I just installed Ubuntu Budgie 21.04 and i tried to do a sudo apt-get update but it gave me the next error: sudo apt-get update Obj:1 http://ppa.launchpad.net/numix/ppa/ubuntu hirsute InRelease Ign:2 http://ppa.launchpad.net/snwh/ppa/ubuntu hirsute InRelease Obj:3 http://ppa.launchpad.net/ubuntubudgie/backports/ubuntu hirsute InRelease Err:4 http://ppa.launchpad.net/snwh/ppa/ubuntu hirsute Release   404  Not Found [IP: 91.189.95.85 80] Leyendo lista de paquetes... Hecho                 E: El repositorio «http://ppa.launchpad.net/snwh/ppa/ubuntu hirsute Release» no tiene un fichero de Publicación. N: No se puede actualizar de un repositorio como este de forma segura y por tanto está deshabilitado por omisión. N: Vea la página de manual apt-secure(8) para los detalles sobre la creación de repositorios y la configuración de usuarios.  The error in english says: The repository «http://ppa.launchpad.net/snwh/ppa/ubuntu hirsute Release» does not have a realease file I tried lots of tutorials but nothing, other types of software downloads work fine, either from the terminal and software app, i really don't know what is wrong here. These are my installed PPA. apt policy $ ls /etc/apt/sources.list.d Archivos de paquetes:  100 /var/lib/dpkg/status      release a=now  500 http://ppa.launchpad.net/ubuntubudgie/backports/ubuntu hirsute/main i386 Packages      release v=21.04,o=LP-PPA-ubuntubudgie-backports,a=hirsute,n=hirsute,l=backports,c=main,b=i386      origin ppa.launchpad.net  500 http://ppa.launchpad.net/ubuntubudgie/backports/ubuntu hirsute/main amd64 Packages      release v=21.04,o=LP-PPA-ubuntubudgie-backports,a=hirsute,n=hirsute,l=backports,c=main,b=amd64      origin ppa.launchpad.net  500 http://ppa.launchpad.net/numix/ppa/ubuntu hirsute/main i386 Packages      release v=21.04,o=LP-PPA-numix,a=hirsute,n=hirsute,l=PPA for the Numix Project Ltd.,c=main,b=i386      origin ppa.launchpad.net  500 http://ppa.launchpad.net/numix/ppa/ubuntu hirsute/main amd64 Packages      release v=21.04,o=LP-PPA-numix,a=hirsute,n=hirsute,l=PPA for the Numix Project Ltd.,c=main,b=amd64      origin ppa.launchpad.net Paquetes con pin: $: orden no encontrada

When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?


I want to show that if $\{X_n\}$ is a sequence of random variables such that:  (1) $\exists X$ (measurable) such that $X_n \xrightarrow{P} X$  (2) $\exists Y$ with $E(|Y|) < \infty$ such that $|X_n| \le Y \quad \forall n \in \mathbb{N}$  Then $E(X_n) \rightarrow E(X)$ and $E(|X_n - X|) \rightarrow 0$  How do I go about showing this?  This is of course the standard dominated covergence theorem changing almost sure convergence to $X$ to convergence in probability.  The approach to proving the standard theorem involves showing that $X$ is integrable and subsequently bounding $E(|X_n - X|)$, but I don't even understand how to do that part in this new set of assumptions.  Can someone help with this?  Once that part is done then the theorem is complete I believe?  I'm aware this might be a duplicate but I cannot understand these things very well and I'm very confused.  Thanks for any help you can give!

Wikipedia claims, if $\sigma$-finite the Dominated convergence theorem is still true when pointwise convergence is replaced by convergence in measure, does anyone know where to find a proof of this? Many thanks!  Statement of the theorem:  Let $\mu$ be $\sigma$-finite, $|f_n|\leq g$ and $f_n\rightarrow f$ in measure, then we must have  $\int f_n \rightarrow \int f$ and $\int|f_n-f| \rightarrow 0$


I have a folder with these files:  03.jpg 04.jpg 05.jpg 99.jpg   I want to rename these files to  003.jpg 004.jpg 005.jpg 099.jpg   by using a bash script. How can I do this?

I have multiple files whose names look like this  2313_ABCDEAUG2014_PQRST_0_.pdf 3244_ABCDEAUG2014_PQRST_0_.pdf 4234_ABCDEAUG2014_PQRST_0_.pdf   t want to rename the file in the following format.  AZ-2014-08-2313.pdf AZ-2014-08-3244.pdf   Please suggest.


I erroneously drag-n-dropped a folder shortcut in my Finder toolbar.  I tried dragging it off and right clicking, to no avail.  How do I remove it?

I accidentally dropped a file in the Finder toolbar instead of the destination folder (the ZIP icon on the right of the screenshot):   How can I remove it from the toolbar?


I would like to check if there is any occurrence of an uppercase or lowercase string in this:  test strings  1a 2A 3aC   js  const str = '1a' /[a-z]/.test(str) //Pass /[a-z][A-Z]/.test(str) //Fail /[a-z]/.test(str) //Pass

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


I tried to get a random number between 3 and 6 (inclusive):  public class A {                 Random ran = new Random();                              public func1(){               x = 3 + ran.nextInt(7); // need Random number x from 3 to 6      y = 3 + ran.nextInt(7)               } }       but it often gives results 8 and 9! How it can be ?  I used     x=(int) (3 + Math.random()*6);     its give 8 sometimes too... where is an Error???

How do I generate a random int value in a specific range? I have tried the following, but those do not work: Attempt 1: randomNum = minimum + (int)(Math.random() * maximum);  Bug: randomNum can be bigger than maximum. Attempt 2: Random rn = new Random(); int n = maximum - minimum + 1; int i = rn.nextInt() % n; randomNum =  minimum + i;  Bug: randomNum can be smaller than minimum.


Where can i find a COP and input work requierd in a standard modern refrigerator? I need a sample refrigerator, so that I can calculate the heat disposed to the surrounding and use that to design an heat exchanger.

What is the amount of heat rejected by the condenser of a vapour compression refrigeration system, typically those found in households? Something in the nature of a 25W compressor, for example


I am using a simple error handling and I think I have everything else right, how would I make the if statement check to see if the value is equal to this array?  String[] values = { "A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K" };  public String Value {     get     {         return _value;     }      set     {         if (value != values)             throw new Exception("Invalid Card Value");         _value = value;     } }

What would be the best way to look in a string[] to see if it contains a element. This was my first shot at it. But perhaps there is something that I am overlooking. The array size will be no larger than 200 elements.  bool isStringInArray(string[] strArray, string key) {     for (int i = 0; i <= strArray.Length - 1; i++)         if (strArray[i] == key)             return true;     return false; }


from wikipidia:  Does someone have a reference for a proof of this statement about SEM? I couldn't find one in the citation. This equation holds true for any distribution you are sampling from?

Let $X_1, X_2, \ldots X_n$ be random variables with mean $\mu$ and variance $\sigma^2$. We define the sample mean $\bar{X} = \sum_{i = 1}^n X_i$.  I am having trouble understanding why the variance of $\bar{X}$ is $\sigma^2 / n$.  Here is what I worked out thus far:  $$\begin{gather} \sigma_\bar{X}^2 = E((\bar{X} - \mu)^2) = E(\bar{X}^2 - 2\bar{X}\mu + \mu^2) = E(\bar{X}^2) - 2\mu E(\bar{X}) + E(\mu^2) = E(\bar{X}^2) - \mu. \end{gather}$$  However, I'm not sure what to do with the $E(\bar{X}^2)$.


My data is like below:    ClassId ClassName   StudentId   Subject     SubjectId   ----------------------------------------------------- 1         ESL        12         English      20   1         ESL        13         Science      30   1         ESL        12         Social       40   1         ESL        12         Maths        50     Required output: parameters are Subject column values    ClassId ClassName   TotalStudents   SubjectIds    -----------------------------------------------     1        ESL         2               20, 40, 50, 30     When one student takes multiple subjects then count student only once, so in the above data 12 is one student id takes multiple subjects so counted only once. TotalStudents value is 2 (1 from student id 12 and 1 from student id 13)  I wrote this query:    Declare @subjectids string   set @subjectids = '20,30,40,50'    -- will split @subjectids  and store in temp table      select      classname, classid, Count(Distinct StudentId)   from      mytable   where      SubjectsIds in @subjectIds   group by      ClassId, ClassName, SubjectId,     but I get this output:  ClassId ClassName   TotalStudents   SubjectIds   ----------------------------------------------     1        ESL         1               20   1        ESL         1               30   1        ESL         1               40   1        ESL         1               50     Any help in eliminating duplicates? Edited: My basic question is how to count student only once when the same students takes multiple subjects from same class? While counting eliminate duplicates.

How do I get:  id       Name       Value 1          A          4 1          B          8 2          C          9   to  id          Column 1          A:4, B:8 2          C:9


First of all, thank you in advance to anyone who will share their experiences with me. My problem is that I need to somehow get or download the html or php file from a link or URL using Delphi(Well preferably Delphi 6 or 7). for example, i need to get the content of "test01.html" from this link "". It's like I download a file via URL.One more thing is that, if your way was to access the URL first, then you need to know this.for example: link is ""test01.html content:    <script>$(document).ready(function() window.location.replace("http://www.test.com/test02.html");}); </script>test02.html content:    <?php echo "hello world"; ?>from my example above relating to my problem, if your way was to access the URL first, then I should still get the content of test01.html not the source of test02.html.This issue is actually not related directly to idhttp.Get function.Thank You Very Much to AnyOne.

There's a web services I want to call in my application, I can use it with importing the WSDL or by just use "HTTP GET" with the URL and parameters, so I prefer the later because it's simple thing.  I know I can use indy idhttp.get, to do the job, but this is very simple thing and I don't want to add complex indy code to my application.  UPDATE: sorry if I was not clear, I meant by "not to add complex indy code", that I don't want add indy components for just this simple task, and prefer more lighter way for that.


Out of the many things that we did to fix the issue of sticky session one was to make the session attributes implement the serializable interface. Now could someone explain it to me in layman terms what happens when this interface is implemented? what behavioural changes are observed in a class which implements this interface?

We work heavily with serialization and having to specify Serializable tag on every object we use is kind of a burden. Especially when it's a 3rd-party class that we can't really change.  The question is: since Serializable is an empty interface and Java provides robust serialization once you add  implements Serializable - why didn't they make everything serializable and that's it?    What am I missing?


Edit: This question has already been answered  for Windows 7, the answer remains the same, however people looking specifically for how to fix it for windows 10 may never see it so I am leaving this one here as well.    I konw you can disable the peek functionality from the settings, but I was wondering if you could remove it completely. In previous versions of windows if I'm not mistaken, when you disabled peek it would remove that area altogether, and it would be nice to be able hide it in Windows 10 as well. I'm talking about this area right here:

Windows 7 has a new "Show Desktop" button all the way at the edge of the system tray area. Is there any way to get rid of it?  I never use it because I just press Win+D instead, and it's kind of annoying to me.


