Finding ${i^i}^{i\cdots}$
Complex towers: $i^{i^{i^{...}}}$
What is a tainted kernel in Linux? Is there a way to absolutely force a Log Out, Shut Down, or Restart with open tabs and unsaved documents? I could not find any relatively simple way to log out of a public use Mac quickly with many tabs open and unsaved document in the background without resorting to sudo shutdown -h now.  The reason I ask is that sometimes a user will have his/her account logged into the iMacs here at school and they would try to log off and then leave, thinking it has completed but the process is interrupted by Safari and Office apps, leaving their account, mounts, and websites still accessible to the next person who sits down.  Obviously a shortcut string would be nice instead of posting a note telling the person to type arcane things in a terminal. For example, just having them try to find Terminal.app is going to be a chore.  This doesn't seem to make sense because the user can just quit each app and click a few dialog boxes but unlike you and I to whom repeatedly pounding Command-Q while hitting the spacebar and D keys are probably second nature. Can jQuery .load append instead of replace? Counting surjective functions We have $r$ objects and $n$ boxes. I have to count all the combinations possible if the objects and boxes could be both different. If that happens I can count the number of variations from $n$ to $r$ (number of functions between objects and boxes). I mean, $n^r$.  But if I have to count all the combinations possible if anyone of the boxes is empty ($r\ge n$). Now I have to count the surjective functions.  For example if I have $r$ objects and 1 box. The number of surjective functions is 1. Then, if I have $r$ objects and 2 boxes, the number of surjective functions is $2^r-2$. And finally if I have $r$ objects and 3 boxes, I will count $3^r-2\cdot[3\cdot2^r-3]$. How do I get the formula for $r$ objects and $n$ boxes? Canonical Post #2: What is the perfect, and how should I use it? Desktop link to Eclipse I was tring to install eclipse on ubuntu. What I did: I unzipped the tar archive of eclipse. I tried to start eclipse from the command line - like this - ./eclipse. It works. But then I tried to create a desktop icon with: gnome-desktop-item-edit ~/Desktop --create-new. In a new icon I showed the path to the eclipse executable which I could launch from the command line. But then eclipse does not start stating:  A Java Runtime Environment (JRE) or Java Development Kit (JDK) must be available in order to run Eclipse. No Java virtual machine was found after searching the following locations: /home/artem/eclipse/jre/bin/java java in your current PATH   The same message appears if I try to launch eclipse by double-clicking its original launcher. So it starts from the terminal but not from the desktop (it does not start when double-clicked) And also I get a message in the terminal (at some stage it appeared):  (gnome-desktop-item-edit:8998): Gtk-WARNING **: Attempting to store changes into `/root/.local/share/recently-used.xbel', but failed: Failed to create file '/root/.local/share/recently-used.xbel.DSV8LW': No such file or directory   I am using Ubuntu 12.04 x32 and eclipse Juno.  PS. PATH variable points at jdk/bin and JAVA_HOME - to the jdk folder PSS. I actually set the environment variables through .bashrc file(JAVA_HOME and PATH) I have a .net client application which is connected to a remote database. Is it safe to keep a single connection open for the lifetime of the client (hours)? Does the answer hold if I have multiple (10 or 100) clients running? When I launch certain programs from the command line like eclipse and document viewer in 11.10 it spews a load of information that seems inconsequential.   Also when they are run in the background they sometimes continue to produce output to the terminal which I am currently working on, which is irritating.  I would like them just launch and keep the background stuff in the background. My reasoning is that if you launch these programs through the GUI (eg double clicking on an icon) these messages are never shown to me, so I don't need them in the command line. How do I remove a configuration object from the active configuration? I'm writing a custom module for Drupal 8. It defines a field storage configuration object, in a file called modules/mymod/config/install/field.storage.bloom_stem.bs_twitter_ac.yml.  The problem is that this is not removed when I uninstall the module; it is apparently left behind because, when I re-install the module, I get a crash.   