I updated to Ubuntu 20.04.1. Now nothing opens. When I try to get to BIOS, nothing. This is what it goes to and stops at: /dev/sda2 : clean, 214252/60497920 files 5981192/241989376 blocks.  That’s what it says on the screen it goes to. Left it there for a day to see if it would move. But nothing. Can’t get to any screen other than that. I’m on a Visio all in one. Is my machine history now?

dev/sda1: clean, 552599/6111232 files, 7119295/24414464 blocks   After I turn on my laptop this message appears. The system never boots, the message just stays there.


The force of gravity keeps our Moon in orbit around Earth. Is it correct to say that the Moon is in “free fall” around Earth? Why or why not?   I think the answer is yes. The moon is falling towards the Earth due to gravity; but, it's also orbiting the Earth as fast as it's falling towards it. This balance between the 2 forces means the moon is essentially "freefalling" towards the Earth. Is my thinking correct? Thanks.

Why doesn't the Moon fall onto the Earth? For that matter, why doesn't anything rotating a larger body ever fall onto the larger body?


Is there a way of redefining the em-dash ligature --- so as to mean \,---\,? Something like:  \let\oldemdash--- \def---{\,\oldemdash\,}   which of course doesn't work.

Is there a method just write --- to get an em-dash, putting a thinspace both before and after it? The situation about break is similar with the original ---.


I was just wondering about squibs in Harry Potter.  I can't remember if they can give birth to normal wizards, does anyone know?

As the title asks, is it genetically possible for a Squib to produce magical offspring, or would the Squib gene trump the magic gene in all cases? How would it be possible for a Squib to have magical children? Additionally, must a Squib come from a pureblooded union, or does the possibility of a half-blood Squib exist?


I have a problem with retrieving data from firebase realtime database. It keeps giving me an error saying "java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference" So this method is used to retrieve data from firebase database and log users in with their username and password. I have tried if(Accounts.getPassword() != null && password.getText() != null && Accounts.getPassword().equals(password.getText().toString())) but no luck it still gives me the error. private void isUser() {     final String userEnteredUsername = username.getText().toString().trim();     final String userEnteredPassword = password.getText().toString().trim();      DatabaseReference reff = FirebaseDatabase.getInstance().getReference("login");      Query checkUser = reff.orderByChild("username").equalTo(userEnteredUsername);      checkUser.addListenerForSingleValueEvent(new ValueEventListener() {         @Override         public void onDataChange(@NonNull DataSnapshot dataSnapshot) {                if (dataSnapshot.exists()){                  String passwordFromDB = dataSnapshot.child(userEnteredUsername).child("password").getValue(String.class);                 Accounts accounts = dataSnapshot.getValue(Accounts.class);                   if (passwordFromDB.equals(userEnteredPassword){ // ****Line that code is not working****                      String usernameFromDB = dataSnapshot.child(userEnteredUsername).child("username").getValue(String.class);                     String accountFromDB = dataSnapshot.child(userEnteredUsername).child("account").getValue(String.class);                       Intent intent = new Intent(getApplicationContext(), Driver.class);                      intent.putExtra("username", usernameFromDB);                     intent.putExtra("password", passwordFromDB);                     intent.putExtra("account", accountFromDB);                      startActivity(intent);                 }                 else {                     password.setError("Wrong Password");                     password.requestFocus();                 }             }             else {                 username.setError("Wrong username");                 username.requestFocus();             }         }         @Override         public void onCancelled(@NonNull DatabaseError 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?


I tried to generate the  sum (using md5sum) of a string, "hello". I tried out different methods as the md5sum tool in Linux, PHP's MD5() function as well as various online text to md5sum translators.  echo "hello" | md5sum   and  echo "hello" > file && md5sum file   Gave the result b1946ac92492d2347c6235b4d2611184. However, PHP's md5() function and almost all online generators gave the output 5D41402ABC4B2A76B9719D911017C592.  What is the reason?

On a  (Leopard) PowerPC, if I do: echo "hello" | md5  on the command line, the result is:  b1946ac92492d2347c6235b4d2611184   But if I enter hello into one of the online MD5 hash sites like , I get:  5d41402abc4b2a76b9719d911017c592   Am I doing something wrong? If I want to use MD5 on the go, how can I make sure what I'm getting on the command line will agree with the online md5 tools?


I am trying to find out if I am doing this right:  I have started with: $f(y)=\binom{n}{y}(\frac{\mu}{n})^y(1-\frac{\mu}{n})^{n-y}$  This is what I get: Result: $exp[ylog(\frac{\mu}{n-\mu}) - nlog(1+e^\theta)+log\binom{n}{y}]$ $\theta=log(\frac{\mu}{n-\mu})$ $b(\theta)=nlog(1+e^\theta)$ $\phi=1$ $a(\phi)=1$ $c(\phi,y)=log(\binom{n}{y})$    However, I found this solution that looks similar but different to mine and values of a and b seem to be different:    So, I noticed they are using $\pi$ instead of $\frac{u}{n}$ so I am not sure if the solutions are equivalent or I made a mistake somewhere along the line.    So I have a couple of questions  Is it possible to have 2 different solutions with different values for a and b and maybe c? Also, in the notes I have $a(\phi)==\phi$ in the examples I have but it might not be true everywhere?

I define an exponential dispersion family as any distribution whose PMF/PDF is  $$f(y \mid \boldsymbol\theta) = \exp\left\{\phi[y\theta - b(\theta)] + c(y, \phi) \right\}\text{, } y \in \Omega$$ where $\Omega$ is in the support of a random variable $Y$ in the family.  Suppose $Y_1, \dots, Y_m$ are independent and binomially distributed ($n$ trials, success probability $p_i$). I've already shown that the Binomial distribution satisfies the above, with $$\begin{align} \phi &= 1 \\ \theta_i &= \log\left(\dfrac{p_i}{1-p_i} \right) \\ b(\theta_i) &= n\log\left(\dfrac{1}{1-p_i}\right) \\ c(\phi, y_i) &= \log\binom{n}{y_i}\text{.} \end{align}$$ After some work, I showed that, as a function of $\theta_i$,  $$b(\theta_i) = n\log(e^{\theta_i} + 1)$$ (this is consistent with what I found at ) and I understand that  $$\mu_i = b^{\prime}(\theta_i) = n \cdot \dfrac{e^{\theta_i}}{e^{\theta_i}+1}\text{.}$$  I also understand that what we need to do is solve for $\theta_i$ in the above, and the canonical link function would be $g(\mu_i) = \theta_i$ according to above. But one thing bothers me: when I run the above through , I obtain $$g(\mu_i) = \theta_i = \log\left( \dfrac{\mu_i}{n-\mu_i}\right)\text{.}$$ Every source I've seen says that the $n$ above should be a $1$ for the binomial canonical link function. Did I do something wrong?


Sometimes @username option doesn't work and enable me to tag a person in a comment who answered a post of mine. In that case, how can I tag the person so that he gets informed?

How do the comment replies (aka "pinging users") work?  Who can I send an @reply to? How do I respond to a specific user when entering my comment? Will they be notified? What do people mean when they talk about "pinging" another user?  Related:


I was following on the above mentioned topic since long & finally got to see this link "  ". But, unfortunately, following this method on chrome i got the error saying : " Uncaught ReferenceError: XMLWriter is not defined" I tried to reply on that blog itself but i think it is no longer available & hence i choose to write here.  can anyone hekp me out with this please.

Is there local file manipulation that's been done with JavaScript? I'm looking for a solution that can be accomplished with no install footprint like requiring .  Specifically, I'd like to read the contents from a file and write those contents to another file. At this point I'm not worried about gaining permissions and am just assuming I already have full permissions to these files.


I'm struggling to understand the idea that if two observers are moving relative to each other, they both see the other's clock as running more slowly. This is a well-known paradox in special relativity, and is supposed to be dealt with by the classic 'twin paradox', but I don't feel the way the twin paradox is resolved really answers this question. It relies on the asymmetry of a two-way journey, but what if we eliminated the asymmetry? Here is a simplified version of the twin paradox I thought of: a spaceship leaves Earth for a planet 10 light years away travelling at 0.9c. Assume the time taken to accelerate to and decelerate from 0.9c is negligible. When it reaches the planet, the crew beams the date recorded on their clock to Earth. (This eliminates the asymmetry, since the message is sent before the return journey. Maybe the crew don't even make a return journey.) What date will be recorded and what will the date be on Earth when the message reaches Earth?

Suppose we have two twins travelling away from each other, each twin moving at some speed $v$:    Twin $A$ observes twin $B$’s time to be dilated so his clock runs faster than twin $B$’s clock. But twin $B$ observes twin $A$’s time to be dilated so his clock runs faster than twin $A$’s clock. Each twin thinks their clock is running faster. How can this be? Isn’t this a paradox?


I have an SSD where I store all of my virtual disks on.   I also have an 8TB drive I want to use to store all of the VM data. Example: Im running pfsense with web caching. Pfsense is on a virtual disk on the ssd, but I want the web cache to be stored in a directory on my 8TB drive. Well when I go to change the directory to my 8TB drive\pfsense\ it doesnt list it as an option.   Using virtual box latest version. pfsense latest version.

Using Virtual Box, how can I install an OS to a secondary, physical disk, and boot it in both (at separate times) Virtual Box, and as a typical secondary OS install?


I want explode to return an empty array if the delimiter is not found.  Currently, I do something like this to get the explode behavior I want:              if (strpos($line, ' ') === false) {                 $entries = [];             } else {                 $entries = explode(' ', $line);             }   There must be a more concise way of getting this behavior without having to use preg_split. preg_split has its own behavior that is also undesirable, such as including the delimiter in the resultant array entries.