The question is as follows:  Suppose that X1 and X2 are independent, identically distributed exponential random variables. Determine the PDF for for X1 - X2.  I understand that because X1 and X2 are IID, they have the same parameter and the same distribution. In this case, it is an exponential distribution. I am also under the assumption that I will need to use some variant of the PDF of the regular distribution:    Other than this, I am not certain how to solve this. Thank you.

Suppose we have $v$ and $u$, both are independent and exponentially distributed random variables with parameters $\mu$ and $\lambda$, respectively.   How can we calculate the pdf of $v-u$?


I have this function for a 4x4 keypad:   uint8_t GetKeyPressed()  {   uint8_t r,c;    KEYPAD_PORT|= 0X0F;    for(c=0;c<4;c++)   {      KEYPAD_DDR&=~(0X7F);       KEYPAD_DDR|=(0X40>>c);      for(r=0;r<4;r++)      {         if(!(KEYPAD_PIN & (0X08>>r)))         {            return (r*4+c);         }      }   }  return 0XFF;//Indicate No key pressed }   Is it ok, or it has some bugs in it ?

I have this function to read key press from a 4x3 key-board:  uint8_t GetKeyPressed() {   uint8_t r,c;    KEYPAD_PORT|= 0X0F;    for(c=0;c<3;c++)   {      KEYPAD_DDR&=~(0X7F);       KEYPAD_DDR|=(0X40>>c);      for(r=0;r<4;r++)      {         if(!(KEYPAD_PIN & (0X08>>r)))         {            return (r*3+c);         }      }   }  return 0XFF;//Indicate No key pressed }   Some macro, I missed:      #define KEYPAD A       #define KEYPAD_PORT PORT(KEYPAD)     #define KEYPAD_DDR   DDR(KEYPAD)     #define KEYPAD_PIN   PIN(KEYPAD)   But I don't understand this code, pretty well, because of those bit shifting operations.  Can anyone help me with this code?  Compiler : avr-gcc  Micro-controller : ATmega328


My intuition of trace is that it is essentially asking, for each basis, where does this basis vector go, and what is the new vector's component in its original basis. Then, trace is a sum of those terms.  And matrix non-commutativity makes sense. You apply one transformation, then the next. And this can lead to differences in the result of $AB$ and $BA$.  But if matrices multiplication is non-commutative, then why, in light of my intuition of trace, is trace cyclic. $$\operatorname{trace}(AB)=\operatorname{trace}(BA)$$  I can show it numerically, but I'd like to be able to think of it in a more intuitive and geometric way.

Let $A_1,\ldots,A_n$ be square matrices (not necessarily symmetric). Taking the trace of a matrix product and a cyclic permutation of the product yields: \begin{align*} \text{trace}(A_nA_{n-1}\cdots A_1) = \text{trace}(A_1A_{n}\cdots A_{2}) \end{align*} The above holds for any cyclic permutation (informally, taking an element off the end and appending it onto the other end), but not, in general, for arbitrary permutations of the matrix product.  On the other hand, the determinant of a matrix product satisfies the following property $\text{det}(A_nA_{n-1}\cdots A_1) = \text{det}(A_n)\text{det}(A_{n-1})\cdots \text{det}(A_1)$. Thus, \begin{align*} \text{det}(A_nA_{n-1}\cdots A_1) = \text{det}(A_1A_{2}\cdots A_n) = \text{det}(\text{"any permutation of the product of $A$ matrices"}) \end{align*}  The determinant can be thought of as the volume of its matrix argument whereas one can think of the trace as being the derivative of the determinant (near the identity matrix), that is, the infinitesimal change in volume.  What is the intuition behind the trace property only holding for cyclic permutations where the determinant is the same for any permutation of the matrix product? Can this be explained in a way that is related to the trace being the determinant's derivative?


I have an article under review in a journal which is taking very long review time. I want to submit a short version in a conference citing that detailed version is under review in XYZ journal. I know the other way round is common practice.   I want to know if it is an acceptable practice in computer science area?

This may be a question repeated many times, but I want to know your opinion.   I submitted a journal paper for an algorithm (Computer Science). Fearing that the review process take too long, I decided to submit a short-version conference paper, while the long version is under-review. I received the journal review comments, and re-sent the modifications to the journal. Meanwhile, the conference paper was accepted. But the camera-ready is not sent yet.   The problem is that both papers are about the same idea. There is also some copy-pasted parts in both papers. But:  1) the editor of the journal was not informed about the conference paper (I heard that I should tell the journal about any published papers - but note that the conference paper is not yet published - not even the camera ready is submitted),   2) the organization organizing the conference, is not the same that manage the journal. I have been told that there are conflicting copyrights.   The proposed solutions (that colleagues told me about):   a) submit both as is !   b) submit both (but with change in text).   c) do not submit the conference paper (but I heard this can be harmful)  d) tell the editor now (but honestly, the journal is way more important than the conference).


I recently uninstalled a managed package that had a lot of custom code built on top of it.  Some of the custom work is triggers. These triggers never had complete coverage as far as I know. Furthermore, the test classes for them were contained in a generic test class file that I deleted along with the managed package.  So effectively at the same time, I was able to make these triggers inactive and delete the managed package. I'm now left in a position where the Inactive triggers are still showing in the Production org and counting against code coverage but I cannot see them anywhere other than in the Dev Console code coverage list results. They are also written around now non-existent sObjects so I'm not even sure I could write and deploy a test class to cover them.  I need to delete these triggers out but I have no way of accessing them. If I download a full copy of the Prod org in an IDE these triggers are not included.  Has anyone had an experience like this where a trigger is included in code coverage but cannot be accessed in the web browser or through an IDE?

We currently have around 20 apex classes and 5 triggers which are not used in our production org. We want to delete them in our production instance. We dont have ant scripts ready yet to be used for our deployments and so we cannot use destructivechanges file. Currently our production deployments are done by our support team and they need documentation from us to do these deletes. Changesets do not allow to delete apex classes and triggers. So what is the best way to delete these apex classes and triggers from production?


I have a little GTK application I've created which is basically a simple Switch. I would like to see if anyone knows if it is possible to add to the menubar in ubuntu. Almost like the power button in the corner. I'd just like to be able to have it sit there and toggle it from time to time to have it run custom code (which turns on my air conditioner via curl/wifi smart plug) similar to a widget I suppose. So rather than having a separate application it just sits there neatly up the top. Any ideas on how to do this if it is possible which I will assume it is but I don't know how ;-)  Executive summary; take a standard GTK switch button and attempt to embed it into the unity menu bar, is it possible?  Thanks Jack

I'm interested in Unity indicators and wonder if there is any tutorial on how to program them. I can use the sources of the existing ones as last resort, but I'd prefer a more friendly approach because my programming skills are quite limited.


I'm currently operating on a late 2013 MacBook Pro and am eager to buying a wireless keyboard for my setup. I was looking at the Logitech MK345, which is a bluetooth mouse-keyboard combo, and thought it was quite what I needed. Although, it didn't really say anywhere that it worked with Mac. I tried looking for answers to see if non-mac keyboards function properly with OS X and only saw answers for wired ones.   I'm pretty confused... Should I take the risk of buying the keyboard? Any suggestions to what I should do? Thanks.

Recently I've been thinking about the idea of migrating from PC to Mac, specifically Mac Mini. The biggest issue however is hardware, since I'm not sure what will and what won't work on OS X.  First issue that comes to my mind is keyboard, currently I'm using Logitech G15. If I connect it to a Mac, how well will this work with OS X specific keys like Option, Cmd, etc? Does it work out of the box with all keyboards, or should I rather buy the Apple keyboard?


Here's my MWE:   \documentclass{article} \usepackage{fontspec} \usepackage{bookman} \usepackage[T1]{fontenc} % Thought this was unnecessary with XeLaTeX \begin{document} Vǫlundarkviða \end{document}   And here is the result:     As you can see, the second letter is missing. Also, I feel like fontenc should not be there. How do I do this properly?

I am unable to figure out simple solution to add "Bookman Old Style"  as a main font in my latex document. I have used below line but does not give me required font.  \usepackage{bookman}   Could not find any Simple correct answer for this. Pl. suggest how to do it.  I am using windows, pdflatex.  thank you


It is no hard to prove that the real sequence $\{a_n\}_{n=1}^\infty$ decided by $$ \begin{cases} a_1 = 1\\ a_{n+1} = \sin a_n \end{cases} $$ converges to $0$ as $n\to\infty$. However, it seems that such a convergence is extremely slow (at least not exponentially), since $a_{n+1}-a_{n} = o(a_n^3)$. However, I still want to know just how slow it is. To be more precise, $$ \text{is }a_n \text{ of order }  \frac{1}{n}, \frac{1}{n^2}, \text{or}\ \frac{1}{\ln n}, \text{or something else?} $$ And how should we analyze a problem like this?

Consider the sequence defined as  $x_1 = 1$  $x_{n+1} = \sin x_n$  I think I was able to show that the sequence $\sqrt{n} x_{n}$ converges to $\sqrt{3}$ by a tedious elementary method which I wasn't too happy about.  (I think I did this by showing that $\sqrt{\frac{3}{n+1}} < x_{n} < \sqrt{\frac{3}{n}}$, don't remember exactly)  This looks like it should be a standard problem.   Does anyone know a simple (and preferably elementary) proof for the fact that the sequence $\sqrt{n}x_{n}$ converges to $\sqrt{3}$?


i have the following partitions  dev/sda1 - 500 mb unallocated - 181 gb  /dev/sda4 - extended 23 gb  /dev/sda5 - ext4 - / 15 gb /dev/sda6 - linux-swap 7.6 gb  /dev/sda4 - ntfs - 261 gb  unallocated - 2.02 mb   I want to merge use 50 gb from the 181 gb and merge it with /dev/sda5 as my root parition is only 15 gb   Please advise how to achieve this

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


I have a major problem with my system's cron; it runs every 3 minustes causing a slow responding from the site. When I checked the logs, I found this error:     Attempting to re-run cron while it is already running.     I found some good answers on  but when I searched for the cron_semaphore variable in variable's table I didn't find it. Even after I disabled the Search module, and uninstalled it, nothing happened: The cron tasks are still not working.  I checked, and I noticed that the cron tasks have been executed 1 day and 7 hours ago, although I configured it to run every 12 hours.     I am using Drupal 7.19.

What are the steps to troubleshoot and resolve this issue as per title?    When I try to run manually, I get a  page immediately, and the error message "Attempting to re-run cron while it is already running."


