I'm reading a book on the , and the author gave a "5-line proof" of Fermat's Last Theorem as a way to introduce the topic of inconsistency in set theory and logic. The author acknowledges that this is not a real proof of the theorem, but the way it was presented implies that it was supposed to look somewhat convincing. I, however, have absolutely no idea how the proof given even remotely relates to FLT, and would greatly appreciate it if someone could make the connection for me. Below is an almost verbatim excerpt from the book.   Theorem: There are no positive integers $x$, $y$, and $z$, and integer $n>2$, such that $x^n + y^n = z^n$.  Proof. Let $R$ stand for the Russell set, the set of all things that are not members of themselves: $R= \{x : x \notin x\}$. It is straightforward to show that this set is both a member of itself and not a member of itself: $R \in R$ and $R \notin R$. So since $R \in R$, it follows that $R \in R$ or FLT. But since $R \notin R$, by disjunctive syllogism, FLT. End.

I think that the question is contained in the title. Suppose we begin from something that is false for example $1=0$. Is it possible using only $\Rightarrow$ (and of course $\lnot ,\wedge,\lor$)  to prove any possible statement? It has been ages since i studied logic at the university so i would prefer a simple explanation (if possible)


I have tried everything to adjust and fix the sensors on my garage door. They will not close when the sun is hitting them. Can I just remove them?

Only during summer and only when the sun is close to the horizon the light from the sun confuses my garage door opener and in order to close the door I have to hold down the wired button which is a real pain if I'm leaving.  A friend suggested I use toilet paper rolls (or maybe some PVC) to shield the sensor from the sun and direct the beam to the other sensor and that's a good idea but it'll mean I have to change how the sensors are mounted to the track and move them out a bit.  Just moving them back might solve the problem (since they'll be blocked by the walls).  Any other suggestions? Is this a common problem?


Me and my husband were granted single entry schengen visa and our country of entry and exit will be Italy. We are travelling in August, 2016 and are confused by what actually single entry means. We are also planning to visit other countries like Switzerland and Germany and back to Italy to fly back home.  Our understanding was, we can enter schengen area once ( in this case through Italy) and if we don't go outside the schengen regions (that includes all 22 countries) it will cause no problem even if we try to enter one country more than once.  Please can one clarify this to me? Thanks a lot.  Marina

I am visiting a friend in Switzerland for ten days. I have already got visitor's visa for the same on my Indian passport. Particulars mentioned on my visa are:  1. 'Etats Schengen' , 2. Single entry 3. Dates of visit. & 4. Type of visa : C.  I understand that having already got ‘Etats Schengen' visa, I can travel to all Schengen countries.  I am also planning to visit Paris for a day during my stay in Switzerland. However, I never mentioned this in my visa application. I am planning to take a train from Geneva to Paris and book a hotel in Paris for one night. Can I possibly plan my Paris trip this way as I have Schengen visa, or I am not allowed to travel out of Switzerland as I never mentioned this in my visa application?   Also what does Single entry on my Schengen visa means: does it mean that I can enter and leave Switzerland only once or it means that I can enter and leave the Schengen region only once.


I realize that your suppose to accept an answer if it worked for you. What if you have a high up-voted , but the answer was found through the comments? Do I ask the user who made the comment to post it as an answer? How important is it to accept answers for all your questions? Is it worth begging users from the comments section to post the answer from the comments section to post their answer as a official answer?   One possible problem  Some users feel answers in the comment section are easy answers and don't deserve to be answered. What do I do in this case. Delete the question?

I am relatively new to SO and see this very often. As the title suggests there are many questions that are answered in comments itself and they remain unanswered forever. Shouldn't there be an option to mark a comment as an answer and the comment is copied over as an answer or something like that?  I guess there should be an option to the creator of the question to do this.


I'm confused of what $\sqrt {3 + 4i}$ would be after I used quadratic formula to simplify $z^2 + iz - (1 + i)$

If I'm given a complex number (say $9 + 4i$), how do I calculate its square root?


Words like row and rank imply that people/things are arranged horizontaly (beside each other), while words like queue and column imply a vertical positioning (behind each other). I need a word that can stand for either regardless whether the positioning is horizontal or vertical. Does it exist in English?

Is there a single, more generic term that can be used to describe both a row and a column? In English, we can refer to a line as being horizontal or vertical, but unless we say ‘a line of something’, that implies a one-dimensional line—it doesn't communicate a row or a column of things. So what could we say instead…? A horizontal or vertical _______?


Let's say i have a string.  "Hello this is a "string need" to split"   I need to get he output as   Hello this is a string need to  split   Any help would be appreciated.

Using SQL Server, how do I split a string so I can access item x?  Take a string "Hello John Smith". How can I split the string by space and access the item at index 1 which should return "John"?


I want to use a Mac Pro on the display of a MacBook. That's because I mainly use MacBook and now would like to use Mac Pro only when I need more power.  But since I'm a traveler for all year round, there is no choice to use iMac or MacBook Pro.  So is it possible to use the display, keyboard, and trackpad of a MacBook to use Mac Pro?

I just bought a new late 2013 iMac and a new late 2013 Macbook Pro retina. Also bought an Apple thunderbolt cable.  Pressing CMD+F2 (enabling Apples "Target Display Mode") on my iMac lets me use the iMac as external monitor for the MB Pro, but I'd like it the other way around (which doesn't seem to work).  Does anyone know how I through Thunderbolt (for speed, am aware that apps like  and Screen Recycler can do it through WiFi) so that my MB Pro becomes an extra external monitor for my iMac?  While  addresses this problem for earlier hardware and software, I'm looking for a solution that supports using a thunderbolt cable and works with late 2013 Macs with OS X Mavericks.


I know that the following maths and factorials properties are useful in my problem but I don't really know how to actually get them into it a rigorous way:  $2\times 2^n=2^{n+1}$  $((n+1)!)/(n!)=n+1 $  So I did  $2((2n)!)≥2\times 2^n(n!)^2$  $2((2n)!)≥2^(n+1)(n!)^2$  But then I don't really know what to do for the $2((2n)!)$ and the $(n!)^2$; how to get them to have n+1

I am trying to use mathematical induction to prove  $$(2n)!\ge2^n(n!)^2\quad\text{for }n\in\mathbb{N}$$  I am stuck at the $n=k+1$ point.


How do you mine obsidian in a cave without it falling into lava?

When I'm mining Obsidian I keep either missing the broken block and watching it burn up in the lava, or dying when I try to catch the broken block. Why? I keep falling in lava below – is that the problem? I'm new to Minecraft.


Rewatching 'The one in Barbados' episode of 'Friends' TV series, I stumbled upon a joke that seemed to sail over my head the first time I heard it.  Joey: No, God, no! No! No no, I'm an actor. You'd probably recognize me from a little show called "The Days of Our Lives" Ross: Dude, it's just "Days of Our Lives"... there's no the.  Could anyone please clarify if Joey deliberatly attached the definite article 'the' to the TV show name to give a ring to it, as if he was more than sure the name of the show alone would impress the listener, or he merely made a technical mistake, not implying anything of the above? Here is the follow-up question: could appending the definite article 'the' to the name possibly attach importance of any sort or solidity for that matter to it?

In the show 'Friends' there is an exchange between Ross and Joey that goes like this:     Joey: I'm in this show called 'The Days of Our Lives'.   Ross: Dude, it's just 'Days of Our Lives'. There's no 'the'.   Sadly, I fail to see humor in this and it's most likely due to my poor understanding of the many meanings of the article 'the'.  I also think understanding this joke could make me understand how the reception of the name "The Facebook" differs from just "Facebook" (the site used to be called thefacebook.com in the past, there's even a mention of that in the movie "The Social Network").  Could you help me understand this, please?


I'm using the python console of QGIS 2.8.1-Wien. I have a shapefile with many fields in the table that I want to remove them. I tried to use this geoalgoritm as:  processing.runalg('qgis:deletecolumn', myshapefile.shp, "myfield", myoutput.shp)    This works perfectly and the field I want is removed. My question is: if I want to remove more than one fields how should I write this formula? Or there are any other way to write a python script?    I used your 1st method, just for one shapefile as:  output_0=processing.runalg('qgis:deletecolumn', "D:/PATRICIA/ECMWF/Test/TPrecip_20140628_VERAO_join9.shp", "Lat_dec", None) output_1=processing.runalg('qgis:deletecolumn', output_0, "Lon_dec", None) output_2=processing.runalg('qgis:deletecolumn', output_1, "Altitude", "D:/PATRICIA/ECMWF/Test/TPrecip_20140628_VERAO_join12.shp")  The result was:"Error: Wrong parameter value: None"  I tried to use the 2nd method for 3 similar shapefiles (with same fields) activated in the table of contentes but just occured de removal of the fields in the 1st shapefile :  layer = qgis.utils.iface.activeLayer() res = layer.dataProvider().deleteAttributes([1, 2, 3, 4, 5, 6, 7, 8]) layer.updateFields()                         In this case it's impossible to use 8000 shapefiles activated in map canvas.  Any help?

How to remove or delete column fields in a shapefile using Python?


I am trying to remember the name of a book of short stories. It was a very thin paperback, with only 4 or 5 stories, and the cover was predominantly black. I don’t remember if it had any image on it. It was probably published in the 1970s, or possibly the early 80s. The story I remember best was the first in the collection. It was set in the near future, in which space travel exists, and Mars is being settled from Earth. It is a bleak hostile world, which used to be ruled by a technologically advanced civilisation that mysteriously vanished, leaving various artifacts behind. This would be consistent with the book being from the 70s, as there are no “Martian canals”, but nonetheless conditions are not as harsh as we now know they are. In any case, the story deals with a pair of Earthman treasure hunters who come across an ancient cache of military equipment in a cavern. They first find small arms (but of extreme power), then larger weapons, including something like a laser cannon which had a protective forcefield. Clearly Earth technology had not yet advanced to creating forcefields. Then they found a squad of robot warriors, and finally an unusual helmet. When one of the men puts it on, he realises he can hear his colleague’s thoughts “…yes, with these weapons and this army we can knock over a third world country, then live in luxury for the rest of our lives…” When he hears this, he calmly shoots the man, and remarks “No ambition. With this equipment, I could rule the world.” He sees one last box in the cavern marked something like “The final weapon” in the Martian script. He opens it, and a grey amorphous shape floats out. At first, thinking it was poison gas he runs from it, but the shape condenses around the man’s corpse on the floor and remarks “Still protoplasm. I like still protoplasm.” It then consumes the body in a gulp. It drifts after the remaining man who opens fire on it with the Martian guns to no effect. He operates the forcefield, but the shape just drifts through it. “Live protoplasm. I like live protoplasm” it remarks, and consumes him. It then goes to the surface looking for the many units of live protoplasm, “just as there had been so many centuries ago”. I would really love to know who the author was. Even fifteen years later I can still remember some of the dialogue verbatim  (well… I think I can), so it made a big impression on me. The other stories were less memorable. One was about a man with a very elaborate model train set up, who finds himself shrunk to the scale of the model, and is eventually killed by the trains.

