Goal :  My intention to design a utility that could access any numeric values( int,double,byte...) and produce the squares.  What i did:    delegate  void t<T> (T somevalues);  class program   {       static void Main()       {           Console.ReadKey(true);       }   }    class Utility   {       public static void Activities<T>(T[] SomeValues,t<T> transformer)       {          var qry = SomeValues.Select(p => transformer(p));         }        public static T Squaring<T>(T vals)       {         return vals * vals;       }   }   Error :    Try to specify explicit type  argument ( in LINQ query). Operator '*' cannot be applied to operands of type 'T' and 'T' ( in Squaring( ) ).   How can i derive constraint or change the code that can access any numerics(int,double,byte,..) and produce the square.

Can anyone tell me if there is a way with generics to limit a generic type argument T to only:   Int16 Int32 Int64 UInt16 UInt32 UInt64   I'm aware of the where keyword, but can't find an interface for only these types,  Something like:  static bool IntegerFunction<T>(T value) where T : INumeric


This book was published in the last decade, probably in the last five years. The story, if I remember correctly, takes place in the present - meaning when the book was published.  In one universe a few people survive in a timeline where the Cuban Missile crisis turned into full-scale war and the world was devastated. Somehow this universe 'bleeds' into our universe, just how I don't know.  I saw the book in a bookstore but I never read it.  Does anyone know what this is?

I read a novel when I was 12 or 13 (late 80's, early 90's) about two timelines combining on Earth.  It was a full length novel for adults that I swiped from my mom (she doesn't remember it at all.)  I've been trying to figure out what the title is for some time but my google-fu is unable to find the right search terms.    The book was published in the 80's or perhaps early 90's.  The story: It was set on Earth and featured two timelines running concurrently (in the 80's?)  Timeline 1:  The nuclear missile crisis had gone badly and a low level nuclear war had more or less destroyed the US, but small towns still survived but are slowly fading away.  Much of the story was about the scarcity of goods, and the protagonist in the main thread of the book started the story by finding a 6 pack of Coke buried in a ruined house.  Throughout the story people were finding things that had grown scarce (deer, bullets, human beings.)  One strange scene I recall involved mutant/radioactive sweet potatoes that had driven a man insane.  Eventually people in this timeline began having dreams of their lives in Timeline 2.  Some of the people were not having dreams, and it was eventually discovered that they had died in Timeline 2.    Timeline 2:  There is panic in a world recognizable as our 1980's as nuclear war draws near.  Since more and stronger missiles have been developed, the end of humanity is at hand.  Things start disappearing from that world as the war begins.  Timeline 2 was mostly seen as vignettes of panicked people running around.  Combination of Timelines: In a weird, incongruous, almost surely poorly written scene, Gaia (yes, Earth itself) is seen to be combining a dying timeline with a doomed timeline in order to save humanity.  At the end of the novel, kids from Timeline 2 are transported into Timeline 1 in order to repopulate.  The new kids drink all the Coke, in case you were wondering...  Any help finding the title would be welcome.  I recall enjoying the book a lot when I was a kid, but I suspect my mom traded it in at our local used book store because at some point it just disappeared.


We got an exercice about maximum and  minimum and there is a question about a sum. The goal is to find the general expression of the sum ( without the sigma ). And there is a kx^k form. We need to derive and I can understand why but I just can't find how you derive a sum.

I am trying to find a closed form solution for $\sum_{n\ge0} nx^n\text{, where }\lvert x \rvert<1$.  This solution makes sense to me:  $\sum_{n\ge0} x^n=(1-x)^{-1} \\ \frac{d}{d x} \sum_{n\ge0} x^n = \frac{d}{d x} (1-x)^{-1} \\ \sum_{n\ge0} nx^{n-1} = (1-x)^{-2} \\ x \sum_{n\ge0} n x^{n-1} = x(1-x)^{-2} \\ \sum_{n\ge0} nx^n=\frac x{(1-x)^2}$  However, a  I am reading used the following method:  $$\sum_{n\ge0}nx^n=\sum_{n\ge0}x\frac d{dx}x^n= x\frac d{dx}\sum\limits_{n\ge0}x^n=x\frac d{dx}\frac1{1-x}=\frac x{(1-x)^2}$$  This seems closely related to the solution I described above, but I am having difficulty understanding it.  Can someone explain the method being used here?


Can a virus or malware be bundled with a non executable download?  For example, when choosing 'save link as' on an .mp3 or a .pdf file, is it possible for the download to include more than just the file?  Or are virus/malware only distributable through .exe files...

I'm downloading an  file via a torrent, but my anti-virus detects something. Is it possible that the AVI file contains a virus?  It is quite weird since the torrent has many positive reviews.


I have a transcend 250GB hard drive which recently stopped working. It didn't sustain and physical damage that I am aware of, dropping, water ect... It won't even pop on the desktop, and isn't recognized with disk manager. I plugged it into a mac to test it and the exact same thing happened. I has using it an hour before, i turned the computer off and when i returned I booted the system to find the HDD clicking.  I heard this could be caused by the reader not finding the center point so it can't read any data also I heard this could be caused by the HDD not receiving enough power form the computer but I doubt this is the problem  My question is there any thing you guys know that will allow be to access the data once to  extract the data off it without using a service?

Upon bootup I have a drive that will spin up click and few times then spin down.  I have a spare drive (same model number) I attempted to transfer the heads from with no luck, HOWEVER, the heads from the bad drive work fine in the spare drive.  Swapping the PCB has no effect either.  So although it seems to spin up fine, could the problem be with the platter motor?


How can print 0, \pi/4, 3\pi/8, \pi/2 in the x-axis when plotting \sin(x) with gnuplot in the range [0, \pi/2].     Thank you,

How do I make the axis labels use multiples of \pi in PGFPlots?


When I run diskutil list there is 40 gb (free space), my question is that how can I merge it into my Container disk2? From the Disk Utility, I am not able to do this as the picture, I can not even find the (free space). I am very new to mac file system, please help me or point me in the right direction many thanks in advance.

Let me tell the story from the beginning: I installed Big Sur on an unsupported Mac using guidelines at Medium. In the guide it was stated that I should create a separate partition for Big Sur, and shouldn't install it on my current one. I had my SSD Called "Macintosh SSD" and later I created a partition named "Macintosh SSD Big Sur" of size 40GBs. After installation I wanted to clear the "Macintosh SSD" of size 80GBs(with old MacOS) and merge it with the new "Macintosh SSD Big Sur". This is what I initially had after formatting partition with the old MacOS  So, I used the command sudo diskutil apfs deleteContainer disk3 after which I had (free space) in /dev/disk1  I want to extend that 39.6GB partition which free space of 80,1GB but all the commands I googled do not work:(( Could you please guide me on what I should do now? Thank you in advance!


I watched a simple video tutorial on how to accomplish it, but nothing shows up on my project when I add the layer. Even if I try zoom to layer, the screen just shows blue. I'm not sure if it has something to do with my Excel, computer, or program. I really need help as I am new to QGIS. (I just posted this, but it won't let me comment to people under that question any more) I have a layer of google hybrid, but when I do add the new layer it is at the top and checked transparency and everything. Its just not accepting the data I entered into the excel spreadsheet is my guess to what the issue is.  I have the spreadsheet with the name, longitude, latitude. Save as CSV In QGIS go to Layer > Add layer > Add Delimited Text Layer Upload the CSV Excel file Add  Nothing shows even tho there is a line in the layers (bottom left) showing that "something" is there but if I choose "zoom to layer" it changes to a blue screen I have a Base layer Google Maps hybrid, and an area of interest on Georgia


Is the Canon T3 compatible with the Sigma 18-200mm F3.5-6.3 DC OS for Nikon? I'm looking around craigslist looking for a compatible lens.

Can we use the lenses from, say a Canon EOS 550D kit (Canon EF-S 18-55mm) with a Nikon DSLR D5000 for example) ? Also, is the reverse possible ?  I'm looking at interchangeability between recent DSLR lenses only, and not with older lenses. Also, for "average" lenses, and not ultra wide/ultra zoom.  The reason for this question is that I'm trying to decide between a Nikon D5000 and a Canon EOS 500D. I like the Nikon better, but Canon is more popular here amongst people I can interchange lenses with :)


Trying to get used to the whole windows 8 thing and don't appreciate the bipolarness, like a lot of people do.  I've seen a lot of people try to fix this by making Modern apps windowed (using ModernMix or something), but how about doing the opposite -- making desktop apps modern apps?  Being able to close them and switch them with the same touch gestures.  That's the main thing.  So someone asked this for Windows 8   It's been asked several times actually  Not sure if it's yet possible for Windows 8.1

Possible Duplicate:          In Windows 8, is there a way to make a normally desktop-only app run outside of the desktop? For normal apps that can be fullscreen, I'd rather switch through them using the metro switcher rather than switching to the desktop and then alt+tabbing.


Problems with ubuntu apt-get install -f  W: Some index files failed to download. They have been ignored, or old ones used instead. E: Problem executing scripts APT::Update::Post-Invoke-Success 'test -x /usr/bin/apt-show-versions || exit 0 ; apt-show-versions -i' E: Sub-process returned an error code E: Write error - write (28: No space left on device) E: IO Error saving source cache E: The package lists or status file could not be parsed or opened.   I tried mount back the tmp but it doesnts works Someone know How to fix it?  root@pipoca:/var/tmp# mount /tmp mount: can't find /tmp in /etc/fstab  root@pipoca:/var/tmp# free -m               total        used        free      shared  buff/cache   available Mem:           3008         868        1327          13         812        1964 Swap:           263           0         263  root@pipoca:/tmp# df -h Filesystem      Size  Used Avail Use% Mounted on udev            1.5G     0  1.5G   0% /dev tmpfs           301M  4.5M  297M   2% /run /dev/vda1        25G   25G     0 100% / tmpfs           1.5G  8.0K  1.5G   1% /dev/shm tmpfs           5.0M     0  5.0M   0% /run/lock tmpfs           1.5G     0  1.5G   0% /sys/fs/cgroup /dev/vda15      105M  3.6M  101M   4% /boot/efi tmpfs           301M     0  301M   0% /run/user/0        root@pipoca:/# dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d' | xargs sudo apt-get -y purge dpkg-query: no packages found matching linux-* Reading package lists... Error! E: Write error - write (28: No space left on device) E: IO Error saving source cache E: The package lists or status file could not be parsed or opened.   using   sudo apt autoremove sudo apt autoclean   I got   E: Write error - write (28: No space left on device) E: Write error - write (28: No space left on device)   using  root@pipoca:/# sudo journalctl --vacuum-time=2d Vacuuming done, freed 0B of archived journals on disk. root@pipoca:/# journalctl --vacuum-size=500M Vacuuming done, freed 0B of archived journals on disk.  root@pipoca:/# apt-get update Hit:1 http://mirrors.digitalocean.com/ubuntu xenial InRelease Hit:2 http://mirrors.digitalocean.com/ubuntu xenial-updates InRelease Hit:3 http://mirrors.digitalocean.com/ubuntu xenial-backports InRelease Hit:4 http://software.virtualmin.com/vm/6/gpl/apt virtualmin-xenial InRelease Hit:5 http://software.virtualmin.com/vm/6/gpl/apt virtualmin-universal InRelease Hit:6 http://security.ubuntu.com/ubuntu xenial-security InRelease Hit:7 https://packages.microsoft.com/ubuntu/16.04/prod xenial InRelease Hit:8 http://archive.ubuntu.com/ubuntu xenial InRelease not a reference at /usr/bin/apt-show-versions line 222. Reading package lists... Done E: Problem executing scripts APT::Update::Post-Invoke-Success 'test -x /usr/bin/apt-show-versions || exit 0 ; apt-show-versions -i' E: Sub-process returned an error code

I'm using Ubuntu 11.04 and I want to free up some space in my root directory, which is overloaded. I especially want to change the path used for installing applications (they are getting installed directly to the root drive).  Another consideration is that I'm working on a MySQL database server. The server is installed in the root directory itself, so I don't want to  risk losing any data.  Please give me some tips to help sort out this problem.