The characters played by humans (eg.  Luke,  leia,  solo etc)  in star wars are Homo sapiens or any other species?  If they are homo sapiens then how could they exist in a galaxy far far away?  Did we reach there?  Or not homo sapiens then which species are they belonging to?

Kind of brought to my attention by .  The poster mentions non-humans, which implies that there are humans in the Star Wars universe.  However, since it happened "A long time ago, in a galaxy far far away", how could there be any humans in the Star Wars universe?  Are there "humans" in Star Wars there just because it was easier to make the movies that way?  Other shows such as Star Trek are about the future of humans, so it's easy to understand the existence of humans in those storylines.  However for Star Wars it just doesn't make sense.  It also seems odd that they'd go around creating all these different species and then just leave the main characters as humans. I guess another possibility is that the humans in star Wars eventually populated Earth, but then what happened to all the technology?


Let $T:V\to W$ be a linear transformation, then $\text{Ann}(\text{Im}T)=\text{ker}T^*$.  How one could start to prove it?  Many thanks.

This is an old exam problem: Let $V$ and $W$ be finite dimensional vector spaces over a field $F$ and let $T: V \to W$ be a linear transformation. Define $\hat{T}: W^* \to V^*$ by $(\hat{T}(f))(v)=f(T(v))$. Here, $U^*$ denotes the dual vector space $U$. Since $\hat{T}$ is a linear transformation prove $\ker \hat{T} = \text{ann}(\text{range } T)$ where $\text{ann}(Y) = \{g \in U^* : g(y)=0 \text{ for all } y \in Y \}$ for a subspace $Y$ of vector space $U$.  I'm really not sure how to start this problem. Any advice would be great!


I have a +7/-0 answer, written based on a reasonably careful reading of a particular authoritative text (not the question itself, which was straightforward). Unfortunately, I wasn't careful enough, and another answer on that question, by looking more completely, has the right of it. (The result is that mine is not merely incomplete, but actually wrong; fortunately, the second answer is currently at +9/-0.)  Should I delete my answer? Edit to say "no, go check the other one"? Leave it for votes to handle? Comment on it? Or what?  There's a lot of questions on metas about deleting downvoted or otherwise community-recognized wrong answers, as well as those that misread the question, but this seems to be a little different, as neither is the case.

I just deleted an answer I had left to a question because it had been proven to be wrong.  It seems that this would be the proper thing to do, since the purpose of the site is to provide correct answers - misleading information is the last thing we all want.  But what if the answer is providing important information about approaches that have been tried and rejected?  What if it's an obvious but wrong choice, and others are likely to leave the same answer if they don't see yours?  What if there are later responses that refer to yours, and you're removing the context?  As a compromise I waited a day before removing my post.  How would you have done it?


My bike wheel was recently stolen and I found this old Bontrager AT-550 wheel in my shed. It's a 29er from my research and I'm wondering what size tyre would fit that would be decently smaller than the current tyre. My bike is a hybrid with a 700cx42c back tyre and the front tyre is 29x2.2 and it would look ridiculous to have a big tyre in the front and small one in the back. I'm sorry for mixing the units the measurement but I'm new to this and would appreciate some help. Thanks!

I have a hybrid bike with Alex DP17 32h rims (700c).  They still have the tyres that came with the bike on them, 40c konda's, but I'd like to replace them with some puncture resistant, narrower tyres with a slick centre strip since most of my commute is on road/tarmac path.  I can't find the rims on the Alexrims site, so how do I find out what tyres it is possible to fit?


I wrote something in LyX and then converted that into a tex file. But when I convert the tex file into a pdf, a huge gap is produced between the last sentence of a paragraph and the next section title like here:     In addition, a large gap is created between one image and another paragraph like the following:     I am pasting here the preamble set by LyX by default:  \documentclass[12pt,twoside,english,refpage,intoc,bibliography=totoc,index=totoc,BCOR7.5mm,captions=tableheading]{article} \usepackage{lmodern} \renewcommand{\sfdefault}{lmss} \renewcommand{\ttdefault}{lmtt} \usepackage[T1]{fontenc} \usepackage[latin9]{inputenc}   \usepackage{geometry}   \geometry{verbose,tmargin=1in,bmargin=1.25in,lmargin=1in,rmargin=1in,headheight=1in,headsep=1in,footskip=1in} \setcounter{secnumdepth}{2} \setcounter{tocdepth}{2} \setlength{\parskip}{\medskipamount} \setlength{\parindent}{0pt} \usepackage{color} \usepackage{babel} \usepackage{array} \usepackage{booktabs} \usepackage{float} \usepackage{amsmath} \usepackage{graphicx} \usepackage{setspace} \usepackage[authoryear]{natbib} \usepackage[unicode=true,bookmarks=true,bookmarksnumbered=true,bookmarksopen=false, breaklinks=false,pdfborder={0 0 1},backref=false,colorlinks=true] {hyperref} \hypersetup{pdftitle={The LyX User's Guide},  pdfauthor={LyX Team},  pdfsubject={LyX},  pdfkeywords={LyX},   linkcolor= black, citecolor=black, urlcolor=blue, filecolor=blue, pdfpagelayout=OneColumn, pdfnewwindow=true, pdfstartview=XYZ, plainpages=false} \makeatletter %%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Textclass specific LaTeX commands. \newlength{\lyxlabelwidth}      % auxiliary length    Any suggestions on how to reduce those gaps shown above? Thanks in advance.

I'm writing my bachelor-thesis and have a couple of small sub-sub-sections explaining conversions, like in the following  \subsubsection*{Assignment}  This document only explains non-compound assignments. The other kind, i.e \texttt{a += b}, is supported by the language too, but is not yet implemented.   \begin{itemize} \item If the first is an \texttt{auto} variable, no conversion takes place when assigning       the right hand side to the variable designated by the left hand side.  \item Otherwise, an assignment conversion takes place converting the given value to the type       of the designated variable.  \item Assignment requires an lvalue as the left hand side, and yields an lvalue result.  \end{itemize}  \subsubsection*{Multiplication} % ...   But latex renders it quite ugly with much space in between the items. I think it does so to fit the whole page. How can I tell it not to do so? Is what I'm doing right at all?


Hi Guys I'am a Network Engineer that was using linux in 5 years  before I use Ubuntu 18.04 and now I'm trying to upgrade to Ubuntu 20.04 and then trying to install Cisco PacketTracert 7.3 for our lab and failed.  this is the error please help me cause this apss it's very important for me  ai@ai:~/Documents/networking/packettracert$ sudo dpkg -i PacketTracer_730_amd64.deb   Selecting previously unselected package packettracer.  (Reading database ... 198839 files and directories currently installed.) Preparing to unpack PacketTracer_730_amd64.deb ... Unpacking packettracer (7.3.0) ... dpkg: dependency problems prevent configuration of packettracer:  packettracer depends on qt-at-spi; however:   Package qt-at-spi is not installed.  dpkg: error processing package packettracer (--install):  dependency problems - leaving unconfigured Processing triggers for gnome-menus (3.36.0-1ubuntu1) ... Processing triggers for desktop-file-utils (0.24-1ubuntu2) ... Processing triggers for mime-support (3.64ubuntu1) ... Processing triggers for shared-mime-info (1.15-1) ... Errors were encountered while processing:  packettracer

I am trying to install Packet Tracer 7.3 (latest version) on Ubuntu 20.04 but do not succeed to so so because of two dependencies which are not installable ("libdouble-conversion1" and "qt-at-spi").  However I successfully installed the previous version (7.2.2) which was available in an Ubuntu installer format (.run file) but I nothing happens when I run it from my gnome desktop.  I am quite a newbie in Linux so I appologies if answers are obvious...  Thanks in advance ;-)  Denis


Most of the work involved in producing a journal is done by people paid at  than most academics, but the those with the rarest skills, those able to review specific scientific articles, provide their labor for free.  In my fairly limited experience most academics are over worked, under paid and not particularly positive about the closed access journal system or shareholding capitalists.  Most reviews are conducted anonymously, so reviewers do not receive direct credit from the scientific community.  Funders (in my limited experience of the MRC at least) care about papers a group author not those they review.  The big journals at least are profitable companies that  to their shareholders, and I presume that if they were unable to get this work done for free they would pay for it, making the academics better off and the shareholders receive less dividends.  Why do so many academics provide this service for free?    I saw  question, but it does not seem address the economic imbalance or the supposition that if no one did it for free then everyone would get paid.

One of the most criticized aspects of the current publishing scheme, is that academics do pretty much all the work for free and publishers get the money.  Why don't people just charge a fee when contacted by a publisher to referee an article?    I know , that's not the question. The issue is why do it requesting no monetary compensation when the publisher is getting (for doing next to nothing) an .


Let $G = GL_2 (\mathbb {R} $).   Show that $T$ = {$     \begin{bmatrix}         a       & b \\     0       & d  \\      \end{bmatrix}$ | ad $\neq 0$ } is a subgroup of $G$  My attempt:  det$(TT^{-1})$ = det$(T)$ det($T^{-1})$ = det($T$)  $1$/det($T$) = $ad$ $(1/ad)$= $1$. We are done by subgroup test

Consider the set $V$ of upper-triangular $n\times n$ matrices with elements in some ﬁeld $K$. I.e., if $A$ is such a matrix, $a_{ij} = 0$, for $i > j$  Show that non-degenerate upper-triangular matrices form a group with respect to matrix multiplication.


I'm brand new to Linux/Ubuntu, and I have multiple flash drives  with the latest release on it. Last night, I mistakenly installed the 32-bit OS while I intended to install the 64 bit. Just before doing so, I took an image of Windows 7 64 in case something went wrong.   I want to upgrade to 64 bit version of Ubuntu while keeping W7 64. Is there a way for me to easily do this? If I use my 64 bit live disk, will the 64 bit version overwrite the 32 bit?  Alternatively, could I just recover the PC from the image I took before installing Ubuntu, wiping everything clean INCLUDING 32-bit Ubuntu (then install 64)? Or will the W7 recovery ignore Ubuntu all together?   Thanks All!

I've got a 32-bit Ubuntu installation running on 64-bit hardware. Now that , I would like to switch to 64-bit without having to reinstall the OS.  This is one of the :  Shawn installed his system using the 32-bit version of Ubuntu, but his hardware is 64-bit and he wants to switch over. He manually installs the amd64 versions of dpkg and apt, replacing the i386 versions and changing which architecture is used as the default; then he installs the amd64 ubuntu-minimal package; then he installs the amd64 ubuntu-desktop package. Over time the remaining i386 packages are replaced automatically on upgrade.  However, when trying to follow the instructions in there, I cannot find any 64-bit version of dpkg or apt.  Did this user story got implemented in a different way in the final spec, or do I need to do something differently?  In short, how can I switch my 32-bit installation to 64-bit?


