Program code :  int main()  {      int i;      for (i = 0; i &lt; 0, 5; i++)          printf("%d ", i);      return 0;  }    The loop above is executed infinite times.  What does i&lt;0,5 mean, and how it is evaluated?
How does the comma operator work in C++?  For instance, if I do:  a = b, c;     Does a end up equaling b or c?   (Yes, I know this is easy to test - just documenting on here for someone to find the answer quickly.)  Update:  This question has exposed a nuance when using the comma operator.  Just to document this:  a = b, c;    // a is set to the value of b!  a = (b, c);  // a is set to the value of c!   This question was actually inspired by a typo in code.  What was intended to be  a = b; c = d;   Turned into  a = b,    //  &lt;-  Note comma typo! c = d;
Suppose $s$ is a complex number with $\Re(s) \in (0,1]$ and $\{a_n\}$ is a complex sequence converging to $a \neq 0$. Must the Dirichlet series $$\sum_{n=1}^\infty\frac{a_n}{n^s}$$ diverge? Stack Exchange iOS app crashes on start Upon clicking on SE icon, blue (starting) screen appears and then I am back to home screen, SE app simply won't start. This kind of behaviour never happened before (on any other app). I tried to remove it from &quot;task manager&quot;, reinstalling and logging back in; neither did work. In Settings -&gt; Stack Exchange -&gt; Notices I found a log message:  FILE DOESN'T EXIST, WILL CREATE: users/dev/buildagent/work/{id}/pods/target support files/pods/pods-ack...plist   App Version: 1.4.0 Device: iPhone7,2 OS Version: Version 9.1 (Build 13B143)   TLDR: app starts when cellphone has no internet access. I just noticed when I am on 3G (cellular internet) it crashes ASAP, but when I am on wifi that has no internet (for LAN etc.) app starts normally but no new content, when I turn off WiFi and iPhone switches to cellular; app crashes. Note: I turn off WiFi using control center - so I never leave the app. Another thing, when I force iPhone to use EDGE (slowest possible internet) app starts, and crashes after 5 seconds or so. I assume when app downloads some data from server.  Known workaround (works for me too)  I found a workaround: turn on Airplane Mode, launch the app, then turn Airplane Mode off. – NobodyNada Set the size of pgf picture? I have a pgf picture which I insert with:  \input{m1.pgf}   But the image is too big. Instead of regenerating a smaller image, I'd rather take advantage of vector graphics, and have XeLaTeX scale it. How do I set the width of pgf picture (keeping its aspect ratio)?  MWE  tex:  \documentclass{article}  \usepackage{fontspec} % enagles loading of OpenType fonts \usepackage{polyglossia} % support for languages  % fonts: \defaultfontfeatures{Scale=MatchLowercase,Mapping=tex-text} % without this XeLaTeX won't turn "--" into dashes \setmainfont{DejaVu Sans} \setsansfont{DejaVu Sans} \setmonofont{DejaVu Sans Mono}  % pgf: \usepackage{pgf}  \begin{document}  \input{m1.pgf}  \end{document}   Sample pgf:  (it's too big to cite it here, and I can't make much smaller). Can you explain Parzen window (kernel) density estimation in layman's terms? Is there a way to solve this integral?  $$\int \frac{dx}{\sqrt{-ax^2 + bx +c}}, \;\;\;\;\; \forall\; a,b,c \in (0,+\infty) \;in\;R$$  I have tried it by changing of variable and by parts, but no result. I don't know what else to do.  Thanks in advance. Average distance between two random points in a square A square with side $a$ is given. What is the average distance between two uniformly-distributed random points inside the square?  For more general "rectangle" case, see . The proof found there is fairly complex, and I am looking for a simpler proof for this special case. I expect it could be significantly simpler.  See also . I had recently taken the hard drive out of my computer so that I could install a bigger one. But when I reconnected it to the computer, all the files on the E:\ partition and some of the files on the C:\ partition had strange names like TTv5yV5354$YVC5Wy on them. I did on one occasion move an electromagnet near the drive. Could that have caused this? Please help me, some of those files were valuable. Safest way to transport a laptop during flight I flew a long range flight carrying my laptop, a quite heavy one, inside a neoprene briefcase in the passenger cabin. The recommendation by the aircrew was to place it in the overhead compartment or under the seat in front of me. However, during take-off and landing, the vibrations on the plane are quite strong and, as a result, it received minor damage.   Placing them in the overhead compartment might be equivalent to placing it on the floor under the seat, with the added issue of additional luggage in the compartment shifting.  I considered the alternative of holding the laptop by the handle while sitting, so it won't be any contact with the aircraft's floor. This is impracticable during cruise, but I thought it could be better during the take-off and landing segments. Another option I considered is to wrap it with completely with bubble wrap before boarding the plane.   Which is the safest way to transport a laptop during flight? app crash in the dealloc I don't really remember the plot but I think the a couple of alien girls (look human) crash land on Earth and are helped by human boy (18-19 ish). They get back to their ship but the older girl, with white hair, decides to stay on Earth to be with the boy.  At the beginning of the TV movie the boy wakes up and uses a ham radio and then goes to work on a ranch/farm(?).  I think it might have been one of these old Disney Sunday night movies. What techniques, tricks or otherwise have you used to get upgrades on flights? I've travelled a lot.  Living in New Zealand or the UK means anywhere is likely a flight, but I've always flown economy.  Twice between LA and Auckland I managed to get the exit row after talking nicely to the check-in girl, but apart from that, nothing.  I've spoken to ticket agents, tried 'check in chicken' (where you wait until the last minute before checking in, hoping there's an overbooking of economy) but have never managed to get an upgrade, while others I know seemingly get them quite often.  What strategy have you used or do you suggest to achieve this?  