How can we prove by mathematical induction that $1,\sqrt{2}, \sqrt{3}, \sqrt{5},\ldots, \sqrt{p_n}$ ($p_n$ is the $n^{\rm th}$ prime number) are linearly independent over the rational numbers ?  $\underline{\text{base case (n=1)}}$: $1,\sqrt{2}$ are linearly independent over the field $\mathbb{Q}$ otherwise $a1+b\sqrt{2}=0 \Leftrightarrow \sqrt{2}=-\frac{a}{b}$ which is absurd.  Then I am stuck.

I need to find a way of proving that the square roots of a finite set    of different primes are linearly independent over the field of    rationals.    I've tried to solve the problem using elementary algebra  and also using the theory of field extensions, without success. To  prove linear independence of two primes is easy but then my problems  arise. I would be very thankful for an answer to this question.


Suppose $X_1,⋯,X_n$ are independent r.v.,  Let $S_n=X_1+⋯+X_n$, I am looking to show that convergence on $S_n$ in probability implies almost sure convergence by showing that $P(\sup_{m\geq 1}|S_m|>4\epsilon)\leq 4\sup_{m\geq 1} P(|S_m|>\epsilon)$.   I have been trying using Kolmogorov's maximal inequality but not much luck. Do I need to be looking at some martingale? Any hints?

Let $X_n$, $n=1,2,3,...$ be a sequence of independent (not necessarily identically distributed) random variables, let $S_n=\sum_{i=1}^nX_i$. Prove the following maximal inequality: For all $t>0$,$$\mathbb{P}\left(\max_{1\leq i\leq n}|S_i|\geq t \right)\leq 3\max_{1\leq i\leq n}\mathbb{P}\left(|S_i|\geq\frac{t}{3} \right)$$


I would like to make horizontal lines at each side of some text. I tried to use \rule, but I want the total lenght (text + line) to be the same (and user defined) for several line-text, so the line lenght depends on the text lenght. Example :    Is there a package or a native LaTeX command to do the trick ?

I'd like to have a horizontal line extending from the end of the text on a line to the right margin. So far I've found \hrulefill and \leaders\hrule\hfill, but these draw a line that's flush with the baseline of my text — how can I get it to be vertically centered?


Ok, so I did a fresh install of Ubuntu 17.04 Zesty. Me, being stupid like I sometimes am, didn't make a Windows 7 bootable USB. Windows was the only way I could get online(tether through pdanet). So I need someone to use an online Linux machine to apt-get the Deb package and dependencies for me so I can dual boot windows. It would be greatly appreciated being the other fastest way would be if I downloaded every single file one-by-one. Thanks!  EDIT: question isn't about creating the USB itself. It's about getting the program and all dependencies in one go.  EDIT 2: This isn't about making the usb its about helping me get the files on an offline machine with the only other device I have has android on it. I literally just need the deb files in an archive. I already know how to use the tools.

I'd like to create a Windows bootable USB stick, but I don't have a Windows machine with me at the moment to do so. How could I achieve the same using Ubuntu?


I have a list:  mylist = [ "hello", "my", "name", "is", "frank", "and", "it", "is", "great", "to", "be", "here", "in", "this", "great", "country"  ]   and am using   for i in range(0,len(mylist)):     print(mylist[i])   to print out each item and it works as it prints out every word in a new line.   What I would like to do is to be able to treat multiple words in the list as one by changing the value of a variable k:  i.e I would like to instead of it outputting   hello                                                                                my                                                                                name                                                                                is                                                                                frank                                                                                and                                                                                it                                                                                is                                                                                great                                                                                to                                                                                be                                                                                here                                                                                in                                                                                this                                                                                great                                                                                country    I would like to if k = 2 to output  hello my                                                                                name is                                                                                frank and                                                                                it is                                                                                great to                                                                                be here                                                                                in this                                                                                great country    should there be an odd number of items in the list, the last word should be alone in a line  if k = 3 then there should be 3 words in a line  Is there any way to do this  Thank you in advance

I have a list of arbitrary length, and I need to split it up into equal size chunks and operate on it. There are some obvious ways to do this, like keeping a counter and two lists, and when the second list fills up, add it to the first list and empty the second list for the next round of data, but this is potentially extremely expensive.  I was wondering if anyone had a good solution to this for lists of any length, e.g. using generators.  I was looking for something useful in itertools but I couldn't find anything obviously useful. Might've missed it, though.  Related question:


I am a Filipino citizen living in Slovenia and I am a holder of a residence card as a family member of Slovenian citizen. With that card, I can travel with my Slovenian wife to the Canary Islands?  Our flight is from Ljubljana with transit in London Heathrow Airport, where we have to collect and recheck our luggage. Do we need a transit visa?

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


I have created a document in Libreoffice Writer and would like to insert page numbers in the document. I am trying to manually insert the page numbers at each footer. But once i insert a desired page number at the footer, all other pages are marked with the same page number.  How could i fix this?

How can I add the page number in LibreOffice so it appears from a specific page to another in the top right corner.


I would like to prepend the page numbers in my scrbook with a letter and a hyphen. This works well for the page footers by redefining \thepage. However, the page numbers get aligned left instead of right in the TOC.  \documentclass{scrbook} \begin{document} \tableofcontents \renewcommand{\thepage}{\Roman{page}}       % flush right page entries in TOC %\renewcommand{\thepage}{P-\Roman{page}}    % flush left page entries in TOC \clearpage\section{Sec1} \clearpage\section{Sec2} \end{document}   Correct alignment:   Incorrect alignment:   Can I somehow fix the alignment for the prepended page numbers?

I have a scrartcl document with arabic and roman page numbers. The list of tables looks like this:    Arabic page numbers are right justified (relative to each other), whereas roman numbers are centered.   I would like to have all page numbers right justified, like this (the red line is just for illustration):    Although I suppose that the solution is probably related to the listof document options, I cannot find an appropriate setting. However, the problem also occurs with article instead of scrartcl, so it does not seem to be specific to KOMA script.  MWE:  \documentclass{scrartcl} \begin{document} \listoftables \clearpage  \begin{table} \caption{First main table.} \end{table} \clearpage  \setcounter{page}{95} \begin{table} \caption{Second main table.} \end{table} \clearpage  \pagenumbering{roman}  \setcounter{page}{1} \begin{table} \caption{First appendix table.} \end{table} \clearpage  \setcounter{page}{28} \begin{table} \caption{Second appendix table.} \end{table} \end{document}


Voldemort is the only one to make seven, but surely at some point, other dark wizards would have tried/succeeded in making horcruxes. Are there any other wizards that have created Horcruxes?

Horcruxes are rare (and then seven come along at once...) and only a few people know about them.  But when was the last Horcrux before Voldemort's? 50 years before him? Centuries? Millennia?


What is the sum of this series: $$S(z) = \sum_{n=1}^{\infty}{n^2z^n}$$  I know it diverges to infinity. Does the sum just equal infinity then?

Could anyone help me find an explicit formula for:  $$ \sum_{n=1}^\infty n^2x^n $$  We're supposed to use: $$\sum_{n=1}^\infty nx^n = \frac{x}{(1-x)^2}  \qquad  |x| <1 $$


I have been thinking about how to prove that the integral domain $\mathbb{R}[x,y]/(x^2+y^2-1)$ is integrally closed and I am writing this post to ask for proof verification.   Attempt.   Let $R=\mathbb{R}[x,y]/(x^2+y^2-1)$. Then $Q(R)=\frac{R}{\{nonzero\:elements\: of\:R\}}$. But {nonzero elements of $R$} is the complement of $(x^2+y^2-1)$ which is the prime ideal of $\mathbb{R}[x,y]$. So letting $p=(x^2+y^2-1)$, $Q(R)=(\mathbb{R}[x,y]/(x^2+y^2-1))_p=R_p.$ Let $\overline{R}$ be the integral closure of $R$ in $Q(R)$. Then since $(\overline{R})_p$ is the integral closure of $R_p(=Q(R))$ in $Q(R)_p(=Q(R))$, $\overline{R}_p=R_p$. And for all other primes $p'$ in $\mathbb{R}[x,y]$, $p'^c\cap p\neq\emptyset$. So $R_{p'}=0={\overline{R}}_{p'}$, which concludes $R=\overline{R}$.

Let $R = F[x,y]/(ax^2+by^2-1)$, where $F$ is a field with $\text{char}(F) \neq 2$ and $a, b \neq 0$. Then $R$ is Dedekind.    My attempt:  $R$ is Dedekind if and only if it is Noetherian, integrally closed, and if every prime ideal is maximal, so it suffices to show these conditions.   Noetherian: I wasn't able to explicitly prove this, but I'm pretty sure that every polynomial in $F[x,y]$ of degree greater than 3 can be expressed as the sum of factors of $ax^2+by^2-1$ and polynomials of degree at most 2, so that $R$ consists of polynomials of degree at most 2. If this is true, then the possible non-units are the possible sums and products of $x, y, x^2, y^2$, and since these are the possible generators of nonzero proper ideals, every ideal is finitely generated, so $R$ is noetherian. Integrally closed: My idea was to show the stronger condition that $R$ is a UFD. Since $ax^2+by^2-1$ is irreducible over $F[x,y]$, $R$ is a domain. Since $ax^2 + by^2 = 1 \in R$, $f \in R^x$ if and only if $f \mid ax^2 + by^2$. But when I tried to use this to show that irreducible elements are prime, I got stuck, and I'm no longer sure $R$ is a UFD, but I can't think of a counterexample either. Every nonzero prime ideal is maximal: Let $P$ be a nonzero prime ideal of $R$. Then, there exists a nonzero ideal $P' \subset F[x,y]$ such that $P'/(ax^2+by^2-1) \cong P$, where this projection comes from the first isomorphism theorem and the canonical projection $\phi: P' \rightarrow P$, where $\text{ker}(\phi) = (ax^2+by^2-1)$. Since the preimage of a prime ideal is also a prime ideal, $P'$ is a prime ideal, and since $$R/P \cong \left(F[x,y]/(ax^2+by^2-1) \right) / \left(P' / (ax^2+by^2-1) \right) \cong F[x,y] / P'$$ by the third isomorphism theorem, it suffices to show that $P'$ is maximal. I feel like $P'$ should be maximal in $F[x,y]$ since $P'$ must contain polynomials of degree at most two, and since these polynomials are "small", the ideal containing them should be "large", but I'm stuck trying to turn this intuition into something formal.