PHP's explode function returns an array of strings split on some provided substring. It will return empty strings when there are leading, trailing, or consecutive delimiters, like this: var_dump(explode('/', '1/2//3/')); array(5) {   [0]=>   string(1) "1"   [1]=>   string(1) "2"   [2]=>   string(0) ""   [3]=>   string(1) "3"   [4]=>   string(0) "" }  Is there some different function or option or anything that would return everything except the empty strings? var_dump(different_explode('/', '1/2//3/')); array(3) {   [0]=>   string(1) "1"   [1]=>   string(1) "2"   [2]=>   string(1) "3" }


Is there a word or phrase which describes "choice of misleading words", or the negation: "choice of non-misleading words"? The nearest phrases I can think of are linguistic deception, or controlled language, as in .  For example, :     I think it is ok for authors (please let's not call them creators, they are not gods) to ask for money for copies of their works (please let's not devalue these works by calling them content) in order to gain income (the term compensation falsely implies it is a matter of making up for some kind of damages).   Another example is "credit" in banking, which just makes "debt" sound like a good thing.  EDIT: The term may either refer to an individual's malicious use of misleading terminology, or to widely-accepted use of misleading terminology. The answers reflect this, but my question does not.

A person in the news recently stated that he was a "Vietnam era veteran". This misled EVERYBODY into thinking he was a Vietnam veteran (and newspapers widely reprinted that he was). But no, he merely served in the armed forces while the Vietnam war was going on, but never participated.   Is there a word for that specific kind of technically-true-but-grossly-misleading claim?  BTW I'm very liberal this is not meant to be about politics but strictly language usage, there's no doubt in my mind that calling yourself a "Vietnam era veteran" is meant to convey a false impression.


I came across a sentence in my advanced book:  "Mobile phones are a public nuisance and should be banned."  I am aware of the structure "The mobile phone is a ~" Where the is used to refer to all mobile phones. Is the meaning of the second sentence the same?

I often have trouble expressing myself when I want to talk about some things (plural) holistically as a single thing.  For example, "differential equations are a form of expression...".  It doesn't seem right to say that somethings (plural) are a something (singular), but I would like to say something like this if it can be done at all correctly.


One of the effects of traveling at high speeds is slowing down of clocks. I can understand gravity time dilation effect but not how would velocity affect clock speeds.   How correct it is, if I say that higher the speed, more object travels through space dimension therefore less it travels through time dimension; therefore slowing down of time?

What are the mechanics of time dilation and length contraction? Going beyond the mathematical equations involving light and the "speed limit of the universe", what is observed is merely a phenomenon and not a true explanation of why time dilates or length contracts.  It has been proven to work out, but do we know why?  Is it something that happens at a subatomic level?


I'm getting reports from users that clicking a link gives them Page Not Found.   These are anonymous users. Page caching is turned on (but not aggressive) I log in, the page works.  I log out, the page does not work. Three reports of unrelated pages in the past week (but all were different node types) Clearing All Caches fixes it. I could be wrong about this (because I didn't think to check until after I cleared caches), but I think it's returning error 406 in Recent Log Entries.   How can I begin to troubleshoot this?

My site's drupal version is 6.19. There are always logs like the following.  the recent log entries shows  type: page not found location:http://www.example.com/display.html referrer:   message: 500.shtml   severity: warning   hostname: 95.64.11.29 or others (maybe search engine robot IP)   The URL and the content is right, but when the anonymous user accesses it, it returns the "Page not found" page. Anonymous users have the permissions to access content.  The cache_page table contains the following header for :  Content-Type: text/html; charset=utf-8 HTTP/1.1 404 Not Found   Why is the page being cached as "404 Not Found", when it actually exists?  When I access  as an anonymous user, the site shows "page not found"; when I clear the cache, anonymous users can access the page. How can I correct the cached content generated by search engine bots?


So, I can't get into third person character view. I am playing the Elder Scrolls V Skyrim on Xbox360, but when I'm in an open area (just to make sure there was enough room for the camera to move around) and press the right joystick down it doesn't work.   Any helpful ideas??

I have played Oblivion and in Oblivion you can see your person on the menu screen. When I go into 3rd person all I see is their back. Is there any way I can see my whole character?


My Schengen visa has been refused twice by French embassy. The reason states is that “The information submitted regarding the justification for the purpose and conditions of the intended stay was not reliable”.” I had given all proper documentation and can think of no reason of refusal. I am married but doing a solo trip. Though my trip covers major cities like Paris, Berne, Switzerland, Netherlands and Nice, I am also travelling to a small French town called Tonquedec. I mentioned that too in my itinerary. Is that that the visa is refused because Visa office is not sure why I am travelling there? Actually I am meeting a friend there but did not mention that in my application to avoid the hassle of him needing to get a sponsorship. What should I do next? Should I reapply and remove this town from the itinerary. If yes after how much time?

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


In Ubuntu 16.04, I ran by mistake sudo rm -rf /usr/share. I know how stupid that is (I wanted to remove /usr/share/somefolder that had been installed as root and got distracted). I interrupted it after about 5 seconds. I can already see some strange things: some text is not displaying on askubuntu.SE in firefox, when I open a terminal I get /etc/zsh/zshrc:111: compinit: function definition file not found, autocompletion returns an error, etc.  My question is: what should I do now?   Edit I install debsums and followed the steps in  to . With the command sudo debsums -cs, I could see that a lot of things where broken. However, I could not fix that other than by reinstalling (see my more detailed answer).

Is there a standard procedure to 'unit test' an Ubuntu system against the deb packages?  Assume, a system has ubuntu-desktop installed according to the package manager. Can I find out, whether the file system has all the files in ubuntu-desktop and dependencies?   related question:


For a multivariate data set, I test normality on the marginals, and I get plots like  above.  That's not my actual plot.... mine is not that obvious, the middle part is actually quite straight.... but the sharp decline/rise near the ends is the same as in my plots.  So, what does this tell us. Which model, if not the multivariate normal, should I use?

I am working with a small dataset (21 observations) and have the following normal QQ plot in R:     Seeing that the plot does not support normality, what could I infer about the underlying distribution? It seems to me that a distribution more skewed to the right would be a better fit, is that right? Also, what other conclusions can we draw from the data?


Consider two infinite circular cylinders of equal radius whose axes meet in a right angle.  (a) What is the volume of their intersection?  (b) What is the area cut out of one by the other?  How to start this question?

Find the volume common to two circular cylinders, each with radius r, if the axes of the cylinders intersect at right angles. (using disk/washer)  I saw no example of this problem anywhere.. I saw an example how to solve it without calculus but I'm afraid that'll be deductions on my test.. I have the volume of a cylinder and the method of area between two curves but this is out of my reach.... I don't know what I can try...


In the D&D 5th starter set scenario(Lost mine of Phandelver), there's a part where players can repel skeletons by saying a password (p.22). However, I cannot find where & how players learn this password in the scenario. Could you enlighten me here please?  Spoiler Alert !! The following is the script from the scenario book.     The three skeletons are animated and attack any creature that comes within 10 feet of the door leading to area 5 or the door leading to area 6, unless that creature is wearing the scarlet cloak of the Redbrands or speaks the password "Illefarn" (the name of an ancient elven nation, which once spread across much of the Sword Coast)

Spoilers! Careful, there are spoilers ahead. If you are playing the adventure Lost Mine of Phandelver or ever plan to in the future, please stop reading now.  Hello everyone,  This is a question related to my .  I'm DM'ing the Lost Mine of Phandelver adventure. We've just arrived at the Hideout      beneath Tresendar Manor, belonging to the Redbrands   And there is another point that is not explained in the book.  In Area 4      There are several skeletons. They will 'Attack unless that person is wearing a red cloak or speaks the password Illefarn'. Nowhere in the adventure does it detail where PC's can learn the codeword though. How are PC's supposed to know this?


Suppose the $\gcd(a,b) = 1$ and $c$ divides $a + b$. Prove that $\gcd (a,c) = 1 = \gcd (b,c)$.  This is relatively easy using Bezout's formula. See . But is there a way to do it without Bezout?

I am lost.   So far...  If $\gcd (a,b) = 1$, by Bezout's Formula  $ax + by = 1$  If $c|(a+b)$, then $cf = a+b$  Then,  $a (x-y) + cfy = 1$   $b(yx) + cfx = 1$  Am I on the right track? Any suggestions?


Here are two instances in a formal paper I submitted where my professor told me my semicolon  usage is incorrect.  He says that, in both instances, a period should be used.  Is he right?  I maintain that I've used them appropriately and at my discretion to indicate closeness of subject matter between two independent clauses.  Instance 1:     Baz Luhrmann, in his 2013 film adaptation of Fitzgerald’s work by the same name, represents its major characters in a manner mostly true to the novel; Nick, Gatsby, Daisy and Tom are somewhat polarized, however, in their speech and actions.      Instance 2:     In the novel, when Nick is “urged” (28) by Myrtle to go along, bribed with the promise of Myrtle’s sister, he responds “Well, I’d like to, but—” (28); in the film, he worriedly says, “No, no, no—that’s alright.”

I've seen a few questions on this site relating to semi-colons, which I believe I correctly understand, but what I'm not as clear about is colons.  For example:     The man ate the apple; it tasted good.   Is this not correctly also written as:     The man ate the apple: it tasted good.   In this case, what is the difference between the two sentences?


I recently edited some files, and i'd like for that change to be permanent. Not something as simple as setting the owner to root, but rather, making so I have no way possible to edit or remove said file.

How to make some file that contains crucial data protected? For instance, suppose I have some files that are important, is there any method or strategy to make these kind of file more protected on Ubuntu? I even want to make some files ask for a password whenever someone tries to open it. Does it affect the version of Ubuntu in terms of security policy? May I use any encryption algorithm externally? Regards.


Problem Hello! Recently I changed my bash PS1 to make it easy to see my current working directory/username. Unfortunately, this led to the following "features":  When nearing the end of the command prompt (about 3/4 of the way in), the cursor wraps back to the start and begins to overwrite text, sometimes on the previous line When using the up/down arrow keys to select previous commands, the cursor can jump to the middle of the screen.  See also I also found  which suggests an error in PS1... I believe this to be the case, however, this doesn't appear to fix the problems I'm seeing here. Details The output of echo $PS1: \[\e]0;\u@\h: \w\a\]\033[0;34m[\033[0m \u \033[34m: \W ]\033[0;0m%   Operating System / Hardware Ubuntu Linux 20.04 operating system, AMD x86 64 bit architecture.

