I will be going on vacation in a couple of days to the beach. I plan to leave my computer (a mid 2012 Mac) in the car, which will possibly be exposed to the sun.   It will be exposed between 14:00 and 20:00 and during this time temperatures can get as high as 38 degrees Celsius (100 Fahrenheit). Will this be a problem? Will I risk ruining the battery / computer?   What precautions can I take? For example, is it better to leave in the trunk or in the back seats? Should I turn it off? (usually I just close the lid)   Thank you in advance!

It's now summer around here, with temperatures ranging from 20C to 30C in the summer. Occasionally, I have a situation where I can carry my laptop indoors, or just leave it in the car for a few hours.  My question is: will it cause any sort of damage if I leave it in the car for several hours? I usually bring it indoors just in-case, but I thought I'd ask. Note that the laptop is always off at this time.


Is  __init__.py file is a module ? I am learning python and come across packages and modules and i have one doubt that weather __init__.py file can be consider as module Since every python file is module so can we consider __init__.py as module ?

What is __init__.py for in a Python source directory?


I'm trying to write something like this: \begin{itemize} \item \(x^2+y^2-1=0; \quad\quad\quad\) (ellipse) \item \(x^2-y^2-1=0; \quad\quad\quad\) (hyperbola) \item \(x^2-y=0; \quad\quad\quad\) (parabola) \end{itemize}  I'm struggling to find out how to make it right without using all those \quad and aligning the captions. Thanks in andvance 🥺

I want to describe the variables involved in an equation in an itemized environment such that every item begins with the variable name and subsequently comes the description for it. I'd like to have all the descriptions left aligned.  Here is a MWE that of course does not produce what I am looking for.  \documentclass{standalone} \begin{document} $E[g(x)] = \int_{-\infty}^{+\infty} f_X(x) \, g(x) \, \mathrm{d}x$. % where, % \begin{itemize}     \item $x$      \quad is a continuous random variable.     \item $f_X(x)$ \quad is the PDF of $x$.     \item $g(x)$   \quad is a function of $x$. \end{itemize} \end{document}


I want to turn off two factor sign in for Apple ID. I do not see that I have that option this time. It used to be that I would be sent a email letting me know it was activated and it had a option to go back to previous settings. This time I did not get a email like that. I do have that I want to recieve the information from Apple all check marked.   Is it possible? How

Is it possible to turn off the Two-Factor Authentication for an Apple ID?  I have more than one device linked to this Apple ID and I know the password and security questions.


Just me, a schizophrenic and a petty arsonist.   How many people are there in the above sentence? Is it ambiguous?

According to the Wikipedia page for the , "Use of the comma is consistent with conventional practice" and "Use of the comma is inconsistent with conventional practice." Did the Oxford Comma come before its omission, or was the Oxford Comma traditionally omitted?  It makes logical sense that every item in a list would be separated in the same way: by a comma. If the Oxford Comma is conventionally correct, when and why did people begin to omit it?


Anyone know how I can enable the WYSIWYG editor for the textarea summary field in D8? I have a "body" field on my news content type set to "Text (formatted, long, with summary)" but only the main textarea gets the WYSIWYG editor while the summary field is just a standard textarea.    The summary field does support rich text, presumably using the same text format as the main textarea, but it's not clear since CKEditor is not there.  Note there's a similar question asked but it's from 2011:

Is there a straightforward way to change the summary/trimmed text to "full html" in Drupal 8?  There are workarounds such as creating separate body fields and using them as the summary but I am specifically asking about changing the text format of default summary/trimmed field of "Text (formatted, long, with summary)".  To put it another way, how to I add the CKEditor bar to the summary/trimmed text.


How to add an item on the third column? I have a code but it only adds an item upto the second column.  lstProjectFiles.Items.Add(f3.FullName).SubItems.Add(f4.FullName);

To add items to column 1 in my listView control (Winform) I'm using listView1.Items.Add, this works fine but how do I add items to columns 2 and 3 etc?


How in Linux using cp one can copy file to destination, but if destination exists, then overwrite only if destination is older than source?  cp -f always overwrites, but overwrite is needed only if target is older than source.

How do I copy a file in Linux only when the file being copied is newer than the version at the destination?  If the file at the destination  is newer, I want the file copy to not go ahead.


Hey Guys I am using the cas-dc DocumentClass and I would like to use sort&compress from natbib with my citation. According to there guiedlines I can use \biboptions{sort&compress} but that dos not work as \biboptions is not recognized. The download is here: mirrors.ctan.org/macros/latex/contrib/els-cas-templates.zip In case someone needs it. Anyone know a solution for that problem

I have been using elsarticle.cls  for most of my work. Now I am trying to take those papers and put them into a thesis, using a thesis template given by my school. The elsarticle says in the preamble  %% natbib.sty is loaded by default. However, natbib options can be %% provided with \biboptions{...} command. Following options are %% valid:  %%   round  -  round parentheses are used (default) %%   square -  square brackets are used   [option] %%   curly  -  curly braces are used      {option} %%   angle  -  angle brackets are used    <option> %%   semicolon  -  multiple citations separated by semi-colon (default) %%   colon  - same as semicolon, an earlier confusion %%   comma  -  separated by comma %%   authoryear - selects author-year citations (default) %%   numbers-  selects numerical citations %%   super  -  numerical citations as superscripts %%   sort   -  sorts multiple citations according to order in ref. list %%   sort&compress   -  like sort, but also compresses numerical citations %%   compress - compresses without sorting %%   longnamesfirst  -  makes first citation full author list %% %% \biboptions{longnamesfirst,comma}  \biboptions{sort&compress}   Since I am using the mitthesis.cls instead of elsarticle.cls now, I tried to load natbib using:  \usepackage[numbers]{natbib}   This seems to work (I think?), but if I try to use \biboptions{sort&compress}, I get an error:  Undefined control sequence \biboptions   Any ideas on how to get \biboptions{sort&compress} to work?   Also, am I loading natbib correctly (I want to use a numbered bibiliography style like \bibliographystyle{model1a-num-names}).


For technical reasons that I cannot change my computers at home are located behind two routers, only one of which (the one connecting my own network) I have control over.  Basically the setup is  Internet <-> R1 <-> private network 1 <-> R2 <-> private network 2  R2 is my router. The private networks are 192.168.10.0 and 192.168.1.0. The latter is mine.  Is there any way for me to reach my computer from the outside (i.e. the Internet)?  I am not adverse to renting a hosted server somewhere and run some sort of client on a computer inside my network to allow the hosted server to SSH to my home network.  Any ideas?

I would like to access the ssh port of my office linux host from home. Unfortunately the host is located behind a NAT router. So, the IP address is not publicly available. There is however access to another internet host (Server) which is unfortunately only non-root access. After a while of searching I do not find a suitable solution.  Following setup:   Office PC (linux, root access) behind NAT (IP not public) but full Internet access. Server PC (linux, no root access) static and public IP and full Internet access. Home PC (linux, root access) behind NAT (IP not public) but full Internet access.   Possible connections: Office PC --> Server <-- Home PC  Not possible: Office PC <-X- Server -X-> Home PC  Neither the Home PC, nor the Server can initiate access to the Office PC. But both the Office PC and the Home PC can initiate connections to the Server.  Reverse SSH tunnel not possible: I tried a method called reverse ssh-tunnel. Unfortunately this requires GatewayPorts on Server set to "yes" in /etc/ssh/sshd_config, where I have no root access.  In principle it should be possible:   0) On the Server I start a userspace program which listens on 2 ports (1 incoming, 1 outgoing)  1) On my office PC I run a another program which keeps a TCP connection open to the outgoing port on the server.  2) From home I connect to Server's incoming port.  There should be a standard solution for this out there.  What is the quickest and cleanest solution to solve this?  Frank


How do I hide the Notification Center menubar icon? Is it possible to do what was done here, for the Spotlight icon?

I am using Mountain Lion.  The only advantage (for me) over the gesture is that Option + clicking the button enables/disables showing alerts and banners (toggles the switch in the notifications center).  Is there a way to hide the button in the status bar that opens notification center?


Is it possible to check if a number is NaN or not?

Is there an isnan() function?  PS.: I'm in  (if that makes a difference).  I had this solved by using isnan() from <math.h>, which doesn't exist in <cmath>, which I was #includeing at first.


I wanna ask you ,  do you have a solution for this question (if statement) or where is the error ?   String z = input.nextLine() ;  //i want from the user value of z  . if (z ==( "Y" || "y" ))  {       statement ...  }      else if (z==("N" || "n" ))     {       statement ...  }   How to write a condition for if when the condition of String in Java  ?

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


Hello everyone, I have a problem with the GPU (msi radeon hd 7870 2gb oc edition), practically in some scenes the rendering with the gpu form some black parts, which are not shown if I render the same scene with an xfx rx 480. What could be the problem?  I installing Blender version 2.77 as user Mike Pan said, and the problem is solved.

In the settings I can't choose another device to render other than the CPU.     According to the blender wiki the GPUs "with a GCN Architecture superior or equal to 2.0 are supported".     And as I understand my GPU (R9 270) should be supported, according to this table from wikipedia(and has GCN 2.0 and up):   Or am I wrong and my GPU isn't actually supported? :(   GPU:    R9 270 (latest drivers)  OpenCL version: 22.19  Blender version: 2.79


For some years now, I've been contributing the maximum amount to my personal IRA ($5,500 in 2015) and my 401k ($18,000 in 2015). This, plus employer match, means I am saving about $30,000 per year in a tax-advantaged account.  Now I am considering switching jobs, but they don't have a 401k plan. Do I have any options other than just a standard investment account with 15% capital gains tax? Would it help if I set up self-employment and contracted myself?

I'm considering moving to a new job that doesn't have any sponsored retirement plans.  I'd like to continue saving on my own though, but it seems that IRAs have a $5,000 contribution limits.  What are some other options to save in addition to an IRA?  I'm not interested in the obvious "put more into your bank savings account," I'm looking for options fairly close to an IRA (trading stocks on etrade also out) to save more.  Also, would contributions to the 401k prior to rolling into an IRA count against the contribution limit to the IRA?


So basically it is like a PHP game, where you have garage and when you buy cars they go to that garage and there is a list of them in there, also there is a button with url http://localhost/garage?active=58(58 being a car ID.) this button switches car and makes it active, you can race using that car with other people. HOWEVER, when you add a weird symbol to the url (ex.:active=58@) , it deactivates all cars, because php code stuck at:   Here, it does not recognise the car id and stops here:  $setinactive = mysql_query("UPDATE user_cars SET active='No' WHERE userid='$userid' and carid='$activenow'");    When without symbol, it ordinary proceeds to this line and sets choosen id car active:  $setactive   = mysql_query("UPDATE user_cars SET active='Yes' WHERE userid='$userid' and carid='$carid'"); }   I know its bad coding, but is there any simple fix to this?