If 1 mole of X is approximately $6.02 \cdot 10^{23}$ X, why is it a unit?   How does it have the characteristics of a unit? Is it just a different way of writing the Avogadro's constant? Does amount actually have a unit or is it unitless?

According to the BIPM and Wikipedia, "amount of substance" (as measured in moles) is one of the base quantities in our system of weights and measures. Why?  I get why the mole is useful as a unit. In fact, my question isn't really about the mole at all; I just mention it because what little information I could find generally talked about moles, not about "amount of substance". Nor am I asking about why it's chosen as a base quantity and not a derived quantity. I get that any particular choice of bases is more or less arbitrary.  I don't understand why it's a dimensional quantity at all. It is, after all, just a count of things; every student is taught to think of it as "like 'a dozen', only more sciencey". Can't we just call it a dimensionless number?  No, says SI; molar mass doesn't just have dimensions of $\mathsf{M}$, it has dimensions of $\mathsf{M}\cdot\mathsf{N}^{-1}$; and Avogadro's number isn't just a number, it's got units of "per mole" (or dimensions of $\mathsf{N}^{-1}$).  Contrast this with an "actual" dimensionless quantity, plane angle (and its unit the radian). Now, you might say that it's dimensionless because radians are defined as arc length over radius, and so plane angle is just $\mathsf{L}\cdot\mathsf{L}^{-1}$; cancel out and you have no dimensions. That strikes me as arbitrary. We could just as easily argue that arc length is "really" a quantity of $\mathsf{a}\cdot \mathsf{L}$ (where $\mathsf{a}$ is plane angle), because it's the measurement of a quantity that subtends $\mathsf{a}$ at distance $\mathsf{L}$.  But this isn't needed; plane angle isn't even a derived quantity, it's a non-quantity. Plane angle is accepted as dimensionless. Why isn't amount of substance?  As I said, I've found very little on this question. From , I found a PDF of . It acknowledges the argument (as does the Wikipedia article), but dismisses it out of hand by saying (essentially) "of course counting things is a way of measuring things, so of course we need a unit of measurement for it".  Other than that, Wikipedia (as far as I can tell) touches on eliminating the mole only in the context of eliminating other units (as for example in natural systems of units). The  blithely cuts moles from the base units as being "just a count of things", but doesn't go into why SI says it is necessary.  Is there any official rationale for the inclusion of "amount of substance" as a dimension? Failing that, can anyone provide, or point me to, some good reasons why it's so special?  EDIT: Thank you all for your input. The more I've thought about it, the more I've come to feel that there's no reason why "count of stuff" shouldn't be a dimension (it's clearly different from, say, a dimensionless number included as a scale factor), and that my unease with the idea comes from simple habit: in any case not involving moles, it tends to get left out. Really, I'm now more wondering why angles are considered dimensionless...    Reading before coming here:    (I thought maybe a committee with this name would be in charge of explaining why amount of substance is needed, but no; it seems they just deal with standardising it)  Wikipedia:    (including a PDF from BIPM linked at bottom, which only confirms that "amount of substance" is one of the base quantities)  (including the PDF from IUPAC mentioned above)


while am trying with ref keyword by replacing out key word there is no error in the below code.while am trying to use out instead of ref there occur an error like"Unassigned OUT Parameter"  What does this error mean ?     static void Main()     {         string test = "34";         addOneToRefParam(out test);         Console.WriteLine("test is : " + test);     }      public static void addOneToRefParam(out string i)     {         int  k =Convert.ToInt32(i) + 1;         i = Convert.ToString(k);         Console.WriteLine("i is : " + i);     }

What is the difference between ref and out parameters in .NET? What are the situations where one can be more useful than the other? What would be a code snippet where one can be used and another can't?


The volume form on the unit sphere $S^{n}$ in $\mathbb{R}^{n+1}$ is given by  $$i_{\bf r}\ dx^1 \wedge \cdots \wedge dx^{n+1}=\sum (-1)^{i-1} x^i \, dx^1 \wedge\cdots \wedge \widehat{dx^i} \wedge \cdots \wedge dx^{n+1}$$    Why must the volume form $dx^1 \wedge \dots \wedge dx^{n+1}$ act on the vector ${\bf r}$ to give the volume form on the unit sphere?  Also, how do I get the form of the volume form on the right-hand side of the equation?

Let $\omega$ the (n-1) form on $\mathbb{R}^n$ $$\omega=\sum_{j=1}^{n}(-1)^{j-1}x_{j}dx_{1}\wedge\cdots\wedge \hat{dx_{j}}\wedge\cdots dx_{n}$$ Show that the restriction of $\omega$ to $S^{n-1}$ in precisely the volume for this sphere.  What I did was: $\omega$ never vanish on the sphere, because, defining $\sigma\in \Omega^{n-1}(S)$ for $$\sigma_{p}(v_{1},...,v_{n-1})=det(p,v_{1},...,v_{n-1})$$ and $i:S^{n-1}\rightarrow \mathbb{R}^{n}$ the inclusion function, then $\omega=i^{\ast}(\sigma)$ then $\omega\not=0$ and therfore is a volume form.   How proof that $\omega$ is the volume form?   The first thing that comes to mind is show that $\int_{S^{n-1}}\omega=Vol(S^{n-1})$ but I have serious problems with the definition, I think that is to much.   How see that $\omega$ is invariant on $\mathbb{R}^{n}$ under action of $O(n)$


How to enable network time synchronization on Ubuntu 16.04? How to verify/ensure that network time synchronization is disabled?

This question shows how to stop automatic time update (and switch to manual):    I want to do this exact thing but I can only ssh onto my machine so I need to make this change through the terminal. Is there any way to do this?


Hello I'm currently running page wish has regular traffic, this page has made only for linking or referring to other websites, The users can find what they looking for in my page, but the user bounce rate, of course, is too low because as I said it refers to other websites/articles  Will that reduces my page ranking on google?  Or Google can count it as good behavior and upper my page.  waiting for your experience

My 1 blog is now 8-months old I receive on average anywhere from 700-1200 people per day, however it is not so much the acquisition numbers in terms of visitor count that interest me, it is the time on site spend, below you can see an image from  yesterday's traffic.    Currently my average visit time is 5.28min I have been working to increase this to 7-min by writing longer posts, which is rather difficult and also I am worried it will start to become to long for users.  When looking at my current time on site spend, would you say it is adequate for a sports niche blog?   If I can increase my time on site spend to say 7 or 8 min am I likely to see an increase in traffic, or am I wasting my time focusing on this?  QUESTION UPDATE  What I am asking is, if there is a direct correlation between time on on site spend from organic traffic to increased ranking?   As for longer content mentioned in comments, my posts are starting to average 2000-words and I am outranking many competitors without backlinks to those posts, so I will say that content length DOES play a direct role in rankings (even more so than backlinks IMO) I would like to know however, how much of a factor is time on site spend


Is it possible to downgrade Safari 6 to 5 in Mountain Lion?  I tried to install 5.1.7 but it says it only works with OS X 10.7.  Is there any workaround I can try?

I understand there was a uninstaller for Safari 6 beta (is that available anywhere?) but it seems no longer available in the Apple Dev Center, and I am on Safari 6 release version.  I need to remove this and revet back to 5.1.7.


I'm trying to write a script that looks into a database and lists all the datasets that begin with zone. The script then enters into a for loop and copies a map into each on the datasets listed. The code returned exit code 0 and it even prints the zone in the interactive window, but the map isn't copied into the respective datasets. This is the code I have so far:  import arcpy import os PATH = r"C:\Users\Daimon Nurse\Desktop\DFMPROJECT\DFM.gdb" PATH2 = r"C:\Users\Daimon Nurse\Desktop\DFMPROJECT" arcpy.env.workspace = PATH arcpy.env.overwriteOutput=True  zones = arcpy.ListDatasets("Zone*") mxd = arcpy.mapping.MapDocument(r"C:\Users\Daimon Nurse\Desktop\DFMPROJECT\Complete Final Capstone Map\Complete Z2 Campus Map_Landscape1.mxd") for zone in zones:     print zone     mxd.saveACopy(PATH2 + zone +  ".mxd")

I have a script that looks through datasets in a geodatabase and copies a mxd document to a folder. The programs works, however it is saving the map documents to my desktop and not the specified folder on my desktop (PATH2). This is the code I have so far:  import arcpy import os PATH1 = r"C:\Users\Daimon Nurse\Desktop\DFMPROJECT\DFM.gdb" PATH2 = r"C:\Users\Daimon Nurse\Desktop\DFMPROJECT\" arcpy.env.workspace = PATH1 arcpy.env.overwriteOutput=True  zones = arcpy.ListDatasets("Zone*")  for zone in zones:     mxd = arcpy.mapping.MapDocument(r"C:\Users\Daimon Nurse\Desktop\DFMPROJECT\Complete Final Capstone Map\Complete Z2 Campus Map_Landscape1.mxd")     print zone     mxd.saveACopy(PATH2 + zone)


I have a class Product where a product has a name:  package main;  public class Product {      private String name;      public Product(String name) {         super();         this.name = name;     }      public String getName() {         return name;     }      public void setName(String name) {         this.name = name;     }  }   And a class Combination where a combination has an array list of products:  package main;  import java.util.ArrayList;  public class Combination {      private ArrayList<Product> products;      public Combination(ArrayList<Product> products) {         super();         this.products = products;     }      public ArrayList<Product> getProducts() {         return products;     }      public void setProducts(ArrayList<Product> products) {         this.products = products;     }     }   In Main I create an array list of products and I want to get all possible combinations of products.  package main;  import java.util.ArrayList;  public class Main {      public static void main(String[] args) {          ArrayList<Product> products = new ArrayList<Product>();          products.add(new Product("p1"));         products.add(new Product("p2"));         products.add(new Product("p3"));         products.add(new Product("p4"));          ArrayList<Combination> combinations = getCombinations(products);      }      public static ArrayList<Combination> getCombinations(ArrayList<Product> products){         ArrayList<Combination> combinations = new ArrayList<Combination>();         //CODE TO ADD         return combinations;     }  }   What is the fastest solution to get all combinations? In the shown example I will get the following combinations:  p1  p1 p2  p1 p2 p3  p1 p2 p3 p4  p1 p2 p4  p1 p3   p1 p3 p4  p1 p4  p2   p2 p3  p2 p3 p4  p2 p4  p3  p3 p4  p4  I don't care about the order in which I retrieve the combinations, the important is to get all of them in the fastest way.