Often when I start looking at history of commands some of the characters from a command displayed aren't erased, for example:  What's happening:  prompt$ some_command prompt$ some_commanother_command   What should have happened:  prompt$ some_command prompt$ another_command   I can't erase those characters and bash ignores them when executing the command. They also disappear when a new prompt is being displayed (after pressing Enter for example).  I asked other people who work on Linux at my workplace and they said that they have that problem sometimes too, but they didn't have an idea on how solve that issue.  I have Ubuntu 11.10 and I'm using guake. Here is my PS1:  \e[0;31m\u \A ${PWD##*/}\e[0;32m$(parse_git_branch)\e[0;31m$\e[m   where parse_git_branch is  parse_git_branch () {     git name-rev HEAD 2> /dev/null | sed 's#HEAD\ \(.*\)# (\1)#' }   As far as I know my colleagues have that problem even with less "fancy" PS1.


I applied and got a multi entry C Schengen visa from France valid for 3 months. My original trip was  France- 5N,  Austria- 3N,  Czech Republic- 1N,  Germany 6N,  France- 1N  However, we decided that we want to spend some time in Greece instead of France so now the itinerary is  France- 1N,  Greece- 4N,  Austria- 4N,  Czech Republic- 2N,  Germany 4N  France- 1N  At first I applied to France because I will be in Germany and France for the same amount of days and France is my port of entry. With the itinerary change, France is still my port of entry but I will be adding a different country and staying at some countries for longer/shorter that I  never mentioned to the embassy. Will they revoke my visa because I will be making these changes? I have heard stories about visas being canceled because the original hotel reservation was canceled. I am an Indian citizen living in the United States if that helps.

My route trip is Prague-->Berlin-->Vienna. I want to change the route to be Prague-->Berlin-->Paris.  Additionally, I already got my Schengen Visa, but after that I found a good deal in another hotel.    Can I change the first hotel I will visit before I travel?  If yes, is that going to cancel my visa or anything like that? Also I planned to go to Vienna and go back to my home from there. Can I change it and go to Paris instead?


I'm looking for a single word of phrase to describe someone intentionally acting dumb or intentionally over looking something obvious so they can deny responsibility or prevent themselves looking bad.  E.g. A person states that they hadn't consider that don't something would have an knock on effect that when the effect is completely obvious and was unlikely to have been overlooked.  I've seen the following suggested: "deliberately obtuse", "passive aggressive" & Blonde in a similar query on Yahoo, but it's not quite what I'm looking for.

What is a word for someone who is experienced and wise, but who deliberately acts naïve?    I don’t intend it for sarcastic use; I’m trying to describe someone succeeding in making people think that that person truly is naïve.   Is there a word for this?


Let $V_1,V_2$ are subspaces of vector space  $V$ . Differences of $V_1 \cup  V_2$ and $V_1 +V_2$ ?

I'm having a difficult time understanding this statement. Can someone please explain with a concrete example?


I have tried the following, copying my code from the IDE into SO. Copying the code and verfied that it is indented 4 spaces as requested by SO and then pasting into SO. I also went as far as to hand type everything from IDE into the SO manually building the code and it still gave me the below error. I could not find any good help to get past this error message and submit my code. I have tried to alter the format several ways. Thank you greatly for your assistance.

How do I post text so that it is formatted as code?  What do I need to do so that my code shows up properly — not escaped or removed — when posted? And how to get the correct syntax highlighting?     For more information, see "" in the .


For any two events $A$ and $B$, show that   $$(P(A\cap B))^2+(P(A\cap B^c))^2+(P(A^c\cap B))^2+(P(A^c\cap B^c))^2\ge\frac 1 4$$   I tried solving the question by writing $A \cap B^c = A - (A \cap B)$ and similiarly expanding the other brackets. But I am not able to proceed any forward.  I also tried applying the Boole's inequality and then squaring the respective terms, but still didn't get the required answer.  Can somebody help me with this question, please?  I would be extremely grateful.

Show that for any two events $A$ and $B$, $$(P(AB))^2+(P(AB^c))^2+(P(A^cB))^2+(P(A^cB^c))^2\ge\frac{1}{4}$$   Using the Inclusion-Exclusion formula, De Morgan's law and $P(AB^c)=P(A)-P(AB)$, I was able to expand the $\rm{l.h.s.}$ as $$(x+y)(x+y-4z)+2z(2z+1)+x(x-2)+y(y-2)+1\quad...\quad(*),$$ where $x=P(A),y=P(B)$ and $z=P(AB)$.  However I'm not being able to group the terms involved in the $\rm{l.h.s.}$ to form a 'suitable' expression and probably the way I have grouped them is not correct.  The expression $(*)$ is subject to the condition   $\max\{0,x+y-1\}\le z\le \min\{x,y\}$ and obviously $0\le x,y,z\le 1$, but I am unable to use this.      Is there an elegant/slick way to show the inequality? It probably can be shown without a lot of work and it's possible I'm missing something trivial here.


I recently purchased a PS4, and was told that if I had downloaded GTA V on PS3 (which I did), then it would transfer to my PS4 when I signed in, but I don't see the option to do so anywhere. Can I actually transfer a game from PS3 to PS4?

We have a large collection of downloaded games from the store, mainly PSX gen (Crash Bandicoot, Spyro, FF7 etc.) and I was wondering if we can move them/re-download them onto the PS4?


I know there are multiple packages for typesettings algorithms (algorithmic, algorithmicx, algorithm2e), and some other which are not exactly designed for this exact purpose but can be used as well (listings). What I don't know is which to choose.   What are the pros and cons of the different packages for typesetting algorithms? (I'm asking for an objective survey here.) Are there any clear differences among them? Which one is more "common" in academic papers?

I am looking for a package that will allow me to write pseudocode  of algorithms. The pseudocode may include mathematical symbols, like \forall, \in and subscripts. But I would like also to "talk" about variables contained in the pseudocode in my text, so be able to say "In figure ... variable foobar corresponds .." and make the word foobar have the same appearance as in the pseudocode example.  I found that with the listings package I can add mathematical symbols by using: \begin{lstlisting}[mathescape]. The problem with this package is that I don't know how to make just one word have the same appearance as the words appearing inside \begin{lstlisting} ... \end{lstlisting}.  Any ideas how to do this?  Or perhaps of another package that will help solve the above mentioned problem?


I just hit 200 reputations and saw big ads removed.  But they didn't bother me at all, so I would like to get them back to support the site.  Is there any way to do so ?

One of the "benefits" of earning 200 rep points is that fewer ads are displayed to you. Instead of seeing three zones (Leaderboard Top, Leaderboard Bottom, and Sidebar), you see only one (Sidebar).  Now I put "benefits" in quotes because I personally don't consider less advertising (especially on SO) to be beneficial. Of course, as the "ad guy", I really don't care because the loss of impressions are statistically negligible, but as a member I feel that I'm missing out on something.  We work hand-in-hand with each sponsor to make sure their ads are high quality and relevant, and we won't even talk to companies with a product/service that we know is a poor fit. And now that there's no more AdSense, that's the only thing we see.  There are so many awesome products/services that I've found through relevant ads, most of which solved problems I didn't even realize I had (or were solvable). , for example, has very recently "changed my life". And of course, there's no other way I'd find out about these, because I don't spend a whole lot of time reading reviews, etc.  So long story short... I think the "reduced advertising" thing should be changed to work as follows:      On the User Profile page, there would be a Checkbox that reads "Show Reduced Advertising". The Checkbox remains hidden until the member reaches 200 rep. Upon reaching 200, the box gets automatically checked.   Basically, it would work exactly the way it did before, except you get the option to turn off reduced advertising.  And yes, of course I'm biased. But still, Good ads are are a Good Thing.


Some of my questions weren't important and also my fault. They were downvoted. Even, no expected answer.  So, I've tried Google and found the answers were quite easy.  I'm also blocked from questioning because of the previous answered questions.  I've tried to delete them but they don't disappear / are not deleted permanently.  What can I do now? Those questions can't be edited. How to get the question opportunity again?  For instance, I want to delete this  .

If you are reading this, you may have been affected by one of our post quality bans. If so, it is important that you  to understand what has happened and how to regain the permissions that you lost. While trying to ask a question, one could see:  We are no longer accepting questions from this account. See  to learn more.  Likewise, for answers:  We are no longer accepting answers from this account. See  to learn more.   Why am I getting this message? Are deleted posts taken into account too? Is a question/answer ban the same as a suspension? How do I avoid getting a question ban? How long do I have to wait before I can post again? What can I do to release the ban? How can I reactivate my account? Can I simply create a new account? I'll just ask somewhere else on the SE network, and they'll migrate my question to the correct site! Will a ban on one Stack Exchange site affect my standing on other sites in the network? Does this apply to meta sites too? My account is in good standing. Why am I still blocked?


When do I run "apt-get update" on Ubuntu 18.04 LTS? Is it ever necessary under Long Term Support?  After reading the suggested duplicates I don't believe my question is a duplicate. I already know what apt-get update does, but that wasn't my question.

I am wondering what sudo apt-get update does?  What does it update?


My travel plan is Istanbul-Schengen-Morocco-Romania-Bulgaria. I have a double entry visa for Schengen valid till 27th May 2018. I exhaust my first Schengen entry when i enter Schengen zone from Istanbul. With my second entry for Schengen still valid, I wanted to know if i am allowed to fly from Morocco to Romania on the 23rd May 2018 and stay there for two days and further on fly to Bulagria on the 25th May 2018 and get a week long visa (or atleast two day visa considering last date of my Schengen Visa as 29th May).

Let's say I have a two entry Schengen visa from Greece, that is valid and both entries are unused, and I want to visit Romania.  Can I fly directly to Romania or do I have to go to Greece first, then from Greece to Romania?


Requirement : Standard users cannot update the status of a record that is already Registered (or post-registered phase). Example: Opp was already “Registered” but some standard user was able to change the record to “Open Won.” Need validation rule for this.   Note: "Stage" is a picklist under opportunity

There are 2 requirements:    standard users can’t update the status of a record beyond “open won” (so that only SF Admins or auto processes update “registered” and the stages beyond registration. Validation rule for this:    ~   AND(       $Profile.Name <> "System Administrator",      ISCHANGED(StageName),      OR(TEXT(StageName) = "Registered",     TEXT(StageName) = "Pre-Certified",     TEXT(StageName) = "Documentation, Submission",     TEXT(StageName) = "Performance verified",     TEXT(StageName) = "Appeals",     TEXT(StageName) = "Certification/ Closed Won")      )   Requirement 2: Standard users cannot update the status of a record that is already Registered (or post-registered phase). For us, some Opp was already “Registered” but some standard user  was able to change the record to “Open Won.”    I am looking for the validation rule of requirement 2 and which should align with first requirement also.  Thanks, Please guide.


