C++ static object declaration in .cpp file
Undefined reference to static class member
How do you prove that these four definitions of the operator norm are equivalent? $$\begin{align*} \lVert A\rVert_{\mathrm{op}} &amp;= \inf\{ c\;\colon\; \lVert Av\rVert\leq c\lVert v\rVert \text{ for all }v\in V\}\\ &amp;=\sup\{ \lVert Av\rVert\;\colon\; v\in V\text{ with }\lVert v\rVert\leq 1\}\\ &amp;=\sup\{\lVert Av\rVert\;\colon\; v\in V\text{ with }\lVert v\rVert = 1 \}\\ &amp;=\sup\left\{ \frac{\lVert Av\rVert}{\lVert v\rVert}\;\colon\; v\in V\text{ with }v\neq 0\right\}. \end{align*}$$ Is there a way to copy maintenance plans from one SQL Server 2012 to another? Both servers are not accessible via the same copy of Management Studio at the same time (on different networks). Finite Cartesian Product of Countable sets is countable? Is the finite Cartesian Product of Countable sets countable?  If possible, could you give a bijection that would work for any example?  Any help would be appreciated. How to select kernel for SVM? How does the radius of a pipe affect the rate of flow of fluid? Poiseuille's law states that the rate of flow of water is proportionate to $r^4$ where $r$ is the radius of the pipe. I don't see why.  Intuitively I would expect rate of flow of fluid to vary with $r^2$ as the volume of a cylinder varies with $r^2$ for a constant length. The volume that flows past a point is equal to rate of flow fluid, and thus it should vary with $r^2$.  I cannot understand the mathematical proof completely. Is there an intuitive explanation for this? Where is Jon going? At the end of S08E06 of Game of Thrones, Jon Snow along with Tormund and others of the Night's Watch      leave the Night's Watch.   and go into the woods.  Where are they going? And why? Can a script modify an environment variable of its calling shell? I am setting my JAVA_HOME in my ~/.bashrc file.  Now, I need to create a script that will change the JAVA_HOME just for the current terminal, so that I can start an app that needs java 5.  I have created this script to do this task, but after finishing, I can see that JAVA_HOME is not updated  export JAVA_HOME=/usr/lib/jvm/java-5-oracle/ export PATH=$PATH:$JAVA_HOME       Here is the result  $ ./javaHome5.sh $ echo $JAVA_HOME /usr/lib/jvm/java-6-oracle/   I think that the reason this is not being applied, is that a script is executing in it's own terminal, so when the script ends, the current terminal will not be affected.  Currently, the only way I've found around this is:   Edit my ~/.bashrc and change the JAVA_HOME var Run source ~/.bashrc to apply the changes in current terminal. Which again cannot be applied in a script, as the source command needs to be run in the current window.   Needless to say, this change applies to all new terminal windows, so I practically need to do this twice: One before starting my app, and one more time right after this, just to restore the environment vars to their default. That's not really convenient.  Do you have any ideas how can I change this var using a script? How to install all possible media codecs from console?  Is there a way to load and save them for some cases without Internet connection?  Thanks in Advance! How to install Ubuntu 18.04 alongside Windows 10 How to install Ubuntu 18.04 alongside Windows 10?  I have tried different process to install Ubuntu 18.04 in my PC in dual boot mode alongside Windows 10. But it turned out that most of the process didn't worked for my PC. My PC's configuration is 500 HDD, 3.5GHz Intel processor, 4GB RAM, 1GB Intel graphics &amp; supports both BIOS &amp; UEFI. Mathematical Induction Question About A Basis Step How can I list references from BibTeX file in-line with commentary? I would like to take the full citation of a reference in my BibTeX file and write commentary in-line after it.  A \fullcitation{id} command would be perfect.  I would like to use it as:  \fullcitation{id1}   This paper talks about A with applications to B.  \fullcitation{id2}   This paper considers how C affects A.  Whenever the \fullcitation{id} command appears, I want it to be replaced with the full reference, including authors, title, journal, and date.  Is this possible? Cleaning wax and pesticide from apple skin I checked my  to see whether I can find something similar to the main-site flag-history for chat-flags, but didn't find anything. I recently had the (dis)pleasure of regularly having to deal with a user, that has been deleted multiple times. Whenever they show up (with the same nick-name) again I have to flag them again. I'd like to get an overview of how often I had to do that, and whether my flags were helpful for the moderators. As such I propose the implementation of a flag-history as it is already in place for the main-site for chat-flags, that request moderator intervention. To be completely clear I am not talking about the 10k user flags, which are acted on in a matter of sometimes seconds with instantly visible results, but about moderator attention flags from this menu: Good reasons to prohibit inheritance in Java? What are good reasons to prohibit inheritance in Java, for example by using final classes or classes using a single, private parameterless constructor? What are good reasons of making a method final? How to fix 'Android is starting' optimization on every boot? I recently updated to Lollipop on a Moto G (1st Gen).   It was running a bit slow, so I wiped by cache then performed a factory reset as recommended.  I now receive the 'Android is starting optimising app xx of xx' every time I boot.   Obviously not life and death, but it's annoying to have to wait 10 minutes for every reboot.   Is this a known issue and is there any way to fix this? It stands to reason: if it didn't, the entire sky would be covered with stars shining blindingly day and night.  But what causes a light wave (or an electromagnetic wave) to fade if there are no celestial bodies in its way? Or, alternatively, why doesn't it fade sooner? Some stars are visible to the naked eye that are hundreds of light years away. Others, closer, can only be detected with the aid of a telescope. Why? Disposing WPF User Controls What documentation does a Mexican citizen need to fly domestically within Mexico? If a Mexican citizen, residing in Mexico, wants to fly domestically, what documents are needed?   Example: Flying from Torreon to Cancun (different states in Mexico) My advisor wants me to include a name of someone who has no contribution to the paper My first advisor wants me to include my second advisor's name in a paper that I worked on before she (2nd advisor) came along.   Should I include her name even though she didn't do anything in that paper? I don't think she even read it. Email Deliverbility How can I enable permissions to edit Email Deliverability access level? Currently it is not editable and in system mode. I need to edit it and set it to "All Email so I can test Approval and workflow functionality.