Im currently fighting a nasty SSD bug , a user advised me to grab hold of the /var/log/syslog file to look out for any culprit files. Now I actually succeeded in retriving the file. I noticed nothing extraordinary, but a red line of zeros in one of the lines. Does this have any special meaning?


After creating an object the little menu in the bottom left corner pops up. But when I try to use it by clicking (and dragging) on it, it just disapears.  I already tried to reset blender and reinstalling it. And I am using Blender v2.82a.

When you add a new mesh, the overlay appears in the bottom left of the screen allowing you to change certain properties. Recently, however, when I try to click on any setting, the box disappears. I've tried clicking, dragging and any combination of both, but the overlay doesn't respond and vanishes as soon as you release the mouse button.    Obviously you only get one chance to change these properties - so I'm stuck without it.  Could an add-on be causing the problem?


I am making a validation for my invoiceId which basically allows all letters and numbers and the dash character (-), and it doesn't allow the word draft in any part of the string, for example:  Valid cases:   123456  InvoiceId-1234 -1234-Invoice-Id   Invalid cases:   draft-234 invoicedraft123 12345draft -draft   This is the regex I am using to validate alphanumeric characters and special characters:  [a-zA-Z0-9-]+  I have tried the negative look ahead for here are my attempts:  /^\b(?:(?!(D|d)(R|r)(A|a)(F|f)(T|t))[a-zA-Z0-9-]+$/;  This one just stops the word draft at the beginning  and /^((?!draft).)*([a-zA-Z0-9-])$;  This one allows special characters.  Is it posible to have create a regex with my requirements?

I know it's possible to match a word and then reverse the matches using other tools (e.g. grep -v). However, is it possible to match lines that do not contain a specific word, e.g. hede, using a regular expression?   Input:  hoho hihi haha hede   Code:  grep "<Regex for 'doesn't contain hede'>" input   Desired output:  hoho hihi haha


Im trying to add more feature in zabuto calendar. That is a modal will appear after click on date, allow we to add or remove event for this day. But i can't catch event click on the button in this modal. Here is my code.  function createModal() { // create a modal //...  var $modalFooterButtonSave = $('<button id="btnSave">Save</button>');  var $modalFooterButtonDelete = $('<button id="btnDelete">Delete</button>'); //... //return this modal }  function myDateFunction() { //Add modal into html page $("#myModal").html(createModal()); //Show modal $('#adjustModal').modal('show'); return true; } $(document).ready(function () {     // zabuto event click on date     $("#my-calendar").zabuto_calendar({         action: function () {             return myDateFunction();         }     });     //Here is problem, i can't catch the event click on this button.     $("#btnSave").click(function(){         alert("The btn Save was clicked.");     }); }

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


Because I hate viruses, I just want to get answer for small question about VIRUSES in Ubuntu.  Let assume my UBS have some viruses (from windows operating system), so should I used an antivirus to remove them before opening the USB or all windows viruses not work on ubuntu operating systems ?  I read some articles that wrote "say goodbye for viruses on ubuntu" but I'm still worried from USB viruses or downloaded RAR, Zip, EXE files.

I thought that there was no need to scan for viruses either in Ubuntu or any Linux distros until I found virus scanner packages clamtk and klamav in Ubuntu software center yesterday.  This leads to the following questions:   How do viruses differ between Linux and Windows? How do the strategies for protection differ between Linux and Windows? Should a virus scanner package be installed on my system? If so, which would be a better option?


Is there L'Hospital's rule for analytic functions of complex variable?  If yes where can I find it, in what books, and how to prove it?

I have a question about something I'm wondering about. I've read somewhere that L'Hopitals rule can also be applied to complex functions, when they are analytic. So if have for instance:  $$ \lim_{z \rightarrow 0} \frac{\log(1+z)}{z} \stackrel{?}{=} \lim_{z \rightarrow 0} \frac{1}{(1+z)} = 1 $$  Now i'm wondering if this is correct? Also if we take $|z|<1$, is it then correct?  Thanks,


I need to write a script for an illustration program which will take an image, allow the user to outline the rectangular face within the image, and then warp the image so that the rectangular face is actually rectangular to the viewing plane. See the image below.  I do not need to do the actual mapping, the program will do that for me if I give it a new rectangle to 'fit' the image to. Given the set of image corner coordinates (A, B, C and D) and a set of coordinates within the image (E, F, G and H), how do I determine the coordinates of the final transformed image (I, J, K and L)? As far as which rectangle to map E-H to in order to get I-L, let's call those M, N, O, and P. They will be known. I am only looking for help with the mathematics of the transformations. I can handle the programming part once I understand the maths.

I'm working on a project using Chrome - JS and Webkit 3D CSS3 transform matrix. The final goal is to create a tool for artistic projects using projectors and animation - somewhat far away from using maths... I'm using a projector to project several squares over several shapes - as seen in the picture. What I would like to do is for the user to draw 4 points on the screen (2D x and y) and from there extract a matrix object that I could apply to a regular DIV element of a dimension of 100px by 100px. By finding scaleX, scaleY, rotation, rotationX, rotationZ and probably some perspective that I could apply to the div to relatively match the surface. I'm not really familiar with geometry beyond sin and cos, and 3D in general and don't even know if that is something doable. If anyone could help me get started or point me in the right direction, I would greatly appreciate. Here is an animated gif (click to enlarge), hoping it makes it more clear to understand.


Doodling in wolfram, I found that $$ \sum^{k}_{n=1}1=k $$ The formula is pretty obvious, but then you get $$ \sum^{k}_{n=1}n=\frac{k(k+1)}{2} $$ That is a very well known formula, but then it gets interesting when you calculate $$ \sum^{k}_{n=1}n(n+1)=\frac{k(k+1)(k+2)}{3}\\ \sum^{k}_{n=1}n(n+1)(n+2)=\frac{k(k+1)(k+2)(k+3)}{4} $$ And so on. There is an obvious pattern that I really doubt is a coincidence, but I have no idea how to prove it in the general case. Any ideas?

Considering the following formulae:  (i) $1+2+3+..+n = n(n+1)/2$  (ii) $1\cdot2+2\cdot3+3\cdot4+...+n(n+1) = n(n+1)(n+2)/3$  (iii) $1\cdot2\cdot3+2\cdot3\cdot4+...+n(n+1)(n+2) = n(n+1)(n+2)(n+3)/4$  Find and prove a 'closed formula' for the sum  $1\cdot2\cdot3\cdot...\cdot k + 2\cdot3\cdot4\cdot...\cdot(k+1) + ... + n(n+1)(n+2)\cdot...\cdot (k+n-1)$  generalizing the formulae above.  I have attempted to 'put' the first 3 formulae together but I am getting nowhere and wondered where to even start to finding a closed formula.


we all know that magnetic field doesn't work....if a current carrying element pulls a metal piece then work is done by the source or the battery not the field.....now let us assume that a bar magnet pulls another magnet / metal above ground and does a work Mgh....now do does this work?  here the source of the field is rotating electrons and we can't blame them to b doing the work ...since electrons rotates in fixed orbit with fixed energies......i dont understand what am i missing?

I learned that the force from a magnetic field does no work. However I was wondering how magnets can be used to pick up pieces of metal like small paperclips and stuff. I also was wondering how magnets can stick to pieces of metal like a refrigerator?


Sometimes you don't search for the answer to a question before you ask it. It will be closed as duplicate. Should you, the question owner, delete it? While it is good for search engines finding the answer and whatnot, it does take up space on the front page, pushing better questions down. What should be done in this situation?

(currently deleted (visible only to 10kers)) is a great example of a duplicate question that should not be deleted. [Note: this question was later merged into , which resulted in the original being hard-deleted. This issue with merging  ] The titles of the duplicates are completely different.  Having duplicates around greatly aids search hits on the site. We need to keep questions like this around for the benefit of the community. Both questions have around 4K views.  They are both relevant.  I cannot believe that a question with over 3K views is being deleted. Edit Search for python continue line and python line break in google.  Both answers are top hits.  They should both be open.


I've noticed that "What's the best..." questions are both popular and against the rules on Stack Exchange sites.  I've also noticed that getting the pulse of the brilliant tech community that uses these sites is extremely valuable. If I want to find a good blog platform, JavaScript MVC framework, or shared text editor, the SO users typically know the newest, technically soundest, most popular and functional ones.  Is there room on Stack Overflow to enable this kind of subjective question? Maybe it could be a new Stack Exchange site, like "bestInClass.stackexchange.com" or different category of question, meant to be opinion based.  I see one similar question, but I'm open to any implementation of the "Best In Class" pattern. Maybe if you ask that category of question the reputation is calculated differently, or in a separate container. Maybe SO rep counts towards some weight on your opinion of what is the best in class.  I think there's a solvable and lucrative problem here:   You have a user base with valuable knowledge (What's the best XYZ?) They are willing to share that knowledge It doesn't fit within the SO model   If #3 could be solved, "What's the Best X" could be a great addition.  Similar:

Stuff like polls, recommendations based on subjective constraints, puzzles, webcomics etc. do not belong on the serious main SE sites, where professionals should be considered at work and having just a few spare minutes ("code's compiling") to answer questions, so they should not be distracted by such things. However, I'd also like to have a home for these things still using the SE engine. For the reason I mentioned before, this needs to be a separate place though. Let's call it four.[sitename-here].com.


I would like to give a suggestion. It is great that you can ask other developers to revise your code, correct it and give you suggestions. But sometimes, you need help with configuring the best technology or a practice you could use, before starting coding. Such questions are not allowed on Stack Overflow. Why is that and can that be changed? Making a category of questions, which do not contain code but asking for suggestion for example.


I am referring to the context where you miss or don't miss  something by a very short time, like when you miss or succeed in taking a train or a flight by just a few minutes or even a few seconds. What are the common expressions  or sayings that can be used in such cases?

In French, if I want to quantify a very small amount of time (but not fixed: it can be 5 ms or 0.1 ms) I can use a pouième. Is there an equivalent in English?  I'm not looking for an expression but for a standalone word.  EDIT : In fact, I need to create a  which will measure time and be equal to a 1/600s. In French, pouième is a cute word which can means a . The issue is that I must write english code and that's why I would like to find a standalone equivalent.


While I can in part understand why bank statements are asked for when making a visa application, the value of them for a multiple-entry visa is somewhat lost on me, because their validity is meaningless after the first visit.  That being the case why bother to offer multiple-entry visas, when the authorities have NO way of knowing whether the visitor can afford future visits? This surely destroys the argument for their inclusion in the first place.

