Understanding the arguments in newtheorem e.g. \newtheorem{theorem}{Theorem}[section]

I would like to understand what the arguments following \newtheorem are e.g.:  \newtheorem{theorem}{Theorem}[section]   \newtheorem{lemma}[theorem]{Lemma}  \newtheorem{proposition}[theorem]{Proposition}  \newtheorem{corollary}[theorem]{Corollary}   I even see some of the arguments switched up in various places. Why is it that in the \newtheorem{theorem} we have the squarebrackets [] being in the 3rd argument instead of the second?  Or for example why is there both a {corollary} and {Corollary} as well as a [theorem] tag sandwiched between the two?  The same happens with the lemma and proposition new theorems, these however also have the square bracketed argument in the middle.  Why is all of this?  Thanks,  Brian


Does repulsive or opposite gravitational force exist?

According to Newton's third law of motion, every force have an equal and opposite reaction. So, using that law, is there a reaction of gravitational force that acts in the opposite direction and is repulsive? If you throw a ball towards the ground, it would bounce up to a certain height. This bounce happens in opposite direction and is repulsive, so is it a clue that repulsive gravitational force exists?


Should Roomba have customized rules for meta websites?

Roomba, i.e. the system that takes care of automatically deleting supposedly low quality questions, is used in both main sites and meta sites. However, in meta sites, the voting system is different: people may downvote questions when in disagreement with the standpoint presented in the questions, despite the questions be of interest. But Roomba automatically deletes downvoted questions (with a few more criteria). Should Roomba have customized rules for meta websites, since the voting system is different?    For example, we could remove the Roomba's criteria on downvotes. Example of useful meta questions that it would save:


Show that $x^2 + y^2 = 3$ has no rational points

Are there rational numbers such that $x^2 + y^2 = 3$ ?     If I want to find a rational paramterizatio of $x^2 + y^2 = 1$  could start with the point $(1,0)$ and find lines $\ell$ of slope $m \in \mathbb{Q}$ and the intersection points $[\ell] \cdot [circle] = 2 [pt] $.  However, if I use the circle $x^2 + y^2 = 2$ there's no rational point on the axes.  Instead we should use $(x,y) = (1,1)$.    In the case of $x^2 + y^2 = 3$ there's no obvious rational point that comes to mind.  I'm concerned there might be no rational point at all.  In integers we'd have $a^2 + b^2 = 3c^2$ with $a,b,c \in \mathbb{Z}$.  We'd have $c \equiv 0 \pmod 4$.  Then $a \equiv b \equiv 0 \pmod 4$.  This could lead to an infinite descent argument.      As a bonus could there exist a small rationqal $\epsilon > 0$ with $\epsilon \ll 1$ and $\epsilon \in \mathbb{Q}$ such that $x^2 + y^2 = 3 + \epsilon$ has a solution (and therefore infinitely many solutions)?


in Latex how to deal with @manual entry style (jabref)

I've a problem so far unresolved and I have not found so much to help me in the different forums I've been looking to. Luckily somebody will have an answer :) I have R software in my library .bib that I built under jabref and I want to cite the software in an article I'm writing with latex. my reference entry in jabref is:  @MANUAL{R2012,  title = {R: A Language and Environment for Statistical Computing. Version     2.15.1},  author = {{R Development Core Team}},   year = {2012},  organization = {R Foundation for Statistical Computing},  address = {Vienna, Austria},  note = {{ISBN} 3-900051-07-0},  url = {http://www.R-project.org}  }   when I try to cite R in my .tex file using \citep*{R2012}  (to get full author name) or just \citep{R2012} nothing happens. Does anyone know which mistake I can have done? Thanks in advance!


Prove the following triangle related inequality

Prove that $\dfrac32\leq \dfrac{a}{b+c}+\dfrac{b}{a+c}+\dfrac{c}{a+b} < 2.$ where $a$ ,$b$ ,$c$ are sides of Triangle   I tried using sine rule which makes up the the expression $\sum \dfrac{\sin{A}}{\sin{B}+\sin{C}}$. Now i dont how to find the range of $\sum \dfrac{\sin{A}}{\sin{B}+\sin{C}}$. Any ideas(hint) or solution would be really appreciated.


I am trying to understand what a p value is and what is its importance in statistics, from this example.  For $50$ specimens of alloy steel the rock hardness scale measured an average of $62$ with standard deviation $8$ he manufacturer claims that the alloy has average strength of $64$ at significance of $0.01$ can you refute this?  Well I did this problem and saw no at this level you cant refute it , I use the null being that the hardness was $64$ and the alternate that the hardness was less then $64$. From the data we observe a $z=-1.7677$ but the chart is $z=-2.33$ and so we cant refute null at this level.  But now I want to understand what the p value would be ,  I thought it was that the p-value is the probability of getting the observed value of the test or a value with even more evidence against the null if the null is actually true. So using that I just look on the z chart, the probability of seeing Z greater then $1.7677$ is $0.0384$, so is that the p value?


Hardware requirement for IOS compilation

My company is moving to IOS Apps development and we are looking for a MAC's pc to compile the apps.  Basically we will develop at Window workstation, then compile at MAC.    Is the Mac Book Pro i5 or Mac Mini i5 power enough the the apps compilation(will only run as workstation to compile the IOS apps)?  How about Running OSX at window 10 HyperV, is it support?  Thanks Louis


Does the offhand attack from Crossbow Expert get a Dex bonus?

The Crossbow Expert feat lets you use a Hand Crossbow in your offhand and take a shot when you attack with your main hand.  Most people I've seen, seem to think this will allow Dual Wielding Hand Crossbows. What I'm curious about is if you get dex mod to damage on the second shot. There are two lines of thought I've come up with on this.  Either it follows the TWF model, where you do not get the offhand weapon's modifier without an extra feat, or it follows the Monk's Bonus attack model, which grants the modifier.   I'm not sure which way to land on this.


Given $\lim\limits_{x \rightarrow x_0} \frac{f(x)-p(x)}{(x-x_0)^n} =0$ Show that $a_r= \frac{f^{(r)}(x_0)}{r!}$

Suppose that $f$ is $n$ times differentiable at $x_0$ and $p$ is a polynomial: $$p(x) = a_0 +a_1(x-x_0)+...+a_n(x-x_0)^n$$    of degree $\leq n$ such that    $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p(x)}{(x-x_0)^n} =0$$    Show that $a_r= \frac{f^{(r)}(x_0)}{r!}$ if $0 \leq r \leq n$, that is $p=T_n$, the $n^{th}$ Taylor polynomial of $f$ about $x_0$.   First,  $f^{(r)}(x_0)$, with  $0 \leq r \leq n$, does exist according to the hypothesis.  If n=1, let's check that $a_1 =\frac{f'(x_0)}{1!}=f'(x_0)$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p(x)}{(x-x_0)} =0$$   $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p(x)}{(x-x_0)} \cdot \lim\limits_{x \rightarrow x_0} (x-x_0)=0 \cdot \lim\limits_{x \rightarrow x_0} (x-x_0)$$   $$\lim\limits_{x \rightarrow x_0} f(x)-p(x) = 0$$ $$\lim\limits_{x \rightarrow x_0} f(x) = \lim\limits_{x \rightarrow x_0} p(x)$$ $$\lim\limits_{x \rightarrow x_0} f(x) = \lim\limits_{x \rightarrow x_0} [a_0 +a_1(x-x_0)]$$ Taking the limit with $f(x)$ and $p(x)$ continuous $$f(x_0) = a_0 +a_1(x_0-x_0)$$ $$f(x_0) = a_0$$ Finding $a_1$: $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p(x)}{(x-x_0)} =0$$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-a_0-a_1(x-x_0)}{(x-x_0)} =0$$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-f(x_0)}{x-x_0} =\lim\limits_{x \rightarrow x_0} \frac{a_1(x-x_0)}{x-x_0}$$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-f(x_0)}{x-x_0} =a_1 \cdot \lim\limits_{x \rightarrow x_0} \frac{(x-x_0)}{x-x_0}$$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-f(x_0)}{x-x_0} =a_1 \cdot \lim\limits_{x \rightarrow x_0} 1$$ $$\frac{f'(x_0)}{1!} =a_1 $$  Assumption $P_{r-1}$: $a_{r-1}= \frac{f^{(r-1)}(x_0)}{(r-1)!}$ to be true such that $$g_{r-1}=\lim\limits_{x \rightarrow x_0} \frac{f(x)-p_{r-1}(x)}{(x-x_0)^{r-1}} =0$$  Finding $a_r$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p_r(x)}{(x-x_0)^r} =0$$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p_{r-1}(x)-a_r(x-x_0)^r}{(x-x_0)^r} =0$$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p_{r-1}(x)}{(x-x_0)^r} = a_r \lim\limits_{x \rightarrow x_0} \frac{(x-x_0)^r}{(x-x_0)^r}$$ $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p_{r-1}(x)}{(x-x_0)^r} = a_r $$  Given $f(x) - p(x) = R(x)$ with $R(x)$ a polynomial of degree $r$, we have $R(x)=o((x-x_0)^r)$. Therefore as $x \rightarrow x_0$, $R(x) \rightarrow 0$.  Given $f(x) - p_{r-1} =R_{r-1}$ with $R_{r-1}(x)$ a polynomial of degree $r-1$, we have $ \lim\limits_{x \rightarrow x_0} R(x) = \lim\limits_{x \rightarrow x_0} R_{r-1}(x-x_0) = 0$  $$\lim\limits_{x \rightarrow x_0} \frac{f(x)-p(x)}{(x-x_0)^r} = a_r $$ $$ \lim\limits_{x \rightarrow x_0} \frac{[f(x)-p(x)]^{(r-1)}}{[(x-x_0)^r]^{(r-1)}} = a_r $$ $$ \frac{1}{r!} \lim\limits_{x \rightarrow x_0}  \frac{ f^{(r-1)}(x)-p^{(r-1)}(x) } {x-x_0} = a_r $$ $$ \frac{1}{r!} \lim\limits_{x \rightarrow x_0}    \frac{ f^{(r-1)}(x)-f^{(r-1)}(x_0) } {x-x_0} = a_r $$ $$ \frac{1}{r!} \cdot f^{(r)}(x_0) = a_r $$  I understood that you are supposed to apply L'hospital rule and do the $(r-1)^{th}$ derivative, but I unsure of the correctness of argumentations of the last 5 lines above (or if it is correct, what would the justifications be?)  leading to the end  result.  $$ \frac{f^{(r)}(x_0)}{r!}=a_r$$  ?


Who is the copyright holder of Stack Overflow user-contributed content?

I understand that user contributed content is licensed under cc-wiki but Creative Commons work still requires a copyright holder. So who actually owns Stack Overflow's user contributed content? Stack Overflow or the individual users who contributed the content?  If it's the individual users, then   isn't Stack Overflow breaking the terms of cc-wiki since they are using the content for a commercial purpose? (they generate advertising revenue from user generated content) could a user demand that all his/her contributions be removed from the website? What would happen in the case of content which had been heavily edited by many different users?   If it is Stack Overflow who owns the content then does that mean people using Stack Overflow user contributed content on other websites should, under the terms of cc-wiki, attribute Stack Overflow and not the individual users who wrote the content?  Does Stack Overflow have a Terms and Conditions stating their IP rights with regard to the content they contribute?


