I have a very simple template class.  #pragma once #include &lt;iostream&gt;  template &lt;class T&gt; class Test { protected:     class Node     {     public:         Node(Node&amp; node) {}     protected:         virtual Node* copyNode(Node&amp;);     private:     }; };  template &lt;class T&gt; Test&lt;T&gt;::Node* Test&lt;T&gt;::copyNode(Test&lt;T&gt;::Node&amp; node) {     return new Test&lt;T&gt;::Node(node); }   I use it in the main program as follows.  #include "Test.h" using namespace std;  int main() {     Test&lt;int&gt; tree;     getchar(); }   I get a syntax error C2061: "identifier 'Node'".  Both the declaration and the implementation are in the same header file (the linker has problems with template classes). I am using Visual Studio 2015.  What is the proper way of implementing the copyNode method without writing it inline?
In templates, where and why do I have to put typename and template on dependent names? What exactly are dependent names anyway?    I have the following code:  template &lt;typename T, typename Tail&gt; // Tail will be a UnionNode too. struct UnionNode : public Tail {     // ...     template&lt;typename U&gt; struct inUnion {         // Q: where to add typename/template here?         typedef Tail::inUnion&lt;U&gt; dummy;      };     template&lt; &gt; struct inUnion&lt;T&gt; {     }; }; template &lt;typename T&gt; // For the last node Tn. struct UnionNode&lt;T, void&gt; {     // ...     template&lt;typename U&gt; struct inUnion {         char fail[ -2 + (sizeof(U)%2) ]; // Cannot be instantiated for any U     };     template&lt; &gt; struct inUnion&lt;T&gt; {     }; };   The problem I have is in the typedef Tail::inUnion&lt;U&gt; dummy line. I'm fairly certain that inUnion is a dependent name, and VC++ is quite right in choking on it. I also know that I should be able to add template somewhere to tell the compiler that inUnion is a template-id. But where exactly? And should it then assume that inUnion is a class template, i.e. inUnion&lt;U&gt; names a type and not a function?
Can't find wifi drivers for 0bda:f179 Realtek Semiconductor Corp Why is the network configuration I set in /etc/network/interfaces ignored on Ubuntu 17.10? Recently, I read in the journal  that Stephen Hawking wrote a paper claiming that black holes do not exist.  How is this possible? Please explain it to me because I didn't understand what he said.  References:   Article in Nature News:  (Zeeya Merali, January 24, 2014). S. Hawking, Information Preservation and Weather Forecasting for Black Holes, . Intutitive meaning behind the formal definition of sufficient statistic? According to the definition of sufficiency, a statistic is sufficient for a parameter if the conditional distribution of $X$ given a value of statistic does not depend upon the parameter.   What I am trying to understand is how does conditional distribution of $X$ not being a function of the parameter fit into the intuitive meaning of sufficiency i.e statistic value holding the same amount of information as that of the respective sample. I can't run Cisco packet tracer 7.1 on Ubuntu I have downloaded and extracted the packet tracer file, then I used this command as root  chmod +x install   then I ran (as root)  ./install    Then I used this command   ./set_ptenv.sh   but whenever I run this command   packettracer    it just doesn't start What exactly is a distribution? I know very little of Probability and Statistics, and am wishing to learn.  I see the word "distribution" used all over the place in different contexts.  For example, a discrete random variable has a "probability distribution."  I know what this is. A continuous random variable has a probability density function, then for $x\in\mathbb{R}$, the integral from $-\infty$ to $x$ of the probability density function is the cumulative distribution function evaluated at $x$.   And apparently just "distribution function" is synonymous with "cumulative distribution function," at least when talking about continuous random variables (question: are they always synonyms?).  