The UK Visas and Immigration Directorate publishes  that provides helpful tips that can result in successful visa applications. Section 2 of this guidance opens is entitled "other documents you may want to provide" (emphasis mine).  Section 2: other documents you may want to provide – all visitors This section provides guidance on the types of documents that you may want to provide to help us consider your application against the Immigration Rules. Previous travel documents/passports, which show previous travel. Financial documents showing that you have sufficient funds available.  These must clearly show that you have access to the funds, such as:  bank statements building society book proof of earnings such as a letter from employer confirming employment details (start date of employment, salary, role, company contact details) where a third party (who is either in the UK or will be legally in the UK at the time of your visit) is providing financial support to you e.g. a business, a friend or a relative, documents to show that they have sufficient resources to support you in addition to themselves and any dependant family should be provided   The first item is "bank statements" and this ties in with the , which says...  evidence that you can support yourself during your trip, eg bank statements or payslips from the last 6 months  (Note 'eg' is a Latin abbreviation meaning "for example"; this appears to be optional rather than a fixed requirement.) Question: How should someone interpret this such that the chances of success are maximized? How many statements should I submit? What are they looking for and what do my bank statements tell about me?


How to draw a Pascal's triangle, similar to what follows?

I would like to typeset the top part of Pascal's triangle. To get the triangle with the names of the binomial coefficients, i.e., {n \choose k}, I used the following code  \begin{tikzpicture} \foreach \n in {0,...,4} {   \foreach \k in {0,...,\n} {     \node at (\k-\n/2,-\n) {${\n \choose \k}$};   } } \end{tikzpicture}   The result is this   Now I want to be equally lazy and do something like this for the values of the binomial coefficients, i.e., replace {\n \choose \k} in the node label with \CalculateBinomialCoefficient{\n}{\k} where \CalculateBinomialCoefficient is a hypothetical macro that calculates the binomial coefficient. Has anyone done something like that?  The result should look like this:


I am using Ubuntu 16.04 and now I need to install Windows 7 along with it.  I only have one sda1 partition on my HDD and it occupies the whole space, so how can I dual boot my system?

I have Ubuntu on my laptop. Now I want install Windows 7 in a dual-boot. How can I do this? I can't lose my Ubuntu files, and I'm afraid that I might break . Go  for UEFI only!


I already have Schengen Visa, however, we added another country which differs from when I applied for visa. Will I have a problem when I enter?  I will be spending more time in the country that issued the visa and I will be both arriving and leaving through the same country that issued the visa.   I actually received it for 15 days since my trip was tourism... is that normal?

Original itinerary Fr 13nights  would it be okay to change itinerary to:  Change to FR 6nights-> IT 7nights -> FR 1night  Already hold Schengen visa valid for 15 days.  Will I be in breach?


I can't find any information on constructs or undead having a disease immunity. The Contagion spell gives diseases. Could someone, RAW, cast Contagion on a stone golem, for example, and give it fleshrot, despite it not having any flesh to rot?

After the , the spell  now inflicts the  condition upon a successful melee spell attack. The relevant spell text is below, with updated portions highlighted in bold:  Your touch inflicts disease. Make a melee spell attack against a creature within your reach. On a hit, the target is poisoned. At the end of each of the poisoned target's turns, the target must make a Constitution saving throw. If the target succeeds on three of these saves, it is no longer poisoned, and the spell ends. If the target fails three of these saves, the target is no longer poisoned, but choose one of the diseases below. The target is subjected to the chosen disease for the spell's duration. Since this spell induces a natural disease in its target, any effect that removes a disease or otherwise ameliorates a disease's effects apply to it.  The wording of the spell leads me to conclude that this spell still inflicts a disease, which has the immediate effect of poisoning the target. Therefore, even if a target has poison immunity, they will still make Constitution saves as designated to see if the disease takes effect. However, the line, "At the end of each of the poisoned target's turns..." also leads me to think that an enemy with poison-immunity cannot be the Poisoned target, therefore disallowing the remaining sequence of events. Are targets with immunity to the Poisoned condition therefore immune to contagion?


Is there support for including an author's title in citations, i.e. their military rank or other title?  Examples include:  (Blackadder 1917) in-text and Blackadder, Captain E. (1917) in the bibliography. (Blackadder 1648) in -text and Blackadder, Sir E. (1648) in the bibliography.  The problem I currently have is that completing the Author field in Bibtex as Sir Edmund Blackadder results in:  Blackadder, S. E. (1648) in the biblio.  I'm using BibDesk 1.6.2  Edit: Request for MWE.  Not sure how to, as it's Bibtex, but just insert this into the Author field:  {Sir} Edmund Blackadder   Or any positioning of the braces. BibDesk gives previews that are replicated in my real file.

My bibtex style outputs      Newton, S. I. Opticks, or a treatise of the reflections, refractions,   inflections and colours of light [Text] / Sir Isaac Newton. [S. l.],   1730. 382 p. Google Books : XXu4AkRVBBoC.   for the following BibTeX entry  @BOOK{IsaacNewton, author = {Newton, Sir Isaac}, title = {Opticks, or a treatise of the reflections, refractions, inflections and colours of light}, publisher = {William Innys}, url = {http://books.google.com/books?id=XXu4AkRVBBoC}, year = {1730}, numpages = {382}, eprint = {XXu4AkRVBBoC}, eprinttype = {Google Books}, }   How should I change the field   author = {Newton, Sir Isaac},   obtain something reasonable rather than Newton, S. I.? Note that second occurrence of Newton's name (Sir Isaac Newton) is correct.  Incidentally, what would be the correct address: "Sir Isaac" or "Sir Newton"?


I'm trying to solve this problem:     Find  a differentiable function $f:\mathbb{R} \longrightarrow \mathbb{R}$ such that $f':\mathbb{R} \longrightarrow \mathbb{R}$ is not continuous at any point of $\mathbb{R}$.    Any hints would be appreciated.

There is a well-known result in elementary analysis due to Darboux which says if $f$ is a differentiable function then $f'$ satisfies the intermediate value property.  To my knowledge, not many "highly" discontinuous Darboux functions are known--the only one I am aware of being the Conway base 13 function--and few (none?) of these are derivatives of differentiable functions.  In fact they generally cannot be since an application of Baire's theorem gives that the set of continuity points of the derivative is dense $G_\delta$.  Is it known how sharp that last result is?  Are there known Darboux functions which are derivatives and are discontinuous on "large" sets in some appropriate sense?


In Goodfellow's Deep learning text, it is written    Is this way of defining a probability $p(y=1| x;\theta)$ even legal?  Recall the definition of a probability given a random variable     where $p_X$ is the probability mass function.  Is the logistic function $\sigma$ considered to be a probability mass function?   If so, what plausible process is responsible for generating this probability mass function? (i.e., a process similar to how geometric or Bernoulli pmf are defined)

I am trying to learn the logistic regression model. I came to know that there is no linear relationship between predictor variables and response variables since response variables are binary (dichotomous). The link function used for logistic regression is  logit which is given by $$  \log \frac {p}{1 - p} = \beta X  $$ This tells that the log odds is a linear function of input features. Can anyone give me the mathematical interpretation of how the above relation becomes linear i.e. how logistic regression assumes that the log odds are linear function of input features? Since I am poor at statistics, I can't understand complex mathematical answer.


I am currently in the process of learning how AES actually works and that works great as of now but when it comes to the Rijndael's key schedule I have a question. From what I have read, I have to make a expanded key that is 240 bytes in size to supply enough subkeys to the whole process of a AES encryption using a 256 bit key. Does this mean that I need to make the expanded key exactly 240 bytes or can I make it 256 bytes and discard the last 16 bytes? I ask this because from what I understand, each round of the key expansion gives me 32 bytes of round keys. In that case I have to do 8 rounds of key expansion to supply the encryption with enough subkeys since 7 rounds will only give me 224 bytes.

It said  that:     [....] Rijndael can be specified with block and key sizes in any multiple of 32 bits, with a minimum of 128 bits. The blocksize has a maximum of 256 bits, but the keysize has no theoretical maximum.   How would the key schedule look for these other key sizes, like a 136-bit key?


I host three different websites on the same server. Here's excerpts from this morning's Apache logs:  ### SITE 1 ### [Fri Dec 13 09:15:49 2013] [error] [client 85.17.87.36] script not found or unable to stat: /var/www/vhosts/site1.com/cgi-bin/php.cgi [Fri Dec 13 09:15:49 2013] [error] [client 85.17.87.36] script not found or unable to stat: /var/www/vhosts/site1.com/cgi-bin/php4 [Fri Dec 13 09:23:21 2013] [error] [client 113.53.238.155] script not found or unable to stat: /var/www/vhosts/site1.com/cgi-bin/php [Fri Dec 13 09:23:22 2013] [error] [client 113.53.238.155] script not found or unable to stat: /var/www/vhosts/site1.com/cgi-bin/php5 [Fri Dec 13 09:23:22 2013] [error] [client 113.53.238.155] script not found or unable to stat: /var/www/vhosts/site1.com/cgi-bin/php-cgi [Fri Dec 13 09:23:23 2013] [error] [client 113.53.238.155] script not found or unable to stat: /var/www/vhosts/site1.com/cgi-bin/php.cgi [Fri Dec 13 09:23:24 2013] [error] [client 113.53.238.155] script not found or unable to stat: /var/www/vhosts/site1.com/cgi-bin/php4 [Fri Dec 13 09:47:03 2013] [error] [client 172.246.127.26] File does not exist: /var/www/vhosts/site1.com/httpdocs/install [Fri Dec 13 09:47:08 2013] [error] [client 172.246.127.26] File does not exist: /var/www/vhosts/site1.com/httpdocs/phpbb3  ### SITE 2 ### [Fri Dec 13 09:24:39 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site2.com/cgi-bin/php [Fri Dec 13 09:24:39 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site2.com/cgi-bin/php5 [Fri Dec 13 09:24:39 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site2.com/cgi-bin/php-cgi [Fri Dec 13 09:24:39 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site2.com/cgi-bin/php.cgi [Fri Dec 13 09:24:40 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site2.com/cgi-bin/php4  ### SITE 3 ### [Fri Dec 13 09:24:40 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site3.com/cgi-bin/php [Fri Dec 13 09:24:40 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site3.com/cgi-bin/php5 [Fri Dec 13 09:24:40 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site3.com/cgi-bin/php-cgi [Fri Dec 13 09:24:40 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site3.com/cgi-bin/php.cgi [Fri Dec 13 09:24:40 2013] [error] [client 107.20.169.255] script not found or unable to stat: /var/www/vhosts/site3.com/cgi-bin/php4   As you can see, some attackers are probing for the existence of software that might be installed on the server, perhaps to search for exploits. I see things like this all the time. One concern is that these logs don't indicate when they were successful. And, in one case, the same IP address is even probing two different sites at the same time. This time the requests seem to be coming from clouds, but that is not always the case.  When the IP address is from places like China or Russia, I manually deny the entire range and restart Apache. But when IP addresses are in the USA, I can't deny the entire range because they could theoretically be used by legitimate customers.  I don't know if this is possible, but I'd like to dynamically block an IP address when certain URL paths are requested.  For example, an IP address would automatically be denied if it requested /cgi-bin/php-cgi  The deny could be temporary in nature. Apache would automatically handle this without requiring a restart.  Is anything like this possible?