/var/log/syslog owned by syslog:adm and permission denied with truncating it

$ sudo > syslog  -bash: syslog: Permission denied  $ ls -la syslog  -rw-r----- 1 syslog adm 11673034092 2016-09-01 16:55 syslog   What's going on here?


How to show that if $G$ is union of three proper subgroups, then there is an epimorphism from $G$ to the Klein 4-group?

I'm going through Grove's "Algebra." I'm having trouble with this one:  "If $G$ is the union of three proper subgroups, then there is an epimorphism from $G$ to the Klein 4-group."  I think the subgroups should in some sense correspond to the non-identity elements in the Klein 4-group.


What is the best way in Python to list all the possible coordinates in a game space?

To learn Python, I'm working on a game. I've hit a puzzle that may have multiple solutions (recursion? reduce? comprehension?), so I want to know what is the best way (e.g. most "Pythonic", best-performing, readable, etc.). Can you help a newbie learn cool stuff? The puzzle is to get a list of cartesian coordinates with which to refer to the spaces in the game board--but I want my solution to work for arbitrary number of dimensions (not just 2D chess, but also 3D chess, etc.) Here's what I've got, and I'm wondering if there are better ways: def cartc(dimensions):     """Returns an object that generates a unique tuple of integers (cartesian coordinates) for each spot          in the dimensions.        Args:         dimensions: An arbitrarily long sequence range objects. Each range object represents one             dimension of the space      Returns:         an iterable object that generates tuples of integers: e.g. (1, 1)                      cartc( [range(3), range(2)] ) generates (0, 0), (0, 1), (1, 0), (1, 1), (2, 0), and (2, 1)                  """          # Generate sets of coordinates by joining lists     tally = [[]]     for dim in reversed( dimensions ):         tally = [ [coord] + partial for coord in dim for partial in tally ]          # Convert to tuples     for coords in tally:         yield tuple( coords )


What is the difference between sudo X and running X as root?

My question is asking regarding a specific observation that I would like to understand.   I just tried to install the package rJava in R and failed even though I prefaced the installation as suggested  with:  sudo R CMD javareconf   Then I came across :     Using sudo and running as root are not exactly the same thing. –  Jon7   Desparate as I was I tried it:  sudo su R CMD javareconf   And to my surprise I suddenly could install that package.    Sorry for the lenghty introduction but I wanted to give you a context to prevent answers like . The question does not aim at specifically the described observation - rather at those "things" in general on Ubuntu.  My question is: How could this be possible? What is the difference between sudo X and runnding X as root?


"I am on the street" or "I am in the street"?

says     "IN" tells us the noun is in an enclosed space (surround or closed   off on all sides). Basically, when something is inside something.      "AT" tells us that the following noun is located at a specific   point or location. It shows an exact position.      "ON" tells us that the following noun is located on a surface. Use on when   one thing is attached to or touching something.   But, what about:  "I am in the street" (so, the street is considered as an enclosed space, maybe, the sentence would mean I am in the middle of the street, not on a pavement)? or   "I am on the street" (so, the street is considered as a surface, the sentence would mean I am standing on it, not under the ground)?  What are the differences?


How to update whatsapp with new apple ID

I need someone to help me  I got this iphone5 a months ago from my cousin and I already have my own appleID and also my iCloud, and I could download the apps and everything but now when I got a notice to update whatsapp it requires the old password :/ is the only solution to delete whatsapp or is there anything else I could do? P.S my cousin doesn't know the password  Thank you


How do I shoot a panorama with a Nikon D5200?

I recently bought a Nikon D5200 and I was wondering how to shoot in panorama mode. I seem to find every other mode but panorama. Do I just need to pan the camera and take multiple pictures and stitch them together later? Or does the camera have a panorama mode built in?


Are the Book of Shadow or Genie's Vessel granted by Warlock features considered as magic items?

Basically the title. If a Warlock fights by wielding their Book of Shadow or Genie Vessel in one hand as a spell focus and keeps the other one empty to meet the requirement of somatic component, they will eventually end up in situations where they are forced to use the book or vessel as an improvised weapon (like when an enemy closed the distance or when the Warlock needs to perform an Opportunity Attack). So the question is, would hitting someone with the spine of the book of shadow or their oil lamp of a Genie Vessel be considered using an improvised weapon with magical properties? For the Vessel, It is a tiny object, but not specifically written as "a magical tiny object" even if the previous sentence mention that the patron has imbued magical powers with it. The Warlock can do lots of wacky stuff with it like sleeping in it or dragging others into it to rest, but it almost seems like its the power of the Class Feature using the item in question as the medium in which the feature's power (and thus your Patron's power) is expressed, and not the power of the Item proper.  Genie's Vessel ; 1st-level Genie feature ; Your patron gifts you a magical vessel that grants you a measure of the genie's power. The vessel is a Tiny object, and you can use it as a spellcasting focus for your warlock spells. You decide what the object is, or you can determine what it is randomly by rolling on the Genie's Vessel table.  The book of shadow is even more vague; it is only stated to be a grimoire, and nothing else about it's materalistic properties are mentioned or explained further other than that if its lost or destroyed you can resummon it. How durable is it, anyway? This also opens some icky boxes like "Would anti-magic fields suppress their magical properties or destroy them outright?" and something like "If the Genie's Vessel is indeed a magic item and using it as an improvised weapon can pierce resistance, the Genie Warlock has access to a magical weapon that is basically the equivalent of a +0 but magical dagger at LV1" etc. I am aware that some similar questions have been asked, like "Does attacking with an improvised weapon using a magic item count as a magical attack?" and "Are punches with Gauntlets of Ogre Strength magical, improvised weapon attacks?"; but the main issue here is that both the book of shadow and the vessel's status as a separate magical item seems to be a bit unclear. They look very much like tag-alongs to complete a feature's ... uh... feautre. PS: Before someone says that using it as an improvised weapon is a poor choice of tactics, keep in mind that Genie Warlocks gain extra damage from the "Genie's Wrath" Feature equal to their proficiency bonus. Compared to wielding a regular dagger with the damage of 1d4 + dex + pb, using the Genie's Vessel as an improvised weapon of 1d4 + str + pb isn't that bad; and depending on how the DM would rule it could be counted as magical and be able to pierce resistances.


What is the norm of this bounded linear functional?

Let $a$, $b$ be two arbitrary but fixed real numbers such that $a < b$, let $C[a,b]$ denote the normed space of all continuous real (or complex) valued functions defined on $[a,b]$ with the maximum norm, and let $f$ be the functional defined on $C[a,b]$ as $$f(x):= \int_{a}^{b} x(t) x_0(t) dt $$ for all $x$ in $C[a,b]$, where $x_0$ is a fixed element of $C[a,b]$.   Now $f$ is evidently linear and bounded. How to compute the norm of $f$? What is this norm?   And what is the norm of the bounded linear functional $g$ defined as follows: $$g(x):= \int_{a}^{(a+b)/2} x(t) \cdot dt - \int_{(a+b)/2}^{b} x(t) \cdot dt$$ for all $x$ in $C[a,b]$?


Change default email application - iPadOS

When I type on Notes.app, it is useful to have clickable email links as follows:    Whenever I click this link, it wants to take me to Mail.app, I don’t have it installed so it shows this message:    I want to use Gmail.app to open these email links, is it possible to change the default app to Gmail?


Downloading Media Creation Tool in Ubuntu

I don't have any device with Windows 10 installer and I need to download media creation tool. I entered  of Microsoft, It shows me only ISO file to download. I searched for media creation tool in Google ( Maybe Microsoft has subpage for downloading it. ) but all results are from . I can't trust these web sites ( Maybe they will download media creation tool that install patched / edited Windows ( Not original ). ). Is there a way to download it from original source? I tried ISO file so much but it is not working on my computer. ISO file is not booting but when I directly write Windows to my USB Stick with media creation tools, it works. I'm not asking how to create a Windows 10 bootable USB, I'm asking for how to download media creation tool, I need it.


I have few questions regarding the Reputation thing. According to the site, reputation is the sign of trust.  I have noticed that I highly trust the answers given by high rep users moreso than the low rep users.  Even though I didn't understand fully sometimes what their answer was, but I am 100% sure that whatever he has written is right.  Now consider this case; suppose I have 40K rep and I usually answer the c++ or java questions.  Now I started answering questions of python or linux for which I am a newbie. Although I have 40k rep up till now, but for python questions I will be like a newbie since I have just started that. It happened with me that I used the high rep answer and it was wrong. I only relaized it later. Then I saw on the summary page that he is new to this area  Now when I give the answer for python question then its quality will be lower than other person with 5k rep who is regularly using python.  There is chance the OP uses the answer of 40k user by just looking at the rep, now that may contain some hidden problems, although the other community members can point that out but there are chances.  I was thinking is there any way we can give an indication along with rep that 40k rep is in c++ or java, but for python he is new.


I just don't know what the heck is that... So I have a Debian with apache2 on it. Got php 5.6.14 and firebird 2.5 superserver. I store my fdb file in /var/www/db , all php files are in /var/www/html. Localhost works, executes php and connects to db with no problem. However all my cyrillic strings in db come up as diamond question marks �  My html charset is utf-8; Default db charset is 'NONE'; When I connect to db using  ibase_connect, I give as a parameter charset 'NONE' (Tried UTF-8, ISO8859_5, WIN1251 and many other)  Just tried Flamerobin. It shows that strings as empty fields (not 'none', but empty)  Can you give any solutions, what it can be?


I am trying to render smoke in cycles, but the relevant blender  is designed for Bender Internal. I have everything set up except for the material.  I imagine you would set up the material nodes something like this:    But the problem is that there is no Voxel Data texture node, ans I am not sure what kind of shader should be used.  Is smoke in Cycles simply not supported yet? Or do I need to go about this a different way?   Reference:


I just started playing Dark Souls 2 without playing the first one.  Since I don't see any sell option in any merchant: Can I sell my old-unused-equipment for souls? If I cannot sell it, does it have any value to be keep until later?


Why would `sudo cp src dst` ignore no clobber rule in /etc?

My global preferences, alias cp='cp -iv', is ignored by sudo while using zsh.  I'm setting up a new system, and I'm trying out zsh for my user account. The root user still has bash. In /etc I have:  /etc/bash.bashrc /etc/zsh/zshenv   Both of these have the above alias, alias cp='cp -iv'.   In the user's directories, neither of these contains the commands in the /etc global configs.   ~/.zshenv /root/.bashrc    If I switch to the root user su - and try to clobber a file with copy, I get the correct prompt, cp: overwrite 'fruits/apple.txt?'. The same for the home user. However, if I sudo the copy command for the home user while in zsh, the file is overwritten! Using bash, I've not experienced this problem before, so I don't have a clue where else to look.


What are these tags related to on the Newest Questions page?

On the right, there is a widget that lists "Related Tags" (left − SO April 2013, right − MSE May 2014):         What are they related to? There isn't even a question selected. Are they related to the whole displayed list?  This can be seen on every SE site.


