I'm currently writing a questions about namespaces for c++. After writing the title, SO will propose related answers to my question from title only. Unfortunately (very fortunately really), namespaces apply in many languages so unless I make a specific reference to c++ in the title, the suggested answers will not be aware of the target language for my question.  I thought that editing the tag sections of the question then going back to the question title would prompt different suggestions but it did not.  My question title is "Global namespace is not checked in other namespaces". I do agree that it is not the finest title, but I have trouble formulating a correct question since I understand my problem poorly for the moment.    This is what I get after typing in the title for suggested questions:        Note that none are for C++. This list does not update after adding the body or tags.

It happens often for me that, after submitting the answer, I look at the "Related" list on the sidebar and see questions that talk about the same question but have a title that's largely difference in words, although very close in meaning.  I know there's a "Similar Questions" list that appears while writing question body, but that's also based on text-processing, which seems to be the problem.  I suggest that, after the user adds the tags, a new "Questions that may already have your answer" list loads right above the "Post Your Question" button, and it depends not only the title and boy text, but also on tag association.  Hopefully it would be not very hard to implement, and would make users life easier.


I am looking for a small tactile switch that works like:  press once -> turn on, press again -> turn off  I only found this model  , but i am looking to buy directly from manufacturer/reference in mouser or digikey if possible, for a small production batch  do you know how can i find this?

If I say something like "SPDT switch" it's assumed to be a non-momentary switch.  Is there standard nomenclature for unambiguously specifying a non-momentary switch?


I'm writing a Trigger that After Insert of a new User, I need to create a Contact with that same new User information. I'm getting this error:      MIXED_DML_OPERATION      DML operation on setup object is not permitted after you have updated   a non-setup object.   Can someone explain how I could work around this error? Thanks!   trigger UserInsertContactInsert1 on User (after insert) {      if(Trigger.isAfter && Trigger.isInsert){         Set<ID> usrIds = new Set<ID>();          for(User u : Trigger.new){             usrIds.add(u.id);         }          List<User> usrList = [SELECT Id, FirstName, LastName, Email, Phone FROM User WHERE Id IN :usrIds];         List<Contact> cList = new List<Contact>();          for(User u : usrList){             cList.add(new Contact(FirstName=u.FirstName, LastName=u.LastName, Email=u.Email, Phone=u.Phone, OwnerID=u.ID, Related_User__c=u.Id));         }          insert cList;      } }

In my test class i have the creation of a dummy custom setting and a dummy lead:  Group g1 = new Group(Name='group name', type='Queue');              insert g1;             QueuesObject q1 = new QueueSObject(QueueID = g1.id, SobjectType = 'Lead');              insert q1;       SetOwner__c mycs = SetOwner__c.getValues('standardset');               if(mycs == null) {                               mycs = new SetOwner__c(Name= 'CustomValues');                  mycs.OwnerId__c ='00520000000z3PrAAI';                  mycs.RecordtypeID__c='012L00000004QsrIAE';                  insert mycs;      Lead lead = createNewLead(u2.id);                           insert lead;   ERROR:  MIXED_DML_OPERATION, DML operation on setup object is not permitted after you have updated a non-setup object (or vice versa): SetOwner__c, original object: QueueSobject: []   I get this error because i am trying to perform DML on setup and non-setup objects in the same transaction.  Any solution for this problem?


At least 5 people died in Bangladesh and more than 200 are injured.  At least 5 persons died in Bangladesh and more than 200 are injured.

I always thought persons was wrong.But recently, I came across this word "persons" in some book. Is it correct? If it is, when would you use persons and when would you use people?


Let $f(x)$ be a polynomial of degree $n$ with real coefficients such that $f(x)$ is non-negative for all real $x$. Let $g(x)=f(x)+f'(x)+f''(x)+\dots$ be the sum of $f(x)$ and the first $n$ derivatives of $f(x)$. Show that $g(x)$ is non-negative for all real $x$. Thanks for any comments/answers in advance!

Let $p(x)$ be a polynomial of degree $n$ satisfying $p(x)\geq 0$ for all $x$. That is, for all $x$, $p(x) = a_n x^n + a_{n-1} x^{n-1} + \cdots + a_1 x + a_0 \geq 0$, $a_n\neq 0$.  Show that $p(x)+p'(x)+p''(x)+\cdots+p^{(n)}(x)\geq 0$ for all $x$ where $p^{(i)}(x)$ is the $i^\text{th}$  derivative.  My interest: I know that, we can rewrite the LDE as follows  $$ p(x)+p'(x)+p''(x)+\cdots+p^{(n)}(x) = Lp(x) $$  where $L := I + D + D^2  + \cdots + D^{(n)}$. Can we say anything about a linear operator of this kind so that it does not change the sign of the input it takes? I can try to solve the question by writing for all the derivatives and factoring them using $p(x)$, but I think there should be a clever way of showing this by the properties of $L$. Can I figure out a solution by just looking at $L$ and the sign of $p(x)$ as in the question? Where should I look for that?


I’m an MS Access diehard and I’m running a 64bit version of Win 10 on my PC. I’ve installed both the 32bit (2.14.7) and 64bit (2.16.3) versions of QGIS on it, and MS Office 2016.  I would like to establish a persistent ODBC connection to an access mdb database but can’t get this to work on either on versions of QGIS.  Using the EVis plugin I have no issues in terms of linking to mdb, and identically accdb, databases on both the 32bit and 64bit versions of QGIS.  However, try as I may I can’t form a successful link via QGIS’s add vector layer ‘database’, ‘ODBC’ setting – the only thing I get is a database table header, its field structure, but no data whatsoever and the name assigned to the layer when I attempt this ends with ‘Unknown’.    It has been suggested that a modification to QGIS's bat file should overcome the issue I'm experiencing, as per adding the following two lines:   set OGR_SKIP=ODBC set PGEO_DRIVER_TEMPLATE=DRIVER=Microsoft Access Driver (*.mdb, *.accdb);DBQ=%%s  I've done this, but in my two installations of QGIS the second line of that code doesn't appear to have any effect, since when I drag an mdb file into QGIS's workspace I get an invalid file format error.  How I can resolve this issue and establish in QGIS a persistent ODBC connection to an access mdb database?

So I followed the instruction here:  for adding a .mdb into QGIS. There are great instructions about 1/3 of the way down. But I still can't get it to open. I on Windows 7 with QGIS 2.4  I restarted QGIS and my computer. I am still getting the error: "Invalid Data Source: ODBC:co2014ProdSumm (btw this is the .mdb) is not a valid or recognized data source. "  These are not vector layers nor is this a ESRI personal geodatabase. This is an Access database with 2 tables I need out of it.   I also found a few other posts    and this one might be the answer but I don't know what it's talking about:   Is there any way to add a .mdb into QGIS? Also I do not have Access on my computer.   Edit 1:I hope this clarifies my issue.  Each time I get Invalid Data Source: C:...Co 2014 Annual Production Summary-xp.mdb is not a valid or recognized data source. Here is where I added the access connection    Trying to add as a vector file   Trying to add a database, I also tried local:host 3000 The error in the pic is the same no matter the source, name etc... I've tried changing all fields around.


I am sending an email to User after who subscribe to my website newsletter. But sometimes the subscription email going to SPAM folder. I am sharing the link of spam mail test result --  Please check the result(analysis) of SPAM mail tester given above & tell me why my mails are going to SPAM  Here is my configuration to send mail through code-->      $config = Array(  'protocol' => 'smtp',  'smtp_host' => 'mail.holaa.in',  'smtp_port' => 25,  'smtp_user' => 'noreply@holaa.in',  'smtp_pass' => 'XXXXXXXXX',  'mailtype' => 'html',  'charset' => 'iso-8859-1'  );  $this->load->library('email', $config);  $this->email->set_newline("\r\n");  $this->email->from('noreply@holaa.in');  $this->email->to($receiver);  $this->email->subject($subject);  $this->email->message($message);  $ans = $this->email->send();   Thanks in advance

This is a tricky one and I've always relied on techniques, such as permission-based emails (i.e. only sending to people you have permission to send to) and not using blatantly spamish terminology.  Of late, some of the emails I send out programmatically have started being shuffled into people's spam folder automatically and I'm wondering what I can do about it.  This is despite the fact that these particular emails are not ones that humans would mark as spam, specifically, they are emails that contain license keys that people have paid good money for, so I don't think they're going to consider them spam  I figure this is a big topic in which I am essentially an ignorant simpleton.


If I have a in play and choose creature type Myr, do the abilities of  interact with the Door?  Do either of Myr Turbines effects cause Door of Destinies to trigger? Or, . Do the 4 myr tokens it generates count?  Seems like the second would but im not sure about tokens...

Are token creatures considerd creature spells? For instince when I use  tap effect combined with  would it allow me to draw a card?


I am using the listings package to document code in a LaTeX document and have line numbering turned on to be able to refer to specific sections in the code. Most changes to the code being documented, something that occurs quite frequently, necessarily mess up the references to line numbers in the accompanying text. Is there a way to make these references to line numbers dynamic, i.e. does the listings package provide a way of identifying lines with labels? I skimmed through the documentation once again, but nothing leaped at me.

I was wondering if it is possible to refer to the lines of the code enclosed in lstlisting environment rather than just manually write a number of the line I want to describe. I have never met with this feature, is this available?


I am attempting to install 'Ubuntu Server 14.04.3 LTS' with a Flashdrive (there is no DVD/CD onboard). However, after keyboard selection a notification is presented saying:   "Your installation CD-ROM couldn't be mounted. This probably means that the CD-ROM was not in the drive. If so you can insert it and try again."   Trying to check Disk Integrity fails because No CD-ROM is mounted.  Things like "Intel Speedstep" and "Secure Boot" are disabled. I've tried UEFI and Legacy installs both with same results.  I've tried the solution presented  with no success (even though it's to a similar but different problem).  I've also tried multiple different Bootable USB programs:   Ubuntu's default  UNetbootin YUMI Rufus   Computer: Lenovo ThinkServer TS130  Notice: I am a novice to this and thus answers with required knowledge I might not understand.  Update Info:  On USB boot, after selecting install - where the screen is black a few quick text notification are flashed.  The first one at the top of the screen:   ACPI PCC probe failed.  tpm_tis 00:06: A TPM error (6) occurred attempting to read a pcr value  Starting system log daemon: syslogd, klogd.   The second one at the bottom of the screen:   mount: mounting /dev/sda on /media failed: Invalid argument  unmount: can't unmount /media: invalid argument  mount: mounting /dev/sda on /media failed: Invalid argument  mount: mounting /dev/sda1 on /media failed: Invalid argument  unmount: can't unmount /media: invalid argument  mount: mounting /dev/sda1 on /media failed: Invalid argument  mount: mounting /dev/sda2 on /media failed: Invalid argument  unmount: can't unmount /media: invalid argument*  mount: mounting /dev/sda2 on /media failed: Invalid argument  Trying to enable the frame buffer...