I have some question about Non-Planar geometry  1. What is non planar geometry?  2. Why this happens after rendering?  Why did I get this line in the middle and the shading is different.

I think my question relates to a fundamental of 3D modeling that I haven't picked up on yet. It's very simple:  Let's say I have a flat quad. A plane on the XY plane inserted into am empty blender file is a great example. Now let's say I start moving each of the 4 vertices around on in any direction, especially the Z axis.   At this point, there would still be one face, but its extremely unlikely that the face would be planar (I just learned this word). So blender does its best to make sense of what this should look like.  The problem I'm having is that it seems like my quads are always like this, but they never look the way I want. There are edges and seams that look like they are dangling in space, and what tends to happen is that my mesh looks great when viewed from most angles, but if you look at it from just the right angle, you notice the dangling edges or sometimes even some kind of impossible geometry. And so I might try to nudge the problematic vertices around, but this often seems to either make it worse, or just hide the bad geometry until you see it from a different angle.  For me, this always seems to happen whenever I'm trying to move vertices to add roundness to something that is originally square.   There is another question on here about how to actually flatten the quads. That's great, and I might use some of the techniques mentioned there. My question is:   Why does this happen? (Can someone explain this better?) What are some tips and tricks to avoid this situation? What are some tips and tricks to mitigate this situation?   EDIT Here is an illustration:  The overall mesh as viewed from a distance looks decent (for my skill level)    But if you get closer and look from a certain angle...    Super close up:    The "edge" that is pointed to by the arrow is not actually an edge, but some kind of artifact created when blender tries to show the quad. The way the vertices are positioned, it shouldn't actually be possible to see the sliver of the face that I marked in red, since this face is supposed to be around the corner from the edges. The edges should form the silhouette on the right side of my figure.     Here is the side view. Maybe it is the angled topology that skews the face in a funny way?  But I'm not looking for help with this one particular issue, but rather a better understanding of why this happens, and ideas to prevent this in future models.


In physics class we learn that the normal or contact force exactly equals the force of earth's gravity pulling you to the center of the Earth and thus cancel each other out. I thought that the normal force does not exactly equal the force of gravity on an object.   The earth is rotating around its axis. That means that, for example, a book lying on a table has no constant velocity since its direction of motion is constantly changing with the circular motion around the Earth's axis. The centripetal force due to this rotation, for a book with mass of 1 kg is given by: $F=\frac{mv^2}{r}$. The speed of the rotation is 465.1 m/s and the radius 6,378,000 m. So this should give a force of around 0.034 N. This means there is a net force.   I thought this would mean that the normal force does not exactly cancel out the gravitational force. Is this true? For example does the normal force on a book, with a gravitational force (on the equator) of $9.78 m/s^2$ and thus a force of $9.78 N$ equal $9.78-0.034=9.746 N$ (or is it that if one talks about the gravitational acceleration, this effect has been taken in account? That is to say, when we talk about gravitational acceleration do we mean an experimental number, so that this effect has been taken in account, or the theoretical acceleration without the effect)? Could this effect be compared with the effect that you are being pushed to the side when a car makes a curve and that the book is like this ´tilt´ a bit upwards?  Thanks in advance

When I am on earth, the weight of my body is countered by the reaction of the ground. So, there is no net force acting on me.  But I am spinning with earth. But if there is no centripetal force then why am I spinning? And the equal air pressure on both side of my body won't be enough for me to stay in the same angular velocity as the earth.  Is it just conservation of angular momentum?


I am getting LNK1120 error, and I am not sure why. I am trying to use a template for int and double, that returns the corresponding type.   This is my Numerical_Analysis_Functions.cpp file  #include "Numerical_Analysis_Functions.h" #include <iostream> using namespace std;  template double  midpointRule<double>(double arr[], int);  template <typename T> double midpointRule(double arr[], int size) {      return 1.0; }   This is my Numerical_Analysis_Functions.h file  #pragma once  template <typename T> extern T midpointRule(T arr[], int size);   This is my main  #include <iostream> #include "Numerical_Analysis_Functions.h" using namespace std;  int main() {     double arr[4] = { 1, 2, 3, 4 };     midpointRule(arr, 4);       cin.sync();     cout << "End of Program.";     cin.get();     return 0; }

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 have searched quite a lot already but unfortunately didnt find any solution or hint yet. My problem is NOT that my computer starts/boots itself from standby mode. For this often discussed problem, there exists the commands powercfg -devicequery wake_armed and powercfg –lastwake.  But for me, the problem is, that when I press "Energy saving" in windows, then my monitor immediately goes black, but my computer keeps running. How could I find out what is causing this issue and which driver/software keeps my PC running? I only installed a new nvidia driver and some windows updates lately, and I disabled Windows 8.1 fast boot mode, nothing more.  Thanks in advance  EDIT:   powercfg /requests showing NONE everwhere VLC only in portable mode, so not running in the background powercfg -energy not showing any entries which say "preventing from sleeping" No print spooler entry, no Windows Media Player Network Sharing Service I also tried powercfg /requestsoverride driver srvnet System as an admin, but didnt solve the issue either HOMEGROUP --> Dunno, because I dont have any other computers in my network. Never used network stuff here.   WHAT TO DO NEXT???

Windows 8 is set to sleep after 30 mins, and it used to work, but recently it's started refusing to sleep. (I can still manually ask it to go to sleep without any issue.)    I was having issues a while ago, but it was with my network adapter. That's since been disabled, so it's definitely not that:    I've checked to see what devices are able to wake up my machine, but it only appears to be my mouse:    Which is odd, because I haven't recently changed my mouse, and more confusing still: The monitor does go to sleep just fine. If it was actually the mouse keeping my system awake, I'm pretty sure the monitor wouldn't go to sleep.  I've checked my Wake Timers, and nothing:    I've also checked my existing requests...  UPDATE: I found something. What to do with it, I don't know...    Note: Even when /requests says that there's "NONE" under every category, my machine still won't sleep(!).    In short: How can I tell what's preventing my computer from Sleeping?    UPDATE: Ok, so I now have a few more pieces of the puzzle. I came back to my computer and it was ASLEEP! Lawks! It seems that the only times it doesn't sleep is if VLC Player is open, even if a video isn't actually playing.  UPDATE UPDATE: Ok, so it won't sleep sometimes when VLC Player ISN'T running, either. Bah!


Trying to wrap my head around this one.   I have a custom object managed by an apex class that has a Process defined along with it. This process has an immediate action that calls an apex class that effectively does equivalent of webhook.  When I write a testClass for it, doing a basic CRUD test, it fails with this message: Methods defined as TestMethod do not support Web service callouts  How does one write a testcase for this?  adding some code:  public class with sharing WebHook {    public class Ids {        @InvokableVariable(label='Id')        public String idfield;    }     @InvokableMethod    public static void postIt(List<Ids> ids) {       Ids aid = ids[0];       Map<String, String> m = new Map(...);       m.put('idfield', aid.idfield);       System.enqueueJob(new QueueableCall('http://localhost:8000', 'POST', JSON.serialize(m)));    }     public class QueueableCall implements System.Queueable, Database.AllowsCallouts {          private final String url;         private final String method;         private final String body;          public QueueableCall(String url, String method, String body) {             this.url = url;             this.method = method;             this.body = body;         }          public void execute(System.QueueableContext ctx) {             HttpRequest req = new HttpRequest();             req.setEndpoint(url);             req.setMethod(method);             req.setBody(body);             Http http = new Http();             HttpResponse res = http.send(req);         }      } }  public class with sharing ClassA {     public static void addA(String a, String b) {         ObjA a = new ObjA();         a.a = a;         a.b = b;         insert(a);     } }   I'm trying to write a testclass for ClassA and it's erroring with message at top. How do I write tests for WebHook and QueueableCall to complete this test?

I have been struggling with this error for a few days now. I get this error every time I try to run a test for a method that has an httpCallout. I followed the architecture from  , but to no avail. I thought it could be something I was messing up in my code, so I copied all three of the classes from the documentation, and I am still getting the error when I try to run the test. All of the classes are on Salesforce API 29. Has anyone run into this before?


Gödel's completeness theorem: Given a set of axioms, if we cannot derive a contradiction, then  the system of axioms must be consistent.  Gödel's incompleteness theorem:'Given any consistent, computable set of axioms, there's a true statement about the integers that can never be proved from those axioms'.  Since the incompleteness theorem assumes that the given set of axioms is consistent, then, by using the completeness theorem shouldn't all statements derived from this set of axioms be true thereby rendering the claim that 'there exists a true statement that cannot be proved' false?

What is the difference between Gödel's completeness and incompleteness theorems?


I have script to run a jar, like shown below.  user="Tim Tom"; jarfile=./app.jar SC_CD="java -jar -Xms512m -Xmx2048m -DUSER='$user' $jarfile" nohup $SC_CD   And im geeting error message as   Error: Unable to access jarfile Tom   So, my understanding is, it is taking the word after space as jar name.  Therefore, my question is, How to pass param with space in it?

Or, an introductory guide to robust filename handling and other string passing in shell scripts.  I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some file names).  I encountered a problem such as the following:   I have a file name containing a space hello world, and it was treated as two separate files hello and world. I have an input line with two consecutive spaces and they shrank to one in the input. Leading and trailing whitespace disappears from input lines. Sometimes, when the input contains one of the characters \[*?, they are replaced by some text which is is actually the name of files. There is an apostrophe ' (or a double quote ") in the input and things got weird after that point. There is a backslash in the input (or: I am using Cygwin and some of my file names have Windows-style \ separators).   What is going on and how do I fix it?


I am aware of the "comment-timeout" which prevents the user to edit comments after 5 minutes edit window.  But, it doesn't prevent the user from deleting and posting a new comment with modified content after 5 minutes.  So, what's the use of that 5-minute comment editing timeout if users can delete and post modified comment, ?


