C++ array and find functions
C++ vectors (instead of arrays)
PDF video Embedding Problem I have embed an mp4 video in the PDF file as given below:  \documentclass{beamer} \usetheme{Singapore} \usepackage{media9} \usepackage{hyperref} \begin{document}  \begin{frame}\frametitle{Title}  \includemedia[ width=\paperwidth,height=0.7\linewidth, activate=pageopen, flashvars={aaa.mp4 &amp;autoPlay=true} ]{}{C:/Users/name/Desktop/aaa.mp4}  \end{frame}  \end{document}    There is no compile time error in the code but after running it this massage comes along a  blank pd f file....  "To view the Flash @R Technology content in this pd f file, please install the required version of Flash Player"  I would like to add here that I already have installed the latest version of Flash Player(Adobe Flash Player 12 ActiveX). So,Can anyone tell what version is required to be installed to obtain Video in pd f file. Which ligatures do the fonts used in my document offer? This is a follow-up question to:   In order to know which ligatures I might consider disabling (I have in mind microtype's \DisableLigatures command; some important notes about selective disabling of ligatures are found under ), knowledge about which ligatures might be applied will be very useful. Which ligatures do the fonts used in my document offer? How to escape braces (curly brackets) in a format string in .NET How can brackets be escaped in using string.Format? For example: String val = &quot;1,2,3&quot; String.Format(&quot; foo {{0}}&quot;, val);  This example doesn't throw an exception, but it outputs the string foo {0}. Is there a way to escape the brackets? This question is NOT about access to USB or external drives.  WPS Witer and other just installed Ubuntu software can NOT open files saved on my /media directory. I keep getting the annoying message: « Could not read the contents of '/media': Permission denied ».   MY SIMPLE QUESTION REMAINS:  How can I access all files and folders on my user username/media/ directory?  I'm using Ubuntu 18.04.3 LTS.  Ubuntu's Nautilus can indeed access all files and folders in all locations. However, Ubuntu's software that I have downloaded (e.g. KRITA, WPS WRITER etc) can NOT access any file or folder on the /media directory. Thanks in advance. According to the Third Newton's law of motion:        For every action there is an equal and opposite reaction.   So, I understand that if I hit a brick wall with $50\, \mathrm{lbs}$ of force, the brick wall also hits me with $50\, \mathrm{lbs}$ of force (usually painfully). In this instance, Newton's third law makes sense. What I'm confused about is, if I hit a patch of drywall with $50\, \mathrm{lbs}$ of force, it's probably going to break, and due to the lack of pain in my hand, I can tell it did not hit me back with $50\, \mathrm{lbs}$ of force.   How does Newton's third law apply to situations when one object or the other is destroyed? It certainly seems like at that point it is incapable of delivering the full force of my blow back to me. What happens with the energy? I was wondering, why there are passport checks at the check-in counter, Immigration and even at the gate?    For example, I was at Istanbul flying to either UK or US. There's a security check at the check-in counter asking a bunch of questions about my immigration status - even more than the Immigration officer at the border. Also, at the gate, there's also Security officer checking my immigration status and passport asking the same questions.    I thought that would be the responsibility of an Immigration officer rather than some third party company?   The thing I'm curious the most is they don't even know which countries this passport can go to with or without visa. They have to go back to the counter and check with the system which takes a long time. I was wondering why they hire these kind of companies to slow down the process? Why do clocks measure arc-length? Apologies in advance for the long question.  My understanding is that in GR, massive observers move along timelike curves $x^\mu(\lambda)$, and if an observer moves from point $x^\mu(\lambda_a)$ to $x^\mu(\lambda_b)$, then his clock will measure that an amount of time $t_{ba}$ given by the curve's arc length; $$   t_{ba} = \int_{\lambda_a}^{\lambda_b}d\lambda \sqrt{-g_{\mu\nu}(x(\lambda))\dot x^\mu(\lambda)\dot x^\nu(\lambda)} $$ will have elapsed where $g_{\mu\nu}$ is a metric on spacetime with signature $(-,+,+,+)$.    