Early on we are told that π = C/D where C is the circumference and D the diameter of a circle.  We are told π is a constant; that it does not get larger or smaller if the size of the circle changes.  But no one ever proves it. It gets skipped in elementary geometry, and then we never get back to it. Can you invent a proof that a) does not involve limits and is simple enough to explain to high school geometry students; b) does involve limits c) uses calculus d) is different from all of the above.

Is there a proof that the ratio of a circle's diameter and the circumference is the same for all circles, that doesn't involve some kind of limiting process, e.g. a direct geometrical proof?


I'm using Centos 7. When I sshpass to my remote login server, I need to specify the title to every terminal I open through gnome-terminal. I tried following approach from the link suggested by @Jesse_b in the first comment.  gnome-terminal --maximize  --tab -e 'bash -c "echo -ne \"\033]0;title1\007\"; top"' \ "sshpass -p "Password" ssh -o StrictHostKeyChecking=no mayank@IP_add 'cd /abcd/efg/ ; bash;'"  gnome-terminal --maximize  --tab -e 'bash -c "echo -ne \"\033]0;title2\007\"; bash -i"' \ "sshpass -p "Password" ssh -o StrictHostKeyChecking=no mayank@IP_add 'cd /abcd/efg/ ; bash;'"   I've created following function in ~/.bashrc as it mentioned in that link.  function set-title() {   if [[ -z "$ORIG" ]]; then   ORIG=$PS1 fi   TITLE="\[\e]2;$*\a\]"   PS1=${ORIG}${TITLE} }   In my first terminal title is getting changed but it seems I can't use it for further use. And my second terminal launched but did not login to my server neither changed the title. Image of first terminal is     But when I ran following command as I want to achieve more than two terminal.  gnome-terminal --maximize  ---tab -t "Title1" -e "sshpass -p "Password" ssh -o StrictHostKeyChecking=no mayank@Ip_add 'cd /abcd/efg/ ; bash;'"    All the terminals are being opened, their titles are changing and loging in on my server but, again I cannot use them further.  Please suggest any solution, what am I doing wrong.

I've seen  about launching gnome-terminal with multiple tabs and the script below is working for me.  That is to say, this script will launch gnome-terminal with various working directories or profiles. . .  #!/bin/sh gnome-terminal \ --tab --working-directory=$HOME/notes  \ --tab --working-directory=$HOME/puppet \ --tab --profile=root-beamish           \ --tab --profile=odyssey                \ --tab --profile=root   ... but I'd like to set a unique title for each tab.  In the case where a tab has its own profile I can change the title from within gnome-terminal with Edit | Profiles | (NAME) | Edit | Title and Command and then change "Initial Title" to what I want and "When terminal commands set their own titles" from "Replace initial title" to "Keep initial title".  However, I'd rather not create a unique profile for every tab.  I'd like a generic solution.  I've tried adding --title='MyTitle' but it doesn't seem to help.  I'm using GNOME 2.28.2 on CentOS 6.


Which is correct, me and Robyn are going to the bar, or Robyn and I are going to the bar?

From some comments in the answers for  (now deleted, 10k only), there's confusion around the usage of I vs. me:  While the sentence, "the other attendees are myself and Steve," is agreed to be incorrect, there's confusion about whether the correct form is "the other attendees are me and Steve" or "the other attendees are Steve and I."  (I've always used the heuristic of removing the other people from the sentence, so I always thought "the other attendee is me" would be correct, instead of "the other attendee is I." Is this true, or am I using a flawed heuristic?)


While adding a polygon feature in QGIS 2.2.0-Valmiera, the representation symbology of that particular feature(which is in-progress) appears to be "filled" until the completion(rightclick)  of digitization, eventhough that layer symbology is given as 'Outline: Simple line' as shown in attached screenshot. How to fix this?

How can I change the settings on the vector "add feature" tool so the tool fill doesn't block my view of what I want to digitize?  This problem popped up after I upgraded to QGIS 2.0   QGIS 2.0 Macbook Pro  OS 10.9


I'm trying to install GDAL and GDAL development libraries on Ubuntu 20.04 with the following commands (source: ): sudo add-apt-repository ppa:ubuntugis/ppa sudo apt-get update sudo apt-get install gdal-bin ogrinfo --version   GDAL installs successfully and it returns: GDAL 3.0.4, released 2020/01/28  After that, I tried installing GDAL development libraries: sudo apt-get install libgdal-dev  It returns the following error: Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  libgdal-dev : Depends: libpq-dev but it is not going to be installed E: Unable to correct problems, you have held broken packages.  What is the problem here? I read somewhere that "UbuntuGIS stable ppa (launchpad.net/~ubuntugis/+archive/ubuntu/ppa) does not have any 20.04 packages." Is there a workaround for this? Everything works if I try it on Ubuntu 18.04.

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


I uninstalled Unity from Ubuntu mistakenly. When I restart the computer I get      The system is running low-graphics mode   I have tried different commands   sudo apt-get autoclean sudo apt-get autoremove   etc but the problem persists.  How can I solve this?

I'm running Ubuntu 14.04. I uninstalled Unity from the Software Center by mistake. How do I reinstall it?


UPDATE: Apparently this ad  and its relative mertis have been discussed. But the official decision was, apparently, to remove the ad from Stack Exchange:    Has the Careers 2.0 collective changed its mind, or was this an accident?  Looks like this ad was :   (Emphasis mine)   I'm not 100% sure this is the appropriate place to discuss Careers 2.0 advertising, but I found this ad to be a bit... uh... weird.  Are those power cables electrocuting that unsupervised baby?!? Somebody call family and children services!

Here is the ad:    Some (including myself) have found the ad to be somewhat offensive (it's quite weird to say the least). Though I recognize the symbolic nature of the ad (staying at home yet working at the same time), the baby looks quite old (especially to still be wearing diapers).  What's worse is the fact that this ad seems to convey that children can be ignored while parents are occupied with something else (very poor timing considering ).   Not only that but the child is right next to (what appears to be) the power cables for the two PCs - a serious electrical shock hazard.  Could we maybe make some adjustments to the ad?


The confusion is to do a date validation in HTML. Is it necessary that the input type has to be "Date". Or can do the validation as input type is "text"?  I tried following JavaScript to alert user when one date is eariler than another. The input field for these values type were set as "text".  Is there another way to do while type is "text" or do i have to change the type?  function checkDate(){     var date1=new Date();     var date2=new Date();     date1=$("#txtStartDate").val();     date2=$("#txtCloseDate").val();     if(date1<date2){         alert("The End date can't be earlier than the Start date !!");         }     }   And I am calling this function onChange event at date 2 input.  From the debugger the function is calling but it's not validating.

Can someone suggest a way to compare the values of two dates greater than, less than, and not in the past using JavaScript? The values will be coming from text boxes.


Boot screen does not accept changes to boot order.  I need to change to boot from usb in order to recover my system which is broken following failed upgrade to 18.01

I have a laptop with Ubuntu installed as the only OS. I also have a USB stick with a Windows 7 installation on it. I want to install Windows from the USB stick on my laptop but when I try to restart the laptop to get access to BIOS, I can't seem to find the command for it, its like it skips everything and just says Ubuntu and then takes me to the login screen.  How do I change the boot priority to USB in Ubuntu?


I have reviewed multiple scripts that address primarily changes on a retina display.  I have a standard monitor (iMac 27").  The line of code that seems to give me trouble is:  tell application "System Events" to tell process "System Preferences" to tell window "iMac"  I have substituted the name of the window containing the parameters of my monitor (see picture).  What am I doing wrong here?  Thanks.

How can I change change screen resolution using AppleScript? If AppleScript can't do it, what about Terminal?  I tried with examples at , but they don't work anymore. I'm on MacBookPro Retina.  This is how the script definitively should start:      tell application "System Preferences"         activate         reveal anchor "displaysDisplayTab" of pane id "com.apple.preference.displays"     end tell     tell application "System Events"         tell application process "System Preferences"           -- insert magic         end tell     end tell   Now I just need to click on "Scaled" and select different display resolutions, but I don't know how these buttons are "called".


I baked a smoke simulation but I just want to freeze the last frame so you see that the entire time. How can I do that? Im using Blender 2.83

I am attempting to render an animation where the camera rotates around an object that is engulfed in flames. My goal is to have the camera rotate but for the flames to be immobile throughout.   Is this possible? I have seen tutorials where the flames are made to slow down, but none where they are motionless.


I just did a fresh install of Ubuntu 16.04 that I set to log in automatically. When it loads up all I get is the desktop wall paper but not top panel or unity side bar. Previously I was using Ubuntu 16.04 Mate edition and everything worked great. I read this question  but I could not get to a tty screen like the poster in that thread. When I did Ctrl+Alt+F1 all I would get is a blank screen. I've tried switching monitor inputs and going from my nvidia card to the onboard graphics but nothing seems to work. I'm just going to switch back to Mate for now but I would really want to check out what's new in Unity. Thanks for any and all help!

When I login, nothing happens.   I am presented with my desktop wallpaper.    No Dash, no Launcher, nothing.