Im trying to keep away some attackers that try to exploit XSS vulnerabilities from my website, I have found that most of the malicious attempts start with a classic "alert(document.cookie);\" test. The site is not vulnerable to XSS but I want to block the offending IP addresses before they found a real vulnerability, also, to keep the logs clean.  My first thought is to have a script constantly checking in the Apache logs all IP addresses that start with that probe and send those addresses to an iptables drop rule. With something like this:  cat /var/log/httpd/-access_log | grep "alert(document.cookie);" | awk '{print $1}' | uniq  Why would be an effective way to send the output of that command to iptables?  Thanks in advance for any input!


I would like to return a dictionary where values are lists sorted by descending length of values.  ex.   data = {'r': [4,3],'t': [4,5,6], 'n': [1,6]}   must give  data = {'t': [4,5,6], 'r': [4,3],'n': [1,6]}   Then, after this first sort, I would like that keys be sorted in alphabetical order for values of same length, as with  data = {'t': [4,5,6], 'n': [1,6], 'r': [4,3]}    Is there a way?

I have a dictionary of values read from two fields in a database: a string field and a numeric field. The string field is unique, so that is the key of the dictionary.  I can sort on the keys, but how can I sort based on the values?  Note: I have read Stack Overflow question here  and probably could change my code to have a list of dictionaries, but since I do not really need a list of dictionaries I wanted to know if there is a simpler solution to sort either in ascending or descending order.


What does an applicant for admissions in a PhD program do if a recommender put down on an already-submitted application suddenly goes AWOL and does not submit his letter of recommendation? Would a missing letter of recommendation completely disqualify the applicant, or does the admissions committee try to make contact with the AWOL recommender?

One of my professors this term promised to write me a recommendation letter for grad school. However, tomorrow is the deadline and her letter is not on the application website. She really liked me, so it's probably a case of her forgetting about/misremembering the deadline.  However, I can't reach her via e-mail, and she's the kind of person who puts absolutely no information online (phone, travel plans, etc). Perhaps she's on some sort of trip to a conference or something.   What can I do (with respect to the graduate programs I have applied to) to resolve this? Is there usually some sort of university policy regarding this situation? I really don't want to be unable to apply for grad school because a professor forgot to check her e-mail.  This situation is different from , because in my situation the deadline has not yet passed.


The method is supposed to check if the linked list has more than one of the same entry. I tried getting the method to check if the head is equal to the current node and then having the current equal to current.next, if the head never equals the current, i have the head equal to head.next and restart the current by assigning it to firstNode. When i try to test the code it gives me the following error:     Exception in thread "main" java.lang.NullPointerException at LinkedBag1.hasDuplicateEntries(LinkedBag1.java:182)    java:182 is while((!head.equals(current)) || (current != null)){   Not sure what this means and what is causing my method to make this error appear.       public boolean hasDuplicateEntries(){     Node head = firstNode;     Node current = head.next;     boolean duplicate = true;      while((!head.equals(current)) || (current != null)){         if(head.equals(current)) {             duplicate = true;         }         else{             current = current.next;         }         current = firstNode;         head = head.next;       }       return duplicate; }   Is there anything I did wrong in my method? Any help will be appreciated.

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?


So...  ls -l --block-size=MB   tells me that directory is one MB  ls -l --block-size=MB directory   tells me there's a 3MB file inside the directory.  Shouldn't that make the directory at least 3MB?  How can the directory be smaller than its contents?

What does size of a directory mean in output of ls -l command?


I'm learning for my exam which is tomorrow and in the practice exam there are a lot of questions where you can choose between those p-values, but what do they mean?   an example question  A test is standardized in a way that μ = 100. The population variance is unknown. In a sample of 31 persons we find x = 103 and s = 6.28. The research question is whether the sample is drawn from a population with a mean score greater than 100. Can the H0 be rejected with ↵ = 0.05? a. No,P>0.05 b. Yes, 0.025 < P  0.05  c. Yes, 0.01 < P ≤ 0.025  d. Yes, P ≤ 0.01  i just don't understand for what they all stand. how can i interpret them?

After taking a statistics course and then trying to help fellow students, I noticed one subject that inspires much head-desk banging is interpreting the results of statistical hypothesis tests.  It seems that students easily learn how to perform the calculations required by a given test but get hung up on interpreting the results.  Many computerized tools report test results in terms of "p values" or "t values".  How would you explain the following points to college students taking their first course in statistics:   What does a "p-value" mean in relation to the hypothesis being tested?  Are there cases when one should be looking for a high p-value or a low p-value? What is the relationship between a p-value and a t-value?


I am working through a linear algebra text and I am doing exercises in a chapter dealing with linear transformations and linear functions. I am trying to come up with the transformation matrix for a vector reflected on a line in two-dimensional space. Please try to the answer the question without change of basis or eigenvalues as I have not reached that chapter. I am confident this does not warrant complicated trigonometry either.  So far I have projected the basis vectors of the space onto the line and found an orthogonal line in search of a solution. I am not sure where to go from here. Thank you

I'm having trouble understanding the solution presented below (It's from a textbook). I tried to get something similar, but to no avail. Help me find the way he derived those a,b,x2 and y2 expressions.   Point p is a point which we want to reflect (It's a simple structure with two integers x and y representing coordinates on a 2d plane); (x0,y0) and (x1,y1) are coordinates of endpoints of a line.  Expected result is a new point with reflected coordinates.   Point mirror(Point p, int x0, int y0, int x1, int y1) {     double dx,dy,a,b;    long x2,y2;    Point p1; //reflected point to be returned      dx  = (double) (x1 - x0);    dy  = (double (y1 - y0);     a   = (dx * dx - dy * dy) / (dx * dx + dy*dy);    b   = 2 * dx * dy / (dx*dx + dy*dy);     x2  = Math.round(a * (p.x - x0) + b*(p.y - y0) + x0);     y2  = Math.round(b * (p.x - x0) - a*(p.y - y0) + y0);     p1 = Point((int)x2,(int)y2);      return p1;  }


$$\int_ {0}^{\infty} \frac{(e^{3x}-e^x) \ \mathrm dx}{x(e^x+1)(e^{3x}+1)}$$ I tried converting it to $$\int_ {0}^{\infty} \frac{\big((e^{3x}+1)-(e^x+1)\big) \ \mathrm dx}{x(e^x+1)(e^{3x}+1)}$$ integral-calculator.com says no antiderivative found. I would like to see how it is solved by Feynman's Trick.

I want to find the following integral: $$\int_{0}^{\infty} \frac{e^{3x}-e^x}{x(e^{3x}+1)(e^x+1)} dx$$ I have been trying to apply simple substitutions like $u=e^x$, to simplify the integral without any luck. I simplified it to  $$\int_{0}^{\infty} \frac{1}{x(e^x+1)}-\frac{1}{x(e^{3x}+1)}dx$$  which seems to have increased my problems.  Wolfram Alpha gives the answer to be 0.5493... and the graph looks like a Gaussian distribution.  Somehow, I feel that this integral is very non-trivial due to the 'troublesome' $x$ in the denominator.


I tried to execute the following command but i got below error  sudo apt-get apt install -y ruby-dev nodejs postgresql-client redis-server wkhtmltopdf memcached      E: Invalid operation apt

How can I install applications like Google Chrome on Ubuntu?  Are there any commands to install an application?    Index of answers:


Wanted to use up expired orange juice in muffins or cake.

This has been discussed briefly elsewhere (e.g. ), but it doesn't seem to have been asked generally.  In the USA, there are a variety of dates printed on foods. Unfortunately, there seems to be little convention. The list includes at least the following (feel free to add more!):   Best by [DATE] Best if used by [DATE] Best before [DATE] Expiry date: [DATE] Expiration date: [DATE] Expires by [DATE] Use by [DATE] Use before [DATE] Freeze by [DATE] Eat fresh or freeze by [DATE]   What meaning is implied/conveyed by each of those?  For example:   What do each of those mean in terms of taste, quality, safety, etc?  Are any of them firmer deadlines than another, and are any intended to be mere guidelines?  Common sense tells us that "expires on [DATE]" means it's assumed to be unsafe after [DATE]), but does it say anything more -- or less -- than that, and what of the others?


I came across this statement...  "Use custom controllers when you want your Visualforce page to run entirely in system mode"  in . What does running in system mode means? Can anyone explain in detail?  Thanks

The VisualForce Developer's Guide says:     Like other Apex classes, all custom controllers run in system mode. Consequently, the current user's credentials   are not used to execute controller logic, and the user's permissions and field-level security do not apply.   To play around with this idea, I set up a profile that could read the Case object, but did not have visibility of the Description field. I then assigned this profile to a user.  My understanding of the quote from the VF developer's guide was that any user would still be able to access the field (i.e. see it if it was referenced in a VF page). However, that doesn't appear to be the case. The following code is a quick page that displays the Description field. Logged in as the test user, the field is not visible.  <apex:page controller="PermissionsController">     <apex:form >         <apex:pageBlock >             <apex:pageBlockSection >                 <apex:outputLabel value="{!c.Description}" />             </apex:pageBlockSection>         </apex:pageBlock>     </apex:form> </apex:page>      public class PermissionsController {      public Case c {get; set;}      public PermissionsController() {         c = [SELECT Id, Description FROM Case WHERE CaseNumber = '00001031'];     }   }   Interestingly, even when I switch the Case permissions off completely for the test profile, the user with that profile can still see the page, if not the field, but if I use a standard controller, then the normal insufficient privileges page is shown.  Does the quote basically mean that the code will still access all objects and fields referenced in the controller, even if the running user doesn't have permission, but the normal field level visibility is applied for the VisualForce page?


i have a HP gamer laptop 15 () with Ubuntu 18.04.  I hardly get 3 hours of battery (the usual are 2 to 2.5 hours) and that is with, Bluetooth off, keyboard back light off and working with the internet browser and some documents.  Installed TLP with its default settings and i didn't noticed any change.  The laptop has:   i5-9300 16 gb ram 256 gb ssd nvidia gtx 1050 3 cells 52,5 WH battery   I know that being a gaming laptop i cant expect a great battery life but i think 2 to 2.5 hours is too short for battery time, even more doing light stuff.  Is there any way to improve the battery life or this is the more i'll get of it??