Suppose $1<p,q<\infty$, $\dfrac{1}{p} + \dfrac{1}{q}=1$, $(X,\Sigma,\mu$ is $\sigma$-finite measure space and $g$ is a measurable function such that $fg \in L^1(X)$ for every $f \in L^p(X)$. Prove that $g \in L^q(X)$.   I have no idea where to start this question. It seems to me a lot like a close question to the Riesz Representation Theorem, or an application of it. Any help is much appreciated. I'm just refreshing many questions I haven't looked at in quite some time for preparation of my Analysis Qualifying Exams.

Let $f$ be a measurable function on a measure space $X$ and suppose that $fg \in L^1$ for all $g\in L^q$. Must $f$ be in $L^p$, for $p$ the conjugate of $q$? If we assume that $\|fg\|_1 \leq C\|g\|_q$ for some constant $C$, this follows from the Riesz Representation theorem. But what if we aren't given that such a $C$ exists?


I know this is a duplicate question but the other answers didn't explain clearly my problem. The talks about no hair theory for explaining the communication and information problem of matter inside the black hole. But I just want to know how it is possible that a field can escape from a black hole. It is not clear where an electric field is made of and perhaps that is the lack of information which can answer why it can escape a black hole.

By the "No Hair Theorem", three quantities "define" a black hole; Mass, Angular Momentum, and Charge. The first is easy enough to determine, look at the radius of the event horizon and you can use the Schwarzschild formula to compute the mass. Angular Momentum can be found using the cool little ergosphere Penrose "discovered". However, I don't know how to determine the charge of the black hole.   How can an electromagnetic field escape the event horizon of a Reissner-Nordström black hole? Is there any experiment we could theoretically do to a black hole to determine its charge?


I have a few subscribers who has changed their email addresses in our system which has been reflected in synchronized data extensions in Marketing Cloud. On email send SFMC is sending email to their old email addresses. Upon investigation, I found that All Subscribers data has not been updated with the new email address for the subscribers who changed their email addresses in Salesforce Cloud (CRM).  Please find below the details for one of the records.  Subscriber Key: 000000000000BBBAA1 New Email address (changed on 13/12/2016): NEW@test.com  Old Email address: OLD@test.com   I have raised a case with SFMC and they came up with a solution to enable the business rule in our account to update the records in All subscribers data as soon as the record is updated in CRM.  Can someone help me to understand the impact of this business rule going forward?

We have set up our Sales Cloud - Marketing Cloud integration where Contact ID is used as the subscriber key.  What we've noticed is when we have contact ID as the subscriber relationship on our sendable data extension, Marketing Cloud will reference contact ID on All Subscribers list and if data matches, it will send to the email address listed on All Subscribers and not to the one on the data extension.  This has caused us headaches for a number of reasons:   Email addresses always change so the one on All Subscribers is out-of-date. Whilst preference center can update a recipients address and write this back to All Subscribers that not how most addresses are updated by the user Email address is typically updated in Sales Cloud instance and migrated to Marketing Cloud either through imports or via synchronized data extensions.  It does not map directly to All Subscribers. Marketing Cloud users assume (and quite rightly) the address listed on the data extension is what will be used in the send. Not the one on All subscribers.   Anyone else experienced this? Any solution to resolve this issue?


Is there a way to Insert/Upsert a Global value set in apex?

Can someone tell me how to create and update Global value set using tooling API? No sure what so send in request body.


While trying to start my Lenovo laptop I get the screen you see in the image below, I’m not able to to do any other thing or get the Ubuntu console. Also I'm not able to start using the Ubuntu CD.

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


I need to type Backus-Naur form in LaTeX document. I found several packages on CTAN:    seems to not work with TeXLive 2009  does not align the declaration, etc. There is a module for ConTeXt,    Is there a package for modern LaTeX, or should I just use hand-formatting via verbatim?

I googled and found two packages:   mdwtools bnf   Unfortunately, both of them have extremely poor documentation. There are only one to two examples for each one, which makes it hard to follow. Furthermore, none of them shows how to indent the grammar properly, rather than just setting up the environment to have a nice look. I wonder is there a major package for writing BNF, or we can just manually use tabbing to handle the indentation? Thank you.


Say, I have a main (large) bibliography file, Large.bib, I include in TeX as  \bibliography{Large.bib}   how do I crate another sub-bibliography file, SubBib.bib that contains the entries which are being cited in the main TeX?

Normally, LaTeX will only create references for the BibTeX entries cited in the text. Is there a way of extracting these entries into a different .bib file automatically? For example if I have a .bib file with two entries, and only one is cited in a particular text, I need a way of creating a new .bib file with just that reference.


I am trying to realize a certain mathematical combination into Javascript but can find the best way to do it. What I am trying to achieve is finding the sum of combinations(consisting of 3 elements) out of N. For example, how can I find sum of all possible combinations consisting of 3 elements out of 5? Manually it looks like this: Selections: A,B,C,D,E  - all of them are numbers All possible 3 out of 5 combos are as follows: ABC ABD ABE ACD ACE ADE BCD BCE BDE CDE ABC means A * B * C The sum of combos in its simplified form will look like this: AB(C+D+E) + AC(D+E) + ADE + BC(D+E) + BDE + CDE. I have tried the following code but it did not work out: function calc(arr) {   var total = 0;   for (let i = 0; i < arr.length; i++) {     let sum = 0;     for (let j = i + 1; j < arr.length; j++) {       sum += arr[j] + arr[j + 1] + arr[j + 2];     }     total += sum * arr[i] + arr[i + 1] + arr[i + 2];   }   return total; }  var arr = [2, 3, 4, 5, 6]; console.log(calc(arr));

I want to write a function that takes an array of letters as an argument and a number of those letters to select.   Say you provide an array of 8 letters and want to select 3 letters from that. Then you should get:  8! / ((8 - 3)! * 3!) = 56   Arrays (or words) in return consisting of 3 letters each.


Background  I have a method that returns a Linq expression with the following signature:  public static Expression<Func<string, bool>> GetStringFilterExpression(IEnumerable<string> fields)   Which I then place into a local variable:  var filterby = GetStringFilterExpression(new[] {"Copy*Z"});   Given a Linq2Sql data context db and a table DbItems, this allows me to do this:  var names = db.DbItems.Select(d=>d.Name).Where(filterby); var result = db.DbItems.Where(d=>names.Contains(d.Name);   Or I can use this helper method  public static IQueryable<T> MatchesFilter<T>(IQueryable<T> query, Expression<Func<T, string>> selector, Expression<Func<string, bool>> filter) {     LambdaExpression lambda = (LambdaExpression)selector;     var predicate = Expression.Invoke(filter, selector.Body);     var lambdaPredicate = Expression.Lambda<Func<T, bool>>(predicate, lambda.Parameters);     return query.Where(lambdaPredicate); }   And perform a slightly more concise query:  var result = MatchesPattern<DbItems>(db.DbItems, d=>d.Name, filterby);   Both methods work, returning the same results, and running the expression as a correctly filtered SQL query (no local collection).  Goal  What I would like to do is use the function inside the normal .Where() clause, so it can be combined with other logic or invoked on more than one field, for example:  var result = db.DbItems.Where(d => filterby(d.Name) && d.Active);   But to do that, I have to use a Func rather than an Expression. I tried unwrapping the expression like so:  public static Func<string, bool> CreateStringFilter(Expression<Func<string, bool>> filterby) {     return p => filterby.Invoke(p); }  var inlinefilter = CreateStringFilter(filterby);   Which does allow this to work:  var result = db.DbItems.ToList().Where(d => inlinefilter(d.Name));   However, that requires pulling the whole table down into a local collection.  If I remove .ToList(), I get a "no supported translation to SQL" error.     Method 'System.Object DynamicInvoke(System.Object[])' has no supported   translation to SQL.   Even though it's the exact same code that runs as SQL when it's wrapped in the Expression.  Is there any way to get this to work as an inline string function in the .Where (or .Count, etc.) clause against the live data context instead of a local collection?  Follow-up/Workaround  Marked as duplicate, but I didn't feel the linked question answered this question, which is how to use an existing string,bool Expression against an arbitrary property (vs. creating custom property-aware expression trees in the accepted answer to the other question).  Here's the workaround I came up with:  Add another helper method like this:  public static Expression<Func<T,bool>> PropFilter<T,T2>(Expression<Func<T, T2>> selector, Expression<Func<T2, bool>> filter) {     LambdaExpression lambda = (LambdaExpression)selector;     var predicate = Expression.Invoke(filter, selector.Body);     return Expression.Lambda<Func<T, bool>>(predicate, lambda.Parameters); }   Then I can create property-specific filters based on the original string filter, and chain them like this:  var filtername = PropFilter<DbItems, string>(d => d.Name, filterby); var filterdesc = PropFilter<DbItems, string>(d => d.Description, filterby); var propfilter = filtername.Or(filterdesc);   Finally, I am able to invoke that filter in Linq and combine with inline property filters like so:  var result = db.DbItems.Where(propfilter.And(d => d.Active));   I gather that's as close as I'm going to get to the original desired syntax.

I have two expressions of type Expression<Func<T, bool>> and I want to take to OR, AND or NOT of these and get a new expression of the same type  Expression<Func<T, bool>> expr1; Expression<Func<T, bool>> expr2;  ...  //how to do this (the code below will obviously not work) Expression<Func<T, bool>> andExpression = expr AND expr2


If $p$ is an odd prime, prove that $1^2\cdot3^2\cdot5^2\cdots(p-2)^2 \equiv (-1)^{(p+1)/2} \pmod p$  Then $$1^2\cdot3^2\cdot5^2\cdots(p-2)^2={1/16} (p-2)^2(3p-1)^2\tag{1}$$   Now since $p$ is odd then $(p+1)/2$ is even and $(-1)^{(p+1)/2}=1$.  Now I tried substract $1$ from $(1)$ to find out if the result is a multiple of $p$. But I can't get the answer any suggestions.

I also have to prove this for $$2^2 \times 4^2 \times 6^2 \cdots \times (p-1)^2 \equiv (-1)^{(p+1)/2} \pmod{p}$$ I made some progress so far and got stuck. I said that since p is odd, $(p+1)/2$ is even. Then we can say that $(-1)^{\mathrm{even}}= 1$, so $(-1)^{(p+1)/2}\pmod{p}$ can be written as $1\pmod{p}$. I know that the product of odds is odd and the product of evens is even, but I cant prove that the left side of this equation in either case is congruent to $1 \pmod{p}$. Any help here would be greatly appreciated.


