C# operator '==' cannot be applied to operands of type 'TKey' and 'TKey' in generic classes
Can't operator == be applied to generic types in C#?
How compatible are my old Nikon lenses? I'm looking at buying a new SLR body. I have an old film Nikon entry-level SLR (about ten years old) with a kit lens. If I buy a Nikon body, how likely is it that my old lens will work on it? Would I be better off buying a new lens? I saw there are various manga with Akame ga KILL! in their names.  The ones I have found are:       Which one should I read if I want to continue the storyline of the anime? Vandermonde Determinant This is an exercise from Ian Stewart's Galois Theory, $3^{rd}$ edition:     If $z_1,z_2,\ldots,z_n$ are distinct complex numbers, show that the determinant $$D=\left|\begin{array}[cccc]  11&amp;1&amp;\cdots&amp;1\\ z_1&amp;z_2&amp;\cdots&amp;z_n\\ z_1^2&amp;z_2^2&amp;\cdots&amp;z_n^2\\ \vdots&amp;\vdots&amp;\ddots&amp;\vdots\\ z_1^{n-1}&amp;z_2^{n-1}&amp;\cdots&amp;z_n^{n-1} \end{array}\right|$$   is nonzero.       Hint: Consider the $z_j$ as independent indeterminates over $\Bbb C$. Then $D$ is a polynomial in the $z_j$, of total degree $0+1+\cdots+(n-1)=\frac{1}{2}n(n-1)$. Moreover, $D$ vanishes whenever $z_j=z_k$ for $k\neq j$, as it then has two identical rows. Therefore $D$ is divisible by $z_j-z_k$ for all $j\neq k$, hence it is divisible by $\prod_{j&lt;k}(z_j-z_k)$. Now compare degrees.   My question is how to do this. I follow the hint and I'm thinking of $D$ as a cofactor expansion; is that the idea? Also, the fact that $D$ vanishes whenever $z_j=z_k$ for $k\neq j$ follows since it would have two identical columns, right? I don't see why $z_j=z_k$ would imply it has two identical rows, as the hint suggests. The fact that it is divisible by $(z_j-z_k)$ is easy since that would make $z_k$ a root for $k=j$, but I'm not quite sure I follow why the degrees would be different. I think the degree of the product would be $1+2+\cdots+(k-1)$, but then add these up for all $k&lt;n$?   I appreciate any clarification that you can provide! During the beta of Windows 10 it was hard know what version you were running unless it had it posted to the desktop. Once that wasn't there - how do you tell what version / build you are running?   This will become more of an issue as Microsoft starts releasing more builds with the new update mechanism. O-Rings vs. Washers for Garden Hoses? Why do I get "unresolved external symbol" errors when using templates? When I write C++ code for a class using templates and split the code between a source (CPP) file and a header (H) file, I get a whole lot of "unresolved external symbol" errors when it comes to linking the final executible, despite the object file being correctly built and included in the linking.  What's happening here, and how can I fix it? For example, on this page:   I see the following:   What does this 499 mean? I can't seem to correlate it with upvotes, posts, edits or anything else. I have been given a Bode plot of a low pass filter, and tasked with essentially reversing the effects by using a high pass filter. I have solved for the transfer function which is the first equation, and I am assuming the inverse transfer function will give me the information I need to construct the high pass filter. I know the values for \$z\$ and \$p\$. Is there a method given any transfer function to realise the circuit elements required? $$H(s) = 0.17\frac{s-z}{s-p}$$ $$H(s)^{-1} = 5.88\frac{s-p}{s-z}$$ Beamer: how to justify the whole text? How can I justify the text in the whole document in beamer without using \usepackage{ragged2e} and \justifying at the beginning of each frame?  \documentclass[8pt,handout,t]{beamer} \usepackage{pifont} %used inside itemize environment \item[\ding{226}] \usepackage{lipsum} \begin{document}  \begin{frame} \begin{columns}[T]  \begin{column}{0.3\textwidth} \includegraphics[width=\columnwidth]{example-image-1x1} \end{column} \begin{column}{0.65\textwidth} \begin{itemize} \item[\ding{226}] \lipsum[2] \item[\ding{226}] \lipsum[3] \end{itemize} \end{column}  \end{columns} \end{frame}  \begin{frame}  \lipsum[3]  \begin{itemize}    \item[\ding{226}] \lipsum[4]  \end{itemize} \end{frame} \begin{frame}   \begin{columns}[t] \begin{column}{0.4\textwidth} \lipsum[3] \end{column} \begin{column}{0.4\textwidth} \lipsum[5] \end{column} \end{columns} \end{frame} \end{document}     Edit: I had already checked  out but it does not work for both the columns and the itemize environment. Incubated but not hatched egg I got the message "oh" and it showed my egg. Before I could do anything the server went down. When I got back on my egg was gone. Is there anything I can do to retrieve my incubated but not hatched egg? How do I deal with a runaway bride? I killed my first wife once I found out there is a mercenary you can marry who gives you up to 300 gold a day (in Whiterun). The only requirement, of course, being that I had to hire her first. So I hired her, and then I popped the question, to which she replied the usual: tell the priest to arrange the wedding.   When we reached Riften I told her to wait, just outside the bee and barb, and arranged the wedding. I went through the process, and the second it finished she left, I followed but as I left she was nowhere to be seen. I have tried going back to my house, the pub where I hired her and that same spot in Riften about 6 times each now, some during the day, some during the night and cannot find her at all.   