My query is similar to , which was closed as “unclear”, without any proper solutions being suggested.  Let me try to see if I can describe my setup more clearly than the original poster.  I have a project named MyProject.  Under the MyProject project there are three packages, the default package, Pkg1 and Pkg2.  The default package contains ClassA, Pkg1 contains ClassB and Pkg2 contains ClassC.  ClassC (in Pkg2) needs to reference ClassA (in default package) and ClassB (in Pkg1).  The import statement "import Pkg1.ClassB;" works like a charm but I am unable to figure out how to import ClassA.    Regards, Sandeep

I'm working now together with others in a grails project. I have to write some Java-classes. But I need access to an searchable object created with groovy. It seems, that this object has to be placed in the default-package.   My question is: Is there a way to access this object in the default-package from a Java-class in a named package?


My question in full is as follows - "What is meant by Principal Component Analysis. including in the explanation the terms: geometric information; covariance matrix; orthogonal transformation; Spectral Theorem My understanding of Principal Component Analysis is that it reduces a number of variables x1, x2... to a smaller set of principal components that store as much of the original information from the original variables in these newly created principal components. However I don't fully understand all of these other terms or how they relate to PCA.

In today's pattern recognition class my professor talked about PCA, eigenvectors and eigenvalues.   I understood the mathematics of it. If I'm asked to find eigenvalues etc. I'll do it correctly like a machine. But I didn't understand it. I didn't get the purpose of it. I didn't get the feel of it.        I strongly believe in the following quote:     You do not really understand something unless you can explain it to your grandmother. -- Albert Einstein   Well, I can't explain these concepts to a layman or grandma.   Why PCA, eigenvectors & eigenvalues? What was the need for these concepts? How would you explain these to a layman?


This is on a fresh install of Ubuntu 14.04 running on a VPS.  For example the following will work:  server {     listen 8080 default_server;     root /var/www;      location / {         try_files $uri $uri/ =404;     } }  server {     listen 80 default_server;     root /var/www;      location / {         try_files $uri $uri/ =404;     } }   When I visit the page it will be my index.html.  But if I try to make nginx listen on another port (35729):  server {     listen 35729 default_server;     root /var/www;      location / {         try_files $uri $uri/ =404;     } }   or even one that's maybe slightly more used (3000 by nodejs servers for example)  All I get is an error saying the webpage is not available. .  Looking in netstat though says that nginx is listening for the port:  tcp        0      0 0.0.0.0:35729      0.0.0.0:*          LISTEN    15349/nginx -g daem   and iptables looks like this (which means no firewall right?)  Chain INPUT (policy ACCEPT) target     prot opt source               destination  Chain FORWARD (policy ACCEPT) target     prot opt source               destination  Chain OUTPUT (policy ACCEPT) target     prot opt source               destination   and sudo ufw status verbose yields  Status: inactive   What's going on?

This is a  about Connection Refused    We see a lot of questions to the effect      When I try to connect to a system I get a message      Connection refused      Why is this ?


I am having trouble with my google sheets script and I wondered if anyone had any advice for a beginner. I want my script to check a cell value (Sheet1, H2), then send an email if the value = 29. However, at the moment it will send an email whatever value it returns, I don't think my if statement works correctly. Any ideas would be really appreciated.  function CheckExpiry() {   // Fetch the days till expiry.   var ExpiryDataRange = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet1").getRange("H2");    var ExpiryData = ExpiryDataRange.getValue();   // Check expiration   if(ExpiryData = 29){     // Fetch the email address     var emailRange = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet1").getRange("C2");     var emailAddress = emailRange.getValue();        // Send Alert Email.     var message = 'You are recieving this email as harness # is up for inspection soon, current inspection expires in the following number of days: ' + ExpiryData; // Second column     var subject = 'Your Harness Spreadsheet Alert';     MailApp.sendEmail(emailAddress, subject, message);     } }

I am completely new to coding. I am a teacher and trying to design a lesson planner tool using Google Sheets Scripts. The idea is to have a template sheet for the lesson that will copy into a new tab. That part is working fine. However, to delete the lesson I want to make it impossible for someone to accidentally delete the template. It is succeeding in not deleting the template tab if "Delete Lesson" is clicked.   However, it is displaying the alert that you cannot delete the template for the other tabs (but then deleting the tab as it should) This is the .  Any help is greatly appreciated!  I used this code at first:  function DeleteTab1() {     var spreadsheet = SpreadsheetApp.getActive();     var sheet = spreadsheet.getActiveSheet();     var sheetname = sheet.getName();     if(sheetname != "Template")  {      spreadsheet.deleteActiveSheet();    }    else {       SpreadsheetApp.getUi().alert('The template cannot be deleted');      }  }   Then I tried this and had the same problem:  function DeleteTab1() {    var spreadsheet = SpreadsheetApp.getActive();     var sheet = spreadsheet.getActiveSheet();     var sheetname = sheet.getName();     if(sheetname != "Template")  {      spreadsheet.deleteActiveSheet();    }    if(sheetname = "Template") {       SpreadsheetApp.getUi().alert('The template cannot be deleted');      }  }


how to uninstall ubuntu 18.04 in dell n5110 and install windows back

I have absolutely no experience with Linux, and I desperately need to get my computer back up and running again with Windows.  How do I remove Ubuntu and reinstall Windows?    Editor's note: many of the answers are about removing Ubuntu from dual-boot but keeping Windows (which is a bit complicated), while other answers are about removing Ubuntu from single-boot (which is easy: basically just format the disk while installing Windows). The question as written is ambiguous between dual-boot or single-boot.


I am reading book "Fuzzy Logic With Engineering Applications, Wiley" written by Timothy J. Ross. I am reading chapter 7 and in this chapter, "Batch Least Squares Algoritm" has been defined. It illustrates the development of a nonlinear fuzzy model for the data in Table 7.1 using the Batch Least Squares algorithm.    At the page 218 there is a mathematical equation:     I have two questions:  1- As you can see, there is a "exp" phrase (in the red rectangle). What is this? Is it the exponential function? ()  At the link, "" it was stated at the link that it is an exponential function, but I noticed that ordinary paranthesis has been used. In my equation, square brackets is used.  2- What is the purpose of the equation?   Thanks in advance.

What is the meaning of the notation $\exp(\text{expression})$ ?  I think that it's something of the form $a^\text{expression}$ but does it mean that the base $a=e$ or can it be any base?


Am I able to prove the monotonicity with induction?

Show that $U_n:=\left(1+\dfrac{1}{n}\right)^n$, $n\in\Bbb N$, defines a monotonically increasing sequence.   I must show that $U_{n+1}-U_n\geq0$, i.e. $$\left(1+\dfrac{1}{n+1}\right)^{n+1}-\left(1+\dfrac{1}{n}\right)^n\geq0.$$  I am trying to go ahead of this step.


I know Animate Dead can give you skeletons or zombies (your choice), and Create Undead can give you Ghouls, Ghasts, Wights, or Mummies.  Is there any other WotC material expanding upon the types of undead you can have? either through spells or magic items or "other"?

In Dungeons and Dragons 3rd edition they introduced skeletons with all kinds of sizes such as Tiny, Small, Medium, Large, Huge, Gargantuan, and Colossal.   As a necromancer, it would be really entertaining to have undead of all kinds and sizes. However, Dungeons and Dragons 5th Edition limits the abilities of a necromancer, as the spell animate dead only allows the caster to reanimate Small and Medium humanoid creatures. Though it's understandable that WOTC made it this way as a way of balancing to prevent the creation of overpowered undead armies, it would be interesting for some sort of way of animating a creature larger than medium.   Personally, I like the idea of having a Gargantuan humanoid skeleton; however, I would not be sure how to apply statistics to an undead or create a proper way of balancing.  There is a section in DMG p. 282 for skeleton and zombie templates, however, the largest creature that exists with a humanoid body is a hill giant categorized as huge. Even then the challenge rating is 5 making thinking of a way of balancing difficult.  Even beyond my desires, I'm sure there are many other necromancer-loving individuals who would desire to animate and control a minotaur skeleton, or any other undead such as beasts or monstrosities.   Is there a way (even house or homebrew rules) of animating undead beyond these restrictions?


I am trying to install KDE on Ubuntu 15.04. I ran sudo apt-get install kubuntu-desktop and got this output: $ sudo apt-get install kubuntu-desktop^ Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies:  kde-telepathy-desktop-applets : Breaks: kde-telepathy-legacy-presence-applet but 1.1-0ubuntu1 is to be installed  kde-telepathy-minimal : Depends: kde-config-telepathy-accounts (>= 15.04.0) but it is not going to be installed  libksgrd5 : Depends: libkf5sysguard5-data (= 4:5.2.2-0ubuntu1) but it is not going to be installed  libksignalplotter5 : Depends: libkf5sysguard5 (= 4:5.2.2-0ubuntu1) but it is not going to be installed                       Depends: libkf5sysguard5-data (= 4:5.2.2-0ubuntu1) but it is not going to be installed  libktpotr9 : Breaks: libktpotrprivate8 (< 15.03.80) but 0.9.0-0ubuntu3 is to be installed  libprocesscore5 : Depends: libkf5sysguard5-data (= 4:5.2.2-0ubuntu1) but it is not going to be installed  libprocessui5 : Depends: libkf5sysguard5-data (= 4:5.2.2-0ubuntu1) but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).  I ran sudo apt-get -f install and got this output: $ sudo apt-get -f install Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required:   linux-headers-3.19.0-15 linux-headers-3.19.0-15-generic   linux-headers-3.19.0-21 linux-headers-3.19.0-21-generic   linux-image-3.19.0-15-generic linux-image-3.19.0-21-generic   linux-image-extra-3.19.0-15-generic linux-image-extra-3.19.0-21-generic   linux-signed-image-3.19.0-21-generic Use 'apt-get autoremove' to remove them. The following extra packages will be installed:   kde-config-telepathy-accounts The following NEW packages will be installed:   kde-config-telepathy-accounts 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. 602 not fully installed or removed. Need to get 0 B/121 kB of archives. After this operation, 712 kB of additional disk space will be used. Do you want to continue? [Y/n] y (Reading database ... 371396 files and directories currently installed.) Preparing to unpack .../kde-config-telepathy-accounts_15.04.1-0ubuntu1~ubuntu15.04~ppa1_amd64.deb ... Unpacking kde-config-telepathy-accounts (15.04.1-0ubuntu1~ubuntu15.04~ppa1) ... dpkg: error processing archive /var/cache/apt/archives/kde-config-telepathy-accounts_15.04.1-0ubuntu1~ubuntu15.04~ppa1_amd64.deb (--unpack):  trying to overwrite '/usr/share/accounts/services/google-im.service', which is also in package account-plugin-google 0.12+15.04.20150415.1-0ubuntu2 Errors were encountered while processing:  /var/cache/apt/archives/kde-config-telepathy-accounts_15.04.1-0ubuntu1~ubuntu15.04~ppa1_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)  Would someone take a look at those and give me any pointers?