What does it mean to say that C was compiled in C?

I've seen stuff like this written... C was written in C, or ABAP was written in ABAP..  I've even seen  saying that this is one of the criteria to sort languages into true programming languages.  I'd like someone to explain to me what this means.  Thanks in advance.  EDIT:Changed title from: "C was made using C" to "C was compiled using C".


Did Voldemort kill half-bloods too during the FWW?

Or was it only Muggles and Muggle-borns? I'm writing a story and I need a little bit of help.


USB tethering from Ubuntu to Android via USB

I have an Ubuntu 12.10 system on my PC and an Android 4.1 system on my Galaxy Nexus. Now I would like to share the Internet connection of my PC via USB with my Phone. I have been searching with Google a lot, but I only found answers how you can share the Internet connection of the Phone with the PC, but I want it the other way around.


I want to run a system command from inside my application. It's suppose to run a command on a remote server using SSH. But that's not really the point. The point is that I don't know how to run any kind of command from the app. I asked in the mail list and they referred me to build a QML extension using C++. But I don't know C++ and it seems that I have to learn so much only to run a simple command.  In Python (as in PHP) it's easy to run a system command. Is there any other way of doing it in my Touch app, or is there someone that could help me even more? Or perhaps have a better solution to my problem?


Access remote services as if local using single SSH connection

Is it possible to create a single SSH tunnel to address a remote host like it was sitting on the local system, eg. type the following pseudo-examples locally and achieve the desired effect:   Copy databases: mysqldump remote | mysql local or mysqldump local | mysql remote Append text to remote files: echo blah >> remote:file.txt Change remote files: sed ... remote:file.txt Execute remote commands: apk add blah   If a single connection is not possible, what is the most convenient way to achieve these things?


Calculate the sum of the double series: $$\sum_{m=1}^\infty \sum_{n=1}^\infty \frac{m^2n}{3^m(n3^m+m3^n)}$$


Show that matrix under addition is isomorphic with the group of complex numbers under addition

Question. Let $M = \left\{ \begin{bmatrix} a & b \\ -b & a \end{bmatrix} \,\middle\vert\,  a, b \in \mathbb R \right\}$.  Show that $(M,+)$ and $(\mathbb C,+)$ are isomorphic.  Show that $(M^{*},*)$ and $(\mathbb C^{*},*)$ are isomorphic.    (Here, $M^{*}$ is defined as excluding the zero-element) I understand that there exists an isomorphism $\phi:M \rightarrow\mathbb C$ defined by $\begin{bmatrix} \alpha & \beta \\ -\beta & \alpha \end{bmatrix}\mapsto \alpha+i\beta$, ie. I can show that $\phi(M_{1}+M_{2}) = \phi(M_{1})+\phi(M_{2})$ and $\phi(M_{1}*M_{2}) = \phi(M_{1})*\phi(M_{2})$. However, I'm unsure how to go about the two subquestions seperately.


Redirect from URL with parameters to SEO friendly URL in .htaccess

I have category page with this structure  example.com/Category.php?Category_Id=10&Category_Title=some-text   i want to write htaccess rules to redirect from   example.com/Category.php?Category_Id=10&Category_Title=some-text   to this  example.com/Category/10/some-text   is there any way to force htaccess to do it. i want when i visit the  example.com/Category.php?Category_Id=10&Category_Title=some-text   the Category page automatically redirect to   example.com/Category/10/some-text   i use this htaccess code but it not redirect page to seo friendly url  Options -Multiviews RewriteEngine On RewriteBase / RewriteCond %{HTTP_HOST} !^exmaple\.com$ RewriteRule ^(.*) http://exmaple.com/$1 [R=301,L]   how can i do it?


I know that we can have a $U(1)$ bundle over the base manifold like $S^2$. For example, we can choose the fibre $U(1)=S^1$ over $S^2$ as the $S^3$ Hopf fibration. I know that we can have a $SU(2)$ bundle over the base manifold like $S^4$. For example, we can choose the fibre $SU(2)=S^3$ over $S^4$ as the $S^7$ Hopf fibration. Correct me if I was wrong! Now, can we have any nontrivial $SU(2)$ bundles over a flat Euclidean $\mathbb{R}^d$ or Minkowski $\mathbb{R}^{d,1}$ space?? If so, could you give some examples? If not, could you give me a proof? (or at least sketch your arguments to convince me?)


What is the significance of the second derivative of a function?

Basically, I just want to know the significance of the 2nd derivative of a function, or what does it tell us.


How to stack two things, up and down, in an equal size in the math summation $\sum$?

How to stack two things, up and down, in an equal size in the summation $\sum$? Here are my failed attempts: 1. $$ \sum_{ \overset{A \in \{1,3,5,...\}  ,}{B \in \{2,4,6,...\} }} $$   2. $$ \sum_{ \underset{B \in \{2,4,6,...\} }{A \in \{1,3,5,...\}  ,}} $$   The {A \in {1,3,5,...}  ,} and {B \in {2,4,6,...} } should be in the equal and good looking manners. Please advice. Many thanks!


I see this symbol all the time and my book has yet to clarify what it means. None of the man pages or web searches clarify this either. At first I believed it to be a I/O symbol, but that never works when I try to play with it.  For example, in the patch Man and Info documents, it say     You can also specify where to read the patch from with the '-i   PATCHFILE' or '--input=PATCHFILE' option. If you do not specify   PATCHFILE, or if PATCHFILE is '-', 'path' reads the patch (that is,   the 'diff' output) from the standard input.   When ever I see the '-' symbol, it is almost followed (at some point) by some mention of standard input.   What am I missing here? Does this symbol reference standard input? What does '-' mean in the context of Bash?


Can I add a status icon for thunderbolt ethernet to the menu bar? (Mavericks)

As the title suggests, I'm using a mac book pro with os x 10.9.2 and I connect to the network through the ethernet adapter thunderbolt.  Is there a way to get a reference icon in the menu bar, as is the case for the wifi?  I'd prefer not to use applications such as iStatsMenu or similar ..


How to call a function if the function's file name is known and is a string?

I am scanning a directory for new python scripts. I expect each script file to have an arbitrary function report(). Say, the following files were found in my directory: ['file1.py', 'file2.py']. So "file1.py" should contain:  def report():     print('I am just a script.')   I need to call report() function for each one of them. How to do it?


A friend of mine is going to fly from Beijing to Toronto, but he'll stop over in Chicago for 7 hours. Does he need the US visa?


Merging firstname/last name into one field

I am entertaining the notion of a single field for name entry on our scheduling web app. I think this is an excellent case for a "forgiving format" to make it easy to enter their names quickly. I would label it and possibly put additional placeholder text guiding the user. Like this:    It's important to catch first and last name correctly because it gets saved in our contact database that we provide to our users. However, people could enter "Joe De Maggio" or "Dr. Chopra" or "Ms Sally Ann Mc Dumont". The possibilities are many.  Is this choice wise? Is the engineering worth the UX? Does anyone know a plugin that tackles this?


Does the scientific community consider the Loschmidt paradox resolved? If so what is the resolution?

Does the scientific community consider the  resolved? If so what is the resolution?  I have never seen dissipation explained, although what I have seen a lot is descriptions of dissipation (i.e. more detailed pathways/mechanisms for specific systems). Typically one introduces axioms of dissipation for example:  entropy $S(t_1) \geq S(t_0) \Leftrightarrow t_1 \geq t_0$ (most often in words)  These axioms (based on overwhelming evidence/observations) are sadly often considered proofs. I have no problem with useful axioms (and I most certainly believe they are true), but I wonder if it can be proven in terms of other (deeper and already present) axioms. I.e. is the axiom really independent? or is it a corollary from deeper axioms from say logic (but not necessarily that deep).  (my opinion is that a proof would need as axioms some suitable definition of time (based on connection between microscopic and macroscopic degrees of freedom))


What are the connected components of the real general linear group?

What are the connected components of $GL(n,\mathbb{R})$? I think there are two, corresponding to those of positive and negative determinant. But I don’t know how to prove that each one of them is connected.  Could you help? Thanks!


For proving the quadratic reciprocity, Gauss sums are very useful. However this seems an ad-hoc construction. Is this useful in a wider context? What are some other uses for Gauss sums?


wireshark problem while loading or opening wireshark qt.qpa.plugin

av_acharya@AnoxBotox:/$ wireshark qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in "path/to/plugins" This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.   sudo apt-get install --reinstall qt5-default Reading package lists... Done Building dependency tree        Reading state information... Done The following NEW packages will be installed:   qt5-default 0 upgraded, 1 newly installed, 0 to remove and 23 not upgraded. Need to get 0 B/24.4 kB of archives. After this operation, 170 kB of additional disk space will be used. Selecting previously unselected package qt5-default:amd64. (Reading database ... 241279 files and directories currently installed.) Preparing to unpack .../qt5-default_5.12.8+dfsg-0ubuntu1_amd64.deb ... Unpacking qt5-default:amd64 (5.12.8+dfsg-0ubuntu1) ...


Transit through London for US to India roundtrip

I have US L1 visa on passport that expires in Jan2014. I am planning to visit India in Jan2014-Feb2014. I have my US H1 visa for which I will go to stamping in India. Now, can I travel through London? The visa I have on passport is for L1 that expires in Jan2014, but my return date is in Feb2014 and I will be coming back on H1. I will be transiting through London between 6th Jan 2014 to 12th Jan 2014.   I read few other similar questions but unable to judge whether to have valid US visa for return date or while passing through london.


I have looked at some of the other forum post and they don't answer my question.  I have been using various Linux Live CDs for some time now, but I've just bought a 16Gb usb 3 stick for a Linux (Ubuntu) install and I wanted some advice  I wanted to know wether I'm better of with a Persistent Live usb or a Full install   In an ideal world I would like all the features of a full install but portability will be important for me, I will be using it on two very different machines and will want to use it on friends and family's laptops for repairs. Is there a way I can have a full install with the portability of a Live USB install?  And thank you in advance  P.s this is my first post so sorry if I've done anything wrong!  EDIT: this question is not a duplicate of the one listed as it asks about the comparison of the methods, not HOW to do them.


Why does the "LaTeX" logo have random capitalisation and letter height?

Why does LaTex have random capitalisation and letter height? Context: So I'm sure this is a rather random question which probably has a really obvious answer, but since I couldn't find it on this site I've decided that I might as well ask it to quench my curiosity: Question I often see the LaTeX logo written like the following image:  And I've always wondered why this is so? I've also seen it on this site as LaTeX. So:  Why does this site have a capital T and X? Does "TeX" represent something? Why do other sites have a raised A and lowered E? Does that represent anything?  Post - Note Again, apologies if this is an obvious question and has already been asked. If so, please don't downvote, just give me the link to where it has been asked or tell me the answer. Also, I wasn't really sure what to tag this question - "syntax"?