Here is my current command:  */30 */1 * * * wget http://mywebsite.com   But it doesn't work as expected. Expected period is every 90min. How can I do that?  Noted that this doesn't work either:  */90 * * * * wget http://mywebsite.com

How can I set cron to run certain commands every one and a half hours?


I am using an Asus ROG(GL553VE) and it's complicated with installing Ubuntu. I changed grub's cmdline linux default to  GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash nouveau.modeset=0 tpm_tis.interrupts=0 acpi_osi=Linux i915.preliminary_hw_support=1 idle=nomwait acpi=force”   And I can't update it.  sudo update-grub Sourcing file `/etc/default/grub' /usr/sbin/grub-mkconfig: 10: /etc/default/grub: splash: not found   MY GRUB FILE ---->  # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. # For full documentation of the options in this file, see: #   info -f grub -n 'Simple configuration'  GRUB_DEFAULT=0 GRUB_TIMEOUT_STYLE=hidden GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash nouveau.modeset=0 tpm_tis.interrupts=0 acpi_osi=Linux i915.preliminary_hw_support=1 idle=nomwait acpi=force” GRUB_CMDLINE_LINUX=""  # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"  # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console  # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' #GRUB_GFXMODE=640x480  # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID=true  # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_RECOVERY="true"  # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1"

Yesterday I'd installed new driver for my sound card and today the Sound doesn't work. I'd found an answer for this problem and fixed it in /etc/default/grub, but now when I try sudo update-grub it comes this error:  /usr/sbin/grub-mkconfig: 7: /etc/default/grub: splash: not found   This is my grub file:  # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. # For full documentation of the options in this file, see: #   info -f grub -n 'Simple configuration'  # MANUELL EINGEFUGT GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash pci=use_crs“  GRUB_DEFAULT=0 GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` #GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" GRUB_CMDLINE_LINUX="splash quiet"  # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that  obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD .  ..) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"  # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console  # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports  via VBE # you can see them in real GRUB with the command `vbeinfo' #GRUB_GFXMODE=640x480  # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter  to Linux #GRUB_DISABLE_LINUX_UUID=true  # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_RECOVERY="true"  # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1"   I add this line:  GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash pci=use_crs“   And I commented this line out:  #GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"   I am using Ubuntu 16.04 LTS.


I want to get text in between START & STOP. Remaining text should be deleted, like some_text_1 and some_text_2.  some_text_1 some_text_1 . . . START --- Values that I want to get ... STOP some_text_2 some_text_2   From my findings, sed does similar job, but only oposite, like: sed '/START/,/STOP/d' file which would give me everything else then content in between START & STOP.  Any idea?

How can I select first occurrence between two patterns including them. Preferably using sed or awk.  I have:  text something P1 something content1 content2 something P2 something text something P1 something content3 content4 something P2 something text   I want the first occurrence of the lines between P1 and P2 (including P1 line and P2 line):  something P1 something content1 content2 something P2 something


If a sequence is such that $a_k$ is arithmetic mean of its two immediately preceding terms. Show that the sequence converge. Find the limit of sequence  I got to see that the odd sub sequence is increasing and bounded above                  by $a_2$ and even sub sequence decreasing and bounded below by $a_1$. Now the sequence is convergent.  Bow how to find the limit of sequence.

We have a sequence of numbers $x_n$ determined by the equality   $$x_n = \frac{x_{n-1} + x_{n-2}}{2}$$  The first and zeroth term are $x_1$ and $x_0$.The following limit must be expressed in terms of $x_0$ and $x_1$ $$\lim_{n\rightarrow\infty} x_n $$  The options are:   A)$\frac{x_0 + 2x_1}{3}$ B)$\frac{2x_0 + 2x_1}{3}$  C)$\frac{2x_0 + 3x_1}{3}$ D)$\frac{2x_0 - 3x_1}{3}$  Since it was a multiple choice exam I plugged $x_0=1$ and $x_1=1$. Which means that all terms of this sequence is $1$,i.e, $$x_n=1, n\in \mathbb{N} $$  From this I concluded that option A was correct.I could not find any way to solve this one hence I resorted to this trick. What is the actual method to find the sequence's limit?


I am pretty new to Angular and I am writing a simple if statement to check if my property isn't one 10 things. Is there a Not In or filter from enums or from a list?  public type: string; if(type === '1' || type === '2' || type === '3') || type === '4'){ // do something } else { //do something else }   I am looking for something simple if we can use like  if(type not in (1,2,3))   What is the best way to check the scenario like this against the string?

What is the most concise and efficient way to find out if a JavaScript array contains a value? This is the only way I know to do it: function contains(a, obj) {     for (var i = 0; i < a.length; i++) {         if (a[i] === obj) {             return true;         }     }     return false; }  Is there a better and more concise way to accomplish this?


Consider a particle of mass $\text{m}$ fired from below into a bob of mass $\text{M}$ of a long, simple pendulum. The particle remains inside the bob and the bob rises through a height of $1.8\text{ m}$. What was the speed of the particle just before striking the bob?  I took the bob, the particle and the earth to be in a system and reasoned that their total mechanical energy must be conserved, since no external forces act on the system and all internal forces are (I think) conservative. Then, I set my reference line for measuring potential energy to be at the level of the bob before the collision. The kinetic energy of the system just before the collision must be equal to the gravitational potential energy at the highest point of the bob's motion. $$\begin{align}\frac{1}{2}mv^2&=(M+m)gh \\ v &= \sqrt{\frac{2(M+m)gh}{m}} \end{align}$$ However, my textbook uses the principle of conservation of linear momentum and the laws of kinematics:  If $\text{V}$ is the velocity of the combined mass after the collision, $(M+m)V=mv$. This gives: $$V=\frac{mv} {M+m}$$ As the string becomes loose and the bob goes up with a deceleration of $\text{g}$, coming to rest at a height $\text{h}$, we can use the equation $v^2=u^2+2ax$. $$h=\frac{V^2}{2g}=\frac{m^2v^2}{2g(M+m)^2}$$ $$v=\frac{M+m}{m}\sqrt{2gh}$$  Why did we get a larger answer this time? My intuition is that be conserving the mechanical energy of the system in the first method, I ignored possible energy losses in the deformation of the bob. Is my intuition correct?

I am stuck in a question where energy conservation is failing and momentum conservation is correct. I think I might be doing something wrong, that's why I'm asking this question. The problem is as follows:     A bullet of mass $25\,g$ is fired horizontally into a ballistic pendulum of mass $5.0\,kg$ and gets embedded in it. If the centre of pendulum rises by a distance of $10\,cm$, find the speed of the bullet.   (H.C. Verma, Centre of Mass, Q47)     Let the mass of the bullet be $m=25\,g$. Let the mass of the pendulum be $M=5\,kg$. Let the peak height be $h=0.1\,m$. Let the initial and final velocities be $u$ and $v$ respectively.  Method 1: (Momentum Conservation)  $$mu=(M+m)v \implies v=\frac{mu}{M+m}\\ \text{Also, }\frac{1}{2}(M+m)v^2=(M+m)gh\\ \implies u^2=2\biggl(\frac{M+m}{m}\biggr)^2gh\\ \implies u=201\sqrt2 \text{ m/s}$$  Method 2: (Energy Conservation)  Since both the masses move together after the collision, and because the velocity at highest point is null, therefore: $$\frac{1}{2}mu^2=\frac{1}{2}(M+m)v^2=(M+m)gh\\ \implies u^2=2gh\biggl(\frac{M+m}{m}\biggr) \implies u=\sqrt{402}$$    To summarize myself, I am curious about the following: Why do the results differ? Shouldn't the energy be conserved as well as the momentum? Since it should be, then what is the flaw in my calculations?


How can I replace the line break of a textbox (multiline-box) by the html's
?  This is my code:  string output = tb_Notizen.Text.Replace("\\r\\n", "
");   Whats wrong here?   I already tried it with \r\n but it didn't worked too...

How can I replace Line Breaks within a string in C#?


I can't find an RPG or table top session were I am, Are there any good resources to find one?

I'd really like to learn how to play pen-and-paper RPGs.  I know that it takes a few players to actually sit down and play, but I'm not at all sure where to find more gamers.  How do I find existing groups to join? Or, are there any resources online that may help me find existing RPG groups or players?


I am planning to do a study that uses binary dependent variable, such as a person is either in the labour force or not in the labour force. The function will have independent variables, for example age, gender, etc. It will based on primary data with more than 100 sample units. Should I use logit model or probit model?

What is the difference between  and ?  I'm more interested here in knowing when to use logistic regression, and when to use Probit.  If there is any literature which defines it using , that would be helpful as well.


I'm getting errors like  Err http://ppa.launchpad.net YOUR_UBUNTU_VERSION_HERE/main Sources                404  Not Found   Is it actually supposed to say YOUR_UBUNTU_VERSION_HERE, or is there some kind of an error that keeps it from writing my Ubuntu version?

I have unistalled and reinstalled the Ubuntu Software Center as per info I found in a similar thread and I got the same response about line 91 or something like that.  I just tried to upload a screen shot but since I'm new it won't allow me to.  I also can not figure out how to cut and paste anything so I have to hand type what the error screen says, both when I attempt to open the software center and nothing happens, when I try to enter commands into the terminal to uninstall, reinstall, whatever I get the same following:  COULD NOT INTITIALIZE THE PACKAGE INFORMATION An unresolvable problem occured while initializing the package information Please report t:his bug against the 'update-manager' package and include the following error message: 'E: Malformed line 91 in source list/etc/apt/sources.list (dist parse)  E: The list of sources could not be read.,  E: The package list of status file could not be parsed or opened.   How do I report bugs?  What can be done about this.  I have searched and everything everyone says to do leads me back to the same line error message.  So, I don't know how to get to line 91 in the source list; to tell you what it says. Sorry, I'm really new to this. That is what I need is to find out how to get there and fix what it says. I would really like to NOT have to re partition my hard drive and start from scratch, so I'm really looking forward to getting this problem solved. I need to be able to install new software.