For example:  $ sudo apt-get install curl Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: bsh : Depends: libjline-java but it is not going to be installed groovy : Depends: libjline-java but it is not going to be installed rhino : Depends: libjline-java but it is not going to be installed E: Unmet dependencies.   Try 'apt-get -f install' with no packages (or specify a solution).   I get the same or similar errors when I attempt to install clojure1.3, leiningen, and several other packages.   When I try the suggestion made in the error message, this is what happens:  $ sudo apt-get -f install  Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required:   diffstat linux-headers-3.2.0-26-generic linux-headers-3.2.0-26 dh-apparmor dkms html2text libmail-sendmail-perl libsys-hostname-long-perl Use 'apt-get autoremove' to remove them. The following extra packages will be installed:   libjline-java Suggested packages:   libjline-java-doc The following NEW packages will be installed:   libjline-java 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. 23 not fully installed or removed. Need to get 0 B/72.0 kB of archives. After this operation, 129 kB of additional disk space will be used. Do you want to continue [Y/n]? Y (Reading database ... 226243 files and directories currently installed.) Unpacking libjline-java (from .../libjline-java_1.0-1_all.deb) ... dpkg: error processing /var/cache/apt/archives/libjline-java_1.0-1_all.deb (--unpack):  trying to overwrite '/usr/share/java/jline.jar', which is also in package scala 2.9.2-400 Errors were encountered while processing:  /var/cache/apt/archives/libjline-java_1.0-1_all.deb E: Sub-process /usr/bin/dpkg returned an error code (1)  $ sudo apt-get upgrade Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies:  bsh : Depends: libjline-java but it is not installed  groovy : Depends: libjline-java but it is not installed  rhino : Depends: libjline-java but it is not installed E: Unmet dependencies. Try using -f.


I want to simulate a finger touch/move/etc. on capactive touch screen. Obviously using a robot arm and stylus pen is a solution, but it was expansive and the structure was too complex. It would be elegant if we can lay something (another capactive touch screen) on the original screen and drive it to simulate a finger.  I learned that a capactive touch screen is somewhat a row/column selection capacity matrix. So is it possible to make a driver system to activite certain areas in the screen and make it recognized as a finger touch?   want to simulate a static touch area, but I want a CONTROLLABLE/PROGRAMMABLE  activition of ANY area in the screen.

I want to make a device that I can place on a capacitive touch screen and it will start tapping the screen repeatedly. Is there any way to do this with the Arduino?


I know that "children" is a plural noun and "birthday" is a countable noun, but I saw this sentence in a book:     Children have a birthday cake at their birthday.    Why is "children" (which is a plural noun) followed by "a birthday cake" instead of by "birthday cakes," and why is "their" followed by "birthday" instead of by "birthdays"?

In a situation where say a group (or at least a plurality) of men is being addressed — for example on a sign passed by many married men — which is correct?  "Remind your wife."  or  "Remind your wives."


example I enter 1357 and program out 106 instead of 10          string num = Console.ReadLine();         Console.Write(Convert.ToInt32(num[1]) + Convert.ToInt32(num[3]));         Console.ReadKey();

I have a char in c#:  char foo = '2';   Now I want to get the 2 into an int.  I find that Convert.ToInt32 returns the actual decimal value of the char and not the number 2.  The following will work:  int bar = Convert.ToInt32(new string(foo, 1));   int.parse only works on strings as well.    Is there no native function in C# to go from a char to int without making it a string?  I know this is trivial but it just seems odd that there's nothing native to directly make the conversion.


I've run out of space on my root partition and I want to extend it. I've seen another posts of this topic but my lack of knowledge makes it difficult for me to achieve what i want. Here's a screenshot of my GParted Window:

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've seen examples where the query orders by count and takes the top row, but in this case there can be multiple "most frequent" values, so I might want to return more than just a single result.  In this case I want to find the most frequently appearing last names in a users table, here's what I have so far:  select last_name from users group by last_name having max(count(*));   Unfortunately with this query I get an error that my max function is nested too deeply.

I have a table like this:   Column  | Type | Modifiers  ---------+------+-----------  country | text |   food_id | int  |   eaten   | date |    And for each country, I want to get the food that is eaten most often.  The best I can think of (I'm using postgres) is:  CREATE TEMP TABLE counts AS     SELECT country, food_id, count(*) as count FROM munch GROUP BY country, food_id;  CREATE TEMP TABLE max_counts AS     SELECT country, max(count) as max_count FROM counts GROUP BY country;  SELECT country, max(food_id) FROM counts     WHERE (country, count) IN (SELECT * from max_counts) GROUP BY country;   In that last statement, the GROUP BY and max() are needed to break ties, where two different foods have the same count.  This seems like a lot of work for something conceptually simple.  Is there a more straight forward way to do it?


The  experiment consists of two interferometers, where each one of them has two 4 km long arms.  Within these, light is further trapped via Fabry-Pérot cavities to achieve a total path length of about 1,600 km.  Why does the path have to be so long? Isn't the phase that governs the interference pattern constant throughout the arm, since it just depends on the path difference between the two arms? Making them both long surely should not change this...?

Antennas for capturing radio waves need to have $\frac{\lambda}{2}$  length for optimum reception of signal. Does it imply LIGO arm length is $\frac{\lambda}{2}$ of Gravitational Wave it is trying to capture?


I have a typescript class that contains an array attribute, i would like to create a copy of this object, i used Object.assign, but the array is not duplicated  class:   export interface IDeclaration {     rechutes?: Rechute[];     text: string; }  export class Declaration implements IDeclaration {     constructor(         public rechutes?: Rechute[],         public text ?: string,     ) {} }  export interface IRechute {     dateDebut?: Moment;     dateFin?: Moment; }  export class Rechute implements IRechute {     constructor(public dateDebut?: Moment, public dateFin?: Moment) {         this.dateDebut = dateDebut ? dateDebut : null;         this.dateFin = dateFin ? dateFin : null;     } }    copy :    const copy: IDeclaration = Object.assign({}, res.body, {     text: transformMethodText(res.body.text),     rechutes: transformMethodRechutes(res.body.rechutes) });  transformMethodText(text: string) : string{     return 'test : ' + text; }  private transformMethodRechutes(rechute: Rechute): Rechute{         return Object.assign({}, rechute, {             dateDebut: rechute.dateDebut != null ? moment(rechute.dateDebut) : null,             dateFin: rechute.dateFin != null ? moment(rechute.dateFin) : null         });     }   Array will always set to empty, when i try to push some new object no change is made.  How to copy my rechutes array inside the Object.assign function ?  Thank's

What is the most efficient way to clone a JavaScript object? I've seen obj = eval(uneval(o)); being used, but . I've done things like obj = JSON.parse(JSON.stringify(o)); but question the efficiency.  I've also seen recursive copying functions with various flaws.  I'm surprised no canonical solution exists.


I have multiple folders inside one folder, I want to move all the contents of these folders up to the parent ( basically like extracting compressed files )  so what's the easiest way to accomplish this ?

I have multiple .rar files in multiple folders like this:    C:\Docs\Folder1\rarfile1-1.rar C:\Docs\Folder1\rarfile1-2.rar C:\Docs\Folder1\rarfile1-3.rar    C:\Docs\Folder2\rarfile2-1.rar C:\Docs\Folder2\rarfile2-2.rar C:\Docs\Folder2\rarfile2-3.rar    C:\Docs\Folder3\rarfile3-1.rar C:\Docs\Folder3\rarfile3-2.rar C:\Docs\Folder3\rarfile3-3.rar     I want to move all of the .rar files to the parent directory 'C:\Docs'. I have a lot more than 3 folders, so I was thinking of making a batch file or something. What would be the commands to do this? Thanks


This is basically a reverse of .  Let's say a user has a single account on several SE sites that are linked (for example, Stack Overflow, Programmers, Gaming and RPG).  They want to expose their SO and Programmers professional accounts to a professional audience, but don't want anyone to link that to their more "frivolous" Gaming/RPG accounts.  Is it possible - as a one-time event - split that one SE account into two separate accounts? The assumption is that they would be 100% independent of each other, with different logins, and no further association between them? If so, what would be the procedure?

I looked at similar questions and wanted to post a more specific one.  If I wanted one of my accounts on the network to no longer be associated to my global account, could an administrator do it manually? I mean, even if they could, would they?  It's a matter of professionalism. I don't want one of my accounts on the network to be visible from my other accounts. I just want that to be under a separate email that's not one of the OpenIDs associated with my global account.  I realize this would have been easier to do when I joined that site, but it's too late now, and only now have I realized that I don't really want that account showing up.  So can it be done by an administrator? I don't want to wait weeks and weeks for a response by using the contact form (funny, I've waited two with this post)...


I'm learning DES, but I have a question. When the plain text input, it gets a permutation by a table.  But, I don't know why 01 -> 58 / 02 -> 50. Is there any special rule or principle of it? or was it just set by the creator of DES?

I am creating a program in C language with DES (Data Encryption Standard) functionality, but don't know how to apply the initial permutation.   Is it achieved by swapping the values? If "yes", then how is the index of the original message created?


I have an auto-generated gravatar as my display on SO. I wish to associate that unique, but non-descriptive, gravatar in other places (such as github). I have grown rather fond of it. Is there anyway to do this? Do I have to go to  and actually sign up for an account?

Is there a name for the default avatars that are generated for users who do not assign one themselves? Not the avatar of the blank user, but the one made up of shards, shapes, and colours:      Is there an online generator for something like that? See also:


Every time I open a question, I open the message with "Hello", and end with "Thanks".  Too many times my messages get edited, and these lines are removed.  I've always wanted to know: why these words are not allowed?

I edit a lot of posts every day. I often run across posts with 'Hi' and 'Thanks' on the top and the bottom of the post respectively. I also run across things like:     --User   Should these items be removed during the editing of the post by an editor?


I have 3 Linux distributions on my machine (Ubuntu, Arch and Fedora). I allocated half the RAM size (3GB) as swap for each of them. (I have realized that having 3 distributions is not of much use to me, but I still have them.)   The problem is now the 3 distributions mount all the 3 swap partitions while loading, and treat swap as a single 9GB partition.   Now when I hibernate my system, obviously no distribution ever wakes up from hibernation.   Is there any way to overcome this?

