interested in the following sentence which appeared in a   in The Washington Post, Politics, (WHO RUNS GOV).     She, along with Mark Childress, were set to be Daschle's deputies at   the White House before he stepped down.   Can someone clarify if the fragment "She, along with Mark Childress, were set to" is ungrammatical, as I think it is?  I would reword were with was because I think that the subject of the sentence - obviously, in grammatical terms - is "She", not "She" and "Mark Childress", but I'm not sure on this correction.  More precisely, I'm not so sure that "She, along with Mark Childress" is equivalent to She and Mark Childress with regard to the effects on the grammatical numbers.


I have borehole data (x, y, z values for each subsurface measurement, and its associated lithology). I would like to interpolate the borehole data to create 1) interpolated subsurfaces and 2) lithological profiles at specific cross-sections. I only have access to the ArcGiS package w/ extensions, but no other software packages, nor the budget to access them.   I need to know if the above is possible with the tools and data that I have, and if so, what tools and methodology I should be looking into.

I am working with lithological data, where I have multiple z depths for one set of coordinates. How is this read by the raster interpolation toolset? Does it utilize only one or all of these z values?  If it does not recognize multiple values, is there a type of interpolation I can use that can?   My ultimate goal is to create something in ArcScene that has a 3D appearance and can demonstrate the profundity of a certain lithology.


My tags are follows:  \documentclass{book}  \usepackage{showframe}  \usepackage{gb4e,qtree,skull}   \begin{document}  \begin{exe} \ex\emph{Superiority-obeying and Superiority-violating multiple \emph{wh}-questions} \begin{xlist} \ex {\textit{Which} student read \textit{which} book? } \ex {{\em Which} book did {\em which} student read ?} \end{xlist} \end{exe}  \end{document}   and the output came as:   How can I get the entries starts from the left margin, please advise...

I'm trying to condense the space around examples in gb4e, with the goal of removing unnecessary whitespace around examples in an abstract. Here's what gb4e gives me now:    What I'd like is for the examples to essentially look like part of the running text, as follows:    In sum, I'd like to remove the left indent before the top level item numbers, remove the vertical space between examples, and remove the vertical space above and below the exe environment.  I think \vspace commands might work here, but it would get very tedious to do this every time, and I'd also like to do it the 'right' way.  (I also think linguex might be able to do this without too much fuss, but I'm used to using gb4e so I'd prefer to stick with it if there's a way to do this.)  MWE:  \documentclass{article}  \usepackage{gb4e} \usepackage{lipsum}  \begin{document}     \lipsum[1]     \begin{exe}         \ex Blah \begin{xlist}             \ex Blah             \ex Blah         \end{xlist}         \ex Blah         \ex Blah     \end{exe}     \lipsum[1] \end{document}


TL;DR: Ubuntu boot hangs on starting the snappy daemon, takes roughly 5min to boot, reinstall doesn't fix, issue is caused by an update.    Backstory: I installed the vanilla-gnome-session and after deciding I didn't like it removed it again. I later had installed and removed ubuntu-gnome-session hoping that it would bring back the old login screen. After that I did an update before reboot. Upon shutdown the loading screen for ubuntu gnome appeared and was running a kernel upgrade. Then when booting again the loading boot screen for ubuntu froze, switching to TTY2 revealed that it hung on three jobs:  A start job is running for * Snappy daemon * Wait until snapd is fully seeded * Hold until boot process finishes up   It takes roughly 5min until this process is finished.  After some unsuccesful troubleshooting decided to reinstall. I first used the reinstall option from the live install disc and after finishing the PC booted fine even after a reboot. However as soon as I ran apt update && apt upgrade it would hang again.  Some goes after doing a complete reinstall (choosing "erase disk and install" on the install disc)