I want to write a function that takes an array of letters as an argument and a number of those letters to select.   Say you provide an array of 8 letters and want to select 3 letters from that. Then you should get:  8! / ((8 - 3)! * 3!) = 56   Arrays (or words) in return consisting of 3 letters each.


This originally started bothering me when voting to close as duplicate of a question which had deleted answers. I thought to myself, "Why on Earth am I being shown the deleted answers for this?" Why do I want to scroll through a bunch of deleted content that the average user won't even see when they get there?  After dealing with it more, it really doesn't seem clear to me why it loads answers at all. A mobile device just isn't friendly enough to be loading extremely long blocks of text like this. The question itself will suffice. If I wa t to see the answers, I can go to the question itself. Seriously, you try to close a question as a duplicate of the Formatting Sandbox on the mobile layout, see where that gets you...  Can the answers please be removed from the vote to close as duplicate dialog on the mobile layout?

Attempting to use the site with a Nexus 4.  I came across a question that was a duplicate, so I found the dupe and voted to close.  The only problem:  the button is at the bottom of the modal.  While in mobile view, that means lots of painful scrolling all the way through the question and its answers.  On the normal site this isn't an issue:    ...but on the mobile site...    Here's an example:    This definitely affects usability while on mobile.


In visual c#, how can I limit the textbox entries to real nos? When i used richtext box and mask it, the length of the number gets limited, which is what I don't want Any suggestions?

I have a windows forms app with a textbox control that I want to only accept integer values. In the past I've done this kind of validation by overloading the KeyPress event and just removing characters which didn't fit the specification. I've looked at the MaskedTextBox control but I'd like a more general solution that could work with perhaps a regular expression, or depend on the values of other controls.  Ideally this would behave such that pressing a non numeric character would either produce no result or immediately provide the user with feedback about the invalid character.


How to disable Ctrl+Q system wide?  I read the other answers but they did not help. Reassigning the shortcut is not possible, since pressing the key combination quits the settings window, so it does not have any effect.  Thanks in advance.

A lot of applications like Firefox, Chrome etc, get closed when I accidentally press Ctrl+Q instead of Ctrl+W because of the proximity of the Q and W keys on the keyboard. Is there a way this shortcut can be removed or reset on a system wide basis?


would like help on the proof, I have most of it but got stuck in one part. my proof is: lets assume there are finite number of primes in the form 4n-1. let P be their product, define N=4P-1. so none of the primes of the form 4n-1 divide N yet there is a prime that divide N, say q.   I know I need to show that q is of the form 4n-1 but have no idea how to prove it, would greatly appreciate your help

This is the proof from the book:     Theorem. There are infinitely many primes of the form $4n+3$.    Lemma. If $a$ and $b$ are integers, both of the form $4n + 1$, then the product $ab$ is also in this form.  Proof of Theorem: Let assume that there are only a finite number of primes of the form $4n + 3$, say  $$p_0, p_1, p_2, \ldots, p_r.$$ Let $$Q = 4p_1p_2p_3\cdots p_r + 3.$$ Then there is at least one prime in the factorization of $Q$ of the form $4n + 3$. Otherwise, all of these primes would be of the form $4n + 1$, and by the Lemma above, this would imply that $Q$ would also be of this form, which is a contradiction. However, none of the prime $p_0, p_1,\ldots, p_n$ divides $Q$. The prime $3$ does not divide $Q$, for if $3|Q$  then $$3|(Q-3) = 4p_1p_2p_3\cdots p_r,$$ which is a contradiction. Likewise, none of the primes $p_j$ can divides $Q$, because $p_j | Q$ implies $p_j | ( Q - 4p_1p_2\cdots p_r ) = 3$, which is absurd. Hence, there are infinitely many primes of the form $4n +3$.   END  From "however, none of the prime ...." to the end, I totally lost!    My questions:   Is the author assuming $Q$ is prime or is not? Why none of the primes $p_0, p_1,\ldots, p_r$ divide $Q$? Based on what argument?     Can anyone share me a better proof?     Thanks.


$$\hat{\theta}=\arg\min_{\theta}\{ ||y-X\theta||_2^2+\lambda||\theta||_2^2\},$$ where $X$ is an $n\times p$ matrix.    We have if $y=X\theta+\varepsilon$ then $$\hat{\theta}^{\text{ridge}}=(X^TX+\lambda I)^{-1}X^Ty$$ So I'm kinda confused, because if $y=X\theta+\varepsilon$, then $||y-X\theta||_2^2+\lambda||\theta||_2^2=||\varepsilon||_2^2+\lambda||\theta||_2^2.$ But I'm confused as to how to show that  $$(X^TX+\lambda I)^{-1}X^Ty=\arg\min_{\theta}\{ ||y-X\theta||_2^2+\lambda||\theta||_2^2\}.$$ Any help would be much appreciated. Thank you. I gotta edit this cause someone said it's a duplicate of an entirely different problem cool.

In ridge regression, the objective function to be minimized is: $$\text{RSS}+\lambda \sum\beta_j^2.$$   Can this be optimized using the Lagrange multiplier method? Or is it straight differentiation?


Is there any difference between writing the following two? The code is for C#  String S1 = "The " + Item.Name + " is made of " + Item.Property + " and is at " + Item.Durability + "% durability."   against  String S2 = "The {0} is made of {1} and is at {2} % durability.", Item.Name, Item.Property, Item.Durability   ? Assuming that item is populated with, for instance, name of Axe, property of Steel, and durability of 50 as a string.

Let's say that you want to output or concat strings. Which of the following styles do you prefer?   var p = new { FirstName = "Bill", LastName = "Gates" }; Console.WriteLine("{0} {1}", p.FirstName, p.LastName); Console.WriteLine(p.FirstName + " " + p.LastName);   Do you rather use format or do you simply concat strings? What is your favorite? Is one of these hurting your eyes?  Do you have any rational arguments to use one and not the other?  I'd go for the second one.


I need to run cmd commands in a c# program im writing, the only solutions ive found make a new command line instance for every command, but i need them to be executed in the same instance    public static void UpdateDeviceData()         {             Process.Start("CMD.exe",                 String.Format("client_commandline.exe setdeviceposition 0 {0} {1} {2}", LPos.X, LPos.Y, LPos.Z));         }

I'm trying to execute multiple commands without create a new process each time. Basically, I want to start the DOS command shell, switch to the MySQL command shell, and execute a command. Here's how I am calling the procedure (also below). Also, how do I handle the "\"'s in the command?  ExecuteCommand("mysql --user=root --password=sa casemanager", 100, false);  ExecuteCommand(@"\. " + Environment.CurrentDirectory + @"\MySQL\CaseManager.sql", 100, true);  private void ExecuteCommand(string Command, int Timeout, Boolean closeProcess) {     ProcessStartInfo ProcessInfo;     Process Process;      ProcessInfo = new ProcessStartInfo("cmd.exe", "/C " + Command);     ProcessInfo.CreateNoWindow = false;     ProcessInfo.UseShellExecute = false;     Process = Process.Start(ProcessInfo);     Process.WaitForExit(Timeout);      if (closeProcess == true) { Process.Close(); } }


I am having a problem downloading a file using selenium.  I had to use selenium to hover over some menus and finally got to the last link which I need to click and reveal 30 zipped files that have a href link.  I want to click on each link and download.  What libraries do I have to make this available to me?  This is my problem:   Need to click the following links:  Corp_sub3_20180107.zip corp_sub3_20180106.zip  corp_sub3_20180105.zip   When hovering my mouse over the first corp_sub3, I see  in windows explorer:   Upon clicking in selenium, I get a "do you want to open or save dialog" box at the bottom.  I'm not able to use selenium to choose the save option for some reason.  What options do I have?  I can only use internet explorer for this problem.    Thanks

I have to automate a case in which I have to download an Excel file using Selenium IDE.I have done this in Firefox by using custom profile feature which automatically downloads file and saves it into a user-defined folder. To do the same in Internet Explorer (IE), is there anything in IE like custom profile and preferences? how do I prompt IE to automatically download a file? I am using Java for automation. Kindly help. *If you guys use java selenium, this article will be useful Selenium WebDriver で IE11/Edge のファイルダウンロードを自動化する （IE11/Edge file download process automation by Selenium WebDriver）


I can't start any virtual machine in virtualbox.I get this error message every time when I try to start a virtual machine:   NS_ERROR_FAILURE (0x80004005) ConsoleWrap IConsole {872da645-4a9b-1727-bee2-5585105b9eed}   My pc is 10 years old. cpu: AMD Athlon x2 64 5200+. Gpu: Nvidia gt 710 2gb vram. 4 gb of ram. What's the problem? Please help!

Yesterday my Virtualbox guests were still running. Today I get the following error for all guests (windows or Linux).  Failed to open a session for the virtual machine win10.  The VM session was closed before any attempt to power it on.  Result Code: NS_ERROR_FAILURE (0x80004005) Component: SessionMachine Interface: ISession {7844aa05-b02e-4cdd-a04f-ade4a762e6b7}   I already tried to run sudo /sbin/vboxconfig, reinstalling from Software Manager, reinstalling following  and upgrading to 5.2.12 r122591 and 5.2.14 r123301. The result was always the same.  My current kernel version is 4.15.0-24-generic #26-Ubuntu SMP.  $ VBoxManage list extpacks Extension Packs: 1 Pack no. 0:   Oracle VM VirtualBox Extension Pack Version:      5.2.14 Revision:     123301 Edition:       Description:  USB 2.0 and USB 3.0 Host Controller, Host Webcam, VirtualBox RDP, PXE ROM, Disk Encryption, NVMe. VRDE Module:  VBoxVRDP Usable:       true


When someone is very hungry we say he is starving. How to describe someone who is very thirsty?

I don't know if the title is completely appropriate/applicable, but I guess it'll have to do until there's an edit.  So a if one dies of starvation, one dies from "suffering or death caused by hunger (New Oxford American Dictionary)". Is there a given term for "suffering or death caused by lack of water/thirst"? When one says "He starved to death", the meaning is "He died from hunger", but there's no term (at least to the best of my knowledge) for something like "He (word for died from thirst) to death)".


Task is to find $$\prod_{k=0}^{\infty} \cos(x \cdot 2^{-k}).$$  I tried to make it with double-angle formula: $\prod_{k=0}^{\infty} \cos(x \cdot 2^{-k}) = \frac{\prod_{k=0}^\infty \sin(x2^{1-k})}{2^\infty \cdot \prod_{k=0}^\infty \sin(x \cdot 2^{-k})} $ I'm sad to admit, that I'm stuck with that one. So I would appreciate any help, such as pointing the right direction.