"Root" tags to organize larger sites with multiple categories

This is more of a "research problem" wrt UI's, but I think the tagging system needs a better UI overall.  Assuming that tags are supposed to categorize content (akin to sticking labels on things), a good tag system should make things easy to find.  But what you have is a kind of soup of things with labels on them.  You can search through the soup pretty easily.  Tags as they are, are kind of browsable through the search box UI. You've made it work, kinda.  But I don't think browsing on SE sites, especially those that house multiple topics, is as pleasant or clear as it could be.  What would be clearer?  I'm not exactly sure, but that's why I said this was a bit of a "research" problem.  The  regarding music.se is to combine all music interest into a single site, instead tons of smaller, less significant mini-sites.  To have violins, guitars, piano, music-theory and song-writing all on one site, you have to be able to organize things quite well.  I think the tagging system is sufficient.  Even with the 5 tag limit on each post, tagging is enough to cleanly divide the site, but its the front end UI to the tagging system that needs work.  Tags replace folders, and tags are arguably better because they don't force you to repeat structure.  For example, if using "folders" on SO:  Folders are bad example 1:  C++     operators     variables   You'd also have  C#     operators     variables   Or you could do  Folders are bad example 2:  operators     C++     C# variables     C++     C#   with repeated structure. With tags you essentially get "virtual folders"  Tags are good example 1:  C++  & operators C++  & variables C#   & operators C#   & variables   Can't do that with folders, and the beauty is, you can VIEW tags as folders.  So perhaps a user-configurable navigation structure that presents a tree view.  Root Tags  You select your "root" tags, for example, piano and guitar (or these can be hard-set by the site manually OR tags can become root tags when there is excess of 10,000 or so posts in them)  piano     technique     fingering  guitar     phrasing     strings     effects   So, with piano as one of your/the site's "root tags", the site takes on an artificial folder structure on top of the tag system.  Each post must contain a "root" tag, which roughly defines the site's scope (kind of like how MSO has "discussion" "support" etc).  This helps you define the scope of the site, and in addition it gives you the opportunity to create a hierachical browse mode, instead of tag-soup mode.  So one possible UI for a front page that has root tags might be  (Where piano, guitar and song are defined as root tags, and the topics shown below are popular tags that also have that root tag.)


Code block is not visible after using HTML  (or "-" before text if you prefer)

When answering/asking a question if you want to achieve   a black dot before the text,   you can either use "-" before your text or use:

some text

   So far so good, but I just noticed that if I use this black dotted text, any code blocks will not be seen after.  Here I have two screenshots to better illustrate the problem:    With "-" before the text:      And now without:    As you probably noticed, the code blocks are only seen if the "-" char does not exist.  Why is this happening? Is this a bug or something that I miss regarding this answer/question editor?


I have a family member who speaks Romanian but not English, French or any other world language. If she flies alone, how can she pass through the control points (immigration, customs) at the airport?  Would it work if she brings a sheet with translations of the common questions and answers? Do airports (CDG in particular) have interpreters available for most languages? Is there any arrival card (for France) she will need to fill?


Enabling SAML SSO: where is the "Use Single Sign-On" permission?

We've set up Single Sign on with SAML. Our IdP is OneLogin and using their link, we are able to connect.  We now want to disable password login for some users in Salesforce.  points me towards a "Use Single Sign On" or "Is Single Sign On Enabled" permission (depending on the age of the document) on the user profile, however I cannot find this permission. Does anyone know where to find it?


More precisely, given the ring homomorphism $\phi:\Bbb{R}[x,y]\to\Bbb{R}^\Bbb{R}$, with  $\phi(f(x,y)):\Bbb{R}\to\Bbb{R},\,\,\phi(f(x,y))(\theta)=f(\cos(\theta),\sin(\theta))$, where $\Bbb{R}[x,y]$ is the ring of formal polynomials in two variables on $\Bbb{R}$, I wish to show that $\mathrm{ker}(\phi)=(1-x^2-y^2)$. So far the best I can do is to show that $\mathrm{ker}(\phi)\supseteq(1-x^2-y^2)$, which is pretty trivial anyway. In particular, I'm interested in a proof of this statement from the perspective of algebraic geometry.


What is XeTeX exactly and why should I use it?

I have been using LaTeX for five years now and have been using PDFLaTeX ever since. I find it hard to monitor the progress of LaTeX development. Recently there is a lot of talk about XeTeX. What is that exactly? Does it make sense to switch to it?


How to set up shader materials with main node Principal BSDF

I have issue with exporting shaders on blender model. I need to export model with shaders in GLTF . The problem is that shader materials are not exporting - only the main color of Principal BSDF node. I've got an idea from google answers, that shader materials can be exported in GLTF only if the main node will be Pricipal BSDF, that is going directly though material output node. But now i have shader mixer, that goes though material output. Is there any way to change order and plug all shaders to Principal BSDF, that will be plugged directly in material output?


Integration by Parts is the 'reverse product rule'. Is there a quotient equivalent?

As the title suggests. I do understand that the quotient rule is pretty much the product rule combined with the chain rule, but regardless is there a methodical way of computing such integrals?


Why prefer the 18-55mm and 55-250mm lenses vs 18-200mm?

There seems to be a preference for to have the    18 mm - 55 mm 55 mm - 250 mm   lenses, but no mention of why they're better than a single 18-200mm. Could someone please explain why the two separate are better than the one combined, and if anyone has quantified this difference?  (I'm curious about Canon in particular.)


Why isn't $e^{2\pi xi}=1$ true for all $x$?

We know that $$e^{\pi i}+1=0$$and $$e^{\pi i}=-1$$  So$$(e^{\pi i})^2=(-1)^2$$$$e^{2\pi i}=1$$  Because $1$ is the multiplicative identity,$$(e^{2\pi i})^x=1^x$$$$e^{2\pi xi} =1$$should also hold true.  But we also know that $$e^{xi}=\cos(x)+i\sin(x)$$and so$$e^{2\pi xi}=\cos(2\pi x)+i\sin(2\pi x)$$which does not equal 1 for all values of $x$.  Now I realize I probably didn't break math, so I must be making an invalid assumption. What is wrong with my reasoning?


Every not empty finite subset of a totally ordered set has a maximum and minimum

Theorem Let be $(X,\le)$ a totally ordered set: then for any not empty finite subset $A$ of $X$ there exist the maximum  element and minimum element. proof. Let be $(X,\le)$ a totally ordered set and we prove by induction that any not empty finite subset $A$ of $X$ has a minimum element. Since $X$ is a totally ordered set, previously we observe that any its subset $Y$ (finite or infinite) is a chain. Obviously any subset $A$ of one element $a$ has trivially a minimum. So we suppose that any subset of $n$ elements has a minimum element and then  we consider a subset $A$ of $n+1$ elements: since $A$ is finite there exists a bijection $\phi$ from $A$ onto some natural number $m$, that is the successor of $n$, and so we can organize the elements of $A$  in a finite succession, that is $A=\{a_1,...,a_{n+1}\}$. Now we consider the subset $B=\{a_h\in A:h\le n\}$: obviously $X$ is a subset of $A$ that has $n$ element and so it has a minimum element $b$; so since $A=B\cup\{a_{n+1}\}$ and since $A$ is a chain (remember what before we observed), it must be or $a_{n+1}\le b$ or $b<a_{n+1}$ and so for the transitivity property of the order relation $\le$ in any case $A$ has a minimum element. So now we only have to prove that any not empty finite subset $A$ of $X$ has a maximum element. So we consider the inverse relation $\preccurlyeq$ defined as $x\preccurlyeq y\iff y\le x$ for any $x,y\in X$: clearly $\preccurlyeq$ is a total order, since indeed $\le$ is a total order, and any minimum in $\preccurlyeq$ is a maximum in $\le$ and so since any not empty finite subset $A$ has a minimum in $\preccurlyeq$ it follows that any not empty finite subset in $\le$ has a maximum element. So we concluded the proof.  Is my proof correct? If not how prove the theorem? Could someone help me, please?


If an entire function maps a rectangle to another rectangle, then it is linear

Suppose $f$ is entire and, for some rectangle $R$, $f(R)$ is a rectangle. Prove $f$ is linear.    I have tried some ways,   Let the first rectangle be $R_1$ and the second one be $R_2$. $ f : R_1 \longmapsto R_2 $  And, I construct one linear map $h_1 : R_1 \longmapsto S_1$, $S_1$ is a unit square. Similarly a $h_2 : R_2 \longmapsto S_2$.  At the beginning, I want to say there should be a identical map $I : S_1 \longmapsto S_2$, but I failed. Second, I want to use extended Liouville's Theorem to say there is a linear mapping between $S_1$, $S_2$, it doesn't satisfy the requirement of the theorem.   Since the map, say $h$, satisfying $|h(z)| \leq |z| + \sqrt{2} $.  What should I try? How to construct a linear map between $S_1$ and $S_2$ ?


How to Create SQLite Database Outside an Android Application?

So far, tutorials I have found create databases and tables inside Android applications.  Usually, (in other languages) I created a database and tables, then simply used them in an application.  Can I do it in an Android application?  I do not want to create them in an application, however, I want to create a database and tables beforehand I use them in the application.  For example, can I access to SQLite of an application (in a device) from the terminal?  How can I do?  Thank you!


Sharing the same `ssh-agent` among multiple login sessions

Is there a convenient way to ensure that all logins from a given user (ie me) use the same ssh-agent?  I hacked out a script to make this work most of the time, but I suspected all along that there was some way to do it that I had just missed.  Additionally, since that time there have been amazing advances in computing technology, like for example this website. So the goal here is that  whenever I log in to the box, regardless of whether it's via SSH, or in a graphical session started from gdm/kdm/etc, or at a console:  if my username does not currently have an ssh-agent running, one is started, the environment variables exported, and ssh-add called. otherwise, the existing agent's coordinates are exported in the login session's environment variables.    This facility is especially valuable when the box in question is used as a relay point when sshing into a third box.  In this case it avoids having to type in the private key's passphrase every time you ssh in and then want to, for example, do git push or something. The script given below does this mostly reliably, although it botched recently when X crashed and I then started another graphical session.  There might have been other screwiness going on in that instance. Here's my bad-is-good script.  I source this from my .bashrc. # ssh-agent-procure.bash # v0.6.4 # ensures that all shells sourcing this file in profile/rc scripts use the same ssh-agent. # copyright me, now; licensed under the DWTFYWT license.  mkdir -p "$HOME/etc/ssh";  function ssh-procure-launch-agent {     eval `ssh-agent -s -a ~/etc/ssh/ssh-agent-socket`;     ssh-add; }  if [ ! $SSH_AGENT_PID ]; then   if [ -e ~/etc/ssh/ssh-agent-socket ] ; then     SSH_AGENT_PID=`ps -fC ssh-agent |grep 'etc/ssh/ssh-agent-socket' |sed -r 's/^\S+\s+(\S+).*$/\1/'`;      if [[ $SSH_AGENT_PID =~ [0-9]+ ]]; then       # in this case the agent has already been launched and we are just attaching to it.        ##++  It should check that this pid is actually active & belongs to an ssh instance       export SSH_AGENT_PID;       SSH_AUTH_SOCK=~/etc/ssh/ssh-agent-socket; export SSH_AUTH_SOCK;     else       # in this case there is no agent running, so the socket file is left over from a graceless agent termination.       rm ~/etc/ssh/ssh-agent-socket;       ssh-procure-launch-agent;     fi;   else     ssh-procure-launch-agent;   fi; fi;  Please tell me there's a better way to do this.  Also please don't nitpick the inconsistencies/gaffes ( eg putting var stuff in etc ); I wrote this a while ago and have since learned many things.