I have a challenge about a cat in a trip where he can walk in the way of $d, d+1, d+2...$ and the sum of that should give $N$, given an $N$, how many ways of chosing $d$ are posible?  Example:  $N=30$ -> $Ans=3$  $d_1=4; d_2=6; d_3=8$   For $d_1: 4 + 5 + 6 + 7 + 8 = 30$  Edit:  Another way to see it is: How many subsets in the sumation up to N are posible in the way $(\sum (d+n) - \sum(d-1))$=N

I have to solve this task:   Find the number of ways to present $1050$ as sum of consecutive positive integers.  I was thinking if factorization can help there: $$1050 = 2 \cdot  3 \cdot  5^2 \cdot  7 $$ but I am not sure how to use that information (if there is a sense) example I can solve something similar but on smaller scale: \begin{align} 15 &= 15  \\ &= 7+8 \\ &=4+5+6 \\ &= 1+2+3+4+5 \end{align} ($4$ ways)


Failed to fetch cdrom://Ubuntu 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417)/dists/trusty/main/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs  W: Failed to fetch cdrom://Ubuntu 14.04 LTS _Trusty Tahr_ - Release amd64 (20140417)/dists/trusty/restricted/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs  W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/Release.gpg  Connection failed  E: Some index files failed to download. They have been ignored, or old ones used instead.

When updating I got this error message:  W:Failed to fetch cdrom://Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)/dists/oneiric/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W:Failed to fetch http://ppa.launchpad.net/synce/ubuntu/dists/your_ubuntu_version/main/source/Sources  404  Not Found   What to do?


Show that a function defined on a domain $D$ symmetric about the origin can be expressed in a unique way as the sum of an even and an odd function.    Sorry but I have no idea about how to start.

What is the logic/thinking process behind deriving an expression for even and odd functions in terms of $f(x)$ and $f(-x)$?  I've been pondering about it for a few hours now, and I'm still not sure how one proceeds from the properties of even and odd functions to derive: $$\begin{align*} E(x) &= \frac{f(x) + f(-x)}{2}\\ O(x) &= \frac{f(x) - f(-x)}{2} \end{align*}$$ What is the logic and thought process from using the respective even and odd properties, $$\begin{align*} f(-x) &= f(x)\\    f(-x) &= -f(x) \end{align*}$$   to derive $E(x)$ and $O(x)$?    The best I get to is: For even: $f(x)-f(-x)=0$ and for odd: $f(x)+f(-x)=0$  Given the definition of $E(x)$ and $O(x)$, it makes a lot of sense (hindsight usually is) but starting from just the properties. Wow, I feel I'm missing something crucial.


I followed  to install Windows 10 on an external USB drive. It all works great. The way to allow the Mac to boot is as follows(this is done inside the command line when booting from the Windows installer USB):  To make your installation bootable, enter bcdboot W:\Windows /l en-us /s Z: /f UEFI. This will create the boot files in your EFI partition.  From what I understand, the Mac has a partition where UEFI systems can boot and in this particular case boots Windows from that partition and then control is passed to whatever is located on the external drive. I became aware of this . I would like to be able to boot this Windows installation from other Macs without running the bcdboot command as that would imply booting the Windows installer and running cumbersome operations. I also know that a USB stick can boot the system (this is what macOS installer and Windows installed do). So... my question is this: Can you create a USB stick that boots up the system and passes control to my USB drive with Windows installed on it? Or maybe change the Windows USB drive to allow it to boot? I don't understand the whole booting process but my guess would be that a bootloader could be installed on a USB stick and that would allow me to boot Windows.

I need to run Visual Studio on my MacBook Pro and I need Windows to do that. The easiest and well known way to install Windows on a Mac is by running the Boot Camp app on the Mac and let it do what's necessary. The problem is that I don't want to partition the Internal SSD so the remaining option is to install Boot Camp Windows 10 on an External Drive and boot it every time I need it by plugging in my external USB 3.0 HDD. Is this achievable?


The RSA private key contains 2 primes (of about 4096 bits each), and I only know their product (called modulus) and the modular inverse (called coefficient).  How do I recover the RSA primes from the modulus and the coefficient, i.e. how do I implement get_primes below?    def get_modulus_and_coefficient(prime1, prime2):   assert prime1 > prime2   coefficient = modinv(prime2, prime1)  # Modular inverse of prime2 modulo prime1.   assert coefficient * prime2 % prime1 == 1   modulus = prime1 * prime2   return modulus, coefficient  def get_primes(modulus, coefficient):   ... prime1, prime2 = ...   assert get_modulus_and_coefficient(prime1, prime2) == (modulus, coefficient)   return prime1, prime2   Is there a well known-recovery method published for this?  FYI This question is different from  . The other question asks for recovery of the primes $p_1$ and $p_2$ from $n$, $e$, $d$. This question asks for recovery of the primes $p_1$ and $p_2$ from $n$ and $q_\mathrm{inv}=p_2^{-1}\mod p_1$. The answer for the other question doesn't help at all with this question.

Given the public key (n, e) and private exponent (d), how to calculate CRT parameters (p, q, dP, dQ, and qInv) of this RSA key pair?


How to prove in a formal system (like HFOL) the following formula $\forall x\exists y(x = y)$?  Obviously, we would like to use the axiom $x = x$ and then use a rule for introducing $\exists$, but how do we get $x = y$?

Give a deduction of $\forall y \exists x (x=y)$  My thinking is I can prove $\exists x(x=y)$ then use generalization theorem， which is equivalent to prove $\neg \forall x \neg (x=y)$ but I got stuck proving this... thanks in advance  Sorry that I did not specify what deduction system that I want to use here, it is the deduction sequence  where ai is either Axiom or original hypothesis or obtained from MP


May be I will do this. Or Maybe I will do this. Which of the two is correct? And one of those is correct, then is there another context where the other form of Maybe/May be is used?

What is the difference in meaning and usage between maybe and may be? Are they synonymous?


I want to read a string from the console.  Using scanf or fgets however, it seems to me that it's only possible to read a string of a fixed maximum size. Even worse, there seems to be no way of checking how many characters were entered in case the user enters too much (in that case I could simply realloc the array in order for the string to fit into the array).  I read that I'm supposed to read one character at a time in the answer to , however I don't know how to read one character at a time without having the user press enter after each character.  How can I do it?

What is the simplest way to read a full line in a C console program The text entered might have a variable length and we can't make any assumption about its content.


I have used R to form a 95% prediction interval for the number of endemic species on an island. My lower bound is negative – is that mathematically sound?  In the linear model used in the prediction interval, the data used are:  Area Surface area of island, hectares DiscSC Distance from Santa Cruz, kilometres Elevation Elevation of higher point in metres and it is coded as such:   selected.model <- lm(ES ~ Area + Elevation + DistSC + I(Elevation^2)                      + (Elevation:DistSC) + (Area:Elevation))    and stepwise regression was performed to find this "best" model   I'm not exactly sure how a prediction interval works. I just want to make sure it is OK. Obviously a negative number of species is incorrect, but I know it takes into account the uncertainty of the mean as well as data scatter.


I'm using a HP Laserjet Pro M28a with Ubuntu 18.04. Printing is fine, but I couldn't get the scanner portion to work for quite a while. I've installed the Debian packages for HPLIP 3.17.10 (official repo), then 3.19.8 (PPA) and finally 3.19.11 (other PPA).  Scanner still didn't work. Out of desperation, I've run sudo hp-plugin -i as suggested in other SO posts and suddenly the scanner works, too.  Unfortunately, this script has now dumped a bunch of unowned binaries into my filesystem, specifically:  /usr/lib/sane/hpgt2500_ntdcmsdll-x86_64.so /usr/lib/sane/libsane-hp2000S1-x86_64.so.1.0.25 /usr/lib/sane/libsane-hpgt2500-x86_64.so.1.0.27 /usr/lib64/sane/hpgt2500_ntdcmsdll-x86_64.so /usr/lib64/sane/libsane-hp2000S1-x86_64.so.1.0.25 /usr/lib64/sane/libsane-hpgt2500-x86_64.so.1.0.27 /usr/local/lib/libjpeg-x86_64.so.9.2.0 /usr/share/hplip/data/firmware/hp_laserjet_1000.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_1005_series.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_1018.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_1020.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_p1005.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_p1006.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_p1007.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_p1008.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_p1009.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_p1505.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_professional_p1102.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_professional_p1102w.fw.gz /usr/share/hplip/data/firmware/hp_laserjet_professional_p1566.fw.gz /usr/share/hplip/data/plugins/license.txt /usr/share/hplip/fax/plugins/fax_marvell-x86_64.so /usr/share/hplip/plugin.spec /usr/share/hplip/prnt/plugins/hbpl1-x86_64.so /usr/share/hplip/prnt/plugins/lj-x86_64.so /usr/share/hplip/scan/plugins/bb_escl-x86_64.so /usr/share/hplip/scan/plugins/bb_marvell-x86_64.so /usr/share/hplip/scan/plugins/bb_orblite-x86_64.so /usr/share/hplip/scan/plugins/bb_soap-x86_64.so /usr/share/hplip/scan/plugins/bb_soapht-x86_64.so   I assume there is some stupid HP license stuff that prevents these files from being packaged regularly, but is there any dpkg-based way to either install or at least properly manage these files? I'm particularly annoyed by the extra JPEG library in /usr/local/lib, this is a surefire way to mess up some totally unrelated package down the road...  Note: I'm not asking how to install the HP plugins, I've already done that. I'm asking how to avoid a future mess with unowned libraries in the system lib directories.

Let's assume that one has some modern HP printer and/or scanner which is not supported by HPLIP package from official repository. Currently Ubuntu versions have :  trusty (14.04LTS): 3.14.3-0ubuntu3.4 xenial (16.04LTS): 3.16.3+repack0-1 bionic (18.04LTS): 3.17.10+repack0-5 focal (20.04LTS): 3.20.3+dfsg0-2 groovy (20.10): 3.20.5+dfsg0-3build1 hirsute (21.04): 3.21.2+dfsg1-2   What can one do if printer is supported in newer version of HPLIP (checked this in )?


