Different Python Variables with Same Value Pointing to Same Object
"is" operator behaves unexpectedly with integers
How can I (algorithmically) count the number of ways n m-sided dice can add up to a given number? Proof that $S_3$ isomorphic to $D_3$ How do I identify which features have NULL attributes in the attribute table of a shapefile?  When i try [field]= 'NULL' it selects the features with value = 0 (see picture) Is there a difference between foo(void) and foo() in C++ or C? Consider these two function definitions:  void foo() { }  void foo(void) { }   Is there any difference between these two? If not, why is the void argument there? Aesthetic reasons? Strip whitespace from jsp output What's optimal hardness for a kitchen knife blade? Many knife manufacturers provide the hardness value for the knife blade in the specifications - like 53HRC or 57 HRC.  What's the optimal hardness for kitchen knives? Do I always prefer the ones with higher hardness all else being equal? $f_n:[0,1]\to [0,1]$ continuous, $f_n\to f$ uniformly, prove: ${\frac1n}\sum_{k=1}^{n}{f_k} \to f$ uniformly I was able to prove, hopefully correctly, that the sum converges uniformly. But, I'm not sure how to show it converges uniformly specifically to $f$.  The way I proved it converges uniformly was by using the Dirichlet convergence test, by taking $a_k(x) = \frac1n$ and $b_k(x) = f_k(x)$. $\sum_{k=1}^n{b_k(x)}$ is uniformly bounded on $[0,1]$ by $n+2$ for instance, and $a_n$ is monotone and uniformly convergent to 0 because it does not depend on the value of $x$.  I got rather stuck after this. I guess I have to use the continuity of the functions and the uniform convergence of both, but I can't figure out how to show that they converge to the same thing. Any help will be greatly appreciated. why does OSX add extra '._' when I tar a directory? I'd just like to know why if I "tar -czf" a file/directory, osx adds a:  ._  for each file? I see these when I untar in linux. Or when I work with the uncompressed project in eclipse as it doesn't like them at all. I use 10.7.5. Difference between "I'm home" vs "I'm at home" What's the difference between these two sentences? And which one's grammatically correct? I've noticed that in comments, when you create `code region` with backticks, the backslash will still work as an escape character within that region (but it should not, IMHO).  To clarify:   In comments, `\\` will be rendered as \, but it should be rendered as \\ In the post body itself, `\\` will be rendered as \\ (i.e., correctly)   This is especially confusing when you enter regular expressions into a comment, since backslash-escaping is very common there, and confusion increases if you are dealing with a regex that is double-escaped for representation in a string.   At some point you lose track how many backslashes you must make so the comment renders correctly, or you don't notice fast enough (or at all) and the comment contains wrong code where the same markup in a question or answer would come out as perfectly correct.   It's just that comments can't be corrected anymore after the grace period, leaving you with the choice of either deleting the comment, thus crippling the conversation, or engaging in a trial-and-error game of writing another comment with even more backslashes to explain the issue.  My question is two-fold:   Will this error be corrected? If yes, existing comments should probably be searched and "fixed" by a routine that tries to do the right thing (this is probably somewhere between hard and impossible) Or, can I rest assured that never ever the behavior of the backslash in comments is going to be changed, so I can start working around this issue by hand, knowing that they won't start displaying incorrectly at some point in the future? Attempting to compile kernel yields a certification error I'm currently attempting to follow  guide in order to install the 4.5.7 kernel with Grsecurity on my Kali Linux desktop.   I am following that list of instructions verbatim, except for the fact that I'm trying to use Grsecurity's test patch for the 4.5.7 kernel and I'm running Kali Linux instead of straight Debian.  Every time I attempt to compile the kernel, however, I get this error following the line "CC certs/system_keyring.o":    CC      certs/system_keyring.o make[2]: *** No rule to make target 'debian/certs/benh@debian.org.cert.pem', needed by 'certs/x509_certificate_list'.  Stop. Makefile:951: recipe for target 'certs' failed make[1]: *** [certs] Error 2 make[1]: Leaving directory '/home/jc/Downloads/linux-4.5.7' debian/ruleset/targets/common.mk:295: recipe for target 'debian/stamp/build/kernel' failed make: *** [debian/stamp/build/kernel] Error 2   I get this error, as I found out, for any kernel even if I apply no patches or modifications, so it has something to do with the tools I'm using to compile the kernel (apparently a system keychain of some sort). Can someone out there tell me how to fix my OS and compile my kernel?   P.S. Here is the output of cat /proc/version:  Linux version 4.6.0-kali1-amd64 (devel@kali.org) (gcc version 5.4.0 20160609 (Debian 5.4.0-4) ) #1 SMP Debian 4.6.2-2kali2 (2016-06-28) How can I add an application to the GNOME window manager? The GNOME on-board documentation covers only the things anyone can easily guess. I have an application for that I can only start from the command line. Not that I mind using a terminal but ...  Anyway, how do I add the command (and preferably a nice logo) to GNOME WM? For instance, does the compiler know to translate  string s = "test " + "this " + "function";   to  string s = "test this function";   and thus avoid the performance hit with the string concatenation? Both DHCP and static IP addresses simultaneously on one interface We can use multiple IP addresses for a single interface in Linux (eg. eth0:0, eth0:1). But can we use DHCP and static IP at the same time? eth0:1 should have a static IP address and eth0:0 should be configured using DHCP.  How can we accomplish both? Vandermonde identity corollary $\sum_{v=0}^{n}\frac{(2n)!}{(v!)^2(n-v)!^2}={2n \choose n}^2$ I am trying to prove this identity:  $$\sum_{v=0}^{n}\frac{(2n)!}{(v!)^2(n-v)!^2}={2n \choose n}^2$$ I think this identity (corollary of Vandermonde identity): $${n\choose 0}^2+{n\choose 1}^2+{n\choose 2}^2+\cdots+{n\choose n}^2={2n \choose n}$$ is applicable for solving it. Please give me some hints. thank you Adobe Illustrator: Lines with stroke < 2.0pt doesn't change color I created lines using the line segment tool in Adobe Illustrator (latest Adobe Cloud version) and I can't change the color of the stroke (through the Appearance panel) if the stroke weight is less than 2.0pt.   If the stroke is 2pt or more, then the color around the line changes but not the line itself.    The whole behavior is odd for me as I've never faced in Illustrator before.  Edit: added screen below with the line selected. Formatting OGR VRT file to convert CSV to KML? How should I install HPLIP binary/proprietary plugin/driver for my HP printer or printer+scanner? Let's assume that one has some modern HP printer and/or scanner which is  supported by HPLIP package from official repository. Or supported by newer version of HPLIP package (see  about installation).  From official documentation () it is known that device needs proprietary/binary driver or plugin.  How should one install such plugin? Suppose $A$ is a $n \times n$ constant matrix. How can I prove $\det(e^A) = e^{\displaystyle \sum_{\lambda_i\in\sigma(A)} \lambda_i}$,  where $\sigma(A)$ is the multiset of eigenvalues of $A$?  The following matlab code shows this is true in $n = 3$ case:  A = rand(3) detA = exp(sum(eig(A))) detmA = det(expm(A)) How to migrate a WordPress installation from one site to another, including all images?