Ka always zeros in MTL file, reflectance and translucency coeffs also missing

I'm exporting a model from Blender into OBJ and MTL files. When I look at the generated MTL file I see that the "Ka" component of the material is all zeros, and there is no information about the reflectance and translucency of the material either. Have a look:  newmtl BigWall Ns 15.000000 Ka 0.000000 0.000000 0.000000 Kd 1.000000 1.000000 1.000000 Ks 1.000000 1.000000 1.000000 Ni 1.000000 d 1.000000 illum 2   Here the Kd and Ks colours have the correct value (all white) but the Ka is set to black.  I've seen that the illum statement can provide some hints on whether reflectance is used, but it does not give me any coefficients.  So how can I make Blender export the ambient coefficient or an ambient colour to this file? And from where can I take the coefficients of reflectance and translucency?  Thanks.  BTW: I found these similar questions here but they were not answered, I hope to run with better luck:       EDIT: Blender's documentation  claims to be able to export ambient colour and shading settings like transparency.


How to add a dot after the section number?

I wonder is there any way to change the format of section numbering from 1.1 to 1.1. ? I know this is trivial, but I really need to add one more dot after the section number. Does anybody know how to do that?  Thanks a lot


KNN - Distance measure and interpretation

KNN can uses different measure to calculate distance: Euclidean, Manhattan, Hemming and Minkowski. Text available over the net doesn't discuss pros and cons for each of distance measure and when to use which (in details). Can an expert answer this?


Mysterious, Undesired Outline Around Black Illustrator Shapes

Why do black shapes end up having a faint outline around them? Will there be any consequences to this when I print? Is there any way to avoid this? Thanks.


Schengen Visa Refused twice what could i have done wrong?

I recieved spanish schengen visas in the past and most recently i was refused a visa twice in a row which to me was shocking. I provided all the documents requested by the consulate i will provide a list of documents i provide and i cannot figure out what was missing or what went wrong. I would appreciate any clarity on this matter.  Passport and application correclty filled out Verifiable flight bookings  Parents bank statement  Parents home contract in spain where i will be staying  My assests in home country Car Title  Marriage certificate Daughters birth certificate   What was missing what could have caused the refusals?


Inverse of an invertible triangular matrix (either upper or lower) is triangular of the same kind

How can we prove that the inverse of an upper (lower) triangular matrix is upper (lower) triangular?


How can I prove the following inequality.

If n is a positive integer, prove that $\dfrac{1}{2\sqrt{n+1}} < \dfrac{1\cdot3\cdot5\ldots(2n-1)}{2\cdot4\cdot6\ldots2n}$


If we have $$ f(z) = \sum_{n=0}^\infty a_n z^n, $$ How do we show that $$ \frac{1}{2 \pi} \int_0^{2 \pi} |f(re^{i \theta})|^2 \, d\theta = \sum_{n=0}^\infty |a_n|^2 r^{2n}? $$ I can show $ \leq $ by using the triangle inequality but I don't know how to show equality. Your help is much appreciated.


Plots to illustrate results of linear mixed effect model

I've been analysing some data using linear mixed effect modelling in R. I'm planning to make a poster with the results and I was just wondering if anyone experienced with mixed effect models could suggest which plots to use in illustrating the results of the model. I was thinking about residual plots, plot of fitted values vs original values, etc.   I know this will very much depend on my data but I was just trying to get a feel for the best way to illustrate results of linear mixed effect models. I'm using the nlme package in R.  Thanks


How can I get root-like permissions so I can download stuff from the software center?

When downloading an application from the terminal it said I couldn't download it because I wasn't root, and when I got to search for the specific software in the Ubuntu software center it doesn't even come up as a search result. I need to get/download ttf-mscorefonts and preload please.


Lone astronaut works with yesterday's self to repair space station

I think this is a short story, I read it 30-40 years ago. A lone astronaut on a space station wakes to find someone bashing on his bedroom door. It is himself from tomorrow, offering to help him repair the space station, which is a two-person job. As the space station travels through the wormhole (I think that term is used), it becomes crowded with other time versions of himself. Does anyone remember the title and/or author?


How to take up the remaining space from the viewport height?

I have this full width div that takes up around 30% of my view port height (not sure of the exact height) and I was wondering if there is a property that will allow me to take up the remaining height of the view port in another div so that both divs take up 100 percent of my view port height?


Is there an equivalent program to the windows explorer for Ubuntu?

and   These above are not the same as this question and I am struggling to find a definitive answer.  I am trying to ascertain whether or not there is an equivalent program to the windows explorer.exe for Ubuntu. I have worked for years on windows and just cannot get used to the mac/linux file explorer.  In windows explorer the current position of where you are is represented in a nice expandable tree on the left with the contents of the current folder in the main window on the right.  Eg:   In Ubuntu's "file" and Mac's "Finder" there is no such thing (as far as i can tell), merely a single representation of your current position in the file structure.  EG:   In the windows explorer screen shot (please ignore the somewhat garish aesthetics) you can clearly see all the folders in c:/ on the left hand side and the contents (folders and files) on the right.  In the ubuntu screen shot, i am in "/home/john/Documents/test folder" yet the "Documents" folder on the left is still closed. Meaning if you are alien (for whatever reason, a new project or what ever) to the fileset you are working on it becomes extremely time consuming as you have to head somewhat blindly into different folders... but if you are generally a busy person with far too much work to do the very last thing i want to do is waste any time on what should be the simplest IT task... navigating a file system.  Is there any way I can achieve a windows explorer style file navigation?  NB  I am not looking to replicate anything else of windows file explorer.


How do I order an IEnumerable such that a special item is always at the bottom?

I have an IEnumerable<string> being passed to me which has the following items:   HP Canon  Lexmark Samsung  Other   Now what I am trying to achieve is order the items alphabetically but I want to keep the other item last. I have gone ahead and used OrderBy(i => i)  which lists the items as follows:   Canon HP Lexmark Other Samsung   The desired result I want is    Canon HP Lexmark Samsung Other   I have tried using .OrderBy(i => i != "Other").ThenBy(i => i) but this puts Other item right at the top.   Can someone tell me how to achieve this please.


I'm trying to plot something using atan in pgfplots, but it always results in hundreds of errors.  I'm using an example I found here:  \documentclass{article} \usepackage{pgfplots} \begin{document}  \pgfplotsset{compat=1.9} \begin{tikzpicture} \begin{axis}[      width=160pt,compat=1.5.1,grid style={ultra thin},every axis plot post/.append style={thick},      x tick label style={font=\tiny},y tick label style={font=\tiny},      scale only axis,grid=major,axis lines=middle,      xlabel={$x$},      ylabel={$y$},      xmin=-200,      xmax=200,      domain=-200:210,      ymin=-5.5,      ymax=5.5,      xtick={-150,-100,...,150},      ytick={-5, -4,...,5},      restrict y to domain=-20:20,      legend style={at={(0.5,-0.05)},anchor=north,nodes={right}},  ]  \addplot[mark=none,color=blue, samples=500]{rad(atan(x))};  \addlegendentry{$y = \tan^{-1}x $};  \end{axis} \end{tikzpicture}  \end{document}   The errors are:  ! Undefined control sequence. <recently read> \pgfmath@multiply@thousand   l.23 ...ne,color=blue, samples=500]{rad(atan(x))};  The control sequence at the end of the top line of your error message was never \def'ed. If you have misspelled it (e.g., `\hobx'), type `I' and the correct spelling (e.g., `I\hbox'). Otherwise just continue, and I'll forget about whatever was undefined.  ! Undefined control sequence. \pgfmath@basic@atan@ ... pt \pgfmath@table@lookup                                                    {\pgfmath@x }{pgfmath@atan... l.23 ...ne,color=blue, samples=500]{rad(atan(x))};  The control sequence at the end of the top line of your error message was never \def'ed. If you have misspelled it (e.g., `\hobx'), type `I' and the correct spelling (e.g., `I\hbox'). Otherwise just continue, and I'll forget about whatever was undefined.  ! Missing number, treated as zero. <to be read again>                     } l.23 ...ne,color=blue, samples=500]{rad(atan(x))};   And it goes on and on. Over hundred errors and then it stops compiling with no result at all. What am I doing wrong here?


How do I resolve this installation error?

I am getting the following error while installing Drush with composer require drush/drush.     Using version ^8.1 for drush/drush   ./composer.json has been updated   Loading composer repositories with package information   Updating dependencies (including require-dev)   Your requirements could not be resolved to an installable set of packages.            Problem 1   - drush/drush 8.1.0 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.1 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.2 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.3 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.4 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.5 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.6 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.7 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.8 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - drush/drush 8.1.9 conflicts with drupal/drupal [No version set (parsed as 1.0.0)].   - Conclusion: don't install drush/drush 8.1.12   - Conclusion: don't install drush/drush 8.1.11   - Conclusion: don't install drush/drush 8.1.10   - Conclusion: don't install drush/drush 8.x-dev   - Installation request for drupal/drupal [No version set (parsed as 1.0.0)] -> satisfiable by drupal/drupal [No version set (parsed as 1.0.0)].   - Conclusion: remove phpdocumentor/reflection-docblock 3.1.1   - Installation request for drush/drush ^8.1 -> satisfiable by drush/drush [8.1.0, 8.1.1, 8.1.10, 8.1.11, 8.1.12, 8.1.2, 8.1.3,   8.1.4, 8.1.5, 8.1.6, 8.1.7, 8.1.8, 8.1.9, 8.8.x-dev, 8.x-dev].   - Conclusion: don't install phpdocumentor/reflection-docblock 3.1.1   - drush/drush 8.8.x-dev requires phpdocumentor/reflection-docblock ^2.0 -> satisfiable by phpdocumentor/reflection-docblock [2.0.0,   2.0.0a1, 2.0.0a2, 2.0.0a3, 2.0.1, 2.0.2, 2.0.3, 2.0.4, 2.0.5].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.0, 3.1.1].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.0a1, 3.1.1].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.0a2, 3.1.1].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.0a3, 3.1.1].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.1, 3.1.1].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.2, 3.1.1].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.3, 3.1.1].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.4, 3.1.1].   - Can only install one of: phpdocumentor/reflection-docblock [2.0.5, 3.1.1].   - Installation request for phpdocumentor/reflection-docblock (locked at 3.1.1) -> satisfiable by phpdocumentor/reflection-docblock [3.1.1].      Installation failed, reverting ./composer.json to its original   content.


Getting an insanely large amount of traffic from Germany

Within the past couple of weeks, there has been an incredibly large number of visits to my company's site with German IP addresses. My company is based in the U.S. and deals primarily with other American companies, so I know this traffic must be from some kind of bot/crawlers. All of the traffic is coming from servers "Server Block" or "Hetzner Online AG" (a lot coming from the IP 88.198.39.182). I've tried to find some more information than this but haven't had any luck. Anyone else experience this or can give me some more insight as to where these are coming from?