This is a short story, I think by Ray Bradbury or Sheckley.  Two (?) adventurers/archaelogists are inside of the weapon cache left by Martian civilization which was destroyed by war. Eventually they find a chamber marked "Absolute weapon" (or ultimate weapon). They fight over who will get it, and only one of them survives. He opens the lock, releasing sentient blob that eats his fallen companions and then him, as well.


I'm coming across several posts (mostly questions) recently. They all come from new users. Those posts seem OK: they're on-topic and is only an edit away from a decent post for beginners to SE, except that there's a spam link, usually near the end of the post (So I call those posts otherwise salvageable).  I prefer a red flag but would that be too harsh?  I see this in :     If an otherwise valid post contains vulgar words as an expression of frustration, edit the bad part out instead of flagging the entire post as rude or abusive. If this results in an edit war or rollback war, flag for moderator attention.   It's about the rude or abusive flag. Is it the same for otherwise valid spam posts?    Note: I see this kind of posts on various sites, on some of which I don't have enough rep for full edit privilege.

I noticed that the posts of the recent spam surge on Ask Ubuntu were all edited by community members into something like     EDITED - REMOVED SPAM ANSWER   or similar.  While I understand why the users have done this and I too don't want to leave the spam content visible for longer than absolutely necessary, it made flagging more time consuming for me.  I had to check the revision for every of those possible spam posts to check if it is actually spam, instead of being able to flag directly from the review site. Spam flags carry a serious penalty, I'm not willing to add my spam flag without checking that it's really spam.  I see the benefit of editing spam, but it also causes some more effort for the later flaggers. Should we as a general policy edit out the content of spam posts, or should we deal with them solely by flagging?


I have file filestore.xml from which I need to extract /local/armdata/data/filestore1, /local/armdata/data/filestore2.  grep binariesDir filestore.xml     <binariesDir>/local/armdata/data/filestore1</binariesDir>     <binariesDir>/local/armdata/data/filestore2</binariesDir>   Is there any way to do this?

I would like to know how I can get the value of a node with the following paths:   config/global/resources/default_setup/connection/host config/global/resources/default_setup/connection/username config/global/resources/default_setup/connection/password config/global/resources/default_setup/connection/dbname   from the following XML:  <?xml version="1.0"?> <config>     <global>         <install>             <date><![CDATA[Tue, 11 Dec 2012 12:31:25 +0000]]></date>         </install>         <crypt>             <key><![CDATA[70e75d7969b900b696785f2f81ecb430]]></key>         </crypt>         <disable_local_modules>false</disable_local_modules>         <resources>             <db>                 <table_prefix><![CDATA[]]></table_prefix>             </db>             <default_setup>                 <connection>                     <host><![CDATA[localhost]]></host>                     <username><![CDATA[root]]></username>                     <password><![CDATA[pass123]]></password>                     <dbname><![CDATA[testdb]]></dbname>                     <initStatements><![CDATA[SET NAMES utf8]]></initStatements>                     <model><![CDATA[mysql4]]></model>                     <type><![CDATA[pdo_mysql]]></type>                     <pdoType><![CDATA[]]></pdoType>                     <active>1</active>                 </connection>             </default_setup>         </resources>         <session_save><![CDATA[files]]></session_save>     </global>     <admin>         <routers>             <adminhtml>                 <args>                     <frontName><![CDATA[admin]]></frontName>                 </args>             </adminhtml>         </routers>     </admin> </config>   Also I want to assign that value to the variable for further use. Let me know your idea.


Question: Fix a natural number $n.$   Is it true that if $n = 2^k$ for some integer $k\geq 1,$ then    $$\binom{n}{\frac{n}{2}}$$    is an even number?   Note that $\frac{n}{2}$ is always an integer, so the combination is defined.   Recall that to calculate $\binom{n}{\frac{n}{2}},$ we calculation a fraction with numerator $\frac{n}{2}$ numbers starting with $n$ and then decrease by $1,$ and denominator $\frac{n}{2}$ starting with $1$ and then increase by $1.$  I notice that $n$ in numerator always cancels with $2 \times \frac{n}{2}$ at the denominator, so the number of even numbers for numerator is more than in denominator.  However, I do not take into account the power of $2$ in both numerator and denominator.   Any hint would be appreciated.

Prove that $\frac{(2n)!}{(n!)^2}$ is even if $n$ is a positive integer.      For clarity: the denominator is the only part being squared.   My thought process:   The numerator is the product of the first $n$ even numbers and the product of the first $n$ odd numbers.   That is, $(2n!) = (2n)(2n-2)(2n-4)\cdots(2n-1)(2n-3)(2n-5).$ In effect, the product of even numbers can be cancelled out with $n!$ resulting in the following quotient:  $$ \frac{(2^n)(2n-1)(2n-3)}{(n!)}\;.$$  To me this looks even thanks to the powers of $2$. But I am not convinced for some reason.   Was this approach to naive?   Sorry for the poor notation, I don't know any coding languages, my apologies.


I want to cd into a directory from the terminal but access is denied, and typing sudo cd (directory) returns an error about sudo not supporting the cd command.  I can use sudo gnome-terminal to launch a new terminal window with root privileges, but I want a solution that I can use from the same non-root terminal window.  Is there a way to make the cd command compatible with sudo?

I want to cd into /var/named but it gives me a permission denied error, and when I want to use sudo to do this I am not permitted. What is the technical reason for this, and is it possible to do this some other way?


I would like to know how to add to a template file a blog post content rendering code so that all blogs will be displayed whenever that template is rendered.

I'm creating custom templates for my Drupal 7 site. There is a custom content type called flowers.   Which template file (.tpl.php) should I put under templates directory of my theme's folder for displaying a single flower-type node? Can I use the Views module to create different views (i.e displaying picture of a flower in a view & displaying species of the flower in another view) for displaying only a single flower-type node? So far I can create pages that displays list of flower-type nodes. I want to display just a single (perhaps providing it's node-id) flower-type node. How do I do that?  2.1. For displaying different types of views to display a single flower-type node, which template files (.tpl.php) should I edit?   Thanks in advance for caring :)


I know there are already several questions about this problem. However, I did not find a solution using the answer already provided.  I just installed Ubuntu 14.04 LTS dual-boot alongside Windows 8. When logging in to Ubuntu using the login manager I am stuck in a log-in loop where I find myself at the beginning again after a black screen in between.  What makes this really difficult for me is that the computer does not have an internet connection and it will take a while until this will be possible. So I cannot install any updates or new applications.  I already tried to create a new (root) user, I changed permissions of my home folder or the /tmp folder, I changed permission of .Xauthority (which worked at first but after a reboot I have the same problem again and changing permission of .Xauthority does not help anymore), changed permission of .IDEauthority (I also tried just moving .Xauthority or .IDEauthority to a different file), restarted lightdm or rebooted the whole system. Also, .xsession-errors does not show any error message.  Not sure if this is helpful, but the system has an nvidia Quadro K2200 and it is apparetly running with the nouveau driver (at least according to "lshw -C display").   Any other ideas? Do you think I can solve this without internet access?  Thanks in advance!

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


I'm coding a vertical navbar and I want to center all the lists in the center, vertically and horizontally. But I set my height as 100vh, and now I don't know ow to use the line-height selector to center the lists vertically. Here's the code I would really appreciate some help:    * {             padding: 0px;             margin: 0px;         }          .navbar {             height: 100vh;             width: 10%;             background-color: aquamarine;             text-align: center;             transition: 1s ease-in;                      }          .navbar:hover {             width: 100%;         }          .navbar:hover li{            width: 100%;            opacity: 1;        }          li {             transition: 1s ease-in;             opacity: 0;             margin-bottom: 30px;             line-height: 10vh;             vertical-align: middle;         }          a {             text-decoration: none;             color: black;             font-size: 20px;         }

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I want to center a div vertically with CSS. I don't want tables or JavaScript, but only pure CSS. I found some solutions, but all of them are missing Internet Explorer 6 support.
Div to be aligned vertically
   How can I center a div vertically in all major browsers, including Internet Explorer 6?


Is there a rule or guideline for a good relation between the answer to question ratio?  I mean to be a reasonable SO-user and be accepted by others. Should good SO-users give (answer) more than take (ask)?  Or is it nowadays the other way around: I should take more than give?    Is there a guideline for the ratio of upvotes to downvotes?  Is occasional downvotes, but not too many, expected of a good member of the community?

Let me say first that I am fairly new here (about 3 weeks) and absolutely love Stack Overflow. At first I let some of the negative attitudes get to me a little, left a few snarky comments, but that phase has passed. I see the tremendous value for this site in the long run and sincerely do want to help make it a better place.  I find myself going for  the downvote very frequently -- currently about 35% of my votes are downvotes. I even make an extra effort to upvote good content to offset this a bit, so the number should probably be more like 60%. I always try to leave constructive comments and try to help out the confused ones who are really trying.  I truly can't tell if it is just me, or if these folks deserve it. I don't know if you guys noticed, but there are a lot of really bad questions being posted, and a lot of people trying to pass off things like "use jQuery", "use Firebug", and "use Google" as good answers (and getting upvotes!). I even saw someone copy/paste my "What does Firebug say?" comment as an answer and get 3 votes within moments. Sometimes This answer is unclear or not useful just doesn't do it justice.  I feel like some of the people just drive me nuts, but then again I feel this way IRL :) Am I being too harsh, or is it really that bad on SO? Has there recently been a surge of new users, and the quality of content is degrading, or was it like this in the "good old days"? Have I perhaps misunderstood the expected behavior on Stack Overflow -- should I just ignore these crappy questions and answers rather than downvote them?