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


Just like the title states, I'd like to switch from Survival Mode to Creative. Is that possible?

This question is regarding the minecraft Beta 1.8 prerelease -- I have a beautiful house in single player survival which I'd like to record while flying.  I want to be able to change the game mode of my survival map to creative to be able to fly through it without installing a mod. I know it is possible if you run the map on a multiplayer server via the command /gamemode <user> 0|1 but I want to achieve this in single player :)  I think this would be possible through editing your level.dat file as I think that's where the game mode for the map is stored.


I need to Create a new user programmatically. So, I have used user_save method, as shown here:  $usersave = array( 'name' => 'abc', 'pass' => 'abc', 'mail' => 'abc@gmail.com', 'status' => 1, 'roles' => array(   DRUPAL_AUTHENTICATED_RID => 'authenticated user',       5 => 'customer' ), );  $save = user_save($usersave);   But it throws this error message:     PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '0' for key 'PRIMARY': INSERT INTO {users} (name, pass, mail, status) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3); Array ( [:db_insert_placeholder_0] => abc [:db_insert_placeholder_1] => abc [:db_insert_placeholder_2] => abc@gmail.com [:db_insert_placeholder_3] => 1 ) in drupal_write_record() (line 7383 of /home/vijay/public_html/vssb/public/includes/common.inc).   What's the issue?

I'm programmatically creating a user with the following code.  $newUser = array(   'name' => $mail,    'pass' => 'password',  // note: do not md5 the password   'mail' => $mail,    'status' => 1,    'init' => $mail,   'roles' => array(5) ); $user = user_save(null, $newUser);   I have got a role with the role ID equal to 5; when I create the user, in the table "users_roles" there is only a row with the value 0 for the role ID, but if I print the user object with var_dump(), it looks like the roles are created.  What am I doing wrong?


Many actions in combat (like making an enemy fall prone), can give an edge to your teammates (in this case, melee advantage) until the enemy's turn (in this case, he would get back up to end the condition). Such actions are the most useful when your turn is right after the enemy's turn, so that all of your teammates can benefit from the edge you give them.  Contrary to the Ready Action (which enables to delay an action to be made after a specified trigger), what I'm seeking here is for a character to delay his entire turn in the initiative order. Is such a thing possible ?  Example 1 : The initial order is Bob, Enemy, Friend 1, Friend 2. Bob wants to delay his turns in the initiative order to do as if his initiative roll had placed him right after "Enemy" in the cycle : Enemy, Bob, Friend 1, Friend 2.  Example 2 : The initial order is Friend 1, Friend 2, Bob, Enemy. Bob wants to delay his turns again, even if, this time, he won't do anything for the first round. The second round's order would then be : Bob, Friend 1, Friend 2, Enemy.

In D&D 4e there was an option to Delay your initiative:     Perform your actions as desired and adjust your initiative to your new   position in the order.   Does this rule to change initiative order still exist in 5th edition? I cannot find it in the PHB.


They travel at the same speed, why? Maybe they are the same thing, but seen from different perspectives.

I suppose there was a discussion already on .  But I silly wonder whether all the massless mediators of four fundamental forces, i.e.  Graviton: $g_{\mu\nu}$ (gravity)  Photon $\gamma$: $A_\mu$ (electromagnetism)  Gluons: $A_\mu^a$ (strong interactions)  Necessarily travel at the same speed? Is there a no-go theorem or theoretical proof to say that it is impossible to have these three mediators have different speeds?   Or does QCD confinement makes the story of gluons any different from gravitons and photons?  [ps. excluded massive $Z^{0}$ and $W^{\pm}$ bosons (weak interactions)]  Another way to say this: Speed of photon, graviton, gluon all equal to $c$? or  Whether all massless particles necessarily have the same speed?  Note add: Notice however, in condensed matter systems, there can be emergent gauge fields and emergent massless particles (Dirac or Weyl cones), but their speeds need not be the same, unless there is some emergent symmetry...


I'm learning to use MySQL at the moment and my instinct for instantiating and initializing my Connection and Statement objects was as following:  public class ProjectDriver {     public static void main(String[] args)     {         Connection conn = null;         Statement stmt = null;         Initializer.sqlInitialize(conn,stmt);     ...     } ... }   sqlInitialize:  public static void sqlInitialize(Connection conn, Statement stmt) {     try {         conn = DriverManager.getConnection(DB_URL, USER, PASS);         stmt = conn.createStatement();     }      catch (SQLException se) {         se.printStackTrace();     }      catch (Exception e) {         e.printStackTrace();     } ... }   as well as an sqlClose method to close the Connection and Statement later on.  My instinct says that the Connection and Statement objects in the ProjectDriver should be properly initialized to their respective forms after the sqlInitialize method has been run, but that most certainly isn't the case. Eclipse has a null-pointer access warning in the IDE, and a NullPointerException error is thrown upon trying to run stmt.ExecuteUpdate(sql);.  I'm pretty sure this is a stupid question, but I can't figure out how to Google (or inquire of StackOverflow) why this is happening. I know that the code I provided isn't really the proper way to do what I'm doing, but I'm curious as to why this is happening. My understanding of pass-by-reference vs. pass-by-value in Java is that all primitives are pass-by-value, and that all Objects are pass-by-reference. Shouldn't modifications made to the Connection and Statement objects in another class remain, even after returning to the main?

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


On the command line (usually bash, and somtimes zsh), I sometimes need to enter a password to authenticate myself. in fact, I need to do that several times a day. Sometimes, you fail typing and instead of hitting return (which is bad sometimes as it is recorded by the server) and type it another time, is there a shortcut (like Ctrl-R for searching the history) to wipe out the typed password and start anew?

One thing that annoys me using Linux's terminal is when I have to type a invisble password, like when you run ssh. Sometimes I mistype one or more letters and then I have to press backspace key a few times to make sure that I erased everything to start again.   I know this is not a big deal but since on the other day I found out that pressing CTRL+L "clears" the terminal I was wondering if there's a way to clear/erase the invisible password without relying on backspace or pressing enter key to try again.


Where do I find the polygon and vertices count for a specific object that I've selected in Blender 2.8? I'm looking for something like this:

Is there a way to get Statistic info in Blender? Or heads up display? Like when I select a group of vertices, I need a way to know how many vertices are selected and How many polygons "or triangles my scene has.


I have a blender that is not very powerful, just 400 Watt. I tried to use it with nuts and it cannot do it, I notice it suffers too much. If I add some water it works well and I like the result. My question is how much time will the cream last in the fridge?   What I have tried: - I tried to make just what I need for today. The blender needs more quantity to move everything. - I tried to add lemon. It seems to work with savory recipes but not if I want a sweet cream, sauce or spread.  If I make a cream, sauce or spread with nuts and a bit of water, how much time will it live well in the fridge?  None of the sources commented answers the question. It is known that nut butters have long shelf life as natural oils help to preserve them. The question here is if adding water can shorten the regular shelf life of a nut butter.

How do I know if a given food or ingredient I have is still good, or if I should discard it?  How can I best preserve a food or ingredient?     This broad question is intended as a "general reference" question to quickly answer many how long will food keep for? questions. Please feel free to edit this question to expand and clarify as needed.


I have been running Deepin for a while. I have enough space left to run Ubuntu and I would like to check it out. How can I accomplish that?

I would like to know how to install another distro side by side with Ubuntu 18.04.2.    Currently 18.04.2 resides on the entire hard drive.  Would I need to make another partition?  How would I go about doing this?  Would I be able to use the same GRUB menu?


I would like to know about package information as i have mentioned in my Question .   For example , There is a installed package in my system . So i want to know whether its a main package or dependency to some other package .  Thank you .

For a specific package, can I find out why it is installed?  So, can I see or it's manually installed, or that it is installed as a dependency of another package? Or that it is installed as part of the distro?


In Sean Carroll's book, last paragraph of page 160, this statement is found:     "The Riemann tensor is of course made from the second derivatives of the metric, and we argued earlier that the only independent scalar we could construct from the Riemann tensor was the Ricci scalar R. What we did not show, but is nevertheless true, is that any nontrivial tensor made from products of the metric and its first and second derivatives can be expressed in terms of the metric and the Riemann tensor. Therefore, the only independent scalar constructed from the metric, which is no higher than second order in its derivatives, is the Ricci scalar."   What is the detailed proof of this statement?

According to Section 6.2, Gravitation and Cosmology by Weinberg, the Riemann-Christoffel tensor is the only tensor that can be constructed out of the second (or lower) order derivatives of the metric tensor and is linear in the second order derivatives. The reasoning behind the same goes like this:   In a class of frames where $\Gamma^{\lambda}_{\mu\nu} =0$, the transformation rule for $\dfrac{\partial \Gamma^{\lambda}_{\mu\nu}}{\partial x^{\kappa}}$ involves an inhomogeneous term which is symmetric in $\mu$, $\nu$, and $\kappa$. Thus, if one is to construct a tensor which is a linear combination of the first order derivatives of the Christoffel symbol then the only way to do so is by eliminating the inhomogeneous part of the transformation and this could be done only by making the combination explicitly antisymmetric in $\mu$ and $\kappa$. Since in these frames, $R^{\lambda}_{\mu\nu\rho}$ $ = \dfrac{\partial \Gamma^{\lambda}_{\mu\nu}}{\partial x^{\rho}} -  \dfrac{\partial \Gamma^{\lambda}_{\mu\rho}}{\partial x^{\kappa}} $, $R^{\lambda}_{\mu\nu\rho}$ is the only tensor that can be formulated using the second (or lower) order derivatives of the metric tensor and is linear in the second order derivatives.  I think the presented argument can only suffice to prove that $R^{\lambda}_{\mu\nu\rho}$ is the only tensor that can be formulated from the first derivatives of the Christoffel symbol and is linear in them. I can't figure out why this suffices to assert that $R^{\lambda}_{\mu\nu\rho}$  is the only tensor that can be constructed out of the second (or lower) order derivatives of the metric tensor and is linear in the second order derivatives.  Edit: As the metric is covariantly constant, $\dfrac{\partial g_{{\mu}{\nu}}}{\partial x^{\rho}} = \Gamma^{\kappa}_{{\mu}{\rho}}g_{{\kappa}{\nu}}+\Gamma^{\kappa}_{{\nu}{\rho}}g_{{\kappa}{\mu}}$.  Therefore,   $\dfrac{\partial^2 g_{{\mu}{\nu}}}{\partial x^{\xi}\partial x^{\rho}} = \bigg(\dfrac{\partial \Gamma^{\sigma}_{{\mu}{\rho}}}{\partial x^{\xi}} + \Gamma^{\sigma_1}_{{\mu}{\rho}}\Gamma^{\sigma}_{{\sigma_1}{\xi}}\bigg)g_{{\sigma}{\nu}}+\bigg(\dfrac{\partial \Gamma^{\sigma}_{{\nu}{\rho}}}{\partial x^{\xi}} + \Gamma^{\sigma_1}_{{\nu}{\rho}}\Gamma^{\sigma}_{{\sigma_1}{\xi}}\bigg)g_{{\sigma}{\mu}} + \bigg(\Gamma^{\sigma}_{{\mu}{\rho}}\Gamma^{\sigma_1}_{{\nu}{\xi}}+\Gamma^{\sigma}_{{\nu}{\rho}}\Gamma^{\sigma_1}_{{\mu}{\xi}}\bigg)g_{{\sigma}{\sigma_1}} $  Now, if I want to show that the Riemann-Christoffel tensor is the only (non-trivial and independent) tensor that can be formulated out of the linear combinations of the second order derivatives of the metric tensor then I can equivalently show that the above expansion can be expressed linearly in terms of the Riemann-Christoffel tensor. But I am stuck over how to do it. Also, I am a little bit unclear as to what a linear combination means in this context. The coefficient of the second order term can be only a scalar constant or can it be the metric or can it be the metric that is getting summed over any of the indices as well?