Unresolved external symbol on operators overload

I have a class and when i tried to compile it on visual studio it gave me 4 external symbols unresolved on 4 operator overloads. It gives me LNK2019 error on the 4 operator overloads listed below on the .h and .cpp files. Seems like the linker is not linking the functions correctly or something else is happening.  .h  template <class T> class Ecuatie {     //some private things public:     //other function definitions     Ecuatie<int> friend operator+(int x, Ecuatie<int> &e);     Ecuatie<int> friend operator+(Ecuatie<int> &e, int x);     Ecuatie<int> friend operator-(int x, Ecuatie<int> &e);     Ecuatie<int> friend operator-(Ecuatie<int> &e, int x); };   .cpp  template <class T> Ecuatie<int> operator+(Ecuatie<int> &e, int x) {     string aux = "+";     aux += to_string(x);     str += "+" + aux;     v.push_back(aux);     return (*this); }  template <class T> Ecuatie<int> operator+(int x, Ecuatie<int> &e) {     string aux = "";     aux += to_string(x);     str = aux + "+" + str;     if (v.size()) {         v[0] = "+" + v[0];     }     v.push_back("0");     for (int i = v.size() - 1; i >= 0; i--) {         v[i + 1] = v[i];     }     v[0] = aux;     return (*this); }  template <class T> Ecuatie<int> operator-(Ecuatie<int> &e, int x) {     string aux = "-";     aux += to_string(x);     v.push_back(aux);     str += "-" + aux;     return (*this); }  template <class T> Ecuatie<int> operator-(int x, Ecuatie<int> &e) {     string aux = "-";     aux += to_string(x);     str = aux + "-" + str;     if (v.size()) {         v[0] = "-" + v[0];     }     v.push_back("0");     for (int i = v.size() - 1; i >= 0; i--) {         v[i + 1] = v[i];     }     v[0] = aux;     return (*this); }   Any ideas why and more important how to fix these errors?


The Who/Whom examples in Strunk and White's Elements of Grammar

From Strunk & White, Elements of Grammar, 3rd Ed., p.11: "When who introduces a subordinate clause, its case depends on its function in that clause."    They then give four examples without explaining which, if any, is incorrect.  They give no further comment on the four examples which are:   "Virgil Soames is the candidate whom we think will win."  "Virgil Soames is the candidate who we think will win." "Virgil Soames is the candidate whom we hope to elect." "Virgil Soames is the candidate who we hope to elect."    It seems to me that 2 and 3 are correct (since we think he will win, and we hope to elect him).   Is this what Strunk and White are driving at, or am I missing something more complicated?  Specifically I would like to reconcile number 2 with an explanation in A Grammar Book for You and I ... Ooops Me by C. Edward Good.   It says (p.138) to use whom for a clause that already has a subject.  It looks to me like number 2 above has a subject, we, and should therefore, according to Good, take whom as the relative pronoun.   Which is correct, Good or S&W?


How to select all data from these two tables?

I need to select all from these two tables. Is it possible?


Determinant of matrix with rectangular matrices on its diagonal

Let matrix $M$ be \begin{align*} M= \begin{pmatrix} A_1 & 0 & 0 & \cdots & 0 \\ 0 & A_2 & 0 & \cdots & 0 \\ \vdots \\ 0 & 0  & 0 & \cdots & A_n \end{pmatrix} \end{align*} where $A_1, A_2, ..., A_n$ are rectangular matrices (could be of different types). What is the formula of calculating determinant of such matrix?


Could a member of my family and I play a game in Steam at the same time?

I have bought a game, but a member of my family couldn't because of $$ and I was thinking if I can do this:    Add his/her computer to the list of family share of steam to let him/her see and play my games (I already have done that).   Block steam (and possibly the game too) in my computer with the firewall to go offline.   Disconnect internet (if 2 doesn't work).   Start the game in both computers (one online and one offline (the offline will be me)).    Before this, I could actually let him/her play my games when I don't play them, and going offline apparently don't block my games.  If I do this, do he/she could play it? (I don't care to go offline or lose achievements, but I care if I could get banned if I do this).  Also, he/she'll buy it, but meanwhile I was thinking if I can do this.  I have read  and apparently it can be done, but I want to know if this is risky.


Will a modern compiler such as GCC perform a tail case optimization in such cases?

Assume I have a function like this :  int recursivefunction (int n) {     if (n>10) return n; /* terminal case */     elseif (n>5) return n*recursivefunction(n-1); /* non tail call*/     else return recursivefunction(n-1); /* tail call   Will the third recursive call be optimized as a tail call ? If not why not ? We could replace this third return statement by an assembly code that clears the current function stack frame, except for local variables passed to the next call, and a goto to the adress of the function, this way no space on the stack is reserved.


Why treat complex scalar field and its complex conjugate as two different fields?

I am new to QFT, so I may have some of the terminology incorrect.  Many QFT books provide an example of deriving equations of motion for various free theories. One example is for a complex scalar field: $$\mathcal{L}_\text{compl scaclar}=(\partial_\mu\phi^*)(\partial^\mu\phi)-m^2\phi^*\phi.$$ The usual "trick" to obtaining the equations of motion is to treat $\phi$ and $\phi^*$ as separate fields. Even after this trick, authors choose to treat them as separate fields in their terminology. This is done sometimes before imposing second quantization on the commutation relations, so that $\phi$ is not (yet) a field of operators. (In particular, I am following the formulation of QFT )  What is the motivation for this method of treating the two fields as separate? I intuitively want to treat $\phi^*$ as simply the complex conjugate of $\phi,$ not as a separate field, and work exclusively with $\phi$.  Is it simply a shortcut to obtaining the equations of motion $$(\square +m^2)\phi=0\\ (\square + m^2)\phi^*=0~?$$  I also understand that one could write $\phi=\phi_1+i\phi_2$ where the two subscripted fields are real, ; perhaps this addresses my question in a way that I don't understand.


Does any subset of $[0,1]$ have a well-defined Lebesgue Measure? No.

New comer to measure theory!  I'm struggling to wrap my head around this concept...  Referring to Lebesgue Measures!   Could someone provide a concrete example of a set in the interval $[0,1]$ such that the probability of choosing a point in that set is not well defined?


While loop involving user input not behaving as expected

I am trying to create a program, that takes asks the user to enter a Contact name, and a contact number, and then stores that contact in my ArrayList entries. Once the user has entered the first contact, they are given the choice to add another contact to the array list, or to not add any more contacts, exiting the loop, and simple displaying all of the contacts stored in entries.  I am currently having trouble exiting my while loop, the first contact adds correctly to the array list, and then displays the "Add Another?" message, however from there it falls apart, if i type Y, the console simply just hangs with the cursor flashing, instead of asking for the next contacts name and number, and if i type N, it once again just hangs and does nothing, instead of exiting the loop and displaying the contents of  my ArrayList like intended.  Any help towards solving this issue would be much appreciated! I have a feeling it may be something to do with my loop, but can't for the life of me see what!  Thanks in advance!  while (addMore != false)     {         System.out.print("Contact name: ");         String name = sc.nextLine();         System.out.print("Contact Number: ");         String TelNo = sc.nextLine();          // add the user inputted contact to ArrayList entries.         entries.add(new TelEntry(name, TelNo));           System.out.print("Add Another?(Y/N): ");         if(sc.nextLine() == "N")         {             addMore = false;             break;         }          else if(sc.nextLine() !="Y" && sc.nextLine() !="N")         {             System.out.println("Please Select Y or N");         }          addMore = true;      }      // FOR LOOP TO PRINT ALL ENTRIES IN ARRAY     for(int i=0; i<entries.size(); i++)     {         System.out.println(entries.get(i));     }


How to return the smaller of an OR operator regex when both are present?

This regex:      import re     string = 'I am a long string with many regexes matching'     pattern = '.*(?:with|regexes)'     print(re.findall(pattern, string))   returns   ['I am a long string with many regexes']   How can I instead make it return:  ['I am a long string with']   i.e. when both the short and long version of the regex is present, return the shorter string.


How to tell contained component to reload data

I've been trying to understand the Lightning component event model, to see what would be the best way to do what I need to do.  I have a component that contains a component, like this:  <!-- parent component --> <aura:component>     <c:childComponent/> </aura:component>   The child component contains a data table that is populated via an init().  When I do something in the parent component that changes the data displayed in the child component, what is the best way to tell the child component to refresh the data displayed by the data table?


Setting the default value of a DateTime Property to DateTime.Now inside the System.ComponentModel Default Value Attrbute

Does any one know how I can specify the Default value for a DateTime property using the System.ComponentModel DefaultValue Attribute?  for example I try this:  [DefaultValue(typeof(DateTime),DateTime.Now.ToString("yyyy-MM-dd"))] public DateTime DateCreated { get; set; }   And it expects the value to be a constant expression.  This is in the context of using with ASP.NET Dynamic Data.  I do not want to scaffold the DateCreated column but simply supply the DateTime.Now if it is not present.  I am using the Entity Framework as my Data Layer  Cheers,  Andrew


First the van rolls, then later the van falls off the bridge. Why doesn't this kick wake up Arthur?  Related questions:


Is it possible to see all the unread messages for the StackExchange network even after one of the unread messages has been viewed? I've noticed that the unread message count in the upper-right corner (circled in red) disappears after clicking just one of the unread messages.


Segmentation fault on execution of a C program related to strings

I have the following code. I initialized 2 pointers, one at the beginning and another at the ending of a string. After every step, I increment the 1st pointer and decrement the second pointer. I copy the value of first pointer into the second if the value obtained by dereferencing 1st pointer is less than the value obtained by dereferencing 2nd pointer.  #include <stdio.h> #include <string.h>  int main() {    char *word="aacdbc";    char *p=word;    char *q=word+(strlen(word)-1);    printf("\n%s\n",word);    int i;    for(i=1;i<=strlen(word)-1;++i) {       if(*p<*q) {          *q=*p;       }       ++p;       --q;    }    printf("\n%s\n",word);    return 0; }   But the code shows a "Segmentation fault error". In which line did I make a mistake?


Word or idiom for someone holding (seemingly) contradictory views

I think some good words would be conflicted, or confused. As an example of context, think of someone who believes in freedom of speech, but, at the same time, they would support banning comedians who make jokes about certain issues that person cares about.