I'm planning to fly to Las Vegas on holiday and drive to Toronto in a used car. I live in the UK and am unfamiliar with licensing laws in Nevada (and the rest of the US!) - though from what I understand the car would need insuring and registering before I could drive it. These are my questions:   Do I simply need to ensure my full UK driving licence is valid for the insurance I buy? Can insurance be purchased instantly online? What is sufficient for proving I have it when registering the car? How do I register the car and can I do it online? Can insurance and registration be handled on the same day? Is there anything I need to be aware of when driving between various states and Canada? These are the states I plan to visit:   Nevada Arizona Utah Colorado Kansas Missouri Arkansas Tennessee Kentucky Indiana Illinois Michigan    Just to point out in advance, I'm well aware that I could hire a car, but that's not an answer to my questions.  Thanks!

For tourists coming to the US, getting a car is a great way to get around, especially if you want to see the national parks. Rental, especially for younger drivers, can be very expensive, so buying a car is a good alternative. The process for buying and registering a car is aimed at US citizens and not tourists, so it is a little hard to find all the information.  How can a tourist buy a car in the US to take on a road trip, and what steps must they take?


If I use my miles to buy an American Economy MileSAAver tickets, do I get to pick my seats when I book the flight?

I'm looking into using AA rewards miles toward a family flight next summer.  I've looked at the AA award chart and the MileSAAver Economy tickets sound appealing because of the low cost in miles, but I still have some questions.  We would need four seats as close together as possible--would that be hard to do using MileSAAver Economy tickets?  Are multiple tickets usually spread around the plane or put on multiple flights?  The chart mentioned that SAAver Economy tickets were a good option "if your plans are flexible"--does that mean that a booked flight could be changed?  Overall, I'm trying to get a better sense of how the MileSAAver Economy miles work and if there are any caveats I should know about.  I really appreciate your help!


If we were able to push a 2x2 piece of wood that is the length of our solar system, how would it behave? My colleague says since its all part of the same molecular structure, the whole piece of wood would move. But my understanding is different. The informational input from one end, to the other, would be faster than the speed of light and as we all know, we cannot go faster than the speed of light. So from my perspective and understanding is that the initial push would need to travel through the entirety of the 2x2 before it started moving. The variables here can be a huge influence but lets say that we are in the vacuum of space where the 2x2 would not be effected by gravity. If anyone could give me a solid answer, that would be greatly appreciated! I am not a physics person so I apologize in advance if the information given here is not enough!

Is it possible for information (like 1 and 0s) to be transmitted faster than light?   For instance, take a rigid pole of several AU in length. Now say you have a person on each end, and one of them starts pulling and pushing on his/her end.   The person on the opposite end should receive the pushes and pulls instantaneously as no particle is making the full journey.  Would this actually work?


I'm trying to use String.valueOf() to replace the null when i'm calling some method.But it still shows nullpointerexception. This may be simple but i'm missing something.  I have statement like this   myvar = this.kind.name().toLowerCase()      It is throwing java.lang.NullPointerException. Im trying to keep string "NULL" whenever i get NPE. so i tried this  myvar = String.valueOf(this.kind.name().toLowerCase()) -- not working   I have found from other posts that it may not work as we have overloaded method String.valueOf(char[]) and String.valueOf(object) and suggested to use below. But still it s not working. How do i assign string null in this case?  myvar = String.valueOf((this.kind.name().toLowerCase()) null))

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?


Environmental pressures are the catalyst of evolution. Pushing a species to adapt to changes therein. My question is can these mechanisms cause significant adaptation over one generation(parent-> child). My thinking is the pressure of the equivalent of human trauma in a species(depending on neurological and biochemical makeup of said species) would be enough to induce genetic influence.  If not, what is the minimum theorized timeframe for environmental pressures to act?   Edit: This is not a duplicate, the previous question is about one animal's lifetime

I am wondering if animals do evolve even after birth and gain DNA changes that give them advantages and make them more suitable to the environment while they are alive, then pass these "enhancements" to their children  UPDATE  After all, cell do split and multiply when the animal is alive, and it could end up with a totally different cells than the one born with, so if a mutation happened during this period that led for it to be the dominant "property", what stops it from being passed on? Is there a research on this?


Please, help to understand what is wrong in next code, since I have pretty modest knowledge in Java generics. Can't find out why I getting pageData is null in class BPage, when in APage it's fine. Thanks in advance. I've simplified the excample classes to several rows:  public abstract class PageData { }  public abstract class Page<T extends PageData> {     protected T pageData;     public Page(T pageData) {         this.pageData = pageData;     } }  public class APageData extends PageData {     public final String locator = "//*[@id=\"id_1\"]"; } public class APage<T extends APageData> extends Page<APageData> {     public APage(T pageData) {         super(pageData);     }      public void getLocator() {         System.out.println(pageData.locator);     } }   public class BPageData extends APageData {     public final String locator = "//*[@class=\"class_1\"]"; } public class BPage extends APage<BPageData> {     public BPage(BPageData pageData) {         super(pageData);     } }   APage aPage = new APage(new APageData()); aPage.getLocator();  // locator found, OK  BPage bPage = new BPage(new BPageData()); bPage.getLocator();  //pageData  NullPointerException


In the , in the logic diagram, there are 2 inverters in series:   What is the point of these inverters in series?

I have recently been looking at the datasheets for the  IC in order to see if it was suitable for my project, and have come across the following logic diagram which strikes me as a little bit odd:         – Schematic created using   For each of the inputs Yn, there are two NOT gates after the triple-input NAND gate; I don't understand why this is necessary as simple boolean logic tells us:  $$\overline{\overline{A}}\equiv A\qquad \forall A \in \{\text{TRUE}, \text{FALSE}\}$$  Therefore I am assuming there is some electronic based reason why there are two inverters before the output? I have heard not gates called Inverting buffers before, and these supposedly isolate the circuit before and after, however, I cannot claim to understand the use of this so I'd appreciate any enlightenment!


I'm new to Python. I see : used in list indices especially when it's associated with function calls.   Python 2.7 documentation suggests that lists.append translates to a[len(a):] = [x]. Why does one need to suffix len(a) with a colon?  I understand that : is used to identify keys in dictionary.

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


I find the standard examples of active and passive voice on, say, Purdue Owl to be pretty obvious. For example, "He kicked the ball" versus "The ball was kicked by him."  For the examples, Someone was talking about whether these different sentences were passive or active voice during a story critique. But when you have "Her hair was dark" vs "She had dark hair." It doesn't seem that either of these would be passive voice. "Her hair was dark" is passive voice? because in passive voice the subject should be receiving the action of the sentence, but that doesn't look to be the case here—her hair is simply dark and only an auxiliary verb is present.   Also, someone was saying "she looked young" is passive, but "she was young" is not passive. But this makes no sense to me. Are they perhaps meaning one is less precise, and they weren't talking about passive/active voice at all when they were saying it was passive? Because all I'm seeing that's different about these two phrases is a narrator that is either uncertain or certain about the subject's age.

How can I reliably and accurately identify the passive voice in writing or speech? I'm not interested in advice about whether or not to use it yet... I just want to know for sure what it is, so that I don't look as stupid as .


A few months ago (?) there were some changes to the site aesthetics, including toning down the use of a contrasting background for code and deleted posts. I'd prefer they both come back, but the issue with code seems like a personal preference; I don't have a pragmatic argument and aren't interested in forcing my opinion about it on the world. However, removing the pink tint on deleted posts is a step backward in practical terms.1  It was very clear when something was deleted. I'm a mod, and for me there's a significant practical value to that. Of course that the post has been deleted is not hidden -- there is still a banner clearly stating the fact.  The visual significance of this diminishes with the size of the post, however. A common context for deletions are brand new users who post questions as answers.  Having a glaring visual element (the pink background) no doubt made something pop.  The banner of course is there, and you receive a notification.  Keep in mind, though, this is already someone who wrote up a question and clicked Post Your Answer.  I think long term users may not realize how relatively complex (compared to eg. bb style forums) the SE interface is, and that a normal reaction to that would to to tune out things in accord with whatever you think you are looking at. So: That's several pragmatic reasons to go with the contrasted background; I really don't see any for not doing so, meaning this seems like a sacrifice of functionality for trivial aesthetics.   There's a 10K rep bar on seeing deleted posts, so if you don't know what I'm on about that's probably why.  The bar does not apply to your own posts if deleted.

I recently noticed that the red background highlight behind deleted posts is now a much lighter shade of red than it used to be in the past.  While I'm generally in favor of having higher contrast ratios for text across SE, I think this crosses the line a bit. The previous background was readable to me and didn't pose any contrast ratio issues to me. On the other hand, the new color is less visible than the old one and difficult to see on monitors with higher contrast settings. In other words, the contrast ratio between the red background and the white surroundings is too low.  As a test to see the magnitude of this issue, I tried raising my display contrast. By default, it's set to 20%, but setting it to 40% made it barely visible unless I really squinted at it, and setting it to 50% made it just about invisible. Some users may turn up their monitor's contrast to a higher level to better read text on screen, but this change makes it more difficult for those users who engage in moderation to identify deleted posts, especially if they've scrolled down.  Can we please make the shade of red that appears underneath deleted posts be darker (while still retaining WCAG Level 2 AA compatibility)?  Here's an image of the current configuration:        ...and the previous configuration:        I hope that this is one of the  of the CSS refactor.


The following command in the ubuntu terminal gives an error   sudo apt-get update   This is the error message  W: The repository 'cdrom://Xubuntu 16.04 LTS _Xenial Xerus_ - Release  amd64 (20160420.1) xenial Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore  potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user  configuration details. E: Failed to fetch cdrom://Xubuntu 16.04 LTS _Xenial Xerus_ - Release  amd64 (20160420.1)/dists/xenial/main/binary-amd64/Packages  Please use  apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot  be used to add new CD-ROMs  E: Some index files failed to download. They have been ignored, or old  ones used instead.