I have just installed Ubuntu 20.04.1 LTS as a dual boot (with Windows 10) on my newly aquired Lenovo IdeaPad C340, and I have two problems. The first one is that when I start it (or restart it) it sometimes just freeze on a black screen and I can't do anything but switch it off manually (by presing the start button). I think it comes from ubuntu, but I did not use my Windows 10 boot many times, so I can't tell if it actually happens with windows 10 too (it yet). Second problem, still at start, it happens that the cursor of my mouse does not appear. I can still use the touchscreen but any click on something else than the hub where are located the power off button etc. does not work. I found that I could stop the problem by closing the session and opening it again, but I don't know how to stop it once for all. Does anybody have a solution? Or at least a suggestion? Thank you for any help!

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


Here the function is $$f(x) =\frac{\sin{x}}{x}.$$ We see that the right hand limit equals the left hand limit but does $f(0)$ exist?

Is $\sin(x)/x$ continuous at $x=0$,(perfectly, not tends to)? The function has right hand and left hand limit same and equals 1 but what happens at perfect zero?it should be undefined. Is it?


I want to experiment to prepare the pork ribs in Weber Kettle charcoal grill on a minimum possible temperature. What is the minimum internal temperature measured inside the meat (not air temperature) for pork ribs to be safe? By safe I mean meat to be prepared so that it is safe to eat.

What general rules do I need to follow to keep my food safe? How do I know what temperature to cook something to, or whether my food is safe at room temperature?


There are particles in a medium. When these particles oscillate with SHM motion, a flow is formed. That is called a wave.  But when there is no medium, there is no oscillation. That means no flow. Eventually no wave!   But electro magnetic wave is formed without any medium. How is it possible?  Again so many said,"EM waves are the oscillation of EM field. " Oscillation of particles mean "particles are getting down and up continuously". Then what does "oscillation of EM field " mean?

As I understand it, electromagnetic waves have two components which are the result of each other, i.e., when a moving electric charge creates a changing magnetic field at point X then a changing electric field is created at point Y and this repeating process is what creates EM waves, so therefore, it requires no medium. Is my understanding correct?  One thing that I'm surprised to know is that light is also called an electromagnetic wave.  Does this include light of any kind, for example: light from a bulb, a tube, and also from the Sun? How do they contain electric and magnetic fields?


According to my knowledge, the indefinite article 'a' must never be used before a proper noun. But I recently heard the English sentence: "Every civilian should be a Mahatma Gandhi to his society".  As per my knowledge, "Mahatma Gandhi" is a proper noun here and 'a' is the article.   Believing the speaker to have a good grasp of English, I now have this doubt: are there any occasions where it is proper to have an indefinite article before a proper noun?  Please advise me.

Sometimes, on the internet, particularly in online games, I see people using the  indefinite article before someone's name: "I see a Joey" or "I hug a Polly". I know some of these people and I'm positive that they are from English-speaking countries, which means it is not a mistake, they do it intentionally.  I was always taught that articles are not used in front of people's names. Maybe it is some sort of slang? What does it mean, when the indefinite article is put in front of someone's name?  Edit: There is a group of people standing somewhere. And somebody, named Joey, appears. They all know Joey. And someone in this group says "I see a Joey". So it is used when someone sees his or her friend. But I don't understand why they use the indefinite article here.


I know how to make things spawn as they follow an object, but is there any way to make them spawn once lets say a snowball hits its target?  I am working on a way to make snowballs that spawn tnt upon hitting their target.

I am trying to make a snowball that triggers a command when it hits a player in 1.15, but I don't know how to do that. When I do execute at @e[type=snowball] run gamemode spectator @a[distance=..2] it only runs the command if it goes right next to them.


Take as an example the sentence: "The monk is skinny, his arms lean from years of cardiovascular exercise." I've seen similar sentences and am curious about the grammar, since a similar sentence (with a comma splice) would be: "The monk is skinny, his arms are lean from years of cardiovascular exercise." Is this wrong (the first example - I know the comma splice is often frowned upon though controversial)? I've seen some serious authors do this so I assume it's not but I don't know how it works.

"Thirsty, we drank. Hungry, we ate. Tired, we slept."   Is there a name for this form of writing? Is it a recognised literary device?


I'm running a Raspbian on a bunch of Raspberry Pis. They each have a unique hostname set in /etc/hostname and the dhcp client correctly registers that name with my router.  The problem I'm running into stems from having these Pis connected to the same network, and then same DHCP server, via ethernet and WiFi - There is a race-like condition that means the rest of the network, when using names to address these Pis, can't deterministically prefer the ethernet connections over the WiFi.  I'd like to make the Pis report a different hostname to the network DHCP server when obtaining a lease based on which interface they connect with. This seems to be possible in a static way by adding a lines like the following to /etc/dhcp/dhclient.conf.  interface "wlan0" {   send host-name "MyHostname-1234-WiFi"; }   The problem I'm looking to solve is how to define that line programmatically. Something like this:  interface "wlan0" {   send host-name "<hostname>-WiFi"; }   Looking into the docs for dhclient.conf(5), it suggests I can use the concat function from dhcp-eval(5) but I'm not having success. I'm trying this:  interface "wlan0" {   send host-name concat(gethostname(), "-WiFi"); }

Actually I want to dinamically assign bootfile-name based on clients MAC.  I have tried this config:  option bootfile-name concat( binary-to-ascii(16, 8, "", substring (hardware, 1, 6)), ".cfg");   But this is wrong config (as dhcp server isn't starting at all). If instead of concat(...) I put just real filename (e.g. "000102030405.cfg") everything is ok. But this is not what I need. Is there any way to dynamically set bootfile-name?


Is the function just undefined or it has the value of the limit? I am just unable to understand which case it is ..

In fact the real question is: Does $\lim\limits_{n\to\infty}1^{n}=e$?.  I know that   $$ \lim\limits_{n\to\infty}\left(1+\dfrac{1}{n}\right)^n=e, $$  So, can we say that $1^\infty=e$?  And, by logic, This product  $$\underset{\text{infinity times}}{1\cdot1\cdot\ldots\cdot1},$$ gives $1$ not other value.


I am now taking log backups daily after a long gap(1.5 years). Now when I run,  DBCC SQLPERF('logspace')   Result,  Database  Log Size (MB)   Log Space Used (%)    Status master     1.742188     64.09753               0 tempdb     51.17969     33.19341               0 model      0.9921875        48.4252            0 msdb       4.554688     55.6711            0 MyDb       15618.68     0.7029594              0   Should I shrink the log file. If yes then how?

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


There are many new question, even limited to a field. A new method, to see which one is interesting, could be to display the reputation of the person who upvoted and has the largest reputation among upvoters. (Or, to protect privacy, some rounding of this number.) Then new questions could be filtered using this upon demand, or everyone could see the ones already upvoted by someone whose reputation is at least 10% of his own reputation.

Takeaway: Are 4 inexperienced users more reliable than 3 experienced users? A high rep doesn't ensure you are smarter, but it makes you the safer option.    I went to SuperUser to see what suggestions can be found for different Malware-removal Applications.  was right on target, and sported five answers, with a total of 9 up-votes.  All of the answers were provided by low-rep users, and that leads me to recognize that the up-votes may be a similar case. Just as answers aren't always equal, neither should up-votes be. The top answer currently has 4 up-votes, and the second most popular answer currently has 3 up-votes. The people who voted in the 3, may be more reputable than those who voted in the 4. Am I communicating this clearly?  I'm not asking that we be told who voted for a particular question, but I am asking that we be told what type of reputation they had. If the 4 votes come from 4 users with less than 300 rep, and the 3 votes came from two users with 300 rep and 1 with 10k rep, the 3 votes should appear stronger by the standards of the system.  Right now I'm worried about accepting the top-voted solution simply because I fear the up-votes may be from people with similar rep to those providing the answers - that doesn't make them wrong, only less-reliable by the standards of the stackexchange engine.  Can we see the sum of rep for  the votes? (Data in parenthesis would not be visible)   4 Votes (Ted • 72 | Bill • 183 | Carl • 423 | J • 100) = Power of 778 3 Votes (Bob • 19,123 | TJ • 283 | Mike • 8,923)       = Power of 28,329  So in this case, you wouldn't see who voted, only that their rep-sum was 778 and 28k.   4 Votes : 778 3 Votes : 28k  I'm not tied to this way of indicating the vote-power, but some method is better than no method.  Another concern is that higher-rep users (having been around longer) participate in voting less-frequently than new-comers do. After all, we're not trying to gain badges, build rep, etc. As a result, it's more likely that a low-rep users will cast a vote than it is a high-rep user. Does that follow logically?    Rebuttal     Reputation (From the SO-FAQ)      Reputation is a (very) rough measurement of  how much the Stack Overflow community trusts you. Reputation is never given, it is earned by convincing other Stack Overflow users that you know what you're talking about. (emphasis added)    "Rep has nothing to do with credibility, competence or knowledge!" - John Smithers     I agree. But it does have to do with "how much the SO community trusts you." Granting that, some votes are more trustworthy than others. Because they come from users who have convinced "other SO users that they know what they're talking about."  "The purpose of anonymous voting is that all votes are valued equally, whether they come from Jon Skeet or from some new person." - devinb     That is clearly not the case though. If SO operates by labeling some users more "trusted" than others (which it does), then that would mean some votes are trusted more than others. I would trust Jon Skeet to suggest a good programming book than I would two freshmen. It's irrational to suggest Jon Skeet will offer the best recommendation but that isn't what is being argued here. Only that Jon Skeet is the safer choice given his reputation.  "Just because a person has reputation does not mean they have more technical knowledge." - yshuditelu     I agree, but it does mean they are the safer source than somebody with no rep. That is, according to the SO-system.


I am using find -type f command to recursively find all files from a certain starting directory. However, I would like to have some directories prevented from entering and extracting names of files inside. So basically I am looking for something like:  find . -type f ! -name "avoid_this_directory_please"   Is there a functioning alternative to this?