The exercise is given as follows "If we take the integral domain $\mathfrak{D}$ consisting of all polynomials $a_nx^n+...+a_1x+a_0$ with integral coefficients, under ordinary addition and multiplication of polynomials, describe the quotient field of $\mathfrak{D}$" Now here is what I did until the moment, first let $\mathfrak{D} = (\mathbb{Z}[x], +_d,\times_d)$, where $\mathbb{Z}[x]$ is the set of all polynomials with coefficients in $\mathbb{Z}$ and $+_d$, $\times_d$ are the addition and multiplication of polynomials. Let $W = \mathbb{Z}[x]\times\mathbb{Z}[x] - \{0_d\}$, where $0_d$ is the zero polynomial in $\mathbb{Z}[x]$, then for any $(x,y)$ and $(u,v)$ in $W$ we establish the relation $\sim$ such that $(x,y)\sim(u,v) \Leftrightarrow x \times_d v = y \times_d u$ Then we let $F = \{[(x,y)]_\sim : (x,y) \in W\}$, that is, $F$ is the set of all equivalence classes given by the relation $\sim$ on $W$, now for any $[(x,y)]$ and $[(u,v)]$ in $F$ we can define $[(x,y)] +_F [(u,v)] = [((x \times_d v) + (y \times_d u), y \times_d v)]$  and $[(x,y)] \times_F [(u,v)] = [(x \times_d u, y \times_d v)]$ Then $\mathfrak{F} = (F, +_F, \times_F)$ form a field, which is the quotiet field of $\mathfrak{D}$. I already know that following those steps from a given integral domain, I will have a field, but I think the author of the book want something more, I tried to think about this structure but I just can see obvious thing which is clearly by definition, for example, the elements of our set $W$ is ordered pairs of polynomials where the second is different from zero, and the elements of $F$ are sets of elements of $W$. Well, the next question ask me to show that the quotient field of a field is isomorphic with the field itself, maybe the field $\mathfrak{F}$ on the previous question which is the topic of my post is isomorphic with some specific kind of structures, but I dont know yet, I got stucked because the author asked to 'describe' the quotient field, its different from all other his questions where he ask to prove/show something. There is a way to properly describe this specific field? Any property about this specific field will be appreciated also.

Let $\mathbb{Z}[x]$ denote the ring of polynomials (in the formal variable $x$) with integer coefficients. Since $\mathbb{Z}[x]$ is an integral domain, we can form its field of quotients, call it $Q.$  Is there a nice description of $Q$? I don't think $Q = \mathbb{Q}((x)),$ or in other words I don't think $Q = $ the set of all formal Laurent polynomials with rational coefficients, because for example I think that $$\sum_{n=0}^\infty \frac{x^n}{n!} \notin Q.$$


Type 1 :  class Demo(object): """docstring for Demo"""     def __init__(self, arg):         super(Demo, self).__init__()         self.arg = arg   or Type 2 :  class Demo(object):     def __init__(self, arg):         self.arg = arg   I have used Type 2 and i have no doubts in it.what does super(Demo, self).__init__()  mean in Type 1 ? and What does it do ?

I'm trying to understand the use of super(). From the looks of it, both child classes can be created, just fine.   I'm curious to know about the actual difference between the following 2 child classes.  class Base(object):     def __init__(self):         print "Base created"  class ChildA(Base):     def __init__(self):         Base.__init__(self)  class ChildB(Base):     def __init__(self):         super(ChildB, self).__init__()  ChildA()  ChildB()


Let's say I didn't know that if a sequence $\{a_n\}$ converges to some number $a$, then all subsequences of $\{a_n\}$ also converge to $a$.  I want to show using the definition of convergence that if $\{a_n\}$ converges to $a$, then $\{a_{n+1}\}$ converges to $a$.   Since $\{a_n\}$ we have for all $\epsilon > 0$, there exists a natural number $N$ such that for all $n \in \mathbb{N}$ $$n \geq N \implies |a_n - a | < \epsilon$$ I'm aware that some books use $n > N$, but this one uses $n\geq N$. Since it doesn't matter, let's stick with $n\geq N$ to be consistent =)  Clearly $n+1 > n \geq N$, so I should be able to deduce from the above implication that  $$|a_{n+1} - a| < \epsilon$$ But I have some doubts. My main question is if I pick any index $m > n$, will I be able to immediately conclude that  $$|a_m - a| < \epsilon$$ In other words, picking an index m > n allows me to "update" the index in $|a_n - a| < \epsilon$ to $|a_m - a| < \epsilon$?

I want to prove the following theorem     Let $\{a_{n}\}$ be a convergent sequence. Prove that $\lim\limits_{n\to \infty}a_{n+1}=\lim\limits_{n\to \infty}a_{n}$   Do I need to show that it is monotone increasing and then use the relation  $$0\leq \lim_{n\to \infty}a_{n+1}- \lim_{n\to \infty}a_{n}\leq 0 \;?$$  Please, I need help on this! Various proofs are welcome! Thank you very much for your time!


Many thanks for the free service on OpenShift.  I am using Gandi for my domain - www.something.io (₁), something.io (₂). I am trying to achieve the following: Have domains ₁ and ₂, redirect to nodejs-something.rhcloud.com without having the rhcloud domain in the address bar. I am aware of masked forward but wouldn't that display the rhcloud domain name? Why is forwarding the naked name so problematic?    The below works fine for www.something.io only:  something.io 3600 IN CNAME nodejs-something.rhcloud.com. www 3600 IN CNAME nodejs-something.rhcloud.com. www.something.io 3600 IN CNAME nodejs-something.rhcloud.com.   something.io displays:  Apache/2.2.15 (Red Hat) Server at nodejs-something.rhcloud.com Port 80   after I setup forwarding in Gandi from *.something.io to www.something.io. It wouldn't even take me to something.io if I didn't, that is, it ignored my rule in the zone file above.  I really wish this was a bit more simple.  I am very new to this so I would appreciate any help.

Is it possible to set a CNAME record at the top of a domain? (i.e. @ CNAME www, @ CNAME foobar.com., etc.)  My ISP says that it's only possible to use CNAME's for subdomains but I've read somewhere else that is should be possible even if not recommended.


I recieved a freezer full of frozen meat is beef or pork is still good if frozen for 4 years. never unfrozen still in package from store


We have to find the summation of the finite series $$\sum_{k=0}^{n}k \cdot {2n \choose k} .$$ Now notice that, if the sum was $~~\sum_{k=0}^{n}k \cdot {n \choose k} ~~$ then we take $~f(x)=(1+x)^n~$ and then do derivative on both side after taking the corresponding binomial expansion. But how should I approach for the given series $~~\sum_{k=0}^{n}k \cdot {2n \choose k} .$. Please help me to solve this.

I need hint proving this $$\sum_{k=0}^{n}\binom{2n}{k}k=n2^{2n-1}$$


I'm making a camera board using . For this sensor you need 3.3V analog power supply and 1.8V, 1.2V digital power supplies. Also, the 1.8V power pins are close to the 3.3V analog pins. Thus I'd like to use ferrite bead to prevent noises in 3.3v rail generated by 1.8V digital power rails. But I have no idea what kinds of ferrite beads would be appropriate for this.   DC resistance : Should it be as small as possible? impedance at each frequency: Should I look at impedances at 1Mhz, or 100Mz?   I'm going to use  as 1.8V power supply. It's a switching regulator and has 2.25Mhz switching frequency. I wonder how you predict noise frequency, or if the 100Mz is general for noises in power rails.

I want to put a ferite bead on positive SMPS supply rail that goes to analog part of the mixed digital/analog circuit.   Now on parametric search at Digikey I can see several parameters: Current rating, DC resistance, Impedance @ frequency. I understand current rating and dc resistance, I understand impedance, but how do I make my choice - should I look for the greatest impedance @ 100MHz with acceptable DC resistance and current ratings for my application?


So I just installed Ubuntu 18.04 desktop alongside Windows 10.  But despite the fact that the password I typed is correct, I still get prompted by this message.  $ lsusb Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 003: ID 0bda:b009 Realtek Semiconductor Corp.  Bus 001 Device 002: ID 05c8:03ab Cheng Uei Precision Industry Co., Ltd (Foxlink)  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub  $ iwconfig lo        no wireless extensions.  wlo1      IEEE 802.11  ESSID:off/any             Mode:Managed  Access Point: Not-Associated   Tx-Power=20 dBm              Retry short limit:7   RTS thr=2347 B   Fragment thr:off           Power Management:off  eno1      no wireless extensions.  $ lspci -knn | grep Net -A3; rfkill list 02:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. Device [10ec:d723]     Subsystem: Hewlett-Packard Company Device [103c:8319]     Kernel driver in use: rtl8723de     Kernel modules: rtl8723de 0: hci0: Bluetooth     Soft blocked: no     Hard blocked: no 1: phy0: Wireless LAN     Soft blocked: no     Hard blocked: no

Your situation   You have successfully installed Ubuntu.  You have just downloaded and booted Ubuntu live media.  The latest LTS (see also ) or latest non-LTS release are preferred. See the list of  that are currently supported.) You upgraded your Ubuntu installation to the latest release that the software updater offered you. WiFi worked before, but not now on the new release. You  to new hardware.   Your problem   The wireless of your laptop or desktop is not working. You tried switching the wireless switch off and on and you tried rebooting several times, but you don't see any WiFi access points. You can see your wireless access point, but you cannot establish a connection. You want to analyze the problem, but you don't know where to start or what information you can provide.   This question and answer was written to give people the wireless script that will provide the information needed in most cases to diagnose their wireless issue's.   Related questions


I wanted to create a LEGO landscape based on the LEGO Movie's way of doing it. I've tried turning a LEGO fluid simulation from a tutorial into a stagnant landscape, without any results. Here is an example picture of a desert scene from The LEGO Movie:   Thanks for any help!