Getting insight into partitions of a table in Azure Synapse (similar to SQL Server)

I'm using  AKA Azure Synapse (which is different from serverless/on-demand Synapse that comes with Azure Synapse Analytics). And :  While the syntax of partitioning may be slightly different from SQL Server, the basic concepts are the same.   I have a table that receives ~33 million new rows per day. Column named version indicates the day on which that row arrived. E.g. all 33 million rows arriving on 2021-05-22 have same version value (2021-05-22). Currently it has ~300 million rows (9 days worth of data). Table has daily partitions.  Here is the order of things I did:  create table with 345 daily partitions (from 22-May-2021 to 30-Apr-2022). insert 9 days (33 million x 9 = ~300 million rows) worth of data into this table. I used INSERT INTO mytable SELECT * FROM some_other_table_with_300_million_rows) update statistics mytable  Question  Expectation: I have 9 partitions with ~33 million rows and 336 partitions with 0 rows. Reality: All partitions have equal amount of data.  When I run : SELECT      partition_id, index_id, partition_number, rows, data_compression_desc  FROM      sys.partitions  WHERE      object_id = OBJECT_ID('mytable')  I get this result: partition_id        index_id    partition_number    rows    data_compression_desc 72057597508452352   1           1                   868784  COLUMNSTORE 72057597508583424   1           2                   868784  COLUMNSTORE ...... 72057597553410048   1           344                 868784  COLUMNSTORE 72057597553541120   1           345                 868812  COLUMNSTORE  868784 * 345 = ~300 million  however: SELECT *  FROM sys.dm_pdw_nodes_db_partition_stats  WHERE object_id = OBJECT_ID('mytable')  returns no rows.  Originally posted here until I discovered dba community:


What is Ubuntu's equivalent of an exe file?

Sometimes I want to install a program when offline. But apt-get downloads as you install.  Is there a way to install a program, like you would install a .exe, on Ubuntu?


I have heard the expression intestinal fortitude to mean courage or endurance to achieve something. Is there a connotation for stubbornness in this expression?


Is it correct to say 'I wish some magic happens'?

Another read I come across in which a guy has written, "I wish you could see that young restless orphan who has no house to live in, none to get food from, whose pshychological centre has been damaged to the hilt. I wish you could see the pain of that abandoned girl on road who has set huge ambitions, but not priviliged enough to reach them, whose each tear drop brings earthquakes in the place on which it has fallen. I wish some magic happens and brings back all your lost senses and you start loving each and every human being going through hardships. Is this at all correct to say happens after wish as the author has written above? The writer is Indian. Not native.


How to turn off a particular hard disk in a multiple disk computer system to save power?

Explanation:  I have about 5 hard disks in my windows 7/8 machine. Since, the operating system is only installed in 1 disk, the rest 4 drives just consume power staying connected to the motherboard.   Now, those 4 disks are only used for data storage and backup purposes. So they are seldom used. In this case, is there any way to turnoff power to the hard-disks not being used? Or at least, is there a way to force the hard disks in lower power consumption state?  How to force them to stop drawing power while they are not being used most of the time? Are there any softwares to achieve this?


I am running a Dell laptop computer with a Windows 7 Professional operating system.  I have Google Chrome and Internet Explorer installed.  When I open Internet Explorer the home page I get is a website that says 'AVG Secure Search'.  I want to delete this.  How can I do so?  I had this problem once before, maybe six months ago, and was able to solve it myself after several hours of effort.  This time I cannot find a solution.  If I type 'remove AVG Secure Search' into Google I find a lot of websites describing this problem, but none offer a clear and effective solution.  Many of those websites are by AVG themselves, but their proposed solutions are not helpful to me.  For example,  says:  Step 1. Open Internet Explorer  Step 2. Click 'Tools' on the top menu, and then click on 'Manage Add-ons'.  Step 3. In the opened window, click on 'AVG Security Toolbar', and then click on 'Disable' at the bottom right corner.  However, on my computer AVG does not appear in the opened window.  The default open window is for 'Toolbars and Extensions', which has a small red circle with a red diagonal line in it, suggesting to me that something is disabled.  If I click on 'Search Providers' instead of 'Toolbars and Extensions', then 'AVG Secure Search' is listed.  If I click on 'AVG Secure Search' then a 'Remove' button appears in the lower right corner of the window, but this 'Remove' button is grayed out and I cannot click on it.   I have explored other websites purporting to provide assistance in removing AVG Secure Search, but these other websites often seem to recommend downloading and installing various applications with which I am not familiar.  Nor does 'AVG' appear anywhere in the listing under 'Programs and Featured' under the 'Control Panel'.  I have also checked other posts here on SuperUser that mention AVG, but have not found a post that provides clear instructions on how to remove AVG Secure Search.  Thank you for any advice.  If I locate a way to remove this search engine myself, I will post the solution here.  (I am using the AVG-antivirus tag, although as far as I know I do not have AVG antivirus software on my computer.  At least, I never knowingly installed it to the best of my recollection.)


I am new to use Linux, so sorry for this stupid question. I've try to have Full Ubuntu on my USB(it is 64GB), I've did it by this tutorial:  , but when it writes it is complete to restart PC and remove my USB with installation medium(I've got another USB stick, 4GB which I used with rufus to boot Ubuntu), so now I my PC I've got plugged only the 64GB with installed Ubuntu, but when I open Boot menu, only Windows boot option will show there. I will be very grateful for all the answers and have a nice day.


"A" or "an" in front of a number that can be read in two ways

Consider the following sentence.  We are selling ___ 1,800 sq ft office.   I would write an, because I say eighteen hundred. But someone else would say a, because they say one thousand eight hundred.   For 2,000 it's easier, because it's always two thousand.   For 2,100 it can again be twenty one hundred, or two thousand one hundred.   So what is grammatically correct, what do I write so that I don't confuse my readers?


Show that a group can not be expressed as union of two of its proper subgroups. I am not sure how to start.


VAR or VECM for a system of I(0) and I(1) variables?

I have 4 variables (time series). All the variables depend on each other. Two of them are non - stationary and the others are stationary . If I apply log transformation in the non-stationary variables, one of them will stationary after this, the other not. So in this case i would have 3 stationary variables (one of them in logs) and the other variable non - stationary. The goal is forecast all variables.   I selected the optimal lag length based on AIC. I test for Cointegration with all original variables using Johansen's test,   the output is "Trace test indicates 1 cointegration eqn(s) at the 0.05   level". How i should interpret it? Should I use VAR or VECM if the goal is forecast all variables? And how can   i build these models? Can you please give any good research?


How do I find out what my default terminal text editor is?

While reading the git introductory material, I read a piece that brought this question to mind.  How do I use the Terminal to find out what my Default Text Editor is?   Are there a General Commands that I can use to find this out?


Why Don't the Death Eaters Kill Harry Physically

We know that someone actually died while playing Quidditch. So why didn't anyone, such as Voldemort or Draco, just poke a quill in Harry's eye to kill him?


What is the advantage of using imaginary units for time in the Minkowski Space rather than regular euclidian space as Lorentz used?

I do understand that Lorentz transformations became as a rotation of coordinates as of a hyperbolic rotation. But what is its advantage over real vector? What is the new thing that it introduces and what problems does it fix or ease?


Why test -n returns true even when a variable is empty? What am I doing wrong?

according to the test(1) manpages:           -n STRING               the length of STRING is nonzero   so I expected this to run fine:  [ -n ${var} ] && echo "var is not empty"   I used this logic in a real case, a script like this:  [...] dne() {     echo DEBUG: wc -c: $(echo -n $peopkg |wc -c)     echo DEBUG: pdir: $pdir     echo "Error: ${package}: doesn't exist in local repos"     exit 1 }   # packages are listed as such:  # p/pname/package-version-release-distrelease... # pname is inconsistent, but it is guaranteed that the first word in package # (all to lowercase) will match at least one pname. # NOTE: package-[0-9]* matches package-32bit. *-32bit is a subpackage we want # to match later, but not when it's not already in pcase. # So that must be negated too  pfirst=${pcase%%-*} for pdir in ${p}/${pfirst}* do     # check if the glob matched anything at all     [ ${pdir} = "${p}/${pfirst}*" ] && dne      peopkg=$(find ${pdir} \         -name ${package}-[0-9]* \         ! -name *.delta.eopkg \         ! -name ${package}-32bit* |sort -rn |head -1)     echo DEBUG: in-loop peopkg: $peopkg     echo DEBUG: in-loop wc -c: $(echo -n $peopkg |wc -c)     echo DEBUG: in-loop test -n: $(test -n $peopkg && echo true || echo false)     #------------------------------------------------------------#     # break on ANY match. There's supposed to be only one anyway #     [ -n ${peopkg} ] && break # <--- [issue here]                #     #------------------------------------------------------------# done [ -z ${peopkg} ] && dne [...]   what matters here is that when I run this, I get these messages:  DEBUG: in-loop peopkg: DEBUG: in-loop wc -c: 0 DEBUG: in-loop test -n: true DEBUG: wc -c: 0 DEBUG: pdir: a/alsa-firmware Error: alsa-utils: doesn't exist in local repos   This makes zero sense to me.. DEBUG: pdir: a/alsa-firmware indicates that the loop exits always on the first iteration. Which can only happen if the glob pattern a/alsa* matched something AND peopkg was nonzero length.  PS: I'm trying to be POSIX compliant.


getopts in function that is called more than once in a script, getopts doesn't detect any opts after 1st function call

I have read the getopts man page and am still not sure about this use case.  getopts is not detecting any available options the second time a function is called in the same script.   As you can see from my debug echo outputs, all of the positional params $@ are present for both function calls.   In the second create_db function call, the getopts while loop is never entered, causing my variables TYPE and ENVIRON to not be set.   Any thoughts?   FUNCTION DEFINITION (create_db)  function create_db {   local TYPE SIZE ENVIRON   TYPE=''   SIZE=''   ENVIRON=''    print_usage() {     echo -e $"\nUsage: create_db -t {mysql|redis|rabbitmq|sftp|elasticsearch} -e <environment_name> -s <size_in_GB>"     echo "Required args: -t, -e"     echo "Optional args: -s"   }    echo "@: $@"   echo "0: $0"   echo "1: $1"   echo "2: $2"   echo "3: $3"   echo "4: $4"   echo "5: $5"   echo "6: $6"    # parse flags   while getopts 't:s:e:h' flag; do     echo "flag: $flag"     echo "opt: ${OPTARG}"     case "${flag}" in       t) TYPE="${OPTARG}" ;;       s) SIZE="${OPTARG}" ;;       e) ENVIRON="${OPTARG}" ;;       h) print_usage          exit 0 ;;       *) print_usage >&2          exit 1 ;;     esac   done   shift "$(( OPTIND - 1 ))"    echo "TYPE: ${TYPE}"   echo "ENVIRON: ${ENVIRON}"    ... DO WORK ...  }   CALLED SCRIPT (environment-setup-from-scratch.sh)  #!/bin/bash  # import functions from utils file . "${0%/*}/environment-setup-utils.sh"  ENVIRONMENT="${1}"  create_db -t "elasticsearch" -e "${ENVIRONMENT}" create_db -t "mysql" -e "${ENVIRONMENT}" create_db -t "redis" -e "${ENVIRONMENT}"    TERMINAL OUTPUT  $ ./environment-setup-from-scratch.sh  sandbox   @: -t elasticsearch -e sandbox 0: ./environment-setup-from-scratch.sh 1: -t 2: elasticsearch 3: -e 4: sandbox 5: 6: flag: t opt: elasticsearch flag: e opt: sandbox TYPE: elasticsearch ENVIRON: sandbox   @: -t mysql -e sandbox 0: ./environment-setup-from-scratch.sh 1: -t 2: mysql 3: -e 4: sandbox 5: 6: TYPE: ENVIRON:


I need a Regex that matches an email-adress, local@domain with following requirements:  Local-part can contain A-z, 0-9, dot, underscore and dash.  Domain can contain A-z, 0-9, dot and dash. The domain needs to contain at least one dot.   How do I make sure that: The domain can't start with or end with dot or dash. And that that the domain needs to contain at least one dot?  These are the two things that really cause me problems in trying to solve it.  Have tried the following:  Regex.IsMatch(email, @"(?:[^.-])([\w.-])@([\w.-])(?:[.-]$)");


When is the past perfect exactly needed?