When updating I got this error message:  W:Failed to fetch cdrom://Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)/dists/oneiric/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W:Failed to fetch http://ppa.launchpad.net/synce/ubuntu/dists/your_ubuntu_version/main/source/Sources  404  Not Found   What to do?


Could any one tell me how to show that only ideals of above ring are $(0)$ and the whole ring?   My thought was to show that by taking any proper ideal if we can prove identity element belongs to it then we can generate the whole ring?  Thanks for helping

Let integer $n\geq 1$. I have obtained that for any field $k$, the matrix ring $M_n(k)$ is simple, i.e., $M_n(k)$ contains no nonzero proper two sided ideals. Now I want to prove that: for any ring $A$ (not necessarily commutative), the matrix ring $M_n(A)$ is simple if and only if $A$ is simple.   How to prove?


I've done a big update on my PC. He asked me if I want to upgrade from 16.04 to 17.10 but I don't know if I can lose some data or something..can someone explain me this situation? Thanks in Advice!

I am currently using Ubuntu 10.04. I know there is a 10.10 release, but can I upgrade directly to 11.04? Could you walk me through the steps please?


Im sorry, but i just want to make clear.  I have a 12/2 going from the panel through conduit (copper wire) to the double gang box.  I want to have each gfci to run independently without using the load.  Why, in case one shuts off the other isn't affected. the double gang box is standard.  the device is a leviton 20 amps.  I was told that you can run 12/2 from the panel to the first gfci black and white.  Then connect the second gfci using a jumper and attaching it to he second gfci.  Is this acceptable by code. we use a washer,dryer in the laundry and the garage heavy machinery.  so why should this be a problem running two independent? please advise and again thank you. larry

Cam I have two GFCIs connected to one double gang box in my laundry room and if so can I do a single line connection so that they both can work independently?  I have a 12/2 going from the panel through conduit (copper wire) to the double gang box. I want to have each GFCI to run independently without using the load. Why, in case one shuts off the other isn't affected. the double gang box is standard. the device is a Leviton 20 amps. I was told that you can run 12/2 from the panel to the first GFCI black and white. Then connect the second GFCI using a jumper and attaching it to he second GFCI. Is this acceptable by code. we use a washer,dryer in the laundry and the garage heavy machinery. so why should this be a problem running two independent?


I just received a new Alienware computer with Ubuntu pre-installed, since updated to version 12.04.  I would like to install Windows 7 or 8 (I have installation discs for both) to run some programs.  Any advice for a Ubuntu novice on how to do this?  Thanks!

I just installed Ubuntu, a full install removing the prior OS. I was forced to remove  from my  because of the max four partitions already being there. I didn't lose anything, all backed up. However, now I am looking to create another partition and install Windows 7 on it.   Do I also need some sort of boot loader that lets me choose which to boot?


From doing research, I think I understand that the order of wlan0 and wlan1 ( and so on ) is determined by the order that the USB devices are recognized.  My question is whether or not this order is deterministic;  once plugged in and recognized in a specific order, will two or more adapters continue to be recognized in that order in subsequent reboots?  If not, is there a way to influence that order to become deterministic?

How or where does Linux determine the assignment of a network device? Specifically, wlan0 or wlan1 for wireless USB devices.  I plugged in a TP USB wireless a while ago, and it was assigned wlan0. I removed it. This week I plugged in an Edimax USB wireless device and it comes up as wlan1. I removed it today to try a second Edimax USB wireless device (I bought two) and now it comes up wlan2.  I know enough of Unix/Linux to know this is being configured somewhere, and if I delete the unused config file I can make the latest Edimax become wlan0. But how/where?


I've been writing in C++ lately and I'm getting confused with .cpp vs .h — when to use them and what should go in them. I've been reading that you should put function definitions in a separate .cpp file, and headers should be used for declarations, but how do I use the separate .cpp file?  Do I #include it or what? I'm looking for clarification on .h and .cpp and what should go where and how to include separate .cpp files.

I am new to C++ and I had a few general questions about code separation. I have currently built a small application, all in one file.  What I want to do now is convert this into separate files such that they contain similar code or whatnot.  My real question right now is, how do I know how to separate things? What is the invisible margin that code should be separated at?    Also, what's the point of header files? Is it to forward declare methods and classes so I can use them in my code before they are included by the linker during compilation?    Any insight into methods or best practises would be great, thanks!


My OS was updated to 16.04  During the upgrade there was a problem with mysql. This is the error message:  Setting up mysql-common (5.7.19-0ubuntu0.16.04.1) ... update-alternatives: error: alternative link /etc/mysql/my.cnf is already managed by my.cnf.bak dpkg: error processing package mysql-common (--configure):  subprocess installed post-installation script returned error exit status 2 Errors were encountered while processing:  mysql-common E: Sub-process /usr/bin/dpkg returned an error code (1)   I tried the solutions that were proposed in the following questions and none of them worked for me. The solutions that were tried:         Is there any suggestion for another solution? Thanks  The output of ls -l /etc/mysql is:   drwxr-xr-x 2 root root 4096 Sep 22 17:29 conf.d -rw-r--r-- 1 root root  839 Sep 19 13:52 my.cnf.bak -rw-r--r-- 1 root root  839 Jan 21  2017 my.cnf.fallback -rw-r--r-- 1 root root  839 Sep 19 13:51 mysql.cnf

My overall upgrade went well, but I am left with a critically lingering issue of mysql-server not being able to install itself, and nothing I am trying gets it to work.  This is the error I see when trying to install/reinstall it:  Setting up mysql-server-5.7 (5.7.11-0ubuntu6) ... Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details. invoke-rc.d: initscript mysql, action "start" failed. dpkg: error processing package mysql-server-5.7 (--configure):  subprocess installed post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of mysql-server:  mysql-server depends on mysql-server-5.7; however:   Package mysql-server-5.7 is not configured yet.  dpkg: error processing package mysql-server (--configure):  dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure.                    Processing triggers for systemd (229-4ubuntu4) ... Processing triggers for ureadahead (0.100.0-19) ... Errors were encountered while processing:  mysql-server-5.7  mysql-server E: Sub-process /usr/bin/dpkg returned an error code (1)   I've tried completely removing it, though doing so attempts to install MariaDB because of dependencies (?). Any suggestions on what I can do to fix this would be most welcome.  EDIT: Looks like I'm not the only one:


I have this equation:  \begin{equation} \begin{split} t(E,T)&= \left[ A  \\ &\quad +B \right] ^{-1} \\ &\quad \ln\left(  C \right)  \end{split} \end{equation}   But it says that there is an error. This error because I put the end bracket (right one) in the second line. I need to keep it in the second line. Do you know some idea of solving this issue?  Thanks in advance.

I want to align equations (using the align environment from the amsmath package) inside matching \left( and \right) commands. For example:  \documentclass[a4paper,12pt]{article}  \usepackage{amsmath}  \begin{document}  \begin{align}     a \left( b &= c \right)\\     d \left( e &= f \right) \end{align}  \end{document}   But that code gives this error:     Extra }, or forgotten \right.   The error disappears when I remove the delimiters. Is there a workaround for this?


How should I undo this connection? It doesn't seem to unscrew, though part of it will move down towards the boiler although this doesnt seem to make it disconnect (I havent tried forcing this though as I don't want it to break)  Its the mains cold water inlet to a small boiler by the way.  Many thanks]

The plastic tubing supplying filtered water to our refrigerator currently runs below a suspended ceiling. I want to reroute it above. How do I disconnect it without damage from either the union or tee, so I can reconnect once moved? The tee is labeled NSF-51 Parker Parflex size 4. The union has no discernible markings. I believe I would rather disconnect the union rather than the tee. I didn't want to just start tugging. I have found similar fittings for sale online, but no instructions for use.  Here is the union:   And here is the tee:


Excluding the mustache villian, what was the first movie to have a person tied to a train track? Did the movie scene come from a book?

Whenever someone thinks about silent cinema the image of the laughing villain, twirling his mustache, and tying the hapless blonde beauty to the railroad, pops up in our collective memory. But in which movie (or movies) did that particular image first appear?


I am trying that a variable that I have just defined has the value of an object and that I can also add more information to it at the same "level" Something like that:   let obj1 = {   name: "jhon",     address: {       city: "abc123",       country: "def456",       zipcode: "123456",     },     job: {       position: "qwe123",       experience: "12 years",     }, }  let obj2 = {   info1: "abc123456",   info2: "12345678978",   info3: "1234567d78778", }  let myobj = {    name: "jhon",   address: {     city: "abc123",     country: "def456",     zipcode: "123456",   },   job: {     position: "qwe123",     experience: "12 years",   },      info1: "abc123456",   info2: "12345678978",   info3: "1234567d78778",    }  console.log(obj1) console.log(obj2) console.log(myobj)    Let me explain, I want "myobj" to be equal to obj1 and obj2. obj1 and obj2 come from different parts and I want the data to be in "myobj" at the same level, as shown in the code

I need to be able to merge two (very simple) JavaScript objects at runtime.  For example I'd like to:  var obj1 = { food: 'pizza', car: 'ford' } var obj2 = { animal: 'dog' }  obj1.merge(obj2);  //obj1 now has three properties: food, car, and animal   Does anyone have a script for this or know of a built in way to do this?  I do not need recursion, and I do not need to merge functions, just methods on flat objects.