I'm creating a world made of cubes, similar to cube world game. Is there any quick way to create a map made of cubes that looks like this?


I have Windows XP Profesional here and it gets very annoying when an application that I launched five minutes ago finally brings up its main window and steals focus from the email that I'm writing (or other currently focused window). Is there any way, native to Windows XP, that I can disable this? I know some applications will just blink their title bar on the Taskbar rather than stealing focus, but they don't all behave this nicely.  I am working in a corporate environment, so there may be a limit on what extras/tools can be installed. Also, I am not sure I have access to regedit (and even if I do, Helpdesk will probably not be amused if they find I'm using it).

Are there any solutions to prevent applications stealing focus from the active window?   This is especially annoying when I'm starting an application, switch to do something else and the new application starts receiving half a sentence of text.


Well I know that since $|x|,|y|$ are both positive integers then we have that  $$|x||y| = \gcd(|x|,|y|)\operatorname{lcm}(|x|,|y|)$$  And since we are given that $|x|,|y|$ are coprime then we have $gcd(|x|,|y|)=1$ and so $$|x||y| = \operatorname{lcm}(|x|,|y|)$$  Now all I need to show is that $|x||y| = |xy|$.  Now let $|x| =n,|y| = m$ and also let $|xy|=k$ and consider $(xy)^{mn}$.  $(xy)^{mn} = (x)^{mn}(y)^{mn} = (x^n)^m(y^m)^n = e^me^n = ee= e$. However, since we have $|xy|=k$ then we know that $$k\leq mn.$$ Now I need to show that $mn \leq k$ to conclude that $k=mn$ and so $|x||y| = |xy|$. But I am stuck in here. I know for sure that I need to use the fact that $xy=yx$. But I dunno how

Another homework problem from my Group Theory class.  Let $a,b$ be elements of a group, $G$.  Let $\operatorname{ord}(a)=m$ and $\operatorname{ord}(b)=n$. Let $a$ and $b$ commute. Prove: If $m$ and $n$ are relatively prime, then the $\operatorname{ord}(ab)=mn$.  So I am having trouble starting off on this problem.  Here is what I believe I know:  $a^m=e$ and $b^n=e$ [as defined by the order of the elements] which leads $a^m=b^n$  $\operatorname{ord}(ab)=mn=\operatorname{ord}(ba)=nm$ as defined by commuting.  $\gcd(m,n)=1$ as defined by $m,n$ being relatively prime.    I don't know how to start this proof. Do I want to to go the route of $a^mb^n=e$?  Then $(ab)^{mn}=e$?   Any tips to start this would be greatly appreciated!!!


I have following two line of commands that needs to be run when the computer starts:  killall syndaemon  syndaemon -i 0.5 -KRd   I created one entry in startup application and added following command:  killall syndaemon & syndaemon -i 0.5 -KRd   But it doesn't get executed.  Tried putting the sleep for few seconds also in the command but no luck.

I have a simple one line command which works perfectly in terminal, but does not work in the "Startup Applications" app thing.  The line of code is : xmodmap /home/seph/Code/Ubuntu\ Scripts/Xmodmap  It's not that much of a hassle to copy it from "Startup Applications" and paste it into terminal, but I don't really get why it isn't working.  I followed someone else's instructions to do it in the first place, so maybe I did something wrong?  In any case, wouldn't it be the obvious and logical assumption that it just types whatever you put in it into Terminal?


I need help width the Random r = new Random(); code.  I will give you my code and tell you what I want to do.  Random r = new Random(); int i = r.nextInt(3); System.out.println(i);  //now how do i make it not to take 0 as a random number //One of them is 0, how do i make it take a random int that is //bigger than 0 but lower than 3. I need help there.

How do I generate a random int value in a specific range? I have tried the following, but those do not work: Attempt 1: randomNum = minimum + (int)(Math.random() * maximum);  Bug: randomNum can be bigger than maximum. Attempt 2: Random rn = new Random(); int n = maximum - minimum + 1; int i = rn.nextInt() % n; randomNum =  minimum + i;  Bug: randomNum can be smaller than minimum.


I am so used to work in PHP with multi-dimensional arrays, where I can assign and initialize a hash by  unset($a); // just to show that there is no variable $a $a['settings']['system']['memory'] = '1 Gb'; $a['settings']['system']['disk space'] = '100 Gb';   Is there a way to do similar thing in Ruby? Or I need to initialize all dimensions first, and then to assign values. Is it possible to define an advanced Hash which will allow to do what I need? How would you do that?    Update  In addition to the solution proposed by Douglas (see below), I have found a , in which Brian Schröäer has proposed an extension for the Hash class:  class AutoHash < Hash   def initialize(*args)     super()     @update, @update_index = args[0][:update], args[0][:update_key] unless args.empty?   end    def [](k)     if self.has_key?k       super(k)     else       AutoHash.new(:update => self, :update_key => k)     end   end    def []=(k, v)     @update[@update_index] = self if @update and @update_index     super   end end   It allows to solve the problem when a missing hash item is undesirably created when the item value was only requested, e.g. a['key'].    Some additional references

Creating hashes of hashes in Ruby allows for convenient two (or more) dimensional lookups.  However, when inserting one must always check if the first index already exists in the hash. For example:  h = Hash.new h['x'] = Hash.new if not h.key?('x') h['x']['y'] = value_to_insert   It would be preferable to do the following where the new Hash is created automatically:  h = Hash.new h['x']['y'] = value_to_insert   Similarly, when looking up a value where the first index doesn't already exist, it would be preferable if nil is returned rather than receiving an undefined method for '[]' error.    looked_up_value = h['w']['z']   One could create a Hash wrapper class that has this behavior, but is there an existing a Ruby idiom for accomplishing this task?


"I chose the USA because I love speaking English and am good at it"  It's for a past event, should it be "I loved....and was good..." instead (even though it's still true today)?

Scenario: My friend John has a personality disorder, intensely paranoid for example.  Can I say:     There were three events last year that told me John had a problem.   or can I say:     There were threee events last year that told me John has a problem.


Can I \lstset to define both Matlab code and Python code? or will last one override the first one? or does listings know the difference when there is a .m or .py extension and use the correct \lstset?

I am using the , and have defined lstset parameter sets for multiple programming languages. I would like to select a parameter set when beginning a lstlisting or lstinputlisting by selecting the language corresponding to the parameter set definitions. I appreciate, however, that language selection at this stage only affects formatting of language-specific syntax and is not connected to the preamble parameter set definitions. Rather, enumerating multiple such definitions is fruitless as the last set of definitions overrides all the former ones (or so it appears). Therefore, I would like to know how to define and subsequently invoke multiple lstset parameter sets.  As a very rudimentary example,  \documentclass{article} \usepackage{listings}% http://www.ctan.org/pkg/listings \lstset{language=C,frame=lines} \lstset{language=C++,frame=none} \begin{document} \begin{lstlisting}[language=C] #include<stdio.h> main() {  printf("Hello World"); } \end{lstlisting} \begin{lstlisting}[language=C++] #include <iostream.h> main() {  cout << "Hello World!";  return 0; } \end{lstlisting} \end{document}   As one can see, both languages are displayed using the second defined parameter set (frame=none). I would like to use a key-value pair in the \begin{lstlisting} macro to invoke the appropriate language-specific parameter set defined in the preamble (as suggested by my use of the language= key-value pair). Is this possible?


I fail to even log into recovery terminal, after I roll back to 4.4.0-142-generic kernel (because of error in nvidia driver in 4.4.0-143-generic kernel) after grub update. I login and then somehow additional enter is pressed and voilà, I have brick instead of PC.

I upgraded from 16.04 to 18.04. When I press Ctrl+Alt+F3 I get the terminal which prompts for the username. When I type my username and press Enter, it doesn't wait for my password (its as if I pressed Enter without entering anything). Even if I enter something, the text shown in plaintext and then it keeps on saying my password is wrong. After few times, the screen is cleared and it prompts for my username again and the same loop goes on.


I'm using WSL and I'm quite new on Linux. I have set an environment variable in /etc/environment called TESTVAR. This variable is required for some projects and it's working just fine when I'm running Bash directly.  But if I'm running a Linux command using the Windows cmd like: bash.exe -c "printenv", the variable doesn't exist. So I can't run my commands using cmd otherwise I'll get many errors because the variable contains an important path.  What do I need to do?  Thanks.

I am having trouble getting pip to work behind a corporate firewall. I added the http and https proxies to my /etc/environment file, and if I execute echo "$HTTP_PROXY" it prints the right thing. However, if I execute env or printenv none of the proxy variables show up. I think this is why pip is failing too. Any insight would be appreciated. My /etc/environment file looks like  PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games" http_proxy="http://<stuff>.<stuff>.org:80" HTTP_PROXY="http://<stuff>.<stuff>.org:80" https_proxy="https://<stuff>.<stuff>.org:443" HTTPS_PROXY="https://<stuff>.<stuff>.org:443"   And I added the same lines to my ~/.bashrc file as well.


The site selection component of the app, if you open, and change to a different app without closing the selection then resume the SE app, the selection tool no longer functions and doesn't drop down anymore.  Typing will fix it, but I want to tap the button.    Tested in editing "Your Sites" and writing Meta Stack Exchange question.  Device: Nexus 6 OS: 5.1.1

Steps to reproduce:   Ask a question, open the "Ask on which site?" dropdown menu. Press the back button.   Issue: the menu will disappear and you can't bring it back by tapping the arrow or the field. Only typing text or selecting another field then tapping back will return the dropdown menu.


In English , we use " both of " , " both " for two things   for instance , if you are going out for a meal , there are two possible restaurants, you Say :   both restaurants are very good   Or,   both of the restaurants are very good   what is the difference?