In order to save disk space, I want to have two OS installations share a single swap partition (a dual-boot). Is this a good idea?


Let it be $$(1+x+x^2+x^3+x^4)^{496}=a_0+a_1x+a_2x^2+...+a_{1984}x^{1984}.$$ Find $$\gcd(a_3,a_8,...,a_{1983})$$ I know the Leibniz Theorem, so all coefficients are of the form $$\frac{496!}{a!b!c!d!e!}1^a\cdot x^b\cdot x^{2c}\cdot x^{3d}\cdot x^{4e}$$ and $a+b+c+d+e=496$, $a,b,c,d,e\in\mathbb N$ So, if $d$ is the $\gcd$ of these numbers, $$d\mid\sum_{i=3}^{1983}a_i,$$ but I couldn't found the value of $d$.  Can someone help me?  Thanks for attention!

Consider the expansion $$(1+x+x^2+x^3+x^4)^{496} = a_0+a_1x+\cdots+a_{1984}x^{1984}.$$   $\quad$ (a) Determine the greatest common divisor of the coefficients $a_3,a_8,a_{13},\ldots,a_{1983}$.      $\quad$ (b) Prove that $10^{340} < a_{992} < 10^{347}$.   Is there an easier way to solve this and is there a formula for the multisection for just the sum of the coefficients and not including $x^k$?  I thought of using the Multisection formula to prove (a). That is, $$\sum_{k \equiv r \pmod{m}}a_kx^k = \dfrac{1}{m} \sum_{s=0}^{m-1} \epsilon^{-rs} f(\epsilon^s x)$$ where $\epsilon$ is a primitive $m$th root of unity and $\displaystyle f(x) = (1+x+x^2+x^3+x^4)^{496}$.  Thus we have $r = 3, m = 5$ and so \begin{align*}\sum_{k \equiv 3 \pmod{5}}a_kx^k &= \frac{1}{5} \sum_{s=0}^{4} w^{-3s} (1+w^s x+(w^{s}x)^2+(w^{s} x)^3+(w^{s}x)^4)^{496}\\&=\dfrac{1}{5}\sum_{s=0}^4 w^{-3s}\left(\dfrac{(w^s x)^{5}-1}{w^s x-1}\right)^{496}\\&= \dfrac{1}{5}\sum_{s=0}^4 w^{-3s} \left(\dfrac{x^{5}-1}{w^s x-1}\right)^{496}.\end{align*}


This is just an easy question!  I want to lean some objective-c but the problem I don't have a mac I've only PC with windows  is there any compiler and editor where I can type my code and run it on windows.  Thanks in advance.

What would be the best way to write Objective-C on the Windows platform?  Cygwin and gcc? Is there a way I can somehow integrate this into Visual Studio?  Along those lines - are there any suggestions as to how to link in and use the Windows SDK for something like this. Its a different beast but I know I can write assembly and link in the Windows DLLs giving me accessibility to those calls but I don't know how to do this without googling and getting piecemeal directions.  Is anyone aware of a good online or book resource to do or explain these kinds of things?


I have a series of shape keys on a curve but the vertex interpolation between the morphing is no good. Is there a place in blender where I can view the animation paths of the vertices in the shape keys and fix up how the vertices interpolate so i can make it smoother.

I have animation where object changes his shape using shape keys, and I want to make some animation smoothing with graph editor. Is there a way to use graph editor for shape key animation?


$T(av_1 + bv_2) = aT(v_1) + bT(v_2)$  Why is this called linear? $f(x) =ax + b$, the simplest linear equation does not satisfy $f(x_1 + x_2) = f(x_1) + f(x_2)$.  Thank you.

I always thought linear functions need to satisfy $$f(x+y)=f(x)+f(y).$$ I am a tad confused now, consider $f(x)=2x+3$. $f(1)=5$, $f(2)=7$, $f(1+2)=f(3)=9 \neq f(1)+f(2)$ which was what I thought linear functions should satisfy.  Could someone clarify?


I'm working with Rmarkdown and my output is a pdf document. When reading the text, I noticed that so many words are printed incomplete such as "ar- rojan" and "progra- mación" (which should be "arrojan" and "programación"):      Los operadores <, >, <=, >=, == y != se denominan “lógicos” o “booleanos” porque nos ar-    rojan como resultado TRUE si se cumple la condición o comparación o FALSE en caso contrario.     Sin embargo, R, al igual que la mayoría de los lenguajes de progra-    mación distingue entre mayúsculas y minúsculas (“case sensitive”),   Based on my little experience with Rmarkdown, I guess in the YAML section I must include some option to prevent for incomplete words but I can't find any documentation related with my needs. This is my YAML:  --- title: "--" author: "" date: "--" output:   pdf_document:     latex_engine: xelatex mainfont: Times New Roman header-includes: - \usepackage{titling} - \pretitle{\begin{flushleft}\huge\bfseries} - \posttitle{\end{flushleft}} - \preauthor{\begin{flushleft}\Large} - \postauthor{\end{flushleft}} - \predate{\begin{flushleft}\large} - \postdate{\end{flushleft}} fontsize: 12pt urlcolor: blue linestretch: 1.15 ---   Thanks in advance for any suggestion or comment.

I can't find where I can remove any kind of hyphenation and just have LaTeX just do a line break.  edit: Honestly speaking I just don't like to read hyphenation anywhere and that's the only reason why I wanted to remove it. It is a matter of style, probably unexpected in LaTeX.  The document has only a summary in a different language and I used the language packages to hyphenate properly.


I wonder if it is theoretically achievable to produce living offspring between a human and a non-human primate. Great apes have 24 pairs of chromosomes compared to our 23, however, it is known that a mule is made from a donkey (62 chromosomes) and a horse (64  chromosomes). Are there other reasons why this human/non-human primate hybrid can't survive?

Since humans and apes share up to 99% of their DNA, can they interbreed? For example, a horse and a donkey seem to be just as distantly related and produce offspring. Mules, however, are sterile. Would ape-human interbreds be sterile?


I've been solving problems from my Galois Theory course, and at some point I sated that, given $p$ prime, $$\frac{X^p-1}{X-1} = X^{p-1}+X^{p-2}+\cdots+X+1$$ is irreducible in $\mathbb{Q}[X]$, because I felt I saw that in my course classes, but I'm not sure how can I prove or if it's even true. Is it really irreducible in $\mathbb{Q}[X]$ for any $p$ prime? If that's the case, how can I prove it? Any help will be appreciated, thanks in advance.

Can someone give me a hint how to the irreducibility of $X^{p-1} + \cdots + X+1$, where $p$ is a prime, in $\mathbb{Z}[X]$ ?    Our professor gave us already one, namely to substitute $X$ with $X+1$, but I couldn't make much of that.


I unenrolled from macOS Big Sur beta program, however I am still getting the 11.0.1 "update is available" notification. I would like to remove this so that I upgrade directly to 11.0 when GM is released. I don't want to install 11.0.1. Is there a way to delete cached update data so I only get 11.0 when it's eventually released?

My MacBookPro is currently running macOS Big Sur Version 11.0 Beta. Now that an official release for Big Sur has arrived, is it possible to move to the public release, just like a regular software update? In the "Software Update" settings, it still looks like I am suggested to install the new Beta version, rather than the official release. How should I fix this?


One of my teachers argued today that 0^0 = 1. However, WolframAlpha, intuition(?) and various other sources say otherwise... 0^0 doesn't really "mean" anything..  can anyone clear this up with some rigorous explanation?

Could someone provide me with a good explanation of why $0^0=1$?  My train of thought:  $x>0$  $0^x=0^{x-0}=0^x/0^0$, so  $0^0=0^x/0^x=\,?$  Possible answers:   $0^0\cdot0^x=1\cdot0^0$, so $0^0=1$ $0^0=0^x/0^x=0/0$, which is undefined   PS. I've read the  on mathforum.org, but it isn't clear to me.


While installing kodi I ran sudo add-apt-repository ppa:team-xbmc/ppa  and got this error : The repository 'https://deb.opera.com/opera-stable stable InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.  Tried some fixes from the suggestions. Went to Software and updates but I got this error. E:Read error - read (5: Input/output error), E:Read error - read (5: Input/output error), E:Read error - read (5:   These are my specs If they are helpful in any way. AMD Sempron(tm) Processor 3000+ Memory  2513MB Operating System    Ubuntu 18.04.4 LTS

So I keep trying to install things on my laptop and whenever I try to use sudo apt-get I get the same errors every  time,  SystemError: E:Read error - read (5: Input/output error), E:The package lists or status file could not be parsed or opened.   Also whenever I try to open software Center through my desktop Icon it will just freeze leaving me to force quit.  If I try to use the command software-center in my terminal I get the longest list in the world which is,   che.open() Traceback (most recent call last):   File "/usr/lib/python2.7/dist-packages/gi/overrides/GLib.py", line 629, in <lambda>     return (lambda data: callback(*data), user_data)   File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 261, in open     self._cache = apt.Cache(progress)   File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 105, in __init__     self.open(progress)   File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 150, in open     self._cache = apt_pkg.Cache(progress) SystemError: E:Read error - read (5: Input/output error), E:The package lists or status file could not be parsed or opened. 2013-10-13 10:13:52,685 - softwarecenter.db.pkginfo_impl.aptcache - INFO - aptcache.open() Traceback (most recent call last):   File "/usr/lib/python2.7/dist-packages/gi/overrides/GLib.py", line 629, in <lambda>     return (lambda data: callback(*data), user_data)   File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 261, in open     self._cache = apt.Cache(progress)   File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 105, in __init__     self.open(progress)   File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 150, in open     self._cache = apt_pkg.Cache(progress) SystemError: E:Read error - read (5: Input/output error), E:The package lists or status file could not be parsed or opened. 2013-10-13 10:13:57,365 - softwarecenter.db.pkginfo_impl.aptcache - INFO - aptcache.open() Traceback (most recent call last):   File "/usr/lib/python2.7/dist-packages/gi/overrides/GLib.py", line 629, in <lambda>     return (lambda data: callback(*data), user_data)   File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 261, in open     self._cache = apt.Cache(progress)   File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 105, in __init__     self.open(progress)   File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 150, in open     self._cache = apt_pkg.Cache(progress) SystemError: E:Read error - read (5: Input/output error), E:The package lists or status file could not be parsed or opened.   That's only about one-tenth of the list which is too long to read. I need help, if anyone has an answer please respond


A man taking the census walks up to the apartment of a mathematician and asks him if he has any children and how old they are.  The mathematician says: "${\it\mbox{I have three daughters and the product         of their ages  is 72}}$".     The man tells the mathematician that he needs more information, so         the mathematician tells him ${\it\mbox{"The sum of their ages is equal to         our apartment number"}}$.          The man still needs more information so the mathematician tells him              ${\it\mbox{"My oldest daughter has her own bed and the other two              share bunk beds"}}$.

