What is the full form of an expressionless statement in javascript?
Detecting an undefined object property
Avoiding labeling features if overlapped by another layer in QGIS? With QGIS 2.12.2, how can I set up layer labeling to avoid placing labels where features from another layer already exist?  For example, if I have a stream/river polyline layer that contains lake "centerlines", and I place a "lake" polygon layer above it in the drawing order, I don't want the river layer to place a label inside the lake.  Instead, I would rather have the river labeled outside of the lake (as needed).  That way, I can place labels from the lakes layer and I don't run into label collisions.  Here is an example, where (I have intentionally put the lines on top for visual purposes) what I am hoping to achieve is no river center-line labels shown inside the lake polygon: Remove the extra headers from the e-mails sent Make display of reputation in revisions list consistent with the user card display The user card in the revision list, for example , shows the exact amount of reputation:  This is not consistent with how the flair works on (all?) other places in the site, e.g. under a post. There, the amount is displayed in units of thousands (k):  (or, in , millions (m).) It used to be consistent, see e.g. : I have a Samsung 960 Pro SSD with Ubuntu 18.04  is it safe to put the swap file on there or would it hurt it in the long run,  I heard some people saying that new SSDs don't suffer from that issue anymore, is this true? Is is possible to skip the confirmation step while adding a repository? When I add a repository by running  sudo add-apt-repository ppa:ubuntu-x-swat/x-updates   It outputs this dialog:  Updated versions of X.org drivers, libraries, etc. for Ubuntu.  This PPA is for stable upstream releases of X.org components.  If you're looking for something even more bleeding-edge, please see the xorg-edgers PPA.  While Ubuntu does not "officially/formally" support these packages, if you discover problems when installing these debs please feel free to report bugs to launchpad.  However, please make sure to clearly state that you are running packages from this PPA so we know the fixes need to come here.  If you are upgrading from one release to another with this PPA activated, please install the ppa-purge package and use it to downgrade everything in here beforehand. sudo ppa-purge ppa:ubuntu-x-swat/x-updates will do it.  [Directions for packaging drivers can be seen at https://wiki.ubuntu.com/X/DriverBuilding]  More info: https://launchpad.net/~ubuntu-x-swat/+archive/x-updates Press [ENTER] to continue or ctrl-c to cancel adding it   I want to skip the confirmation step  Press [ENTER] to continue or ctrl-c to cancel adding it   How can I automatically confirm the addition of a PPA? Is it possible to insert arguments into functions when they're used like Function@ or //Function? Explicit space character? I'm wondering about the best way to do an explicit space character (I don't even know what it's properly called), like the ones you get in the \begin{verbatim*} environment. The closest I've found is  \sqcup   in math mode, but it seems like a bit of a hack to me. Is there any text symbol for what I'm looking for? Non-Exchange address in Exchange GAL We just made the switch to Google Apps for part of our domain. We disabled the accounts that are now on Google Apps and mail routes correctly. Our problem is that now we have no way of seeing those users in the Global Address List.  So we have these users in our Active Directory, they have no mailbox on Exchange, and we want to be able to see/search for their addresses in the GAL. Is there any way to do this?  This is Exchange 2007, if that matters. I am trying to solve:  $$\int_{-\infty}^{\infty}\frac{x\sin{x}}{x^2 + a^2}dx$$  and show that it equals $\pi e^{-a}$ for all $a &gt; 0$.  I translate it to its complex equivalent:  $$lim_{R \rightarrow \infty} \int_{-R}^{R}\frac{z\sin{z}}{z^2 + a^2}dz = \int_{C}\frac{z\sin{z}}{z^2 + a^2}dz - \int_{\gamma}\frac{z\sin{z}}{z^2 + a^2}dz$$  where C is a half circle with radius R, above the real axis, and $\gamma$ is only the curved (top part) of the half circle.  I've shown that $$\int_{\gamma}\frac{z\sin{z}}{z^2 + a^2}dz$$ tends to 0 as $R \rightarrow \infty$.  So now:  $$lim_{R \rightarrow \infty} \int_{-R}^{R}\frac{z\sin{z}}{z^2 + a^2}dz = \int_{C}\frac{z\sin{z}}{z^2 + a^2}dz$$  By residue theorem,   $$\int_{C}\frac{z\sin{z}}{z^2 + a^2}dz = 2\pi i \cdot res_{ai}f$$  as $ai$ is the pole of $f$ that lies above the real axis.  $$2\pi i \cdot res_{ai}f = 2\pi i \cdot lim_{z \rightarrow ai} (z-ai)\frac{z sin{z}}{z^2 + a^2}$$  By L'Hospital's rule, this is equivalent to:  $$2\pi i \cdot lim_{z \rightarrow ai} (z-ai)\frac{z^2\cos{z} + 2z\sin{z} - zai\cos{z} - ai\sin{z}}{2z} = 2\pi i \cdot \frac{\sin{ai}}{2} = \pi i \sin{ai}$$  But how is $\pi i \sin{ai}$ equivalent to $\pi e^{-a}$? Did I make a mistake? The story is basically told from an alien's point of view. Essentially they observed us from far off, deemed us as violent and a danger to the universe, and set course (asteroid or something) to kill us. They kept observing and saw all the art and beauty we created and realized we were actually not so bad, but by then they couldn't stop it. So it was sort of also an apology letter to Earth in the end.  