javascript code execution time
How to measure time taken by a function to execute
Beginner here with an issue on a simple presentation using beamer  \documentclass{beamer}  \begin{document} \begin{frame}   \tau \epsilon \chi \end{frame} \end{document}   The above fails with the message "! Missing $ inserted." and waits for me to do something when converting to pdf. I have tried adding the instruction \usepackage[utf8]{inputenc} and also \usepackage[greek]{babel}. I have not seen references either to needing to use any other package. What is exactly I am missing? What is a good website to hack around using Selenium? I want to learn Selenium, but I don't know what to code. Sure, I can throw Google some queries, I can fill out some forms, press buttons, find divs and links, etc. But I think this stuff is pretty basic.  What would be more "advanced" ideas to try out? Can you give real-life examples? If I was at point $A$ and I wanted to walk directly to point $B$, I would have to walk half way to point $B$, but before that I would have to walk half way to halfway to halfway to point $B$ and half of that again and so on and so fourth. if I halved this distance an infinite amount of times then there would be an infinite amount of actions I would need to perform in order to cross from $A$ to $B$. Therefore, if each action took any quantity of time at all, then it would take me an infinite amount of time to cross from $A$ to $B$, even if $A$ and $B$ were only a few centimetres apart!   Because I am not infinitely old and I can move, there must be a flaw in this logic. Where is it? Two friends who have unpredictable lunch hours agree to meet for lunch at their favorite restaurant whenever possible. Neither wishes to eat alone and each dislikes waiting for the other, so they agree that each will arrive at a random time between noon and 1 pm, and each will wait for the other for 15 minutes or until 1:00. What is the probability that the friends will meet for lunch on a given day? Now that Unity is gone, the usual way of setting a Compose Key (via Keyboard Preferences > Layout) no longer works (because in Ubuntu 18.04, Devices > Keyboard has no Layout tab).  How do we set a Compose Key in Ubuntu 18.04 Bionic Beaver? We have to shift our web-site to a new domain due to some unavoidable circumstances. The portal has been up and running there since 2009.  It has good index in various search engines and we are getting a good number of page hits on daily basis.  Losing the search hits and index are our big concern. We are not sure how best we can handle this.  What all can be done to preserve as much as possible while shifting to new domain name. Archive by Year How to tell Max CP? What are best practices for managing SSH keys in a team? I work with small teams (&lt;10) of developers and admins with the following characteristics:   Most members of the team have >1 personal computer, most of which are portable Team members have access to 10-50 servers, usually with sudo   I think this is pretty typical for most startups and small- to mid-size corporate IT groups.  What are the best practices for managing SSH keys in a team like this?  Should you share a single key for the whole team?  Should each person have their own key on a shared account ("ubuntu" on every server)?  Separate accounts?  Should each team member keep a separate key for each of their laptop or desktop computers? Syntax error while creating DB2 Trigger What is wrong in the below trigger syntax, I am getting this error An unexpected token "INT" was found following " DECLARE NULL_ROW_ID".  Expected tokens may include:  "END-OF-STATEMENT".. SQLCODE=-104, SQLSTATE=42601, DRIVER=3.68.61  CREATE TABLE A (     A_ID INT NOT NUll,     A_CODE VARCHAR(100) NOT NULL,     PRIMARY KEY(A_ID) );  CREATE TABLE B (     B_ID INT NOT NUll,     B_CODE VARCHAR(100) NOT NULL,     A_ID INT,     PRIMARY KEY (B_ID),     FOREIGN KEY (A_ID) REFERENCES A (A_ID)  );  CREATE OR REPLACE TRIGGER B_TRIGGER AFTER UPDATE OF A_ID ON B REFERENCING NEW AS N OLD AS O FOR EACH ROW     WHEN (N.A_ID IS NULL)     BEGIN ATOMIC         DECLARE NULL_ROW_ID INT;         SET NULL_ROW_ID = (SELECT A_ID FROM A WHERE A_CODE = 'Custom Null String');         IF NULL_ROW_ID IS NULL THEN             SIGNAL SQLSTATE '70000' SET MESSAGE_TEXT = 'Custom Null String row not found.';         END IF;     SET N.A_ID = NULL_ROW_ID;     END @   It's on DB2 Express-C 10.5 VBox on 14.04, Kernel driver not installed (rc=-1908) On Installing Virtual box on Ubuntu 14.04, I got following message:     Kernel driver not installed (rc=-1908)      The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a >permission problem with /dev/vboxdrv. Please reinstall the kernel module by executing      '/etc/init.d/vboxdrv setup'      as root. If it is available in your distribution, you should install the DKMS package >first. This package keeps track of Linux kernel changes and recompiles the vboxdrv >kernel module if necessary.   