I have 4 authors for one article but I get one name and initals for all the others:  @Article{everythingIPA,   author       = {Federico Berruti \& Graeme Nixon\& Giambattista Taglioni\& Rob Whiteman},   journal      = {McKinsey Digital},   title        = {Intelligent process automation: The engine at the core of the next-generation operating model},   year         = {2017},   date         = {2017-03},   journaltitle = {McKinsey Digital}, }   I've tried using , or ; as separators and that way, I can get 2 names correct but not all 4.

I use  to store all articles I need and bibtex4word add-on (in MS Word) to maintain the reference list. So, I would like to know how to properly fill the "author" field in Jabref with multiple authors to appear them correct in the reference list.  For example, I've got the article with several authors:      E. Orti, J.L. Bredas, C. Clarisse   And I would like them to appear in this manner. But instead I get this:     C. C. E. Orti, J. L. Bredas


I am wanting to use a switch/ case statement in bash to check if a file name which is a string contains something but also does not.  Here is my case:  case "$fileName" in     *Failed|!cp*)        echo "match"      ;; esac   But this does not work currently, how can I see if the string matches "Failed" but also does not contain "cp"?  It would be great if this could be done in a switch/ case as well

I have a string in Bash: string="My string"  How can I test if it contains another string? if [ $string ?? 'foo' ]; then   echo "It's there!" fi  Where ?? is my unknown operator. Do I use echo and grep? if echo "$string" | grep 'foo'; then   echo "It's there!" fi  That looks a bit clumsy.


I'm trying to create a class that, among other things, generates URLs from parameters passed to an environment. For some weird reason, if the URL string contains a /, hyperref tries to create a URL that points to a file named <URL>.pdf.  \documentclass{article}  \usepackage{expl3} \usepackage{xparse} \usepackage{verbatim} \usepackage{hyperref}  \ExplSyntaxOn \keys_define:nn { mydocument / myenvironment } {   link    .tl_set:N = \l_myenvironment_link_tl,   print   .bool_set:N = \l_myenvironment_print_bool, }  \NewDocumentEnvironment { myenvironment } { m } {   \keys_set:nn { mydocument / myenvironment } { #1 }     \minipage{\textwidth}      \tl_clear_new:N \l_item_url_tl      \tl_put_left:Nn \l_item_url_tl { https:// }     \tl_put_right:Nx \l_item_url_tl { \l_myenvironment_link_tl }      \href{\l_item_url_tl}{TeX.StackExchange} \\      \url{\l_item_url_tl} \\  } {     \endminipage } \ExplSyntaxOff  \begin{document}  \begin{myenvironment}   {      link = tex.stackexchange.com,   }   Here is some content in my environment with a good link \end{myenvironment}  \begin{myenvironment}   {      link = tex.stackexchange.com/users/3351/robbie,   }   Here is some content in my environment with a \textbf{bad} link \end{myenvironment}  \end{document}   The above MWE exhibits the behaviour I'm describing: the first instance of the environment has a link to https://tex.stackexchange.com, but the second creates a link to https://tex.stackexchange.com/users/3351/robbie.pdf. Weirdly enough, it doesn't mangle the URL if I use \url, but I can't use that command in my document as the link text is also generated.  Why does it do this, and how do I make it use the raw URL value in the hyperlink target?

I'm creating a simple macro with \href in it. But it seems to be kind of tricky, because using \href with a parameter does not recognize the link format. It simply adds an unwanted .pdf to the link target.  Basically the link  https://ctan.org/pkg/hyperref   is automatically changed to   https://ctan.org/pkg/hyperref.pdf   What is causing this behavior?  \documentclass{article} \usepackage{expl3,xparse} \usepackage{hyperref} \ExplSyntaxOn \cs_new:Npn \__pkgcls:n #1 {     \texorpdfstring{             \href{https://ctan.org/pkg/#1}{\ttfamily#1}     }{#1} } \DeclareDocumentCommand{\class}{o m}{% typeset class names     \__pkgcls:n { #2 } } \DeclareDocumentCommand{\package}{o m}{% typeset package names     \__pkgcls:n { #2 } } \ExplSyntaxOff \begin{document}   \class{scrartcl}\\\package{hyperref}\\\href{https://ctan.org/pkg/hyperref}{\ttfamily hyperref} \end{document}     Update: Here's a screenshot:    Update: The problem seems clearly expl3 related. Using something like  \def\pkgcls#1{\texorpdfstring{\href{https://ctan.org/pkg/#1}{\ttfamily #1}}{#1}} \def\pkg#1{\pkgcls{#1}}   produces the correct result.


I'm writing a plugin, and near the top of the main plugin file I have a series of require_once statements as is typical.  After more than ten hours of trying to figure out why WP couldn't find my classes, I finally landed on this -- if I had:  require_once( 'includes/myclassfile.php' );   it failed.  But if I explicitly put in the base path like so:  define ( 'MY_DIR', rtrim( plugin_dir_path( __FILE__ ), '/' ) ); require_once( MY_DIR . '/includes/myclassfile.php' );   it worked.  So my question is: why didn't the first form work?  My IDE (PhpStorm) understood it, the boilerplate I started from used it, and I have other plugins installed that use that form, and they work.  What could have been different about this case?  Edit: This question got marked as duplicate of another that also addressed confusion about the proper use of require, however in that case, the final conclusion was the opposite of what worked for me.  I am not asking what to do, but why one version would fail.  Isaac's answer suggests a reason, but it is unsatisfying since there are other top-level plugins in my wordpress install that do work with the form that doesn't work for mine --- I would like to know what makes mine different.  (Just to be complete, here is the full plugin file:)       /*  * Plugin Name: A Strenga Projects  * Version: 1.0  * Description: Projects for Strenga  * Author: DD  */ if ( ! defined( 'ABSPATH' ) ) exit;  define ( 'STRENGA_PROJECTS_DIR', rtrim( plugin_dir_path( __FILE__ ), '/' ) );     require_once( STRENGA_PROJECTS_DIR . '/includes/plugin.php' );  function myFoofunction() {     ladeda();  // defined in plugin.php } myFoofunction();

My problem is when on the main plugin file I include a PHP file something like this:  include(WP_PLUGIN_URL . '/wordpress-group-buying/ipn/paypal-ipn.php'); // or include_once(WP_PLUGIN_URL . '/wordpress-group-buying/ipn/paypal-ipn.php'); // or require(WP_PLUGIN_URL . '/wordpress-group-buying/ipn/paypal-ipn.php'); // or require_once(WP_PLUGIN_URL . '/wordpress-group-buying/ipn/paypal-ipn.php');   and on that file I have a call to a WordPress function like:  add_action('hook', 'callback');   and I get:     Fatal Error: Call to undefined function add_action()   Now before you say "use if(**function_exists**('add_action')){" if I use that then it just doesn't work.  The questions:   What would be the correct way to do that? What are the difference between include, include_once, require and when do I use witch?


When looking at chat replies on a regular SE site, I see this:    However, when looking at the same notification on , I see this:    As you can see from the hovertext, it seems to just be the icon that is being loaded incorrectly: the  icon is being loaded instead of the SE icon.  This , but with no real resolution other than "wait and it might go away".

Today I'm seeing the wrong icon in the dropdowns only on chat.  The circled icons should be Writers, not Worldbuilding:    They're correct on the Q&A sites:    I've only seen this for Writers so far.  If I get any inbox notifications or rep for other late-in-the-alphabet sites, I'll update.  As you can see in the screen shot from chat, Meta.SE is fine.  I suspect this has to do with the creation of new sites, indexing, and caching, but new-site is Tuesday and it's Thursday now, so that's some pretty heavy-duty caching if that's the cause.


Often, for work reasons, I have to create xubuntu virtual machines that I use for embedded development. How can I (starting from an iso image and a blank VM) avoid installing things I don't need, such as libreoffice? On google I found no way to do a manual or custom installation.  Edit: I don't want and don't need to customize a Live CD ISO. I need a custom installation cd that installs on my hard disk the packages I decide. I tried cubic, and he created a live cd for me, but not an installation cd.

I would like to customize Ubuntu live CD by installing some additional packages. I have followed   but it doesn't seems to work. Can anyone provide clear instructions?   Note: I do not prefer Remastersys, manual way will be appreciated.  Customization  Packages that I want to install:   Thunderbird    Samba    SSH       Changes that I need:   Remove Games menu from the Application menu Firefox shortcut on Desktop Radiance as the default Theme Different default Ubuntu Wallpaper   Configuration file changes   I want the panel to be placed at the bottom I want to paste my Samba configuration file instead of default Samba configuration I have few Firefox shortcuts and folders I would like to show that in Desktop Also it will be nice if you say me how to change the icon sets   Recent Updates   I have customized Ubuntu 10.10 with Firefox shortcuts and few folders on desktops. Everything went smooth. But the installer gets crashes after choosing the timezone. How do i fix this issue? Also setting wallpaper affects the login screen. The wallpaper which i set is displayed on the login screen also. I just want the default one for the login screen.


I want to change column separator symbol '&' of tabular environment by creating a new environment that also works similar to tabular environment. Please Help.

I am new in LaTeX. In tabular, we generally use & for partition. I want to create a .sty for tabular environment. Replace & with comma delimiter, in this case comma should be work as & like in tabular command.   In .tex file, input is a,b,c and output should look like |a|b|c|


For a commutative ring $R$ with $1\neq 0$ and a nonzerodivisor $r \in R$, let $S$ be the set  $S=\{r^n\mid n\in \mathbb{Z}, n\geq 0\}$ and denote $S^{-1}R=R\left[\frac{1}{r}\right]$.  Prove that there is a ring isomorphism $$R\left[\frac{1}{r}\right]\cong \frac{R[x]}{(rx -1)}.$$  I'm thinking maybe I can find a homomorphism from $R[x]$ to $R\left[\frac{1}{r}\right]$ that has kernel $(rx-1)$, and then use the first isomorphism theorem. Is this the right approach?

I am having trouble with the following problem.      Let $R$ be an integral domain, and let $a \in R$ be a non-zero element. Let $D = \{1, a, a^2, ...\}$. I need to show that $R_D \cong R[x]/(ax-1)$.    I just want a hint.  Basically, I've been looking for a surjective homomorphism from $R[x]$ to $R_D$, but everything I've tried has failed. I think the fact that $f(a)$ is a unit, where $f$ is our mapping, is relevant, but I'm not sure. Thanks


I wants to use the application GAP. Please help me, how should I start and from where? I need this to compute some specific structures. Thanks for help!