Two old friends, Jack and Bill, meet after a long time. Jack: Hey, how are you man? Bill: Not bad, got married and I have three kids now. Jack: That’s awesome. How old are they? Bill: The product of their ages is 72 and the sum of their ages is the same as your birth date. Jack: Cool… But I still don’t know. Bill: My eldest kid just started taking piano lessons. Jack: Oh now I get it.  How old are Bill’s kids?  I am not able to figure out how Jack get it when Bill says "My eldest kid just started taking piano lessons"?


This is a MacBook Pro running macOS Mojave 10.14.6 with FileVault enabled.  In my case the problem is that at the login page, when the computer starts, the admin user account doesn't appear but after logging in as standard user I see that there is an admin. My brother who created the admin forgot the password.     I was thinking to press command + S when the Mac starts , in order to create a new admin, but with FileVault enabled single user mode does not work.   Is there still a possibility to recover the admin password?  My question is slightly different than those for which it was marked as duplicate because in those answers are explained:   Single User Mode(Command+S). As I have explained in my question, with  FileVault enabled single user mode does not work. Recovery Mode(Command+R) . When in the terminal, in recovery mode, I type  resetpassword I have not the possibility to choose the admin account but it's choosen standard account and i think that if I reset the password in this way  I will reset the standard user password and not the admin one.

On my mac I have 2 accounts and the both are normal account. So in this moment I don't have a Administrator account, only one that was in the past a administrator, but now is not.  How I can have again a Administrator account?


Consider the following elaborate scenario, which nevertheless actually occurred at our table. Two PCs, Sophie Sorcerer and Roger Rogue, sneak into the hideout of hapless villain Tarley Target. While hidden, Sophie uses her Subtle Casting metamagic to silently cast sleep, rendering Tarley unconscious without ever alerting him to the intrusion. Sophie and Roger swiftly exfiltrate the sleeping Tarley from the hideout to their camp nearby, where Sophie successfully casts charm person on him. When the sleep spell ends and Tarley awakes, Sophie takes advantage of Tarley's charmed condition: she dupes him into believing that someone else actually assaulted him, and that the PCs are in fact his saviors. Tarley, overcome with gratitude and having little cause to believe the PCs are really hostile, proceeds to spill his secrets. Once satisfied that she has squeezed every bit of useful information from Tarley, Sophie signals to Roger -- who has been quietly, nonchalantly moving into striking position -- to kill him. Initiative is rolled. Tarley is ruled surprised. Roger goes first, attacks, and misses. Does Tarley's charmed condition end? The description of  says a target that fails its save "is charmed by you until the spell ends or until you or your companions do anything harmful to it." Does an unsuccessful attack count as "harmful" for purposes of charm person? Would it make a difference if Tarley remained unaware of the attack -- e.g., because (as happened here) the DM ruled him distracted by Sophie's riveting conversation? Related questions:   asked what "harmful" means vis-à-vis charm person, but only in the context that the charmed condition restricts the charmed creature's ability to "target the charmer with harmful abilities or magical effects."  asked whether the target of charm person has to know who damaged them in order for the spell to end, but that presumes damage was actually dealt.

The  spell's duration can be ended by my companions doing anything harmful to the afflicted targets. What is considered harmful for the purpose of the spell's duration?     until the spell ends, or until you or your companions do anything   harmful to it.   In many places, the harm is defined when introduced as a term (see for examples: PHB 109; PHB 118; PHB 259). The harm here seems to be undefined, did I miss the definition here or on another page of the book?


Example:   /etc/bind/db.local file is created by apt package bind9 ( source:  ) but how to find a package which have created for example /usr/share/dns/root.hints?   I am looking for a universal solution to check any file path and the answer should be the package name (names if there is more then one) or reliable answer, that the file path was created by a user (i.e. not by apt install).

Say, I'm given a filename like libasound.so.2. Is there a way to query the package manager to correlate the filename with its corresponding package?  I'm interested to get answers for any package manager, but my primary focus is on apt and yum.


I was wondering where you bought that book (from)? Is 'from' necessary in this sentence ?

When someone purchase something from somewhere and I ask him the location of purchasing, which one is the correct question:     Where did you buy it?   OR     Where did you buy it from?   Is preposition necessary to use in this question or there is no need to use it?


If A and B are two n x n invertible matrices, would the matrix result from A+B be invertible?  I think it would because for a matrix to be invertible its determinant would have to be greater than 0, and if you add the determinants of two matrices greater than 0 you would have to get a non zero answer. But is there any way to prove this?

I can't find out if the product of two invertible matrix is an invertible matrix or if the sum of two invertible matrix is an invertible matrix.  Can anyone suggest an answer/counterexample?  Thanks a lot in advice


Suppose there is a group of $n$ people, and we need to choose exactly $k$ among them to give $k$ identical prizes. Also, exactly $a$ of these $n$ people are special. The problem is to calculate, how many ways are there to choose the $k$ people in such a way that, an odd number of special people are included in the choice? For example, if $n = 5,\ k = 3,\ a = 3$ then there are $4$ possible ways. WLOG, we assume that the first $3$ people $p_1,\ p_2,\ p_3$ are special. Then the possible ways are: $$ (p_1, p_2, p_3)\\ (p_1, p_4, p_5)\\ (p_2, p_4, p_5)\\ (p_3, p_4, p_5) $$ I know the solution to a similar problem where the constraint of odd special people are not present, so we can pick any number of people from the $a$ special ones and the remaining from the $n - a$ non-special ones. There is bijection argument which shows the answer is simply ${n \choose k}$. But I can't seem to find any way to adapt this solution for the above problem with the odd constraint.

How do I simplify: $$\sum_{r = 0}^{\lfloor \frac{k}{2} \rfloor} \dbinom{k}{2r} \cdot \dbinom{n-k}{k-2r}?$$ Basically, the sum is: $\dbinom{k}{0} \cdot \dbinom{n-k}{k} + \dbinom{k}{2} \cdot \dbinom{n-k}{k-2} + \dbinom{k}{4} \cdot \dbinom{n-k}{k-4} \cdots.$ This seems very similar to Vandermonde's Identity but because we skip two everytime instead of one, I don't see how I can apply it to this problem.


What is difference between 'string' and "string"?  For example, I use   alert('abc') and alert("abc")   document.getElementById('id') and document.getElementById("id")   I don't see any difference.

console.log("double"); vs. console.log('single'); I see more and more JavaScript libraries out there using single quotes when handling strings. What are the reasons to use one over the other? I thought they're pretty much interchangeable.


I periodically get this error on my phone. It will say the internal storage is running out but when I check the storage use it will say:  Total space 1.97 GB Available: 182MB Apps: 622 MB Cached 11.70 MB  This time, I checked my android/data folder and it said Spotify was using 1GB of space (in addition to all the space it is using in my other storage), so I deleted the Spotify cache and uninstalled it, then wiped my cache in recovery, but I didn't end up with any extra space afterwards.  I've deleted the log and LOST.DIR folders.   I can't seem to free up any more space. Every time this happens I have to factory reset and reinstall cyanogen (I'm running CM 10.1.3 now) to recover storage space, but each time it happens again eventually. I tried updating to a newer version of CM 10.1.3 but that doesn't help either.  UPDATE: I went through my apps to see if there was data I could get rid of there. I found 268MB in my Twitter app cache, but when I tried to clear the cache it wouldn't move. I uninstalled twitter but it didn't free up any storage space...  What am I doing wrong?  (Thanks!)

I have a Galaxy S2 running Android 4.1.2. It has a 12GB internal HD, and a 16GB SD card.  I keep getting errors from various programs telling me I am running out of space. BeyondPod won't download new episodes, Evernote keeps putting up a notification of a lack of space (even though it seems to be storing everything), and sometimes apps won't update.  I have tried to ensure I have no superfluous apps, and I haven't really changed the apps I use since I first ever started using the device. I keep any large files, like music collections or videos, on my SD card.  When I connect my device by USB to my Linux computer and check the properties of my 12GB HD, it says 9.9 GB is used. But if I browse the files, every folder seems to have barely kilobytes of information.   Why is my 12GB HD filling up, and how do I clear it out so I don't get these errors?  Update: My phone is rooted, so if that is something that can help me in this situaton, then root access is available to me.


When I try to update, I get this:   root@deepit-R405-A-CPD6A2:/var/lib/apt# sudo apt-get update E: Type '123443215' is not known on line 61 in source list /etc/apt/sources.list E: The list of sources could not be read.   Any idea what I can do?

Every once in a while I see users having issues to update due to errors like this:  E:Type 'ain' is not known on line 1 in source list /etc/apt/sources.list.d/some-ppa.list'   with varying types/line numbers/source list files (often after removing a PPA).  How can such an error be fixed?


My hopes aren't very high for this one but here's how my problem goes:  I am using an LG V10. Over the summer, its motherboard decided to die and it was replaced. Therefore the external SD card I used and encrypted on my old motherboard is now inaccessible :/ Is there any way to reach its contents?   If android devs really didn't come up with a way to decrypt an SD card on another device than the one its encrypted on, then there's no point in using encryption at all and maybe even no point in preferring android either..   Thanks for any help in advance

I encrypted both my phone and SD card upon purchasing my HTC Evo 4g LTE.  Recently the phone died (would get to the login screen and then reboot).  After a factory reset the SD card shows up as damaged.  I've tried mounting it in various ways, but neither the phone nor a computer will attempt to mount the drive - they just ask to format it.  Is there any hope of recovering the contents?


I have date strings in "Y-m" format. Day is irrelevant here. Now I need to create another date from these date strings wheere day should be either 1st or the last day of the month. I have tried this code:  $curDate = DateTime::createFromFormat('Y-m', $datestring1); $dt =  $curDate->format('Y-m-d');   The problem here is that it creates dates with the current day of the months. How can I force it to do it for the 1st or last day?   Thanks

I need to get the first and last day of a month in the format YYYY-MM-DD given only the month and year. Is there a good, easy way to do this?


I am into home brewing and one of the popular practices is for people to can wort - this is basically a sugary barley like tea- for growing yeast. A lot of people simply can wort in a pressure cooker or via normal steam canning methods, but after reading about the time variations necessary to can certain foods, and after failing to find a specific time recipe for wort even after emailing a government body asking for recommendations, I reached the conclusion that I did not need edible wort out of a can.  Instead I could just boil the wort once out of the can to kill any potential botulism toxin and still have the ability to portion large batches of wort into cans. The question is this: is there anything that won't be killed off in the boil that I need to worry about? After all, even though this is for yeast growth, I will end up drinking a small amount as it will end up in my beer.