My next flight is from Melbourne to Tokyo, and I plan on trying all of these ;)  (Related questions on  and  upgrades) I compiled the following file (through MiKTeX which I have just updated all files), and I do not get the junk.pdf file inserted.  \documentclass{report} \usepackage{pdfpages} \begin{document} qwe \includepdf[pages=-]{./junk.pdf} \end{document}   The .log and junk.pdf file are there: ;   OK, yes it works with pdflatex, but I have to use latex->dvips->ps2pdf because of other constraints insertion of EPS figures). Beside, I do not know how to use the suggested lastpage option.  Using \includepdf[nup=2x2,frame,pages={1-13}]{./junk.pdf} I do correctly get 5 pages which should have included junk.pdf, but I get blank pages with a black dot in the center. Add an image directly from the clipboard I've tried to find other questions covering this, but (surprisingly) I did not find any.  When I want to add a screenshot to a post, as far I know the only way to do it is to save it as a file and then upload the file, using Stack Overflow's image hosting. OK, much better than finding a hosting site yourself, but sometimes I wish I could just paste the image from the clipboard.  It's not as straightforward as it may seem, I know. , and it needs a Java applet to get it done. I think everybody with a history of participation can't help but notice the explosive growth of repeated duplicate questions. The work of looking for duplicates and then closing questions has overtaken the work of actually answering questions.  It's become virtually impossible to ask something which hasn't been yet asked. Lately I feel boredom each time I see a new question and start answering it only to realize after the first written sentence that I have answered similar questions five times over or seen them answered some ten times or more. I know where it's going to be going and what answers with what votes it is going to receive before any answer is even written.  It's obviously not the administration's fault, it is simply so. The questions is, what to do about it? Engaging more moderators to close and close duplicates won't work because it's already starting to repel users who get mad at their questions closed and become afraid of asking more or perhaps just go away.  The original idea of Jeff stated the the site is for questions that can be answered. Meaning no open-ended discussions. When I first read this I had a casual thought - well, and what's gonna happen when they all are asked and answered? Will it become a museum, a monument of wisdom and knowledge or what?  I'm not sure what to do about it. Perhaps deprecation/versioning of older questions so that their new versions can sparkle the tiresome evening...  POSTSCRIPTUM.  I recall Star Trek Voyager episode  when another Q asked Captain Janeway for asylum. He was tired of immortality and wanted to die. They opened a hearing and went on to visit the continuum to evaluate the living conditions there which caused the suffering and the wish to escape it in death. A lifeless picture presented itself to the visitors... a house lone in an open space, two people going about their business, nobody talking. When asked why they were silent, the following was said. It's been so long, all has already been said, all stories told, all jokes are made... there is nothing left to do...  Are we there as well?  UPDATE: Just saw this answer in another question:       Also, some of the core questions got asked early on in the life of the site. Great questions still come around from time to time, but many have already been asked.   Doesn't that confirm my point? find $\sum_{k=2}^{\infty}\frac{1}{k^2-1}$ Do full frame sensors gather more light than crop sensors? Lots of people say that full frame sensors receive more light than cropped sensors. I have never found a proof of this claim so I tried to do the computation by myself, and proved the contrary! Could you tell me if I am wrong ?  We want to compare the same frame with the same depth of field. I'm not concerned by the quantity of photons by photosite, which is unrelated to sensor size but to the density of pixels. I have neglected effects like vignetting or angle effect on the edge of the micro-lens array. Here is my simple reasoning :  If you want the same  α~2arctan(size/2f) with a full-frame sensor and a crop sensor with crop ratio c, you have to multiply the focal length by approximately c. Now, in order to maintain the , the f-number N have to be divided by c. If we measure the "amount of light" with the well defined  Ev provided by the same frame of the same scene (so the  is fixed), we have Ev ~ f/N.  Putting all together, Ev_crop = Ev_ff x c², so the cropped sensor receive more light than the full frame sensor !  For those who are interested in the price of two equivalent systems, one with a FF+50mm+135mm and the other with Crop+35mm+85mm, see this . Solve $\frac1x+\frac1y=\frac1{pq}$ For $x,y\in\mathbb{N}$ how many ordered pairs $\left(x,y\right)$ satisfy   $\dfrac{1}{x}+\dfrac{1}{y}=\dfrac{1}{pq}$ where $p,q$ are distinct primes? I bought a Mac (13", early 2011) almost 5 years ago. When I first got it, it was running under OS X 10.7 and it was pretty fast. I've being upgrading it ever since and it's now running under Mac OS X 10.11.  I guess it didn't totally survive the upgrades because, today, there's a lot of bugs, freezes, lags, "spinning beach ball" appearing,... for example, when I write something on a normal program/editor, the cursor freezes for a few seconds, then catches up to what I'm writting.  As you can guess, that's really annoying! I've been thinkning about upgrading the hardware but I don't know what to do: should I change the RAM to 8 GB - 1 333 MHz (currently my computer has 4 GB - 1 333 MHz)? Or should I upgrade to an SSD (which is pretty expensive and difficult to install)?  Thank you very much. How to perform hard / cold reboot of iPhone or iPad? Why isn't there a continuously differentiable surjection from $I \to I \times I$? I was asked this question recently in an interview. Why can't there be a a continuously differentiable map $f \colon I \to I \times I$, which is also surjective? In contrast to just continuous, where we have examples of space filling curves.  I have one proof which is direct via Sard's theorem. But the statement seems simple enough to have a proof using at most implicit (and inverse) function theorem.