Background: This year I'll do another Group Theory course ( Open University M336 ). In the past I have used Mathematica's AbstractAlgebra package but (although visually appealing ) this is no longer sufficient (i.e. listing subgroups of $S_4$ takes ages). So, I want to learn more about GAP. I worked through beginner tutorials that I found via the . Currently, I am not making much progress with GAP. The  does not help me much at this stage.  Question: Which resources are available to self-study GAP? How does one become proficient in GAP? What ( books, tutorials ) should you study?


Harry survived the Killing Curse because Lily gave her life to save his, and that's it. Similarly when Harry gave his life to save the people of Hogwarts, Voldemort couldn't kill anyone attending there so they are also made immune to the curse. So how has this never happened before?? No one in the history of the world has ever sacrificed themselves? Seems fishy.

While answering another question I mentioned the love protection spell from Harry's mom, which got me thinking, since this spell is so unique and no one understands it, does that mean not a single person in the entire history of wizards is known to have died for someone because of love and then have created a protection spell for that person?  No parents, spouses or really close friends in the history of everything self-sacrificed for a loved one?  Did JKR create a loveless universe, where love was as miraculous and rare as the fact that Harry is the only person to survive Avada Kedavra?


Let $X$ and $Y$ be random variables such that $X$ follows a standard normal distribution and that the support of Y is $S_{Y} = (-1,1)$ with $P(Y = -1) = P(Y = 1)$. Let $Z=XY$. By using the CDF method and MGF method, derive the probability density function of Z.  The problem I have with this question is that I do not know how to use the information I am given about $Y$.  My attempt:  MGF METHOD: $$E(e^{tZ})=E(e^{tX}e^{tY})=\frac{e^{t^2}}{2}E(e^{tY})$$  CDF METHOD: $$P(Z\leq a)=P(XY \leq a)=P(X \leq \frac{a}{Y})$$  I notice $Y$ is an even function. I'm not sure what other useful information it gives me. Any help is appreciated.

I have two independent variables: $X$ follows from standard Gaussian distribution $N(0,\sigma^2)$; $Y$ follows from Rademacher distribution, i.e., $Y$ can be either $-1$ or $1$ with the same probability.  My question is:  For a new random variable of $Z=XY$, What is the probability density function?   Or can we have some concentration inequalities for $Z$ (e.g., show how $Z$ approaches its expectation, etc.)?


Dear all,  As you can see on the above figure, I would like the text to be higher (like it should start at the top of the image).  My code is :  \begin{figure}[ht]  \centering  \includegraphics[scale=1]{Images/GIS_mapping_Software.jpg}  \caption{test}  \label{GIS_Mapping_Software}  \end{minipage}% \begin{minipage}[t]{10cm}  As shown on figure ~\ref{GIS_Mapping_Software}, the purpose of the GIS is to display multiple maps on one single map.\\  For example, a single map could regroup sites that produces pollution and sensitive sites to pollution. \\ \end{minipage}  \end{figure}    Is there anyway I can change my code so that the text begins at the top of the image ?

I would like to be able to align two minipage at the top, without worrying about what is in the minipage.  I am aware of the optional [t] parameter, but still have some confusion as to how this all works.  I tend to think of a minipage as a regular page in that whatever is placed on it starts at the top and fills the page going across and then down the page, but this does not appear to be the case.  In the MWE example below, I have color coded the sections for reference purposes.   The first case (black) works just as I would expect. The two minipages are aligned exactly as I want with the [t] specifier.  No question here.  The next case (red) only works if the inner minipage also has the [t] specifier. Why is that necessary?  I would have thought that any content would be placed at the top of this page, and since both the outer minipage had a [t] things should have aligned at the top. I would like to place a graphic in the second mini page, and still have the two aligned at the top.   The simple case (blue) of using \includegraphics directly does not result in the content being aligned at the top.  So, then I attempt to put this in a \parbox (green) and this too does not yield the desired results.  I also try to place the graphic inside an inner minipage (brown) and specify the [t] alignment, and even though this worked in the red section, it does not here.  The only difference between the red and brown being that the red section had text, whereas the brown section has a graphic.  I am aware of question regarding  which suggests to place \vspace{0pt} at the top of the minipage, and that does provide the desired alignment (cyan), but adds vertical space at the top.  So, my second question is why is the \vspace{0pt} necessary when a graphic is included, but not when it is text.  This appears to be a hack and wondering if there is a replacement for minipage that works better without having to worry about exactly what is in the minipage?  Also, why did wrapping the figure in a parbox (green) or another minipage (brown) not solve this problem?   Here is the MWE:  \documentclass{article} \usepackage[demo]{graphicx} \usepackage{lipsum} \usepackage{xcolor}  \begin{document} \section{This Works - Aligned at top as desired} \begin{minipage}[t]{0.6\linewidth}     \lipsum[1] \end{minipage} \hfill \begin{minipage}[t]{0.3\linewidth}     \lipsum[2] \end{minipage}  \color{red} \section{Why does inner mini page required the [t]?} \label{Minipage-in-minipage} \begin{minipage}[t]{0.6\linewidth}     \lipsum[3] \end{minipage} \hfill \begin{minipage}[t]{0.3\linewidth}     \begin{minipage}[t]{\linewidth}% Why is [t] required here         \lipsum[4]     \end{minipage} \end{minipage}  \color{blue} \section{Why are These not aligned at top?} \begin{minipage}[t]{0.6\linewidth}     \lipsum[3] \end{minipage} \hfill \begin{minipage}[t]{0.3\linewidth}     \includegraphics[width=\linewidth]{foo} \end{minipage}  \color{green} \section{Why are These not aligned at top?} \begin{minipage}[t]{0.6\linewidth}     \lipsum[3] \end{minipage} \hfill \begin{minipage}[t]{0.3\linewidth}     \parbox{\linewidth}{\includegraphics[width=\linewidth]{foo}} \end{minipage}  \newpage \color{brown} \section{Why does this not work with the [t] as it did in red section?} This worked fine in Section \ref{Minipage-in-minipage}  \begin{minipage}[t]{0.6\linewidth}     \lipsum[3] \end{minipage} \hfill \begin{minipage}[t]{0.3\linewidth}     \begin{minipage}[t]{\linewidth}% Even with [t] here, this does not work         \parbox{\linewidth}{\includegraphics[width=\linewidth]{foo}}     \end{minipage} \end{minipage}   \color{cyan} \section{Adding a \textbackslash{}vspace\{0pt\} works} \begin{minipage}[t]{0.6\linewidth}     \vspace{0pt}% Hack!! But does do the job     \lipsum[3] \end{minipage} \hfill \begin{minipage}[t]{0.3\linewidth}     \vspace{0pt}% Hack!! But does do the job     \begin{minipage}[t]{\linewidth}% Why is [t] required here         \parbox{\linewidth}{\includegraphics[width=\linewidth]{foo}}     \end{minipage} \end{minipage} \end{document}


I've just download and installed the latest version of CentOS inside a VirtualBox VM. Installation went OK, but when I start the VM and log in, if I try and ping anything I get an error due to lack of network interface.  if I try and issue the ifup eth0 command, I'm told      network is unreachable   . If I list the network interfaces using ip link show the interfaces that are listed are:  lo enp0s3   I know what the loopback interface is for, but what is the latter? I was expecting eth0 or wlan0.  Inside virtual box I've set my network adapter to NAT, Bridged and Host Only but it makes no difference to the resultant Linux machine  As you can guess, I'm a tad new to all this, so any help on getting networking working inside my VM is appreciated.  Many thanks  ****edit**: so now I know the new (rather confusing) naming convention, thats good. Been a while since i used Linux. I followed this guide:  but when I run service network restart it fails. Looking at the log it says:  Failed to start LSB: Bring up/down networking.   **

When I run ifconfig -a, I only get lo and enp0s10 interfaces, not the classical eth0  What does enp0s10 mean? Why is there no eth0?


provides insight on the average performance of actively managed mutual funds from ~5 years ago:     Growth fund managers fared even worse, with just 6% of growth funds beating their benchmark -- the worst such result since at least 1991. The average margin of underperformance reached a whopping 3.5 percentage points.   If it becomes harder and harder to beat the large indexes, why would one still go with actively managed mutual funds? My understanding is that they are also more pricey, expense ratio-wise, and come with more tax hurdles. Furthermore, I'd assume that modern technology like robo-advisors is going places.

The general consensus is that the single best indicator of a fund's future performance is the its expense ratio . If you look for more than 5 minutes online you discover the  approach to investing; the , etc. It looks like the less you pay for a fund (and therefore the less it's managed), the better it does in the long run.  So why is it that in peoples' 401(k)s there are so many high-cost actively managed funds? Furthermore, why are there so many high-cost actively managed funds in the first place? Shouldn't the market reflect the fact that actively-managed funds typically don't beat the index they benchmark to and and react by purging itself of these crappy funds?


In Windows, when you change a file extension, you get a warning     If you change a file name extension, the file might become unusable      Are you sure you want to change it?      Is there a registry key or group policy setting to disable this warning?  If you know of an authoritative reference indicating the warning can't be disabled, please link to it.  I change file extensions frequently and always have to confirm this dialog.

Is there a way to turn off the file extension rename dialog in Windows 7?  The one that prompts you     Rename: If you change a filename extension, the file might become unusable. Are you sure you want to change it?


So I'm currently in junior year of my undergrad as an Electrical Engineering major. As of this moment my GPA's 3.25; however, throughout my college career I've had to retake courses multiple times in order to get passing grades, and I still have some B's and C's. I plan on talking to advisors for grad school but at this rate it feels pointless to even consider thinking about applying in the future. Especially because the classes I retook were classes I initially failed, and because sophomore and freshmen year I was a different major (Biology) so it's going to take more time for me to finish my undergrad.

When applying to a PhD program in the US, how does the admissions process work? If an applicant is weak in a particular area, is it possible to offset that by being strong in a different area?  Note that this question originated from this . Please feel free to edit the question to improve it.