Sometimes when preparing to eat canned goods, I realized that it has already expired. I am hesitant to throw it away because it may still be edible.  Question: Does cooking expired canned goods make them edible? Assume that it expired no more than one month ago. Some say yes, because it only affects the quality of the product. Some says no, because it is very dangerous and not worth risking.  I want to hear this from experts. :)


Funding and financial management sometimes (remains or remain) difficult.  Can you please tell me wich one is correct and why?

Possible Duplicate:          Would I use is or are in the following sentence?      The Pohutakawa Coast, Hauraki Gulf, and Waiheke Island is/are the backdrop for our day.   If I rewrote it so the subject (backdrop) starts the sentence, then it seems to me that as it is singular, the verb should be the singular is. But as it is written above, are seems less clumsy.


I love using Hot Corners, but I regularly trigger them by mistake when performing other tasks, so I disabled them for a while and found I couldn’t live without this functionality.  This got me to thinking - what if I could set a delay (0.5 secs) before the Hot Corners get triggered, or maybe set it so it’s triggered by a right-click action?  I had a look at the Mission Control system preferences but didn’t see any way to do this instead of just accidentally moving the mouse..   Can I do this? Maybe a terminal command? Other suggestions welcome too.

I like the concept of hot corner actions but the trigger time for hot corner actions is too quick for me to make good use of them. I keep tripping my corner actions accidentally while reaching for objects in that general vicinity of the corner.  Is it possible to extend the trigger time for hot corner actions? So I have to hover in the corner for at least a second or two before the hot corner action triggers?


With the patch 2.0.1, you no longer can improve your MF with Paragon Level or Nephalem Valor buff.  So is there a way to improve that stats without raising the difficulty level or playing in coop ?

What should I wear to maximize my Magic Find? What specific items are ideal for a Magic Find-optimized build? Does any one particular class have better class-specific items with increased Magic Find?


I was thinking about the sentence "Could I Have This Kiss Forever" after listening the song "Could I Have This Kiss Forever" by Enrique Iglesias.  And I'm confused is this sentence gives a same meaning like "Can I Have This Kiss Forever". If not what is the difference between "Could I Have This Kiss Forever" and "Can I Have This Kiss Forever"?  Someone may think this question as a duplicate one, but I didn't find answer for my question by another question. Edit: At most questions about Could/Can they give some idea about Could/Can but not about the meaning difference of the above sentences.

Can you please explain this to me?          Could you please explain this to me?   I am unable to figure out which to use which situation. I did google, and some posts say they are both the same, even if the second one is more formal. Other posts say could is the past tense of can, but in the above example, I don't think could is used as past tense of can.  What is correct way to use these words?


I have a query related to a transformation of variables question; the images of which I have attached here.  I have solved the question almost, but there seems to be a problem with the distribution that I have derived in the last line of the solution.  I would greatly appreciate any kind of help. Thanks in advance.  N.B.: In the question, $U$ should follow $N(\mu = 0, \sigma^2 = \frac{1}{4} = 0.25)$.

I am trying to prove the statement:  If $X\sim\mathcal{N}(0,\sigma_1^2)$ and $Y\sim\mathcal{N}(0,\sigma_2^2)$ are independent random variables, then $\frac{XY}{\sqrt{X^2+Y^2}}$ is also a Normal random variable.  For the special case $\sigma_1=\sigma_2=\sigma$ (say), we have the well-known result that $\frac{XY}{\sqrt{X^2+Y^2}}\sim\mathcal{N}\left(0,\frac{\sigma^2}{4}\right)$ whenever $X$ and $Y$ are independent $\mathcal{N}(0,\sigma^2)$ variables. In fact, it is more generally known that $\frac{XY}{\sqrt{X^2+Y^2}},\frac{X^2-Y^2}{2\sqrt{X^2+Y^2}}$ are independent $\mathcal{N}\left(0,\frac{\sigma^2}{4}\right)$ variables. A proof of the last result follows by using the transformation $(X,Y)\to(R,\Theta)\to(U,V)$ where $x=r\cos\theta,y=r\sin\theta$ and $u=\frac{r}{2}\sin(2\theta),v=\frac{r}{2}\cos(2\theta)$. Indeed, here $U=\frac{XY}{\sqrt{X^2+Y^2}}$ and $V=\frac{X^2-Y^2}{2\sqrt{X^2+Y^2}}$. I tried to imitate this proof for the problem at hand but it appears to get messy. If I haven't made any error, then for $(u,v)\in\mathbb{R}^2$ I end up with the joint density of $(U,V)$ as $$f_{U,V}(u,v)=\frac{2}{\sigma_1\sigma_2\pi}\exp\left[-\sqrt{u^2+v^2}\left(\frac{\sqrt{u^2+v^2}+v}{\sigma_1^2}+\frac{\sqrt{u^2+v^2}-v}{\sigma_2^2}\right)\right]$$ I have the multiplier $2$ above as the transformation is not one-to-one. So density of $U$ would be given by $\displaystyle \int_{\mathbb{R}}f_{U,V}(u,v)\,\mathrm{d}v$, which isn't readily evaluated. Now I am interested to know if there is a proof where I can only work with $U$ and don't have to consider some $V$ to show that $U$ is Normal. Finding the CDF of $U$ doesn't look so promising to me at the moment. I would also like to do the same for the case $\sigma_1=\sigma_2=\sigma$. That is, if $X$ and $Y$ are independent $\mathcal{N}(0,\sigma^2)$ variables then I wish to show that $Z=\frac{2XY}{\sqrt{X^2+Y^2}}\sim\mathcal{N}(0,\sigma^2)$ without using a change of variables. If somehow I can argue that $Z\stackrel{d}{=}X$, then I'm done. So two questions here, the general case and then the particular case. Related posts on Math.S.E: . . Edit. This problem is in fact due to L. Shepp as I found out in the exercises of An Introduction to Probability Theory and Its Applications (Vol. II) by Feller, alongwith a possible hint:  Surely, $U=\frac{XY}{\sqrt{X^2+Y^2}}=\frac{1}{\sqrt{\frac{1}{X^2}+\frac{1}{Y^2}}}$ and I have the density of $\frac{1}{X^2}$ at hand. Let's see what I could do now. Apart from this, a little help with the integral above is also welcome.


I am an Indian Citizen and Canadian PR holder. Want to book the flight from YYZ ( wow airline) have a route through Iceland (6.55 hours hold) to New-Delhi. Do I require Iceland Visa or Transit Visa?   My outward flight is:     Fri, Jan 11, 2019 Toronto (YYZ) 06:00PM New Delhi (DEL) 03:15 AM + 2   day      Flight 1: | 5h 45m | WW214 | Operated by: WOW air Layover: 6h 55m   | Reykjavik (KEF)      Flight 2: | 10h 5m | WW322 | Operated by: WOW air   And return flight is:     Wed, Jan 30, 2019 New Delhi (DEL) 07:00 AMToronto (YYZ) 05:00 PM      Flight 1: | 11h 50m | WW323 | Operated by: WOW air Layover: 2h 10m |   Reykjavik (KEF)      Flight 2: | 6h 30m | WW213 | Operated by: WOW air

I found many related questions on this site but I am still not sure about the rules. How can I decide if I need a visa to transit? Schengen members as of May 2021 are as follows:  Austria Belgium Czech Republic Denmark (excluding Greenland and the Faroe Islands - but an open border with the Schengen Area is maintained) Estonia Finland France (excluding overseas departments and collectivities) Germany Greece Hungary Iceland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands (excluding Aruba, Curaçao, Sint Maarten and the Caribbean Netherlands) Norway (excluding Svalbard) Poland Portugal Slovakia Slovenia Spain (except Ceuta and Melilla) Sweden Switzerland


He knows a thing or two about being a doctor: study, study, study!   Is this "being" the same as "becoming?"  And why?

I am not good at English. And I used to say that I want to become a software developer. But Some people are using that I want to be a [something]. Which one is correct? And at what situations we should use which one? I read in many websites. Answers I have found so far are  Be is abbreviation of become. Both are same. Be is representing continuous thing. Become represents future.  I can't understand it because of people usage. Could anyone please further explain the difference between these two?


Does anybody know what package shall I download or what to do to open .MDI files on Ubuntu 13.10?  MDI: Microsoft Document Imaging Format

I have some insurance files that I need to be able to view, but they are in the MDI format I can't get them to work at all in Ubuntu.  I've searched the entire forum and I've even installed Microsoft office 2003 & 2007 through Wine, but it still doesn't work correctly.   The only solutions posted in the forum have suggested getting an MDI to pdf converter or installing MS office.  I haven't gotten any of this to work.  How can I view or convert MDI files?


Hi I am trying to read a CSV File called test.csv in JAVA . Below is my code :   import java.io.BufferedReader; import java.io.FileReader;  public class InsertValuesIntoTestDb {      @SuppressWarnings("rawtypes")     public static void main(String[] args) throws Exception {                 String splitBy = ",";         BufferedReader br = new BufferedReader(new FileReader("test.csv"));         String line = br.readLine();         while(line!=null){              String[] b = line.split(splitBy);              System.out.println(b[0]);         }         br.close();    } }   This is my CSV File (test.csv):  a,f,w,b,numinst,af,ub 1RW,800,64,22,1,48:2,true 1RW,800,16,39,1,48:2,true 1RW,800,640,330,1,48:2,true 1RW,800,40,124,1,48:2,true 1RW,800,32,104,1,48:2,true 1RW,800,8,104,1,48:2,true 1R1W,800,65536,39,1,96:96,true 1R1W,800,2048,39,1,96:96,true 1R1W,800,8192,39,1,48:48,true   I am trying to print the first column in the csv ,but the output I get is only a in an infinite loop . Can anyone please help me fix this code to print the entire first column. Thanks.

Can anyone recommend a simple API that will allow me to use read a CSV input file, do some simple transformations, and then write it.  A quick google has found  which looks promising.  I just wanted to check what others are using before I couple myself to this API.


I have a 600EX-RT Canon flash, and am looking for a cheap Yongnuo flash to be used as a slave to the Canon. Do you know any Yongnuo than can reliably be used as a slave to my 600EXRT ?

My current flash setup is a standard shoe mount but I've been thinking about getting a remote.  I've been drooling over the Speedlite 600EX-RT. It uses radio to control slaves, which is nice (longer distance, doesn't require line of sight, etc.).  One thing I don't understand: do slaves also have to be 600EX-RTs or do other flash units use radio to communicate already? Can any (cheap?) flash slaves can be used with a Canon Speedlite 600EX-RT or do I need to buy the 600EX and a ST-E3-RT transmitter in order (or multiple 600EX-RTs) to have a radio-controlled remote flash setup?