How do I make an Bootable Ubuntu USB containing the the latest version of Ubuntu?  For completeness, how would I be able to do this on Ubuntu, Windows, OS X or another Linux distro?


Let  $(X,d)$  be  a  complete  metric  space  and  $$f \ :\ X\rightarrow X$$  be  a   map   such  that  ,  for  some  positive  integer  $k$ ,  $$f\circ f\circ .....\circ f(\ k\ \ fold\ \ composition\ \ with\ \ itself\ )$$  is  a  contraction.  Then  $f$  has  a  unique  fixed  point .  How  should  I  approach  this  problem  $?$   Sorry  for  the   lack  of  efforts  here  .  Please  give  me  some  hints  as  to  how  to  begin  the  thinking  $?$

I wanted to show that if $f:X\to X$ is a function from a complete metric space to itself and if $f^k$ is a contraction, then $f$ has a unique fixed point (say $p$) and for any $x$ in $X$ $f^n(x)\longrightarrow p$.  What I did is use what I know from Banach as follows: Take $x$ arbitrary in $X$. Then consider the sequence $f^n(x)$, which I denote by $x_n$. Let $x^{(i)}$ be the sequence $x_i, x_{i+k}, x_{i+2k}...$ for $i$ between 0 and $k - 1$. As $f^k$ is a contraction, we can apply Banach and so it has a fixed point (say $l$) and all the $x^{(i)}$ are convergent to $l$.  Then $x_n$ is convergent to $l$ (for any $\epsilon$ exists $N$ such that $d_X(x_n, l) < \epsilon$, this $N$ being the maximum of the corresponding N's obtained from each of the $x^{(i)}$).  Since $x$ was arbitrary and $l$ is unique, this means that $p=l$ and the proof is completed.  Am I doing something wrong or missing anything?  I just want to ensure I understand this properly, this is not a homework or something similar.  Thank you!


How to write or tell that collection of Email ID's has been attached.

For example, if I wanted to write the equivalent of  There are many automated teller machines in this city.  Would it be  There are many ATMs in this city.  or  There are many ATM's in this city. (could get confused with possessive form or contraction).  or just  There are many ATM in this city. (assuming the final s is included in Machines represented by M).  Maybe something else?


While trying to install lollypop I got this error   Traceback (most recent call last):   File "/usr/lib/python3/dist-packages/lollypop/container.py", line 79, in update_db     self.__show_first_run()   File "/usr/lib/python3/dist-packages/lollypop/container.py", line 335, in __show_first_run     view = FirstRunView()   File "/usr/lib/python3/dist-packages/lollypop/view_first_run.py", line 29, in __init__     builder.add_from_resource("/org/gnome/Lollypop/FirstRunView.ui") GLib.Error: gtk-builder-error-quark: .:3:50 Required gtk+ version 3.20, current version is 3.18 (7)

I am running Ubuntu 15.04. I installed GNOME on top of that. Now I am using GNOME Shell. I heard 3.16 has many improvement. I am thinking about upgrading. My question is that, if I upgrade to GNOME 3.16 will I be able to upgrade to the next version of Ubuntu (15.10) when it arrives?


I'm basically trying to install a package that requires snappy compiled in c for speed. I have already downloaded and installed the required compiler from here .  This  is the error I'm getting.  I can't figure out why it's not able to get stdint.h. It should come with the compiler right?   Any tips would be appreciated.

To my amazement I just discovered that the C99 stdint.h is missing from MS Visual Studio 2003 upwards.  I'm sure they have their reasons, but does anyone know where I can download a copy?  Without this header I have no definitions for useful types such as uint32_t, etc.


I have a lengthy function that is messing up:  \begin{align*} D(a,z) &= \frac{1}{\sqrt{\pi}}2^{\frac{a}{2}}e^{-\frac{z^2}{4}} \left(\cos \left(\frac{\pi a}{2}\right)\Upgamma \left(\frac{a+1}{2}\right) \ {_1F_1}\left(-\frac{a}{2};\frac{1}{2};\frac{z^2}{2}\right) \\  &+ \sqrt{2}z\sin \left(\frac{\pi a}{2}\right)\Upgamma\left(\frac{a}{2}+1\right) \ {_1F_1}\left(\frac{1}{2}-\frac{a}{2};\frac{3}{2};\frac{z^2}{2}\right) \right) \end{align*}   The last bracket \right) is not showing up. I think this is because I broke the lines in the middle at &+. Rather than splitting up the function into another set with the term right next to D(a,z)=, would it be possible to get this bracket working? I'm sure it would, I just don't know how.     Thanks!

I have a very long equation that must be separated into two lines, and it has several pairs of nesting \left \right delimiters. Unfortunately, it seems that they need to be on the same line in order for them to work.  Also I'm using the align environment because I need the aligning functionality. Is there a way to have the size of delimiters automatically adjusted over multiple lines?


I've been messing around on Minecraft with Not Enough Items, trying to get an ∞ amount of items so that I can make a rapidly-firing dispenser that always shoots and doesn't run out of ammo. I mean when people have like 111 spawn eggs or something in their inventory.   I know how to make a redstone clock. But I try to get an ∞ amount of fire charges, it says in chat it gave me an ∞ amount of fire charges, but I don't have it in my inventory.   Any suggestions?

I want to know how to make a dispenser that can throw an infinite amount of arrows. I want to use this for my base.  Is it possible? If so how can I do it?


I have been member of SO for 4 months. I have a question regarding some functionality. Whenever I give an answer to a question, there is functionality given Add Another Answer. I can comment on my answer at any time and also able to edit answer. Then   Why this functionality given on SO to add another answer?  When should I add another answer?  Why there is requirement of multiple answers? What is limit of adding answers to single question?

When is it reasonable/recommended to add another answer when I have already added one? My doubt comes from  that I  although I find later that the question was not complete. I found a way to solve the problem and was going to post it when I got the "add another answer" question.  So, should I post a new answer in this case or edit the somewhat faulty one? Better yet, when is it appropriate to post another answer?


I am Using menu token module to access pages related particular user, I am getting issue while selecting path in token menu using replacement patterns. can any one explains on what basis it will take the link and direct to the page. i tried to use [node:content-type:name], As there are so many content types created in my site, so how it will take the specific content type which is related with the node.  kindly suggest me if there are alternatives for this.. i am fed up by trying this whole day.


Suppose $\phi: [0,1] \to \mathbb R^n$ is a continuous map. Does there exist continuous, injective $\psi : [0,1] \to \mathbb R^n$ such that $\psi(0) = \phi(0)$ and $\psi(1) = \phi(1)$ and $Im(\psi) \subset Im(\phi)$?

Let $X$ be a path-connected topological space, i.e., for any two points $a,b\in X$ there is a continuous map $\gamma\colon[0,1]\to X$ such that $\gamma(0)=a$ and $\gamma(1)=b$. Note that beyond continuity little is required about $\gamma$.     Is it always possible to make $\gamma$ a simple (=injective) curve? (Of course we consider only the case $a\ne b$).    If the answer depends on $X$, what are some mild sufficient conditions on $X$?   If $X$ is sufficiently nice, e.g., an open subset of $\Bbb R^n$, the answer is "yes";  more generally, what one would call "locally simplepath-connected" suffices (the set of points reachable from $a\in X$ by a simple curve is both open and closed). Also, for arbitrary $X$ it is clear that a single instance of self-crossing can be short-cut. But for infinitely many possible short-cuts the situation may become somewhat hairy, I'm afraid.  EDIT: To avoid Mike Miller's counterexample (indiscrete topology on $X$ with $|X|<|\Bbb R|$), let's at least assume that $X$ is Hausdorff. At any rate, $|X|\ge|\Bbb R|$ is a necessary condition - I am still looking for "as mild as possible"  sufficient conditions ...


What is the default timeout interval of a sudo session? How to edit that?

I execute quite a lot of sudo commands.  I noticed that if I execute one and then another one within few minutes, the 2nd time I don't get the message:     [sudo] password for my_username:   but I do get it when there is more time between the execution of the two commands.  What's the period of time in which the message is not appearing? How can we check it / update it?


Does a rogue wielding two weapons get two sneak attacks or is the sneak attack damage bonus only valid for the first attack?

I've designed for a campaign a duo of rogues. My character is as Sniper, and his follower is a Knife Mistress. Couple of questions about them.  Our party is about to ambush several trolls. My Sniper will hide near their camp, and shoot the weakest one when fight begins. His follower will then rush the troll and slice him in several pieces.  My Knife Mistress is high enough to have BAB +6/+1, is dual-welding daggers and has the Improved Two-Weapons Fighting feat. I get 4 attacks (+8, +8, +3, +3).  Now, does she deal Sneak Stab's damages on each attack (×4), only on main hand attack (×2), on only once per round (×1), as in 5e?


so I'm relatively new to lightning web components and still not understanding all of the eventhandling. I'm creating a component for a customer and I'm having some problems with my lightning-datatable.  i have a parent-child structure like this  parent.html  <c-custom-data-table table-data={tableData}></c-custom-data-table>   parent.js  export default class fastOrder extends LightningElement {     @track tableData = [];     localTable = [];      setRowData(event) {         this.localTable.push(event.detail);         this.tableData = this.localTable;         this.template.querySelector('c-custom-data-table').setTableData(this.tableData);     } }   child.html  <lightning-datatable                               key-field="Produktcode__c"                 data={tableData}                 columns={columns}                 onrowselection={getSelectedRecords}>         </lightning-datatable>   child.js  export default class BasicDatatable extends LightningElement {     @track columns = columns;     @track tableData = [];      @api setTableData(detail) {         this.tableData = detail;      } }   Im calling setRowData(event) from another child-component in the context of an event. The first time I'm doing this the view of the datatable is refreshed after the tableData property gets updated. But every other time than the first one theres no refresh of the view. according to the console the tableData property gets properly updated but i dont see any new rows in my datatable.  I also tried changing the binding to @api with getter and setter   @track _tableData = [];     @api      get tableData() {         return this._tableData;     }     set tableData(value) {         this._tableData = value;     }   with exactly the same effect.  Am I missing something here? I saw examples with @track binding which got constantly refreshed with the update of the tracked property. I searched and tried for hours but maybe someone already encountered this kind of situation and can help me with a workaround (or atleast an explanation).  Thanks in advance!