I'be been running 18.04 since a clean SSD install on the day of it's official release, without issues. Power on to login was seconds (max 10)  Then, I did a regular upgrade this morning:  $ sudo apt update && sudo apt dist-upgrade   The packages installed/upgraded were:  Install: linux-headers-4.15.0-24:amd64 (4.15.0-24.26, automatic), linux-headers-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-modules-extra-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-modules-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic), linux-image-4.15.0-24-generic:amd64 (4.15.0-24.26, automatic) Upgrade: gnome-control-center-data:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-headers-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), gnome-control-center:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-image-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), linux-signed-generic:amd64 (4.15.0.23.25, 4.15.0.24.26), gnome-control-center-faces:amd64 (1:3.28.1-0ubuntu1.18.04.1, 1:3.28.1-0ubuntu1.18.04.2), linux-generic:amd64 (4.15.0.23.25, 4.15.0.24.26)   I rebooted once the upgrade had completed, and noted a 2-3 minute delay on the Ubuntu loading/splash screen (prior to login) (without any progress/activity indicated on the dots).  I powered off and tried to boot again, but am getting this delay consistently now. Also close down is much slower too.  Update #1 (2018-07-03): Analysis on systemd:  $ sudo systemd-analyze blame 3min 53.073s plymouth-quit-wait.service     2min 20.699s snapd.seeded.service          49.949s snapd.service           6.186s NetworkManager-wait-online.service           1.148s dev-sda2.device           1.098s plymouth-start.service   Showing that plymouth-quit-wait.service (which I now believe is related to the Ubuntu loading/splash screen) and snapd.seeded.service were by far the longest running services to initiate. So I compared the times before the dist-upgrade and after:  $ journalctl -u plymouth-quit-wait.service --since today -- Logs begin at Fri 2018-04-27 13:01:30 BST, end at Tue 2018-07-03 12:38:05 BST. -- Jul 03 04:15:43 user-laptop systemd[1]: Starting Hold until boot process finishes up... Jul 03 04:15:46 user-laptop systemd[1]: Started Hold until boot process finishes up. -- Reboot -- Jul 03 04:21:17 user-laptop systemd[1]: Starting Hold until boot process finishes up... Jul 03 04:24:52 user-laptop systemd[1]: Started Hold until boot process finishes up.   Before the upgrade plymouth-quit-wait.service took 3 seconds. After the upgrade it took 3 minutes 35 seconds  $ journalctl -u snapd.seeded.service --since today -- Logs begin at Fri 2018-04-27 13:01:30 BST, end at Tue 2018-07-03 12:42:14 BST. -- Jul 03 04:15:43 user-laptop systemd[1]: Starting Wait until snapd is fully seeded... Jul 03 04:15:43 user-laptop systemd[1]: Started Wait until snapd is fully seeded. -- Reboot -- Jul 03 04:22:47 user-laptop systemd[1]: Starting Wait until snapd is fully seeded... Jul 03 04:24:49 user-laptop systemd[1]: Started Wait until snapd is fully seeded.   Before the upgrade snapd.seeded.service took 0 seconds. After the upgrade it took 2 minutes 2 seconds.  Update #2 (2018-07-06): This morning's boot saw the return of the delay. So I guess we're still waiting for the kernel/plymouth/snapd update.  Update #3 (2018-07-12): The problem seems to be resolved, but I didn't see any update to snap or plymouth, and I'm still running 4.15.0-24 kernel. So I'm not sure which package update fixed the problem, or if it just resolved itself somehow. Reading the bug updates on launchpad it's unclear to me what was done (or is being done) to what package/s. If anyone can clarify that would be very useful.


I need to find a topology over $\mathbb{R}$ that is (strictly) coarser than its usual topology, and must be Hausdorff and connected. However, every topology that I had considered fails in one of those conditions. For instance, neither the cofinite topology and the topology generated by semi-rays are Hausdorff but both are connected topologies.  I don't know if such topology exists, can someone help me?

The following are simple observations.  Suppose $\mathcal{T}_1,\mathcal{T}_2$ are two topologies on a set $X$ such that $\mathcal{T}_1$ is finer than $\mathcal{T}_2$.  If $( X ,\mathcal{T}_2 )$ is Hausdorff, then so is $( X ,\mathcal{T}_1 )$. If $( X ,\mathcal{T}_1 )$ is connected,  then so is $( X ,\mathcal{T}_2 )$.   The real numbers with the usual topology is both Hausdorff and connected, which leads to the following two questions.  Is there a topology on the real numbers strictly coarser than the usual one, which makes it still Hausdorff?  Is there a topology on the real numbers strictly finer than the usual one, which makes it still a connected space?


I run a site where multiple photographers upload and sell their photos to my users.  Some of them just want to buy a JPEG, some of them want to buy a JPEG to print.  You and I both know that a 6000x4000 72dpi file is essentially "identical" to a 6000x4000 300dpi file, but  a) users don't always b) more importantly, some online printers don't seem to.  I've come across more than one printer who requires photos to be 300dpi, even though simply changing a file's dpi metadata makes no difference to the image data.  If I were to set the dpi EXIF of all photos bought on the site would I end these headaches for people?  Would it cause any problems anywhere else?  Do some computers/phones/softwares treat 300dpi images on a screen differently to the "standard" 72dpi image on a screen?  I don't believe there SHOULD be any problem with doing this... but I wanted to tap into the collective knowledge here to double check.  Thanks

I often see statements in discussions about web displayed image quality that go something like this: "I only upload pictures at 72 dpi and 1200 pixels on the long edge, so if someone copies and prints the image it won't look as good as if it were 300 dpi."  What? Have I missed something here?  Does an image edited and saved/exported with 1200x800 pixels at 300 ppi look any different online than the same image saved/exported with 1200x800 pixels at 72 ppi? Other than the metadata regarding ppi, is there any difference in the two images at all? If so, what is the difference? If I tell my printer to print the images at 4R (4X6 inches) will there be any difference at all in how the printer creates a print from the 1200x800 @ 300 dpi image versus the 1200x800 @ 72 dpi image?