I've been reading SO discussion on how output going to a terminal is line buffered, and output to pipes or files etc is usually "block buffered". I am trying the following two pipelines on OSX, which aim to prepend a timestamp to the incoming lines:  while [ 1 ] ; do echo $RANDOM && sleep .5 ; done | ~/bin/prepend_ts_python    and  while [ 1 ] ; do echo $RANDOM && sleep .5 ; done | ~/bin/prepend_ts_perl   The Perl program is (and I don't know much about Perl):  #!/usr/bin/perl  while ( <> ) {     print scalar(localtime()), " ";     print; }   The Python program (clearly not prepending a timestamp yet) is:  #!/usr/bin/python  import sys  for line in sys.stdin:     print("foo")   The pipeline using the Perl version prints output immediately, as desired, whereas the Python one outputs intermittently.  I was under the impression that any buffering that was going on was being determined by the while/echo loop, and for this reason people were recommending using the unbuffer command on the beginning of the pipeline.  Does Perl have some way of flushing its STDIN? I didn't think it could reach "backwards" in the pipeline. Why are they different?

Is output buffering enabled by default in Python's interpreter for sys.stdout?  If the answer is positive, what are all the ways to disable it?  Suggestions so far:   Use the -u command line switch Wrap sys.stdout in an object that flushes after every write Set PYTHONUNBUFFERED env var sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)   Is there any other way to set some global flag in sys/sys.stdout programmatically during execution?


It seems that if I were to just express interest in a single subdiscipline (computer networking for example), and none of the networking professors are taking on students, I would not be considered based on any other merits my application may have. But if I were to express interest in several subdisciplines it may be difficult to create a structured statement of purpose.

I am wondering how many research interest should be included in a statement of purpose. Is it better to include just one core interest or to include up to three as in my case?


When anonymous users go to /user, i would like to show the registration form instead of the login form, or just redirect to /user/register. I couldn't find anywhere how to do that...

Is it possible to redirect anonymous user to user/register page? How can I do that?


How do I run a script as sudo at boot time?  I need to run ethtool --offload <net> rx off to disable the annoying jme udp checksum error message.

I had a script that automatically enables my wifi without using networkmanager, but I don't know how to run the script as root while the system is booting. How do I make the script run automatically during boot?


Let $n \in \mathbb{N}$, let $A \in \mathbb{R}^{n \times n}$      True or false? The linear system of equations for $Ax=b$ is uniquely   solvable for every $b \in \mathbb{R}^{n}$ if and only if   $\text{det(A)} \neq$ 0   I think the statement is true. Making $\text{det(A)} \neq 0$ should avoid us getting non-unique results such as $0=0$.  Remebering this and knowing $\text{det(A)} \neq 0$ gives linearly independent vectors, we can only get unique solution.  Edit: We don't know anything about $x$. If $x \neq 0$, then the statement will be true, right?    Please correct me if I'm wrong / unclear, these tasks will be asked in my exam and I want pass it :)

I know there's a theorem in linear algebra that has a list of statements that are equivalent, as follows:   $\det(A) \ne 0$ $Ax = 0$ has only the trivial solution $Ax = b$ is consistent for every matrix $b$ $Ax = b$ has exactly one solution for every $n \times 1$ matrix $b$   (and several other which I do not need for the question that I'd like to ask).  So we've been learning about linear independence, span and bases, and I was wondering the following:  Is statement 2 the same as saying a set of vectors are linearly independent?  Is statement 3 the same as saying the set of vectors span a vector space? (Meaning that every single vector $b$ in the vector space can be made from some combination of $Ax$, where $A$ would represent that vectors and $x$ would be all of the scalar multiples of the vectors?  Is statement 4 the same as saying the set of vectors is a basis? (since that one solution must be the trivial solution, it must be linearly independent, and since it is consistent for every $b$, it spans the vector space?)  It seems pretty obvious that it's all related to each other, but I'm just wondering if they're all exactly the same.


To have the best quality of figures in my document I'm using pdf images. But it seems that when the pdf images have very thin and/or transparent lines the final figure in the pdf gets messy, basically the lines get thicker and darker, unless the pdf is fully zoomed. This effect can be seen in the pictures below.  Does anyone know the root cause of this and how to fix it?  EDIT: And note the inconsistency in the thickness of the lines in the zoomed out version. While the zoomed in version all lines are the same thickness, as in the original image.  Zoomed out figure:    Zoomed in figure:

I use PCTEX 5.1. When I print from a DVI window my embedded graphics line plots are too thin and almost fade out. When I export the document to a PDF and print it the graphics line weights are much better; however, the PDF driver actually makes every second page, text and graphics, is a little lighter. The dvi driver doesn't do that. So first, can I get the dvi driver to increase the graphics line weights, and second is there a patch for the PCTEX PDF driver problem.


In sentences like, "I'm dying to get to you and "I'm learning to live again" and "i was preparing to go for surgery when you called" what are "dying", "learning" and "preparing" functioning as? Are they verb(ing) or are they gerunds.

Progressive forms of verbs consist of the form to be + participle. At least that is what most English grammars say or they are imprecise and speak of the -ing form. My question is what follows after the forms of to be?       I'm working in the garden.   Is working here a present participle or rather a gerund? I asked myself this question long after I had left school, simply because one accepts what grammar books say without much reflection. But the longer I think about this problem, the more I tend to see it as a gerund.    I stumbled upon this through a curious way of speaking in German dialects. Normally we don't use progressive forms in German, but some dialects make extensive use of forms such as   Ich bin am Aufräumen - word-for-word translation: “I'm at tidying up”.   Normally in English a preposition such as in "at tidying up" is omitted and it becomes:   I'm tidying up.   On another forum, a German language one, we noted the German dialects that made extensive use of such forms as beim/am Aufräumen—and we discovered that these forms are used extensively in areas along the River Rhine from Switzerland to the north, but  also in the east of Germany and in the south.  So it is reasonable to ask what form is used in English, participle or gerund? In German it is a gerund, a participle would be unusual. So it might be the same in English, but since participles and gerunds have the same form, it is really difficult to decide which form it is.  I derive the progressive forms from a formula with "in the act of doing":   I'm working in the garden means “I'm in the act of working in the garden.”         When you omit "in the act of" you get the normal progressive form.     I forgot to mention that the following archaic form also exist       We were ahunting / went ahunting     where one may assume that the prefix a- is a relic of a preposition.


Take this code snippet for example: a = [] for x in range(2):     a.append(lambda: print(x)) print(a[0](), a[1]())  The output is: 1 1  But I expected it to be 0 1  How do I fix this?

I want to create a list of lambda objects from a list of constants in Python; for instance:  listOfNumbers = [1,2,3,4,5] square = lambda x: x * x listOfLambdas = [lambda: square(i) for i in listOfNumbers]   This will create a list of lambda objects, however, when I run them:  for f in listOfLambdas:     print f(),   I would expect that it would print  1 4 9 16 25   Instead, it prints:  25 25 25 25 25   It seems as though the lambdas have all been given the wrong parameter. Have I done something wrong, and is there a way to fix it? I'm in Python 2.4 I think.  EDIT: a bit more of trying things and such came up with this:  listOfLambdas = [] for num in listOfNumbers:     action = lambda: square(num)     listOfLambdas.append(action)     print action()   Prints the expected squares from 1 to 25, but then using the earlier print statement:  for f in listOfLambdas:     print f(),   still gives me all 25s. How did the existing lambda objects change between those two print calls?  Related question:


Does there exists a nontrivial positive integer solution with $x\ne y,$ of $$x^4+y^4=2z^2.$$

I would like to know any way of solving the diophantine equation $x^4+y^4=2z^2$. Or ideas that seem worth trying out.  By solving I mean fining all solutions and proving there are no more.  Keith Conrad showed how to reduce this equation to a different one which was solved by Fermat in his notes about Fermat descent, other than I have no ideas how to solve it. I tried to do descent on it directly but that seems completely impossible so I am interested in other techniques. Thanks very much.


I have a question with regards to lagrange multiplers. The question is as follows: Find the points on the sphere x^2+y^2+z^2=4 that are closest to and farthest from the point (3,1,-1). Now, it is clear to me that the distance from any point to (3,1,-1) is simply using the R^3 metric, d=$$\sqrt((x-3)^2+(y-1)^2+(z+1)^2$$ and I can make the algebra easier by considering $$d^2$$. However, my question is as follows: How can I be sure that the maximum or minimum occurs when  $$\nabla(d^2(x,y,z))=\lambda\nabla(g(x,y,z))$$ where $$g(x,y,z)=x^2+y^2+z^2$$? I would like an explanation in terms of tangent and normal spaces please? As i'm unable to find one.  Furthermore, it is to my knowledge that the lagrange multiplier works when the contours of the function f(x,y) just touches the constraint g(x,y)=c. However, is it possible to have contours of f(x,y) where the contours increase and decrease and wouldn't then the lagrange multiplier not work?

I know that the Lagrange multiplier method helps us evaluate critical points of $f$ on the closed boundary of the restriction.   In other words we solve:$$\nabla f=\lambda \nabla g$$  But why does this method actually work? Can someone please give me an explanation. Thank you!