Why is this so?     Here is how I would attempt to justify this fact in special relativity with $g_{\mu\nu} = \eta_{\mu\nu}$.  Consider an inertial observer $O$ in $\mathbb R^{3,1}$, and suppose that this observer sees a clock, which I'll call observer $O'$ moving around on a curve $x^\mu(\lambda)$.  If $O'$ were also an inertial observer, then given any event with coordinates $x^\mu$ as measured by $O$, observer $O'$ would measure the coordinates of the event to be $x'^\mu = \Lambda^\mu_{\phantom\mu\nu} x^\nu + x_0^\mu$ for some Lorentz transformation $\Lambda$.  If $O'$ is not inertial, then this is no longer true, and there is some more complicated family of transformations, say $T_\lambda$ between events as seen by both observers.  I would argue, however, that if we were to partition the interval $[\lambda_a, \lambda_b]$ into a large number $N$ of intervals $I_1=[\lambda_a, \lambda_i], \dots, I_N=[\lambda_{N-1}, \lambda_b]$ with $\lambda_n = \lambda_a+n\epsilon_N$ and $\epsilon_N=(\lambda_b-\lambda_a)/N$, then on each interval $I_n$, $O'$ is approximately an inertial observer in the sense that $$   T_{\lambda_n} = P_n + \mathcal O(\epsilon_N), \qquad (\star) $$ for some Poincare transformation $P_n$.  Then we would note that since $O'$ is stationary in his own reference frame, he measures his worldline to have the property $\dot x'^\mu(\lambda) = (\dot t(\lambda), \mathbf 0)$ so that $$   I_{ba}=\int_{\lambda_a}^{\lambda_b}d\lambda \,\sqrt{-\eta_{\mu\nu}\dot x'^\mu\dot x'^\mu} = \int_{\lambda_a}^{\lambda_b} d\lambda \, \sqrt{\dot t^2} = t(\lambda_b) - t(\lambda_a) = t_{ba} $$ On the other hand the integral on the left can be written as a Riemann sum using the partition above, and we can invoke ($\star$) above to get \begin{align}   I_{ba}  &amp;= \lim_{N\to\infty}\left[\sum_{n=1}^N \epsilon_N\sqrt{-\eta_{\mu\nu}\dot x'^\mu(\lambda_n)\dot x'^\nu(\lambda_n)}\right] \notag\\ &amp;= \lim_{N\to\infty}\left[\sum_{n=1}^N \epsilon_N\sqrt{-\eta_{\mu\nu}\dot x^\mu(\lambda_n)\dot x^\nu(\lambda_n)} + \mathcal{O}(\epsilon_N^2)\right] \notag\\ &amp;= \int_{\lambda_a}^{\lambda_b}d\lambda \,\sqrt{-\eta_{\mu\nu}\dot x^\mu\dot x^\mu} \end{align} Combining these two computations gives the desired result.  How do others feel about this argument?  I'm not completely comfortable with it because of the assumption $(\star)$ I made on $T_\lambda$.  I imagine that in GR a similar argument could be made by invoking local flatness of the metric. How do I install PlayOnLinux on Ubuntu? I have a cron job that runs every minute on an Ubuntu 12.04 box  $sudo crontab -e * * * * * mylogin /pathto/file.sh &gt; /log/filelog   If I run file.sh, the bash script does some stuff and echos out runs:  $ ./file.sh  runs   If I check the log of cron tab it shows that the job is running:  Jul 10 12:41:01 localhost CRON[1811]: (root) CMD (mylogin /pathto/file.sh &gt; /log/filelog) Jul 10 12:41:01 localhost CRON[1810]: (CRON) info (No MTA installed, discarding output) Jul 10 12:42:01 localhost CRON[1813]: (root) CMD (mylogin /pathto/file.sh &gt; /log/filelog)   However, the script is not running. It is not doing it's work and not echoing runs to /log/filelog.  $cat /log/filelog  #shows nothing   What other steps can I take to debug this problem? Was unable to find rationale for separate tags accros SE sites.   Tag function According general definition in information systems, a  (such as an Internet bookmark, digital image, database record, or computer file). This kind of metadata helps describe an item and allows it to be found again by browsing or searching. Tags are generally chosen informally and personally by the item's creator or by its viewer, depending on the system, although they may also be chosen from a controlled vocabulary.  On SE - the same:  is a () word or phrase that describes the topic of the question help you identify  or relevant to you.  tag origin and quality  Where from tags are originated and what are tag quality parametres?  problems and contradictions examples related with SE tags  Humanity is facing information overload.  are created for collecting and sharing personal knowledge on questions or problem solving. But tag's descriptions are not matter of personal knowledge - it's just matter of , i.e. vocabulary/dictionary, or taxonomy/ontology or, speaking in general, human lexic conceptual apparatus / framework. So why time has to be spent on fact's duplicating and sharing?  