From SF :      There are some limitations on the depth of changes tracked for   rerendering in reactive properties. The tracking depth depends on the   type of the reactive property.      Lightning Web Components tracks changes to the internal values of   these types of reactive properties:         Primitive values    Plain objects created with {…}   Arrays created with []         Also SF does not track for complex types like Date.   Now what I wanna do is track an Array of complex object. If a new element is added subtracted from the array re-render the UI. Classic Data - table example.  So I declared my Markup:  <template>     <h1>Hello </h1>     <lightning-datatable                 key-field="id"                 data={data}                 columns={columns}                 is-loading={tableLoadingState}>             </lightning-datatable>              <lightning-button variant="brand" label="Add row" title="Add row" onclick={addRow} class="slds-m-left_x-small"></lightning-button> </template>   JS:  import { LightningElement, track } from 'lwc'; const columns = [     { label: 'Label', fieldName: 'name', type:"text"},     { label: 'Website', fieldName: 'website', type: 'text' },     { label: 'Phone', fieldName: 'phone', type: 'text'  } ]; export default class App extends LightningElement {     @track data = [{name:'Mylabel' , website:'google.com' ,phone :'74126478963',amount : 45  }];     @track columns = columns;     @track tableLoadingState = false;      addRow(){         console.log('add row called');         this.data.push({name:'Mylabel2s' , website:'2google.com' ,phone :'74126478963',amount : 45 });         console.log(JSON.stringify(this.data));         //this.data =[];      }   }   When I save and try running this I get the message as shown in docs.  [LWC warning]: Property "_def" of [object:vm undefined (0)] is set to a non-trackable object, which means changes into that object cannot be observed. <lightning-primitive-header-factory>   which means I cannot track the row data for lightning-datatable, which also means when I add or remove rows I would be unsuccessful.  I could not find a solution to add row in datatable and get it updated back in the markup, I searched dev guide and recipe book. Is this a limitation? or there is a workaround?


I just got a 35mm f/1.4 lens and wanted to see if it has any focus issues to be fixed. So I got this kit and not sure what exactly I should have done but I focused on the middle of that bar code like area where it was bent and took the shot. To my eyes ( and I don't have good eyes) feels like Zero of the ruler is in focus but at the same time I feel like nothing is sharp enough. So I uploaded the image here in DropBox, please take a look and tell me what you think.

I have a Canon 7D with a 50mm f/1.4 lens, and I think the auto-focus of the lens is off.  How can I test and adjust this reliably?  Will this approach work with all of my lenses? If I had a different camera body, would I have other/different options?


First some notation and definitions: In the Bayes formula as written for machine learning applications, $$    p(\theta|D) = \frac{ p(D|\theta) p(\theta) }{ p(D) } $$ commonly $p(\theta)$ is labeled the prior, $p(D|\theta)$ is called the likelihood, and $p(D)$ is called the evidence (or marginal likelihood I think).  Elsewhere (in various books), the likelihood is defined as $$    p(D|\theta) $$ viewed as a function of $\theta$, not of $D$.  But $\int p(D|\theta) d\theta$ does not necessarily integrate to one, and therefore is not a probability density. As support, in the Bishop Pattern Recognition & Machine Learing book p.22, "Note that the likelihood is not a probability distribution over w, and its integral with respect to w does not (necessarily) equal one."    On the other hand, I believe $\int p(D|\theta) d D$ does integrate to one. But this is the integral of a conditional probability, not a likelihood.   Finally the question: is the likelihood in the Bayes formula really a likelihood (since a likelihood is not a probability)?  If not, why is it called a likelihood?  If so, how can a non-probability appear in this formula that calculates the posterior probability?  How to think about this?  (In fact I have a theory about what the answer is, but since I am self learning I hope to hear a better and complete explanation rather than an answer "yea that's right", from which I would learn nothing)

What is the reason that a likelihood function is not a pdf (probability density function)?


We are running an underwater campaign where everyone is an aquatic race, and most of the campaign will take place completely underwater. Call Lightning says: "A storm cloud appears in the shape of a cylinder that is 10 feet tall with a 60-foot radius, centered on a point you can see within range directly above you. The spell fails if you can't see a point in the air where the storm cloud could appear (for example, if you are in a room that can't accommodate the cloud)." Does this literally mean you must be able to see a point "in the air", or could this work beneath the waves?

As the old adage goes "water and electricity don't mix" because in real life water has impurities in it that make it super conductible. So what would happen in D&D if, for instance, a sorceress cast  on a creature underwater?  Would the spell not work? Would it affect the caster as well? Would it spread and hit everything under water?   Shocking grasp in particular specifies that "You have advantage if the target is wearing metal armor" which indicates that they are taking conductivity into account.  What about  or , would casting a higher level spell change the outcome?


I am currently getting null pointer exception in a fragment while calling getHolder. here's the Code for the fragment  public class Camera_Fragment extends Fragment implements IVideoPlayer, View.OnClickListener { Button up, dowm, right, left;  SurfaceView CamView; private String VideoUrl = "http://192.168.0.4:81/videostream.cgi?user=admin&password=admin";  private SurfaceHolder Holder; private Surface surface = null; private LibVLC libVLC;  private int mVideoHeight; private int mVideoWidth; private int mVideoVisibleHeight; private int mVideoVisibleWidth; private int mSarNum; private int mSarDen;  @Nullable @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {     View view = inflater.inflate(R.layout.cam1, container, false);     CamView = (SurfaceView) view.findViewById(R.id.Cam1_CamVIew);      up = (Button) view.findViewById(R.id.Cam_up);     dowm = (Button) view.findViewById(R.id.Cam_down);     right = (Button) view.findViewById(R.id.Cam_right);     left = (Button) view.findViewById(R.id.Cam_left);      up.setOnClickListener(Camera_Fragment.this);     dowm.setOnClickListener(Camera_Fragment.this);     right.setOnClickListener(Camera_Fragment.this);     left.setOnClickListener(Camera_Fragment.this);     return view; }  @Override public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     Cam_Play(); }  private void Cam_Play() {     Holder = CamView.getHolder();     try {         libVLC = new LibVLC();         libVLC.setVout(LibVLC.VOUT_ANDROID_SURFACE);         libVLC.setHardwareAcceleration(LibVLC.HW_ACCELERATION_AUTOMATIC);         libVLC.init(getActivity().getApplicationContext());     } catch (LibVlcException e) {         e.printStackTrace();     }     surface = Holder.getSurface();     libVLC.attachSurface(surface, this);     libVLC.playMRL(VideoUrl); }   The above Code is working flawless in a Activity.. But in the fragment its not .. I am still a biggner in Android development.And i am using fragments for the first time. Any Solution or suggestion.  here's the logcat   11-17 01:03:52.301 5860-5860/com.fyp.tirz.wifisurveillance E/AndroidRuntime: FATAL EXCEPTION: main 11-17 01:03:52.301 5860-5860/com.fyp.tirz.wifisurveillance E/AndroidRuntime: Process: com.fyp.tirz.wifisurveillance, PID: 5860 11-17 01:03:52.301 5860-5860/com.fyp.tirz.wifisurveillance E/AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.SurfaceHolder android.view.SurfaceView.getHolder()' on a null object reference 11-17 01:03:52.301 5860-5860/com.fyp.tirz.wifisurveillance E/AndroidRuntime:     at Fragments.Camera_Fragment.onCreate(Camera_Fragment.java:62)

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I have put some additional details below, but as a quick note this is not Deep Range by Arthur C. Clark. However, it not only shares many of the same types of undersea aqua culture/farming with Deep Range, as I recall the story had a 'Clarkesian' feel to it. Unfortunately reviewing Clarke's bibliograpy and having read most of the novels/novellas lsited I could not find one that fit. That includes Cradle which also has some aquatic themes. Nor is it Dolphin Island, The Hydronauts nor any of the Tom Swift stories. I am pretty sure it was at least novella length if not a full novel.   A teenage Lunar colonist boy visits Earth with his diplomat father during a bid for Lunar independence. In one memorable early scene at the hotel/resort/ambassadorial complex at which they are staying he is at the pool (which he does frequently because it helps relieve the gravity pull which is hard for him).  He watches with some minor disbelieve at the practice of tourists putting oil on themselves and baking in the sun.  However, he then notices a teenage girl who is as pale as a moonbeam and can swim with the ease and grace of porpoise. The girl turns out to be an aqua farming colonist whose parent is also at the (UN?) gathering to consider the Lunar independence proposal.    The two hit it off and the boy is allowed to go with the girl to her undersea home. In one early scene within the undersea colony dome the boy is scared when he finds cannot speak without squeaking. It was an oxy-helium mix (vs. nitrogen) used to prevent the bends (a later plot point). The undersea colonists allow the boy to help with various tasks around the colony. He gets stung by I believe either a manta ray or jellyfish which becomes a plot point later on.  At one point there is what appears to be sabotage to the 'fish fence' which shuts off the walls of bubbles in the water keeping the fish penned in. The boy is accused of being the saboteur and is put on trial. In an interesting judicial form defendants and witnesses are asked to swear in using either a globe or a silver/platinum orb representing the moon. Towards the end of the book there is a climactic escape scene during the voting on the Lunar independence. The boy does an untimed ascent out of the colony (leading to the bends mentioned earlier).    While the age of the protagonists (older teens) and lack of overt sex/violence made it feel like a young adult story I don't think it was meant as one. But, could be wrong.

About twenty years ago, I read a sci-fi novel where, if I recall correctly:   The protagonist is a guy, and probably a teenager or a young adult. Like most of humanity, he lives on land; but he's visiting an undersea colony (one of many?), and that's where most of the action takes place. He gets to know a girl there about the same age; maybe he's staying with her family for some reason? (Maybe they're relatives of his?) The girl had an older brother ("Ian", maybe?), but he died. He goes out of the city (i.e., goes for a dive) at some point, and gets in trouble, but is mysteriously rescued. He learns about an underground separatist movement of some sort. (I don't remember the details.) He eventually discovers that:       Ian is actually alive, and his family (or at least his sister) is still in touch with him; but they're covering up the fact that he's joined this separatist movement, and (like some other separatists) has modified his body to have gills so he can live out in the ocean.      Ian is actually who rescued him mysteriously.     I would guess, in retrospect, that the novel is from the 70s or so; but I don't really know.  I read the novel in English, and I don't think it was a translation.


I don't recall enough material for this to be a novel, but I may have simply forgotten a great deal.  The protagonist (young, male, uninfected) is transporting an infected young woman to either a quarantine area or a safe zone.  If I'm not conflating stories, this was set in the U.S. and he's headed roughly for Florida.  I don't recall if he's doing this out of a sense of what's right, or because he's been recruited/paid to do it.  The infection causes people to grow novel sense organs, like the ability to taste things with their hands.  (There may be further effects as the infection progresses, but that happens off-screen.)  They naturally become friendly, and one night he wakes up to find she's running her hands over his face - which will transmit the infection to him.  There are some (2?) scientists involved who are sympathetic/helpful; they offer to try to keep him from getting infected, which essentially involves an acid bath.  He changes his mind at the last minute, deciding to accept being infected to stay with the young woman.  One of the scientists is infected, and in order to stay focused on his work he chooses to chemically burn off any sense organs that grow on him.  I feel like I read this about 12-15 years ago.