When is it worth it to create one of the above and when is it better to keep things in the same place?

This is a  about Active Directory Domain Services (AD DS).         I find myself explaining some of what I assume is common knowledge about it almost daily. This question will, hopefully, serve as a canonical question and answer for most basic Active Directory questions. If you feel that you can improve the answer to this question, please edit away.


Currently,  which prevents deleting cookies - causing an exception: OpenQA.Selenium.WebDriverException: 'Unknown error’  Microsoft’s response was to mark it as Won’t Fix and advise updating the version of Edge.  Unfortunately, telling clients to update their browser version isn’t ideal. Is there a workaround which will allow me to remove a cookie, without this exception?

How do you delete all the cookies for the current domain using JavaScript?


When I get an email about an inbox notification on any Stack Exchange site it comes from "Stack Overflow <do-not-reply@stackoverflow.email>"   And I think they should at least change the name displayed on the front of the email if not the email address itself to stackexchange.email.   Also, I think they should remove the link at the top of all SE notifications which links to Stack Overflow and change it to link to Stack Exchange instead.

I got a mail from the Stack Exchange Travel Site that I am one of the top users this month.  In the email, I saw:     Email us directly at team@stackoverflow.com any time   Why are they putting @stackoverflow.com there instead of @stackexchange.com?


I am confused with changes in 18 04 with windows switching in presence of multiple workspaces. Imagine that I have an application (say terminal) open in two different workspaces. Now using alt+tab and choosing the application seems to have different behaviours:   ubuntu 16.04: go to application within the same workspace ubuntu 18.04: go to application but in the workspace where it was last used.    Is this correct? If yes, is there any chance I can revert to the 16.04 like behaviour?   Thanks!!  PS: technically, this is a duplicate of this  on Ubuntu 11.04, it seems old enough that a new answer is welcome?

I am looking for a clean and fast method to force GNOME in Ubuntu 14.04 to switch between active apps only on the current workspace when pressing the shortcut alt + tab.


In a series circuit, the voltage is the same everywhere on that circuit. However, thinking about Voltage as a steady force or potential, I imagine that at parts of the circuit without resistance, the current would be greater as the force would be able to move them faster, without any obstruction. Why is this not the case?

I understand when we say current, we mean charge (protons/electrons) passing past a point per second. And the charges have energy due to the e.m.f. of the power supply.  Now tell me, if a lamp has resistance and you hook it in the circuit, how will the current stay the same? The charges obviously lose energy in the lamp and so become SLOWER, which should mean current decreases, right?  [Edit] All answers explained a bit of everything, so it was hard to choose one. If YOU are looking for an answer, please check the others too, in case the accepted one doesn't answer your question.


When I search bookmarks I can't find a way to locate the folder of the result.  I have many bookmarks folder and subfolders and most folders and subfolders contain some bookmarks. When I cannot remember or guess the folder where a bookmark resides but I know I have it, I can search for bookmarks and all results are listed and I can click each result. There are properties of each result displayed. I would expect that the folder where a bookmark lives is an important property, but I cannot find this information.  Is this a one way street? Once you put it somewhere you have to always remember where you put it, otherwise no way to locate it? Is such a basic back reference missing in the Firefox bookmarks search?  Edit: In the meantime I found a related question (my question is also asked as a secondary question there), just for reference:   Edit 2: This was already filed as a bug:  as pointed out by m_cowen_uk in his answer.

The search box in the bookmarks bar only searches the bookmarks themselves, yet I have arranged the bookmarks into folders and subfolders. Sometimes I can't see the folder that I know I have, so I would like to do a search for it. Even if I find a bookmark that I have, onces it comes up as a result of a bookmark search, there's no way of finding out what folder it is contained within so I can get the other bookmarks - I'd like a similar function to Open Containing Folder.  I've had a look for an add-on to do this but the problem is the terms bookmark, folder and organise are too general.


I've been seeing a lot of really old questions being bumped to the front page because a person who most likely found the question on google answers "Yeah me too".   These are two examples:       I'm sure there are more. In these questions, the answers have been deleted by an admin/votes, but they were there at one point.  That's why I say that all questions that have gone 60 days straight with no activity should become protected.