This limit seemed quite unusual to me as there aren't any intermediate forms or series expansions which are generally used in limits. Stuck on this for a while now .Here's how it goes :    $$ \lim \limits_{n \to \infty} \left[\cos\left(x \over 2\right)\cos\left(x \over 4\right)       \cos\left(x \over 8\right)\ \cdots\ \cos\left(x \over 2^{n}\right)\right] $$


I wanted to check the FAQ to see if there was a guide on giving good answers, and I couldn't find one. Am I blind? Should this be added?  What made me think of it is a common theme in bad answers I have noticed recently. Usually involving the phrase, "I'm not sure but ..." or "I think...". My thought about answers like this is: The SO community is big enough that you should never answer if you're not sure. Someone is sure, and they will answer.  It might be nice to have a guide to refer to.

UPDATE: This is now live on all Stack Exchange sites. You can access it at /help or by clicking the "help" link in the top nav or footer of any page.   We can all agree that Stack Exchange is a complicated beast that takes a while to understand. New users can be overwhelmed and confused by all of the rules, where to find them, and how to abide by them. Even though many established users leave comments linking to helpful resources, or answer questions posted to metas, it's a scattershot way to help users learn our rules and answer their questions.  And so, we're introducing a new Help Center, which you can now see here on MSO: .  Here's what we're hoping to achieve:   Consolidate important information that is currently scattered throughout a great many resources: MSO and child metas'  lists, each site's official FAQ page, blog posts, and miscellaneous other resources like our  pages and  /  guides. Any rules or explanations of basic site mechanics should be easily accessible in one place. Allow easy linking and easy navigation. Each topic is separated out onto its own page, with a unique URL to allow pointed linking to that page. Each article page also has sidebar navigation that shows other topics in the same category, as well as a list of other categories, for the rare user who is motivated to read more. Use comprehensible language that non-power users will be able to understand. A lot of our guidance, written by the community and by Stack Exchange itself, uses jargon that can be unclear to users learning our system for the first time. We want to make sure terminology is sufficiently explained and use plain language wherever possible.   This Help Center will (once we roll it out to all sites) replace the current FAQ pages. Each site will continue to have its own  tag on meta, but any policy that is essential to the functioning of the community will be rolled into the appropriate section of the new Help Center.  What's broken, and what are we missing?  We're already planning to add more features and articles to the Help Center in the coming weeks, but we wanted to show you all the core of it and get your feedback. There are additional articles that we plan to include here (especially in the "Reputation & Privileges" category), but the articles currently included should cover everything that exists in the current FAQ and old /help page /contact page (which will be redesigned when the new Help Center is live everywhere).  This is live only on MSO right now. We want to get your opinions about the Help Center in general, fix any bugs or typos you might find, and add any crucial information that's missing. Once we've addressed all those things, the new Help Center will roll out network-wide.   A couple of implementation notes:   We will be adding a "search" feature to the /help landing page that will make it easier for users with a specific problem to find the relevant article(s). Site moderators will be able to edit the  page to include lists of what is on- and off-topic for each site, just as they can currently edit the "What can I ask here?" part of the current FAQ. You may notice that some article titles are preceded by a round bullet. The bullet is temporary while Jin designs an icon, but those articles are "featured" articles; they are meant to draw attention to the most important site policies or most frequently encountered issues. Fixed   So there you have it. A new, consolidated, Help Center to provide a single resource for users looking to understand how our network works.  We're still making some small changes to this feature. Please continue to post here on meta if you encounter any bugs / typos / broken links. If you want to suggest a new page, have an issue specific to one site, or have another major change, you can start a new meta post and tag it .


Let p and q are odd prime numbers such that q=2p+1. Prove that   i) $-4$ is primitive root modulo $q$.  ii) If $p  \equiv  1 \pmod 4$ then $2$ is a primitive root mod $q$.   iii) If $p  \equiv  -1 \pmod 4$ then $-2$ is a primitive root mod $q$.

If $p$ and $q = 2p + 1$ are both odd primes, show that $-4$ and $2(-1)^{(1/2)(p-1)}$ are both primitive roots modulo $q$.   I cannot get heads nor tails of how to even start this let alone finish it


I have a number coming in as a string. When I try to cast it into a number it seems to be rounding it in a weird way. parseInt('10211688549781435') results in 10211688549781436  Similarly playing around with these numbers I get the following answers: parseInt('10211688549781436') results in 10211688549781436 parseInt('10211688549781437') results in 10211688549781436 parseInt('10211688549781438') results in 10211688549781438 parseInt('10211688549781439') results in 1021168854978140  What is causing this behaviour?

Is this defined by the language? Is there a defined maximum? Is it different in different browsers?


I followed , which was subsequently . I am now seeing the CV question in my "Following" tab on my profile, with an "unfollow" link. If I click that link, a popup informs me that "This post has been locked; locked posts can't be voted on." Looks like a bug to me. Please allow me to unfollow migrated questions.  is related. (I also followed a deleted question, but for that, clicking "unfollow" worked.)  has been proposed as a duplicate. It isn't: it states that "I can only unfollow it by going through the profile." I can not unfollow a migrated question in my profile.  describes the exact behavior I am having, just for deleted-as-spam questions instead of migrated ones. It may be that both questions can be addressed through the same underlying fix.

Now that we can unfollow deleted posts, there is an issue with being unable to unfollow answers which were locked due to being rude or spam. There is a button on the answer and when clicked it changes state, but I get a red popup with the message:  This post has been locked; locked posts can't be voted on  Also, the unfollow/following button on the questions is gone, I can only unfollow it by going through the profile. If the answer was deleted by the owner then I can both unfollow and follow it again without issues. I haven't tried it with locked questions yet, but I can't even follow a deleted question again from my profile page. I get this error message:  Following not enabled for this post.  To summarize:  I can unfollow deleted questions, but only from profile page I can't follow deleted questions I can unfollow and follow deleted answers. Both from post view and profile I can't follow/unfollow locked posts  P.S. Filtering doesn't work with paging. When I select answers only and go to second page the filtering turns off.


I cannot manage to understand why g++ keeps complaining about iter?  vector.cpp:42:8: error: ”typename” needed before ”std::initializer_list<_Tp>::iterator  This is the code:  template<typename T> Vector<T>& Vector<T>::operator=(std::initializer_list<T> list) {    if ( list.size() > 0 )    {        clear();         for( std::initializer_list<T>::iterator iter = list.begin();             iter != list.end(); iter++ )         {            push_back(*iter);        }    }     return *this; }   Kind regards

In templates, where and why do I have to put typename and template on dependent names? What exactly are dependent names anyway?    I have the following code:  template <typename T, typename Tail> // Tail will be a UnionNode too. struct UnionNode : public Tail {     // ...     template<typename U> struct inUnion {         // Q: where to add typename/template here?         typedef Tail::inUnion<U> dummy;      };     template< > struct inUnion<T> {     }; }; template <typename T> // For the last node Tn. struct UnionNode<T, void> {     // ...     template<typename U> struct inUnion {         char fail[ -2 + (sizeof(U)%2) ]; // Cannot be instantiated for any U     };     template< > struct inUnion<T> {     }; };   The problem I have is in the typedef Tail::inUnion<U> dummy line. I'm fairly certain that inUnion is a dependent name, and VC++ is quite right in choking on it. I also know that I should be able to add template somewhere to tell the compiler that inUnion is a template-id. But where exactly? And should it then assume that inUnion is a class template, i.e. inUnion<U> names a type and not a function?


I'm trying to plot characteristics for the Burgers Equations. But I have to plot them only using the inbuilt function plot. It seems like a fairly straight forward problem but I still cant solve it

I'm trying to plot the characteristics for the following problem.  Consider the first order nonlinear hyperbolic PDE (the inviscid Burgers' equation) $$ \frac{\partial u}{\partial t} + u \frac{\partial u}{\partial x} = 0 , \tag{1.2a} $$ with the boundary and initial conditions defined by $$ u(0,t) = 0,\qquad u(x,0) = \begin{cases} \sin^2(\pi x) &\quad 0\leq x\leq1,\\ 0 &\quad 1\leq x\leq 2. \end{cases} \tag{1.2b} $$  So far I have managed to find all the gradients for the lines from each value of $x_0$. But I'm not sure how to plot it. It seems like a very simple question but one I'm finding really difficult. I also cannot use any inbuilt matlab functions except the very minimal ones such as plot. Here is my code so far.. dx=0.01;%spatial step dt=dx;%set time and space steps equal X=2;%end of space interval x=0:dx:X;%space vector formed Tf=1;%end of time interval n=floor(X/dx);%number of overall space steps n1=floor(1/dx);%number of space steps needed - 1st interval timesteps=floor(Tf/dt);%number of time steps  u1=sin(pi*x).*sin(pi*x); u11=u1(1:n1); u2=zeros(1,n1+1);  %initial conditions  u0=[u11,u2]; %form ic vector u0 u=u0; c=1./u0;%gives the gradients of each x0 point


When I search for files in windows explorer, it does not find any files ("No items match your search.") event though I can see the files in the directory.  For example, searching for "*.h" finds nothing.  Used to work just fine.  Windows-7 Pro 64-bit

I can't use the Windows 7 File Explorer search successfully. If I enter a search string, for instance car in the search box, I just get No files found, despite obviously having several files that match the string (blue_cars.jpg, carrot.gif) in the current folder. I have edited the search options so that both file names and contents are searched, even if they are not indexed.  What am I doing wrong here?


How can I set my bukkit server on my mac to use more than 1 core? I set my server to use 12 gigs of RAM for now, considering that I will be adding more servers soon.  My iMac has these configurations:   3.5GHz Quad-core Intel Core i7, Turbo Boost up to 3.9GHz 32GB 1600MHz DDR3 SDRAM - 4X8GB 1TB of PCIe-Based Flash Storage NVIDIA GeForce GTX 780M 4GB GDDR5   It uses mavericks.  Also, is it possible to use the graphics card for the server (considering that the RAM on it is MUCH faster than the standard 1600MHz RAM) when the card is not in use?  Thanks so much guys!

I am working on setting up a Minecraft server on a machine I have at home. This particular machine has two quad-core CPUs running at 2.0Ghz so I would like to take advantage of the number of cores and run a server with 4 or 6 of the cores. My server of choice is CraftBukkit, the latest version of which is craftbukkit-1.4.7-R1.0 and launched with a start-up script of:  "C:\Program Files\Java\jre7\bin\java.exe" -Xms1G -Xmx8G -jar craftbukkit-1.4.7-R1.0.jar"   The  says:     Minecraft servers, as of 1.1.0, can use multiple cores, so now they will not sit idle.   but does not really expand on this.  My questions, then:   Is it possible to set the number of cores the server uses? How do I do it - via start-up options, or other methods? Is it really worth it and would it make that much of a difference with a lot of players?


I want to extract half of the space used by the sda1 that is being used by my Ubuntu 17 OS to Dual boot with windows.   Is there any safe way of doing this without losing any data?