I'm trying to locate a story I read sometime in the seventies in an anthology so it may have been written earlier. A plague/alien parasite has infected earth wreaking havoc. It's communicated by touch (and those infected develop a compulsion to touch other people). Those people infect have grey skin caused by, it turns out, massive nerve growth.   The protagonist might have been a priest ministering to the "sick". And in the advanced stage the infected might have grown a third eye. It's also possible the infected were called "feelies" (but using this to search only turns up stories where feelies are a future version of tactile TV).  Any help appreciated. Thanks.


I have just drawn a set of bar charts over a layer in ArcGIS 10.2 for Desktop.   How can I manage rotate the charts keeping my dataframe with the same rotation?  The options offered in Symbology Display only lets you to display the chart as bar or column.   Any chance to set a rotation angle??

I am using ArcMap 10.2 and want to represent a layer in a rotated dataframe with chart (graph) symbology. The problem is that the charts do not rotate with the dataframe:     I thought I could convert to graphics and rotate each chart individually, but   that is very tedious I don't find an option to convert a layer to graphics, works for the legend but not for the actual layer symbology


I am trying to install GCC by the command sudo apt install gcc in the terminal of my Ubuntu 18.04.1. But I am getting the following message:  bharath@bharath-Lenovo-G50-80:~$ sudo apt install gcc [sudo] password for bharath:  Reading package lists... Done Building dependency tree        Reading state information... Done E: The package savap:i386 needs to be reinstalled, but I can't find an archive for it.   bharath@bharath-Lenovo-G50-80:~$ apt-cache policy savap:i386 savap:i386:   Installed: 14.0.3876-1100   Candidate: 14.0.3876-1100   Version table:  *** 14.0.3876-1100 100         100 /var/lib/dpkg/status   Could anyone please suggest a way to fix this?

Running Synaptic I get the following error message:  E: The package hl1440lpr needs to be reinstalled, but I can't find an archive for it. E: Internal error opening cache (1). Please report.   Upon accepting the message, Synaptic quits.


Did anybody figure out how to successfully install Ubuntu 16.04 or 18.04 on a MSI GS65 8RF? After finally installing it (after following ), it freezes when I try to log in.   I've already disabled secure boot and set the BIOS to UEFI only.   Does anybody have a solution for this?  Edit: It is not a duplication, MSI GS65 still freezes even after BIOS update

I've been trying to get Ubuntu 18.04 LTS running on my new MSI GE63 Raider. I can get into the live USB by passing acpi=off and then running the installer. After that, I install the proprietary nvidia driver (nvidia-driver-390). Also I have tried installing nvidia-prime and bumblebee. I've also blacklisted nouveau.  The issue is that I cannot for the life of me get it to boot without passing acpi=off, because otherwise it hangs at a purple screen. When trying in recovery mode with any of the included kernels (4.15.0-20 and 4.15.0-29) I can see it hangs at   Loading initial ramdisk.   In addition to the above I tried passing following parameters in GRUB:   acpi=ht acpi_osi= acpi_osi=! acpi_osi="Windows 2009" acpi_osi=! acpi_osi="Linux" nomodeset nogpumanager   ... and a couple more (I forget after trying so many)  The specs of this laptop are:    intel i7 8750h (6 core) nvidia gtx1060m 16gb of RAM 256gb ssd (which holds the windows 10 partition and the "/" 1000gb hdd (which holds the data for windows and "/home"   The BIOS settings are set to UEFI. Fast boot and secure boot are both disabled. I've also tried switching off Intel speedstep and c-states, both to no avail.  Also, I have tried to install Debian 9, Lubuntu 17.04, Ubuntu 16.04 LTS, Deepin 15.5 and Mint 18, all of which need the added acpi=off flag.  Does anyone have any advice for this?  Thanks in advance!


If it is, whats the first meaning that you get from it?

Is "medium appearance residential buildings" correct? Am I not sure it's correct or not?  Is it the representative of "aged and worn out residential buildings"? How else might I express this? I want a phrase that combines semi-aged and semi-worn out in one.   I am writing a scientific paper. I categorized buildings by their qualitative state in three classes. I simply want a good name for those classes. those classes were good appearance buildings, medium appearance buildings, and decayed buildings. (In the case of repair, quality of material and how rusty they are - just physical appearance.) But I think this combination is not good for repeated usage in my text.


Like do they understand the mechanism behind it? Is there a mechanism behind it? (for a lack of a better word) Or is it just thought to be a law without any further explanation?

Please will someone explain what time dilation really is and how it occurs? There are lots of questions and answers going into how to calculate time dilation, but none that give an intuitive feel for how it happens.


I am working on converting a large map into a booklet format.  I am making selections of 4 inches by 7 inches then copying them to make a new layer.  When I drag this new layer into a new document it is increasing in size.  How to I make the sizing consistent between layers?

Let's say I have a file that's 4'x12' and represents a space on an actual wall. I want to open certain files (of different sizes) and drag each file into the large file in order to arrange the images correctly on the computer before physically hanging the framed finals.  When I drag a new image into the larger file, the new image's size and the size of its copy don't match. That is, Say I drag an 8x10 into the large file, well on the large file (trying to control size with guides and rulers) the new image is some other size, but not the right one.   What am I doing wrong? How do I make sure that when I click and drag the new image that it will be properly represented?


My laptop came with 2gb RAM but i am thinking to extend it to 6 GB By keeping 4gb ram in The Other slot. Is it better to take 4gb RAM and extend ny system memory To 6GB or Take 2GB RAM and extend it to 4GB .Please give me reply as soon as possible. Thanks in advance

My laptop has two slots for RAM, and currently has two 512 MB chips, for 1 GB.  Windows XP is running terribly slow on it, so I want to upgrade the RAM.  I could buy two 1 GB chips to replace both of the current 512 MB chips, to give me 2 GB of RAM.  Or, the price is the same to buy one 2 GB chip, to replace just one of the 512 MB chips, and give me 2.5 GB total.  The RAM it takes is PC2-4200 533MHz DDR2.  What do you think would be better: buying two 1 GB chips so it can take advantage of dual-channel operation, or buying one 2 GB chip to end up with more total RAM but not dual-channel operation?  Like I said, price is the same, so performance is the only consideration.  I'm not doing anything especially intensive like video or photo editing -- just having multiple Office programs open, playing music, browsers, etc., but currently even opening the first application takes forever.  If it matters, the laptop is a Toshiba Qosmio G25-AV513 running Windows XP Media Center SP3.  Thanks! Kevin


Early in a dangerous encounter we were able to save our bacon by trapping an Archmage with a Bead of Force, effectively removing him from the fight for 1 minute.  We managed to eliminate his allies several rounds later and then started to gather around the sphere that the Archmage was trapped in so that we could cut him to pieces as soon as the sphere disappeared. There were two rounds left before the sphere was gone.   DM decided to have him cast Time Stop and ruled that doing so would give him time to wait out the sphere and then cast Teleport in order to escape, all while we were frozen in time.   We all disagreed, saying that, because the passage of time is stopped for all but the Archmage, we and the sphere would proceed normally from our perspective and the Archmage would just have more time to write his last will and testament before the sphere disappeared and we dog piled him.   If water kept flowing, if sand dials kept pouring, if spheres of force marched closer to expiration, then time didn’t stop, did it? In that scenario, sentient life was frozen while time kept passing, and that’s not what the spell says. It’s Time Stop, not Life Freeze.  What do you think? Was the DM correct in his ruling, or should the Archmage have been ripped apart by ravenous adventurers?

The  spell says time stops for other creatures.  What all is affected by the spell? Is gravity affected? Air movement?  I know that the spell only does what it says, and nothing else, but just wondering.   In addition, is it saying that the other creatures are not affected by environmental effects and the like while time is stopped?  For instance, if a wind blew really hard at one of the creatures you're fighting, would it affect that foe while time stop is active? If you were to place a bear trap behind the person, and a hard wind blew enough to tip them, would they then fall over onto the bear trap and be damaged without the spell ending?  This is a very curious spell...


I trying to put smooth shadow on my final render view like you you can see on the right.

I am very beginner in Blender Cycles. I am trying to imitate this in cycles:  Not sure if this scene is CG or an actual photograph. I have modeled the eggs (easy), now I just want to imitate the lighting setting of this scene. I have tried adding:   One White Plane emitter above the eggs Same Plane emitter behind the camera, directly facing the eggs. Two Plane emitters on either sides of the camera facing the eggs. Turned Ambient Occlusion ON for the world.    I am getting either too crisp shadows or crossing shadows but never the same as in the scene.  So my question is which lamp should be used and where ? Please also explain why ?  I am currently here:   If I make the plain larger, the whole scene gets too bright:


I've got 12 items in arrays like this:  $item[1] = array('pseudo' => 'Item1', 'name' => 'apple', 'rarity' => '1', 'id' => '1' ); $item[2] = array('pseudo' => 'Item2', 'name' => 'banana', 'rarity' => '30', 'id' => '8' ); $item[3] = array('pseudo' => 'Item3', 'name' => 'cherry', 'rarity' => '23', 'id' => '12' ); $item[4] = array('pseudo' => 'Item4', 'name' => 'pear', 'rarity' => '27', 'id' => '18' ); $item[5] = array('pseudo' => 'Item5', 'name' => 'watermelon', 'rarity' => '70', 'id' => '14' ); $item[6] = array('pseudo' => 'Item6', 'name' => 'orange', 'rarity' => '100', 'id' => '17' );   What I need is to print 1 of the 6 items randomly but affected by its rarity, so the more rare it is the less times it will occur the rarity is from 1-100. How do I accomplish this using php?

I know how to generate a random number in PHP but lets say I want a random number between 1-10 but I want more 3,4,5's then 8,9,10's. How is this possible? I would post what I have tried but honestly, I don't even know where to start.


I was preparing for PD1 exam and came across the below sentence on interface in the developer documentation which I’m unable to understand. Can anyone help with an example as to what the below statement implies?  If you define a variable whose type is an interface, any object you assign to it must be an instance of a class that implements the interface, or a sub-interface data type.