Then on following the   I entered these commands:  sudo apt-get install linux-headers-generic build-essential dkms sudo apt-get remove --purge virtualbox-dkms sudo apt-get install virtualbox-dkms   On Running the last command   sudo apt-get install virtualbox-dkms   I get an error:  Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable  distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies: virtualbox-dkms : Depends: virtualbox (&gt;= 4.3.10-dfsg-1) E: Unable to correct problems, you have held broken packages.   Just for reference, I checked the version of the Virtual Box, I got 4.3.16 r95972  It worked using the solution  sudo apt-get install build-essential module-assistant sudo m-a prepare   Second as mentioned in the error reinstall kernal module.  sudo /etc/init.d/vboxdrv setup   More Details are from I'm on ub20LTS and I really dislike how much top space the topmost bars use. Any idea on how to remove or reduce their numbers?  Edit: Thanks to everybody's support, this is how my workspace looks like now. I've :  Installed gnome-extensions for firefox. Turned off menu bar in ff. Installed dash to dock. Installed hide top bar.  This way you can better utilize your screen space. zsh scripting - How do I NOT match a pattern in filename generation? I'm currently trying to loop through a set of directories, but only the ones I care about.   $ ls -d */ cfdpost_statefiles/     p050L0260/  p050L0510/  p060L0390/  p070L0260/  p070L0510/  p092L0390/  p097L0260/  p110L0390/  p131L0325/  p150L0510/  profiles/ ERCOFTAC_TestSettings/  p050L0390/  p060L0260/  p060L0510/  p070L0390/  p084L0510/  p094L0325/  p100L0510/  p125L0510/  p136L0260/  p162L0260/  settings/   I want to match all the p###* directories except for the ones beginning with p125 and p150.  If I just do patterns with a pipe, I get:  $ for dir in ./p(125|150)*(/); echo $dir ./p125L0510 ./p150L0510   However, if I try and use the ^ like it shows :  $ for dir in ./p^(125|150)*(/); echo $dir zsh: no matches found: ./p^(125|150)*(/)   Any ideas how to proceed? Putting char into a java string for each N characters I have a java string, which has a variable length.   I need to put the piece "&lt;br&gt;" into the string, say each 10 characters.   For example this is my string:  `this is my string which I need to modify...I love stackoverlow:)`   How can I obtain this string?:  `this is my&lt;br&gt; string wh&lt;br&gt;ich I nee&lt;br&gt;d to modif&lt;br&gt;y...I love&lt;br&gt; stackover&lt;br&gt;flow:)`   Thanks Let $A$ be a real square matrix en let $I$ be the identity matrix with the same size. Let $n&gt;0$ be the smallest natural number for which there exist  $a_0,a_1,...a_{n-1} \in {R}$ such that $A^n+a_{n-1}A^{n-1}+....+a_1A+a_0I=O$.  Show that A is invertible if and only if $a_0\neq0 $.  So i need to proof    $A$ invertible $\rightarrow$$a_0 \neq 0$ $a_0 \neq0 \rightarrow$ $A$ invertible    I don't really know where to start with 1, and with 2 I tried to prove it with a contradiction but I don't think it's right either. No field properly between $\mathbb Q$ and $E$ iff $G(K/\mathbb Q) \cong A_4$ or $S_4$ How to power a button's LED within a guitar? I'm working on a guitar, and the plan is to use three latching push buttons so that each pickup can be turned on and off individually. I'm fairly confident that the following diagram should work for that (Feel free to correct me)   The buttons I want to use are , which have a built-in LED when turns on when the button is pressed.   Which brings me to my question: Is there a way to power the LED? If I introduce a 9volt into the wiring, wouldn't that cause problems with the guitar's standard electronics? Super+D key shortcut does not show desktop I recently installed Saucy Salamander on my computer. Previously in Ringtail, Super+D used to show the desktop. However for this release, the Super+D does not seem to work properly... Is it a bug? What does the big intersection or union sign of a set mean? In some cases, we will have to consider the union or the intersection of several, even infinitely many sets, defined in the obvious way. For example, if for every positive integer $n$, we are given a set $S_n$, then   $$\bbox[border:1px solid red]{\bigcup_{n=1}^\infty S_n}=S_1\cup S_2\cup\cdots=\{x\mid x\in S_n\text{ for some }n\},$$   and   $$\bigcap_{n=1}^\infty S_n=S_1\cap S_2\cap\cdots=\{x\mid x\in S_n\text{ for all }n\}.$$   Two sets are said to be disjoint if their intersection is empty. More generally, several sets are said to be disjoint if no two of them have a common element. A collection of sets is said to be a partition of a set $S$ if the sets in the collection are disjoint and their union is $S$.   Normally what I know is that you can make a union or an intersection between only two sets. In this expression, there is a big union of sets. I'm asking about the meaning of this expression – what does it mean? What does the infinity sign do at the top?  Things are even more complicated with De Morgan's laws, which use the same expression:     Two particularly useful properties are given by De Morgan's laws which state that   $$\left(\bigcup_nS_n\right)^c=\bigcap_nS_n^c,\quad\quad\quad\quad\left(\bigcap_nS_n\right)^c=\bigcup_nS_n^c.$$   Anyone who can explain to me the expression or De Morgan's laws would be much appreciated. For example i have the domainname buyhouse.com The keywords "buy house new york"  buyhouse.com/new-york/   buyhouse.com/buy-house-new-york/   Whats the best url option for SEO?