I have a static array inside a class template. The linker complains about a undefined symbol and even after applying the tips I saw on the web, I can't figure out what goes wrong.   Header  template&lt;unsigned int N1, unsigned int N2&gt; class Foo  { private:     static const int Size = N1 * N2;  public: // stuff  private:     static float mArray[Size];  }   CPP  template &lt;unsigned int N1, unsigned int N2&gt; float Foo&lt;N1, N2&gt;::mArray[size] = {0};   The linker complains about Foo&lt;...>::mArray not being defined. I got it to compile (and link) when I move the definition to the header but I know that this is bad practice for statics. What is the best approach here?  Cheers
Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)
I got the following problem: Right now I am checking my equations, which are usually written in align. This looks great in most of the cases, but sometimes the pagebreaks are weird, ie there is a lot of vertical whitespace left (like 2.5cm) at the end of a page. I made the following MWE to illustrate this.  \documentclass[a4paper, 12pt, headsepline]{scrreprt} \usepackage[onehalfspacing]{setspace} \usepackage{amsmath, amssymb, mathtools} \usepackage{mathptmx} \usepackage[a4paper]{geometry} \geometry{left=2cm,right=5cm,top=2cm,bottom=2cm} % \usepackage{lipsum} %\lipsum \usepackage[pangram]{blindtext}  \begin{document} \Blindtext[1][3]%1 paragraph, 3 pangrams \begin{align} X_{t+1} &amp;=  \frac{X_{t+1}+X_{t+1}}{Y_t}  \label{eq:1}  \intertext{Solving...:} \notag  X_{t}  &amp;=  \frac{X_{t+1}+X_{t+1}}{Y_{t+1}} \notag \\ \intertext{Solving further...:} \notag  % ===PAGEBREAK HERE: 2nd page begins=== &amp;= \frac{X_{t+1}+X_{t+1}}{Y_t} +  \frac{X_{t+1}+X_{t+1}}{Y_t}  \notag \\ &amp;= \frac{X_{t+1}+X_{t+1}}{Y_t}...  \notag \\ \intertext{Solving further...:} &amp; = \frac{X_{t+1}+X_{t+1}}{Y_t}  \notag \end{align}  \end{document}   In the MWE, the first 'Solving further' should be on the first page instead (to save space and it would also look better I guess?). The position where I would like the pagebreak to be is also marked as a comment in the MWE.  My question is first on a general basis: Which is the best environment to achieve multiple line equations, which can be aligned as in align, and to save space at the same time? Or to be more precise: If possible, I'd like to stick with align and adapt the pagebreaks only if necessary.  Thanks! This is a  about  the use of a *AMPP's stack.    I recently had a talk with some experienced people and they suggested to me not to use a WAMP stack, and instead install apache, mysql and php separately.  I don't understand why they have suggested this, though, so can anyone tell me?  Is there a particular disadvantage of WAMP, or a particular advantage to installing all of them separately?  Since a WAMP stack itself is composed of apache, mysql and php, then what's the difference between using the WAMP stack and installing them all separately? What's the best way of checking if an object property in JavaScript is undefined? Complex Exponent of Complex Numbers How does one find the algebraic solution of a Complex number raised to the power of another Complex number?  Here is the work I have done so far, if there are any mistakes please inform me.  A real number with a Complex Exponent: $$A \in \Bbb R, \space z \in \Bbb C,\space z = x + iy$$ $$A^z = A^{x+iy} = A^xA^{iy}$$ $$\implies e^{iy\ln A} = A^{iy}$$ $$\exp(iy\ln A) = \cos (y\ln A)+i\sin(y\ln A)$$ $$A^z = A^x[\cos (y\ln A)+i\sin(y\ln A)]$$  A Complex number with a Complex Exponent: [Using previous variables] $$C \in \Bbb C,\space C = a +bi\space|\space re^{i\theta}, \theta =\arg C$$ $$C^z = (a+ib)^z$$ [After previous mistake the following notes are inaccurate] $$C^z = a^x[\cos (y\ln a)+i\sin(y\ln a)] + ib^xib^{iy}$$  And this is as far as I could go as the expansion of $ib^xib^{iy}$ is being problematic. Could I have some help with this expansion? My fiancée and I are looking for a good Caribbean cruise in October and were wondering which islands are best to see and which Cruise line to take?  It seems like a lot of the cruises don't run in this month due to Hurricane season so I'm looking for other good options.  EDIT We'll be travelling in 2012. How do I  prevent .xsession-errors from eating disk space? Is there any way to completely disable the .xsession-errors file?  I have it as a symlink to /tmp so that my laptop hard disk can (hopefully) go to sleep for once, but at least 95% of the stuff in the file (it fills up at about 500k an hour) is...  (nautilus:1618): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed  which is total garbage to me.  I have tried doing a symlink to /dev/null but that does not work (the resulting link is overwritten), and I also do not want the activity so that hopefully my laptop can go to sleep for once.  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Emergency stop. &lt;read *&gt;   l.2 \usepackage                {amsmath}\usepackage{amssymb}^^M *** (cannot \read from terminal in nonstop modes)   Here is how much of TeX's memory you used:  10 strings out of 495062  226 string characters out of 1182645  45108 words of memory out of 3000000  3285 multiletter control sequences out of 15000+50000  3640 words of font info for 14 fonts, out of 3000000 for 9000  28 hyphenation exceptions out of 8191  10i,0n,7p,80b,8s stack positions out of 5000i,500n,10000p,200000b,50000s No pages of output. I'm using Bash on both client and server. When running a command over SSH:   ssh &lt;host&gt; 'declare' gives a list of shell variables. ssh &lt;host&gt; 'mount' gives a list of mountpoints.   However, declare is a Bash builtin, while mount is an external command. How does SSH know which to run if there is a shell builtin and an external command with the same name on the server? Read MIME data using PHP How do I remap certain keys or devices? 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First, I assume the contrary that there exists a bijection $f$, and I can find an element in $S$, but not in the range of $f$. But I can't find such element. How can you construct such $f$? How to pull data from internal memory on an unrooted phone? Yesterday, I suddenly discovered that I had lost all the user files on the internal memory of my android phone. All my photos, my music, my PDFs, audio recordings, everything. I will explain the events leading up to this in a separate paragraph below.  I have a Lava Z90 phone and I do not use an external SD card, so I must work with my phone to recover all data. I've been googling and following stuff I get from the internet(including Stack Overflow). Here's what I have done so far.   Tried using photo recovery apps available on Play Store. None of them worked. Decided to go more technical. Enabled USB Debugging and OEM Unlocking from Developer options in my phone. Then I used ADB pull command, pull /dev/block/mmcblk0 /home/data.img to try create an image of the entire internal storage so I can analyse it using PhotoRec. It says pull: not found I assumed this is because my phone isn't rooted?  I tried to root it with the KingoRoot apk but that didn't work. I have Ubuntu on my PC and there is not KingoRoot for Ubuntu. My next step would be to use Wine to run KingoRoot on my machine and try to root my phone that way.   I have the following questions:   How can I create an image, a data dump of my entire internal storage that i can later analyse for my data? Can I do it with an unrooted phone? If not, how can I root my phone with ADB? Am I going about this right? Is there a better, easier way to recover data that I should use instead?   Thank you very much.  How I lost my data  I recently uninstalled the TikTok app from my phone. Yesterday I connected my phone to my PC over mtp and found that there were certain leftover folders on the internal memory. One was a folder with Chinese name, one was a folder called ByteDance and one folder called Thumbnails. I assumed that the first two were leftovers from the TikTok app and the third was mere thumbnails. So I deleted them to save space. Nothing happened that day, except that I couldn't access any of my WhatsApp images through WhatsApp(they were still accessible through the gallery). However, when I woke up the next morning, all my data on the internal memory was gone. I still have contacts my messages and my settings, just that everything that was accessible through the file explorer has disappeared. Ubuntu gets stuck in a login loop Meaning of convolution? I would like to be able to set a flag at the beginning of the main flag (say output) that tells if I want to produce a paper document or an electronic document.   Then I should check this flag to define or not empty pages, hypperref, oneside or twosides, etc.  How could I do that ? Schwarz's Lemma, fixed points question This is from an old qualifying examination question.  