So I believe that I have a real world use case for an object model that uses abstract classes and interface. I do however have a few questions about the best way to go about it:  Interface  public interface iLove{    String pet(); }   Abstract  public abstract class Animal{    public string animalName {get;set;}    public boolean happy {get;set;}     public virtual boolean isHappy(); }   Class  public class cat extends Animal implements iLove{    public cat(String nm){      animalName = nm;   }    public string pet(){     system.debug(animalName);             happy = true;     return 'prrrrrrr';   }    public override boolean isHappy(){     return happy == null ? false : happy;   }  }   So, if I instantiate like this:  Animal a = New Cat('Fred');   I do not have access to the method pet() since Animal does not implement pet  Doing this:  iLove i = (iLove)a;   I can now can execute pet()  However, if I instantiate like so:  iLove i = New cat('Fred');   Executing pet() debugs the animalName and there is no access to isHappy() or animalName directly  Now, the goal is to have many Animals that have a common definition (Animal) that may have different interfaces. for this example each one implements their own pet method, Dog - Bark, Lion - Roar, etc.  Is there a better way to handle all of this where I would not have to Instantiate Animal and then cast to iLove  Goal would be one line for instantiation where I would have access to the properties in Animal as well as the methods of the interface without having to do  Cat c = New Cat('Fred');   As obviously that would work but then it cuts out the whole point of the interface....  Is the casting of the SuperClass to the Interface the way to go about it?  Should I just define the abstract methods in the abstract class. If so what is the point of the Interface. I would suspect in this case it may not be needed but could be used if other classes which to interact with the cat without having to worry about the Animal class.  Thoughts?  Putting the interface on the Animal class has similar effects...


I have a desktop running Ubuntu 18.04 with Gnome, and two monitors. The screen does not automatically go blank or lock itself. I can manually lock the screen, but if I, say, go to bed, when I wake up in the morning the screen is still as I left it. Through Settings-> Power -> Power Saving, I have 'Blank Screen' set at 10 minutes, but that doesn't happen.   I'm not sure where to start trying to investigate what is going wrong. How do I get my screen to  go blank? I don't really care whether it locks or not, I just do want it to turn off my monitors.

is it possible to set different blank screen timeouts in Ubuntu 18.04 with Gnome when on battery or ac? The power settings menu provides only one field which is applied always, no matter of the current mode.  This question was already asked for the Unity desktop a while ago () and they did not find a solution but I had the hope that that might have changed with Gnome now.


I am using a ua741 op-amp. My question is, how can I use a potentiometer to null the output offset voltage?  I believe if I'm correct, that output offset voltage means the output voltage provided by the op-amp even though no input voltage is connected. But I don't get how you can use a resistor to null the offset voltage.

What is Offset null in 1st and 5th pin in IC 741 (Op-Amp)? Why it is used, though it is not used in many circuits? Give me explanation regarding the offset null! Why offset voltage was formed in IC 741?


I have Ubuntu 18.04.1 LTS and trying to execute "poweroff" as a sudoer but without needing to enter the password.   I added this line to visudo:  nurp    ALL = NOPASSWD: /sbin/poweroff   It gives this error:  nurp@nurp-OptiPlex-7040:~$ poweroff Failed to set wall message, ignoring: Interactive authentication required. Failed to power off system via logind: Interactive authentication required. Failed to open /dev/initctl: Permission denied Failed to talk to init daemon.   I tried sudo poweroff -f but then it asks for password. I just want to run a long script and poweroff after it finishes. I don't want to type password on the command line.

I recently found out that reboot works just as well as sudo reboot, from what I can tell. However, in a lot of instances, I see people saying to sudo reboot. Why is this? Are they the same, and just personal preference? Or are they different? Does sudo reboot do more than reboot?


I am a bit new to git and would like some help with this. so here is what happened. I have a total of 6 commits in a branch, now I need to reset any changes made by me to specifically 2 files- abc.txt and xyz.txt  How can I achieve this? any help on this is highly appreciated. Thanks in advance.

I have made some changes to a file which has been committed a few times as part of a group of files, but now want to reset/revert the changes on it back to a previous version.   I have done a git log along with a git diff to find the revision I need, but just have no idea how to get the file back to its former state in the past.


I've noticed that, any time I try to pick up Peskin and Schroeder, the main stumbling block it the leap in mathematical constructs from QM. Is there a good textbook that could teach me some of the math I need to know (advanced properties of Fourier transforms, vector integration tricks, etc.) to get a foothold on this?  I noticed this question might be misleading; I am not looking for a mathematical-physics take on QFT, anything regarding rigorous abstract algebra, topology, etc. Mainly I'm looking for what might be the textbook between the level of undergraduate and graduate math curriculum that contains principles used in introductory QFT.  Again, I am not trying to answer this question . I am an engineer with a decent background in QM but I can't understand the math in QFT. I am not looking for a mathematical approach to QFT as I would be hopefully lost, I am looking for a source to give me the mathematical pre-requisites for QFT.

I'm a student of mathematics with not much background in physics. I'm interested in learning Quantum field theory from a mathematical point of view.  Are there any good books or other reference material which can help in learning about quantum field theory? What areas of mathematics should I be familiar with before reading about Quantum field theory?


Of late, I've noticed that many web sites seem to be using light grey text for many sections of their sites. Some such sections include - the text (link, usually) that shows in the status bar at the bottom of the browser when you hover the mouse over a link on their page, the indicator text in form fields to be filled in (e.g. the word "email" in the email address field), and many other elements on the page.  That light grey makes it much less readable.    Not sure whether is a new trend, or something to do with my browser settings (I haven't changed them lately, AFAIK), or Google Chrome, which is my browser. This is on Windows 7 running on a Dell Vostro laptop. I added the info about the laptop because I suspect the problem may even be due to my hardware settings, since I found the default brightness to be too high after I bought it, and changed it via Control Panel.  Would like to know what are some of the things I can check or change to solve this.  Thanks.

I would like to be able to change the default CSS used by chrome, such as removing the underlines for links, etc. However, I cannot find the default CSS file used by Chrome. Does anyone know where it is?


My F1-F12 keys have all sorts of multimedia buttons on them (volume, brightness, wifi, etc). But I am working in a 3D application which uses F1-F12 heavily, and I do not want to have to press fn+F9 for example as thats slows my productivity down considerably.   How can I get round this?   I went into BIOS hoping there would be an option to swap fn and multimedia keys, but I looked everywhere and there was one. Just a fn + control key swap which I don't need.  System is Lenovo ThinkPad with Windows 7 (ubuntu dual boot but I mostly use win7).  UPDATE - I have updated to the latest BIOS (from 2.26 to 2.29) from Lenovo website to no avail. Still no such option to change fn behaviour under BIOS.

I just have bought a new Lenovo Ideapad S400u notebook, and it is not default F1-F12, it is default mute button, refresh, more brightness, less brightness...  I've downloaded "Lenovo Keyboard Slim Fn Switcher" or something like that, but it didn't work.  Then, how can I change Fn function to get my F1-F12 buttons? I'm running Windows 8.1.


Let $n>1$ a number and $\zeta_n$ the the $n$-th root. $p$ be a prime. I'm looking for strategys & theorems which allow to calculate the minimal poplynomial $m_{\zeta_n}$ of $\zeta_n$ over $\mathbb{F}_p$. (the case $n=p-1$ is boring).  first of all since the cyclotomic polynomial $\Phi_n(X)$ is the minimal polynomial of $\zeta_n$ over $\mathbb{Q}$ with coefficients in $\mathbb{Z}$ we apply the reduction modulo $p$ and see that $m_{\zeta_n}$ divides $\overline{\Phi_n(X)}$ with $\overline{\Phi_n(X)}$ the image of $\Phi_n(X)$ under reduction map $\mathbb{Z}[X] \to \mathbb{F}_p[X]$.  are there some irriducibility criterions? for example I found : see Bruno Joyal's answer following statement:  the cyclotomic polynomial $\Phi_n(X)$ is irreducible over $\mathbf F_p$ precisely when $p$ has multiplicative order $\varphi(n)$ modulo $n$.  could anybody give the reference where it is proved or a sketch of it if it's not too deep?  do there exist another nice theorems treat this question?

I want to know if there is a way to decide if a cyclotomic polynomial is irreducible over a field $\mathbb{F}_q$?


A few days ago I was working in Matlab when suddenly Matlab crashed. My screen then switched to a strange resolution of which I couldn't alter the settings. Therefore, I decided to reboot. Grub now also has a much smaller resolution than normal. After I press enter the screen turns off and shows a message that it isn't receiving a signal.  I've had problems with CUDA and Nvidia drivers before. After installing a driver I had a similar problem, except that the screen had a signal and had a white blinker in the top left corner. Another difference is that now I've had the Nvidia driver and CUDA working for a long time, and all of a sudden without installing or updating it, it has stopped working.  I've tried replacing quiet splash with no splash, after which I do get to see the Ubuntu logo, but afterward the no signal sign appears once again. I've also tried replacing quiet splash with nomodeset, same result except I now saw a purple screen before the no signal sign of my monitor.  Other solutions I've looked at tell me to open up a terminal, which I've tried but have failed to do so. I'm now a bit lost. What steps do I take next? The last time I reinstalled Ubuntu entirely. This time around I have a small part of my thesis on my computer, and I'd like to save it!

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


The Basic Rules state that you can get a possible bonus action. Is this entirely up to the dm or are there circumstances where it is guaranteed? Players handbook doesn't include the bonus action.

We were trying to understand how the "Action Surge" rule works, and after some discussion we came to a standstill.      Starting at 2nd level, you can push yourself beyond your normal limits for a moment. On your turn, you can take one additional action on top of your regular action and a possible bonus action   The keyword "possible" is what threw us off. Half the group thought it meant "additional action or bonus action", and the other half thought it was "additional action and bonus action".  So which is it?


I have a Python script which takes as input a list of integers, which I need to work with four integers at a time.  Unfortunately, I don't have control of the input, or I'd have it passed in as a list of four-element tuples.  Currently, I'm iterating over it this way: for i in range(0, len(ints), 4):     # dummy op for example code     foo += ints[i] * ints[i + 1] + ints[i + 2] * ints[i + 3]  It looks a lot like "C-think", though, which makes me suspect there's a more pythonic way of dealing with this situation.  The list is discarded after iterating, so it needn't be preserved.  Perhaps something like this would be better? while ints:     foo += ints[0] * ints[1] + ints[2] * ints[3]     ints[0:4] = []  Still doesn't quite "feel" right, though.  :-/ Related question:


my fridge went out. It was a good 2 days that the temp inside of the fridge wasn't too warm but it wasn't cold either. I took most of the contents out and placed them on ice. A whole day and a half past and Well my fridge finally came in, however the ice melted and I thought I stacked it well but when i woke my eggs were completely submerged in the water. The ice was packaged and from the store. Do you think my eggs are still good to consume?