I came across a question on serverfault today that is about 18 months old.  The reason I found it is that a 1 rep user had just added an answer.  I didn't notice the date at first, and added my own answer as well.  This isn't a huge deal for one question, but what about the general case?  Does it make sense that any question over, say, a year (or even just six months) should be automatically protected? I know technology changes and we want the ability to keep older questions up to date, but remember that protecting a question only locks it for users with a small rep. What about including views as part of the equation?  A question that earns a "Popular Question" badge is probably getting enough views from low rep users to really need protection and enough views from higher rep users to get the edit and new answer attention when needed, but lower view questions maybe either don't need the protection or do need the edit/answer help from anyone who does happen to land at the question. Update: For context, here is a link to a query that shows actual answers that would have been blocked under this proposal, so we can judge the typical quality.  Note that to accurately judge this you have to view them in the context of answers that are already available to the question at the time the answer is added:  And here is a query to show how many questions would be effected:  Notethat this is a naive query: it only checks answer count rather than whether the answer has an upvote, and there's no way right now to know how many of these are already protected.  Using the current data set, the result is 114039, or a little less than 1/10th of all questions, and because of the other limitations it's probably even smaller.


Usually I would write the given sum in the form $$lim_{n \to \infty}\frac{1}{n}\sum_{r=o}^{n}{f(\frac{r}{n})}$$ and then approximate it with the integral $$\int_{0}^{1}f(x)dx$$ but it doesn't seem so easy to do with this question. The solution says that this sum is equal to the integral: $$\int_{0}^{1}x^2e^xdx$$ without any further explanation. I can't see how they are equal. Any help is appreciated.

Evaluate $\displaystyle \lim_{n\rightarrow \infty}\sum^{n}_{k=0}\frac{\binom{n}{k}}{n^k(k+3)}$.   $\bf{My\; Try::}$ Although we can solve it by converting into definite Integration.  But I want to solve it without Using Integration.  So $\displaystyle \lim_{n\rightarrow \infty}\sum^{n}_{k=0}\frac{\binom{n}{k}}{n^k(k+3)} = \lim_{n\rightarrow \infty}\sum^{n}_{k=0}\frac{(n-1)(n-2).......(n-k+1)}{k!\cdot n^{k}\cdot (k+3)}$  Now How can i solve after that, Help required, Thanks


Not long ago I did the 'A night to remember' quest. You will be teleported into another dimension then  when completed, you will be teleported back to the bar you found Sam.. But when I was there Jordis sword maiden was there with me to be my follower but when I was teleported she was not with me.. I tried to teleport her to me using commands and even going back to the same place but to no avail.. What do I do?

At the end of the "A Night to Remember" quest line, my follower came with me when I was teleported to the Misty Grove. Once there, I told my follower to wait.  Now, when I was teleported back to the real world, my follower's not with me: presumably because he's still waiting at the Misty Grove. I've waited for some time and still he hasn't come back.  How can I get my follower back?


Hi i am having a problem making a custom tag for this equation  \begin{equation*}\label{eq:3}         C_1 = \theta \left(Y_1^L -T_1+\frac{1}{1+r}(Y_2^L+T_2)+V_1\right) \tag(3)     \end{equation*}   I want to refer to an equation from a book (as part of my class) which i called equation 3. But i simply can't change it without getting a lot of syntax errors.  I have tryed different things form the forum, but so far without luck.  Hope you can help.

I would like to label an equation with an arbitrary symbol, rather than a number, or letter.  Is this possible?


I have around hundreds of jars at a particular directory which my application uses. So I thought its hard to add each jars one by one to the classpath. So is there any command or any way so that i can add all the jars at one go. some *.jar should add all the jars.

Is there a way to include all the jar files within a directory in the classpath?  I'm trying java -classpath lib/*.jar:. my.package.Program and it is not able to find class files that are certainly in those jars.  Do I need to add each jar file to the classpath separately?


Does JavaScript's base form validation have limitations since we know that there is an option for a user to shut off Javascript option from the browser?  Is client side base form validation is an efficient way to validate forms in a web application?

Which is better to do client side or server side validation?  In our situation we are using    jQuery and MVC.   JSON data to pass between our View and Controller.     A lot of the validation I do is validating data as users enter it. For example I use the the keypress event to prevent letters in a text box, set a max number of characters and that a number is with in a range.   I guess the better question would be, Are there any benefits to doing server side validation over client side?    Awesome answers everyone. The website that we have is password protected and for a small user base(<50). If they are not running JavaScript we will send ninjas. But if we were designing a site for everyone one I'd agree to do validation on both sides.


I am using my early 2015 MacBook Pro as a desktop by connecting it to an external display, thus, it needs to be plugged in to a charger all the time.  Does charging my early 2015 MacBook Pro all the time damage the battery? Is it a bad practice?