If f is holomorphic in the unit disk $D$ and $|f(z)|&lt;1$ for all $z\in D$. Suppose also that $f$ has two distinct fixed points in $D$ then $f(z)=z$ for every $z\in D$  I know that I have to use the Schwarz's lemma and may be make use of Möbius transformations. I tried setting $g(z)=\phi_a\circ f\circ \phi_{-a}$. But that does not seem to work because I don't see why $|g(z)|=|z|$ for some non zero $z$.   Any helpful hints are greatly appreciated.  Edit: Of course the $a$ above is one of the fixed points. In reading I am not sure if the issue below could have something to do with needing a custom wordpress ajax handler? All of these functions are inside my functions.php file. I have a couple of PHP functions that are supposed to pass information from one to another. The an AJAX call to the final function should produce the final result through that call. Its not happening. My count results in 0 and I am not understanding why. If I replace my query with a static array like [44,55,99,33] then it will pass the values ok. Likewise if I keep the query and simply replace the $id in the query and make it a static id such as '20' then it works. I would think that the id was the issue then and it wasnt pulling properly but it seems to work ok just not pass? function idx(){     global $wpdb, $id;       $getId = $_SERVER['REQUEST_URI'];     $ecp = explode('/', $getId);     if($ecp[3] != ''){         $id = $ecp[3];     }         return $id; } add_action( 'after_setup_theme', 'idx' );  =============================================== function Total_Result(){     global $wpdb;     $id = idx();        /*$resultx = [44,88,59,52];*/ ;      $resultx = $wpdb-&gt;get_results( $wpdb-&gt;prepare(&quot;SELECT * FROM {$wpdb-&gt;prefix}custom_form_submission_conversation as cc LEFT JOIN {$wpdb-&gt;prefix}custom_form_submission as cs on cc.fsid ='$id' WHERE fsid='$id'&quot; ));          $resultxs = array($resultx);          $total_result =  count($resultxs[0]);     echo  $total_result; }  when I var_dump $resultx I get: array(3) { [0]=&gt; object(stdClass)#1256 (36) { [“cid”]=&gt; string(3) “167” [“fsid”]=&gt; string(2) “20” [“specified_date”]=&gt; string(3) “yes” [“price_quote”]=&gt; string(4) “1140” [“posted_by”]=&gt; string(9) “dc_vendor” [“limit_count”]=&gt; string(1) “1” [“read_unread”]=&gt; string(1) “1” [“vendor_response”]=&gt; string(4) “zero” [“date_created”]=&gt; string(19) “2021-04-15 11:39:08” }   [1]=&gt; object(stdClass)#1257 (36) { [“cid”]=&gt; string(3) “186” [“fsid”]=&gt; string(2) “20” [“specified_date”]=&gt; string(3) “Yes” [“price_quote”]=&gt; string(3) “602” [“posted_by”]=&gt; string(8) “customer” [“limit_count”]=&gt; string(1) “1” [“read_unread”]=&gt; string(1) “1” [“vendor_response”]=&gt; string(4) “zero” [“date_created”]=&gt; string(19) “2021-04-15 11:39:08” }   [2]=&gt; object(stdClass)#1258 (36) { [“cid”]=&gt; string(3) “188” [“fsid”]=&gt; string(2) “20” [“specified_date”]=&gt; string(3) “yes” [“price_quote”]=&gt; string(4) “1017” [“posted_by”]=&gt; string(9) “dc_vendor” [“limit_count”]=&gt; string(1) “1” [“read_unread”]=&gt; string(1) “0” [“vendor_response”]=&gt; string(4) “zero” [“date_created”]=&gt; string(19) “2021-04-15 11:39:08” } }   so then I try and pass that data like so: function getvendorresponsestatus() {     global $wpdb; $id = idx();          $total_resultx = Total_Result($id);         die; }  Ive tried with and without the die();. The AJAX call is: setInterval(function(){     var ffiidd = jQuery('#ffiidd').val();     var ajaxurl = &quot;&lt;?php echo admin_url('admin-ajax.php'); ?&gt;&quot;;          jQuery.post(ajaxurl, {         action: &quot;vendorAjaxprog&quot;,         ffiidd: ffiidd     }, function(data) {         console.log(data);         jQuery.post(ajaxurl, {             action: &quot;getvendorresponsestatus&quot;, //&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt; this is the action that calls the function             fsid : ffiidd         },         function(datas) {             console.log('+ datas);             jQuery('.cust_vendor_top').html(datas);         });         if(data == 0){}else{             jQuery('.ajaxreload').html(data);                                     }     });               }, 5000);/*==30 seconds==*/  So the question is why wont it pass along the query array information but it passes a basic array or it will pass if I change the id in the query to be static? I know the query is good because of when I var_dumped it, I have results before I get to the Total_Result() function.