I got review banned for 7 days on March 3rd, 2014. I have the habit to click on Review whenever I am on Stack Overflow's page. Yesterday it was showing me the following regular message     You have failed too many recent review audits – looks like you might need a break. Come back in 4 days to continue reviewing.   So there were 4 days left of my review ban. But this morning when I click on the Review link, it allowed me to perform a review. You can see my          I double checked all the reviews, there isn't any failure in today's reviews.   Now again when I click on review again it shows me same message as before, but with a 3 day warning      You have failed too many recent review audits – looks like you might need a break. Come back in 3 days to continue reviewing.   First I thought that it was because of some of my helpful flags that my review ban is lifted automatically by the system. But now I think that this is a bug in the system. It shouldn't allow me to review  for the next 3 days.   Update This issue is re-produced with me just before few minutes. I have notice one thing that this happens only one time, meaning after ban this happens one time only and once it happens it doesnt happens again till the ban period is over.

As the title suggests, I am blocked for 7 days for reviewing the posts!   Today when I clicked on the counter for reviews (I don't know the exact name for that), I was able to review the content. I reviewed 2 posts and responded as needed!   Here is the thing: I was able to review even while blocked for being stupid while reviewing!  Was it a bug or something else? It happened just a bit ago.        There are the reviews that I did just an hour ago. When I clicked the same link, it reminded me that I am not able to review posts for 3 days more. (7 was the real count!)        I have no idea if this was a bug! Can anyone tell me?


Indian toposheets (pre-2000 series) of 1:50k scale are in Polyconic projection, with Everest 1956 spheroid and India-nepal datum. How do I create a custom CRS in QGIS to represent this, so that I can then reproject the topo corners (tic points) to UTM-WGS 84 and then geo-reference the toposheet.

I have a shapefile with the following projection information:  PROJCS["Nepal_india_boundary",GEOGCS["Nepal_india_Geo",DATUM["D_Everest_India_Nepal",SPHEROID["Everest_Definition_1962",6377301.243,300.8017255]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",500000.0],PARAMETER["Central_Meridian",84.0],PARAMETER["Standard_Parallel_1",26.666667],PARAMETER["Standard_Parallel_2",29.333333],PARAMETER["Scale_Factor",0.9997],PARAMETER["Latitude_Of_Origin",28.002808],UNIT["Meter",1.0]]   Which transformation parameters (preferably 7 parameters) can I use to transform the shapefile into WGS84 (decimal degree) system?


I would like to share my situation because maybe helpful to others, and I need some advice.  I administer a VPS with some web servers and high traffic.  The systems specs are x2 Xeon E2620 with 2 cores, 18Gb ram and 800Gb HDD.  The first step when I got full access was check the server configuration.  The system holds:   Apache2 php-cgi 5.3.3 (prefork) MySQL 5.1 Prestashop (1.4 - 1.6) APC   At first sight (later confirmed), the server settings and the system architecture is not optimal.  The server is busy almost all time and web access very slow.  So, I think I have a couple of alternatives to circumvent this situation because the traffic only grows.   Optimize the current settings could be only a temporary solution.   It means tuning Apache, preforks, MySQL, uninstalling unneeded software... etc.  OR   Change the system architecture thinking in scalability. ( better temp. solution before invest more $$ scaling horizontally)   My idea, and my doubt is what do you recommend for scale.  nginx, php-fpm, varnish, APC OR nginx working together with Apache.  I think first is better because they all still runs in the same machine.  Thanks.

This is a  about capacity planning for web sites. Related:      What are some recommended tools and methods of capacity planning for web sites and web-applications? Please feel free to describe different tools and techniques for different web-servers, frameworks, etc., as well as best-practices that apply to web servers in general.


In my first playthrough at level 40 I ran out of useful-sounding perks and started wondering about V.A.T.S effectiveness. There are 25 perks directly benefiting V.A.T.S out of 93 perks in total (yes, I counted), which makes me think that it is supposed to be a much more substantial aspect of the game than I (and perhaps others that are used to pulling the trigger themselves) can fathom.  Is V.A.T.S really just statistics, convenience and cinematic splatter or is there a whole other angle I'm not seeing?    EDIT: I know about Threat Detection and Critical Strikes. I'm just wondering why that would merit 1/4 of all perks being about V.A.T.S when it seems like it is just an alternative play style to FPS. Can someone give me a concrete breakdown of how effectively V.A.T.S can be used? I believe I'm not alone in saying that there might be less obvious nuances to it that justify its existence.

Throughout my playthrough of Fallout 4, I've never once felt the need to use VATS. I never even considered using it since my understanding of it is that it's just letting the game do the shooting or hitting for you and you're leaving it up to RNG to win a battle.   The only reason I see to use V.A.T.S. is for the critical hits (assuming that criticals only occur through VATS outside of sneak attacks) and for determining if a distant NPC is friend or foe.  What are (if any) the other reasons to use V.A.T.S.?


I know this might be an easy task but I cannot seem to get anywhere with this proof:  I am given this: $\exp(x)=$ $\sum_{n=0}^\infty \frac{x^n}{n!}$.  I have to prove that: $\exp(x+y)=\exp(x)\exp(y)$.

I am trying to prove $\exp(x+y) = \exp(x) \exp(y)$.  I may use that $$\exp(x) = \sum_{n=0}^\infty \frac {x^n}{n!}$$ I further know how to multiply two power series in one point, i.e. if $f(x) = \sum_{n=0}^\infty c_n(x-a)^n$ and $g(x) = \sum_{k=0}^\infty d_n(x-a)^n$ then $$ f(x)g(x) = \sum_{n=0}^\infty e_n(x-a)^n $$ with $$ e_n = \sum_{m=0}^n c_md_{n-m} $$


Which sentence below is grammatically correct?  I didn't answer your questions because I had fallen asleep early last night.  I didn't answer your questions because I fell asleep early last night.   I'm leaning more toward the second sentence since the time was specified, and I don't see why the past perfect is needed. Please, correct me if I'm wrong, and thanks in advance.

My question might seem to be stupid enough, it's basic grammar, I believe; however, I'm at my wits' end. Should we use Past perfect or Past Simple in the following sentence:     He promised/ had promised to turn up at 4, but appeared at 9?


Preface: I'm not a trained sysadmin. Just trying to learn as I go. Please be gentle. :)  Background: So we rented a VPS to act as our domain controller. Joined ~500 of our laptops to it. GPOs were working perfectly (thanks to advice from grawity and others on my previous question). But the VPS was very unstable, kept restarting around every 10 mins for reasons I couldn't figure out. In the end I installed 2012R2 on the VPS instead of 2016, promoted it to domain controller again and reconfigured the GPOs. I also set up another VPS as domain controller to act as a sort of backup. The servers are stable and everything works.  Problem: After I reinstalled OS on the DC I can't see the ~500 laptops that were joined earlier among the list of computers. I checked 1 laptop and it still shows itself as a member of the domain and still has existing policies but "gpupdate /force" fails and I suspect that all the older laptops won't be receiving any further updates on GPOs. At this point I don't mind manually rejoining the computers but almost all of those laptops are in the field. So I could either ask for a recall which is not gonna make me any friends or send them a .vbs script to join the computer to domain again and ask them to run it which, even if I assume everyone does, the .vbs contains the root password to the domain controller so that's a non-starter. So here's my 2 questions:   Is there any way I could rejoin those old laptops? Given that the laptops still 'consider' themselves as members of the domain. I think if I can just get them to show up in the domain computers list, I could reset the computer account and the trust issue should be solved... I think. We're unsatisfied with the support from the VPS provider and want to switch. Is there any way we can move to a new VPS with a new IP and not have to rejoin the computers again.   (I suspect the answer to second question would also answer the first one by default but I don't know for sure, so leaving it upto you.)  Bit of relevant info: We're using a publicly routable .net domain registered on godaddy. Using custom nameservers (ns1..net and ns2..net both pointing to the IP of dc1 as of now). Since the domain is publicly routable, we have set DNS of computers to 8.8.8.8 & 8.8.4.4 instead of the DCs ("gpupdate" works on newer computers with this configuration).  Thanks for reading and appreciate any guidance you can provide.  EDIT: System seems to have marked this question as duplicate of "Command to remove computer from non-existant domain". Completely different question though

I lost my domain controller machine, and then add new domain controller but with a new  domain. How do I remove network machines from old domain using command line and add to new domain? Machines using Windows Server 2008 Core (command line only)  net computer \\name del   works only on domain controller.  sconfig   When I try to exit from old domain, console requests username and password for exit. I type it, and then get error "Could not connect to domain" (old domain controller not exists)  What to do?


I have a dictionary of values read from two fields in a database: a string field and a numeric field. The string field is unique, so that is the key of the dictionary.  I can sort on the keys, but how can I sort based on the values?  Note: I have read Stack Overflow question here  and probably could change my code to have a list of dictionaries, but since I do not really need a list of dictionaries I wanted to know if there is a simpler solution to sort either in ascending or descending order.


I have made a custom module with a config/install folder containing many yml files from a drush configuration export. When activating the module , it does install the configuration. How can i delete all this config when i uninstall the module ?

