Why this partial specialization in C++ gives compiler error "invalid use of incomplete type"?
"invalid use of incomplete type" error with partial template specialization
In the same way as you can currently render the active viewport in Open GL? Some aspects of the Workbench renderer look as if they will be very useful for NPR people. Does a shortcode with a single attribute have to use an array? I want to build a shortcode that takes a single attribute.  Everything online is telling me to make it using an array:  // Add Shortcode function bg_comparison_points_shortcode( $atts ) {     // Attributes     $atts = shortcode_atts(         array(             'custom_field' =&gt; '',         ),         $atts,         'comparison_points'     );     return bg_calculate_points($custom_field); } add_shortcode( 'comparison_points', 'bg_comparison_points_shortcode' );   But in my mind something like this would be much simpler  // Add Shortcode function bg_comparison_points_shortcode( $custom_field ) {     return bg_calculate_points($custom_field); } add_shortcode( 'comparison_points', 'bg_comparison_points_shortcode' );   Is there a problem doing this simpler version? How do I mirror the faces of a cube (edit all of them when I edit one)? What's the relationship between initial eigenvalues and sums of squared loadings in factor analysis? On the one hand I read in a comment  that:     You can't speak of "eigenvalues" after rotation, even orthogonal   rotation. Perhaps you mean sum of squared loadings for a principal   component, after rotation. When rotation is oblique, this sum of   squares tells nothing about the amount of variance explained, because   components aren't orthogonal anymore. So, you shouldn't report any   percentage of variance explained.   On the other hand, I sometimes read in books people saying things like:     The eigenvalues associated with each factor represent the variance   explained by that particular factor; SPSS also displays the eigenvalue   in terms of the percentage of variance explained (so factor 1 explains   31.696% of total variance). The first few factors explain relatively large amounts of variance (especially factor 1), whereas subsequent   factors explain only small amounts of variance. SPSS then extracts all   factors with eigenvalues greater than 1, which leaves us with four   factors. The eigenvalues associated with these factors are again   displayed (and the percentage of variance explained) in the columns   labelled Extraction Sums of Squared Loadings.   That text is from Field (2013) Discovering statistics using IBM SPSS, and this diagram accompanies it.    I'm wondering     Who is correct about whether it's possible to speak of eigenvalues after rotation? Would it matter if it was an oblique or orthogonal rotation?   Why are the "initial eigenvalues" different from the "extraction sums of squared loadings"? Which is a better measure of total variation explained by the factors (or principal components or whatever method is used)? Should I say that the first four factors explain 50.317% of variation, or 40.477%? How to add item to right-click menu when NOT selecting a folder or file? How do I add a menu item to my context menu to open up powershell (or any other arbitary application) when I right-click inside Windows Explorer?  I found tons of links on how to add menu items when doing this: (selecting a folder; )    ...but couldn't find any instructions on how to add menu items when doing this: (not selecting a folder or file)    I did find  and tried adding powershell to HKEY_CLASSES_ROOT\Directory\Background\shell\, (loosely based on the  and linked above) but it didn't work for me.  I'm running Windows 7, by the way.  Also, I'm currently interested in adding only PowerShell, but I'd prefer a general solution I can apply to add any program to the context menu. What to do if a referee plagiarises the result after rejecting a paper? Delete own query on data explorer Minimal polynomial of $\sqrt{2}+\sqrt{3}$ over $\mathbb Q$ I had an example in the book given as follows:        Find the minimal polynomial of $\sqrt{2}+\sqrt{3}$ over $\mathbb Q$ .       Solution:  $~~~~~$$(\sqrt{2}+\sqrt{3})^2=5+2 \sqrt6$      $(\sqrt{2}+\sqrt{3})^4=49+20 \sqrt6$       Then $(\sqrt{2}+\sqrt{3})^4-10(\sqrt{2}+\sqrt{3})^2+1=0.$       Thus $a=\sqrt{2}+\sqrt{3}$ satisfies $f(x)=x^4-10x^2+1$ over $\mathbb Q$.       Let $p(x)$ be the minimal polynomial of $\sqrt{2}+\sqrt{3}$ over $\mathbb Q$.Then $(\sqrt{2}-\sqrt{3}),(-\sqrt{2}+\sqrt{3}),(-\sqrt{2}-\sqrt{3})$ are also roots of $p(x).$   So degree of $p(x)$ is atleast $4$.      But $f(a)=0 $ and $f(x) \in \mathbb Q[x] \implies p(x)$ divides $f(x)$ .      So $f(x)$ is minimal polynomial of $\sqrt{2}+\sqrt{3}.$   But I can't get the step  how are $(\sqrt{2}-\sqrt{3}),(-\sqrt{2}+\sqrt{3}),(-\sqrt{2}-\sqrt{3})$ also roots of $p(x).