I was trying something with Integer, and output is freaking me out.  public class CountB {    public static boolean returnBool(String w, Integer count)   {      for (int i = 0; i < w.length(); i++)      {          if (w.charAt(i) == 'B' || w.charAt(i) == 'b')         {        count++;         }      }      if (count > 0)       return true;     return false;    }    // write the static method “isThisB” here   public static void main(String[] args)   {     //  Scanner keyboard = new Scanner(System.in);    //   System.out.println("Enter a string: ");    String w = "fgsfbhggbB";//keyboard.nextLine();    Integer count = new Integer(0);    System.out.println(returnBool(w, count));    System.out.println("Number of B and b: " + count);   } }   Now, Integer being a wrapper class of int, and count being its object, when I pass count from main to returnBool, value of count becomes 3, so it returns true, as java is pass by value count object value should change in main method also, but in main count prints 0.  I want to understand why this is happening?

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


Does $ L = \sum_{i=2}^{\infty } \frac{1}{n \log(n)} $ converge or diverge?  I established that:  $$ L \le I   = \int^{\infty}_{2} \frac{1}{n \log(n)}   = \lim_{n \to \infty} [ \ln(\log(n)) - \ln(\log(2)) ], $$ and as $ \lim_{n \to \infty} \log(x) = \infty $, then $ L $ diverges.  But I'm not sure:   of the sense of the inequality, about the conclusion.

Recently, I encountered a problem about infinite series. So my question is how to know whether the infinite series $\sum _{n=2}^{\infty } \frac{1}{n \log (n)}$ is convergent?


Let $a,b$ and $c$ be positive integers such that $gcd(a,b)=1$ and $a\vert bc$. Prove that $a \vert c$.

Well I thought this is obvious. since $\gcd(a,b)=1$,  then we have that $a\not\mid b$ AND $a\mid bc$. This implies that $a$ divides $c$. But apparently this is wrong. Help explain why this way is wrong please.   The question tells you give me two relatively prime numbers $a$ and $b$ such that $a$ divides the product $bc$, prove that $a$ divides $c$. how is this not obvious? Explain to me how my "proof" is not correct.


I want to boost the ram's memory, but as I clean my phone,it's memory was almost full.

I'm sure many people like me are aware and annoyed by the extremely limited amount of RAM in Nexus S (512MB but only 300+ is usable), I have searched all over google for a solution to increase the amount of RAM available and came up empty (I tried swap file applications but they just broke my system's SD card partitions causing a complete reset).  I wonder if there is any hardware solution to this problem. Is it possible to swap the chip out for a bigger capacity one? I realize that it is not as simple as swapping out PC RAM from a dimm but I haven't seen any schematics for the chip layout on the ARM boards in the smartphones so I really hope that it is somewhat possible to increase the amount of RAM on the board.


I have a PC which has 2 CPU's in the mainboard, 40 GB RAM and 3 Graphics Cards. Can Blender render for example one frame on all gpus at the same time? And generally: is it possible to render on cpu and gpu at the same time?

I have a GTX 1060 6GB in my current build, and I also have a GTX 960 2GB in storage. I was wondering if I got , and got both of my GPUs in one build (not SLI or CrossFire, just in the same system) would I be able to use both GPUs for rendering simultaneously? I don't care if this means having them both render separate tiles in one instance of Blender, or rendering separate frames in two instances. I'm using Cycles for everything I do.


I'm looking for the name of a science fiction short story in which characters lack modesty when communicating over video phones but direct contact is excruciatingly embarrassing.

Can anyone help me identify this book please? I read a book in the 80s about a woman living underground in a pod. Everyone had a big tv which gave them news etc (but it was starting to go wrong) and their food was delivered direct to their pod.  They weren't allowed to go to the earth surface as it was supposedly contaminated (post-war?). She gets a message from her son on the other side of the world and she takes the tube train from outside her pod and then some sort of aircraft to see him and eventually gets onto the surface of the earth and breathes the air and meets free people.


Let $G$ be a group of $2n$ .Let H be a subgroup of $G$ consisting of only those elements of $G$ which are of order $\neq 2$.Suppose $o(H)=n$ Show that $n$ is odd and $H$ is  abelian.  Pairing the elements $(g,g^{-1})$ of $H$ since $g\neq g^{-1}\forall g\in H$.Also $H$ has identity $e$.Thus $o(H)=n=$ odd  How to show $H$ is  abelian.

Question is:     Let $G$ be a group of  order 2n. Suppose half of the element of G are of order 2 and the other half form  a subgroup $H$ of order n . Prove that $H$ is of odd order  and is an abelian subgroup of $G$   What could i see is..  if we prove that order of every element of $H$ is odd , then order of $H$ is odd . Also i am unable to use the fact that half of the element of $G$ are of order 2.  Please help me to clear this.  Thank You.


Good day,  I have an engineering background and I recently took an interest in topology. I found this book Topology (2015) by Marco Manetti (ISBN 978-3-319-16958-3) and starting going through it.   Unfortunately I am experiencing a lot of difficulties with his definitions in the introductory chapter, which correspondingly means I can't quite do the exercises contained therein. Although I do understand the set-theoretic notation he uses, I find it difficult to understand the significance of these definitions and to develop a kind of intuition for them. Hence the question: is this book suitable for a beginner in this subject?  Best wishes

I am a graduate student of math right now but I was not able to get a topology subject in my undergrad... I just would like to know if you guys know the best one..


I've installed Ubuntu alongside Windows 7. How do I get access to my Windows files with Ubuntu?

I'd like a GUI method to set my Windows partition to mount on boot, using the same options as when it mounts by me opening it in nautilus.


I believe that Newton's third law is valid in special relativity. But I read an argument in Griffiths' textbook Introduction to Electrodynamics (3rd edition), where he argued on page 517, that Newton's third law is violated:     Indeed, if the two objects in question are separated in space, the third law is incompatible with the relativity of simultaneity. For suppose the force of $\mathbf{A}$ on $\mathbf{B}$ at some instant t is $\mathbf{F}(t)$, and the force of $\mathbf{B}$ on $\mathbf{A}$ at the same instant is $-\mathbf{F}(t)$; then the third law applies, in this reference frame. But a moving observer will report that these equal and opposite forces occurred at different times; in his system, therefore, the third law is violated.   Currently I could not find a argument against his. I found several posts here in Physics SE arguing that Newton's third law is equivalent to conservation of momentum, which is correct in special relativity. However, their reasons do not seem to invalidate Griffiths' argument. I would like to know where did Griffths' went wrong in his argument.    Update: I realize that there are several similar posts:      But both of them centered on the momentum conservation, whereas what I want to ask is about the action-reaction view of Newton's third law.

Relativity has always been explained to me (in books I've read, etc) as a superset of newton's laws - that is; it encapsulates all of Newton's mechanics in addition to other effects (observer effect, time dilation, space-time geometry, etc).   I can kind of imagine 2 of Newton's 3 laws of motion to be incapsulated within Einstein's Special Relativity, but the one about "for every action there is an equal and opposite reaction", I'm struggling to find a place for that within Special Relativity.   Does this sit outside Special Relativity's explanatory power or is it inferred within somehow?


I need to access a linux servers with private ip form any network.  Usually I use VPN to access those servers. But want to access without VPN.  Can you guys please tell the settings need to be done on server and on putty?  Thank you.

I've been hunting all over the inter webs and I cannot find a simple example of the form of port forwarding that I am looking for. Well, the truth is, I may have just simply not understood the jargon used and then overlooked a valid solution.  Here is the proposed setup. I have a computer at home (homeC) and I typically connect to a server at work (workServer.com), but whenever I connect to the server, I am generally (90%+ of the time) simply hopping over to another computer on the network (localC 192.168.x.y). I would love to setup workServer.com to port forward over to the other local computers ip addresses if I use a non-standard port (e.g. 12345).  Assume all computers involved are running some variant to unix, but that the user only has root access on some computers (not workServer.com). In fact, the username user is the same on all computers. I am trying to find ways to solve the following problems:   a command to use in workingServer.com which will forward a port to a given local computer (I also need to know which ports are available, I suppose) the command to run on homeC to connect to localC   On a side note, it would be interesting if it were possible to limit the mac-addresses of computers that can connect to user@workingServer.com because I see this as greatly increasing my security.  If you have any other ideas or useful suggestions, I would greatly appreciate them.


I am, apparently, one of 12 people with the gold tag badge for feature-request and one of 39 people with the gold tag badge for discussion here on meta.se.  I hadn't realized this until I cast a close as duplicate vote, then was shocked (and awed) by the power unleashed. Unicorns came from everywhere and swept the question off into duplicate land so fast I was left breathless!  While I certainly don't mind thinking of myself as a feature request or discussion expert, given that you have to tag every question with at least one of the four tags, bug, feature-request, discussion, support then being an expert in these tags may not mean as much, since they are so general and prevalent. Other gold tag badges would indicate expertise in a specific area, such as badges, or chat, but the required tags are fairly non-specific.  There are only 76 people with , so it's probably not a problem to be fixed immediately, and I'll just have to be more thoughtful about my dupe closing here on meta, but consider removing required tags from these new powers on sites where specific tags are required.

Recently  I'd like to request that moderators have the ability to disable this for certain tags. On the site that I am a mod on, , the [code-golf] tag accounts for over 50% of questions on the site. (We've been talking about getting in more diversity, but that's another discussion.) Clearly, giving users the ability to unilaterally close half the questions on the site is probably not a good idea. This could apply for other tags for which tag badges do not necessarily imply expertise - for example, a user having a tag badge in the [] tag on Code Review (sounds like a meta tag, but I'm not familiar with the site's policies and such) would not really imply that the user is an expert in... helping beginners? When this new feature launches across the network, could it also come with some way to disable it on tags that wouldn't benefit from it?


First of all I'm not a physist, my formation is related to Information Systems but I was always curious regarding the laws that rules our universe.   I would like to apologize as well for my bad english since it is not my mother language.  Recently I watched a video from professor Michio Kaku which makes me curious about the lack of information related to dark energy / dark matter.  To start with I would like to think that before the big bang, nothing else existed, even the empty space, so everything was concentrated in a single high density ball of pure energy with a mass tending to be infinite.  When the big bang took place, this ball of energy expanded in all directions, expanding the own space and everything inside trough all directions. Today we know that nothing can go faster than speed of light, however this afirmation is based on the fact that the light is travelling on vacuum or empty space.   Considering a supposition that our own dimension was created together with the big bang including the space, this law may not be applied at the very first moments after the big bang since the objects could be travelling ahead of the speace itself.  If we consider that during the big bang, 80% of the energy released started travelling faster than light in all directions, creating the own space on it's way, and then we had the remaining matter travelling below the speed of light behind it.  Since nothing on space can travel faster than speed on light, we can not see the objects that initially started travelling faster than speed of light, however their gravitional effects can be feel at the the galaxies near the boundaries of the universe which are being pulled away from each otther.  The big questions about dark energy and dark matter is that something should exist otherwise galaxies won't have enough mass to be formed as well as the fact that the speed the universe is expanding is increasing over time. If instead of having dark energy acting on the space between the matter, we have simply a massive amount of matter outside the know boundaries of our universe pulling the galaxies away from the centre of the universe, could this be a plausible solution for the dark matter / dark energy question?  Again sorry for the stupid question, but it was something that came into my mind and even after looking for answers on internet I could find anything related to it.