I'm a bit confused about two different errors I get, which seem to contradict each other. I guess I didn't register my field types properly. The first one appears when I try to uninstall my module. Drupal\Core\Field\FieldException: Attempt to create a field field_example that does not exist on entity type node. in Drupal\field\Entity\FieldConfig->getFieldStorageDefinition() (line 312 of core\modules\field\src\Entity\FieldConfig.php).  The second one appears as an error message within the UI when I try to fix it by introducing another module which should only create the field type. Unable to install Helper, field.field.node.content_type_example.field_example already exists in active configuration.  In general, the module calls an external API and fetches data which is then used to create nodes with several fields. These are defined inside the config/install directory. Furthermore, inside src/Plugin/Field there are FieldType, FieldFormatter and FieldWidget classes, more or less as described . I used  module when I tried to fix the first error without a helper module. With its help, I removed the field types created by my module in the first place. Unfortunately, I don't know a lot about drush, which seems to be capable of solving the issue. On the other hand, it would be great if it was possible to "reset" the content type and the field types programmatically whenever the module is installed or uninstalled. So far, I tried the following code, without much luck: <?php // mymodule.install file use \Drupal\field\Entity\FieldStorageConfig;  function mymodule_install() {   if (FieldStorageConfig::loadByName('node', 'field_example')) {     FieldStorageConfig::loadByName('node', 'field_example')->delete();   } }  Does someone know how I can fix the error and how I should manage these fields in the future? Thanks!


Gunpowder is often referred to as the source of Gandalf's fireworks. But, it is never clearly stated what Gandalf's fireworks were made up of.  The fireworks were by Gandalf: they were not only brought by him, but designed and made by him; and the special effects, set pieces, and flights of rockets were let off by him. But there was also a generous distribution of squibs, crackers, backarappers, sparklers, torches, dwarf-candles, elf-fountains, goblin-barkers and thunder-claps.  A more likely possibility is that the fireworks were made with the power of Narya, the Ring of Fire, but that too is not confirmed. Another reference to gunpowder is through Saruman's inventions.  Even as they spoke there came a blare of trumpets. Then there was a crash and a flash of flame and smoke. The waters of the Deeping-stream poured out hissing and foaming: they were choked no longer, a gaping hole was blasted in the wall. A host of dark shapes poured in. ‘Devilry of Saruman!’ cried Aragorn.  It is never said that this 'bomb' was made up of gunpowder or Saruman's magical capabilities, but Peter Jackson used the former in the 2nd film.   Of course, this is completely non-canonical and doesn't prove that gunpowder exists in Tolkien's Middle-earth. Also, when Isengard was attacked by the Ents:  ‘Isengard began to fill up with black creeping streams and pools. They glittered in the last light of the Moon, as they spread over the plain. Every now and then the waters found their way down into some shaft or spouthole. Great white steams hissed up. Smoke rose in billows. There were explosions and gusts of fire. One great coil of vapour went whirling up, twisting round and round Orthanc, until it looked like a tall peak of cloud, fiery underneath and moonlit above. And still more water poured in, until at last Isengard looked like a huge flat saucepan, all steaming and bubbling.’  Also, during the Siege of Gondor:  But the engines did not waste shot upon the indomitable wall. It was no brigand or orc-chieftain that ordered the assault upon the Lord of Mordor’s greatest foe. A power and mind of malice guided it. As soon as the great catapults were set, with many yells and the creaking of rope and winch, they began to throw missiles marvellously high, so that they passed right above the battlement and fell thudding within the first circle of the City; and many of them by some secret art burst into flame as they came toppling down.  But again, though speculated, it is never stated in these 2 instances that it was gunpowder,  Therefore, is it even plausible to say that gunpowder exists in Middle-earth? Note: This is not a duplicate of:  I am asking about the evidence concerning the existence of gunpowder. Whereas the accepted answer in the linked post merely describes the existence of magic and it's different forms in Tolkien's legendarium and does nothing to describe the existence of gunpowder. The answer by Dronz is reasonable, but it seems speculative and there was no evidence given.

By the Third Age, gunpowder was obviously invented, but it was very rarely used. In late medieval and early modern Europe (and subsequently on the whole planet) it completely changed warfare.  As Middle Earth is a very low-magic setting, gunpowder would not be made obsolete by magic, as magic hardly exists at all.   We don't see any cannon artillery, or tercios which would mop up the floor with a similarly sized army from Middle Earth (maybe except the Elves whose archery would probably still be superior to muskets).


I made chocolate using cacao butter, cacao powder, sugar (icing and granulated), and dried milk powder.  In addition to being too sweet (panicked and added too much icing and granulated sugar), and too grainy (I removed the cacao butter from heat and added the other ingredients), it taseted really oily.  Why was the chocolate oily?  I made the following errors: 1. Not properly measuring everything (I couldn't find a suitable recipe) 2. Removing the cacao butter from heat and then adding the other ingredients  3. Not whisking the chocolate mixture  4. Not pre mixing the dry ingredients 5. Not sticking to icing sugar

I want to make plain dark chocolate at home.   The process is tricky in my experience, not simply mixing cocoa, cocoa butter, milk powder, sugar, etc.  Can you share some practical tips for doing the process and choosing the right ingredients.


I wanted to take a sneak peek at Windows 7 so I thought of installing it. I have Windows Vista on my laptop which came pre-installed with it. I didn't want to mess with it.  So I created a partition (20 GB) in my USB external hard disk and tried to install Windows 7 on that partition. But when I booted from a Windows 7 DVD and selected the target partition on USB hard disk, it said it cannot be installed.  Is there any way to install Windows on an external USB hard disk?

Is it possible to install Windows OS to plug and play storage devices such as external hard drives, HDD enclosures (with SATA hard drives), USB flashdrives and the likes? What OS's? And if it's possible, can I boot on it after the installation/formatting?  I've read someone has tried this already using Windows XP but failed since XP reinitializes all attached USB devices before loading OS, thus disabling the External HDD that is attached via USB port.  What about other Windows OS: on Windows 7 or 8.... or Windows 10?  I'm asking this because I'm planning to create a portable OS. When I'm at my house, when I go to my grandmother's, or to a friend's place: I just simple plug that portable storage device, change the boot priority, and turn on the system and ta-da! I will only see one environment every time.


I read often that preprint servers such as arXiv are changing how we publish. However, no one in my area of medical imaging uses them and they are regarded in my lab with suspicion.  I currently have a finished manuscript that I am about to send to an IEEE transaction journal. I would like a preprint of this manuscript to be publicly available for several reasons. However, my supervisors are worried this might invalidate my ability to publish this manuscript. They don't want to take the risk that I do this wrong and can't publish.  So here is the simple question I never seem to see a simple answer to. Here is a finished manuscript, fully formatted for the journal I am going to submit it to, in PDF. Can I submit this  PDF as a pre-print to arXiv right now, or not? Will the publisher still consider publishing it? To play devil's advocate, why wouldn't IEEE say, this has already been published in the arXiv, it is no longer new work?  Edit: Here is what IEEE says: "Does IEEE consider an author posting her paper on preprint servers or on her company's web sites to be a form of prior publication, which may then disqualify the paper from further editorial consideration? No. IEEE policy allows an author to submit previously posted papers to IEEE publications for consideration as long as she is able to transfer copyright to IEEE, i.e., she had not transferred copyright to another party prior to submission."

Is it legal to upload a paper to arXiv when it is under double blind review for one of the IEEE journals? I am suspicious that it may violate the double blind review requirements and I couldn't find any thing in the journal's homepage specific to this issue. In general IEEE allows preprint versions to be uploaded to arXiv.


EDIT: this question is not covered  as this does not refer to subscript or superscript  QUESTION:  How do I use subscript or superscript in comments?  <sup> and </sup> don't work.  I see the chemists using latex in comments ?  Maybe that's the only way?

Across the Stack Exchange network you may leave comments on a question or answer.  How do comments work? What are comments for, and when shouldn't I comment? Who can post comments? Who can edit comments? How can I format and link in comments? My comment doesn't contain some of the text I typed in it; why? My comment appears to be long enough, but I can't post it because it's too short; why? Who can delete comments? When should comments be deleted? Why can't I comment on specific posts even if I have enough reputation to comment? When can comments be undeleted? What are automatic comments? How can I link to comments? Anything else I should know about comments?  Also see the FAQ articles on  and .


I don't understand the formula at all:  $$e^{ix} = \cos(x) + i \sin(x)$$  I've tried reading all sorts of webpages and answers on the subject but it's just not clicking with me. I don't understand how we can define things when these are already known quantities. We've already got an exact definition for $e$ as $\lim_{n \to 0} (1+\frac{1}{n})^n$, and we've got $i = \sqrt{-1}$, and we've got $\cos$ and $\sin$ as the $x$ and $y$ coordinates of where right triangles meet the unit circle.   So I don't understand how we get from those figures to Euler's formula. Then again I also don't understand why complex numbers are of the form $a + bi$ so that might have something to do with it. I have a hard time separating what identities are "emergent" from the previous mathematics and which pieces are "by definition" and why they are defined that way. I don't understand why we start talking about "rotations" as if it's obvious that's what's happening. I don't even know why $e$ is involved in any of this to begin with.   Is $e^{ix}$ simply being written in the slightly rearranged complex form $a + ib$ where $a = \cos(x)$ and $b = \sin(x)$? Is this to be interpreted as $\cos(x)$ being the $x$-coordinate and somehow $i \sin(x)$ is the $y$ coordinate?

Euler’s formula states that $e^{i  x} = \cos(x) + i \sin(x)$.  I can see from the MacLaurin Expansion that this is indeed true; however, I don’t intuitively understand how raising $e$ to the power of $ix$ produces rotation.  Can anyone give me an intuitive understanding?