My friend told me that I need to disconnect the power cord when the battery is fully charged. Otherwise, I will shorten the life of the battery.  Other people say you should drain it once a month or point out that for long term storage, you should charge it to 50% and then periodically (3 to 6 months) bring it back to 50% and store it again.  I am going to use my laptop at home 90% of the time. So, I plan to have the power cord connected all the time.  I'd prefer to just plugging in my MacBook Pro and letting it be on charge long term and occasionally taking it away from the charger when I'm not at home or my desk.  Are these specific recommendations worth the inconvenience?


I've only just identified something which has been bugging me for literally years. Why does the executioner Fudge brings to kill Buckbeak use an axe? Seriously, one Avada Kedavra and it's done with zero pain, zero mess and zero effort. Possible arguments and why I think they're wrong.  Not every wizard knows how to use the killing curse. - Sure, that's true but we know the Ministry of Magic employs aurors, and employs someone purely to execute dangerous animals. So that wouldn't be a problem. It's an unforgivable curse, it's illegal. - The fake Professor Moody makes it clear that the unforgivable curses are only illegal when used against a fellow human being, then uses them on spiders by way of demonstration.  Here are some possible real-world, fiction writing, reasons (I'm not looking for these):  The image of an executioner with an axe is a frightening and dramatic image. The sound of the axe coming down gives the kids a reason to falsely think Buckbeak has already been killed. This might make it easier for Harry and Hermione to escape with Buckbeak.  So, are there any in-world reasons the ministry would choose to use an axe instead of a spell?

In Harry Potter and the Prisoner of Azkaban      Buckbeak (or Witherwings)    is sentenced to death by the Ministry of Magic. Walden Macnair, the Executioner of the Ministry of Magic, is brought to Hogwarts to carry out the sentence.  In the end      the execution didn't actually take place.   There is one thing I can't understand: why kill him with an ax? Why would there be an executioner at all? Wouldn't it be simpler, cleaner, and less torturous for the convict to use a poison, or any other magical way to humanely and legally kill? Even if there isn't a thing like that (which I doubt) it still seems way too brutal to use an ax, especially when you're the Ministry of Magic.


I am an English as a Second Language teacher in Indonesia. Currently, in my class I have a girl who is in third grade who I think (I don’t know because there is no sort of diagnosis here) SM. I want to help this girl as much as I can but there are a few things which make it more difficult that perhaps someone here might be able to give me hints on how best to move forward.  First of all, I only meet her for 35 minutes a day teaching her and her class English. I have no opportunity to have any time on my own with her and I am under pressure to teach the whole class English as a second language so just not much time at all. Second, I have no chance what so ever to speak to her parents. Her form teacher just says she is shy and there is no need to speak to her parents or spend any extra time with her. Third, I can only speak to her in English so I don’t know how much she is understanding when I am reassuring her that she is in a safe situation.  The positives though are that when I give her instructions she seems to follow them so I think she is understanding a lot of what I say. Second, she seems to like me, she likes sitting close to me when we are all reading together and often tugs on my arm if she wants me to look at her work. Third, she has just started nodding and shaking her head (only about 25% of the time but I think that is great progress).  What I usually do (Please tell me if you think I am doing anything wrong!) I talk to her just in the same way as I chat to the other students, giving a pause if she wants to give me an answer but when she doesn’t just continue chatting, giving her praise for good work or commenting on her cute bracelet or whatever. Second, I try and tell her and her friends that she is welcome to speak at any time she feels comfortable but it is also no problem that she keeps her thoughts to herself. I try and involve her in anything I can as sometimes the other students leave her out but I have a very demanding class so I have to confess that sometimes she gets left out a bit since I am teaching communicative English and the majority of my lessons involve talking.  One more thing I want to ask, since she seems a little closer to me she has started wondering around more and not focusing on her work. Before, if it was something written she would sit on her seat and give it a try but since she has started nodding and tugging on my arm she seems to wonder more and not sit down as much. What can I do? I try to say to her calmly that she has to sit down and focus like her friends but I just don’t know what is the best thing to say to her.  I read on a blog that I could give her some cards for asking to go to the bathroom etc so I plan on doing that but I would love any other ideas from anyone who has them! Thank you for reading!

Although I am not a parent, I am interning in social work.  I am currently working with a student in an elementary school who does not speak. The parents have explained that she does speak at home (I also witnessed her speaking to her mother outside of the school), but she has not said a word since she began school in August.  I work with her individually and in a group, and she still refrains from speaking in both settings.  We wonder if the cause is anxiety because she's not speaking at school but she is at home.  Have any of you experienced something similar with your children? What can we do as school staff to create an environment that is more comfortable/less anxiety-inducing for her?