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


Though official Catalyst software 13.1 is suitable for ati radeon hd4330, it can't be installed on Ubuntu 14.04 as it can't support Xorg >= 7.6 As I need proprietary drivers for trusty, I would like to know if there is a way to bypass this limitation ? (For example by fetching driver sources)  Here are some results from the terminal :  $ Xorg -version  X.Org X Server 1.15.1 Release Date: 2014-04-13 X Protocol Version 11, Revision 0 Build Operating System: Linux 3.2.0-37-generic x86_64 Ubuntu Current Operating System: Linux bordeaux80 3.13.0-27-generic #50-Ubuntu SMP Thu May 15 18:06:16 UTC 2014 x86_64 Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.13.0-27-generic root=UUID=4015e6f7-d11a-45fd-ac9b-5b6c7ab9eaa0 ro quiet splash vt.handoff=7 Build Date: 16 April 2014  01:36:29PM xorg-server 2:1.15.1-0ubuntu2 (For technical support please see http://www.ubuntu.com/support)  Current version of pixman: 0.30.2     Before reporting problems, check http://wiki.x.org     to make sure that you have the latest version.   $ xrandr  Screen 0: minimum 320 x 200, current 1366 x 768, maximum 8192 x 8192 LVDS connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 353mm x 198mm    1366x768       60.0*+    1280x720       59.9      1152x768       59.8      1024x768       59.9      800x600        59.9      848x480        59.7      720x480        59.7      640x480        59.4   VGA-0 disconnected (normal left inverted right x axis y axis) HDMI-0 disconnected (normal left inverted right x axis y axis)   $ uname -rp  3.13.0-27-generic x86_64   $ glxinfo | grep OpenGL  OpenGL vendor string: X.Org OpenGL renderer string: Gallium 0.4 on AMD RV710 OpenGL core profile version string: 3.1 (Core Profile) Mesa 10.1.0 OpenGL core profile shading language version string: 1.40 OpenGL core profile context flags: (none) OpenGL core profile extensions: OpenGL version string: 3.0 Mesa 10.1.0 OpenGL shading language version string: 1.30 OpenGL context flags: (none) OpenGL extensions:   Edit : Indeed, I would like to use WebGL inside Chrome. But seems like free drivers miss functionalities. This is my chrome://gpu settings :    Regards

chrome://gpu/     And      google-chrome --version  Google Chrome 27.0.1453.93           How To Enable WebGL In Chrome On Ubuntu ?


Can anybody pass me on a good source to see the steps in proving, \begin{equation} \zeta(2n) = \frac{(-1)^{k-1}B_{2k}(2\pi)^{2k}}{2(2k)!} \end{equation} I know how we start by looking at the product of sine and use the generatinf function for the Bernoulli numbers to connect them. I am finding it hard to find a source that doesn't just assume the result or say that it is fairly trivial. Any help would be appreciated, Thanks

I recently, out of interest, tried to prove Euler's formula $\zeta{(2n)}=(-1)^{n-1}\frac{(2\pi)^{2n}}{2(2n)!}B_{2n}$ for all $n\in\mathbb{N}$. I adapted  Euler's original proof for $\zeta(2)=\frac{\pi^2}{6}$:  We have the well known formulas $\sin(x)=\sum_{k=0}^{\infty}\frac{(-1)^kx^{2k+1}}{(2k+1)!}$ and $\sin(x)=x\prod_{k=1}^{\infty}\left(1-\frac{x^2}{k^2\pi^2}\right)$. The product formula can be transformed into a series expansion as well but in order to keep it neat, some definitions first:  For the real sequence $\left(a_i\right)_{i\in\mathbb N}$ with $\sum a_i$ convergent, define $$ A_n:=\sum_{i=1}^{\infty} a_i^n $$ $$ \alpha_n:=\sum_{(x_1,\dots,x_n)\in M_n}\prod_{r=1}^{n} a_{x_r} $$ Where $M_n:=\{(x_1,\dots,x_n)\in\mathbb N\space|\space x_1<\dots<x_n\}$. Now we write $c_i=-\frac{1}{i^2\pi^2}$. When we expand the product, we get only odd exponents of $x$ and the coefficient of $x^{2k+1}$ for $k≥1$ is $\gamma_k$. By comparison of the coefficients, we obtain $\gamma_k=\frac{(-1)^k}{(2k+1)!}$. Now, through telescoping, it can be shown algebraically that for every sequence $\left(a_i\right)_{i\in\mathbb N}$ with $\sum a_i$ convergent we have: $$\sum_{i=1}^{n}{(-1)^{n-i}\alpha_{n+1-i}\space A_{i}}=A_{n+1}+(-1)^{n+1}(n+1)\alpha_{n+1}$$ For all $n\in\mathbb N_0$. Since $C_n=\sum_{i=1}^{\infty} \left(-\frac{1}{i^2\pi^2}\right)^n=\frac{(-1)^n}{\pi^{2n}}\zeta{(2n)}$ we have: $$ \sum_{i=1}^{n}{(-1)^{n-i}\gamma_{n+1-i}\space C_{i}}=\sum_{i=1}^{n}{(-1)^{n-i}\frac{(-1)^{n+1-i}}{(2n-2i+3)!}\frac{(-1)^i}{\pi^{2i}}\zeta{(2i)}}=\sum_{i=1}^{n}{(-1)^{i-1}\frac{\zeta{(2i)}}{(2n-2i+3)!\pi^{2i}}}=\frac{(-1)^{n+1}}{\pi^{2n+2}}\zeta{(2n+2)}+(-1)^{n+1}(n+1)\frac{(-1)^{n+1}}{(2n+3)!}=\frac{(-1)^{n+1}}{\pi^{2n+2}}\zeta{(2n+2)}+\frac{(n+1)}{(2n+3)!} \iff \sum_{i=1}^{n+1}{(-1)^{i-1}\frac{\zeta{(2i)}}{(2n-2i+3)!\pi^{2i}}}=\frac{(n+1)}{(2n+3)!} $$ For all $n\in\mathbb N_0$. Now we are ready to prove the formula $\zeta{(2n)}=(-1)^{n-1}\frac{(2\pi)^{2n}}{2(2n)!}B_{2n}$ with induction. With the equation above we can easily verify that it is true for $n=1$; therefore we assume that it holds for all $1≤i≤n$. The assertion $\zeta{(2n+2)}=(-1)^{n}\frac{(2\pi)^{2n+2}}{2(2n+2)!}B_{2n+2}$ is then equivalent to: $$ \sum_{i=1}^{n+1}{(-1)^{i-1}\frac{(-1)^{i-1}\frac{(2\pi)^{2i}}{2(2i)!}B_{2i}}{(2n-2i+3)!\pi^{2i}}}=\frac{(n+1)}{(2n+3)!}\iff \sum_{i=1}^{n+1}{\binom{2n+3}{2i}2^{2i-1}B_{2i}}=n+1\iff \sum_{i=0}^{2n+2} \binom{2n+3}{i}2^iB_i=0 $$ This identity can be proven by comparing the coefficients in the equation $\frac{e^x-1}{x}\frac{2x}{e^{2x}-1}=\frac{2}{e^x+1}$.   Is this proof valid? Nonetheless, if it is, it isn't very elegant. Are there faster ways to prove it?


How do I solve this login loop? Every time I have given the correct password, but my account is not opening. Every time it comes back to my login prompt. Crashes back to the login screen.

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


At work, I am tasked with creating a user database.  It needs to account for (end)user permissions for 8 different installed programs.  The database will be hosted by each client containing their specific information behind a firewall.  I have the majority of it built out (tables below), but I don't know how to incorporate permissions.  I could put all available permissions in a table, and then link them to users/groups and applications in another table.  Or I could put all available permissions in a table, then link them to users/groups in another table, and then applications in yet another table.  Problem is that both of these options don't play well with the applications because I cannot think of a way to actually search for a specific permission (ex: call to database to find if user can do 'x') without the programmer hard-coding the permission Ids into the program.  I could have a table per application with each of that application's permissions as a column, but there are 70+ permissions for each application and the tables would get huge (also not very expandable if we need to add more permissions later).  So the end questions is; How do I set up permissions for end-user accounts in a way that the programmer does not have to know and hard-code the Ids into the applications?  Table - Description   Applications - Basically a list of our applications so we have an Id to link the permissions to GlobalSettings - Settings used for all users, mostly password requirments Groups - Lists all end-user administrator defined groups of users (this way a permission can be tied to a group of users at one time) PreviousPasswords - Lists the last x hashed passwords for each user (the ones they can't use again) UnusablePasswords - Lists passwords we won't let our end-users use (such as password1) User_Group_Link - Links a User to a Group Users - Lists all end-users and their needed data (birthday, name, etc)

I'm trying to find the best way for a basic security system for a website.  I know I want users and groups.  I thought I'd have:  user_table user_id user_name ...  group_type group_id group_name parent_id ...  group_table id user_id group_id   First one is the user, second one is the group, and the third one is the intermediary table that connects the two.  One user has many groups.  Does this sound ok?


How to write if include? condition in JavaScript?  My sample code is here:  var a = ['red', 'green', 'blue', 'yellow']; if (a.include("red" )) {      alert(a); }   It gives the following error:  SyntaxError: missing : in conditional expression

What is the most concise and efficient way to find out if a JavaScript array contains a value? This is the only way I know to do it: function contains(a, obj) {     for (var i = 0; i < a.length; i++) {         if (a[i] === obj) {             return true;         }     }     return false; }  Is there a better and more concise way to accomplish this?


Let $f\colon [0, 1] → \mathbb{R}$ be a continuous function. Given, $f(0) = 0$ and $\int_0^1 f(x)\, dx = 0$, prove that $∃ c ∈ (0, 1)$ such that $c^2f(c) = 2\int_0^cxf(x) \,dx.$ I need some help on how to use the fundamental theorem to prove this result. My attempt: Let $F'(x)=f(x)$, the $\int_0^1 f(x)\, dx = 0$ implies that $F(1)=F(0)$. Now we take $H(x)=xf(x)$ and $\int_0^c xf(x)dx=\frac{c^2f(c)}{2}-\int_0^c\frac{x^2f'(x)}{2}dx$. This is where I'm stuck.

