If $y^y=x$, can $y$ be expressed as a function of $x$?
Is $x^x=y$ solvable for $x$?
Embedding C++ Objects into QML with Context Properties According to Qt5 documentation:  all public slots of C++ classes that inherit from QObject, are accessible from QML Here what I did:  C++  class MyClass : public QObject {     Q_OBJECT  public slots:     void doStuffFromQmlSlot()     {         qDebug() &lt;&lt; Q_FUNC_INFO;     }  public:     MyClass()     {         qDebug() &lt;&lt; Q_FUNC_INFO;     } };   my main.cpp contains:  MyClass myClass; QQmlEngine engine; engine.rootContext()-&gt;setContextProperty( "myclass", &amp;myClass ); QQmlComponent component( &amp;engine, QUrl::fromLocalFile("qml/qtquick-01/main.qml") ); component.create();   QML  import QtQuick 2.0  Rectangle {     width: 360     height: 360     Text {         text: qsTr("Hello World")         anchors.centerIn: parent     }     MouseArea {         anchors.fill: parent         onClicked: {             myclass.doStuffFromQmlSlot();              Qt.quit();         }     } }   Actually the QtCreator seems to recognixe the exposed myclass object into the QML as it enables auto-completion of both class name (myclass) and the public slot doStuffFromQmlSlot(). When I run the application I unfortunately got the following error:  ReferenceError: myclass is not defined  Any clue on what I'm doing wrong? Combinatorics - binary - very interesting question I tried to solve this problem without any success. I really hope that you will know the answer. $f(n,m)$ presents the number of binary strings (empty string included) that include at most n times '1', and at most m times '0'.      Prove: $$f(n,m) = \binom{n+m+2}{n+1}-1$$ Prove that $f(X)$ and $g(Y)$ are independent if $X$ and $Y$ are independent Let $X$ and $Y$ be independent random variables. Prove that $f(X)$ and $g(Y)$ are independent for any choice of measurable functions $f$ and $g$.   This sounds very obvious, but I have no idea how to approach it.  EDIT: Two random variables are independent if $\Pr\{X = x \text{ and } Y = y\} = \Pr\{X = x\} \cdot \Pr\{Y = y\}$ How can I bring back the old menu style on Chrome 28 onwards, now that the --disable-new-menu-style switch has been removed? Where can I get a Thunderbolt hub or splitter? Apple has just announced the new MacBook Airs, Mac mini, and Thunderbolt display. One of the features of the Thunderbolt display that caught my eye was its ability to daisy-chain two displays together from one Thunderbolt port (on a MacBook Pro).  I already have two 24" monitors and I don't feel like paying for two £900 displays. I worked out that all I need is a Thunderbolt hub/splitter so that I can plug the two cables that emerge into mini DisplayPort-to-DVI adapters.  Does anyone know of any Thunderbolt hubs or splitters? Or does anyone know of an alternative method? Is it possible to unwrap materials made in Vertex Paint? I painted an group of objects in Blender using the Vertex Paint and was wondering if it would be possible to unwrap the mutliple materials(when the objects are joined together using Ctrl+J)? Do I have to paint it all over again? Configure up-arrow to browse through commands with same initial characters rather than all previous commands On the bash command-line, ↑ gives me the previous command. On the command-lines in ipython or matlab, when I type a few characters, ↑ gives me the previously entered command starting with those characters. How can I enable exactly this behaviour in bash? I am aware of more advanced ways of searching through the command-line history, but sometimes a simple way is more convenient. I have a layer of georeferenced points, and a layer of vectorized borders. Is there a way I can use QGIS to calculate how many points fall within each area of the borders layer? Reference sObject Fields dynamically from a string value Is it possible to reference the fields of an sObject (opportunity in this example) dynamically from a string value? For example, take the following code:  for(Opportunity o: oppList) {       for(String s : strList) {            // I'd like to set the opportunity field values based on the string             // value that contains the API name of the opportunity field       }  }  So, the variable strList contains the opportunity API field names. I'm trying to clear some fields on the opportunity in a before update trigger, but I have to access the field names dynamically in the strList. I have a project that needs a different voltage (or multiple voltages) than what I have available. Sometimes I need DC instead of AC, or I need a lower or higher voltage. How do I convert from one to another? Should I use resistors or a regulator or something else?  