This question is present as a matter of historical interest.  While you are encouraged to help maintain its answers, please understand that "big list" questions are not generally allowed on Ask Ubuntu and will be closed per the .   It is possible to greatly extend the usage time of a laptop or netbook running on battery by disabling various services and installing various packages.   What tricks or tips do people have for getting an extra hour or two out of their batteries?


if I create a list like this: list1 = [[0] * 5] * 5  And then I edit a value of it like this: list1[0][0] = 99  When I print list1, I get the following output: [[99, 0, 0, 0, 0], [99, 0, 0, 0, 0], [99, 0, 0, 0, 0], [99, 0, 0, 0, 0], [99, 0, 0, 0, 0]]  Why has it edited the first index of each list when I have told it to just edit the first index of the first list? If I create a list differently like list(range(1,26)), it works perfectly fine.

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


For $a,b,c>0$. Prove that $$\frac{1}{\left(2a+b\right)^2}+\frac{1}{\left(2b+c\right)^2}+\frac{1}{\left(2c+a\right)^2}\ge\frac{1}{ab+bc+ca}$$    Outside $a=b=c$ I can't exploit what from it

Let $x,y,z>0$: Prove that:   $\frac{1}{(x+2y)^2}+\frac{1}{(y+2z)^2}+\frac{1}{(z+2x)^2} \geq\frac{1}{xy+yz+zx}$  I tried to apply Cauchy - Schwarz's inequality but I couldn't prove this inequality!


Why do they do it?   If I apply some constant force on a charged particle, would it gain velocity just like any other particle or would it lose its energy by emitting radiation?  What if I observe a charged particle from an accelerating frame, would the particle still radiate energy? If so, where does that energy come from ?   Please explain clearly about how the velocity of an electron increases when a constant force is applied.  Not a duplicate of  because my questions are not answered there.

Let's consider it case by case:  Case 1: Charged particle is at rest. It has an electric field around it. No problem. That is its property.  Case 2: Charged particle started moving (it's accelerating). We were told that it starts radiating EM radiation. Why? What happened to it? What made it do this?  Follow up question: Suppose a charged particle is placed in uniform electric field. It accelerates because of electric force it experiences. Then work done by the electric field should not be equal to change in its kinetic energy, right? It should be equal to change in K.E + energy it has radiated in the form of EM Waves. But then, why don't we take energy radiated into consideration when solving problems? (I'm tutoring grade 12 students. I never encountered a problem in which energy radiated is considered.)


I'm running a Ubuntu server and this evening since rebooting it I am not getting the error message Cannot write to '' (No space left on device).  Earlier I did unzip a large directory in to /root which created around 100 files, I then removed these using rm /root/*. I did check ls prior to doing this and the only files in /root were the actual ones that I wanted to remove. Did I do something wrong here?  Here are some outputs:  df -h  root@localhost:~# df -h Filesystem      Size  Used Avail Use% Mounted on /dev/xvda        47G   47G     0 100% / none            4.0K     0  4.0K   0% /sys/fs/cgroup devtmpfs        494M  8.0K  494M   1% /dev none             99M  192K   99M   1% /run none            5.0M     0  5.0M   0% /run/lock none            495M     0  495M   0% /run/shm none            100M     0  100M   0% /run/user   df -i  root@localhost:~# df -i Filesystem      Inodes IUsed   IFree IUse% Mounted on /dev/xvda      3129344 52147 3077197    2% / none            126527     2  126525    1% /sys/fs/cgroup devtmpfs        126232  1410  124822    2% /dev none            126527   792  125735    1% /run none            126527     4  126523    1% /run/lock none            126527     1  126526    1% /run/shm none            126527     2  126525    1% /run/user   du -Pshx /* 2>/dev/null  root@localhost:~# du -Pshx /* 2>/dev/null 9.1M    /bin 4.0K    /boot 4.0K    /dev 6.8M    /etc 31M     /home 29M     /lib 4.0K    /lib64 16K     /lost+found 8.0K    /media 4.0K    /mnt 4.0K    /opt 0       /proc 76K     /root 192K    /run 7.6M    /sbin 4.0K    /srv 0       /sys 12K     /tmp 611M    /usr 541M    /var   Can someone please suggest something here, as I'm out of ideas?

I have file servers which are used to store files. Files might reside there for a week, or for a year. Unfortunately, when I remove files from the server, df command doesn't reflect the freed up space. So eventually, the server gets filled up (df shows 99%), and my script doesn't send any more files there, except there might be a few dozen GB of free space on there.   I got noatime flag on the mounted partitions if that makes any difference.


I'm sure others have faced this frustrating issue in the past.   Say you have a dozen tabs open in a browser and you are at a hotel or cafe attempting to use their wifi. You select the wifi ID and all of a sudden, the wifi login screen populates all of your tabs, with no option to go back to the previous website. The content in those tabs has been lost, forever.   How does one prevent this from happening?

It is common for public Wi-Fi access points to include login pages, even at times, when they’re free (i.e. Starbucks, many airports, hotels, etc).  I’m often in a situation where I’ll open up Chrome/Firefox, with and all my previously open tabs will start to reload.  If there is a wireless login redirection page, however, every tab is redirected and reloaded and the previous page is lost from history (and the back button won't return to it).  Is there any way to avoid or circumvent this behavior?


I have dual nationality ie a British and a South African passport. My British passport has expired I will be renew once in the UK. I will be travelling from South Africa, into Dublin and on to Heathrow.  Do I need a visa using my South African passport commuting from IRELAND to UK?

I have a valid South African passport and an expired British passport - it expired 18 October 2009. I need to travel to the UK in March 2015. Do I need a visa to get into the UK?


I am supposed to get two big integer numbers (up to 600 digits) from console screen and write the result on the console again.  I defined two variables of type std::string to store two big integer numbers .I take their values from the user. To take the sum of that two numbers, I defined two vectors to store the digits of that two strings of numbers .   Here is the problem, when I try to loop through the vector to print the digits  that I took from strings of numbers I get the following result .The Ascii values of the digits are printed on The Console. Could anyone tell me how to fix this problem please.   Note: The code is still not complete .  For the first string I took the numbers 9 8 7 6 5 4 3 2 1 from the user , on the console window I got the following result.   [0]57  [1]56  [2]55  [3]54  [4]53  [5]52  [6]51  [7]50  [8]49      #include <iostream>     #include <sstream>     #include <vector>     #include <algorithm>       std::string Sum_Of_Two_Long_Integers()     {       std::string First_String ;       std::string Second_String ;       std::string Result_String ;        std::cout << "Please enter the first number: " ;       std::getline(std::cin, First_String);       std::cout << "Please enter the second number: " ;       std::getline(std::cin, Second_String);        std::vector <int> First_String_Vector (First_String.length()) ;       std::vector <int> Second_String_Vector (Second_String.length()) ;        for(int Counter = 0 ; Counter  < First_String_Vector.size() ; ++ Counter)       {          First_String_Vector[Counter] = First_String[Counter] ;          Second_String_Vector[Counter] = Second_String[Counter] ;          std::cout << "[" << Counter << "]" << First_String_Vector[Counter] << std::endl ;       }        return Result_String ;    }     int main()    {       std::string Result_String  = Sum_Of_Two_Long_Integers() ;       std::cout << "Result = " << Result_String << std::endl ;        return 0 ;    }

I am using the RSA Algorithm for encryption/decryption, and in order to decrypt the files you have to deal with some pretty big values. More specifically, things like   P = C^d % n   = 62^65 % 133   Now that is really the only calculations that ill be doing. I have tried using Matt McCutchen's BigInteger Library, but I am getting a lot of compiler errors during linking, such as:  encryption.o(.text+0x187):encryption.cpp: undefined reference to `BigInteger::BigInteger(int)'  encryption.o(.text+0x302):encryption.cpp: undefined reference to `operator<<(std::ostream&, BigInteger const&)'  encryption.o(.text$_ZNK10BigIntegermlERKS_[BigInteger::operator*(BigInteger const&) const]+0x63):encryption.cpp: undefined reference to `BigInteger::multiply(BigInteger const&, BigInteger const&)'   So I was wondering what would be the best way to go about handling the really big integers that come out of the RSA Algorithm.  I heard that a possibility would be to declare your variables as a double long, so...  long long decryptedCharacter;   but I'm not sure exactly how big of an integer that can store.    Well for example, I try to compile and run the following program using dev C++:  #include iostream  #include "bigint\BigIntegerLibrary.hh"  using namespace std;  int main() {     BigInteger a = 65536;     cout << (a * a * a * a * a * a * a * a);     return 0; }   then I get those errors.  Derek, I thought that by including the BigIntegerLibrary.hh file, that the compiler would go through and compile all the necessary files that it will use.  How should I try and compile the program above in order to resolve the linking errors?


I have booked a flight from Delhi to Prague with layover at Paris for 12 hrs. Want to do sight seeing in Paris during layover period.   Do I have to apply Schengen Visa from French embassy or Czech embassy in India.

I want to apply for a Schengen visa. I am planning to stay in Paris  for 3 nights and 7 nights in Switzerland.  Which visa do I need to apply for? If I choose France then is it possible that I can stay for 2 nights in France and 8 in Switzerland after visa approval.


What is the etimology of word History? Is it in English word His Story, or is this only another fancy coincidence?

According to , history comes from the same root as story. If they are from the same word, where does hi- come from? Is it just because of the English habit of taking names from other languages verbatim or is there something more to it?


I am looking an adjective which can be used to describe people who know a bit of everything , somebody who is not superficial in term of general information irrespective of someone's age.  I'd rather not  use the word intellectual because it depicts an academic or philosopher who is very good at the area they the work area in my mind.Can we call a college guy as intellectual just because he reads a lot and knows pretty much something on everything?  I'd rather not  use the word well-rounded because it includes someone's sportive activities but I am asking more about knowledge.   Maybe a word which can be used by someone  to describe themselves who dare to attend " who wants to be millionaire" contest ?