If I left food out of the refrigerator for some period of time, is it still safe? If I left it out too long, can I salvage it by cooking it more?


Welcome to the world after .  We've patched our servers and are replacing our SSL certificates.  But just because our servers are fixed, that doesn't mean that the rest of the internet is fixed.  We have employees, and they use the internet to exchange secrets such as credit card numbers and logon credentials.  They are looking to us for advice.  We can advise our clients to use  to see if the site they want to go to has the vulnerability.  If a site returns positive, then don't exchange secrets with it.  But if a site does not return positive for Heartnet, then the situation may be any of:   The site never had the vulnerability (good) The site had the vulnerability and has fixed it, but is still using the possibly compromised SSL certificate (bad) The site had the vulnerability and has fixed it, and regenerated the SSL certificate but without regenerating keys (bad) The site had the vulnerability, fixed it, regenerated keys, and replaced the SSL certificate. (good)   Is there any means we can give our employees, before they type their credit card number into the form, to tell the good scenarios from the bad ones?  How do we instruct our employees to minimize their exposure to servers which are compromised by Heartbleed?

This is a  about understanding and remediating the Heartbleed security issue.   What exactly is CVE-2014-0160 AKA "Heartbleed"? What is the cause, what OSs and versions of OpenSSL are vulnerable, what are the symptoms, are there any methods to detect a successful exploit?   How can I check to see if my system is affected? How can this vulnerability be mitigated? Should I be concerned that my keys or other private data have been compromised? What other side effects should I be concerned about?


My problem is that after I installed Ubuntu 14.04.5, I cannot visit through the label that is shown after the BIOS screen (the label is under the label of my Windows 10). Windows 10 is still running well.  The error says Windows failed to start. File: \NST\nst_linux.mbr. Status: 0x000007b.  I installed Ubuntu using the method of 'something else', since I want to install it in another hard drive, which is HDD from my SSD where windows 10 is located. Here is a picture of my disk management, in which we can see disk 0 (C) is the windows drive (SSD), and disk 1 (D) is the HDD where I want to put Ubuntu in.    In disk 1, partition 1 is EFI, partition 2 is / mount point ext4 type. partition 3 is swap area and partition 4 is /home mount point ext4 type. And I chose the partition 1 (EFI, also sdb1) as Device for boot loader installation.  But as you can see from the image, all partitions I allocated for Ubuntu are 100% free and I do not know where Ubuntu is. This is the screenshot after I tried to install Ubuntu for many times, and every time I found they are still empty.  My booting configuration is: UEFI - secure boot off. I tried using EasyBCD, but got a warning like this:    So there is no way to add new entry for Linux option.   Still, I tried using Grub2 for Windows and clicked several operations (which I do not exactly understand), nothing helpful happened. The error is still there.  I have searched a lot instructions and videos online but it seems nobody has the same problem like mine. Really appreciate if somebody can help me here.

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


are (non-rotating) black holes with electric charge. The Schwarzschild radius depends on their mass and charge. The metric is given by: $$ ds^2 = -\left(1-\frac{2M}{r}+\frac{Q^2}{r^2}\right)dt^2 + \frac{1}{1-\frac{2M}{r}+\frac{Q^2}{r^2}}dr^2+r^2d\Omega^2$$ If a certain ratio of these is achieved, the event horizon will be pushed to infinity. As can be seen, the charge of the hole contributes to the metric, but in a contrary way as the mass. I'm not sure I get this. If energy is equivalent to mass, shouldn't charge contribute in the same way as mass? Which would mean that the Schwarzschild radius becomes smaller instead of bigger? Won't the potential energy involved in the electrostatic repulsion of the parts of the charge be involved too (instead of the electric field only)? Which would mean that the radius shrinks even more? If the charges are confined, this energy would be rather large.

The Reissner-Nordstrom metric (in spherical coordinates and c = 1) differs from the Schwarzschild metric in a additive term $$\frac{GQ^2}{4\pi\epsilon_0 r^2}$$, so the metric is   $$ds^2 = \left(1 - \frac{2GM}{r} + \frac{GQ^2}{4\pi\epsilon_0 r^2}\right)dt^2 - \left(1 - \frac{2GM}{r} + \frac{GQ^2}{4\pi\epsilon_0 r^2}\right)^{-1} dr^2 - r^2d\Omega^2$$  This has an effect of "repulsion".   Why adding more energy (by the addition of charge to the black hole) has this repulsive effect? What is the physical meaning of adding charge to a black hole?


Imagine the following completely hypothetical scenario:  I have Chris Davis on my team (I am Dan Duquette).  I know that Chris will be a free agent next year, and I want to keep him.  I sign him to a multi-year deal that goes into effect next season - and doesn't begin until then.   At the trading deadline;  realizing I will not compete, I trade him to the Diamondbacks for Ken Griffey the Third, Alex Rodriguez's cousin, and a genetic clone of Pedro Martinez.  I do this knowing that next season Chris will be back, and The Orioles now have murderers row.  When the next season starts Chris's contract kicks in and he's an Oriole again.  I'm sure that this is illegal, but I can't find any mention of it on Google.  Does anyone know the rules (if any) referencing this type of situation?

Every season near the trade deadline, we see teams that are out of it trading expensive players and/or free agents-to-be, typically for younger players or prospects.  For example, Matt Garza, set to become a free agent after the season, was traded to the Rangers for a few prospects.  It made sense for the Cubs to trade Garza, because he wasn't under contract any further than this season, and thus doesn't have much value to them.  Compare Garza to someone like Mike Trout, who is likely the most valuable property in baseball, given his skill and inexpensive cost over the next several years.  There's no way the Angels would trade him, because he'll be the cost-controlled centerpiece of the team for years to come.  However, with the Angels out of it this year, what if they wanted to trade Trout to a contender (say the Pirates), but only for the remainder of this season?  That is, they'd get several top prospects now, and would have an agreement with the Pirates that they'd trade him back in the offseason (for something pretty worthless, say for a journeyman minor leaguer).  The Pirates get Trout for the stretch run and are happy to give up a few prospects.  Trout doesn't have much value to the Angels this year, but he has a ton of value for next year.  So they get a few prospects for him, in exchange for the part of his career which has very little value to them.  So in effect, the Pirates are renting or borrowing him for the remainder of 2013.  Why don't trades like this happen?  Are there any rules prohibiting trades like this?


I am looking for an explicit description of the additive, multiplicative group structure and automorphism group of the field with 729 elements.   Sorry for not being clear. I have no clue what does "explicit description" mean, but I am guessing that the underlying group might be cyclic, but I do not know how to give a proof.   For its automorphism group, What I have tried:  1). Comparing this with the Galois group of this field over $F_3$ which is cyclic.  2). I also know that Aut(Z_3） = Z_2, which is, in general, true for or prime fields. That is why I am guessing that the underlying additive group should be cyclic, then by the same method, I can show that the automorphism group is a cyclic group of order 728 probably.

I would like to construct a field with 729 elements. I know that $729 = 3^6$, and that I have to find an irreducible monic polynomial of degree 6 over $GF(3)$. I chose the polynomial $x^6 + 2x^2 + 1$, which I have verified (computationally) that it is irreducible over this field. However, I do not know how to proceed with the construction. Any hints?   Suppose I hadn't found this polynomial computationally. Is there an algebraic method of finding such polynomials when the degree is quite large? Or, at least testing for irreducibility in such cases?


How can I align a whole page content to beginning of page? I would like to prevent such situations, where there are huge distances between elements like lists or paragraphs (evenly distributed elements) because the next item didn't fit on this page:

If we use the book class, the output looks like the following screenshot.    But if we use the article class, the output looks better as follows.    The MWE is given as follows. Note: please enable -shell-escape!  \documentclass[12pt]{article}% please change to article and compare the output.  \usepackage{filecontents} \begin{filecontents*}{"article sample.tex"} \documentclass{article} \usepackage{lipsum} \begin{document} \lipsum[1-20] \end{document} \end{filecontents*}  \usepackage{showexpl}  \lstset {     breaklines=true,     breakindent=0pt,     tabsize=2,     columns=flexible,     language={[LaTeX]TeX},     basicstyle=\small\ttfamily\hbox{}, }  \newcount\x  \newcommand\MyLTXinputExample[2][2mm]{% % #1: length of gap, % #2: filename with .tex,      \lstinputlisting[caption=\url{#2.tex}]{"#2.tex"}     \bgroup         \parskip=#1\relax         \fboxsep=0pt         \pdfximage{#2.pdf}%         \x=0         \loop             \ifnum\x<\pdflastximagepages                 \advance\x by 1                 \noindent\hfill                 \fbox{\includegraphics[width=0.5\dimexpr\linewidth-4\fboxrule-#1\relax,page=\x]{"#2"}}%                                  \ifnum\x<\pdflastximagepages                 \advance\x by 1                 \hfill                 \fbox{\includegraphics[width=0.5\dimexpr\linewidth-4\fboxrule-#1\relax,page=\x]{"#2"}}%             \fi                 \hfill\null\par         \repeat     \egroup }  \PassOptionsToPackage{obeyspaces}{url} \usepackage{hyperref}  \begin{document} \immediate\write18{pdflatex "article sample"} \MyLTXinputExample{article sample} \end{document}   How to prevent book class from vertically justifying the contents? In other words, I want to use the book class but its output (only the justification is under consideration) must look like the output that article class produces.


Here is a problem I've been working on. I am stuck and wondered if you guys could shed any light.  Let $a>0$ and $u_{1}>a$.  Consider the sequence $(u_{n})_{n=1}^{\infty }$ defined by:  $$ u_{n+1}\: :=\: \frac{1}{2}(u_{n}\:+\:\frac{a^2}{u_{n}})\;\;\;\;\forall n\in \mathbb{N} $$  Show that the sequence is convergent and that:  $$ \lim_{n \to \infty}u_{n}=a $$  Thank you in advance guys,  Deborah

a) Let $a>0$ and the sequence $x_n$ fulfills $x_1>0$ and $x_{n+1}=\frac{1}{2}(x_n + \frac{a}{x_n})$ for $n \in \mathbb N$. Show that $x_n \rightarrow \sqrt a$ when $n\rightarrow \infty$. I have done it in two ways, but I guess I'm not allowed to use the first one and the second one is incomplete. Can someone please help me?  We already know $x_n \rightarrow \sqrt a$, so we do another step of the iteration and see that $x_{n+1} = \sqrt a$.  Using limit, $x_n \rightarrow x, x_{n+1} \rightarrow x$ (this is the part I think it's incomplete, don't I have to show $x_{n+1} \rightarrow x$, how?), we have that   $$x = \frac x 2 (1 + \frac a {x^2}) \Rightarrow 1 = a/x^2 \Rightarrow x = \sqrt a$$ b) Let the sequence $x_n$ be defined as $x_{n+1}= 1 + \frac 1 {x_n} (n \in \mathbb N), x_1=1$. Show that it converges and calculate its limit. "Tip: Show that sequences $x_{2n}$ and $x_{2n+1}$ monotone convergent to the limit." I didn't understand the tip, how can this help me? Does it make a difference if the number is odd or even? Thanks in advance!