There's more gravitational force in our galaxy (and others) than can be explained by counting stars made of ordinary matter. So why not lots of dark planetary systems (i.e., without stars) made of ordinary matter? Why must we assume some undiscovered and unexplained form of matter?


If Char$F$ $\neq  0$, then Char$F$ must  be prime number.  MY try: If Char$F$$ = nk $ for integers $n$ and $k$, then by definition, $nk = 0 \implies n = 0$ or $k = 0$ which implies Char$F=0$ which is a contradiction.   Is this correct?

I'm trying to prove that the characteristic of any field $F$ is either $0$ or a prime number, but I have no idea what to do.  Help?


I'm using the SE app on an Android phone (Galaxy S5 OS 6.0).  When I try the option to view a question in a browser, it simply opens the same question in the app. It doesn't even try opening the browser.  Is this a common issue, or am I the only one experiencing it?  Things I've tried:   clearing defaults for the SE app, clearing defaults for my browsers, clearing data for the SE app, restarting my phone   Here's the option I'm talking about:

This is a follow-up to .     When I click a link to an SE site in the Android app, it gives me an "open with" pop-up that has two options:         Chrome   Stack Exchange         I can then choose to open SE posts like this "Just once" or "Always."      The problem is that when I set the SE app to "always," and I click "open in browser,"   Except, the app crashes when trying to open it in browser.  LogCat (just right after selecting "Open in browser")  01-22 18:03:36.354: E/AndroidRuntime(16064): FATAL EXCEPTION: main 01-22 18:03:36.354: E/AndroidRuntime(16064): Process: com.stackexchange.marvin, PID: 16064 01-22 18:03:36.354: E/AndroidRuntime(16064): java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference 01-22 18:03:36.354: E/AndroidRuntime(16064):    at com.stackexchange.marvin.utils.Helpers.getNonMarvinViewIntent(Helpers.java:452) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at com.stackexchange.marvin.ui.question.QuestionDialog$1.onClick(QuestionDialog.java:39) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at com.android.internal.app.AlertController$AlertParams$3.onItemClick(AlertController.java:1108) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at android.widget.AdapterView.performItemClick(AdapterView.java:310) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at android.widget.AbsListView.performItemClick(AbsListView.java:1145) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:3066) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at android.widget.AbsListView$3.run(AbsListView.java:3903) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at android.os.Handler.handleCallback(Handler.java:739) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at android.os.Handler.dispatchMessage(Handler.java:95) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at android.os.Looper.loop(Looper.java:148) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at android.app.ActivityThread.main(ActivityThread.java:5417) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at java.lang.reflect.Method.invoke(Native Method) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 01-22 18:03:36.354: E/AndroidRuntime(16064):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)   I suspect it's related to , but not sure.  Specs:   Device model: Nexus 5 Android version: Android 6.0.1 SE app version: 1.0.82 (beta) Installed browser: Chrome 47.0.2526.83 (latest at current writing)


Citizens of the USA naturally refer to themselves as Americans and refer to the country as America.  When speaking to a person from Canada, he argued that it was incorrect to call the country America. Instead, I should be saying the United States (of America).  Is it incorrect to refer to the country as America? And even if it is, won't people from around the world understand that the USA = America?

People often refer to the country US as America and to the people from the US as Americans.  As far as I know, that's the only case in the world where a continent's name is used for a country's name (let me know if I'm wrong). Why does that happen?


Prove that for any integer $n$, we have $n^3=n  \text{ in } Z_6$

Prove that for every integer $n$ , $n^3=n \text{ mod }6$  I was having no clue how to do this, then I thought of case-by-case analysis and obviously it worked. The problem is that there were six case and together they are long.   Is there any shorter method of proving this. Kindly provide some hints.


Me and my friend were arguing regarding the effects of alcohol and i wanted to ask here to clarify. Are there any positive effects to being intoxicated?

If a character is drunk, what are the penalties associated to it? Are there any benefits to it? I do remember a special prestige class for monks about it, but I don't remember anything specific in the core rulebook.


I wrote a simple bash script which does nothing but sleeps.  #!/bin/bash  echo "Sleeping..." sleep 180s   I see two processes running on my system after I run the script:  user 22880  0.0  0.0  12428  1412 pts/28   S+   20:12   0:00 /bin/bash ./sleep.sh user 22881  0.0  0.0   7196   356 pts/28   S+   20:12   0:00 sleep 180s   I give a SIGTERM to the process with id 22880 by using kill -15 22880 which kills the process. However, after this, I still see the sleep command running which exits after 180 seconds.  user 22881  0.0  0.0   7196   356 pts/28   S    20:12   0:00 sleep 180s   Why does this happen? What do I need to do to not leave the sleep 180s process running?

I want to kill a whole process tree.  What is the best way to do this using any common scripting languages? I am looking for a simple solution.


I am trying to get a list from another form. I have made the list public and put it in its own class to no avail.  Form1:  using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; using System.Data.Common; using System.Configuration;  namespace eAnfonebu {     public class variables     {         public List<int> rhifAnfoneb = new List<int>();         public List<int> rhifArcheb = new List<int>();         public string[] ddydiadArcheb;         public string[] enwArchebwr;         public string[] eBost;         public int[] gair;         public decimal[] prisMilGair;     }     public partial class Form1 : Form     {           public Form1()         {             InitializeComponent();          }          private void Form1_Load(object sender, EventArgs e)         {          }          private void createNew_Click(object sender, EventArgs e)         {             Form2 f2 = new Form2();             f2.ShowDialog(); // Shows Form2         }      } }   Form2 (addInvoice):  using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms;  namespace eAnfonebu {     public partial class Form2 : Form     {         public Form2()         {             InitializeComponent();         }          private void AddInvoice_Click(object sender, EventArgs e)         {             try             {                 variables.rhifAnfoneb.Add(variables.rhifAnfoneb[variables.rhifAnfoneb.Length - 1] + 1);             }             catch             {                 variables.rhifAnfoneb.Add(1);             }         }     } }   I am getting the error (An object reference is required for the non-static field, method, or property 'variables.rhifAnfoneb') in              try             {                 variables.rhifAnfoneb.Add(variables.rhifAnfoneb[variables.rhifAnfoneb.Length - 1] + 1);             }             catch             {                 variables.rhifAnfoneb.Add(1);             }   I am sorry for different languages in same code but I am billingual and sometimes I set out to make an app in one language but then it slowly morphs to another.  If awnsering could you please awnser as simply as you could because I am new to c#  Any help would be greatly appreciated.  Eoin

Consider:  namespace WindowsApplication1 {     public partial class Form1 : Form     {         public Form1()         {             InitializeComponent();         }          private void button1_Click(object sender, EventArgs e)         {             //int[] val = { 0, 0};             int val;             if (textBox1.Text == "")             {                 MessageBox.Show("Input any no");             }             else             {                 val = Convert.ToInt32(textBox1.Text);                 Thread ot1 = new Thread(new ParameterizedThreadStart(SumData));                 ot1.Start(val);             }         }          private static void ReadData(object state)         {             System.Windows.Forms.Application.Run();         }          void setTextboxText(int result)         {             if (this.InvokeRequired)             {                 this.Invoke(new IntDelegate(SetTextboxTextSafe), new object[] { result });             }             else             {                 SetTextboxTextSafe(result);             }         }          void SetTextboxTextSafe(int result)         {             label1.Text = result.ToString();         }          private static void SumData(object state)         {             int result;             //int[] icount = (int[])state;             int icount = (int)state;              for (int i = icount; i > 0; i--)             {                 result += i;                 System.Threading.Thread.Sleep(1000);             }             setTextboxText(result);         }          delegate void IntDelegate(int result);          private void button2_Click(object sender, EventArgs e)         {             Application.Exit();         }     } }   Why is this error occurring?     An object reference is required for the nonstatic field, method, or property 'WindowsApplication1.Form1.setTextboxText(int)


I was just wondering whether it makes a difference if I mysql_real_escape data more than once?  So if I escaped data in one part of my website, and then again in another part of code. Would this be a problem? Or make a difference?

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


Is it theoretically possible to find $P$, $K$, and $K^\prime$ such that $E_K(P) = E_{K^\prime}(P)$ where $E$ is AES-128 and $K \ne K^\prime$? I'd imagine this would be infeasible, but is it actually impossible?

For $PT\in \mathbb{M}$ and $CT\in \mathbb{C}$, let $\mathbb{F}=\{f|f:\mathbb{M}\rightarrow\mathbb{C}\}$ be the collection of all functions from $\mathbb{M}$ to $\mathbb{C}$. Then AES encryption under key $k$ is one of these functions, say $f_k$, such that $f_k(PT)=CT$. Then,   Is there any key $k'$ such that $k\neq k'$, but $f_k(PT)=f_{k'}(PT)$? If so then is there any fixed cardinality of such sets of keys?


I am not sure if I understand the term damping coefficient correctly (I am a high-school student). Here's the link for the info that I learned:    So, as far as I understand, damping coefficient is $\gamma$. It's equation:  $$x/x_0 = e^{\gamma t} \, .$$  And another equation:  $$\gamma = c/2m \, .$$  $c$ as I understand it is decay constant. Although the website doesn't provide with such information.  However, one of the questions on the units of damping coefficient in this forum had an answer that said that $\gamma$ doesn't have units (). How can that be? I mean, I don't understand something. It should be s^-1 in this case. Are the equations flawed?  What I have in mind is underdamped case.  The graph I have looks like this:   So can I use the first formula $(x/x_0 = e^{\gamma t}$) to get $\gamma$, which is the damping coefficient, or the website has it wrong?

I've heard the terms "damping constant" and "damping coefficient" used to describe both the $c$ from the viscous damping force equation $F = -c\dot{x}$ and the $\gamma$ from the definition $\gamma = \frac{c}{2m}$. Is there standard usage for each term, or is it context dependent? If it is context dependent, are there terms which uniquely refer to each of $c$ and $\gamma$?