What is the correct form in the following sentences, "both" and "both of them"?      a) "Both of them are unique."      b) "Both are unique."   If "both" by itself already contains "both of them", so I can conclude that the first option is not correct. Isn't it?


Have read a lot of stack overflow answers on this topic and also I have read many blogs. I can surely conclude that Java is pass by value.  But to convince people I need a proof of some language which is pass by ref.  So can someone give a live example of a language which is pass by reference by whose example we could relate that java is not pass by reference.

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


I want to create a batch file which is capable of downloading any files from direct links.  I already tried this:   chrome start http://dl2.romhustler.net/download/MTOeeo3FWffukwoWvagsXw/1430069124/psx_full/Dino%20Crisis%20%5BU%5D%20%5BSLUS-00922%5D.rar   The commands are all in the same line and I tried with quotes and without quotes.  I always get a Forbidden 403 error.  However when I copy and past the link in search bar the file starts downloading without any issue.  Is there any way to make this work?  I am using Windows 7 Ultimate 32-bit.

Without using any non-standard (Windows included) utilities, is it possible to download using the Windows command line?  The preferred version is Windows XP, but it's also interesting to know for newer versions.  To further clarify my question:   It has to be using HTTP The file needs to be saved Standard clean Windows install, no extra tools   So basically, since everybody is screaming , I want simple Wget functionality, without using Wget.


I have recently been shown the gamma function and a few of its uses, and one of those is calculating the measure of the unit ball in $\Bbb{R}^n$. The formula shows the measure going to zero (rather fast, actually) as n grows greater.  I have understood the proof, but it was achieved through some artifacts of integration, and it does not provide a geometric understanding of what is happening.  The result was justified by mentioning that the (hyper)cube that surrounds the sphere has a diagonal of $2^{n/2}$ and that since the measure is, intuitively, how many tiny cubes can I fit inside the sphere, if the volume of the cube is fixed and grows bigger relative to the sphere, then it is the sphere that is becoming smaller overall.  I cannot however visualize this: in fact, the cube has a side length of 2, which translates to a volume of 2^n, which is also growing...  Moreover, an $\infty$-dimensional space has a unit ball of measure $\infty$ (I proved this for $C(0, 1)$), which seems to contrast with the "limit" of the size of $D^n$, the ball of $\Bbb{R}^n$.  Can anyone give an intuitive ("geometric") reason for why the unit balls grow smaller as n increases?

The volume of a $d$ dimensional hypersphere of radius $r$ is given by:  $$V(r,d)=\frac{(\pi r^2)^{d/2}}{\Gamma\left(\frac{d}{2}+1\right)}$$  What intrigues me about this, is that $V\to 0$ as $d\to\infty$ for any fixed $r$.  How can this be?  For fixed $r$, I would have thought adding a dimension would make the volume bigger, but apparently it does not.  Anyone got a good explanation?


I wanted to make an object oriented preprocessor to my programming language which converts my language into C (like early C++). And I want to simulate the classes with structures. And the question is: how can I declare a variable inside a struct like this:   typedef struct { //equivalent of class    int a = 5;    int (*sub)(int) = &int_sub; //function of a class, uses an external declared function } class_name;   I tried the code above but the compiler wrote this:  error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘=’ token         void (*sub)(int) = &int_sub;   I have two questions:   Can I declare a variable inside a struct? If yes, how?

Why can't we initialize members inside a structure ?  example:  struct s {    int i = 10; };


I would like to print to a clean terminal, but not issue a clear or reset command such that the user will not lose data. After the printing is done, I would like to put the user in their old (root) window. I see this done in programs like htop, tmux, less and the like. My understanding is that they create a new window on top of the root, use that, and return the user to the root window when done. How can I emulate the same behaviour in a shell script? I (think I) cannot just pipe what I want to print to less as I need to capture the user's input. Here's a template for what I need: begin-window # a top-layer window is created echo data read input echo processed input read _ # press enter to exit end-window # user is returned to the original window

Today I was using glance tool in my office to monitor CPU utilization.When I run glance from terminal ,the command clears the screen and after all the work when I quit back to the terminal,the previous prompts are still there on my screen.I mean that I can see all the previous lines.My question is how is this effect of clearing screen achieved.If they had used command like clear,It should have cleared the whole screen,how did they manage to get back all the previous prompts ? I want to implement the same feature for some of my scripts.  Similarly when using vi command ,the screen is fully occupied and after exiting,we are able to view previous prompts as well.


I have a timestamp      1457459333506 (Tue, 08 Mar 2016 17:48:53 GMT)   This should be Unix timestamp with milliseconds. I want to write this as a string, so I'm using   $dt = new DateTime("@$unixTimestamp"); echo date('Y-m-d H:i:s.u', $unixTimestamp) . "
";   But the output is 2016-06-08 22:09:22.000000  This is obviously wrong, and has no milisecond precision. So I've tried  echo date('Y-m-d H:i:s.u', $unixTimestamp / 1000) . "
";   Which outputs as 2016-03-08 17:48:53.000000 (correct, but also has no milisecond precision).  How can I get this to output correctly as: 2016-03-08 17:48:53.506 ?

this code always returns 0 in PHP 5.2.5 for microseconds:  <?php $dt = new DateTime(); echo $dt->format("Y-m-d\TH:i:s.u") . "\n"; ?>   Output:  [root@www1 ~]$ php date_test.php 2008-10-03T20:31:26.000000 [root@www1 ~]$ php date_test.php 2008-10-03T20:31:27.000000 [root@www1 ~]$ php date_test.php 2008-10-03T20:31:27.000000 [root@www1 ~]$ php date_test.php 2008-10-03T20:31:28.000000   Any ideas?


I'm studying the motion of photons near a Schwarzschild black hole.   My coordinates to describe the position of a photon are $~r$, $~\theta$, $~\phi$ and $~\textrm{p}_\textrm{r}$, $~\textrm{p}_\textrm{$\theta$}$, $~\textrm{p}_\textrm{$\phi$}$.   I understood that if $~\dot{\textrm{p}_\textrm{$\theta$}} = 0~$ and $~\dot{\theta} = 0~$ is, then the angle $~\theta~$ will stay the same and the photon will stay confined within the plane, right?   However I'm not sure I understood what the (angular-)momenta really represent and what influence on the system they have.   Does anyone have a simple definition and example?   Thanks a lot!

This arises from the question , which I'm afraid I answered just by looking it up in . However Schutz (as he frequently does) glosses over details he thinks are irrelevant or too simple to be worth explaining, and I have realised I don't understand an assumption he makes.  Schutz states without proof that if we have an equatorial orbit in a Schwartzschild metric then:     Independence of the metric of the angle $\phi$ about the axis implies that $p_\phi$ is constant.   In the non-relativistic world I assume this corresponds to angular momentum being constant in a central potential. So far so good. But why is it the component of the dual vector $p_\phi$ that is constant rather than $p^\phi$? The component $p^\phi$ is presumably not constant since (in this case) $p^\phi = p_\phi/r^2$.  Bonus points for also explaining his similar claim that time independance means that $p_t$ is constant rather than $p^t$.  I fear that Schutz didn't explain because it's an insultingly simple question, but if someone can provide a nice intuitive explanation I would be very pleased to read it.


How can i flip a string in c# application like for example : "AMBULANCE" text that is seen as mirror image.I dont have any idea to where to start with .im using c# forms application  I have tried for reversing the string ,but is there any possibility to flip a string (like mirror images)?  Like : ƎƆИA⅃UᙠMA  This is not reversing as in

I've just had to write a string reverse function in C# 2.0 (i.e. LINQ not available) and came up with this:  public string Reverse(string text) {     char[] cArray = text.ToCharArray();     string reverse = String.Empty;     for (int i = cArray.Length - 1; i > -1; i--)     {         reverse += cArray[i];     }     return reverse; }   Personally I'm not crazy about the function and am convinced that there's a better way to do it. Is there?


I just installed Ubuntu 18.04 and the System Monitor app shows transparent and I have to put it on a dark background to actually see the info. ALso the window does not have borders.     What can it be? I installed the communitytheme but it seems like that is not the problem.

I have installed communitheme in gnome-shell. It gives smoother and faster experience. However, I am facing the following issue with System Monitor window. The window is completely transparent.    is there any way to solve this in this theme?


I have been noticing that the consecutive login marker in the user profile is not working right.  This marker can be found in the visits status section on the visited line.  I logged in everyday since I registered and it still states that I am never consecutively logging in. I have checked and rechecked if its something I am not doing right, but I have even counted when I login and it should report a lot more consecutive days then it does.  Can anyone please check on this subject and see if I am doing something wrong? It's pointless to have a marker if it doesn't work right.

I'm pretty depressed that I'm finally one of the people posting this, since I'm usually telling those people "you're obviously wrong", but either I don't understand how consecutive day counting works or this seems impossible:    The last activity count is right; I was on SO at about 18:30Z yesterday (Saturday). Is it possible for the consecutive count to be at 1 if my last activity was yesterday? It would seem like it has to be at least 2 then (although I was definitely active Friday; I suspect Saturday is the "missing" day since all I did was poke through the newest question list and check the current flags)


I am a user of emacs but basically I use the basic commands. I do some competitive coding and for every problem that I solve in C++ I have to write  #include<iostream> #include<stdio.h> using namespace std; int main() {   return 0; }   before I start writing the solution. I was wondering that the mighty text Editor like Emacs must have some feature to pre include a text of string.

Particularly, what is the best snippets package out there?  Features:   easy to define new snippets (plain text, custom input with defaults) simple navigation between predefined positions in the snippet multiple insertion of the same custom input accepts currently selected text as a custom input cross-platform (Windows, Linux) dynamically evaluated expressions (embedded code) written in a concise programming language (Perl, Python, Ruby are preferred) nicely coexists with others packages in Emacs   Example of code template, a simple for loop in C:  for (int i = 0; i < %N%; ++i) {   _ }   It is a lot of typing for such common code. I want to invoke a code template or snippet which inserts that boilerplate code for me. Additionally it stops (on TAB or other keystroke) at %N% (my input replaces it) and final position of the cursor is _.