I have never had this problem before. But after seeing some questions posted on ELU, I started to doubt. I have been through links1, pages of grammar books2, a lot of questions3 posted here and ELU. I now still can't seem to understand how the past perfect is exactly used. The references sometimes even contradict each other.  What I had understood so far was      The past perfect is not necessary if we are not 'going back' to the earlier past, and simply moving from one event to another.   but I then saw a lot of other 'rules' including      If the sequence is clear, the past perfect is not needed.   which is slightly different, less 'narrow' and can be applied in more situations than the first ruleA, and      The past perfect is optional only when talking about an action at a specific time.   This is confusing. Can anyone here clarify things out please?    A For example, for  Doing the survey [completed] -> Showing the result      We showed the result of the survey we did.      If the second rule is applied, the sentence above is fine (the sequence is clear), but not if the first rule since we are not moving from any event to the next and possibly even going back.    1  and   2 Practical English Usage (2005) by Michael Swan, Collins Cobuild Student's Grammar (1991). Upper-Intermediate Cutting Edge.  3 including , , ,  etc.


So far, I've unlocked one of the secret hats. I'm wondering what other secret hats are out there and how to earn them?


How can I style html the input file type using css, and also change the browse button, thanks


I'm writing something with the article class, and I'd like to have the table of contents pages numbered with roman numerals, and in addition and most importantly: to have the arabic numbers reset after the table of contents.  That's because I'm printing the document as I write, and the TOC will be ready only after the work is finish (and I don't want to change the page numbers). As it's a somewhat big article (~70 pages maybe) should I switch to a book class instead?


Does light really slow down when moving through a transparent medium?

I assume its speed doesn't change but the photons get absorbed and destructed by the materials' atoms and then they emit new photons. Is that true?


When I execute sudo apt-get install mysql php7 in my vmware, it goes well in the beginning, but in the end, it shows:  Unable to locate mysql php7   why would this situation happen?  Is it because I choose to get mysql and php service when I installed the system? Whether my system get the service or not?  在虚拟机中执行sudo apt-get install mysql php7时前面都是Done，最后一条是Unable to locate mysql 和php7 ，这是为什么呢？是因为我在安装的时候选择装了他们吗？那到底我的虚拟机里有没有mysql和php服务？   有人能帮帮我吗？


Draw a circle surrounded by numbers in TikZ

I want to draw the following figure using TikZ in LaTeX with the following requirements:   Numbers are evenly distributed around the circle. I can control the size of the circle. The size of the numbers can also be modified.   Edit: after following the comments, I get something that works.  \documentclass{beamer} \usepackage{tikz}  \begin{document} \begin{tikzpicture} \tikzstyle{every node}=[font=\large] \def\numofpoints{9} \def\labelpatt{{2,3,1,8,7,9,0,6,4,5}}  \node[circle,draw,minimum width=2cm] (bigc) {}; \foreach \x in {0,...,\numexpr\numofpoints-1\relax} { \node (l-\x) at (360/\numofpoints*\x+90:1.2cm)     {\pgfmathparse{\labelpatt[\x]}$\pgfmathresult$}; } \end{tikzpicture}  \end{document}


Unwanted and uneeded files generated every save

Just in case this is relevant: I've set up git on a Windows PC and every time I edit and save a change in a LaTex file (using Tex Studio) a new .tex file is created. See here:    'The_Cult' is the original LaTex file and the file below it is the new file.  Every time I make any edit and save one of these files is created.  This makes for a very messy work folder.  Any ideas why this is happening and how I can prevent it?


What's the practical difference between `command` and $(command)?

Both give the output of the command, so what is the semantic difference between the two? Some reading led me to suspect is that $(command) is Bash syntax, and the back quotes are integrated into Unix somehow; is there any truth to this?


I'm a bit confused about what Gstreamer does.   Does it come installed by default with Ubuntu ?  If so which version  is the default for 14.04?  Does it provide hardware accelerated video playback (decoding) ?   If so does it work with VA-API and VDPAU or is it an alternative to those?    Thanks for your help


A graph whose every odd cycle is a triangle is 4-colorable

As the title says, I have a simple finite graph whose every odd cycle is a triangle, and I want to show that $\chi (G)\leq 4$.  My idea was trying to use the fact that a graph is bipartite iff it contains no odd cycles. The general direction was: if we somehow "remove" the triangles, we get a 2-colorable graph, and then maybe somehow we can add them back without adding more that 2 colors needed...?


Let $x$ be an irrational number. Is the set $\ \{nx \mod 1: n \in \mathbb{N} \}\ $ dense in $[0,1]\ ?$ Obviously if $x$ were rational, the set would be finite and therefore would have no limit points, so my question follows naturally. Certainly, the set must have at least one limit point in $[0,1],\ $ e.g. see my answer . If the answer is no, how do we find the set of limit points in $[0,1]\ ?$ I had a look at , but I'm not sure it's the same question and I'm not very knowledgeable on continued fractions.


array of functions is printing wrong values (i think)

Please, can you explain me why the following lines of code, print letter E many times, instead of A,B,C,D,E ?  I don't understand what's going on. I've tried many things, but i get either errors, or undefined values.  var values = ['A','B','C','D','E']; var myfunctions = [];  for (var i = 0;i < values.length;i++){     var letter = values[i];     console.log(letter);     myfunctions.push( function(){         console.log(letter);     });  };  for (var j = 0;j < values.length;j++){     myfunctions[j](); };


Can you unwrap an image prepared for Uboot using mkimage?

I have an image that's currently wrapped in a uboot header from using the Uboot mkimage utility. I don't have the original of that image, so I want to take off the uboot header to turn the uimage back into a normal one. Is there any way this can be done?


From      The temperature of an ideal monatomic gas is a measure of the average kinetic energy of its atoms.    Now if I remove all the particles from the box shown below will the temperature be zero?


Best way to cache apt downloads on a LAN?

I have multiple Ubuntu machines at home and a pretty slow internet connection, and sometimes multiple machines need to be updated at once (especially during new Ubuntu releases.)  Is there a way where only one of my machines needs to download the packages, and the other machines can use the first machine to get the debs?  Does it involve setting up my own local mirror?  Or a proxy server?  Or can it be made simpler?


Was testing for midichlorians done covertly?

Various commentators have suggested that one of the reasons knowledge of the Jedi dies out so fast in Rogue One is that there were so few Jedi compared to the wider galactic population (I believe I've seen one post here that talks about a trillion people on Coruscant and around 100,000 Jedi in the galaxy). However it's also known in-universe that every child is tested for their midichlorian count. If true, then this suggests it was done covertly, otherwise the conversation would go something like:  "We're going to just check his Midichlorian count now, Mr Fett" "His what? You're doing what now? Hands off my Boba!"  [screaming]  So is there any indication whether testing was done overtly or covertly?


Rosewill RNX-N600UBE Connectivity issue on Ubuntu 17.04

I have installed Ubuntu 17.04 Zesty Zepus on my computer. I have been unable to connect to any wireless network with 17.04, whether from using the live USB during installation or after it has been installed. I experienced.no problems on 16.04. Although Ubuntu can see my network in 17.04, it cannot connect and it says "Disconnected".  EDIT:  I have followed Jeremy31's commands. The Internet seems to work now, and it works quite well. I had problems installing Steam and Chrome from .deb files with the Ubuntu Software program, so that's why I thought the Internet was malfunctioning. Gdebi fixed that issue.  I have entered my wireless-info.txt file to the link below which I received by entering the commands   wget -N -t 5 -T 10 https://github.com/UbuntuForums/wireless-info/raw/master/wireless-info && \ chmod +x wireless-info && \ ./wireless-info     Output of lsusb:  ID 148f:3572 Ralink Technology, Corp. RT3572 Wireless Adapter


Exporting QGIS contour attributes in DXF file?

I have a .tiff data file that generates contours in QGIS. I save it as .dxf. The contours don't have any attributes or data. That's bad, because I want to make a 3D landscape in Revit using the information.   How do a save/export the contour lines from QGIS so that they have a z-elevation attribute or at least some information?    I ticked the attributes box when extracting the contours, but the attributes doesn't show in the dxf.


What is this book or homebrew PDF covering how to stat offspring from different dragon parents that I remember?

I am new here, but I have read some of your discussions and I see that there is a glimmer of hope for me, for I cannot remember where I have seen information on this particular matter.  To rephrase: I would like to make a dragon that is an offspring of different coloured/typed dragons; say, one is chromatic and the other is metallic, or both are different chromatic kinds. I already know that I can apply a half-dragon template to a dragon. That is not what I am looking for.  A few years ago I have seen some published (electronically or in paper, not sure) source that contained information that I require. It might have been an unofficial .pdf (open licensed d20), or some sort of compendium with creatures and templates, but I remember it specifically addressed the issue and it even had a "fancy" name for such creatures.  Can anyone, please, drop me a hint? Pretty please!   [looks innocent as a baby kobold hugging a golden pony]


Expectation of Brownian Motion exit time

Let $(B_t)_{t \geq 0}$ be standard Brownian Motion with $B_0 = 0.$ Then $$ \mathbb E[\tau_{(a,b)}] = 0 $$ for all $a<b\in \mathbb R$ where $\tau_{a,b}$ denotes the first exit time of $(B_t)_t$, that is $\tau_{(a,b)} = \inf\{ t\geq 0:B_t \notin(a,b) \}$. How do I prove this? Ideas: I know that $B_t - B_s$ is normally distributed for all $s<t$  with mean $0$ and variance $t-s$. Thus, you could maybe use this information to prove the statement above.


I have some problem with resolution. My monitor resolution is 1920x1080.  At first when I installed ubuntu i had 800x600.. Now, after installing AMD driver, I only have 1600x1200 to choose like max resolution.  Why is that? What should I do?   Any answer will be helpful :)   P.S. My graphic card is Sapphire radeon HD 7850 (1Gb)


I wonder if any users have thoughts about using TeX for documents that need to be editable in the future. I doubt, for instance, that I could build documents even from a few years ago:   Packages change, develop new conflicts, etc. Supporting technologies change (e.g., BibLaTeX has replaced BibTeX in recent years)   For many applications, this is irrelevant. But I have some materials that I would like to update in the future. I've run into a few situations where I return to a document after a year or two, and have to spend half a day debugging the code because the packages have changed.  Is there anything that can be done to address this within TeX, or would I need to look at an alternate format?


How do you make the camera in blender cycles render everything so it looks like pixels? I want everything in my scene to look pixelly like this image I found:


Clean URLs - is it better to not have a colon or comma them?

I'm trying to create the following kind of URL:   www.example.com/state:ca/type:apartment,condo/price:0,20000/  or  www.example.com/state/ca/type/apartment/condo/price/0/20000  Is it better to not have ':' or ',' in the URL for SEO?