I want to run a bash script in a directory /media/aliakbar/New Volume(internal drive)/further/path/to/file . The problem is: with chmod +x the file's permission is not changed (proof: I couldn't execute script from terminal):  -rw------- 1 aliakbar aliakbar    561 Jun  8 14:05 buildscript_0.10.0.sh   I moved the file to /home/<user>/Downloads/, did chmod +x which worked, and moved file back to /media/aliakbar/New Volume(internal drive)/further/path/to/file, replaced non-executable file but still with ls -l there's no change!?  NOTE: I'm on Ubuntu LTS 14.04 (dualboot) with df -T run in file directory returning:  /dev/sda3   fuseblk   277228568   168883892   108344676   61%   /media/aliakbar/New Volume    New Volume is on an internal drive unfortunately I don't know how it's mounted, I have only an empty /etc/fstab.d/ folder   What am I doing wrong?

sorry fresh user. I installed about 9 days ago and had issues with Unity disappearing which took 5 days of headaches to fix. It never did fix, I reinstalled.   I set up Plex (media server) and while the server is running and can be accessed by external network devices, I can't add files. Plex says this is because of permissions. I have gone up and down the forums here and at Plex to get an answer. It seems everyone says   chmod -R 755 /media/My\ Book/Videos   will change permissions to allow the folder "Videos" on my external USB 2.0 NTFS 3TB Western Digital drive (which is mounted and accessible through the file manager) as well as every sub-directory and file contained therein to be accessible to user "Plex".  I have used file manager and as soon as you click to change permissions it changes right back. When I chmod with -c it tells me every file is changed (usually 600) to 755 as I commanded it to do. I did   ls -l   to verify and there is no change. (I also used ls -l to make sure I knew who the owner was and it is me (mvl1014). ls -al gives me the same info.)  I swear to god I tried to sudo it and after smashing my head against this keyboard for basically the entirety of my day, I tried it as root. I was scared shi-less but couldn't come up with anything else. sudo su to root and then chmod -R -c /media/My\ Book/Videos  Same result. -c told me every single file was changed and a check in Unity or in terminal confirmed not a darn thing changed.  Now it seems to me that even if that isn't the thing stopping Plex from working there is still a problem with this command not going through.  12.04LTS -- on gen 1 i7 (2.7 GHz I believe) with 6 GB ram   I've attempted to attach a screenshot but I'm told I need 10 reps to do so, which means I'm copy/pasting too.  Please excuse my obfuscation, but Lorem Ipsum seemed unnecessary. And I tried multiple ways to format this but it looks perfect every way and messed up each time in the preview below. (Ugh, I'm a mess.)  $ chmod -R -c 755 /media/My\ Book/Videos  .....  .....  .....  mode of `/media/My Book/Videos/xxxx/xxxx/xxxx.mkv' changed from 0600 (rw-------) to 0755 (rwxr-xr-x)    ls -al shows:  mvl1014@FX6800:/media/My Book/Videos$ ls -al   total 88  drwx------ 1 mvl1014 mvl1014     0 Aug 28 15:17 .   drwx------ 1 mvl1014 mvl1014 20480 Sep  3 14:29 ..  drwx------ 1 mvl1014 mvl1014  8192 Aug 28 15:18 xxxx drwx------ 1 mvl1014 mvl1014 49152 Aug 16 14:02 xxxx drwx------ 1 mvl1014 mvl1014  8192 Aug 27 21:36 xxxx drwx------ 1 mvl1014 mvl1014  4096 Jul 23 19:09 xxxx   I apologize if this has been asked. I looked through this place plus at all the suggested "Similar Questions". The closet thing I got to an answer , but running the provided code with my own UID didn't work either.


I remember a time when anonymous users could post questions without an account on Stack Overflow. , this is no longer possible.  I don't mind the removal. I DO, however, find it interesting that it was built and then removed. What was the rationale? Are there any blog posts talking about it? Are there any stories from the trenches that lead to the decision?  Why did Stack Overflow drop anonymous content?  I ask because I'm faced with a similar situation and tested wisdom is interesting.  (Again, I don't want this to be a feature debate, but rather a historical recounting).

I know SO's policy is "you don't have to register to ask questions," but there are so many new members and so many hit-and-runs... The majority of the questions I see now are coming from new users (i.e., it's their first question). Although unregistered users should still be able to ask questions, I think we should encourage users to create an account. Here is a couple of ways we could do that:  Explicitly encourage people to get an account: there's currently nothing telling people to do that. Maybe tell people something like "Get an account, it's easy!" and maybe show some of the perks of having an account (and having rep).  Maybe give a few bonus points for registering; and have that enable a basic privilege. It could be taken from one of the , for example.   Of course getting people to register is just half of the battle. I don't know what the stats are on this, but I think there's a number of users who create multiple accounts anyways. We could curb that by:  Having smart(er)? duplicate account detection systems, alerting someone who is about to create a new account and possibly has an account already. Give them a message like "Hey, it looks like you already have  account, are you sure you want to create a new one?"  Create a new privilege (10k? 20k?) that gives users tools to detect possible duplicate accounts, eg: "List users with the same e-mail," "List users with the same IP addresses,"  etc. (without revealing said emails and IPs). Then the 10k/20k can look at other stuff (e.g.: posts) and refer the new user to a moderator for a possible merge.


Can we just say that if between 2 points in some given circuit, there's no load, then the potential at those 2 points are same?

I understand all the concepts of what voltage is using all the analogies but some things related to the drop of voltage across a circuit confuses me.   If I had a short circuit and attached a voltmeter I would get a potential difference reading of 0 volts. How is current then going through the wire if it is 'X' volts at any point in the wire? Let's say I have a DC 9V battery with a load in the middle. I read somewhere (probably mistaken here) that the voltage drop in this situation must be 9V or rather, that the sum of load resistances must be equal to voltage of the source. I mean, there is a variable amount of resistance to each load so at the base of the load I might have 9V and at the end of the load I might have 5V with a 4V potential difference.


I recently had one question put on "Hold" on Stack Overflow and was really sad, shocked and confused. It turns out that I modified my question, another user also improved it a lot and it was reopened.   But I'm still amazed and disturbed by the fact that I cannot ask question like "What is the best...".  This type of question has some negatives:   Create emotional reactions Attracts spams Attracts non objective answers, sometimes by creators of products/software Could lead to inappropriate exchange/words Generate lots of unnecessary information It is subjective   But these kinds of questions also have their positives:   It create debate where lots of useful information came out Brings new information that could lead to change some minds / a new vision to readers In most case, those questions lead to a solution that will save a lot more time than any other kind of question In most case, those questions lead to a solution that will save a lot more of money than any other kind of question (usually related to products) Brings creator reaction that would bring additional useful information on the product, reason of certain design decision, ...   In summary:  Considering the negatives and the positives, and also considering that Stack Overflow has a really good system for rewarding/penalizing users, I think that the acceptance of this type of questions would be a lot more beneficial for users than anything else. It is only because Stack Overflow has this rewarding system that it could support those type of questions easily whithout too much drawbacks. Also, Stack Overflow has the best reputation and is recognized as the best question/answer system now for programmers (it is subjective I know, but don't be blind, be honest and admit it), then I think that it returns to Stack Exchange to offer that type of question for the benefits of everyone.  If Stack Overflow does not support this type of question, what can we do? Where can we go to have lots and good reactions to this type of questions? Who will do it?

I needed to find a good Perl module to do HTML parsing.  The good thing about Perl is the CPAN (module library) with gazillions of modules to do everything, the bad thing is that it's hard to find the right module.  So I though, let's ask Stack Overflow: “What is a good Modern Perl way to parse HTML documents?”  I quickly got one great answer and several good comments.  I would have gotten at least one more good answer, but then the question was put on hold because it's “subjective”, and it couldn't be added anymore.  In spite of protests, it was then closed and later deleted.  I've got the answers that I needed, but now other people will be deprived of this useful information.  Is it really so important to stick to the rules that this question had to be removed? Yes, it's subjective.  By definition.  I want people's opinions about what module I should use, after all. The question got 8 plus-votes and 2 minus-votes, so others thought it was useful too.  The URL was  , but I think it only works when logged in as me.  Do I need to start looking for another site to ask such questions?  If so, too bad, I really liked Stack Overflow until now.


I upgraded from 14.04 which had Gnome DE. My Grub is black in colour since then. I am hoping to reinstall Grub to match with Unity I have now. I do not have any other DE s for now. Does reinstalling Grub give me stock 16.04 ? If yes, give me the commands, please.  Update :  Reinstalling Grub has no effect on Gnome-ish black elements while booting, sadly.  Update 1 :  I am not looking to change colour. I tried reinstalling Grub to remove Gnome-ish elements and get dotted boot screen by Ubuntu during start up and shutdown.

I use  the latest version of Grub Customizer (3.0.2) and Ubuntu 12.04. On appearance settings I changed the background image and the font, but once I reboot the system they don't appear; there's always the default Ubuntu background image and the font seems a bit changed but not as expected. I tried to resize and crop the image as described here:  but it doesn't work in any case. On /etc/default/grub: # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. # For full documentation of the options in this file, see: #   info -f grub -n 'Simple configuration'  GRUB_DEFAULT="0" #GRUB_HIDDEN_TIMEOUT="0" GRUB_HIDDEN_TIMEOUT_QUIET="true" GRUB_TIMEOUT="10" GRUB_DISTRIBUTOR="`lsb_release -i -s 2> /dev/null || echo Debian`" GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" GRUB_CMDLINE_LINUX=""  # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"  # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL="console"  # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' #GRUB_GFXMODE="640x480x15"  # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID="true"  # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_RECOVERY="true"  # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1"  export GRUB_MENU_PICTURE="/home/attilio/Immagini/grub/1366.jpg" export GRUB_COLOR_NORMAL="white/black" export GRUB_COLOR_HIGHLIGHT="light-cyan/black" GRUB_FONT="/boot/grub/unicode.pf2"  Thank you very much in advance.


I have a list of integer  a=[1,2,3,4,5,6,7,8,9]  and i must create a string with the integers separated by spaces and every five number i must add a '\n'  string='1 2 3 4 5\n6 7 8 9\n\n'    I have tried with a join like that:  string=' '.join(a)  but i don't know how to add '\n' with a condition.

I have a list of arbitrary length, and I need to split it up into equal size chunks and operate on it. There are some obvious ways to do this, like keeping a counter and two lists, and when the second list fills up, add it to the first list and empty the second list for the next round of data, but this is potentially extremely expensive.  I was wondering if anyone had a good solution to this for lists of any length, e.g. using generators.  I was looking for something useful in itertools but I couldn't find anything obviously useful. Might've missed it, though.  Related question:


I'm trying to install ulsy in order to use its blitz symbols for proofs by contradiction.  I downloaded the metafont source from CTAN:   I then unzipped it in texmf/tex/latex  I ran latex ulsy.ins and latex ulsy.dtx and produced the .sty file.  At this point, the compiler was able to find the .sty file but produced an error message saying that it could not find the .tfm file.  Somme other answers suggested that this problem could be resolved by installing the following:    texlive-latex-recommended  texlive-latex-extra  texlive-fonts-recommended  However, this did not work for me.    I then tried moving the .tfm file to texmf/fonts/tfm/public/ulsy and the .mf file to texmf/fonts/source/ulsy  Now when I try to use the symbols in math mode, I just get arbitrary greek letters, but my understanding is that ulsy's symbols are supposed to be used in text mode anyway.  Unfortunately, I am getting the following error message when I try to use ulsy's symbols in text mode:     !pdfTeX error: pdflatex (file ulsy10): Font ulsy10 at 600 not found    ==> Fatal error occurred, no output PDF file produced!      kpathsea: Running mktexpk --mfmode / --bdpi 600 --mag 1+0/600 --dpi 600 ulsy10      mktexpk: don't know how to create bitmap font for ulsy10.      mktexpk: perhaps ulsy10 is missing from the map file.      kpathsea: Appending font creation commands to missfont.log.      pandoc: Error producing PDF from TeX source      Error: pandoc document conversion failed with error 43      Execution halted   Can anyone point me in the right direction or guide me through the manual installation?