I've heard of converters, transformers, regulators, inverters, step-down, step-up, buck, boost, switching, linear, and other terms. Or acronyms (initialisms) like PMIC and LDO. Can someone shed some light on all this? "Could not identify document class." error when trying to count words I'm trying to count words in a cyrillic LaTeX document with .  I run the command perl texcount.pl index.tex and get following output:  D:\wd&gt;perl texcount.pl index.tex  !!! Could not identify document class. !!! File: index.tex Encoding: utf8 Words in text: 0 Words in headers: 5 Words outside text (captions, etc.): 0 Number of headers: 1 Number of floats/tables/figures: 0 Number of math inlines: 0 Number of math displayed: 0  (errors:1)   index.tex starts with following line:  \documentclass[a5paper,pagesize,10pt,bibtotoc,pointlessnumbers, normalheadings,DIV=9,twoside=false]{scrbook}   So documentclass tag is present.  How can I fix this error? Inequality $\sqrt{1+x^2}+\sqrt{1+y^2}+\sqrt{1+z^2} \le \sqrt{2}(x+y+z)$ If $x&gt;0$, $y&gt;0$, $z&gt;0$ and $xyz = 1$ then   $$\sqrt{1+x^2}+\sqrt{1+y^2}+\sqrt{1+z^2} \le \sqrt{2}(x+y+z)$$   I tried using $\displaystyle x = \frac{a}{b},y = \frac{b}{c}$ and $\displaystyle z = \frac{c}{a}$ substitution,  $\displaystyle \sum_{cyc} \frac{\sqrt{a^2+b^2}}{b} \le \sqrt{2}\left(\frac{a}{b}+\frac{b}{c}+\frac{c}{a}\right) \\ \displaystyle  \iff 6+ 2\sum_{cyc}\frac{\sqrt{(a^2+b^2)(b^2+c^2)}}{bc} \le \sum_{cyc}\frac{a^2+b^2}{b^2} + 4\sum_{cyc}\frac{b}{a}$  So it would suffice if we showed $\displaystyle \sum_{cyc}\frac{\sqrt{(a^2+b^2)(b^2+c^2)}}{bc} \le 2\sum_{cyc}\frac{b}{a}$  Squaring again does not lead anywhere nice. Is the last inequality true ? If not is there a better way of showing the result ? pgfplots fillbetween with multiple curves What happens to matter in a standard model with zero Higgs VEV? Suppose you reset the parameters of the standard model so that the Higgs field average value is zero in the vacuum, what would happen to standard matter?  If the fundamental fermions go from a finite to a zero rest mass, I'm pretty sure that the electrons would fly away from nuclei at the speed of light, leaving positively charged nuclei trying to get away from each other.  Looking at the solution for the Hydrogen atom, I don't see how it would be possible to have atoms with zero rest mass electrons.  What happens to protons and neutrons?  Since only a very small part of the mass of protons and neutrons is the rest mass of the quarks, and since they're flying around in there at relativistic speeds already, and since the nuclear force is so much stronger than the electrical force with an incredible aversion to naked color, would protons and neutrons remain bound assemblages of quarks and virtual gluons?  Would they get a little larger?  A little less massive?  What would happen to nuclei?  Would they stay together?  If the protons and neutrons hold together and their properties change only some, then I might expect the same of nuclei.  Different stable isotopes, different sizes, and different masses, but I would expect there would still be nuclei.  Also the W and Z particles go to zero rest mass.  What does that do to the electroweak interactions?  Does that affect normal stable matter (outside of nuclear decay modes)?  Is the weak force no longer weak?  What happens to the forces overall? Choice function for collection of arbitrary finite sets. AC required? Will be glad for a little hint: let x and n be positive integer such that $1+x+x^2+\dots+x^{n-1}$ is a prime number then show that n is prime What do ref, val and out mean on method parameters? I'm looking for a clear, concise and accurate answer.    Ideally as the actual answer, although links to good explanations welcome.  This also applies to VB.Net, but the keywords are different - ByRef and ByVal. In other words, what is the Drupal 8 equivalent of ?  Drupal 8 still uses hook_menu(), but for what I can see, the information returned by the hook is different from what the hook returned in Drupal 7. For example, the definition given in user_menu() for user is the following.    $items['user'] = array(     'title' =&gt; 'User account',     'title callback' =&gt; 'user_menu_title',     'weight' =&gt; -10,     'route_name' =&gt; 'user_page',     'menu_name' =&gt; 'account',   );   The route_name property links to an entry in the  file.  user_page:   pattern: '/user'   defaults:     _content: '\Drupal\user\Controller\UserController::userPage'   requirements:     _access: 'TRUE'   This is different from what done with Symphony, and it confuses me about how a module can alter the route defined from another user.  