Convert list into list of grouped strings
How do you split a list into evenly sized chunks?
"Overclocking" an AVR In AVR datasheets under the Electrical Characteristics section you will typically find a graph like this (this one is from the ATMega328):    I've seen designs that seem to "work" but operate outside the shaded envelope. Specifically, I've seen 3.3V (Arduino) designs that run the clock from an external 16MHz crystal. Clearly, this is out of spec. What are the practical negative consequences of running outside this envelope? I recently ordered the GTA V PC from Steam and when I finished installing and launch the game. It gave me "Grand Theft Auto V has exited unexpectedly". I tried "safe mod" and every option available, but none of them work. I checked some forums and found a lot of people having the same problems. What could be the possible cause? I'm using a laptop with these specs:  CPU: i7 4700m GPU: AMD HD8970M RAM: 8GB  I'm pretty sure my laptop is way beyond the minimum specs. Does someone know how can I enter the game? What does the comma operator do? Ubuntu 18.04: switch back to /etc/network/interfaces Starting sometime around Ubuntu 18.04, the Ubuntu devs stopped using the classic /etc/init.d/networking and /etc/network/interfaces method of configuring the network and switched to some thing called . This has made a lot of people very angry and been widely regarded as a bad move. Is it possible to remove netplan and use the correct /etc/network/interfaces method for configuring the network? How can I install Windows after I've installed Ubuntu? I have Ubuntu on my laptop. Now I want install Windows 7 in a dual-boot. How can I do this? I can't lose my Ubuntu files, and I'm afraid that I might break . Go  for UEFI only! I am non EU national, living in a Schengen country for past 5 years. I hold Indian passport and EU permanent residence card valid for 5 years.   Can i go to UK for few days to visit friends without a visa?  I am aware that UK is not in Schengen, and Schengen visas and residence permits issued by Schengen country is not valid for United Kingdom? But what about the PR card issued by a Schengen country?  I am also aware that EU citizens carrying EU passport have no restrictions to visit UK. How do I change font size on the DataGridView? Just a few questions about Hyper-V virtual machines and clustering I have been using Microsoft’s Hyper-V technology for a little while now, but I am just now dipping my toe into clustering.  In particular, I am trying to implement a fault-tolerant SQL DB. This involves setting up two VMs, clustering them via Failover Cluster, and then installing SQL Server in some fashion. I have two physical machines - one high-end and rather beefy “heavy lifter” to contain the majority of the VMs, and another “backup” (a repurposed desktop) to hold the essential “secondary” (or failover) AD-DC, SQL and FS VMs.  The main reason why I find the failover cluster at the VM level so attractive is that it presents a single IP and DNS entry to the network as a whole - if one machine (physical or virtual) goes down, you might loose some ping and the connections get reset, but the network applications (Microsoft RMS connection to backend SQL) can still connect to a viable DB without having to mess around with the settings at all.  My first question is in terms of SQL Server itself. If I have a cluster between two VMs, does it make more sense to install the SQL Server in Failover Cluster configuration or should I simply install it in a stand-alone config and mirror the DBs? For example,  suggests just mirroring the DBs, but do I just mirror standalone DBs on standalone VMs, or can I get the network and failover benefits of clustered VMs while still utilizing (on each clustered VM) standalone DBs that have been mirrored between each other?  As well, I have come across a lot of documentation about SQL clustering, but most assume a number (#>2) of physical machines to hold not only the actual SQL VMs but also the Quorum and Witness stores. I will not be able to muster more than two physical machines. As such, I will have to be satisfied with a VM cluster that does not exceed two VMs (one for each physical machine).  