$   Kindly help with this. I'd like to see if somebody has been trying to log-in by brute-force into my Ubuntu 12.04 server over SSH. How can I see if such activities have been taking place? Problems with Groups in Traminer I'm having a problem using the group function in TraMineR. I have a data set that contains SPELL data, so multiple rows per case. I also have demographic data per case, at one row per case. I merge these together and end up with data that has a demographic covariate per row, so multiple rows per case. An example of this data would be:  id startmin stopmin activity educ4 4      1      20       work    HS 4      20     40       play    HS 8      1      15       sleep   College 8      15     40       work    College   I can make sequence data from this, but when I try to run a plot using the group command        seqiplot(atus.seq, group = atus.seqdata$educ4, border=NA,                 withlegend="right",  cex.plot=.55)   it tells me:       &gt;"Error: group must contain one value for each row in the sequence object".   I have gotten this to work with the example of the mvad data in the training manual, but I can't seem to get it to work with the groups, whether I link to the original demographic data, the merged data, or try to pass the covariates by seqformat and seqdef. Ideas? For $V$ vector space of dimension $n$ under $\mathbb C$ and $T: V \to V $ linear transformation , show $V= \ker T^n \oplus $ Im $T^n$ How to wait in a bash script for several subprocesses spawned from that script to finish and return exit code !=0 when any of the subprocesses ends with code !=0 ?  Simple script:  #!/bin/bash for i in `seq 0 9`; do   doCalculations $i &amp; done wait   The above script will wait for all 10 spawned subprocesses, but it will always give exit status 0 (see help wait). How can I modify this script so it will discover exit statuses of spawned subprocesses and return exit code 1 when any of subprocesses ends with code !=0?  Is there any better solution for that than collecting PIDs of the subprocesses, wait for them in order and sum exit statuses? $\mathbb{Q}^{\times}$ is the group of rational number without $0$ under multiplication, and $\mathbb{Z}^{n}$ is the free abelian group of rank $n$. Show that $\mathbb{Q}^{\times}$ not isomorphic to $\mathbb{Z}^{n}$. I tried to assume that there is an isomorphism and to get a contradiction.. didn't succeed In Russian we have idiom/saying "To shoot out of cannon into sparrows" (literal translation) which is used to convey an idea of applying too drastic measures to small problems. I believe there should be some native-English equivalents to this saying. Can you share if there are any? I'm working on a 2nd order passive low pass filter, consisting of two passive low pass filters chained together.         &ndash; Schematic created using   Let \$ H(s) = H_1(s)H_2(s) \$ where \$ H_1(s) \$ and \$ H_2(s) \$ are the transfer functions for each separate filter stage.  Then \$ |H(s)| = |H_1(s)||H_2(s)| \$  Knowing the magnitude of a passive low pass filter,   $$|H(s)| = \dfrac1{\sqrt{ (\omega R_1C_1)^2 + 1} } \times \dfrac1{\sqrt{ (\omega R_2C_2)^2 + 1} } = \dfrac1{\sqrt{((\omega R_1C_1)^2 + 1)((\omega R_2C_2)^2 + 1)}} $$  Then trying to find the cutoff frequency:  $$ \left(\dfrac1{\sqrt{2}}\right)^2  = \dfrac1{\sqrt{((\omega R_1C_1)^2 + 1)((\omega R_2C_2)^2 + 1)}} $$ $$ 2  = \sqrt{((\omega R_1C_1)^2 + 1)((\omega R_2C_2)^2 + 1)} $$ $$ 4  = ((\omega R_1C_1)^2 + 1)((\omega R_2C_2)^2 + 1) $$ $$ 4  = (\omega R_1C_1)^2(\omega R_2C_2)^2 + (\omega R_1C_1)^2 + (\omega R_2C_2)^2 + 1 $$  And I'm stuck. Research on the web tells me \$ \omega_c = \dfrac1{\sqrt{R_1C_1R_2C_2}} \$, but I can't find why? Can anybody show my the derivation to find this? I'm working on a large c++ system that is has been in development for a few years now. As part of an effort to improve the quality of the existing code we engaged on a large long-term refactoring project.  Do you know a good tool that can help me write unit tests in C++? Maybe something similar to Junit or Nunit?  Can anyone give some good advice on the methodology of writing unit tests for modules that were written without unit testing in mind? How can I use 3rd party libraries on QGIS plugins on Windows?   I've developed a plugin that uses rasterio and numpy for a customer, but he's having problems installing rasterio and numpy.  Actually rasterio and numpy were installed in it's main system Python (C:\Python27), but I need QGIS Python to recognize it. Why doesn't the Related question list show that questions are closed? Programmatically obtaining Big-O efficiency of code I wonder whether there is any automatic way of determining (at least roughly) the Big-O time complexity of a given function?  If I graphed an O(n) function vs. an O(n lg n) function I think I would be able to visually ascertain which is which; I'm thinking there must be some heuristic solution which enables this to be done automatically.  Any ideas?  Edit: I am happy to find a semi-automated solution, just wondering whether there is some way of avoiding doing a fully manual analysis. Printing pointers in C