The only function that is still invoking hook_menu_alter() is menu_router_build(), but that function still contains code that needs to be updated, since it is still using the now deprecated drupal_alter().    // Alter the menu as defined in modules, keys are like user/%user.   drupal_alter('menu', $callbacks);   foreach ($callbacks as $path =&gt; $router_item) {     // If the menu item is a default local task and incorrectly references a     // route, remove it.     // @todo This may be removed later depending on the outcome of     // http://drupal.org/node/1889790     if (isset($router_item['type']) &amp;&amp; $router_item['type'] == MENU_DEFAULT_LOCAL_TASK) {       unset($callbacks[$path]['route_name']);     }     // If the menu item references a route, normalize the route information     // into the old structure. Note that routes are keyed by name, not path,     // so the path of the route takes precedence.     if (isset($router_item['route_name'])) {       $router_item['page callback'] = 'USES_ROUTE';       $router_item['access callback'] = TRUE;       $new_path = _menu_router_translate_route($router_item['route_name']);        unset($callbacks[$path]);       $callbacks[$new_path] = $router_item;     }   } What should we do with old, very popular closed questions? Motivated by the deletion of     On one hand, I disagree with these closures, because:  These questions were (and still are) very popular They have some good information in them (or at least the first one does) and it feels like bad sportsmanship to remove good information from the internet, particularly when it was contributed by your fellow users  Number 2 in particular bothers me. A lot. On the other hand, I do agree that:  The community of 10k users should be able to decide which closed questions they wish to delete on their own without me intervening These questions should definitely remain closed, because they either have an absurd # of answers, or are duplicates (though some duplicates ). Which means they are eligible for deletion … forever. These questions wouldn't survive more than 10 minutes if asked today on Stack Overflow, so in some ways they are artifacts from the past, like dinosaurs in an era of mammals.  There is some related discussion in:   While I normally favor code solutions here, I am not sure I like the idea that once a question gets 400 upvotes it should become extremely difficult to delete. It feels like mob rule. Official policy on the blog: Compiling LaTeX document empties .bbl file I'm trying out biblatex for the document I'm compiling, using the biber backend on my miktex distribution. Everything, including biber, should be up to date, assuming the MiKTeX repository currently holds the latest versions of everything.  This is what the biblatex documentation (p. 101) says about how often I have to run biber to update my .bbl file:     Whenever a reference to a work which has not been cited before is   added, this procedure must be repeated. This is also the case if the   last reference to a work which has been cited before is removed   because some citation labels may change in this case.   So if I make changes to my document (which is a very common activity in the process of writing a document), but leave the citations unchanged, I should not have to re-run biber before compiling the changes. However, every time I compile my document, regardless of the compiler or documentclass, the .bbl file is emptied. Consequently, the next time I compile the document without running biber, the bibliography is removed (seeing as the .bbl file contains nothing), and all my citations are broken. For this reason, I have to run biber before every time I compile the document, which largely counters the benefit of externalizing the bibliography in the first place.  How can I make the compilers stop overwriting my .bbl file and make everything behave as described in the biblatex manual?  Upon investigating the contents of the auxiliary files, I found that the .bbl file (after running biber, before compiling) begins with the following lines:  % $ biblatex auxiliary file $ % $ biblatex bbl format version 2.3 $   Does the biblatex version 2.8 still mark the .bbl files as version 2.3? If not, could this be the problem? And if so, why does my 2.8 version of biblatex (partly) behave as version 2.3?  Any help solving this problem would be much appreciated.