Frequently there are questions about, how to manually install a font, what very often means “Type1 font”. So I thought, we should write a general answer about the several aspects to regard.  Beside the usual approach for  it seems, that for fonts further steps are necessary. What are these steps? Or better:  How to manually install fonts and their associated support files in TeX distributions?


True or false: There exists a continuous function  $f: \Bbb R \to \Bbb R$ such that $f(\Bbb Q) \subseteq {\Bbb R}\setminus {\Bbb Q}$ and $f({\Bbb R}\setminus {\Bbb Q}) \subseteq {\Bbb Q}$.  My attempt: I was trying to use the sequential definition of continuity. Consider $a \in \Bbb R$ then we have a seqn ${x_n}$ of rational numbers converging to $a$ and we have a seqn ${y_n}$ of irrational numbers converging to $a$. Then what will be $f(a)$?  I was thinking that in one way $f(a) \in \Bbb Q$ and on the other way $ f(a) \in {\Bbb R}\setminus {\Bbb Q}$ . But I am wrong $\{f(x_n)\} \subseteq {\Bbb R}\setminus {\Bbb Q}$ and $\{f(y_n)\} \subseteq {\Bbb Q}$ still $f(a)$ can be anywhere.   Is there any way to fix my attempt or any other possible idea?

Is there a way to prove the following result using connectedness?  Result:  Let $J=\mathbb{R} \setminus \mathbb{Q}$ denote the set of irrational numbers. There is no continuous map $f: \mathbb{R} \rightarrow \mathbb{R}$ such that $f(\mathbb{Q}) \subseteq J$ and $f(J) \subseteq \mathbb{Q}$.


If a rock is thrown at someone's head, or a car drives against a wall, or a meteor hits a planet, is the physical damage done to the object proportional to the projectile's momentum, or to its kinetic energy? (assume that the target object is at rest in the reference frame).  I'm sure that it depends on all kinds of factors, but roughly, does it depend linearly on the projectile's speed (as momentum does), or quadratically (as kinetic energy does).

Let's assume we have 2 bullets. The first bullet has $450$ $J$ of KE and $3$ $kg.m/s$ of momentum, while the second bullet has $250$ $J$ of KE and $5$ $kg.m/s$. Now if they are both shot at ballistic gelatin, which one is expected to cause more damage if both are stopped by the gelatin? By damage here I mean more penetration, bigger cavity, heat and any other deformation of the gelatin.    In other words, if the velocity of a projectile is doubled, will the amount of damage it causes when it collides with an object double or quadruple?


American tourist here. I understand the 180 day scheme, 90 days in (non-consecutive), 90 days out (consecutive).   Here’s the question: I enter the Schengen area on Jan 1st and leave the Schengen area on Jan 31st (30 days) leaving me 60 Schengen days unused. Can I wait outside the Schengen for an extended amount of time, say 5 or 6 months, and then arrive in the Schengen area with my 60 days still usable?

I have searched the web a lot and could not find an answer that fits my situation. Here are two links that are quite contradictory:       My situation:  I've visited Portugal in December 2012 for 29 days on a Schengen visa valid from December 1st, 2012 to February 1st, 2013 for research purposes (I am a Ph.D. student). I want to visit Sweden from February 10th, 2013 to May 10th, 2013 (89 days). I have applied for a Schengen visa again (for research). How will the 90/180 rule work in my situation?


this is my first time asking on stackoverflow, and I have a trouble when programming with python 2.7. Here I have a calculation: 1350/2.7  The exact answer must be 500, but python give the answer 499.99999999999994  I know about the fact that some numbers cannot be represented exactly in binary, causing error on floating calculation.  So can anybody give me an advice? How to deal exactly with it?

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


I am just wondering if there would be any loss of speed or efficiency if you did something like this:  int i = 0; while(i < 100) {     int var = 4;     i++; }   which declares int var one hundred times.  It seems to me like there would be, but I'm not sure. would it be more practical/faster to do this instead:  int i = 0; int var; while(i < 100) {     var = 4;     i++; }   or are they the same, speedwise and efficiency-wise?

I have always wondered if, in general, declaring a throw-away variable before a loop, as opposed to repeatedly inside the loop, makes any (performance) difference?  A (quite pointless) example in Java:  a) declaration before loop:  double intermediateResult; for(int i=0; i < 1000; i++){     intermediateResult = i;     System.out.println(intermediateResult); }   b) declaration (repeatedly) inside loop:  for(int i=0; i < 1000; i++){     double intermediateResult = i;     System.out.println(intermediateResult); }   Which one is better, a or b?   I suspect that repeated variable declaration (example b) creates more overhead in theory, but that compilers are smart enough so that it doesn't matter. Example b has the advantage of being more compact and limiting the scope of the variable to where it is used. Still, I tend to code according example a.  Edit: I am especially interested in the Java case.


Especially when you are a new user your vote doesn't count (yet). I found myself voting on questions at the beginning but quickly lost motivation for it because it always went something like this: Post has X votes I vote Post has quickly X+1 votes Gets reverted to X votes in the next instant  Now there's at least a notification that your vote gets saved. But when it is already saved, why not show the vote all the time in the first place? In some places I have enough points that my votes do count but I still don't use it because I'm used to it not making any difference. If you change it to show the vote from the start, users are maybe more interactive with the voting system. Because if you look at the views of question and the upvotes of the answers, only a fraction of them actually casts a vote.

Users below 15 reputation can't effectively vote. It says:     Votes cast by those with less than 15 reputation are recorded, but do not change the publicly displayed post score   Does it mean that they will take effect after I reach 15 reputation or because they were cast before, they're recorded but ignored?


I'm having an issue trying to set up the default posts post type to use the permalink structure of /news/%postname%/ - I've tried editing the permalinks but it throws out my other custom post types.  I've currently got two other custom post types; 'careers' and 'case-studies' which use /careers/%postname% and /case-studies/%postname%  When adding "/news/" into the permalink settings it adds that to the custom post types as well, which I don't want. To help explain, it makes the two custom post types change to /news/careers/%postname% etc.   Is there a way I can change the slug or permalink structure of the default "posts" post type or another way around this issue please?  I've tried various solutions and had a good look around for similar issues but they aren't quite the same.

I would like to set a permalink structure with a prefix that will appear just on the posts. The prefix should only be displayed for the posts and not for the permalinks of categories or tags.   I set the permalink structure as /post/%post_id% and the post URL is example.com/post/12345. But the prefix added also to the categories and tags and it become example.com/post/category/news instead of example.com/category/news. How I can do it?


Consider:     If only it could snow in the town, my city would look amazing!   First, I would like to know is it "If only" or "only if"? which is more idiomatic? What about:     only it could snow in the town, my city ...   As another example:     only if I had that car, I would be in Hawaii now       if only I had that car, ....   Second I would like to know do I need "the" before "town"? because I've seen there is no "the" in phrases like "in town", is it a universal rule for any case?

What is the differences between "if only" and "only if" ? What is the use of each  in the sentences? Are there any specific rules for their uses?  "I could get more work done if only there weren't so much noise." "We will manufacture these handbags only if we can obtain the right leather."


I obtained two groups of data from my experiment and calculated the binomial distribution for each group, trying to see if they are significantly different from each other. However, the z sore I got was way smaller than -4, which was a little bit odd to me. Here is how I did my calculation:  The control group: # of trails n1=34; # of successes k1=2, success rate p1=2/34=5.9% The experimental group: # of trails n2=25; # of successes k2=2, success rate p2=2/25=8.0%  average p=6.8% standard error=0.0044 test statistic z=(5.9%-8%)/standard error=-4.77 It's a two-tailed test. I couldn't find a p-value corresponding to the z score I got (-4.77) on the table. Does that mean my p-value was just really small or I made mistakes here?

I have three groups of data, each with a binomial distribution (i.e. each group has elements that are either success or failure).  I do not have a predicted probability of success, but instead can only rely on the success rate of each as an approximation for the true success rate. I have only found this , which is close but does not seem to exactly deal with the this scenario.  To simplify down the test, let's just say that I have 2 groups (3 can be extended from this base case).   Group 1 trials: $n_1$ = 2455 Group 2 trials: $n_2$ = 2730      Group 1 success: $k_1$ = 1556 Group 2 success: $k_2$ = 1671   I don't have an expected success probability, only what I know from the samples. So my implied success rate for the two groups is:   Group 1 success rate: $p_1$ = 1556/2455 = 63.4%  Group 2 success rate: $p_2$ = 1671/2730 = 61.2%   The success rate of each of the sample is fairly close. However my sample sizes are also quite large. If I check the CDF of the binomial distribution to see how different it is from the first (where I'm assuming the first is the null test) I get a very small probability that the second could be achieved.  In Excel:     1-BINOM.DIST(1556,2455,61.2%,TRUE) = 0.012   However, this does not take into account any variance of the first result, it just assumes the first result is the test probability.  Is there a better way to test if these two samples of data are actually statistically different from one another?


Could it be possible that all of the unexplained phenomena (like uncertainty)  in our 4D world might be originated from a higher dimension universe? If so, then of course we'll never observe the actual phenomena since we only live in a lower dimension world. For people who live in higher dimension universe, all that is uncertain for us, is deterministic for them.

I've often heard the argument that having 3 spatial dimensions is very special. Such arguments are invariably based on certain assumptions that do not appear to be justifiable at all, at least to me. There is a  on Wikipedia.  For example, a common argument for why >3 dimensions is too many is that the gravitational law cannot result in stable orbital motion. A common argument for <3 dimensions being too few is that one cannot have a gastrointestinal tract, or more generally, a hole that doesn't split an organism into two.  Am I being overly skeptical in thinking that while the force of gravity may not be able to hold objects in stable orbits, there most certainly exist sets of physical laws in higher dimensions which result in formation of stable structures at all scales? It may be utterly different to our universe, but who said a 4D universe must be the same as ours with one extra dimension?  Similarly, isn't it very easy to conceive of a 2D universe in which organisms can feed despite not having any holes, or not falling apart despite having them? For example, being held together by attractive forces, or allowing certain fundamental objects of a universe to interpenetrate, and thus enter a region of the body in which they become utilized. Or, conceive of a universe so incomprehensibly different to ours that feeding is unnecessary, and self-aware structures form through completely different processes.  While I realise that this is sort of a metaphysical question, is 3+1 dimensions really widely acknowledged to be particularly privileged by respected physicists?