I know only about  published by Indian Academy of Sciences and I've read most of the content from it's math portion of all the issues.

I want to make someone a present by subscribing for him to a mathematical journal. (It should appear every month or every two months). The contents should be comprehensible to an undergraduate in mathematics, and be about a broad selection of topics (for example not only analysis).   I expect the content to be something like proposing interesting problems and then giving solutions with some references for further study. Are there some famous journals you could suggest me?


A group of prime order is cyclic and so unique.   But is this the only possibility?  How do you characterize finite group of order $n$ for which it is unique up to isomorphism?  As pointed out by friend earlier, if $n=pq$ is composite, then $C(p) \times C(q)$ is not isomorphic to $C(n)$ and we are done.   But Here is a theorem:     Let $n$ be a positive integer. Then the cyclic group $C(n)$ of order $n$ is   the only group of order $n$ if and only if one has $(n, \phi(n)) = 1,$ where   $\phi$ denotes the Euler phi function.   I'm just trying to understand it.

According to Wikipedia, a  (in group theory) is one which is coprime to its Euler phi function and is the necessary and sufficient condition for any group of that order to be cyclic. Why is that true?  I can see that if $n$ is prime, that guarantees any group of order $n$ is cyclic, but I don't seem to see how to extend it to $(n,\phi(n))=1$  It would be nice if someone could explain it to me. Thanks.


I was following a tutorial on making a simple game with Java, but for some reason my code stopped working for no reason that I can find. This is Window class that I was using.      package com.tutorial.main;      import java.awt.Canvas;     import java.awt.Dimension;      import javax.swing.JFrame;      public class Window extends Canvas{          private static final long serialVersionUID = -240840600533728354L;          public Window(int width, int height, String title, Game game){             JFrame frame = new JFrame(title); // line 13              frame.setPreferredSize(new Dimension(width,height));             frame.setMaximumSize(new Dimension(width,height));             frame.setMinimumSize(new Dimension(width,height));              frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);             frame.setResizable(false);             frame.setLocationRelativeTo(null);             frame.add(game);             frame.setVisible(true);             game.start();          }     }   Yesterday it worked fine. Today, when I reopened Eclipse, added some more code and tried running it I get a NullPointer Exception.      Exception in thread "main" java.lang.NullPointerException         at java.awt.Window.init(Window.java:497)         at java.awt.Window.<init>(Window.java:537)         at java.awt.Frame.<init>(Frame.java:420)         at javax.swing.JFrame.<init>(JFrame.java:233)         at com.tutorial.main.Window.<init>(Window.java:13)         at com.tutorial.main.Game.<init>(Game.java:26)         at com.tutorial.main.Game.main(Game.java:105)   I did not change anything in the Window class, nor the game class so I have no idea what is causing this. This is the line in Game.java that calls the window:      new Window(WIDTH, HEIGHT, "Game", this); // line 26

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?


How can I show that the elements A * B and B * A have the same order?    where A, B belong to a finite group G   How can I prove that 2 elements have the same order? I was thinking of showing that if (A * B)^n=id; and (B * A)^m=id then n=m; Any ideas or tips how I can do that? Thank you!

How do I prove that if $a$, $b$ are elements of group, then $o(ab) = o(ba)$?   For some reason I end up doing the proof for abelian(ness?), i.e., I assume that the order of $ab$ is $2$ and do the steps that lead me to conclude that $ab=ba$, so the orders must be the same. Is that the right way to do it?


This is from Lang's Algebra (page 251)     Proposition 6.11 Let $E/F$ be a normal field extension. Let $E^G$ be the fixed field of $\operatorname{Aut}(E/F)$. Then, $E^G$ is purely inseparable over $F$ and $E$ is separable over $E^G$.   And below is a corollary of this theorem:     Corollary 6.12. Let $F$ be a field with characteristic $p\neq 0$ such that $F^p=F$. Then, every algebraic extension $E$ of $F$ is separable and $E^p=E$.   How this is a corollary of the above theorem?  Lang states that "Every algebraic extension is contained in a normal extension, so Proposition 6.11 can be applied to get this", but how?  Let $E$ be an algebraic extension of $F$. Then, there is a field extension $L$ of $E$ such that $L/F$ is normal.  Let $\phi\colon F\to F:a\mapsto a^p$.  Then, by hypothesis, $\phi$ is a field automorphism of $F$.  Then, $\phi$ can be extended to a field monomorphism $\sigma \colon \bar F \to \bar F$, but since $\phi$ is not fixing $F$, I don't get what this has to do with Proposition 6.11.  These are what all I know. How do I proceed to prove the corollary?