I frequently come across a really useful answer on StackOverflow which has been closed because it doesn't match the Q&A format.  Examples include  ,  ,   ,  and there are others.  Where should this information be exchanged if it's not on stackoverflow?  It seems the moderators are often somewhat overzealous...  ---edit  When I say best, I mean they are informative and useful for someone who's looking for an answer to them.  Even if they do become a bit of a discussion, I value other people's opinions on the relative merits of the different JPA frameworks.  I come here looking to choose one and the answer helps me.  So what if it's not a definitive answer?  ---edit  I don't care how popular a question is, nor how interesting it is.  Users are interested in stuff that's useful to them.  Plenty of those were useful (as judged by the upvotes on the answers: 'This answer is useful'), but closed because they didn't have a definitive answer, as far as I can tell.  ---edit  Seems I'm not the first person to think this: there are various similar questions to mine like this one:   In it the user lists lots of other useful questions which have been closed:                    So isn't there a place on stackoverflow for these questions?  A discussion section, maybe?

I'm on SO pretty much every day researching something to do with programming, and over the last month or two, I find I'm growing frustrated and a little disgusted at how many interesting questions have been closed as "not a good fit" or "too subjective".  I think there is a confusion between "subjective" and "calls for judgement". To me one of the most valuable things about SO is the tremendous breadth and depth of experience of the members, and experience translates into smart decisions and advice, and that advice cannot always be asked for, or expressed in terms of, bald facts and data.  It's going to be 'subjective'.  I don't think SO should be Wikipedia. I think that if I could ask a question to a group of skilled programmers sitting around a table at lunch, and get interesting, valuable answers, then I don't care whether the question or the answers are 'subjective', I think that question should equally well be fair game for Stack Overflow.  I would like to see a mechanism whereby people who vote to close a question lose reputation when somebody expresses interest in that question or its responses.  How can I, or can I, influence this aspect of SO?


When I add a table:    \begin{table} \begin{center} \begin{tabular}{ | m{2cm} | m{6cm}| m{7cm} | }  \rowcolor{Gray}  \hline Aspect & Angular  & React \\  \hline Développeur & Google & Facebook \\  \hline Langage & Typescript & Javascript ou JSX \\  \hline Architecture & Utilise une hiérarchie de composants & Utilise des composants basés sur JSX \\  \hline Databinding & Utilise Liaison d'événement et des propriétés & Gestion de l’état des composants avec l’architecture flux \\  \hline Routage & Utilise Liaison d'événement et des propriétés & Gestion de l’état des composants avec l’architecture flux \\  \hline \end{tabular} \end{center} \caption{Comparaison entre Angular et React} \label{angular_react} \end{table}   It gets added in the beginning of the page despite the fact that in the source code I added it after the Angular paragraph:  However, when I remove:  \begin{table} \end{table}   This kindof solves the issue. It displays the table in its place but it removes the caption:  This is really strange. I need the table in its place, with the caption. Howver, I couldn't solve this. Any help?

How to influence the position of float environments like figure and table in LaTeX?   This is a general question and should collect useful answers for all users. I hope we can use this as a reference


I want to make a modification to text inside my span after css will finish my animation (200ms). I want to pass a delay parameter to my hover state, so it would wait. My code is as follows:  $('.overlay').each(function() {     var text = $(this).children('.category').children('span').text(),         newtext = text.substring(0,1);      $(this).children('.category').children('span').text(newtext);      $(this).delay(5000).hover(function() {         $(this).children('.category').children('span').delay(5000).stop().text(text);     }, function() {         $(this).children('.category').children('span').text(newtext);     }) });   Unfortunately, it doesn't work, no matter where I place delay. What can I do?

I would like to delay a hover event in jquery.  I am reading from a file when user hovers over a link or label.  I don't want this event to occur immediately in case the user is just moving the mouse across the screen.  Is there a way to delay the event from firing?  Thank you.  Example code:  $(function() {     $('#container a').hover(function() {         $('
').load('ReadTextFileX.aspx',             {filename:'file.txt'},             function() {                 $(this).appendTo('#info');             }          );     },         function() { $('#info').remove(); }     }); });   UPDATE: (1/14/09) After adding the HoverIntent plugin the above code was changed to the following to implement it.  Very simple to implement.  $(function() {     hiConfig = {         sensitivity: 3, // number = sensitivity threshold (must be 1 or higher)         interval: 200, // number = milliseconds for onMouseOver polling interval         timeout: 200, // number = milliseconds delay before onMouseOut         over: function() {             $('
').load('ReadTextFileX.aspx', {filename:'file.txt'},                 function() {                    $(this).appendTo('#info');                 }              );         }, // function = onMouseOver callback (REQUIRED)         out: function() { $('#info').remove();  } // function = onMouseOut callback (REQUIRED)     }     $('#container a').hoverIntent(hiConfig) }


01-02 05:30:50.220 8776-8776/com.wordpress.alhazn.puhaba E/AndroidRuntime: FATAL EXCEPTION: main java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.wordpress.alhazn.puhaba/com.wordpress.alhazn.puhaba.MainActivity}: java.lang.NullPointerException     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2045)     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2146)     at android.app.ActivityThread.access$700(ActivityThread.java:140)     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1238)     at android.os.Handler.dispatchMessage(Handler.java:99)     at android.os.Looper.loop(Looper.java:177)     at android.app.ActivityThread.main(ActivityThread.java:4944)     at java.lang.reflect.Method.invokeNative(Native Method)     at java.lang.reflect.Method.invoke(Method.java:511)     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)     at dalvik.system.NativeStart.main(Native Method)  Caused by: java.lang.NullPointerException     at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:117)     at android.support.v7.app.AppCompatDelegateImplV9.<init>(AppCompatDelegateImplV9.java:149)     at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:29)     at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:54)     at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:202)     at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:183)     at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:519)     at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:190)     at com.wordpress.alhazn.puhaba.MainActivity.<init>(MainActivity.java:44)     at java.lang.Class.newInstanceImpl(Native Method)     at java.lang.Class.newInstance(Class.java:1319)     at android.app.Instrumentation.newActivity(Instrumentation.java:1068)     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2036)     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2146)      at android.app.ActivityThread.access$700(ActivityThread.java:140)      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1238)      at android.os.Handler.dispatchMessage(Handler.java:99)      at android.os.Looper.loop(Looper.java:177)      at android.app.ActivityThread.main(ActivityThread.java:4944)      at java.lang.reflect.Method.invokeNative(Native Method)      at java.lang.reflect.Method.invoke(Method.java:511)      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)      at dalvik.system.NativeStart.main(Native Method)

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


Folks, This Question is not about Sql Injection. I know how to prevent Sql injections. And so, it's not similar to:  I use Prepared Statements. This question is about html tags injections to breakup the html of my webpage. The following php code is a pagination section like the bottom part of google SERP. The code builds the page numbers at the bottom of the SERP. Like: (Page 12345678910). My concern is how I made use of the security functions to prevent user attacks (user inputs containing html tags etc. to break the html of my page and any other malicious inputs) when making keyword searches to my Mysql Database. I am making use of urlencode(), rawurlencode() and htmlentities() to achieve my purpose. Experimenting to learn how to use these functions properly. Now bearing these 3 functions in mind, especially the rawurlencode(), can you fine folks tell me which WHILE loop from my 2 codes below I should stick to with an explanation why you favour that one over the other ? Your feed back would be a good learning for me. Thank You. <?php //ERROR REPORTING FOR DEVMODE ONLY. ini_set('display_errors','1'); ini_set('display_startup_errors','1'); error_reporting(E_ALL); ?>  <?php //PAGINATION SECTION. $search = $_GET['search']; //Keyword(s) to search. $col = $_GET['col']; //MySql Tbl Col to search. $tbl = $_GET['tbl']; //MySql Tbl to search. $max = $_GET['max']; //Max Result per page. $page = $_GET['page']; //Serp Number.  $row_count = 100; //WHICH ONE CORRECT ? Matching rows found in this example. $row_count = '100'; //WHICH ONE CORRECT ? Matching rows found in this example. $total_pages = ceil($row_count/$max); $i = '1';   //$selfpage = $_SERVER['PHP_SELF']; $selfpage = basename(__FILE__,''); //Echoes: url_encode_Template.php. Does not fetch the url $_GET params. $path = rawurlencode($selfpage); $query_string_1 = '?search=' .urlencode($search) .'&tbl=' .urlencode($tbl) .'&col=' .urlencode($col) .'&max=' .intval($max);  //WHICH WHILE LOOP IS BEST ? while($i<=$total_pages) {     $query_string_2 = '&page=' .intval($i);     $url = $path .htmlentities($query_string_1) .htmlentities($query_string_2); //Full URL With $_GET params: https://localhost/Templates/url_encode_Template.php?search=keyword&tbl=links&col=keyword&max=100&page=1      if($page == $i)     {         echo '' .'' .intval($i) .'' .'';     }     else     {         echo '' .intval($i) .'';     }     $i++; }  echo '
'; echo __LINE__; echo '
';   $i = '1'; //WHICH WHILE LOOP IS BEST ? while($i<=$total_pages) {     $query_string_2 = '&page=' .intval($i);          if($page == $i)     {         echo '' .'' .intval($i) .'' .'';     }     else     {         echo '' .intval($i) .'';     }     $i++; }  ?>         NOTE: The differences between the two WHILE loops is this. The first one has $url variable while the second doesn't. Second one directly echoes htmlentities() while first one adds htmentities() to the var $url and echoes the $url instead. Notice what is getting echoed on both WHILE loops as the echoes differ between the two WHILE loops. I reckon the first one is better. But I prefer your professional opinion. In short, which of these two WHILE I should rid.