drush -y pm-uninstall mymod drush cr drush -y en mymod      exception 'Drupal\Core\Config\PreExistingConfigException' with message 'Configuration objects (field.storage.bloom_stem.bs_twitter_ac) provided by mymod already exist in active configuration'   So it seems I need to some how manually remove this configuration object. Do I need to provide some more code that deletes it when the module is uninstalled? How can the contact point of rolling body have zero velocity? They say that for a rolling body, the velocity of the contact point is zero. I'm not getting this. How can it be zero when it's in continuous motion? Is short-circuiting logical operators mandated? And evaluation order? How to get product recommendations Possible Duplicate:          I have a question of the form "what companies provide service X?"  I checked meta, and apparently such questions are highly discouraged on all Stack Exchange sites. Which is fine, but it obviously raises the meta-question: Where can I ask my question?  (In particular, I know that there are people hanging out on Stack Overflow who have probably needed the same service, so if an answer exists, they possess it...)  Edit: I should perhaps point out that the service I'm looking for is rather specific and slightly obscure. Otherwise, yeah, this would be a 10-second exercise with Google. The replier's From email address is modified when Marketing Cloud RMM forwards an email to the routing address We've set up RMM to forward replies to routing address and SFMC adds our subdomain to the replier's From email address (i.e. replier@gmail.com becomes replier.gmail.com@oursubdomain.com). However, their reply-to address remains the same.  It seems like DMARC Forward Reply Rewrite is enabled, but we were advised not to touch it as that may affect email deliverability.  Is there any workaround to this? And what will happen if we disable this feature? Map from real numbers to real numbers as abelian groups If $f(x)$ is differentiable at x, I need to prove that $\lim_{h\to0}\frac{f(x+h)-f(x-h)}{2h}$ exist and is finite.  so if $f(x)$ is differentiable at a $x$, the difference quotient exist for this point, and also $f(x)$ must be continuous at x as well  so that mean that:  $\lim_{h\to0^+}\frac{f(x+h)-f(x)}{h} =  \lim_{h\to0^-}\frac{f(x+h)-f(x)}{h}$  and that: $\lim_{x\to x_0^+}=\lim_{x\to x_0^-}=f(x_0)$  I know I should probably use arithmetic limit laws to prove this but I can't see how what I figured out could help me. any help with that?  Thanks! What's the difference between "I love singing" and "I love to sing"? I would like to know what the difference is between "I love doing something" and "I love to do something".  For example:        “I love singing.”      and,        “I love to sing.”      When I was young, I was told that "love doing something" is right, but one day, I found Jessie J wrote "I love to sing" on her Instagram. How can you tell when a participle is being used as an adjective?  I feel completely lost trying to guess. Just as a completely arbitrary example   For every dedicated scientist patiently recording atmospheric pressure and wind speed while shivering at high altitudes, there is a carnival barker with a bevy of pretty girls willing to dangle from a basket or parachute down to earth. Sometimes when you're downloading an image and the connection breaks mid stream, you are left with a half downloaded image. If you try to view it you get the upper part of the image and the bottom part is usually coloured grey or green or some other color.  In other words, it is corrupted.  Is there a way to check whether the image is damaged in that way or otherwise corrupted? Strange floating-point behaviour in a Java program In my program I have one array with 25 double values 0.04 When I try to sum these values in a loop I get following results:  0.0 + 0.04 = 0.04 0.04 + 0.04 = 0.08 0.08 + 0.04 = 0.12 0.12 + 0.04 = 0.16 0.16 + 0.04 = 0.2 0.2 + 0.04 = 0.24000000000000002 0.24000000000000002 + 0.04 = 0.28 0.28 + 0.04 = 0.32 0.32 + 0.04 = 0.36 0.36 + 0.04 = 0.39999999999999997 0.39999999999999997 + 0.04 = 0.43999999999999995 0.43999999999999995 + 0.04 = 0.4799999999999999 0.4799999999999999 + 0.04 = 0.5199999999999999 0.5199999999999999 + 0.04 = 0.5599999999999999 0.5599999999999999 + 0.04 = 0.6 0.6 + 0.04 = 0.64 0.64 + 0.04 = 0.68 0.68 + 0.04 = 0.7200000000000001 0.7200000000000001 + 0.04 = 0.7600000000000001 0.7600000000000001 + 0.04 = 0.8000000000000002 0.8000000000000002 + 0.04 = 0.8400000000000002 0.8400000000000002 + 0.04 = 0.8800000000000002 0.8800000000000002 + 0.04 = 0.9200000000000003 0.9200000000000003 + 0.04 = 0.9600000000000003   Why on earth could that happen?! How to colorize an image as in the example? I have seen such an effect being used in many places however I haven't figured out how to replicate it via Photoshop.  I have tried desaturating the image, placing it under a layer of solid colour and then lowering the opacity of the colour. I have also tried a couple of blend modes, to no avail. The effect is nowhere near the same.  Can someone please tell me the effect used on these images?