Question: Let $f:[0,1]\to\mathbb{R}$ be a continuous function such that $f(0)=0$ and $$\int_0^1f(x)dx=0.$$ Prove that $\exists a, b\in(0,1)$ such that $$\int_0^{a} xf(x)dx=0\text{ and }\int_0^bxf(x)dx=\frac{b^2f(b)}{2}.$$  My approach: Let $g:[0,1]\to\mathbb{R}$ be such that $$g(x)=x\int_0^xf(t)dt-\int_0^xtf(t)dt, \forall x\in[0,1].$$ By the first fundamental theorem of calculus we can conclude that $g$ is differentiable on $[0,1]$ and $$g'(x)=\int_0^xf(t)dt, \forall x\in[0,1].$$ Also, observe that $g(0)=0$ and $g(1)=-\int_0^1tf(t)dt$. Thus, by applying MVT to the function $g$ on the interval $[0,1]$, we can conclude that, $\exists c\in(0,1)$ such that $$g'(c)=\int_0^cf(t)dt=-\int_0^1tf(t)dt.$$ Observe that clearly three cases are possible, i.e, either$$\int_0^cf(t)dt<0\text{ or }\int_0^cf(t)dt=0\text{ or }\int_0^cf(t)dt>0.$$ Now let $h:[0,1]\to\mathbb{R}$ be such that $$h(x)=\int_0^xtf(t)dt, \forall x\in[0,1].$$ Please note that the part highlighted below is wrong, but still I have included it to just demonstrate my thinking process, as it might be of some help to others trying out this problem.  Observe that if $\int_0^cf(t)dt<0$, then, $h(1)>0$. This also implies that $\exists$ an open interval $(d,e)\in[0,c]$, such that $f(t)<0, \forall t\in(d,e)$. Now select any point $c_1\in(d,e)$. Applying MVT to the function $h$ on the interval $[0,c_1]$, we can conclude that $\exists c_2\in(0,c_1)$ such that $$h'(c_2).c_1=f(c_2).c_2.c_1=h(c_1)-h(0)=h(c_1)<0.$$ Now $h(c_1)<0$ and $h(1)>0$. Thus, by IVT we can conclude that $\exists a\in(c_1,1)\subseteq(0,1)$, such that $$h(a)=\int_0^af(t)dt=0.$$ A similar reasoning for the case when $\int_0^cf(t)dt>0,$ shows that $\exists a\in(0,1)$, such that $$h(a)=\int_0^af(t)dt=0.$$ Now finally if $\int_0^cf(t)dt=0$, then we will have $h(1)=0$. Now if $f$ is identically equal to $0$ on $[0,c]$, then clearly $tf(t)=0, \forall t\in[0,c]\implies h(x)=0, \forall x\in[0,c].$ Thus choosing any point $x\in(0,c]$ and setting it as $a$, we will have $h(a)=0$ and we will be done in that case. Now if $f$ acquires both positive and negative values on $[0,c]$, then we can conclude that $\exists c_1,c_2\in(0,c)$, such that $f(c_1)>0$ and $f(c_2)<0$. Also, let us assume WLOG that $c_2>c_1$.  I have not been able to make any significant approach other than this. Can someone help me out with this problem? Please note that a solution using integration by parts might not be possible, since $f$ is not a differentiable function.


When I try to install something via a .deb file or just from software center it will say installing for a second or so then go back to the button saying install. When I try to update the software I have installed it just shows the installing sign but doesn't update, I left it running over night but still nothing updated  Picture of me trying to update:

Occasionally, when I'm installing stuff, I get an error like the following:  Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  package1 : Depends: package2 (>= 1.8) but 1.7.5-1ubuntu1 is to be installed E: Unable to correct problems, you have held broken packages.   How can I resolve this?


[root@localhost ~]# echo $$ 16991 [root@localhost ~]# bash -c "echo $$" 16991 [root@localhost ~]# bash -c "echo $$" 16991 [root@localhost ~]# bash -c 'echo $$' 21062 [root@localhost ~]# bash -c 'echo $$' 21063 [root@localhost ~]# bash -c 'echo $$' 21064 [root@localhost ~]# bash -c "echo $$" 16991   I understand that whenever we use single quotes, a new sub-shell is created, and same is not happening with double quotes. Why is it so?

I used to use '' and "" (single and double-quotes) interchangeably on the command line, but I recently noticed that '$HOME/some/dir' is not expanded, while "$HOME/some/dir" is. I searched around a little bit and found that "" allows some protection of special characters, while '' allows full protection. So what other characters are protected by '' and not ""?  EDIT: What are practical situations in which these differences might be significant?


I just bought USB Wireless Adapter but didn't know how to install it. I've tried using lsusb and lshw -C Network before and after plug the USB.   Here's the output of lsusb.  Before:      Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 003: ID 5986:0543 Acer, Inc  Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub   After:  Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 003: ID 5986:0543 Acer, Inc  Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 003 Device 031: ID 0bda:f179 Realtek Semiconductor Corp.  Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub   It seems the difference is Bus 003 Device 031: ID 0bda:f179 Realtek Semiconductor Corp. But the output of lshw -C Network is same.  WARNING: you should run this program as super-user.   *-network                       description: Wireless interface        product: BCM43142 802.11b/g/n        vendor: Broadcom Corporation        physical id: 0        bus info: pci@0000:07:00.0        logical name: wlp7s0        version: 01        serial: b8:76:3f:bc:1d:ef        width: 64 bits        clock: 33MHz        capabilities: bus_master cap_list ethernet physical wireless        configuration: broadcast=yes driver=wl0 driverversion=6.30.223.271 (r587334) latency=0 multicast=yes wireless=IEEE 802.11        resources: irq:16 memory:90700000-90707fff   *-network        description: Ethernet interface        product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:0e:00.0        logical name: enp14s0        version: 0c        serial: 3c:07:71:59:b9:8a        size: 100Mbit/s        capacity: 1Gbit/s        width: 64 bits        clock: 33MHz        capabilities: bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation        configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168g-2_0.0.1 02/06/13 ip=192.168.100.6 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s        resources: irq:27 ioport:2000(size=256) memory:90500000-90500fff memory:90400000-90403fff WARNING: output may be incomplete or inaccurate, you should run this program as super-user.   Should I install realtek wireless driver? If so, how to check which realtek wireless driver I should install? Thanks.

I'm trying to install wifi drivers for a particular mini wifi card i bought. The output of lsusb is:  0bda:f179 Realtek Semiconductor Corp   I've searched everywhere for drivers, but could not find anything. Any help?  Thanks


I have seen related questions been asked on this forum, but none of them actually reached the point I would like to be clarified. From my perspective, every single non-math/logic question is opinion-based. In some cases, that opinion will be strongly backed by evidence. In others, it will be an intuition with not too much justification. However, there is always a chance of every answer being wrong (the only verifiable truth is, as Descartes put it "cogito, ergo sum")  My question would then be "where's the barrier?"? How certain does science have to be about an answer in order to stop being opinion-based. Let's show a few examples:  First, our all time favourite: a code question I posted myself on stackoverflow:  In this thread, I am asking for a way of writing a "Python list with labels", this means, a "Python dictionary", but there are other ways to achieve the same goal. Most people would not say this should be put on hold as opinion-based, but in that case... Why should the following question?   This question was posted on the chess forum. For those who may not be familiar with chess, the asker wants to build an "opening repertoire", so, he wants other users to help him find the most adequate answers to the opponent's first moves. But there is no such thing as the most adequqate answer! There are many possible ways to reach a good position, just as in my previous question. So, yes, the answers to this question are purely opinion-based and it was put on hold.  However,  this quedstion is asking basically the same thing, except it a different position. As before, there is no final answer, and indeed we see different people giving different pieces of advice. The question was not put on hold and it even received 4 upward votes.  Just in case you know nothing about either Python or chess, here are a few examples of questions that could be opinion-based (or not)                  In short, my point is that opinion-based judgements are purely a matter of opinion and this should not be a reason to put on hold so many questions,at least, not in every community. I understand I could be wrong and that's why I ask you: "Where is, in the Stack Exchange world, the border between a fact and an opinion?" Please don't put on hold as opinion-based!

On Stack Overflow at the moment, there is a popular question which is currently high in the Hot Questions feed:   So far it has been closed twice (once by the community and a moderator and once by a moderator alone) but re-opened twice by the community. It is clearly not a [so] Stack Overflow question. Reading between the lines, there could be a valid Software Engineering question there, but it would be a very basic one (at the fizz-buzz competency level) and looks more like a populist attempt to farm reputation than a serious question.  Worst of all, even though there are some interesting answers on this question, they are all going to be completely useless to future visitors to the site, since they will be completely undiscoverable. If the question were at least "What is the best fair distribution algorithm?" it would still be off-topic (primarily opinion based), but at least it might help someone once the topic falls off the Hot Questions feed.  Although this has turned into just a bit of fun, and I don't want to kill that, enough is enough. While this question is open, unlocked, and still seen as a valid question, it is setting a bad example for the whole Stack Exchange network.   questions like this, especially on the grandfather Stack Exchange site, devalue the work we are putting in on every other site by making it appear acceptable to re-open populist questions like this after two moderators have classified it as off-topic.  What should we do about this question?   Should it be left open? Power to the people? Closed and locked by a moderator? Migrated to another site? …or something else?


Is there any way to get a total of all questions on a given site that have been closed for each reason? E.g.,   123 duplicate 456 OT 789 too broad   Bonus points if OT is separated by its reasons.

Are there any stats about the percentage of close reasons used to close questions   Successfully (preferably, based on the number of closed questions) Unsuccessfully (alternatively, the total percentags of close votes cast by users)   ?   Is there any way to get this from the query explorer?


I attempted to season my new carbon steel wok using an outdoor gas fryer, which worked great for turning the metal the proper blue color. Unfortunately, for the seasoning step, I put too much canola oil on the wok, and now the center has a black film that cannot be easily scraped off. I've seen conflicting advice for how to remove it. Should I simply put the wok back on the fryer and re-heat to bake everything off, and then re-season?

After reading , I want to try to re-season a skillet with flaxseed oil; I'm fairly certain I did a terrible job when I seasoned the skillet several years ago. Is it possible to do this with steel wool or vinegar? (I don't have a self-cleaning oven, so that method is out.)


My server runs Ubuntu 12.04.5 LTS. I try to keep it up to date as possible by doing  sudo apt-get update && sudo apt-get upgrade regularly. So far I was assuming that this would update the kernel as well. Today I noticed however that I am running a totally outdated kernel (uname-r gives 3.2.0-77-generic).   Doing sudo apt-get dist-upgrade didn't fix this. Then I tried sudo apt-get install linux-generic linux-headers-generic linux-image-generic - also with no success...  Why am I not receiving the latest kernels and how can I fix this?

I am currently using Ubuntu 12.04.2 32bit. I installed it using LiveCD.  Tomorrow, 23rd August 2013,Ubuntu 12.04.3 is released. I want to upgrade from Ubuntu 12.04.2 to Ubuntu 12.04.3 without using any LiveCD. Is it possible? If so please suggest me how can I do.  Actually while using Ubuntu 12.04.2 I have troubled with graphics. My graphics card is Intel i845G 64 MB. When Ubuntu starts it works fine and smooth without any lagging, but after sometime it hangs for few seconds (1 or 2 seconds) with a garbage screen and becomes sluggish. All windows and browsers start lagging and also it is not possible to play any video in any player (VLC, Movie Player, Xnoise, SMPlayer etc..).  I think Upgrading to Ubuntu 12.04.3 could fix my problem.  Any help will be greatly appreciated..    I've posted an answer to upgrade Ubuntu 12.04.x to 12.04.4.