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


public class TimsOrder {      private int size;     private String name;     private static TimsProduct[] items;      private TimsOrder(String name, int size) {         this.name = name;         this.size = size;     }      @Override     public double getRetailPrice(){         return price;     }      private static void orderItem(TimsProduct item) {         Donut chocolate = Donut.create();         item = chocolate;     }      public static TimsOrder create() {         items = new TimsProduct[size];         for (int i = 0; i < items.length; i++) {             orderItem(items[i]);         }         TimsOrder order = new TimsOrder("OrderName", 1); //Where 1 is the # of items     }      public double getAmountDue() {         double total = 0;         System.out.println("Testpoint");         for (int i = 0; i < items.length; i++) {             total = total + (((TimsProduct) items[i]).getRetailPrice()); //Line with issue         }         return total;     } }  public abstract class TimsProduct extends Commodity {     private String name;     private double cost;     private double price;      @Override     public double getRetailPrice(){         System.out.println("Testpoint2");         return price;     } }  public class Donut extends TimsProduct {     private String description;     private int calorieCount;      private Donut(String name, String description, double cost, double price, int calorieCount) {         super(name, cost, price);         this.description = description;         this.calorieCount = calorieCount;     }      public static Donut create() {         Donut chocolate = new Donut("Chocolate", "Glazed", 0.30, 0.99, 500);         return chocolate;     } }   Test Code:  TimsOrder t = TimsOrder.create(); System.out.println(t); System.out.printf("Total Price: $%.2f\n", t.getAmountDue());   I realize that t.items has 0 values which is the problem here. What I do not know is why these values are not there.  If anyone wants to see the files: Commodity.java   TimsProduct.java extends commodity   TimsOrder.java   Donut.java extends TimsProduct

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


I'm quite stuck on this function for a c++ program.   Instructions Write a function called RemoveGrades that takes the student array and grade vector as parameters, it asks the user for a valid assignment number, loops through each student, and removes the selected assignment from each student's grades vector.  I've searched a lot about deleting specific elements from vectors but can't seem to figure out how to get vector.erase() to work. I think the issue is that I'm working with a vector of arrays of ints.  code  given  // may be declared outside the main function  const int NUM_STUDENTS =3;   // may only be declared within the main function  string Students[NUM_STUDENTS] = {"Eric","Stacy","Mark"};  vector <int> grades[NUM_STUDENTS] {     {10,98,88,99,57},     {62,80,94,100,93},     {11,82,28,85,38} };  void RemoveGrades(string Students[],vector<int> grades[],int numstudents){     cout<<"Remove assignment"<<endl;     int assignmentNum;     assignmentNum=getValidAssignmentNumber();     for (int index=0;index<numstudents;index++) {            grades[index].erase(assignmentNum);      } }   If I put in two arguments in grades[index].erase clion tells me I need one argument, and if I put one it tells me I need two. Any help is appreciated. Thanks  Error messages  No matching member function for call to 'erase' candidate function not viable: requires single argument '__position', but 2 arguments were provided  In function 'void RemoveGrades(std::string*, std::vector*, int)': /cygdrive/c/Users/Ryan Foster/CLionProjects/arrays_and_vectors_second_try/main.cpp:191:56: error: no matching function for call to 'std::vector::erase(int&, int&)'          grades[index].erase(assignmentNum,assignmentNum);

I want to clear a element from a vector using the erase method. But the problem here is that the element is not guaranteed to occur only once in the vector. It may be present multiple times and I need to clear all of them. My code is something like this:  void erase(std::vector<int>& myNumbers_in, int number_in) {     std::vector<int>::iterator iter = myNumbers_in.begin();     std::vector<int>::iterator endIter = myNumbers_in.end();     for(; iter != endIter; ++iter)     {         if(*iter == number_in)         {             myNumbers_in.erase(iter);         }     } }  int main(int argc, char* argv[]) {     std::vector<int> myNmbers;     for(int i = 0; i < 2; ++i)     {         myNmbers.push_back(i);         myNmbers.push_back(i);     }      erase(myNmbers, 1);      return 0; }   This code obviously crashes because I am changing the end of the vector while iterating through it. What is the best way to achieve this? I.e. is there any way to do this without iterating through the vector multiple times or creating one more copy of the vector?


Most of the villains to most of the kages were reincarnated but Why wasn't Jiraya reincarnated.  Kabuto reincarnated almost everyone from the past during the war and the presence of Jiraya could've been too helpful for him.But my question is what was the reason for reincarnating him.

During the Great War, Kabuto resurrects a lot of very, very powerful shinobi (Madara or Hashirama the 1st, e.g.). However, he doesn't bring someone as powerful and impactful as Jiraiya.  My girlfriend pointed this out a few days ago and since now, I wasn't able to find a reason. I see that this Edo Tensei no Jutsu brings up some questions ( or even ) on the table, but it seems that everyone forgot Jiraiya in this equation.  Why didn't Kabuto resurrect Jiraiya during the Great War?


I have a raster which I want to cut. A second raster smaller, should be exactly the part where I want to cut the first layer (so I cut the same size as raster 2).  The idea is that raster 2 become the mask for the cut. How can I do this?

Given two input layers  The clip layer - an arbitrary layer (though in my case it's a float 1 band geotiff) The mask layer - a paletted raster in which every pixel is either NO DATA or a single "color" value, same for every pixel.  I want to create an output raster whose overall extent matches the extent of the mask layer and each pixel is either NO DATA if the corresponding pixel of the mask layer is NO DATA or the value of the corresponding pixel from the clip layer if the corresponding pixel of the mask layer is not NO DATA. I know I can mask the clip layer with a polygon, but the mask layer is a raster. Polygonizing the raster layer is possible in principle, but would result in a polygon with a lot of very short edges. Is there a direct way to do this in QGIS? I suppose there's probably a path that involves creating a new layer and using the raster calculator, but I'm hoping there's something more direct. Further complicating the matter is that the two rasters might not have the same resolution and origin. I believe this is equivalent to  in ArcMap.


Anyone know a good explanation of the QQ-plot algorithm?  , p.2. has the only one I've found and it's a bit unclear to me (particularly the percentiles and quantiles).

In , Nick Cox wrote:     Binning into classes is an ancient method. While histograms can be useful, modern statistical software makes it easy as well as advisable to fit distributions to the raw data. Binning just throws away detail that is crucial in determining which distributions are plausible.   The context of this comment suggests using QQ-plots as an alternative means to evaluate the fit. The statement sounds very plausible, but I'd like to know about a reliable reference supporting this statement. Is there some paper which does a more thorough investigation of this fact, beyond a simple “well, this sounds obvious”? Any actual systematic comparisons of results or the likes?  I'd also like to see how far this benefit of QQ-plots over histograms can be stretched, to applications other than model fitting. Answers on  agree that “a QQ-plot […] just tells you that "something is wrong"”. I am thinking about using them as a tool to identify structure in observed data as compared to a null model and wonder whether there exist any established procedures to use QQ-plots (or their underlying data) to not only detect but also describe non-random structure in the observed data. References which include this direction would therefore be particularly useful.


Please help me. I noticed that my laptop was on a spilled water on the table over night. I dismantled it and cleaned it up, dried it as much as I could from a warm temperature viz rays on the sun for a day.  Now it can only power and make a noise with the fan then goes off... don’t know what to do from here. Also when plugged in for a charge it doesn’t show light of power.

I'd love some advice in repairing a water-damaged laptop.  My girlfriend spilled a glass of water on her Sony Vaio and now it doesn't turn on...at all...dead! What steps should I go through to work out where the problem is and which part(s) I'll need to replace?  I can't seem to find out what has happened by just looking at the circuit boards. I'm new to electronics but could buy relevant volt-meters etc. I'm just looking for a decent trouble-shooting guide.


I'm getting an "unresolved external symbol "public:__thiscall hijo<int>::hijo<int>(void)" referenced in function_main   I started a new project cause I was having this same error on another larger project. The error occur when I try to allocate space using the new keyword. If this error is silly please forgive me cause I haven't programmed anything in the last months.    /********************file hijo.h******************/ #pragma once #ifndef hijo_h #define hijo_h  template <class A> class hijo { public:     hijo(void);     ~hijo(void); }; #endif     /********************file hijo.cpp***************/     #include "hijo.h" #include <iostream> using namespace std;  template <class A> hijo<A>::hijo(void) { } template <class A> hijo<A>::~hijo(void) { }   /*********************at main() function ***************/  #include <iostream> #include "hijo.h"  int main(){      hijo<int> *h = new hijo<int>; <----  PROBLEM AT THIS LINE      system("pause");     return 0; }

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


I use Gnome Tweaks Tool 3.34.0 (and GNOME Shell 3.36.4) and under "Keyboard & Mouse" I change via "Additional Layout Options" the "Caps Lock Behavior" to be swapped with Escape key.  Yet while this works for a while, the setting often undoes itself and I don't know why. The setting is seen as toggled, but the default behavior of the button is restored. How can I make the swap permanently? The issue occurs often when I lock the screen and login. Also, I have an USB switch to use my input devices at another PC. So it may have to do with the unlpugging the keyboard and then restoring the connection.  $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 20.04.1 LTS Release:    20.04 Codename:   focal

I have caps-lock key remapped to control, which usually works fine, but after some uptime and one/more suspend/awake cycles* this mapping breaks, and caps-lock reverts back to the default behavior -- i.e. turning on the led and capitalizing whatever I type. (Even though the Tweaks UI still shows it as being mapped to Ctrl -- see picture below.)  Questions:  Is this a known issue (with maybe a known fix)? (Could not find anything relevant with a quick search.) Is there a way to debug the problem, preferably from the command line?  *Remark: I'm not sure it is the suspend/awake cycle that causes the problem, but I can't connect it to anything else... Remark2: removing and readding the mapping (or rebooting) solves the problem, but it would be nice to find a more permanent solution.


Let $f$ be a function on $R^2$ that is a polynomial in $y$ when $x$ is fixed and that is a polynomial in $x$ when $y$ is fixed. Is it true that $f$ is a polynomial?  The only idea I come up with is the characterization of one-variable polynomials. A function $p(x)$ is a polynomnial iff $p^{(n)}(x)=0$ for some $n$. This gives that the $m$th partials of $f$ are zero for $m \in \mathbb Z_+$. But how to conclude that $f$ is a polynomial in two variables? Is there any criterion that I can use?

I have problems proving the following result:     Each $f: \mathbb{R}^2 \rightarrow \mathbb{R}$ such that $\forall a,b \in \mathbb{R} \ : \ f_a(y) := f(a,y), \ f_b(x) := f(x,b) $ are polynomials is a polynomial with two variables.   If I consider $f$ as a function of $x$, then its derivative  $f'(x) = \frac{\partial f}{\partial b}(x)$. Similarly if we treat $f$ as a function of $y$.   I assume that $f_a(y) = \frac{\partial f}{\partial a} (y) $ and $f_b(x)=\frac{\partial f}{\partial b}(x)$.  But I am not sure if we can assume that, because  the degree of the derivative should be smaller than the degree of the original function (and it isn't).   Actually, I'm not even sure if what I'm trying to prove is true, because in the original formulation of the problems there is written $f_a(y) := (a,y), \ f_b(x):=(x,b)$. But that didn't make sense.  Could you help me here?  Thank you.


The command \label{here} defines a label and \ref{here} outputs the corresponding representation in the text. Is it possible to get the correspondig (numeric) counter value for the here reference so that one could do calculations with it and use it to set a counter, for example?