This is my work so far.    How can I isolate the $(a^2-b^2)$?  I am not asking for a full solution, just a hint and next step.    All done! Thanks Michael.

If $4\mid a+bc$ and $6\mid b+ac$ prove that $2\mid a^2-b^2$   This is as far as I get:  $$a + bc = 4k\qquad\text{for some $k\in\Bbb Z$} \\b+ac =6l\qquad\text{for some $l\in\Bbb Z$}\\\implies (a^2-b^2)(1-c^2) = 16k^2 + 36l^2$$


I made a small app in android studio, which is tic tac (XO) game. All was working fine and I've tested the app on the emulator many times. But at a moment the application crashed and the well known message says: Unfortunately, "tictactoe has stopped". And then I wasn't even able to start the app, all the time it crashes when trying to run it.   Android logcat showed those messages:     E/AndroidRuntime: FATAL EXCEPTION: main      E/AndroidRuntime: java.lang.RuntimeException: Unable to resume activity {.tictactoe/.tictactoe.MainGame}: java.lang.NullPointerException     E/AndroidRuntime:     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2575)      E/AndroidRuntime:     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2603)      E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2089)      E/AndroidRuntime:   at android.app.ActivityThread.access$600(ActivityThread.java:130)   With many more messages. Any help?  Update: more logcat:     E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)      E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99)      E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)

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 came across a code snippet which used a statement int k=(a++,++a) in it. I don't understand which type of statement is this (a++,++a) and how it will be evaluated. Why is the bracket is used here? Is it a function call?  Here is the code.  #include <stdio.h> int main(void) {     int a=5;     int k=(a++,++a);     printf("%d\n",k);     return 0; }   The output I get is 7 — why is that?

Have you ever tried this before?  static void Main(string[] args) {     int x = 10;     x = x++;     Console.WriteLine(x); }   Output: 10.  but for   static void Main(string[] args) {     int x = 10;     x++;     Console.WriteLine(x); }   Output: 11.  Could anyone explain why this?


Player A has a  (4/4 double strike) and decides to use the Bloodrush ability of , so now the Wrecking Ogre is a 7/7 with Double Strike + Trample.  If Player B decides to block it with 3 2/2 creatures, on the first combat, Wrecking Ogre's power will be down to 1/1,and that 1/1 will go to the player because it has trample.  My concern is about the second strike of wrecking ogre. Since there are no more blockers, will it deal 7/7 damage or 1/1 damage?  And if wrecking ogre is blocked by 2 5/5 creatures? Will it be dead before it can attack again? Will the Trample and Double Strike will be useless?

I understand that the double strike mechanic allows a creature to attack in both a first strike combat damage step and a normal combat damage step.  It's clear that when a creature with no other abilities aside from double strike is blocked that even if the defender has lethal damage marked in the first strike step that the additional damage does not carry forward to the player.  How does this view of double strike change with relation to trample and lifelink?  I believe the correct interpretations are (not accounting for other effects or abilities) that 2 times the attacker's power is marked as damage on the defender.  For trample this amount is reduced by the defender's toughness and additional damage carries forward as normal.  Similarly for lifelink the active player gains life equal to 2 times the attacker's power.  Thus a 10/10 trampling double striking life linker blocked by a 1/1 creature would deal 19 points of trample damage and the active player would gain 20 life.  Is this interpretation correct?


Preface:  This question is, IMO, not a duplicate of "", for these reasons:   Only bullet "1." of my question seems to be partially addressed in the above question, which doesn't talk about reopen voting in any way (only about close voting). The above question does ot explain anything about bullet "2." and "3." of my question. The above question in no way addresses the scenario related to example C, where the real answer to that part of my question is included in the comment quoted near the end of my question.     Assume a question which was put on hold as the result of voting via the Close votes review queue (on any SE site), as shown in : below the link to the actual , it shows the typical (in red) "completed".  Similar for the result of voting via the Reopen votes review queue (on any SE site), as shown in : below the link to the actual , it shows the typical (in red) "completed".  However, there are questions where such "completed" is not shown:   Example A where below the  it says "invalidated" (not "completed"): Example B where below the  it says "invalidated" (not "completed"): Example C where below the  it says "invalidated" (not "completed"):   My questions:   What does such "invalidated" actually mean? What are possible cases where this happens? Who or what actually "invalidates" such reviews of close or reopen votes, and why?   Update 1:  My "impression" is that something happens (gets triggered) by a moderator-like intervention, maybe something like "stop this close/reopen voting" and my (next) guess is that such event then pulls the "invalidated" trigger. I may be wrong (just guessing), but that is what I saw happening in various similar cases over the recent past (and via this question I try to understand if there is such a thing, and if so what it is).  Update 2:  The existing answer to my question here, appears to be an answer for Example A and B. But IMO it does stil not explain Example C. So until an even better answer arrives that also explains Example C, I accept this answer.  Update 3:  Note this comment below the accepted answer:     Sorry, I misread the dates. That one got invalidated because of a bug that existed back then (I believe it got fixed last year). Essentially any reopen vote causes the edit to be ignored, but the system only considered reopen votes at least 15 minutes old for review cases. So if the system updated review within that 15-minute, it would think the task is invalid because the edit doesn't qualify and the only reopen vote isn't old enough. It would kill the task and wouldn't recreate it unless a second reopen vote came in. I forget how it was fixed, I think we started ignoring the reopen vote time.   Only this comment should illustrate what I wrote in my "Preface" above ...

Recently I flagged  as a duplicate. A few days later, when I checked it again to see if it was closed, I realized it wasn't.    Searching in Meta brought me to , where a comment suggested checking the timeline. So I checked the  and saw that the close flag was set as invalidated.  Does this mean that it was disputed? When I click on it I see only "This item is no longer reviewable." Do I need more reputation (3000+ ?) to view more detailed information?


I was planning to upgrade my users from version 3.4 to 3.5 and 3.6 using major push upgrades. I am able to go to "Setup > Create > Packages > Versions > Push Upgrades > Schedule Push Upgrade" But the only options I get is to push minor versions, ie from 3.4.1 to 3.4.2 or 3.4.X.  I did create a case with Salesforce support and according to support, my org is activated with Push Major capability.   How do I use Push major versions? Is there some other screen I should be looking at? My developer Org is Summer '13, is it something visible only in Winter '13 or doesn't this matter?

We are ISV Partners and all of our packaging orgs have been upgraded to Winter 13. One of the features of Winter 13 was supposed to allow us to push major release versions to subscriber orgs. I would have expected it to be in the previously existing "Push Upgrade" section of our packaging orgs, but that still only allows pushing patch versions.  If it didn't make the final Winter 13 release, I would have expected Salesforce to take it off the release page. Is this something we have to ask to be enabled?


Can I delete my own question which has an answer awarded with a bounty?

What circumstances can cause a question or answer to be deleted, and what does that actually mean?    How can a post be deleted? When can't I delete my own post? Can I still see my post even after it's deleted? Can I see a list of my deleted posts? How can I undelete one of my posts? What does deletion mean for a post? How do votes to delete work? What are the criteria for deletion? What else should I know about deleted posts? If I flag my question with a request to delete it, what will happen?       For more information, see the articles about  and  in the .


We have two sites/blog, and now we are merging the two blogs into one blog. We move content from domain2.com to domain1.com. What should I consider when it comes to SEO. Should I move all the traffic from domain2.com to domain1.com? And then 301 redirect articles from domain2.com to matching the imported articles at domain1.com?

I have two domains (.com and .co.uk) with different websites. In .co.uk domain I have a good ranking and my idea is to redirect the .co.uk domain to .com. I think I have to use 301 redirect.  My questions is, I have two different websites, the two websites are different but with the same categories and some products, I have to create only one redirect of home to home or a should create other pages like similar products, categories and other similar pages in both sites?  The created backlinks usually goes to homepage, so I thought I just needed to redirect the homepage.  I don't want to lose the ranking and have problems with Google crawl.


Reading package lists ... Error!  E: Encountered a section with no Package: header  E: Problem with MergeList / var/lib/apt/lists/www.beerorkid.com_compiz_dists_dapper_main-amd64_binary-i386_Packages  E: Could not parse or open package lists or status file.   how to fix? Because of this, it open almost nothing  I try to do an update and...  E: Error with GPG : http://www.beerorkid.com dapper Release : The following signatures were invalid : NODATA 1 NODATA 2

The computer gave me this output in a window:  E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages E: The package lists or status file could not be parsed or opened.   How can I fix this?


I have a tablet PC running windows 8.1 but I want to install Ubuntu. It has UEFI.   How to do it?

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?


Let $A$ be an integral domain and $A[X,Y]$ the polynomial   ring in two variables with coefficients in $A$. Let $m, n ∈ \mathbb Z_{≥1}$ be positive integers. Claim: the ideal $(X^m − Y^n)$ is prime in $A[X, Y ]$ iff $m$ and $n$ are coprime.   I got the following hint but I couldn't figure out how to proceed the proof. Please give me a more details hints. "For the ”if” direction: Show that the map $ϕ : A[X, Y ] → A[T], f(X, Y ) → f(T^n, T^m)$ is a ring homomorphism, which factors over a ring homomorphism $\bar ϕ : A[X, Y ]/(X^m − Y^n) → A[T]$. Then show that $\bar \phi$ is injective."

I am trying to show that $X^n-Y^m$ is irreducible in $\Bbb{C}[X,Y]$ iff $\gcd(n,m)=1$ where $n,m$ are positive integers.    I showed that if $\gcd(n,m)$ is not $1$, then $X^n-Y^m$ is reducible. How to show the other direction. Please help.


Ok, I know trolls didn't fight at Erebor in the book; Jackson decided to include them in the film.  Shouldn't they have turned to stone during the day?

I've been watching The Hobbit Extended Edition, and saw the scene where the dawn light inundated the three trolls, who promptly turned to stone. What I have to wonder is, why do the trolls turn to stone when exposed to sunlight? I'm aware that not all do so, but why these ones? Is it something to do with their origins or nature?


I had a question.  I came here first to look for an answer.  There was no answer here.  I then went to google and found an answer.  I wondered if I should ask the question here and perhaps supply the answer myself (the one I found on google).  Can I, should I do that?  Maybe the difference is in being a passive or active user of stackexchange?  Not sure.