My /dev/sda6 says I only have 4.7G available but still use% is 99? It does not make sense. Can someone help me with this? waybackdrm@dolansroadbike:~$ df -h Filesystem      Size  Used Avail Use% Mounted on udev            3.8G     0  3.8G   0% /dev tmpfs           784M  2.5M  781M   1% /run /dev/sda6       260G  242G  4.7G  99% /  I try the following: sudo apt-get autoremove sudo apt-get clean  doesn't seem to do anything? Any feedback? also let me know if I need more screenshots?

The main question is how to make space in root (/). After this I want to resize the root partition, this topic can be found on:  or elsewhere.  I'm a little bit confused. No command seems to work for there is no space. I tried some random easy-way solutions but the problem persists. Here is the description of what I did:  1) It started giving me advices of “Little space on root, try uninstall software”  2) I removed some, and the Software Update continued working.  3) Eventually the root filled and now and for over two weeks the update software isn't working. I forced to upgrade with sudo apt-get update and sudo apt-get upgrade and not working. It gives me this message (auxiliar repositories):    4) At some point I tried to do some random reading on forums and enter command like this: sudo apt-get clean  and gave me a file in: /var/cache/apt/archives/lock.txt and problems with dependencies, repositories and dpkg.  5) When I run sudo apt-get -f install this is the current exit:  $$$$$$$$:~$ sudo apt-get -f install [sudo] password for $$$$:  Leyendo lista de paquetes... Hecho Creando árbol de dependencias Leyendo la información de estado... Hecho Corrigiendo dependencias... Listo Se instalarán los siguientes paquetes extras:   linux-headers-3.13.0-61 linux-headers-3.13.0-61-generic Se instalarán los siguientes paquetes NUEVOS:   linux-headers-3.13.0-61 linux-headers-3.13.0-61-generic 0 actualizados, 2 se instalarán, 0 para eliminar y 60 no actualizados. 2 no instalados del todo o eliminados. Se necesita descargar 0 B/9.575 kB de archivos. Se utilizarán 76,5 MB de espacio de disco adicional después de esta operación.    ¿Desea continuar? [S/n] s dpkg: aviso: falta el fichero de lista de ficheros del paquete "gnome-power-manager", se supondrá que el paquete no tiene ningún fichero actualmente instalado dpkg: aviso: falta el fichero de lista de ficheros del paquete "qtdeclarative5-qtfeedback-plugin:i386", se supondrá que el paquete no tiene ningún fichero actualmente instalado dpkg: aviso: falta el fichero de lista de ficheros del paquete "libio-string-perl", se supondrá que el paquete no tiene ningún fichero actualmente instalado (…) And continues with 2369 problems like this (all packages not found?)  6) Over this point I realized I had the root full and needed to liberate space and maybe extend the size of partition, for which I read I will need some 200 MB of free space. I don't remember how but I entered two commands that told me how much used/total space I had, noting it was full.  7) And now when I try to not mess with commands I don't really know (late), trying to uninstall software gives me this exit:  $$$$$$$$$:~$ sudo apt-get --purge remove openshot [sudo] password for $$$$: Leyendo lista de paquetes... Hecho Creando árbol de dependencias Leyendo la información de estado... Hecho Tal vez quiera ejecutar «apt-get -f install» para corregirlo: Los siguientes paquetes tienen dependencias incumplidas:  linux-headers-generic : Depende: linux-headers-3.13.0-61-generic pero no va a instalarse E: Dependencias incumplidas. Intente «apt-get -f install» sin paquetes (o especifique una solución).  Any suggestions? I have installed programs not found on Software Center and took me some time and effort, I would like not to format or reinstall Ubuntu if possible. Thanks in advance.


I am creating a website with web apps within it.  I am now at the stage where I am using phonegap to turn the web apps into mobile apps, but for that I need to make a branch for each app which has the app's directory as the root.  How do I go about creating a branch with a sub directory as the root?  root directory -> app 1 -> app 2

I have a  repository which contains a number of subdirectories. Now I have found that one of the subdirectories is unrelated to the other and should be detached to a separate repository.  How can I do this while keeping the history of the files within the subdirectory?  I guess I could make a clone and remove the unwanted parts of each clone, but I suppose this would give me the complete tree when checking out an older revision etc. This might be acceptable, but I would prefer to be able to pretend that the two repositories doesn't have a shared history.  Just to make it clear, I have the following structure:  XYZ/     .git/     XY1/     ABC/     XY2/   But I would like this instead:  XYZ/     .git/     XY1/     XY2/ ABC/     .git/     ABC/


There is a list of dates in the form of array list Example :  11/02/2012 21/04/2019 12/03/2061 11/09/1961 22/08/2014  We will have to return the third latest date from the above list  I feel we will have to first sort in descending order of year and take the third latest date from that  Could you please give me a suggestions on this?

I need a good explanation (references are a plus) on Python's slice notation.   To me, this notation needs a bit of picking up.   It looks extremely powerful, but I haven't quite got my head around it.


I know "I know about him" but don't know "I know of him"  Question is: I know of him. What does this mean or imply? PS. think of vs know of is a totally different phrase

Could someone help me to understand when I should use think of and when think about in sentences?  What is the difference between using one or the other?


After trying to install WINE from the WINE HQ .deb, I can no longer get updates or install apps without getting the message:  E: Malformed entry 55 in list file /etc/apt/sources.list (Component) E: The list of sources could not be read.  This is Kubuntu 18.04 64 bit.  I don't know what the 55 refers to, as there are fewer than 55 sources in the list. I've noticed the file sources.list.save is slightly longer than the file sources.list, but don't know whether switching these files will damage anything. I don't see where I can attach the working file (assumption on my part) in case it's needed for review. Please let me know what other information I can provide to help solve this problem.  Thanks, I didn't see where I could edit the question. Here goes...  # deb cdrom:[Kubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725)]/ bionic main multiverse restricted universe  # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://us.archive.ubuntu.com/ubuntu/ bionic main restricted # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic main restricted  ## Major bug fix updates produced after the final release of the ## distribution. deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ bionic universe # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic universe deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates universe # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates universe  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu  ## team, and may not be under a free licence. Please satisfy yourself as to  ## your rights to use the software. Also, please note that software in  ## multiverse WILL NOT receive any review or updates from the Ubuntu ## security team. deb http://us.archive.ubuntu.com/ubuntu/ bionic multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic multiverse deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates multiverse  ## N.B. software from this repository may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse  ## Uncomment the following two lines to add software from Canonical's ## 'partner' repository. ## This software is not part of Ubuntu, but is offered by Canonical and the ## respective vendors as a service to Ubuntu users. # deb http://archive.canonical.com/ubuntu bionic partner deb-src http://archive.canonical.com/ubuntu bionic partner  deb http://security.ubuntu.com/ubuntu bionic-security main restricted # deb-src http://security.ubuntu.com/ubuntu bionic-security main restricted deb http://security.ubuntu.com/ubuntu bionic-security universe # deb-src http://security.ubuntu.com/ubuntu bionic-security universe deb http://security.ubuntu.com/ubuntu bionic-security multiverse # deb-src http://security.ubuntu.com/ubuntu bionic-security multiverse deb https://dl.winehq.org/wine-builds/ubuntu/ bionic main deb http://archive.canonical.com/ubuntu bionic multiverse deb-src http://archive.canonical.com/ubuntu bionic multiverse deb https://dl/winehq.org/winehq.org/wine-builds/ubuntu/bionic main # deb-src https://dl/winehq.org/winehq.org/wine-builds/ubuntu/bionic main # deb-src https://dl.winehq.org/wine-builds/ubuntu/ bionic main

I have unistalled and reinstalled the Ubuntu Software Center as per info I found in a similar thread and I got the same response about line 91 or something like that.  I just tried to upload a screen shot but since I'm new it won't allow me to.  I also can not figure out how to cut and paste anything so I have to hand type what the error screen says, both when I attempt to open the software center and nothing happens, when I try to enter commands into the terminal to uninstall, reinstall, whatever I get the same following:  COULD NOT INTITIALIZE THE PACKAGE INFORMATION An unresolvable problem occured while initializing the package information Please report t:his bug against the 'update-manager' package and include the following error message: 'E: Malformed line 91 in source list/etc/apt/sources.list (dist parse)  E: The list of sources could not be read.,  E: The package list of status file could not be parsed or opened.   How do I report bugs?  What can be done about this.  I have searched and everything everyone says to do leads me back to the same line error message.  So, I don't know how to get to line 91 in the source list; to tell you what it says. Sorry, I'm really new to this. That is what I need is to find out how to get there and fix what it says. I would really like to NOT have to re partition my hard drive and start from scratch, so I'm really looking forward to getting this problem solved. I need to be able to install new software.


Here's bold text on its own:     strong text   Here's bold text not on its own:     strong text strong text   Can we fix this?

I am trying in one of my posts to do this:  ***how many*** **and** ***where***   Which for some reason comes out like this:    Why is that happening?  Shouldn't the middle word be bold?  Is this  for markdown or is it (as I assume) a ?


Is "I want to learn how to swim" the right expression, or should I have said so: "I want to learn to swim."?

"learn to [verb]" "learn how to [verb]"   Is [1] merely a less formal version of [2]? If not, does [1] communicate something subtly different? Consider the following:  In [2], the object of learning is explicitly "how to [verb]" (for instance, "I will learn how to speak French").  Is the object of learning in [1] "to [verb]" or is it something implicit and abstract that allows the subject "to [verb]"? For instance, in "I will learn to speak French", the object of learning would be the prerequisite elements for speaking French: "French phonemes, grammar, syntax, etc.".


I've been trying to export a few map layers using QGIS print composer. First, I loaded the layers and opened the composer using Project -> New Print Composer:    Gave it a proper name:   Added a new map:   Exported as image:   However, the outcome is shifted a few dozens of kilometers westwards:   This specific west shift is inconsistent; sometimes I experience a smaller shift or a shift in another direction. Moreover, the scale often changes too - which makes map exporting impossble.  I'm using the newest QGIS version:   Any idea how to export the image properly? I'm currently using screenshots, which are a poor solution.

I'm having trouble with the OpenLayers Plugin of Qgis and the map composer:  If I create an OSM-background layer and if I want to export this, the OSM-Layer looks perfectly all right in the normal qgis program window. But in the map composer and after export the layer has shifted relatively to my other shape layers (EPSG:32633 - WGS 84 / UTM zone 33N).  The second thing is that the output resolution of the exported osm-layer is very, very poor.   A really bad way of getting around this whole trouble would be to increase the screen resolution and make a screenshot of the map composition window of qgis. But I don't think this would be very professional. It also would cause a lot of pain :)   I'm using Qgis 1.8.0-Lisboa under Linux. The openlayers plugin is version 0.92.