Then there are many famous distributions.  $\Gamma$ distribution $\chi^2$ distribution, etc.  But what exactly is a $\Gamma$ distribution?  Is it the cumulative distribution function of a $\Gamma$ random variable?  Or the probability density function of a $\Gamma$ random variable?  But then a frequency distribution of a finite data set appears to be a histogram.  Long story short: in Probability and Statistics, what is the definition of the word "distribution"?    I know the definition of distribution in Mathematics (an element of the dual space of the collection of test functions equipped with the inductive limit topology), but not Probability and Statistics. launch a VM on Ubuntu On Ubuntu 14.04, I installed VirtualBox on which I have created 2 Ubuntu virtual machines.  Does Ubuntu provide a way to launch  the virtual machine I want at a particual moment ? Is there any solution for this problem by developing a .sh script for example or using any other programming language ? I normally use the following idiom to check if a String can be converted to an integer.  public boolean isInteger( String input ) {     try {         Integer.parseInt( input );         return true;     }     catch( Exception e ) {         return false;     } }   Is it just me, or does this seem a bit hackish?  What's a better way?    See my answer (with benchmarks, based on the  by ) to see why I've reversed my position and accepted  to this problem.  I think this original code will be used by most people because it's quicker to implement, and more maintainable, but it's orders of magnitude slower when non-integer data is provided. This is Exercise 26 from Chapter V Algebraic Extensions in Lang's Algebra.  $F$ is finite normal extension over $k$ and $f(x)$ is irreducible in $k[x]$. If $f(x)=g(x)h(x)k(x) \in F[x]$ where $g(x),h(x)$ are monic irreducible factors in $F[x]$, I need to show that there exists an automorphism of $F$ which takes $g(x)$ to $h(x)$.  Any hints would be appreciated.  Sending one root to another is okay but how to do that for a collection of roots? Is there a difference between single and double quotes in Java? To find all $n$ such that $(n-1)!+1$ is a perfect power of $n$ I'm programming a presentation in LaTeX using the beamer class.  However, it defaults to 4:3 aspect ratio slides, while everything I use is 16:9. Is there an easy way to change this using a command or two? Due to my ignorance, I find that most of the references for mathematical analysis (real analysis or advanced calculus) I have read do not talk much about the "multivariate calculus". After dealing with the single variable calculus theoretically, it usually directly goes to the topic of measure theory.    After reading the wiki article "", I'd like to find the rigorous proof for this test. The first book comes to my mind is Courant's Introduction to Calculus and Analysis which includes the multivariate case in the second volume.   Motivated by this, I'd like to put the question here:     What are the usual references for the   theoretical treatment for   ? I'm out of close votes. Can I use moderator flags instead? Problems with \input{table.tex}\hline after 2020 fall LaTeX release Since updating to the 2020 Fall release (MikTeX on Windows but also tested with TeXLive), I can no longer compile files where tables are imported from an external file using \input and followed by \hline (or \bottomrule). Things work perfectly with older releases. Note that it works if the last \\ is outside the file to be imported, but this is not a feasible option if the tables are created automatically from other softwares. Here is a MWE:  \begin{document}  \begin{table}   \caption{Table in text}   \begin{tabular}{lcc}     a &amp; 1 &amp; 2\\     b &amp; 1 &amp; 2\\     \hline   \end{tabular} \end{table}  \begin{table}   \caption{Table in other file 1}   \begin{tabular}{lcc}     \input{table1}     \hline   \end{tabular} \end{table}  \begin{table}   \caption{Table in other file 2}   \begin{tabular}{lcc}     \input{table2}\\     \hline   \end{tabular} \end{table}  \end{document}  with external files: table1.tex:     a &amp; 1 &amp; 2\\     b &amp; 1 &amp; 2\\  table2.tex:     a &amp; 1 &amp; 2\\     b &amp; 1 &amp; 2  Here is the log when it fails: This is pdfTeX, Version 3.14159265-2.6-1.40.21 (MiKTeX 20.10) entering extended mode (MWE.tex LaTeX2e &lt;2020-10-01&gt; patch level 1 L3 programming layer &lt;2020-10-05&gt; xparse &lt;2020-03-03&gt; (&quot;C:\Program Files\MiKTeX\tex/latex/base\article.cls&quot; Document Class: article 2020/04/10 v1.4m Standard LaTeX document class (&quot;C:\Program Files\MiKTeX\tex/latex/base\size10.clo&quot;)) (&quot;C:\Program Files\MiKTeX\tex/latex/l3backend\l3backend-pdftex.def&quot;) (MWE.aux) (table1.tex) ! Misplaced \noalign. \hline -&gt;\noalign                    {\ifnum 0=`}\fi \hrule \@height \arrayrulewidth \futurelet... l.18     \hline                 ! You can't use `\hrule' here except with leaders. \hline -&gt;\noalign {\ifnum 0=`}\fi \hrule                                           \@height \arrayrulewidth \futurelet... l.18     \hline                 ! Missing number, treated as zero. &lt;to be read again&gt;                     \futurelet  l.18     \hline                 ! Illegal unit of measure (pt inserted). &lt;to be read again&gt;                     \futurelet  l.18     \hline                 (table2.tex) [1{C:/Users/Gouel/AppData/Local/MiKTeX/pdftex/config/pdftex.map}] (MWE.aux) ) (see the transcript file for additional information)&lt;C:/Program Files/MiKTeX/fo nts/type1/public/amsfonts/cm/cmr10.pfb&gt; Output written on MWE.pdf (1 page, 14750 bytes). Transcript written on MWE.log.  With an older release under Linux, it works perfectly: This is pdfTeX, Version 3.14159265-2.6-1.40.20 (TeX Live 2019/Debian) (preloaded format=pdflatex)  restricted \write18 enabled. entering extended mode (./MWE.tex LaTeX2e &lt;2020-02-02&gt; patch level 2 L3 programming layer &lt;2020-02-14&gt; (/usr/share/texlive/texmf-dist/tex/latex/base/article.cls Document Class: article 2019/12/20 v1.4l Standard LaTeX document class (/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo)) (/usr/share/texlive/texmf-dist/tex/latex/l3backend/l3backend-pdfmode.def) (./MWE.aux) (./table1.tex) (./table2.tex) [1{/var/lib/texmf/fonts/map/pdftex/up dmap/pdftex.map}] (./MWE.aux) )&lt;/usr/share/texlive/texmf-dist/fonts/type1/publi c/amsfonts/cm/cmr10.pfb&gt; Output written on MWE.pdf (1 page, 13788 bytes). Transcript written on MWE.log. What is exactly the density of a black hole and how can it be calculated? Does text in brackets invoke the "an" vs. "a" rule? Plot construction for a velocity vs position graph. Interpolation for phase-diagram construction? I continue to find it amazing that something as “bulky” and macroscopic as a static magnetic or electric field is actually a manifestation of virtual photons.  So putting on your QFT spectacles, look closely at the space near the pole of a powerful magnet – virtual photons! Now look between the plates of a charged capacitor – virtual photons again!   But if it’s all virtual photons, how do we get the difference between a magnetic and electric field?  [This question needs the tag "magnetostatics" as well]. I have a group of objects of the same colour, consisting of compound paths, regular paths and groups of these. How to change the colour of all objects at once? When I tried to use colour picker or change it through color palette the colour remained the same but the graphics was rendered with a very tiny outline of the new colour, which I guess is not printable. Usually I had to change the colour of all objects individually.  Edit: I'm sorry if I was not too precise. I mean to apply new colour / swatch to all member objects of the group at once, not to change properties of a commonly shared swatch.    Edit 2: I received very useful answers, however my goal was to pick a colour from another object, serving as a source. When I tried to select all objects, for example with ctrl-a, and then use a eyedropper to pick up a desired colour, it didn't work for some objects in some groups. Please have a look at my answer where several methods are listed.