Meta appears to have come to a consensus that when a user asks a question that is easily answered with Google that we should not close the question but rather answer it properly.        However, what does this mean about asking questions that can be answered easily with a Google search?  More specifically, should we encourage or discourage such behavior, and how?  Here are some reasons that I can think of for each option.  Reasons to Encourage  ""   And that includes answers easily accessible via Google search   Sometimes we want to  another answer to a  that   Sometimes we want to save others the Google searching we did by asking and answering the question ourselves. In this case, we did do the research, but the question by necessity must not show research effort.  Reasons to Discourage  Question quality may drop, as users will feel less incentive to Google their problem. This will also probably result in a greater quantity of questions as well that have already been answered on StackOverflow, as Google searches often result in StackOverflow answers.


I know, this is an old question that has been asked many times . I agree with the common answer that #include <filename> should be used for system headers and #include "filename" should be used for project-local headers.  However, now I found  from the ISO/IEC C++ Tools Working Group, which states the following:     All headers within a project should be included using the <> style inclusion and contain the project name as a directory prefix. And all headers means all headers public, private, or implementation detail, in executables or in libraries.   They also give an explanation:     The problem with the "" style inclusion is if the header is not found relative to the including file, most implementations will continue looking for it in the include search paths, the same as for <>. As a result, if the header is not present in the right place (for example, because it was mistakenly not listed as to be installed), chances are that a completely unrelated header with the same name will be found and included. Needless to say, debugging situations like these is unpleasant.   I don't understand this. Why does this problem not occur with the <> style?  Bonus question: What's the status of such a paper anyway? Can it be considered an official recommendation of the ISO/IEC C++ consortium, peer-reviewed and acknowledged by many experts? Or is it just a proposal by someone in order to trigger a discussion?

In the C and C++ programming languages, what is the difference between using angle brackets and using quotes in an include statement, as follows?   #include <filename>  #include "filename"


Let V be an inner product space,and suppose that $x$ and $y $ are orthogonal vectors in V.We also know $\left\lVert x+y  \right\rVert^2=\left\lVert x  \right\rVert^2+\left\lVert y  \right\rVert^2$.My question is how can we deduce the pythagorean theorem in $\mathbb R^2$ from it.If possible give geometrical views.  Any help will be greatly appreciated.  thanks!! in advance.

I've got a question concerning how to proof the Pythagoras theorem using the following assumption:  $x$ is perpendicular to $y$ (if and only if) $||x+y||^2 = ||x||^2 + ||y||^2$, where $x$ and $y$ are vectors.  I have a basic understanding of linear algebra, however I'm a beginner with this. The question provides hints how to prove the above mentioned equation.  Namely that I should use the properties of the dot product and the definition of the norm of a vector. Those being symmetry, scaling and distributivity as the dot product properties and the norm of a vector being the squared root of the dot product between the same vector.  I was thinking about using the fact that if a vector is perpendicular to another vector the dot product between those vectors should be 0. But that is not provided as a hint so I'm not sure. I know the under lying thought behind it is the cosine rule for vectors, that being:  $$x\cdot y = ||x||\,||y|| \cos(\theta)$$  If the angle between the two vectors is perpendicular you should use $\cos(\pi/2)$ which is $0$ and $||x||\cdot 0 = 0$ and $||y||\cdot 0 = 0$ with the vectors not necessarily being $0$. Thus $x\cdot y = 0$. How would I apply this to the equation I first mentioned to prove the Pythagoras theorem?  I have a few more thoughts on how I could prove this but I'm not sure if they're correct.  I hope someone could point me in the right direction.


I am trying to locate owner of domain:  LinkedInPro.CO   I have reviewed WHOIS and it states REDACTED FOR PRIVACY.  Further, Admin Email: Please query the RDDS service of the Registrar of Record identified in this output for information on how to contact the Registrant. Thanks in advance!

When I search whois data for some domains for example, liquid-solutions.biz, I get the following:  Registrant Email: Please query the RDDS service of the Registrar of Record identified in this output for information on how to contact the Registrant, Admin, or Tech contact of the queried domain name.   What does this mean and how to query RDDS service?


I have a 5-year Type-C Schengen visa and I went to the Netherlands on October 17, 2017 for approximately two months. After that I haven't been to any Schengen country until today. Currently I am planning to go to the Netherlands again on August 10, 2018. Am I allowed to enter the Netherlands without applying for another visa? I am not sure about this 180/90 days rule.  Thank you.

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


Given 3 points, $(x_1, y_1), (x_2, y_2), (x_3, y_3)$, how might I find an equation intersecting all of these points? Given just 2 points, to find a linear equation, this is the formula: $$y\ =\frac{\left(y_2-y_1\right)}{\left(x_2-x_1\right)}x+\frac{\left(y_1+y_2-\left(x_1\left(\frac{\left(y_2-y_1\right)}{\left(x_2-x_1\right)}\right)+x_2\left(\frac{\left(y_2-y_1\right)}{\left(x_2-x_1\right)}\right)\right)\right)}{2}$$ In the same form of $y=...$, what is the formula for a quadratic equation with 3 points?

I came home from school today, pulled out my homework, now I'm stumped.  I don't want the answer, I just want to know how to do it.  Here is the question that I'm reading:  Determine a quadratic function in standard form for the set of points $(x_1,y_2)(x_2,y_2)(x_3,y_3)$  Where the $x$'s and $y$'s represent the points.  Here are the points I am working with (remember, I don't want the answer, I just want to know how to do it, there are lots of questions on this so I want to be able to know how to do it).     $(-1, 2), (0, 1), (1, -4)$   Thanks!


I have tried proving the following question using contradiction, but I am not sure if that totally makes sense. The question is as follows:     Prove that if $a, b \in \mathbb{Z}$ and $a^2-3b^2$  is divisible by 4, then at least one of $a, b$ must be even.   So, here is my attempt: Asume for a proof by contradiction that $a, b \in \mathbb{Z}$, $4|a^2-3b^2$, and both $a$ and $b$ are odd. Now, let $a = 2k + 1$, $b = 2m + 1$, for some $k, m \in \mathbb{Z}$ and substitute it into $a^2-3b^2$. $$a^2-3b = (2k+1)^2 -3(2m+1)^2$$ $$=4k^2+4k-12m^2-12m-2$$ $$=2(2k^2+2k-6m^2-6m-1)$$ This is contradiction since $4$ does not divide $a^2-3b^2$ if both $a$ and $b$ are odd. $\square$

I am trying to prove old test exercises and this one is resisting me.  I know you can believe that I meant $a^ 2 + b ^ 2$ is divisible by 4, but no, in the test it says that 4 is divisible by $a ^ 2+ b^2$.  Suppose that $ a,b \in \mathbb{Z}$  If 4 is divisible by $ a^2 + b^2$, then $a$ and $b$ are not odd.  I started like this:  Suppose that a and b are even, then $a = 2m$ and $b = 2n$ for some $m,n \in \mathbb{Z} $.   Thus  $$ a^2 = (2m)^2 \ \mbox{and}\ \  b^2= (2n)^2$$ $$ a ^2 + b^2= (2m)^2 + (2n)^2$$ $$ a^2 + b^2 = (4 m^2 + 4n^2) = 2(2m^2+2n^2) $$  Now $$2m ^ 2 + 2n^2\in \mathbb{Z} = k$$ Then  $$ a^2+b^2= 2k$$  Is this a correct proof?/ Any better ways to prove this.  Sorry for the lousy English. Thanks.


I'm trying to change the color of my typeface on photoshop so i selected  solid color layer and set the blend mode to color but the color of the   typeface didn't change as the color i selected but only the outline of typeface.  how do i change the color of the typeface clearly with the solid color just like the picture below? (done by someone else)

i used masking + Gaussian blur + curves on my typeface on photoshop  after all, i wanted to change the color of typeface by   clicking the letters using magic wand,   but the shape of letter is changed as i filled colors on it. (the typeface becomes thicker)  how can i change the color of typeface?


There are many variations of this problem but for concreteness I'll stick to one.  I roll a 6 sided die and a 4 sided die, what is the probability the sum is over six?  Very trivially I could make a table with all the outcomes and count 14 out of 24 cases.  However I may be asked this question during an interview, and constructing a table might take a while and is prone to errors. Is there a trick to this problem that I'm missing? Or in other words is there a way to solve this problem that's simpler than constructing a table of outcome?  ===Edit=== Distribution methods are nice, but for in an interview this solution might be too cumbersome

In D&D players roll a 20 sided die trying to beat a set number to determine if an attack hits the target. Players often can add modifiers to this roll to help the odds in reaching this target number. If the target number (enemy armor level) is passed by the attack roll, damage is done to the target which requires a different roll depending on the power of the attack. If the armor level is matched for that attack roll, damage is calculated like normal (rolling dice, adding modifiers) and then halved, rounding down to the nearest integer.  One of my spells allows me to do three attacks at once on one creature, and on a hit deals 2 6-sided dice +2 damage.  It so happened I used this spell on my "Ally" and I'm trying to figure out what my chances of actually killing him were.  I roll a 1d20 (1 20-sided die) and add +4 to the roll and if that result is greater than or equal to 16 (my 'Allies' Armor level), I roll damage which is 2d6+2 (halfing then rounding down the damage if the attack equaled Armor level). That damage result is then subtracted from my 'Allies' starting Health which is 20.  I repeat this 2 more times, adding damage on each hit. If his health reduces to 0 then he is dead. If his health is 1 or more by the end of this attack he lives and gets to attack me.  I want to know, statistically what percentage of time will my Ally be reduced to 0 health after doing this spell?


I have installed wine and I am afraid that viruses will affect my PC now. I will not open any other .exe file other than mine one (which I use everyday)

Just wondering if installing Wine might open up a fairly solid Linux desktop to the world of Windows viruses.  Any confirmed reports about that?  Would you then install a Windows antivirus product under Wine?


I am building an iOS app and it is still in early stage for testing. My QA actually lives in another state and I can't install my app to his iOS device with physically connected option.  Is there a way that I can send the iOS app package to my QA and he can install it somehow in his physical device? Also, this app is still in early testing phase so I don't think we are ready for app store approval.

How can you beta test an iPhone app?  I can get it on my own device, and anyone that gives me a device, I can run it on theirs, but is there a way to do a limited release via the app store for beta testing?  Related: Also, see  on getting your app onto phones without using the App Store.