Another issue involves MSDTC - the Distributed Transaction Coordinator. When attempting to install the SQL Failover Cluster (I never completed it for this reason) it threw a hissy fit because MSDTC had not been clustered. Search as I might, I have not yet found a way to do so under Windows Server 2012 R2. I have found , but these instructions don’t align with 2012 R2 (at least, not in a way that allows me to successfully cluster MSDTC). Plus,  that I have found for SQL Server Failover Cluster installation suggest that a third “network device” - shared network storage (a SAN) - is required for the DB itself (and other functionality). I do not have this, and won’t be getting this. Most of my storage exists on the “heavy lifter” that was designed for all of the “primary” VMs. If that physical machine goes down, so does the storage. The secondary server does have enough resources for an AD-DC Server, an SQL server and a File Server, so it will handle the “secondary” failover versions of those VMs (clustered or not).  My final question involves file servers. If I cluster file servers between two VMs (one on my “heavy lifter” and another on my “backup”, how do I mirror the data between them? Clustering VMs only provides a single point of access on the network for a resource, it doesn’t exactly replicate data between the two - that is left to the services that serve up that data. I am unsure how I can ensure that file server data between two clustered file server VMs can be properly mirrored. Remember, I only have two devices to be used here - my primary machine and a backup secondary. There is no chance of me obtaining a SAN or any other type of network attached storage. What exists on the machines must act as the storage.  Thanks in advance for any suggestions. Show that one-sided limits always exist for a monotone function (on an interval) How to show that the spherical metric satisfies the triangle inequality? For $x,y\in \mathbb R^n$ define  $$d(x,y)={\|x-y\| \over \sqrt{1+\|x\|^2} \sqrt{1+\|y\|^2}}$$ Here $\|x\|$ is the euclidean norm of a vector. How to prove that $d$ (the spherical metric) is indeed a metric?     Progress so far:    $d(x,y)\ge 0$ is obvious. $d(x,y) =0 \iff \|x-y\|=0 \iff x=y$, so the positivity holds. $d(x,y) = d(y,x)$ is clear from the formula, so symmetry holds.    But I am having difficulties with the triangle inequality. Writing it out in coordinates leads to a complicated inequality with square roots all over the place in denominators. Is there a better way? What does // mean in a path? How do I force Windows to check for updates? Question about Angle-Preserving Operators This an exercise out of Spivak's "Calculus on Manifolds".  Edit:  There was a typo in the exercise as is noted below in the answers.  The statement has been edited to reflect this.  Given $x,y\in\mathbb{R}^{n}$, the angle between $x$ and $y$ is defined by  $$\angle(x,y) = \arccos\left(\frac{\langle x,y \rangle}{|x|\cdot |y|}\right),$$ where $\langle x,y \rangle$ denotes the standard Euclidean inner product.  A linear operator $T:\mathbb{R}^{n}\to\mathbb{R}^{n}$ is said to be angle-preserving if $\angle(T(x),T(y)) = \angle(x,y)$ for every $x,y\in\mathbb{R}^{n}$.  The exercise as stated:  Let $\{x_{1},\dots, x_{n}\}$ be a basis for $\mathbb{R}^{n}$.  Then suppose that $\lambda_{1}, \dots, \lambda_{n}\in \mathbb{R}$ are such that $Tx_{j} = \lambda_{j}x_{j}$ for each $j = 1,\dots, n$.  Then $T$ is angle-preserving only if (not if and only if!)$|\lambda_{i}| = |\lambda_{j}|$ for every $1\leq i\leq j\leq n$.  I'm having problems with the $(\Rightarrow)$ direction.  My best attempt (which seems to lead nowhere) is to suppose that $|\lambda_{j}|\neq |\lambda_{k}|$.  Then by assumption, \begin{align*} \angle(Tx_{j},Tx_{k}) &amp; = \arccos\left(\frac{\langle Tx_{j},Tx_{k} \rangle}{|Tx_{j}|\cdot |Tx_{k}|}\right)\\ &amp; = \arccos\left(\frac{\langle \lambda_{j}{x_{j}},\lambda_{k}{x_{k}} \rangle}{|\lambda_{j}{x_{j}}|\cdot |\lambda_{k}{x_{k}}|}\right)\\ &amp; = \arccos\left(\frac{\lambda_{j}\lambda_{k}\langle {x_{j}},{x_{k}} \rangle}{|\lambda_{j}|\cdot|\lambda_{k}|\cdot|{x_{j}}|\cdot |{x_{k}}|}\right)\\ &amp; = \arccos\left(\text{sign}(\lambda_{j})\text{sign}(\lambda_{k})\frac{\langle {x_{j}},{x_{k}} \rangle }{|{x_{j}}|\cdot |{x_{k}}|}\right)\\ \end{align*} may also be calculated as \begin{align*} \angle(Tx_{j},Tx_{k}) &amp; =  \angle(x_{j},x_{k})\\ &amp; = \arccos\left(\frac{\langle x_{j},x_{k} \rangle}{|x_{j}|\cdot |x_{k}|}\right). \end{align*}  Then since $\arccos$ is injective, I believe I can make the jump that $\text{sign}(\lambda_{j})\text{sign}(\lambda_{k}) = 1$, which does not resemble the conclusion that I should arrive at.  Note:  I wasn't sure what tag to put this under, so anyone who knows better please feel free to adjust.  Thanks for any help you can give. How to open and convert CHM documents? I have some documents that are in a .chm format. I wondered if there is a file format that can be easier to navigate, supported and of equal file size in Ubuntu?  