grub2 issues after upgrade
How can I repair grub? (How to get Ubuntu back after installing Windows?)
How to fix apt: Signature by key uses weak digest algorithm (SHA1)? How to check if a String contains another String in a case insensitive manner in Java? Suppose I have a line segment of length $L$.  I now select two points at random along the segment.  What is the expected value of the distance between the two points, and why? Contacts in Mavericks Messages display phone numbers instead of contact names Since updating to Mavericks the Messages app doesn't display the contact names for people I've been communicating with iMessage, it shows their phone number instead. My messages thankfully still stay synced between my iPhone and Messages on Mavericks. Platform diving: How deep does one go into the water? I am a platform diver. I am trying to figure out how deep in the water I go depending on which platform I dive from.  The platforms are 1m, 3m, 5m, 7.5m and 10m above the water surface.  By ignoring air resistance (we assume that I do not do any tricks) I can easily compute the energy that my 90 kg body has when it is hitting the water:  E = mgh = 0.5mv^2   My problem is to find the deceleration in water and thus how deep my feet will go into the water before coming to a halt. We can assume that I stand straight and fall straight down and have a height of 190cm.  How do I compute that? int fn();  void whatever() {     (void) fn(); }   Is there any reason for casting an unused return value to void, or am I right in thinking it's a complete waste of time?  Follow up:   Well that seems pretty comprehensive.  I suppose it's better than commenting an unused return value since self documenting code is better than comments. Personally, I'll turn these warnings off since it's unnecessary noise.    I'll eat my words if a bug escapes because of it... After uninstalling a program with apt and reinstalling it in another location (ex. pypy with snap), running the program from command line reports bash: /usr/bin/pypy: No such file or directory, but which pypy correctly gives /snap/bin/pypy. How do I get the shell to recognize the new installation location? Shouldn't this be a pretty straightforward operation? However, I see there's neither a size() nor length() method. Is there any good reason that an empty set of round brackets (parentheses) isn't valid for calling the default constructor in C++?  MyObject  object;  // ok - default ctor MyObject  object(blah); // ok  MyObject  object();  // error   I seem to type "()" automatically everytime. Is there a good reason this isn't allowed? Inertial frames of reference I'm struggling with the notion of an inertial frame of reference. I suspect my difficulty lies with the difference between Newtonian and relativistic inertial frames, but I can't see it.   I've read that Newton's laws apply in any non accelerating frame of reference, which are called inertial frames. So, if I play pool on a train moving with uniform velocity, the balls behave in the same way as if I were playing pool in a pool hall. So the train is (to a good approximation, ignoring forces caused by the Earth's rotation and movement around the Sun etc) an inertial frame.   I've also read that in an inertial frame, Newton's first law is satisfied. So, if I slide a rock on a sheet of ice and I could somehow eliminate the frictional forces between the rock and the ice, the rock would carry on sliding for ever, as predicted by Newton's first law.   Question 1 - is the  sheet of ice also therefore a good approximation to an inertial frame?  Question 2 - are these two definitions of inertial frames saying the same thing in different ways?  Both these examples occur in gravitation fields, which doesn't seem to matter as both the train and the ice sheet are presumably good approximations to inertial frames.  Question 3 - is gravity irrelevant when defining these two inertial frames?  In special relativity, I've read (Foster and Nightingale) that an inertial frame is also one where Newton's first law holds. But as it's special relativity there cannot be an inertial frame if there's a gravitational field, so I'm assuming the above two examples are not inertial frames in special relativity.  Question 4 - how come you can use the same definition of an inertial frame (satisfied Newton's first law) but in the case of special relativity, the train and the ice sheet aren't inertial frames. Is this to do with not being able to synchronize clocks in a gravitational field?  In general relativity, I've read (Schutz) that a freely falling frame is (on Earth) the only possible (and local) inertial frame. So again the first two examples would not be inertial frames in general relativity.  Question 5 - am I right to think that my two examples aren't even approximate approximations to an inertial frame in relativity?  Question 6 - have I missed anything else that might be useful?  Many thanks  Edit. On reflection, am I right in thinking that because Newtonian mechanics assumes universal, absolute time we don't need to worry about synchronizing clocks in a Newtonian inertial frame. Therefore we don't need to worry about gravity in a Newtonian inertial frame, because in such a frame gravity does not affect time.  