I need to exclude .git from my find search. To achive that, I am using the -path ./.git -prune switch:  $ find . -path ./.git -prune -o \( -type f -o -type l -o -type d \) | grep '.git' ./.git   However, even though this skips the contents of the .git directory, it lists the directory itself. It works when I add -path ./.git -prune -o -print -a  find . -path ./.git -prune -o -print -a \( -type f -o -type l -o -type d \) | grep '.git'   Why is this necessary. I thought that both commands should have same output. The second syntax is quite ugly.


It would be nice if Stack Overflow (and its brethren) visually indicated when there was activity on one's account, as, e.g., att.net/yahoo does:    That way I wouldn't have to interrupt my work to check it, I could just glance up and see.

I'm usually running many different StackExchange sites in Firefox using tabs (using ReloadEvery to update every 5 minutes).  Right now to check for activity, I have to manually click on the tab to see if the envelope is lighted.  How about making the icon on the tab i.e. the title text change in some way, denoting that you have activity on the page?  We already add a message count for the chat tabs, so this shouldn't be very complicated.  Possible Example:


I know about session and using it well. I know to use the session I should put the session_start() top of each page that I want to use the session. But I found a problem in understanding of an issue.   Consider we have a bank that it called A bank and I want use from its payment gateway.Also consider we have a user that its username is B and he\she want to buy a product form the store.  At first, when the login operation is successfully, the login.php file will get the session from the user and  will save the $username value in the $_SESSION[login_user] variable.   We know that the  $_SESSION[login_user] variable is a global variable. This means that if the username is B and login operation is successful as the result the  $_SESSION[login_user] will get the B value and if we use the  $_SESSION[login_user] in each php file, the value in the $_SESSION[login_user] is B.  And then consider the user clicks the buy button and the store redirects the user to the payment gateway and he/she can buy a product successfully.Now the payment gateway sends information about payment to the server. Now the big problem is that in here, the user does not send a request to get the his/her session. In here, the payment gateway from the A bank requests and sends information to the store.  Now I want to save the username that has purchased in the database.  I do not know What do I do. Since there is no a good tutorials about this issue, please guide me.

I have an app using PHP and the PayPal API. The basic way it works to get a payment is that you do a web service call to PayPal to get a token and then do a browser redirect to PayPal with that token for the user to pay. After the payment details have been confirmed, PayPal redirects back to the URL you originally set in the service call.  This all works, millions of people use it every day, et cetera.  Strange thing is, when PayPal redirects back, the PHP session is gone. It's a .  First question: why is this happening? Both pages are on the same domain, both use HTTPS. The session works for all requests up until the PayPal redirect back.  The linked forum thread suggests a workaround, to persist the session ID in the PayPal request and then to retrieve it later and restore the session. Great, except it doesn't seem to work.  I can add some log statements:  log(session_id());   before and after the various redirects. When coming back from PayPal, I log some more.  log("session id is " . session_id()); $session_id = get_session_id_from_paypal(); log("setting it back to " . $session_id); session_id($session_id); session_start(); log("session id is now " . session_id());   The result is not at all what I'd expect:     session_id is fc8f459a186a3f4695ff9ac71b563825   setting it back to 82460dcf8c8ddd538466e7cb89712e72   session_id is now 360ba3fd99d233e0735397278d2b2e55     Second question: why is the session id not at all what I set it to? What am I doing wrong? Or, at least, why do none of the session variables come back?


My edit to an answer was accepted by two of the three reviewers, with the third rejecting with a claim that part of my edit was incorrect.  In fact, my proposed edit was entirely and demonstrably correct, and the reason given for rejecting is invalid.  How can I let that reviewer know about their error, and have them change their review to "Accept" - changing stats for both of us?  Please note:  This is not the same question as asking for an appeal of an edit that was rejected.  It's asking what I can do about one of the three reviewers, a dissenter who voted against my edit based on their incorrect information.

I'll pose this one as a question for an open discussion because the issue really bothers me:   Shouldn't there be an appeal process for (wrongly) rejected edits?  First I have to give you some background for context: Almost all of my reputation score on SO comes from answering questions related to Bootstrap 4. Also, according to SO, I'm currently in the top 5% of folks who answer questions on that particular topic. In other words, I actually know a few things in regards to this particular topic.   Now, I have recently made an edit to an old question concerning this particular topic, Bootstrap 4 (i.e. my area of expertise). I'll link to that at the bottom because I want to keep the question and discussion general here.   My edit was rejected by 2 individuals who clearly have NO knowledge in regards to Bootstrap 4. But that's not even the most annoying part. The most annoying part are the justifications they have given for their rejection. Those justifications are completely and utterly 100% WRONG!   More context:   I as a guy who is in the top 5% of folks answering Bootstrap 4 related questions initially saw that old questions and didn't know what it actually meant (based on its title). So, I clicked the question because I wanted to find out what the asker actually meant. I then read the actual question. Nothing changed, the question was still unclear at that point. I then looked at the comments. And it was only then where I saw a clarification comment from the asker!   In the first comment to that question, someone asks: What does "multiple items carousel" mean?   That's exactly the question I would have asked because to me (someone who is in the top 5% answering Bootstrap 4 questions and actually KNOWS stuff about this subject) the asker's question was totally unclear. "multiple items carousel" is a term I have never heard before and at best this term/description is very ambiguous. Even to someone like me who is dealing with Bootstrap 4 and Bootstrap 4 related questions every single day.   It is, therefore, highly advisable, helpful and recommended to add the necessary clarification at least to the question's title and possibly also to the text of the question which is exactly what I did.   So, here are the issues I'd like to start a discussion about:   1) People reviewing edits often don't have any expertise on the topic at hand.   2) It seems that if a question has comments attached to it, those comments are NOT shown to the individuals reviewing the edits! WHY? Those comments were essential for a context in this case and would have shown even to someone who is inexperienced with Bootstrap 4 that my edit was in fact, relevant and correct.   3) There is no appeal process for cases of that nature.   So, my question is, once again:   Shouldn't there be an appeal process for (wrongly) rejected edits?  I'd like this to be an open, general discussion about this issue but for those mods who are interested to look up my particular case, it's my edit to .  P.S.  I had promised to mods to never post anything on meta ever again but have now decided to make an exception for this issue because it really bothers me when someone accuses me of wrongdoings when it is objectively NOT the case.


I know infected documents in windows have file extension of .pdf.exe or .jpg.exe . Can you infect a file without changing extension? Is it the same in linux?

I may have the wrong idea here, but I thought that:    MIME types are identifying codes, embedded inside a file. File .extensions are idenifying codes, suffixed to the file's name.   I thought, from something I heard in the dim dark ages, that Linux was .extension agnostic... ( maybe it was in the early days, and things have changed since then...? )  I've recently come from the Windows world, where, at the Operating-System level, a file .extension is the only way (as far as I know) to associate it with its relevant Application program.    Because I don't know why, I find it a bit disconcerting that a file named  "fred" and a file named "fred.txt" both open up in a Text Editor.    Is there a clear-cut hierarchy at work here?


Explain why a correlation between two variables does not necessarily imply that one variable causes the other to vary as it does. Give an example.

I'm looking for specific, real cases in which a causal relationship was inappropriately inferred from evidence of a correlation.   Specifically, I'm interested in examples that meet the following criteria:   Existence of the causal relationship was accepted as fact widely enough to have notable effects (on public policy, discourse, individual decisions, etc.). The link was inferred solely on the basis of correlative evidence (perhaps along with the existence of a coherent but unproven causal mechanism).  Causality has been objectively falsified or at least called into serious doubt.   The two examples that came to mind for me aren't quite ideal:   Sodium intake and blood pressure: As I understand it, it has since been determined that salt intake only increases blood pressure in sodium-sensitive individuals. The existence of a valid causal relationship (although not quite the one that was originally accepted) make this example less compelling. Vaccines and autism: I may have the background wrong, but I believe this link was surmised on the basis of both correlations and (fraudulent) experimental evidence. This example is weakened by the fact that (fake) direct evidence existed.   Note: I've seen this similar question:    My question differs primarily in that it focuses on notable, real-world examples and not on examples in which a causal link is clearly absent (e.g., weight and musical skill).


Duplicate:    I think I have found in my recent experience that I design software differently than most of my peers.  I tend to take the incremental bottom up approach after gathering enough requirements to get a high level idea of the components in the software.    So, in the case of designing an interface that would support multiple concrete classes...I would take a look at what is common to each specific concrete candidate, asking how would I get the job done for each concrete (while thinking about being robust for future concrete).  Then I take that set of commonalities and make an interface, which I believe is a "bottom-up" approach.  In the case of a top down approach I would believe that the designer would look at the client side of the interface and how a client would interact with the interface and then try to implement the concrete classes.    So I can see advantages and disadvantages of top-down / bottom-up.  I just would like to know which is more efficient and provides a better result based off of your previous experiences?   Note: I'm not talking about development methodology (agile, waterfall, etc.), I'm talking about design approaches.

When coding, what in your experience is a better approach?    Break the problem down into small enough pieces and then implement each piece. Break the problem down, but then implement using a top-down approach. Any other?


I wish to convert the whiteHex variable to a decimal using the parseInt() function, and store it in a variable, whiteDecimal.  var whiteHex = 'ffffff';  var whiteDecimal = parseInt(whiteHex);   I am unsure if the above is correct or not. The reason being, that I then wish to subtract 1 from whiteDecimal and store it in a variable offWhiteDecimal. This is where I am getting stuck. How can I subtract one from the ffffff hex value? Am I missing something within the parseInt function?

How do you convert decimal values to their hexadecimal equivalent in JavaScript?


Is it expected that when I test if a null value is not in a list, the result is always false.  That is:    select 'Hello world' where null not in(1,2,3);   Don't select anything, because null not in(1,2,3) is false.   I don't understand this, because the list(1,2,3) don't contain any undefined values(null) so I would expect the null not in(1,2,3) to be true. So why is it false?

This issue came up when I got different records counts for what I thought were identical queries one using a not in where constraint and the other a left join. The table in the not in constraint had one null value (bad data) which caused that query to return a count of 0 records. I sort of understand why but I could use some help fully grasping the concept.  To state it simply, why does query A return a result but B doesn't?  A: select 'true' where 3 in (1, 2, 3, null) B: select 'true' where 3 not in (1, 2, null)   This was on SQL Server 2005. I also found that calling set ansi_nulls off causes B to return a result.