I want to compare the output of \ref to a number in LaTeX. I thought it would be easy but after spending lots of hours surfing the net I still don't know the answer. I found similar questions on this site but I would prefer a solution that does not require another package to be included, so that I can see clearly how the \ref command (and some others) works. I tried a lot of things, some of which I share below, therefore my question is rather long, I'm sorry about that. First, I tried the following codes (the resulting error messages are shown after a % sign):  \begin{equation} \label{eq:myeq}   a=b   \end{equation}  \ifnum\ref{eq:myeq}=1 true\else false\fi % error: "Missing number, treated as zero."  \expandafter\ifnum\ref{eq:myeq}=1 true\else false\fi % error: "Missing number, treated as zero."  \edef\blabla{\ref{eq:myeq}} % error: Incomplete \iffalse; all text was ignored after line 42. \ifnum\blabla=1 true\else false\fi \expandafter\ifnum\blabla=1 true\else false\fi   Of course, \ref{eq:myeq} gave the expected result, namely 1.  Then, I found the definition of \ref using the latexdef ref command:       \ref:   macro:#1->\expandafter \@setref \csname r@#1\endcsname \@firstoftwo {#1}   Further examining \@setref and \firstoftwo, I concluded that the equation number (together with the page number) is stored in a control sequence called \r@eq:myeq. More precisely, the content of \r@eq:myeq is {1}{1} where the first number is the equation number and the second number is the page number. (The output of \expandafter{\csname r@eq:myeq\endcsname} is 11.) If I understand well, in order to obtain the equation number we have to expand \csname r@eq:myeq\endcsname by only two levels to get {1}{1} (the first level of expansion yields \r@eq:myeq), and then we choose the first argument by \@firstoftwo. Since there is no simple way to expand a control sequence by only one level, it is done in a rather circuitous (say tricky) way by \ref. This I could also reproduce by the following code:  \def\sth#1#2{\expandafter #2#1} \makeatletter \expandafter\sth\csname r@eq:myeq\endcsname\@firstoftwo \quad \ifnum1=\expandafter\sth\csname r@eq:myeq\endcsname\@firstoftwo true\else false\fi \makeatother   which resulted in 1   true. So far so good but there are still a few questions. First of all, if the above code works then why does the code with \ifnum1=\ref{eq:myeq}... fail (see above)? Seemingly, the two "algorithms" are doing the same. Second, the above code works only if the auxiliary file (with aux extension) contains the label definition. If it doesn't (the reference is undefined) then LaTeX gives the following error message: Missing number, treated as zero. How can I write a code that works even if the reference is undefined? Thank everybody who read all my above struggle and I would appreciate if someone shed light on the points that were not clear to me and who corrected me where I was wrong and confirmed where I was correct. Unfortunately the whole command syntax of (La)TeX is still very strange to me.


I am new here. I was wanting to know if you can use tags whenever I am answering another person's questions? Tags have me a bit confused?   Chat Support mobile-web 'bug-feature request discussion support'.

My question—my meta-question as the case may be—concerns the purpose of these words referred to as "tags". Let me be clear: I use tags. The site supports them, so why shouldn't I? My understanding of their reason for existing is tragically incomplete.   Are they used for searching? Are they useful in any other way, or do they merely act as decoration?     For more information, see "" and "" in the .


I have Ubuntu 14.04 server running. It is running on VirtualBox 5.1.12r112440. The vdi size was 50GB but I used this link to resize it successfully to 200GB:    However when I boot the VM up it says root / is next to zero disk space.     The image shows that I have about 50GB of unallocated space in the /dev/sda5 extended partition to use for resizing the partition for root. In the GParted Live CD app thats displayed I dont see the devices /dev/sda2 - /dev/sda4. I suspect that root is one of this non listed partitions. So how do I get root more disk space?  df -h Filesystem          Size  Used Avail Use% Mounted on udev                2.0G  4.0K  2.0G   1% /dev tmpfs               396M  684K  395M   1% /run /dev/dm-0            45G   43G  366M 100% / none                4.0K     0  4.0K   0% /sys/fs/cgroup none                5.0M     0  5.0M   0% /run/lock none                2.0G   12K  2.0G   1% /run/shm none                100M     0  100M   0% /run/user /dev/sda1           2.4G   47M  2.2G   3% /boot  pvdisplay   --- Physical volume ---   PV Name               /dev/sda5   VG Name               matrix-ubuntu-vg   PV Size               106.70 GiB / not usable 2.00 MiB   Allocatable           yes    PE Size               4.00 MiB   Total PE              27314   Free PE               14584   Allocated PE          12730   PV UUID               lVlrhr-IDvI-i81L-GmZp-Dj12-tx24-NjuSOZ   Thanks for helping!  Please refer to my answer as to why this is not answered by the "possible duplicate". The write up in the link I provided is a pretty good walk through on how to resize a LVM partition.

I want to shrink my second (LVM) partition, in order to create a new partition in the newly freed space. I am using the Live CD to do so, because I know I can't resize/move this partition while it is in use. When I opened GParted in the Live CD, I realized that I could not resize the partition, because when I right-click it, the option "resize/move" is disabled.  I tried to unmount it, to "lazy" unmount it (umount -l /dev/sda2) but it didn't work.  A screenshot from GParted:


I was solving some questions on Math Stack Exchange about irrational numbers when suddenly this question struck me.  We know that $e$ is irrational and that $\pi$ is also irrational.  Then is $\pi\cdot e$ rational or irrational?

A little reading suggests:  It is known that either $\pi + e$ or $\pi \times e$ is transcendental (or possibly both), but no proof is known that one of those two numbers in particular is transcendental.  If we just want irrationality rather than transcendence, is a proof known?  Can we prove $\pi+e$ is irrational?  Can we prove $\pi \times e$ is irrational?


I want to upgrade my 12.04LTS to 14.04LTS. I have tried update-manager-d , and in update manager settings I have set something like : "Notify when new LTS version...". But I don`t get message that new Ubuntu is available . Update manager shows that no, updates available.

So I have Ubuntu installed on my pc, and I want to upgrade to the new Ubuntu which was just released. When I check for any new updates it doesn't show any upgrades to the new release. How can I fix this? Thanks!


I heard some guy say that we can't digest plant food as well as herbivores. Which seems weird to me seeing as how humans can survive without any nutrient deficiencies besides b12 on only plants but we would pretty much just die of nutrient deficiencies on a carnivore diet. Can someone show me how we can't digest plant food as well as herbivores?

Can a human eat grass and digest it? Could it be possible to use it as food just like other plants such as wheat or beans?


The assignment says "using conditionals and a while loop, prompt the user to either ask another question of thank them for using the program, depending on what they decide."  Trying to figure out how to use a while loop to continuously prompt the user to decide if they would like to continue. Wouldn't I need a new scanner each time?  Also, my program stops right after the user enters yes or no in the second scanner. Ahhhhhh.  Here's what I'm working with:     System.out.println("Hello!\nNeed to make a decision?\nWant to know about the future?\nType in a yes or no question and press Enter: ");     Scanner reader = new Scanner(System.in);    String question = reader.nextLine();     System.out.println();     Random generator = new Random();    int rand = generator.nextInt(20) + 1;     if (rand == 1)    { System.out.println("It is certain.");}     if (rand ==2)     {System.out.println("It is decidedly so."); }     if (rand ==3)    {System.out.println("Without a doubt."); }     if (rand ==4)     { System.out.println("Yes, definitely.");}     if (rand ==5)    {System.out.println("You may rely on it.");}     if (rand == 6)    {System.out.println("As I see it, yes."); }     if (rand == 7)    {System.out.println("Most likely.");}     if (rand == 8)    {System.out.println("The outlook is good");}     if (rand == 9)    {System.out.println("Yes.");}     if (rand == 10)    {System.out.println("Signs point to yes.");}     if (rand == 11)    {System.out.println("Reply hazy.");}     if (rand == 12)    {System.out.println("Ask again later.");}     if (rand == 13)    {System.out.println("Better not tell you now.");}     if (rand ==14)    {System.out.println("Cannot predict now.");}     if (rand ==15)    {System.out.println("Concentrate and ask again.");}     if (rand == 16)    {System.out.println("Don't count on it.");}     if (rand == 17)    {System.out.println("My reply is no.");}     if (rand ==18)    {System.out.println("My sources say no.");}     if (rand == 19)    {System.out.println("Outlook does not look so good.");}     if (rand == 20)    {System.out.println("Very doubtful.");}      System.out.print("\nWould you like to ask another question?: ");    Scanner reader2 = new Scanner(System.in);    String YesNo = reader2.nextLine();       if (YesNo == "no") {        System.out.println("Thanks for playing!"); }       while (YesNo == "yes") {       System.out.println("Enter your question: ");     Scanner reader3 = new Scanner(System.in);    String question2 = reader3.nextLine();     Random generator2 = new Random();    int rand2 = generator.nextInt(20) + 1;     System.out.println();     if (rand2 == 1)    { System.out.println("It is certain.");}     if (rand2 ==2)     {System.out.println("It is decidedly so."); }     if (rand2 ==3)    {System.out.println("Without a doubt."); }     if (rand2 ==4)     { System.out.println("Yes, definitely.");}     if (rand2 ==5)    {System.out.println("You may rely on it.");}     if (rand2 == 6)    {System.out.println("As I see it, yes."); }     if (rand2 == 7)    {System.out.println("Most likely.");}     if (rand2 == 8)    {System.out.println("The outlook is good");}     if (rand2 == 9)    {System.out.println("Yes.");}     if (rand2 == 10)    {System.out.println("Signs point to yes.");}     if (rand2 == 11)    {System.out.println("Reply hazy.");}     if (rand2 == 12)    {System.out.println("Ask again later.");}     if (rand2 == 13)    {System.out.println("Better not tell you now.");}     if (rand2 ==14)    {System.out.println("Cannot predict now.");}     if (rand2 ==15)    {System.out.println("Concentrate and ask again.");}     if (rand2 == 16)    {System.out.println("Don't count on it.");}     if (rand2 == 17)    {System.out.println("My reply is no.");}     if (rand2 ==18)    {System.out.println("My sources say no.");}     if (rand2 == 19)    {System.out.println("Outlook does not look so good.");}     if (rand2 == 20)    {System.out.println("Very doubtful.");}      System.out.print("\nWould you like to ask another question?: ");  } }   }

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


Evaluate : $$ \lim_{n\to\infty}\left(\dfrac{1}{e^{n}}\displaystyle \sum_{r=0}^{n} \dfrac{n^r}{r!}\right) $$  Numerical calculation suggests that the limit should be $\dfrac{1}{2}$. I tried using  and , but to no avail. An elementary solution is appreciated. Thanks in advance.

I'm supposed to calculate: $$\lim_{n\to\infty} e^{-n} \sum_{k=0}^{n} \frac{n^k}{k!}$$ By using WolframAlpha, I might guess that the limit is $\frac{1}{2}$, which is a pretty interesting and nice result. I wonder in which ways we may approach it.