At the same time We are living at the linked data times. IMHO it's the biggest blunder having same tags with different descriptions in different SE sites unlinked. Tags (and so - descriptions) should be unified.  So I'm calling to unify all tags across SE sites as feature request. Maybe automatic linking to Wikipedia and/or some other decent dictionary would be reasonable.  solution examples  This is not a duplicate of Why Are Ethernet/RJ45 Sockets Magnetically Coupled? As the title says really, why do ethernet sockets need to be mag-coupled? I have a basic understanding of electronics, but mostly, I can't figure out the right search terms to google this properly. Lat/Long co-ordinates are not plotting onto EPSG:3857 OSM basemap correctly Excuse me if this is a stupid question, but I've honestly tried to find the answer in a few threads here on SE, and I cannot seem to follow the suggested steps correctly.    Project is in  (WGS 84 / Pseudo-Mercator) BaseMap (OpenStreetMap) layer is set to EPSG:3857 Vector data has been imported from CSV, and has Lat/Long coordinates, set to EPSG:3857.    The layer appears right in the middle of the map, around 0,0 obviously.   Why is this, what am I doing wrong? Does non-mass-energy generate a gravitational field? At a very basic level I know that gravity isn't generated by mass but rather the  and when I wave my hands a lot it seems like that implies that energy in $E^2 = (pc)^2 + (mc^2)^2$ is the source of gravity.  If the total energy of a particle contributes to the generation of a gravitational field, that seems to imply some strange things.  For example, you could accelerate a particle like an electron to such a high velocity that it has enough momentum / kinetic energy to collapse into a black hole.  An observer traveling with the electron would see an electron and stationary observers would see an arbitrarily massive black hole flying by.  These observations seem to be contradictory.  The same would be true of an extremely high energy photon.  Another consequence is that a stationary particle could appear to have so much mass that it could attract / deflect the trajectory of a rapidly moving observer.  It seems odd that at low velocities you wouldn't even notice a stationary electron as you pass it by but at high velocities the gravitational field you observe could be significant enough to alter your path.  Am I correct that non-mass-energy generates a gravitational field?  If it does, how are these strange observations like a particle looking like a black hole in one reference frame but not another reconciled? "Each of these is" vs. "each of these are" Each of these CDFIs are finding solutions for communities that lack   access to traditional financial products and services, and the NEXT   Awards will accelerate their success.   OR     Each of these CDFIs is finding solutions for communities that lack   access to traditional financial products and services, and the NEXT   Awards will accelerate their success.   The difference is, the first one uses "CDFIs are" and the 2nd sentence uses "CDFIs is"  Which one is correct? Any why? Why $SU(3)$ and not $U(3)$? Is there a good reason not to pick $U(3)$ as the colour group? Is there any experiment or intrinsic reason that would ruled out $U(3)$ as colour group instead? Evaluating the indefinite integral $ \int \sqrt{\tan x} ~ \mathrm{d}{x}. $ I have been having extreme difficulties with this integral. I would appreciate any and all help. $$ \int \sqrt{\tan x} ~ \mathrm{d}{x}. $$ Recently I installed Ubuntu 16.04 on my HP Envy 17t and everything works fine. However, I need to disable the touchscreen input permanently and I tried everything I could found but nothing works.  The closest thing I could manage was to make a shell script that will run at startup (the shell script calls xinput set-prop "Touchscreen Input Name" "Device Enabled" 0 command).   However, this script will not run until I log in. My touchscreen needs to be disabled at the log-in screen.  How can I solve this? I tried modifying the 10-evdev.conf file but all I got is a purple screen and a broken Ubuntu setup. When would you call java's thread.run() instead of thread.start()? When would you call Java's thread.run() instead of thread.start()? My change password interface is not working on java eclipse web application Not able to add 3 JPanels to a main panel