Let $f:\mathbb{R}\rightarrow\mathbb{R}$ be a continuously differentiable function such that $\underset{x\rightarrow\infty}{\lim}\frac{f(x)}{x}=0$ and suppose $\underset{x\rightarrow\infty}{f'(x)}$ exists. Then Prove that $\underset{x\rightarrow\infty}{f'(x)}=0$    I can see that if we apply L'hoptal's theorem directly to $\frac{f(x)}{x}$ then we can get the answer. But is it possible to do so without knowing the value of $\underset{x\rightarrow\infty}{f(x)}$  On the similar problem: , they have given the existence of $\lim_{x\rightarrow\infty} f(x)$. But in this particular problem they haven't

I've been trying to solve the following problem:  Suppose that $f$ and $f'$ are continuous functions on $\mathbb{R}$, and that $\displaystyle\lim_{x\to\infty}f(x)$ and $\displaystyle\lim_{x\to\infty}f'(x)$ exist. Show that $\displaystyle\lim_{x\to\infty}f'(x) = 0$.  I'm not entirely sure what to do. Since there's not a lot of information given, I guess there isn't very much one can do. I tried using the definition of the derivative and showing that it went to $0$ as $x$ went to $\infty$ but that didn't really work out. Now I'm thinking I should assume $\displaystyle\lim_{x\to\infty}f'(x) = L \neq 0$ and try to get a contradiction, but I'm not sure where the contradiction would come from.   Could somebody point me in the right direction (e.g. a certain theorem or property I have to use?) Thanks


Why do we use the group $SU(3)$ and not $SL(3, \mathbb{R})$ for color charge?  As far as I can tell, the $SL(3, \mathbb{R})$ is volume and orientation preserving, by the fact that it has unit determinant, and if I'm not mistaken the only thing that $SU(3)$ adds is that it is inner product conserving?  And now to play devils advocate, does that still matter? Ever since the Klein-Gordon equation we have stopped viewing fields as wave-functions, and the expectation values come from calculating things like  $$< F > = \frac{\int \mathcal{D}\phi F[\phi] e^{i S[\phi]}}{\int \mathcal{D}\phi e^{i S[\phi]}},$$  so wouldn't such differences be divided out?  I've also calculated the structural constants and noticed that the anti-symmetric ones are all identical apart from a sign change in $f_{257}$, although for the symmetric ones there are actually a lot of sign changes.  Also, I kind of struggle to see why $SL(3, \mathbb{R})$ would not be norm conserving, is it possible to show this fairly easily?

What is the motivation for including the compactness and semi-simplicity assumptions on the groups that one gauges to obtain Yang-Mills theories?  I'd think that these hypotheses lead to physically "nice" theories in some way, but I've never, even from a computational perspective. really given these assumptions much thought.


Looking to be able to search the contents of an Excel spreadsheet from the SharePoint mobile app.  I have a spreadsheet with Postal Codes/Zip Codes with corresponding information. I would like to be able to search for a Postal/Zip Code as you would in Excel if you pressed "CTRL + F" FIND for example.  Is there a way to upload the spreadsheet and when you open it in the app, have the magnifying glass to click on or a field to type into without the need to install the Excel mobile app?  When I upload a test spreadsheet, it opens as like a PDF. User has "Read" permissions for the document library the spreadsheet is located in. I do not want the user to be able to edit any information, just serach/find/view it.  Thanks in advance,  (repost from guest account)

Looking to be able to search an Excel spreadsheet from the SharePoint mobile app.  I have a spreadsheet with Postal Codes/Zip Codes with corresponding information. I would like to be able to search as you would in Excel.  When I upload a test spreadsheet, it opens as like a PDF. User has "Read" permissions for the document library the spreadsheet is located in.  Thanks in advance,


I have got the following code in my unit test. But, it returns the error mentioned when run.  var leaveTypesList = new List<LeaveType>() { leaveType1, leaveType2, leaveType3 }; var leaveTypesQueryable = leaveTypesList.AsQueryable(); mockLeaveTypeRepository.Setup(r => r.GetLeaveTypes()).Returns(leaveTypesQueryable); var leaveTypeDtos = service.GetLeaveTypes();   The error is generated from the last line when the results are returned from the service.  The service code for the GetLeaveTypes method listed below, which is a simple accessing of the repository.      public IQueryable<LeaveTypeDto> GetLeaveTypes()     {         //return Mapper.Map<IQueryable<LeaveTypeDto>>(leaveTypeRepository.GetLeaveTypes());         return leaveTypeRepository.GetLeaveTypes().ProjectTo<LeaveTypeDto>();     }   The repository code is also a simple return of an IQueryable of leave types.      public IQueryable<LeaveType> GetLeaveTypes()     {         return dbContext.LeaveType.Where(lt => lt.IsActive);     }   Just cannot figure out what is wrong here. Any ideas?

I have an List and I'd like to wrap it into an IQueryable.  Is this possible?


Let's define $x=\sqrt{ab}$, where $a=-1$ and $b=-1$.  Does $x=1$, as $-1\cdot-1=1\implies\sqrt{-1\cdot-1}=\sqrt{1}=1$?  Or maybe $x=-1$, as $\sqrt{a^2}=a\implies\sqrt{-1\cdot-1}=\sqrt{(-1)^2}=-1$?  I assume that at least one of the following is true:   The former solution is true, and the fallacy is in assuming $\sqrt{a^2}=a$ for a negative base $a$. This doesn't seem to hold, given that this is equivalent to saying that $a^{2^{\frac12}}\not=a^{2\cdot\frac12}=a$ for a negative $a$, where the value of $a$ seemingly has no bearing on the arithmetic performed with the exponents. The former solution is true, and the fallacy is in assuming the positive root is meant in the latter solution; in fact, $\sqrt{-1\cdot-1}=-\sqrt{(-1)^2}=--1=1$. But this implies that, depending on how the radicand is factored, one is forced to take the positive root for one factoring and the negative root for another factoring to get the same answer, which doesn't seem right. The latter solution is true, and the fallacy is in assuming the positive root is meant in the former solution; in fact, $\sqrt{-1\cdot-1}=-\sqrt1=-1$. But, in addition to the problem with the previous solution, this additionally means that $\sqrt{ab}=\sqrt{a}\sqrt{b}$ holds even for negative $a,b$.   Which of my reasonings is incorrect? Or are all of them correct, and there's an additional solution that I'm not seeing?

I know there must be something unmathematical in the following but I don't know where it is: \begin{align} \sqrt{-1} &= i \\\\\ \frac1{\sqrt{-1}} &= \frac1i \\\\  \frac{\sqrt1}{\sqrt{-1}} &= \frac1i \\\\  \sqrt{\frac1{-1}} &= \frac1i \\\\  \sqrt{\frac{-1}1} &= \frac1i \\\\  \sqrt{-1} &= \frac1i \\\\  i &= \frac1i \\\\  i^2 &= 1 \\\\  -1 &= 1 \quad !!? \end{align}


One of my pages is set up so that the initial page title is just some placeholder title, and it changes after an AJAX call.  Here's what the process looks like:   Initial page load AJAX call to retrieve some data Page title changed according to AJAX data   Does Google take page title changes into account? Or does Google only look at what the initial page title is?

In my page I need to add alt tags and Title tags from JavaScript after the DOM is loaded.   So I would like to check whether these dynamically added values will be considered during Google SEO audit.  If they are not counted, what is the solution to get dynamically appended alt tags considered.


I live in a small town home and have limited indoor bike storage. The space that I do have outdoors is too small for products like the tidy tent. Any recommendations?

I've got insufficient space to store my bike inside. I fear however that it will rust away within a few years if I store the bike outside. My question is twofold:   Will storing a bike outside be a problem? What can I do to prevent rust and possibly other types of decay?


I want to measure the performance speed of my method in runtime execution but i am not sure if what i have done is really measured the performance of my method i want or is doing something else. If it is measuring the performance speed of my method than how reliable it is. The method which i want to measure performance speed is called FFMulFast and it calculates the multiplication of two polynomials part of Galois Field (256). Note : i will present only code which is relevant to my question.    public class GaloaField {   // some fields here       public int FFMulFast(int a, int b){    int t = 0;;    if (a == 0 || b == 0)    return 0;       /* The multiplication is done by using lookup tables. We have used both   logarithmic and exponential table for mul     * the idea is firstly look to Logarithmic table then add their powers and find the corresponding of this to exponential table */    t = (Log[(a & 0xff)] & 0xff) + (Log[(b & 0xff)] & 0xff);   if (t > 255) t = t - 255;   return Exp[(t & 0xff)];   }    //some other methods here       public void runABunch() { //method which will measure the performance speed of FFMulFast       long start = System.nanoTime();        int a=0x56;        int b=0xf4;        for (int i = 0; i < 5000000; i++)          FFMulFast(a,b);        long end = System.nanoTime();        System.out.println("Time: " + (end-start));    }      public static void main (String [] args) {      GaloaField galoa=new GaloaField();       galoa.runABunch();   }

How do you write (and run) a correct micro-benchmark in Java?  I'm looking for some code samples and comments illustrating various things to think about.  Example: Should the benchmark measure time/iteration or iterations/time, and why?  Related:


When viewing the history tab then both tabs are toggable        When viewing the traffic sources tab then only the history tab exists

I was seeing the Site Analytics page (/site-analytics)  (>25K users) and also  and found out that the header is not consistent:   When in history, the header shows "history | traffic sources" When in traffic sources, the header just shows "history"   Graphically:


I have an Acer D20 with an Intel GMA3600 card. Is graphic acceleration for this card supported? Videos, flash, and other graphic intensive operations struggle with the current setup.

I was planning to buy Acer Aspire One D270 within a few days and as everybody installs linux on their netbook I was also planning to do that.  Now, my question is how is Acer's hardware compatibility with linux and specifically in respect to the new Acer Aspire One D270.  Has anybody tried installing linux on these new netbooks. It will be a great help if a D270 user can share his/her experience with linux usage.  I read on some forums that there is some linux driver issue with Intel GMA 3600 and that people are not able to adjust their brightness. So, as I am a linux noob is this a major issue or not.  Specs:  RAM : 2Gb DDR3 Processor: Intel N2600(Cedar Trail) Graphics: Intel GMA 3600 HardDisk: 320Gb 5400 rpm


We know that on an idempptent semiring $R$, the natural order relation is defined as: for all $x, y\in R$, $x\leq y$ when $x+y=y$, which is clearly a partial order relation. I am unable to point out whether this relation is a total order relation too? i.e., does it satisfy Comparability (trichotomy law)?