First read it like a year ago online and I can't find any trace of it anymore, nor can I recall the site it was on. Anyone know what short story this is? Get full name twice in Bibliography I use biblatex with style=authoryear and when there are two references of the same author in the bibliography there is just a dash. How can I get the full name in the second entry too? Is there a clever way to show that  $$|x| - |y| \leq |x-y|$$  I believe I can think of a way to solve this using cases, but the book I'm working out of said that "A very short proof is possible if you write things in the right way" which has motivated me to figure out this quick way, but I've failed thus far and any help would be appreciated Note: This is an attempt to create a canonical question that covers all instances of &quot;low-graphics mode&quot; error that occurs to a user, including but not limited to installation of wrong drivers, incorrect or invalid lightdm greeters, low disk space, incorrect installation of graphics card like ATI and Nvidia, incorrect configuration of xorg.conf file while setting up multiple monitors among others. If you are experiencing the &quot;low-graphics mode&quot; error when trying to login but none of the following answers work for you, please do ask a new question and then update the answers of this canonical question as and when your new question gets answered.   When I try to boot into my computer, I am getting this error:  The system is running in low-graphics mode Your screen, graphics cards, and input device settings could not be detected correctly. You will need to configure these yourself.   How do I fix the failsafe X mode and login into my computer?  Answer index: I've made some high resolution pixel art in PS by drawing it down at the pixel level and then increasing the image size with the nearest neighbor setting to keep it crisp. In the web browser, however, I need to display these images as icons with a dynamic size, so I can't just size the images correctly to begin with, and the broswer seems to blur the images when rendering them smaller, while vector images seem to stay more crisp as they shrink.   So I'm wondering if there's a way to convert the pixel art neatly into vector. I'm aware of the trace function in illustrator, but it seems to do a rough job iirc. I need help with this exercise.  I need to prove $$\int_{0}^{1}x^{-x}\ dx=\sum_{n=1}^{\infty}n^{-n}$$  I think I should use some convergence theorem, but I'm stuck.  Thanks a lot! Adding a CMS to an existing Magento shop I am working on a project for 3 niche stores built on magento (using magento's multi-store function)  that each get roughly 50k unique visitors a day.  The sites don't currently have a blog or forum or any social networking aspects.    Would like to add a cms to each site that can be centrally run and would like it to take over the front end content from Magento.  Also would like it to maintain an online blog/publication of sorts with videos, articles, and the like with privileges to edit the content given to a dozen or so people with different privileges.  Want to add a forum to each site that is fairly robust and to possibly add some social networking aspects down the road, so extandability and available plugins/mods in each cms is important.  Other than shared login between the forums,blog/publication and store, would like to be able to integrate some content from the forums and blog/publication into the store as well.  After researching this a bit, I am inclined towards Drupal, but I haven't found any modules to integrate it with Magento.  Also, since the blog content will be done by about a dozen nontechnical people, I want something that is very easy to work with.  Lastly, since the site gets a good amount of traffic, speed and security are very important.  What CMS would you recommend integrating in this context?  Deciding between Drupal, Wordpress and ModX.  Also Plone as well.  Thanks. How to find the square root of a permutation Observe that  $$\begin{pmatrix} 1 &amp; 2 &amp; 3 &amp; 4 &amp; 5 \\  2 &amp; 4 &amp; 1 &amp; 5 &amp; 3 \end{pmatrix} \begin{pmatrix} 1 &amp; 2 &amp; 3 &amp; 4 &amp; 5 \\  2 &amp; 4 &amp; 1 &amp; 5 &amp; 3 \end{pmatrix} =  \begin{pmatrix} 1 &amp; 2 &amp; 3 &amp; 4 &amp; 5 \\  4 &amp; 5 &amp; 2 &amp; 3 &amp; 1 \end{pmatrix},$$  so $\begin{pmatrix} 1 &amp; 2 &amp; 3 &amp; 4 &amp; 5 \\  4 &amp; 5 &amp; 2 &amp; 3 &amp; 1 \end{pmatrix}$ is the square of a permutation. More generally, how do I check if a permutation is square and how can I find its root? Embedding a link (or other html) in a JSF message How to add a Login / Logout link in Main navigation menu? How can I add a Login link to the "Main navigation" menu?  When a user clicks on the link, it should take them to the /user/login page. Once they login, the link should change to say "Logout" instead of "Login".  Is there any way to add such a link? Idiom that means trying to save something that is beyond saving It's on the tip of my tongue.  Example: "Replacing the hard drive of this computer would be [idiom]. It's going to fail completely soon enough."