Is there an appropriate word for the antonym of "full-stack", as in programming? Someone who knows a lot of things just as a full-stack programmer, but without mastering them.


im running gnome ubuntu 14.10/windows 7 ultimate on a hp pavilion g6 1d98dx and it appears that my wireless button is somehow bound to something to do with the softblock (not the hardblock as it should be) i ran rfkill list all and it gives me   0: phy0: Wireless LAN Soft blocked: no Hard blocked: yes   but if i press my wireless button (f12) nothing happens to the indicator light but when i run rfkill list all again it says  0: phy0: Wireless LAN Soft blocked: yes Hard blocked: yes   any ideas are welcome ive tried installing diffrent distros such as mint, ubuntu, kubuntu, deepin, and fedora but they all have the same problem

I would like to know if my  is in anyway compatible with Ubuntu.  Dual booting Ubuntu 15.04 with windows 8.1 on an HP Pavilion G6 1d98dx.  I've tried so many different distros but the problem is the same on all of them "wireless disabled by hardware switch" I've tried rfkill unblock all but that did not fix the problem.  Bus 002 Device 002: ID 04f2:b293 Chicony Electronics Co., Ltd  Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 002: ID 05dc:a20b Lexar Media, Inc.  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub 00:00.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h Processor Root Complex 00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] BeaverCreek [Radeon HD 6520G] 00:01.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] BeaverCreek HDMI Audio [Radeon HD 6500D and 6400G-6600G series] 00:04.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Family 12h Processor Root Port 00:11.0 SATA controller: Advanced Micro Devices, Inc. [AMD] FCH SATA Controller [IDE mode] 00:12.0 USB controller: Advanced Micro Devices, Inc. [AMD] FCH USB OHCI Controller (rev 11) 00:12.2 USB controller: Advanced Micro Devices, Inc. [AMD] FCH USB EHCI Controller (rev 11) 00:13.0 USB controller: Advanced Micro Devices, Inc. [AMD] FCH USB OHCI Controller (rev 11) 00:13.2 USB controller: Advanced Micro Devices, Inc. [AMD] FCH USB EHCI Controller (rev 11) 00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller (rev 13) 00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD] FCH Azalia Controller (rev 01) 00:14.3 ISA bridge: Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge (rev 11) 00:14.4 PCI bridge: Advanced Micro Devices, Inc. [AMD] FCH PCI Bridge (rev 40) 00:15.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Hudson PCI to PCI bridge (PCIE port 0) 00:15.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Hudson PCI to PCI bridge (PCIE port 1) 00:15.2 PCI bridge: Advanced Micro Devices, Inc. [AMD] Hudson PCI to PCI bridge (PCIE port 2) 00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h/14h Processor Function 0 (rev 43) 00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h/14h Processor Function 1 00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h/14h Processor Function 2 00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h/14h Processor Function 3 00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h/14h Processor Function 4 00:18.5 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h/14h Processor Function 6 00:18.6 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h/14h Processor Function 5 00:18.7 Host bridge: Advanced Micro Devices, Inc. [AMD] Family 12h/14h Processor Function 7 01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 05) 07:00.0 Network controller: Ralink corp. RT5390 Wireless 802.11n 1T/1R PCIe 08:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5209 PCI Express Card Reader (rev 01)


We have some new hardware in our office which runs its own customized Linux OS.   How do I go about figuring which distro it's based on?

I'm working on a simple bash script that should be able to run on Ubuntu and CentOS distributions (support for Debian and Fedora/RHEL would be a plus) and I need to know the name and version of the distribution the script is running (in order to trigger specific actions, for instance the creation of repositories). So far what I've got is this:  OS=$(awk '/DISTRIB_ID=/' /etc/*-release | sed 's/DISTRIB_ID=//' | tr '[:upper:]' '[:lower:]') ARCH=$(uname -m | sed 's/x86_//;s/i[3-6]86/32/') VERSION=$(awk '/DISTRIB_RELEASE=/' /etc/*-release | sed 's/DISTRIB_RELEASE=//' | sed 's/[.]0/./')  if [ -z "$OS" ]; then     OS=$(awk '{print $1}' /etc/*-release | tr '[:upper:]' '[:lower:]') fi  if [ -z "$VERSION" ]; then     VERSION=$(awk '{print $3}' /etc/*-release) fi  echo $OS echo $ARCH echo $VERSION   This seems to work, returning ubuntu or centos (I haven't tried others) as the release name. However, I have a feeling that there must be an easier, more reliable way of finding this out -- is that true?  It doesn't work for RedHat. /etc/redhat-release contains : Redhat Linux Entreprise release 5.5  So, the version is not the third word, you'd better use :  OS_MAJOR_VERSION=`sed -rn 's/.*([0-9])\.[0-9].*/\1/p' /etc/redhat-release` OS_MINOR_VERSION=`sed -rn 's/.*[0-9].([0-9]).*/\1/p' /etc/redhat-release` echo "RedHat/CentOS $OS_MAJOR_VERSION.$OS_MINOR_VERSION"


if  $P(x) = x^2 + x + 41$  compute for $x = 1,2,3..10$ and check if the values are prime.  I have solved this by trial division. Might it be that P(1), P(2), P(3)... are all primes? This one is out of my depth. I vaguely suspect that proof by induction is the way to go but i do not know how. Please guide me through the proof or to relevant readings that will help me.

Here's a problem that showed up on an exam I took, I'm interested in seeing if there are other ways to approach it.     Let $n\in\{0,1,...,39\}$. Prove that $n^2+n+41$ is prime.    I shall provide my own solution, though I am curious does anyone know how to do this without using PIDs?


How do we know that $(p_1 \cdot \ldots \cdot p_k)+1$ is always prime, for $p_1 = 2$, $p_2 = 3$, $p_3 = 5$, $\ldots$ (i.e., the first $k$ prime numbers)?  Euclid's proof that there is no maximum prime number seems to assume this is true.

I've expressed Euclid's proof on the infinitude of primes on Mathematica:  f[x_] := Product[Prime[n], {n, 1, x}] + 1 TableForm[Table[{f[x], PrimeQ[f[x]]}, {x, 1, 20}]]   Which results in:  $\begin{array}{ll}  3 & \text{True} \\  7 & \text{True} \\  31 & \text{True} \\  211 & \text{True} \\  2311 & \text{True} \\  30031 & \text{False} \\  510511 & \text{False} \\  9699691 & \text{False} \\  223092871 & \text{False} \\  6469693231 & \text{False} \\  200560490131 & \text{True} \\  7420738134811 & \text{False} \\  304250263527211 & \text{False} \\  13082761331670031 & \text{False} \\  614889782588491411 & \text{False} \\  32589158477190044731 & \text{False} \\  1922760350154212639071 & \text{False} \\  117288381359406970983271 & \text{False} \\  7858321551080267055879091 & \text{False} \\  557940830126698960967415391 & \text{False} \\ \end{array}$  The proof flaws for all those values, how is it considered a proof then? I guess that there might be infinite prime numbers according to the proof, but what is the guarantee that at some point it won't fail indefinitely?


Let $X$ be a noetherian integral separated scheme which is regular in codimension one. Then the proposition states that $\operatorname{Cl}(X)\cong\operatorname{Cl}(X\times\mathbb{A}^1_\mathbb{Z})$, where $\operatorname{Cl}$ denotes the divisor class group. In the proof, the author defines a homomorphism $\operatorname{Cl}(X)\to\operatorname{Cl}(X\times\mathbb{A}^1_\mathbb{Z})$ by sending a prime divisor $Y$ on $X$ to $\pi^{-1}(Y)$ on $X\times\mathbb{A}^1_\mathbb{Z}$.  Why is $\pi^{-1}(Y)$ a prime divisor?  Reducing to affine open sets, it suffices to prove that if $A$ is a noetherian integral domain (regular in codimension one) and $\mathfrak{p}$ is a prime ideal of $A$ with height $1$, then $\mathfrak{p}[t]$ is a prime ideal of $A[t]$ with height $1$. How do I prove this? Why can't there be a prime $\mathfrak{q}$ of $A[t]$ with $0\subsetneq\mathfrak{q}\subsetneq\mathfrak{p}[t]$ and $\mathfrak{q}\cap A=0$?

For Noetherian rings $R$ and $S$, let $R\rightarrow S$ be a faithfully flat ring extension and $I$ an ideal of $R$. Does $\operatorname{ht}I=\operatorname{ht}IS$ hold?    Is it a conclusion in some books on commutative algebra?


Linq offers a method to filter an enumerable for a given type.  public static IEnumerable<TResult> OfType<TResult>(this IEnumerable source);   But this means I need to now the type (and have access to it) at compile time. In order to let someone define the type as string how would I call this having the type only as string?  Sure, I could write my own function (since the  isn't that heavy).  I am just curious if there is a way to call without writing my own method. The compiler complains on everything I tried so far.  In my case I have one lib defining an attribute and a second lib allowing to something if the attribute is set. But the filtering library does not know the first library, so I would need to pass this as string.  Well, in detail I am trying to write a Swagger/Swashbuckle operation filter adding the infos for typical pagination. Unfortunatly the pagination itself is in an (replaceable) pagination library. So I need to pass the information which attribute defines that this methods supports pagination from the pagination library to the Swagger/Swaschbuckle library (or define it as value in the configuration).  The code itself does only check if the attribute is set (thats all where I need the type).    public void Apply(Operation operation, OperationFilterContext context)   {     bool paginationSupported = context.ControllerActionDescriptor       .GetControllerAndActionAttributes(inherit: true)       .OfType<MyTypeAsString>() //???       .Any();      if (paginationSupported) // do stuff   }

What's the best way to call a generic method when the type parameter isn't known at compile time, but instead is obtained dynamically at runtime?  Consider the following sample code - inside the Example() method, what's the most concise way to invoke GenericMethod<T>() using the Type stored in the myType variable?  public class Sample {     public void Example(string typeName)     {         Type myType = FindType(typeName);          // What goes here to call GenericMethod<T>()?         GenericMethod<myType>(); // This doesn't work          // What changes to call StaticMethod<T>()?         Sample.StaticMethod<myType>(); // This also doesn't work     }      public void GenericMethod<T>()     {         // ...     }      public static void StaticMethod<T>()     {         //...     } }


After the release of Minecraft I saw more and more rip offs of the game but some actually began to change it up a bit making the game have a organic look instead of the iconic blocky one that Minecraft does. If you'd like to look at the game that i'm referring to you can do so . If you skip to around 50 seconds on the first video the steam page offers you can see the mining part that i'm wondering about.   I was wondering how this affect is achieved where they are able to remove part of the 3D object on collison with the players pick. I have heard about constructive solid geometry before and figured that could have been used but i'm not so sure.

A few days ago I found something called voxel terrains and I think that they're pretty cool.  But I don't know anything generating them. Do you model it in your modeling software or use something like a heightmap? I read on  that voxels are like 3d pixels or volumetric pixels.  After I make the voxel terrain, how can I take these voxels and make them  destroyable/diggable?   I will pick the best answer based on:   code and algorithms. preferably based in C# explanations. I am a beginner with algorithms but I'm very familiar with object oriented programming step by step demonstrations. Not only concept but direction. diagrams/illustrations. No, not screenshots of other engines.    I know that this is a complicating subject. But, thanks for any help!  No, I'm not trying to make a minecraft clone.    Edit  Thanks to everyone for your great help (especially Nick Wiggill)!  is what I managed to make (Work in progress).