I am trying to prove this statement in the characteristic $p>0$ case.     Every algebraic extension of a perfect field is separable and perfect.   This is stated as a corollary of Proposition V.6.11 in Lang.     Let $k$ be a field and let $K$ be a normal extension of $k$. Let $G$ be the group of automorphisms of $K$ that fix $k$. Let $K^G$ be the fixed field of $G$ acting on $K$, and $K_0$ the maximal separable subextension of $K$. Then $K^G$ is purely inseparable over $k$, $K$ is separable over $K^G$, $K_0\cap K^G =k$  and $K_0K^G=K$.   Lang doesn't write many details in the proof except that every finite extension is contained in a normal extension.   This is what I have so far. Suppose, $k=k^p$. Let $E$ be an algebraic extension of $k$. Let $\alpha \in E$. Now, $\alpha$ is contained in the field, say $K$ generated by the roots of the minimal polynomial of $\alpha$ over $k$ (and is hence normal as it's the splitting field of the minimal polynomial of $\alpha$). At this point, I don't know how to proceed. I am tempted to use the Frobenius map, but it does not fix every element of $k$ although it does stabilize it in this perfect case. Any hints will be appreciated. Thanks.


If only dimensionless constants are physically meaningful, and both Planck's constant, $h$, and the speed of light, $c$, are in the denominator of the expression for the fine structure constant, $\alpha$, then is there any way of distinguishing, by measurements or experiments, between an increase of $h$ and an increase of $c$ (assuming a definition of $c$ in terms of a meter rod, rather than itself)?

Every so often, one sees on this site* or in the news† or in journal articles‡ a statement of the form "we have measured a change in such-and-such fundamental constant" (or, perhaps more commonly, "we have constrained the rate of change of..."). These are often shrouded in controversy, with people often stating quite loudly that statements of the sort are meaningless and even unverifiable, but the end result is often quite confusing. Thus:   Is it possible to speak about changes  to a physical constant that contains dimensional information? If not, why not?     *          .$\ \ $† .$\ \ $‡ .


Does the ArcGIS Pro feature "least cost corridor" have an equivalent module or workflow in QGIS?

I'm trying to work out least cost paths in QGIS. I have a DEM and a slope raster extracted from it, and a set of points, between which I want to find the least cost paths. I can find a SAGA plugin, but it needs a cost raster.   How do I go about making one of those, and then getting the least cost paths?


So I understand that if it said the number of underordered then it would have been  $\binom{k+t-1}{t-1}$ or $\binom{k+t-1}{k}$ but the ordered part is throwing me off so I don't know what to write as this formula.

Is there a formula or method to find the number of 6-letter words from the English alphabet if repetition is allowed, but they must appear in alphabetical order?   Type what you know about how many words there'd be if they didn't also need to be in alphabetical order...  Limitless repetition however ordering wasn't specified. I'm so confused as to how to combine the formula for repetition and ordering.  I know the number six letter words that do not have to appear in alphabetical order would be $26^6$.  But when I try to count only those words that are alphabetically ordered, I get stuck.


Is it possible to animate a background color change in a click function? I saw many examples with mouseover/hover functions but none with a click function. Only without animation following line works:  $('#element').css({ backgroundColor: "#99cc00" });   I tried to add an animation effect with:  $('#element').animate({ backgroundColor: '#ffffff' }, 2000);    and   $('#element').css({ backgroundColor: "#99cc00" }).animate({}, 2500);   but without an effect. Please have a look at my fiddle:   Any ideas?

I am trying to animate a change in backgroundColor using jQuery on mouseover.  I have checked some example and I seem to have it right, it works with other properties like fontSize, but with backgroundColor I get and "Invalid Property" js error. The element I am working with is a div.  $(".usercontent").mouseover(function() {     $(this).animate({ backgroundColor: "olive" }, "slow"); });   Any ideas?


I do not know how to solve the following:     Show that If $(b,c) = 1$, then $(a,bc) = (a,b)(a,c)$   Thanks.

Problem: Show that if $(b,c)=1$, then for any integer $a$ we have $(a,bc)=(a,b)(a,c)$. [Hint: Prove that each member of the alleged equation divides the other.]  This is the way I proved it (without the hint): $(a,b)(a,c)=(a(a,b),c(a,b))=(a^2,ab,ac,bc)=(a^2,bc,a(b,c))=(a^2,a,bc)=((a^2,a),bc)=(a,bc)$  But how should I prove it using that hint or at least a similar proof.


I toss a balanced coin until the number of heads I get equals the number of tails? What's the chance I never stop?  I have tried considering the reverse event and a recursive reasoning but nothing conclusive. A close question has already been asked here but I don't know the Markov formalism that is used.

