How to overwrite contents of a dir without deleting anything?
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Trim string in JavaScript? How do I trim a string in JavaScript? That is, how do I remove all whitespace from the beginning and the end of the string in JavaScript? Arduino Boost Converter. Connecting load makes converter non functional We've just been learning about complex numbers in class, and I don't really see why they're called numbers.  Originally, a number used to be a means of counting (natural numbers).  Then we extend these numbers to instances of owing other people money for instance (integers).  After that, we consider fractions when we need to split things like 2 pizzas between three people.  We then (skipping the algebraic numbers for the purposes of practicality), we use the real numbers to describe any length; e.g. the length of a diagonal of a unit square.  But this is when our original definition of a number fails to make sense- when we consider complex numbers, which brings me to my main question: what is a rigorous definition of 'number'?  Wikipedia claims that "A number is a mathematical object used to count, label, and measure", but this definition fails to make sense after we extend $\mathbb{R}$.     Does anyone know of any definition of number that can be generalised to complex numbers as well (and even higher order number systems like the quaternions)? Problem:  If $\gcd(a, b) = 1$ and If $ab = x^2$ ,prove that $a$, $b$ must also be perfect squares; where $a$,$b$,$x$ are in the set of natural numbers  I've come to the conclusion that $a \ne b$ and $a \ne x$ and $b \ne x$ but I guess that won't really help me.. I understand that if the $\gcd$ between two numbers if $1$ then they obviously have no common divisors but where do I go from this point?  Any tips at tackling this would be great. It looks quite easy though I'm still trying to get my hand around these proofs! Any pointers in the right direction would be great.  Thank you in advance, Desktop link to Eclipse Create ArrayList from array I am going to Canada, I have a valid U.S. tourist visa (B1/B2). Can I transit via a U.S. airport on the way to Canada with this visa? Logically I know I can since I am allowed to enter the U.S. but I am just making sure. Using "recently" with past simple Is it fine to use recently with the past simple tense in the following sentence?     Did you read any books recently?   Is it grammatically correct?  Or do I have to use:     Have you read any books recently? Limit values of struct member The following you could have seen in  (sorry, I've commented there, so you won't see it anymore) in Chrome 35.0.1916.153 m (current version). Notice how the add comment link overlaps the bounty box:    The same you can observe with a comment box on other sites, e.g. at this time in :    Could you shift it a bit down ?  It seems that it happens on more than just Stack Overflow (maybe all sites ?). If $G$ is a compact topological group, how to show that a finite index subgroup of $G$ is open ? I really don't know where/how to start...  PS : I precise that by "compact" I mean that it is hausdorff and that any recovering of $G$ by open sets has a finite sub-recovering (sorry if I wasn't unclear) Background not changing using gsettings from cron I'm trying to change my wallpaper to a random image using Indrajith Indraprastham's suggested script here:    When I run the script from a terminal window, the bg changes just fine, but when it's run from cron, I'm mailed this error:     (process:21901): dconf-WARNING **: failed to commit changes to dconf: Error spawning command line 'dbus-launch --autolaunch=00216c114dcf433c9bb9009985d607d6 --binary-syntax --close-stderr': Child process exited with code 1   I would appreciate any suggestions. Grub not loading after Windows 8 Install Friendly way to make previous large calculation results reusable in a new session In the past month, I've been really busy with the university and stuff, and I don't sleep as much as I used to. I usually sleep 4-5 hours a night.  I haven't been doing that extensively ( I always kept a good sleeping routine), but can the lack of sleep affect my health on the long term ? Inductive proof of the closed formula for the Fibonacci sequence How to describe "object" arguments in jsdoc? Checking for null before event dispatching... thread safe? Something that confuses me, but has never caused any problems... the recommended way to dispatch an event is as follows:  public event EventHandler SomeEvent; ... {     ....     if(SomeEvent!=null)SomeEvent(); }   In a multi-threaded environment, how does this code guarantee that another thread will not alter the invocation list of SomeEvent between the check for null and the invocation of the event? Maximal ideals in the ring of real functions on $[0,1]$ Let $S$ be the ring of all continuous functions from $[0,1]$ to $\mathbb R$. How to prove that all maximal ideals of $S$ have the form $M_{x_0}=\{f\in S \mid f(x_0)=0\}$?   Thanks in advance. Which way is up? (electric outlet)