Now this isn't to much of a problem because I can re-marry...oh wait, to remarry, my spouse has to die, so I can't claim gold off her and can't remarry, and the autosaves have been used up fast travelling to the places I thought she might've been. My last save is something like 6 levels ago, and I don't want to have to load it.   What should I do about this situation? Removing intercept from GLM for multiple factorial predictors only works for first factor in model I am running a binomial logistic regression with a logit link function in R. My response is factorial [0/1] and I have two multilevel factorial predictors - let's call them $a$ and $b$ where $a$ has 4 factor levels  $(a_1,a_2,a_3,a_4)$ and $b$ has 9 factor levels $(b_1,b_2,\dotsc,b_9)$. Therefore:  mod &lt;- glm(y ~ a + b, family = binomial(logit), data=pretend) summary(mod)   The model output would then show all the information about the model as well as the coefficients.  There is a factor level for both a and b missing (a1 and b1) from the summary output. I understand that it is constrained in the "intercept" of the model. I have read that if I want to remove the intercept term and see the estimates for those factor levels I can just add -1 to the model formula, i.e.:  mod2 &lt;- glm(y ~ a + b - 1, family=binomial(logit), data=pretend) summary(mod2)   In the new model (mod2) the intercept term is then gone and variable a's factor-level a1 is given amongst the list of coefficients. But, variable b's factor-level b1 is still missing and given that there is no intercept term anymore, how can I interpret the odds-ratio for that factor level then?  Could someone please explain to me how to get the coefficient for b1 too and why this is happening? Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start.  All the questions linked below, as well as others which deal with more specialized books, can be found under the tag  (formerly ).  If you have a question to add, please edit it in. However, make sure of a few things first:   The question should be tagged  It should be of the form "What are good books to learn/study [subject] at [level]?" It shouldn't duplicate a topic and level that's already on the list   Related Meta: I'm new to TDD and xUnit so I want to test my method that looks something like:   List&lt;T&gt; DeleteElements&lt;T&gt;(this List&lt;T&gt; a, List&lt;T&gt; b);   Is there any Assert method that I can use ? I think something like this would be nice  List&lt;int&gt; values = new List&lt;int&gt;() { 1, 2, 3 }; List&lt;int&gt; expected = new List&lt;int&gt;() { 1 }; List&lt;int&gt; actual = values.DeleteElements(new List&lt;int&gt;() { 2, 3 });  Assert.Exact(expected, actual);   Is there something like this ? How can I use Unicode-aware regular expressions in JavaScript?  For example, there should be something akin to \w that can match any code-point in Letters or Marks category (not just the ASCII ones), and hopefully have filters like [[P*]] for punctuation, etc. At the moment the most frustrating part of my brewday is getting the cold wort into the fermenter. Here is my process. I have a 20 litre saucepan that i use as a kettle that does not have a tap. At flame out I add my immerseion chiller that is plumbed into my kitchen sink tap. When I have reached temperature I remove the chiller and whirlpool and leave it to rest to 30 minutes. I am use a siphon to rack directly into the plastic bucket fermenter.  The problem is that the siphon always gets clogged with the hops after i have only transfered about 20% of the wort. I have also tried carefully pouring the wort through a seive, but this sort of depfeats the point of the whirlpool and also the seive got blocked with hops as well. All in all i end up wasting a lot of the wort because i am afraid of getting a lot trub in the fermenter.  What are the best processes to use with my current equpment to get the wort into the fermenter? Embedding ordinals in $\mathbb{Q}$ Is having a skills bar chart on a resume a good idea? How do real and effective user IDs work? When a normal user wants to make change to the passwd file, the user will by setuid be given the effective user access. User becomes root temporarily and can edit passwd.  However you can only edit your password right, and not everybody else? However your effective user access is root. So how come you're not allowed to change other passwords beside yours?  When you run a program with setuid, what does it mean actually when effective user is root, but real user id is still your name? Python: List vs Dict for look up table I have about 10million values that I need to put in some type of look up table, so I was wondering which would be more efficient a list or dict?  I know you can do something like this for both:  if something in dict_of_stuff:     pass   and  if something in list_of_stuff:     pass   My thought is the dict will be faster and more efficient.  Thanks for your help.  EDIT 1  Little more info on what I'm trying to do.  .  I'm making a look up table to see if a value calculated has all ready been calculated.   EDIT 2  Efficiency for look up.  EDIT 3  There are no values assosiated with the value...so would a set be better?