How does one prove that a simple (steps of length $1$ in directions parallel to the axes) symmetric (each possible direction is equally likely) random walk in $1$ or $2$ dimensions returns to the origin with probability $1$?  Edit: note that while returning to the origin is guaranteed $(p = 1)$ in $1$ and $2$ dimensions, it is not guaranteed in higher dimensions; this means that something in a correct justification for the $1$- or $2$-d case must fail to extend to $3$-d (or fail when the probability for each direction drops from $\frac14$ to $\frac16$).


I'm working with payroll data in a spreadsheet. What I'm looking to find is a total across different rows of employees with different roles. For example, how could I write a forumla for the "Total Hours" column below? ╔═══════╦══════════╦═══════════╦═══════╦═════════════╗ ║ Emp # ║ Employee ║   Role    ║ Hours ║ Total Hours ║ ╠═══════╬══════════╬═══════════╬═══════╬═════════════╣ ║     1 ║ Jim      ║ Role 1    ║     5 ║           7 ║ ║     1 ║ Jim      ║ Role 2    ║     2 ║             ║ ║     2 ║ Bob      ║ Only Role ║    10 ║          10 ║ ║     3 ║ Jane     ║ Role 1    ║    10 ║          15 ║ ║     3 ║ Jane     ║ Role 2    ║     2 ║             ║ ║     3 ║ Jane     ║ Role 3    ║     3 ║             ║ ╚═══════╩══════════╩═══════════╩═══════╩═════════════╝

I'm trying to figure out how to "group by" values in an Excel spreadsheet.  Given the following example (this is an inventory sheet I use at my restaurant:)    At the far right of the spreadsheet there is a column named Cost of Goods Sold.  I would like to be able to come up with a total COGS figure for each Category.  Is this possible in excel? Moreover, I'd like to do it in a separate worksheet so that the first worksheet (what is pictured) isn't affected.  Any ideas?  Thanks!


Hi I have problem with response from REST. I receive Object Json parse it and everything look fine but when i try add it to Realm i get Null Pointer Exception. This is link to my project:   In MainActivity I call function synchronizeContractorsItems then in the 3-th Call i'm get the error.

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?


Last year I purchased a car with a cosigner. I've made all payments on said car. Now that his sister inlaw and I are broken up he has taken the car. He's made no payments and has hidden the car from me. Is that legal?

As a co-buyer on an automobile, can the other party take full possession? Both parties names are listed as the Purchaser's. Only one purchaser signed the retail order for the motor vehicle, and if so, how can one become a no co-buyer?


I have a scenario where in before update context I want to check a list of fields for changes. Normally I would simply compare the values between newMap and oldMap as such:  for(Record r : Trigger.new) {     if(Trigger.oldMap.get(r.Id).thisField__c != Trigger.newMap.get(r.Id).thisField__c) //The field value has been edited in this update     {perform business logic} }   It seems to me like this could be a great place to use FieldSets, so that I can easily add or remove fields that I want to check for edits in this loop, but all I can find is FieldSetMember.getFieldPath() which returns a string - that is great for use in a SOQL query, but what about here where I want to directly reference those fields in my apex code?  Is there any way to do this? I had imagined it looking something like this, but I've put ??? where I am at a loss for how to reference the field in question on the record within newMap or oldMap.  List<FieldSetMember> fieldsToCheck = Schema.SObjectType.Object.fieldSets.Fields_To_Check.getFields();  for(Record r : Trigger.new) {     for(FieldSetMember fsm : fieldsToCheck)     {         if(Trigger.oldMap.get(r.Id).??? != Trigger.newMap.get(r.Id).???) //The field value has been edited in this update         {perform business logic}     } }

I have 30+ fields in a field set, and in the update part of my trigger, I want to see if any of those fields have been changed. Can I access them using field sets?  Anyway to do it, short of writing out every field in my trigger?  I'm doing something similar to this:


So I got an abuse complaint for one of my dedicated servers, running Debian 6.0  Sure enough, sometimes, top shows /usr/bin/host using a lot of CPU for no apparent reason, and netstat shows process host doing a lot of HTTP requests.  After while, my syslog even says nf_conntrack: table full, dropping packet., which i assume has something to do with this matter.  I have verified the executable /usr/bin/host using debsums, and is seems to be fine, too. The server as such is 100% updated, too.  So i am guessing something is somehow calling my host executable and coercing it to do HTTP requests for some DDoS.  I could of course simply hack together a script to killall host as soon as this is happening, but I would really like to know where the problem originates from.  I am checking the Apache logs for interesting entries around the time that host is starting to do its requestst, but haven’t found anything yet.  Anyone have a recommendation on what else to do? How can I see who and what called 'host'? Google didnt show up any examples of /usr/bin/host being abused, at all!

This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.