I used to use Windows and Ubuntu on my pc. But I'm no longer a Windows user, now only Ubuntu. I tried to instal Ubuntu over the Windows, but grub still installed and asks every boot which system should it start. Theres a way to remove completly and start straight on Ubuntu?

I searched the Internet for instructions on how to remove , but the only thing I could find was using a Windows DVD to "repair" the system. I previously had a Windows/Linux doal-boot and removed Windows ( + ), but GRUB is still installed with only one entry: the Linux one.  How can I uninstall GRUB and directly boot on a -based OS?


I'm trying to create a cep program that is able to detect when a user's salary change.so i wrote this code   Pattern     .<comptedata>begin("First Event").subtype(comptedata.class).where(             new SimpleCondition<comptedata>() {                 @Override                 public boolean filter(comptedata event) throws Exception {                     if (event.getoperation()!="virement"){                         return false ;                     }                     return event.getMontantop() != event.getsalaire();                 }             })     .followedBy("seconf Event").subtype(comptedata.class).where(             new SimpleCondition<comptedata>() {                 @Override                 public boolean filter(comptedata event) throws Exception {                     if (event.getoperation()!="virement"){                         return false ;                     }                     return event.getMontantop() != event.getsalaire();                 }             });   but it gives me this error  Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/flink/api/common/ExecutionConfig$ClosureCleanerLevel     at org.apache.flink.cep.pattern.Pattern.where(Pattern.java:159)     at myflink.cep.changePattern.getEventPattern(changePattern.java:19)     at myflink.app.toWarningStream(app.java:69)     at myflink.app.main(app.java:52) Caused by: java.lang.ClassNotFoundException: org.apache.flink.api.common.ExecutionConfig$ClosureCleanerLevel     at java.net.URLClassLoader.findClass(URLClassLoader.java:382)     at java.lang.ClassLoader.loadClass(ClassLoader.java:424)     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)     at java.lang.ClassLoader.loadClass(ClassLoader.java:357)   I understood from this question () that there is a class file that my code depends on and it is present at compile time but not found at runtime, however flink-core already exists in my project structer i tried to make it at runtime instead of compile but It doesn't solve the problem I don't know what should I do

I am getting a NoClassDefFoundError when I run my Java application.  What is typically the cause of this?


I'm making a Python irc bot. For some reason the yield statement in my join() method makes it skip the method altogether, but if I replace it with a return it works fine. However, I need to yield an error per each unsuccessful join attempt.  I have a join method of the bot that returns a server error command code response if the join is unsuccessful for some reason. It's None if the bot joins successfully.  unsuccessful = bot.join(channels)   I would be able to do:  if unsuccessful:     for error in unsuccessful:         print(error)   The join method looks like this  def join(self, channels):     chan_errors = range(471, 480)  # See RFC for commands 471-479      if isinstance(channels, str):         channels = [channels,]      for channel in channels:         self.send('JOIN %s' % channel)         for response in self.get_response('JOIN', chan_errors):  # Verify             if response.command in chan_errors:                 channels.remove(channel)                 yield response     self.channels.append(channels)   If I switch the "yield response" with "return response" it runs the method.   The get_response method looks like  def get_response(self, commands, terminators=None):     for msg in self.msg_gen():         self.handle(msg)         if msg.command in commands:             if terminators is None:                 return msg             yield msg         if msg.command in terminators:             return msg   It receives messages from a message generator. The commands are the server command the caller is looking for and the terminators drop out of the generator when one is found. It's sort of like a coroutine.  Does anyone know what is happening here?

What is the use of the yield keyword in Python? What does it do? For example, I'm trying to understand this code1: def _get_child_candidates(self, distance, min_dist, max_dist):     if self._leftchild and distance - max_dist < self._median:         yield self._leftchild     if self._rightchild and distance + max_dist >= self._median:         yield self._rightchild    And this is the caller: result, candidates = [], [self] while candidates:     node = candidates.pop()     distance = node._get_dist(obj)     if distance <= max_dist and distance >= min_dist:         result.extend(node._values)     candidates.extend(node._get_child_candidates(distance, min_dist, max_dist)) return result  What happens when the method _get_child_candidates is called? Is a list returned? A single element? Is it called again? When will subsequent calls stop?   1. This piece of code was written by Jochen Schulz (jrschulz), who made a great Python library for metric spaces. This is the link to the complete source: [Module mspace][1].


Let $\mathcal{A}$ be an additive category. And let $C(\mathcal{A})$ be the category of the chain complexes. Now let $f:X_* \rightarrow Y_*$ be a chain map in $C(\mathcal{A})$ and $C(f)$ be its mapping cone. As we've already known, there's a proposition:     If $C(f)$ is contractible, then $f:X_* \rightarrow Y_*$ is a homotopy equivalence.   My question: Is the inverse problem true? To be explicitly, if $f:X_* \rightarrow Y_*$ is a homotopy equivalence, then does $C(f)$ necessarily to be contractible? I guess that this is not true in general for a part of the proof of the proposition doesn't holds conversely. Am I right? If I'm right, is there any counterexample? Thanks in advance.

Let $f: K^\bullet \to L^\bullet$ be homotopy equivalence. From theory of triangulated categories it follows that $C(f)^\bullet$ is contractible. But how can i produce explicit formula for homotopy of $Id_{C(f)^\bullet}$ and $0_{C(f)^\bullet}$?


The  states:  The average squared deviation is typically calculated as x.sum() / N, where N = len(x). If, however, ddof is specified, the divisor N - ddof is used instead. In standard statistical practice, ddof=1 provides an unbiased estimator of the variance of the infinite population. ddof=0 provides a maximum likelihood estimate of the variance for normally distributed variables. The standard deviation computed in this function is the square root of the estimated variance, so even with ddof=1, it will not be an unbiased estimate of the standard deviation per se.  (emphasis added) What does the final statement in bold mean?  Where does the estimate break down and become biased?

According to the Wikipedia article on  the sample SD   $$s = \sqrt{\frac{1}{n-1} \sum_{i=1}^n (x_i - \overline{x})^2}$$  is a biased estimator of the SD of the population. It states that $E(\sqrt{s^2}) \neq \sqrt{E(s^2)}$.   NB. Random variables are independent and each $x_{i} \sim N(\mu,\sigma^{2})$   My question is two-fold:   What is the proof of the biasedness? How does one compute the expectation of the sample standard deviation    My knowledge of maths/stats is only intermediate.


In an example, suppose we have a hypothetital infinite population of objects of two colors: red and blue, and we know the true proportions of each: $P(red)=0.3$ and $P(blue)=0.7$  Now, suppose I blindly draw objects at random and try to guess their color by using a random number generator which predicts red 30% of the time and blue 70% of the time.  What proportion of guesses are expected to be correct in a theoretical infinite sample? Intuition tells me 50%. If that is correct, why?

This is not homework. I am interested in understanding if my logic is correct with this simple stats problem.  Let's say I have a 2 sided coin where the probability of flipping a head is $P(H)$ and the probability of flipping a tail is $1-P(H)$. Let's assume all flips have independent probabilities. Now, let's say I want to maximize my chances of predicting whether the coin will be a head or tail on the next flip. If $P(H) = 0.5$, I can guess heads or tails at random and the probability of me being correct is $0.5$.  Now, suppose that $P(H) = 0.2$, if I want to maximize my chances of guessing correctly, should I always guess tails where the probability is $0.8$?  Taking this one step further, if I had a 3-sided die, and the probability of rolling a 1, 2, or, 3 was $P(1)=0.1$, $P(2)=0.5$, and $P(3)=0.4$, should I always guess 2 to maximize my chances of guessing correctly? Is there another approach that would allow me to guess more accurately?


How do you use terminal to enable Universe source? Or any those 4 from Software Sources: Main, Universe, Restricted, Multiverse Main is on by default and Restricted is on if durring Ubuntu installation i tick Enable Restricted Formats. Answer with line where version checked so it auto detects it. Like command I know for partner but that goes to Other Software tab sudo add-apt-repository "deb http://archive.canonical.com/ $(lsb_release -sc) partner"

How do I get to the Universe Repository in supported versions of Ubuntu?


I  just came across this question and thought if i could ask help. How do you solve problems that have powers with a negative number? Ex. 2^(-2)

This is what we are taught: $$5^{-2} = \left({\frac{1}{5}}\right)^{2}$$  but I don't understand why we take the inverse of the base when we have a negative exponent.  Can anyone explain why?


Statistical significance of a (variable in a) model grows with sample size. Citing :  If one uses test statistics with constant size (i.e. a constant degree of confidence), almost any simple model will be rejected given a sufficiently large data set.   ...[On the other hand] any hypothesis can be maintained by testing it on a sufficiently short time series.  From a practitioner's perspective, this is troubling. Statistical significance is often used in convincing that a (variable in a) model is relevant; but once you know it grows with sample size, the argument loses much of its power.   is a related discussion (e.g. the answer by Mark Claesen).  Questions:  (1) How to overcome the sample-size-dependence of statistical significance?  (2) Can we adjust statistical significance to make it independent of sample size?  (3) What to use instead of statistical significance?   The goal is to find out whether a given (variable in a) model is relevant and useful.

I am working with a data set having N around 200,000. In regressions, I am seeing very small significance values << 0.001 associated with very small effect sizes, e.g. r=0.028.  What I'd like to know is, is there a principled way of deciding an appropriate significance threshold in relation to the sample size? Are there any other important considerations about interpreting effect size with such a large sample?


$\binom{n}{k-1} + \binom{n}{k} = \binom{n+1}{k}$  So far I have gotten $\frac{n!}{(k-1)!\big(n-(k-1)\big)!} + \frac{n!}{ k! (n-k)!}$  But I quickly lose myself once I have to start making the denominator equal. Help would be appreciated.   Sorry for the duplication, I am new to the site and didn't quite know how to look up my question.

Can someone explain to me the proof of $${n+1\choose k} = {n\choose k} + {n\choose k-1}$$?


There was a bit of a hubbub on , where some people thought links to gold-farming sites should not be allowed in profiles, while others thought they should.  I took the stance that they should be allowed, but that appears to be the less popular opinion.  However, according to  on meta.SO, and even according to , as long as there's nothing illegal or (too) offensive, profiles are pretty much anything-goes, including advertisements for your businesses.  So let me take it to an extreme:  if I have a site selling male-enhancement pills, and I do everything by the book (have the right paperwork, don't sell where it's illegal to sell, etc.), can I have a link to it in my profile?