If there is, I would like to start converting all those books and probably using them with less hassle on all my Ubuntu PCs and my Android phone. How to print original variable's name in Python after it was returned from a function? I have enum and use the variables like myEnum.SomeNameA, myEnum.SomeNameB, etc.  When I return one of these variables from a function, can I print their names (such as myEnum.SomeNameA) instead of the value they returned? Why does inductor current lag the applied voltage at its terminal by 90 degrees? I studied electromagnetism and I am currently working with Inductors.  I could not figure out the physical reason based on electromagnetics on why inductor current lags the applied voltage by 90 degrees?  Everywhere I find the Formula as the starting point of explanation which is partially satisfying.    Induced EMF =L di(t)/dt    From the above equation, I understood that when there is a change in current there will EMF induced in the coil terminals. But How this induced EMF makes the current to lag the supply voltage V(t) = Vm*sin(wt)? (Please don't just differentiate and say there is a lag, I am looking for a physical sense on why this happens)  Lets us consider the AC voltage is applied across the terminal at time t=0; At this time there is almost no current. From this transient state how the steady-state is reached where the current is delayed with respect to the voltage?  Can someone help me to figure out why the current lags the Supplied voltage by using electromagnetism, the motion of Charges or any other basic concepts? Can a single molecule have a temperature? I need to display math in my report, but is it possible to remove the vertical space around align*?  A little example is the following (where I just want the align* to have the same vertical space as a \\  \documentclass[10pt,danish,a4paper,oneside,fleqn]{report}  \usepackage[english]{babel} \usepackage{amsmath}  \begin{document}  ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss \begin{align*}   A{\cap}B\ &amp; =\ {\left\{{b,d,e}\right\}}{\;}{\cap}{\;}{\left\{{a,b,f,g}\right\}}   \\   \nonumber\ &amp; =\ {\left\{{b}\right\}} \end{align*} ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss \\ ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss  \end{document} "An error occurred when reviewing this item" On approving an edit, I just get this pop up since morning. At first I thought there might be some internet connection issue, but this is now the 3rd to 4th time I got the same error; also, the review is accepted because on refresh I can see my name with approved text beside, but it still throws this error.    I am on a Windows 7 machine, running Firefox 24 (Icognito/Private Mode)    Also, this happens only when edit(1) is written on an question/answer, I don't go to review queue and approve, these reviews were directly loaded from the notification beneath the question/answer.  Martijn Pieters reproduced the problem from the review queue three times; each time the improve option was picked, accepting the suggested edit but editing the post some more. The network console shows that posting to https://stackoverflow.com/review/task-reviewed fails, the server responds with a 404 error:  Request headers: POST /review/task-reviewed HTTP/1.1 Host: stackoverflow.com Connection: keep-alive Content-Length: 137 Accept: application/json, text/javascript, */*; q=0.01 Origin: http://stackoverflow.com X-Requested-With: XMLHttpRequest User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36 Content-Type: application/x-www-form-urlencoded DNT: 1 Referer: https://stackoverflow.com/review/suggested-edits/3575396 Accept-Encoding: gzip,deflate,sdch Accept-Language: en,en-US;q=0.8,nl;q=0.6,nb;q=0.4,no;q=0.2,de;q=0.2,fr;q=0.2 Cookie: &lt;redacted&gt;  POST data: taskTypeId=1&amp;reviewTaskId=3575396&amp;taskResultTypeId=5&amp;fkey=f8791a329b445b658876f4d3afe7961e&amp;postCommentId=null&amp;taskResultSubtypeFlags=null  Response headers: HTTP/1.1 404 Not Found Cache-Control: private Pragma: no-cache Content-Type: application/json X-Frame-Options: SAMEORIGIN Date: Fri, 13 Dec 2013 12:04:53 GMT Content-Length: 0   On the  itself, no record is made of the accept; instead the suggested edit is recorded as approved by 3 people not including Martijn Pieters. In this case the improve review arrived too late.  In , improve again resulted in the error, but the Community account is shown rejecting the edit. Drag and drop not working inside Nautilus on Ubuntu 17.10