This is not the case in spacetime, as here gravity does affect time and the only way to have synchronized clocks in an inertial frame in spacetime is: 1. have no gravitational field, or 2. use a local, freely falling frame.  Am I on the right track here? Initializing a member array in constructor initializer How to force Windows to rename a file with a special character? I have a song that Windows can't play because there is a question mark in the name of the file.  "Where Have All the Cowboys Gone?.ogg" // as an example   So I try to rename it and Windows complains whether I try it in Explorer or from command prompt.  Error I get when trying to copy, rename, or move is:     The Filename, directory name, or volume label syntax is incorrect   Is there a Windows way to force a rename in this case?   Update  I'll keep an eye on this question, but after 13 answers and many attempts (aside form 3rd party solutions) it seems that Windows can't do this (or at least my windows can't, no short names). So I'm accepting the answer which was my original solution anyway of using Linux. It would be nice to see Windows handle this somehow, so don't stop just because I've accepted this answer, the question still stands! I have a samba share on my LAN that requires a username and password to obtain write access (otherwise it defaults to read-only).  I can't figure out where in the Unity desktop I can connect to the share and be prompted for my login credentials.  I can mount the drive, of course, but then I'm browsing as a guest (read-only).  What gives? Given $a>b>2$ both positive integers, which of $a^b$ and $b^a$ is larger? Given $a&gt;b&gt;2$ both positive integers, which of $a^b$ and $b^a$ is larger?  I tried an induction approach. First I showed that if $b=3$ then any $a \geq4$ satisfied $a^b&lt;b^a$.  Then using that as my base case I tried to show that given any pair of positive integers $a,b$ satisfying $a&gt;b&gt;2$ and $a^b&lt;b^a$, then $(a+1)^{b+1}&lt;(b+1)^{a+1}$ - but that is where I got stuck.  Any help would be appreciated. Is there an "exists" function for jQuery? I can't remember the gender of the main character.  I remember bits and pieces from different books, but I think they're all part of the same series. The pieces may not be in order or from multiple books.   Boy somehow ends up in a mirror universe that's darker and seems to have no people. He has to travel to a certain office(?) building and steal a book. I think this is towards the end of the book (I can't remember the events leading up to it). I think he finds the portal in a forest or something behind his school. He goes into the ocean with mermaids or something and has to save the ocean from pollution. Aliens exist and are observing Earth, because they think it's undeveloped and are waiting for them to be advanced enough. His mother ends up in hospital and he does something to save her. He goes to Ireland(?) and enters a mountain or something to find a race of people. I can't remember who showed him how, but I'm pretty sure she used magic. He goes to Mars and saves a race from war with themselves(?). This place was hidden inside an illusion. He's also grouped with a linguist that learned their language. He travels to another world where there's a prince. I can't remember, but I think it might've been part of a tournament. His sister goes to a robot planet through a portal. I think the actual planet was a robot/AI and had lots of little robots on it. Can't remember what happens here, but he goes there and saves her from something.   It was set a few years ago, when computers weren't common (his family got one early in the first book, I think).  Thanks in advance if someone finds it. How to find out how many games I have won with a specific race on ladder 1v1?  The profile screen just gives me the total wins and losses but I play with all three races and I would like to know my stats per race.  Thanks.  PS: I have been playing Starcraft from the release date but I don't have the old replays as I format my computer often. What's the difference between semicolon and double ampersand && What is the difference between  echo "Hello " ; echo "world"   and  echo "Hello " &amp;&amp; echo "world"   Both seems to run the two commands after each other. Windows 10 lets you 'schedule' a reboot for later. I want to disable it.  Evidently Windows scheduled itself for a reboot last night when I wasn't looking and just closed everything I had been working on the night before.  I reboot on the regular; I don't need Windows to do that for me.  Can I disable it completely? I don't mind if it downloads everything, and then says "hey, you should reboot," but it should never reboot itself, ever.  I'm using the "Pro" edition of Windows 10. Two very closely related questions:  If a card has two different "Sacrifice this creature for X" abilities on it, does sacrificing it give both benefits?  Likewise, if a card requires a creature to be sacrificed, but that creature has a "Sacrifice this creature for X" ability, do you get the sacrifice benefit when you sacrifice it for the other requirement?