Are there any rules concerning what I can put in my profile?


Can anyone show that:  $\mathbf{a_{\perp}}=\mathbf{a}-\frac{\mathbf{x}\mathbf{x}^T}{\mathbf{x}^T\mathbf{x}}\mathbf{a}$,  $\mathbf{a}\in\mathbb{R}^N$, $\mathbf{x}=(1,1,\dots,1)^T\in\mathbb{R}^N$  results in $\mathbf{a}$ becoming orthogonal to $\mathbf{x}$?  Thank you for your help.

I am given the vectors $\mathbf{w}, \mathbf{v}, \mathbf{u}$ in $\mathbb{R}^n$ such that $\mathbf{u} \neq 0$ and $\mathbf{w} = \mathbf{v} - \frac{\mathbf{u}\,\bullet\,\mathbf{v}}{\|\mathbf{u}\|^2}\bullet\mathbf{u}$. I am asked to show that the vector $\mathbf{w}$ is orthogonal to $\mathbf{u}$.     So far, I have written out the definition of orthogonal: two vectors are orthogonal if and only if their dot product is zero.   So what we need to prove is $\mathbf{w}\bullet\mathbf{u} = 0$ where $\mathbf{w}\bullet\mathbf{u}$ is defined as $\mathbf{w}^T\bullet\mathbf{u}$.   However, I have been stuck on this problem for about an hour and haven't made any significant progress from here. How do we go about proving that the vectors are orthogonal?


I got to the highest level of trust of one of my companions. Now I'm curious if there are disadvantages to doing the same with a different companion to get their perk as well.  Do I lose the perk from the first companion? Do I slowly lose karma with them if not traveling with them?   Is there any negative side effect, or should I just run around as a two-faced chameleon gaining the perks from all of them I can?

Every companion provides a unique perk. I read that you gain the perk after you reach positive reputation with your follower.  Is the perk permanent after you unlock it with reputation (stays active even after you dismiss the follower)?  Do you loose the perk if reputations drops after maxing it out?


What is the difference between  "I'll go to the sea." and  "I will be going to the sea."  If it's ok with you, could you tell me how to use these?

Non-native speakers often get confused about what the various tenses  and aspects mean in English. With input from some of the folk here I've put together a diagram that I hope will provide some clarity on the matter.  I offer it as the first answer to this question. Consider it a living document. Input is welcome, and good suggestions will be  incorporated into the diagram.    Nota bene: What this is not is a discussion of whether there are  more than two tenses in English. , to which this question is not intended to supply arguments one way or the other.  Here, the aim is to provide an overview of what constructions English-speaking people use for conveying information about actions referring to past, present, and future, and to provide it first and foremost to precisely the people who are likely to use "tense" as a catch-all term in their search, rather than to linguists who know better.  Breaking News There is now an excellent ELU blog article titled  . It is highly recommended reading.


I have windows 10 running on my laptop. I have connected stereo speakers to it via the existing 3.5 mm audio jack.  I want to connect one more speaker via Bluetooth and want to play the same content on all of the speakers simultaneously or if that is impossible I would be equally satisfied even if I am able to play some different content in the Bluetooth speakers via my laptop and different content on stereo speakers simultaneously.  Now how do I do this? Without extra hardware.  Highly appreciate your help!

I have a hearing impaired person in the house and want to equip her with a bluetooth headset while the rest of us listen over the speakers. I am able to connect the headset and get it to play by setting it as the default speaker. Problem is that the speakers are then turned off.  Working with windows 7 and Samsung bluetooth headphones.


I panicked when changing a lens and forgot to turn the camera off, I realised before fitting the other lens, I worried I’ve done damage as it states in the manual no turn it off first although everything seems fine. I am a worrier though but what are the chances I’ve done damage? I have a brand new D7200 so you can see why I’m concerned.

I have just accidentally changed my lens over with the power on. In the manual it lists this as something you shouldn't do as a 'caution' . Can this cause damage? If so, what and how will I tell?  (I have an Olympus OM-D.)


I have the habit of everytime someone answers/comment one of my questions, i go trhu their list of questions and see if I can answer/contribute to any of the unanswered ones.  A few days ago I started to have some trouble on windows and the users answering windows questions have lots of answers and reputation, but zero questions.  I thought everyone had to ask questions to even start to be able to reply... Or do they delete their old questions for some reason?

Why do some people not ask questions on SO? If it is only for reputation (which basically boosts their CV), they could instead do some investigations in spheres that interest them. So what's the point in only answering questions? Training to become a consultant?


I'd like to use the Greek letter qoppa in a formula in an otherwise non-Greek document. I tried using the greekoption for babelbut that turned my document into Greek letters. By default, \qoppadoesn't seem to be defined.

Since I have switched to the 2014 texlive, one issue is not working: the character \qoppa. The command is defined in polutonikogreek in babel. It is an archaic greek letter, but was used also in classic times for the number 90.  The glyph is available in the cmr font and in MinionPro and in the beautiful MinionMath font of Johannes Küster. I want the latter. In MinionPro/MinionMath, it is unicode character 03d9 (formerly u+03DE, it recently changed, as it turns out), see   How do I get the glyph into latex? I tried  \def\testqoppa{\begingroup\fontfamily{MinionPro}\fontencoding{LGR}\selectfont\char19\endgroup}   and   \def\testqoppab{\begingroup\fontfamily{minionmath}\fontencoding{LGR}\selectfont\char19\endgroup}   But all this gives the cmr glyph, because latex complains  LaTeX Font Warning: Font shape `LGR/MinionPro/m/n' undefined LaTeX Font Warning: Font shape `LGR/minionmath/m/n' undefined (Font)              using `LGR/cmr/m/n' instead on input line 571.   This seems like a beginner error from my side. Can somebody help me to get it right? I need \qoppa only in two places, so a nasty trick is also sufficient. The MinionMath font is installed and is working for all other purposes. Here is an extract of the .cls file:  \usepackage[fullfamily,textlf, opticals, swash, onlytext]{MinionPro} \usepackage[extraops,textcomp,withamsmath,amssymb]{minionmath} \usepackage{amsmath}             \usepackage{minionamsmath} \usepackage[polutonikogreek,greek,latin,french,italian,german,british]{babel}


var str = ' some value, 1, 2 , test3';     str +="test string, 12, test12";       var varArray = new Array();    varArray = str .split(",");    if(varArray[i] == '' || varArray[i] == "")    {     //some logic     }   I have referred this piece of code from some blogs. I am curious, is there any difference in both comparison in if condition . is it specific to browser. Please help me to know the reason of using this. or both are same.

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 would like to know what Lucy, Mary and a third person  think - taking into account they might have different opinions. Would the following sentence be correct?  I would like to know Lucy's, Mary's and your thoughts on this issue.

If I was to label something      The Poets and Painters' Distillery    do I only apply the possessive apostrophe after 'Painters' as in the text written above, or do I also need to apply one to 'Poets' so that it becomes      The Poets' and Painters' Distillery ?    I'm thinking the former is correct, but cannot be too sure.


In your field of research, what is the significance of the corresponding author?   Does the title "corresponding" imply that the person is the expert out of the list of all authors, or that the person is responsible for communicating with the journal / reviewers?   When should the PhD student, if she/he is set as the first author, also be the corresponding author?

After reading the question , I got the impression that (at least in the writers' field) the "corresponding author" flag could carry an implied meaning, such as "did more work than the other authors", or "is a more senior author". Is it the case?  I am in mathematics, a field where we typically sort the authors alphabetically, and I've never given any importance to that role (apart from "this author is willing to answer a couple of extra e-mails, if needed").


Are there cryptographic hash functions that have homomorphism-like properties?  E.g. satisfying following relation $h(a || b) = h(a) · h(b)$, where $h(x)$ is hash function itself, $x || y$ is concatenation and $x · y$ is some hash-specific combination function making single hash given two of them. If that makes any difference, it can be also assumed $a$ and $b$ are of equal length, and $h(x)$ is expected to produce hash sums of same length regardless of $x$.  I can think of basic, non-cryptographic example — $h(x)$ can be plain arithmetic sum of character codes modulo 256, and $x · y := (x + y) \bmod 256$, so  $$ h(\texttt{"foo"}) = (102 + 111 + 111) \bmod 256 = 68 $$  $$ h(\texttt{"bar"}) = (98 + 97 + 114) \bmod 256 = 53 $$  $$ h(\texttt{"foobar"}) = (102 + 111 + 111 + 98 + 97 + 114) \bmod 256 = 121 $$  $$ h(\texttt{"foo"}) · h(\texttt{"bar"}) = (68 + 53) \bmod 256 = 121 $$  So, is there something similar, but with high collision resistance?

A  is a function $H : A \to B$ between two sets with some algebraic structure $(A, *)$ and $(B, \star)$ such that   $H$ is collision resistant, i.e. it is hard to find $x \neq y$ such that $H(x) = H(y)$ and $H$ is a homomorphism, i.e. $H(x * y) = H(x) \star H(y)$.   Are there any practical realizations of such a homomorphic hash function, or even a homomorphic signature scheme (i.e., where we can "add" valid signatures to get a signature of the "sum" of two messages)?  Even better, are there even any libraries implementing this?


Why indefinite integral has such a notation ? What part "dx" has to do with the indefinite integral, and why f(x) is multiplied by it ?

When I was at school and learning integration in maths class at A Level my teacher wrote things like this on the board.  $$\int f(x)\, dx$$  When he came to explain the meaning of the $dx$, he told us "think of it as a full stop".  For whatever reason I did not raise my hand and question him about it.  But I have always shaken my head at such a poor explanation for putting a $dx$ at the end of integration equations such as these.  To this day I do not know the purpose of the $dx$.  Can someone explain this to me without resorting to grammatical metaphors?


I have been looking around the web for guides on how to install a new font for LaTeX with PDFlatex. There are plenty of guides, but I have a hard time trying to follow them.  At the moment I have the following files and file structure:  -pwb(walbaum)   -fonts     -afm       -abobe         -walbaum           <18x .afm files>     -enc       <empty>     -map       <1x .map file>     -tfm       -abobe         -walbaum           <60x .tfm files>     -type1       -abobe         -walbaum           <18x .pfb files>     -vf       -abobe         -walbaum           <30x .vf files>   -tex     -latex       -abobe         -walbaum           <4x .fd files>           <1x .sty file>   So what is the next steps to be able to use the font? Where should I put the files, etc? And will I be able to use it for math equations?  If you can explain it in a simple way, I would be glad.  Bonus info: I am using TexMaker and PDFLatex on a Mac.

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?