We know that on an idempotent semiring $R$, the natural order relation is defined as: for all $x, y\in R$, $x\leq y$ when $x+y=y$, which is clearly a partial order relation. I am unable to point out whether this relation is a total order relation too? i.e., does it satisfy Comparability (trichotomy law)?


Last month we changed service providers for the internet. I believe they also changed the modem/router at the same time. As a result Google no longer recognizes me and I can not access my old account. I have important contact information particularly some medical contacts. my old account was nyob415@gmail.com. Thank you

I have forgotten the password or username for my Google account, or I'm unable to access my account for other reasons.  How can I recover my account?  (This Q&A is meant as a general description for all Google and Gmail username/password questions. See: )


I believe term ‘learning rate schedule’ is a certain solution for tuning the learning rate. But at the same time, every parameter evaluating the parameter itself can be called a hyperparameter. So can the learning rate schedule be called a hyperparameter?

I have noticed that such terms as model hyperparameter and model parameter have been used interchangeably on the web without prior clarification. I think this is incorrect and needs explanation. Consider a machine learning model, an SVM/NN/NB based classificator or image recognizer, just anything that first springs to mind.   What are the hyperparameters and parameters of the model? Give your examples please.


Does $S^1 \times S^3$ admit a complex structure?   It is parallelizable, so it admits an almost complex structure...is there a nice way to see that this is or is not integrable?

Apparently there is a complex structure on $X = \mathbb S^1 \times \mathbb S^3$ but I have no ideas why. Any hints ?


When I upgraded to Ubuntu 14.04, apparently my kernel was supposed to upgrade from 3.11 to 3.13. Unfortunately, the kernel upgrade did not complete. As a result, I have several files for 3.13, but am still running 3.11. I've decided the best thing for me to do is to complete the kernel upgrade.  Specifically, when I look at the linux packages I have installed, I see:  me@Bedrock1:~/Downloads/cudaDownloads$ dpkg -l | grep "linux-" | cut -d " " -f 3 gcc-4.8-powerpc-linux-gnu-base linux-firmware linux-headers-3.13.0-29 linux-headers-3.13.0-29-generic linux-headers-3.13.0-30 linux-headers-3.13.0-30-generic linux-headers-3.13.0-32 linux-headers-3.13.0-32-generic linux-headers-3.13.0-34 linux-headers-3.13.0-34-generic linux-headers-3.13.0-35 linux-headers-3.13.0-35-generic linux-headers-3.13.0-36 linux-headers-3.13.0-36-generic linux-headers-3.13.0-37 linux-headers-3.13.0-37-generic linux-headers-3.13.0-39 linux-headers-3.13.0-39-generic linux-headers-generic linux-image-3.11.0-23-generic linux-image-3.8.0-33-generic linux-image-extra-3.11.0-23-generic linux-image-extra-3.8.0-33-generic linux-libc-dev:amd64 linux-sound-base linux-source linux-source-3.13.0 syslinux-common syslinux-legacy  and, when I look in my boot directory, I see:  me@Bedrock1:~$ ls /boot abi-3.11.0-23-generic         memtest86+.bin abi-3.8.0-33-generic          memtest86+.elf config-3.11.0-23-generic      memtest86+_multiboot.bin config-3.8.0-33-generic       System.map-3.11.0-23-generic grub                          System.map-3.8.0-33-generic initrd.img-3.11.0-23-generic  vmlinuz-3.11.0-23-generic initrd.img-3.8.0-33-generic   vmlinuz-3.8.0-33-generic    It looks as though I can use apt-get/synaptic to install linux-image-3.13 and linux-image-extra-3.13, but I can't find downloads for any of the files in my /boot directory. Is there something obvious I'm missing here?  Should I expect installation of the correct packages to update GRUB files as necessary, or will I need to read up on that before I start booting into the 3.13 kernel?  Are there any other files I should be checking for?  Is there an obvious reason why my kernel didn't manage to update completely to 3.13? If so, do I need to compensate for it?

I just upgraded from 13.10 to 14.04, but when I do uname -r, it says I have kernel 3.11. I want to have the default 14.04 kernel, (3.13 I believe). How can I get this?


I need help determining the sample size necessary for a logistic regression (binary DV) with two continuous predictors and also the sample size necessary if I use three continuous predictors.

I want to make a logistic model from my survey data. It is a small survey of four residential colonies in which only 154 respondents were interviewed. My dependent variable is "satisfactory transition to work". I found that, of the 154 respondents, 73 said that they have satisfactorily transitioned to work, while the rest did not. So the dependent variable is binary in nature and I decided to use logistic regression. I have seven independent variables (three continuous and four nominal). One guideline suggest that there should be 10 cases for each predictor / independent variable (Agresti, 2007). Based on this guideline I feel that it is OK to run logistic regression.    Am I right? If not please let me know how to decide the number of independent variables?


Assume $f$ is Riemann integrable and further assume that $\int_a^x f=0$ for all $x$. How would I go about showing that $f$ itself is $0$ almost everywhere?  I am new to Lebesgue's measure theory so I am hoping for a somewhat elementary proof if possible?  I know that almost everywhere means all except a set of measure zero. I was wondering if I could get a point to start on? We are told $f$ is Riemann integrable, so that means by Lebesgue's criterion for Riemann integration that there are at most countably infinitely many discontinuities. Thank you!

I have been thinking on and off about a problem for some time now. It is inspired by an exam problem which I solved but I wanted to find an alternative solution. The object was to prove that some sequence of functions converges weakly to zero in $L^2$.   I managed to show (with some help) that the limit $f$ (of a subsequence) satisfies $\int_0^x f \ dm=0$ for all $x>0 $. From this I want to conclude that $f=0$ a.e. I can do this with the fundamental theorem of calculus in its Lebesgue version but there ought to be a more elementary proof.  Can someone here help me out?


I have a server with 150GB of diskspace. Today I uploaded a dataset of 30GB. I cancelled the import due to internet dying, then noticed there was 29GB of space missing in the database (meaning the CSV was uploaded, but not deleted when I broke the operation). When uploading the data once again, it broke again and I lost another ~25GB. Now there isn't enough free space to upload the data.  This is hosted on AWS RDS, Postgres 10.6.  Is there a way to fix this? But will this delete records? I'm hosting at the moment ~70GB of data and don't want to lose any records. What's the best way to go about this?

I have a server with 150GB of diskspace. Today I uploaded a dataset of 30GB. I cancelled the import due to internet dying, then noticed there was 29GB of space missing in the database (meaning the CSV was uploaded, but not deleted when I broke the operation). When uploading the data once again, it broke again and I lost another ~25GB. Now there isn't enough free space to upload the data.   This is hosted on AWS RDS, Postgres 10.6.   Is there a way to fix this? I read about VACUUM. But will this delete records? I'm hosting at the moment ~70GB of data and don't want to lose any records. What's the best way to go about this?


I just use documentclass(report) and \listoftables. And my tables in the documents have so long names for section name, like III.3.1.1 , and so on. So, when i compile the tex file, it became like this :    any idea to fix that? Thank you.

I'm preparing a document using the book class. In the table of contents, the space between the subsection number and title is too wide. How to reduce it?


This was only about 5-6 years ago but there was a book I remember reading a lot of in High School. It was about a girl and her little brother who lived in this sewer city beneath another city, there was a lot of cement. Their school bought into this government program to feed the kids a weird paste and then they all were playing VR pod "games" with aerial battles. Turns out the government was trying to build an army, the siblings find out the people living above them are the uber rich, both groups think outside this cylinder is nothing but death and pollution, but after going over the wall in a plane they find lush forests where the uber-uber rich are living.

Sci-fi book in the future about a city that had 2 levels.    The top level was for the rich people. A game center with a space flight game is added. The main character (male) plays with friends and wins a competition. He ends up in huge competition and does well. He finds his sister (twin I believe) and joins the military as the competition was just a recruitment game. He flies into "destroyed land" and finds out that rich barons are living on private islands.  The destroyed lands were caused by some plague.  I read this book in 2010.


Is the following code vulnerable to Sql injections and how to validate it ?    $query=("select * from table2 where username = '$username'and password='$password'"); $result=  mysqli_query($connect, $query);        $row=  mysqli_fetch_assoc($result);     if  ($username==$row['username']&&$password==$row['password'])     {         header('location:header.php');//to go header         } else {     header('location:insert_p.php');}

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?


private static HSSFSheet ExcelWSheet;  private static HSSFWorkbook ExcelWBook;  private static HSSFCell Cell;  private static HSSFRow Row;  private  static String[][] getTableArray(String FilePath, String SheetName)    throws Exception  {         FileInputStream ExcelFile = null;     String[][] tabArray = null;     try{         ExcelFile = new FileInputStream(FilePath);         // Access the required test data sheet         ExcelWBook = new HSSFWorkbook(ExcelFile);         ExcelWSheet = ExcelWBook.getSheet(SheetName);         int startCol = 1;         int ci=0;         int totalRows = ExcelWSheet.getPhysicalNumberOfRows();         int totalCols = ExcelWSheet.getRow(1).getLastCellNum();         System.out.println(totalRows);         System.out.println(totalCols);         tabArray=new String[totalRows][totalCols];         DataFormatter formatter = new DataFormatter();            for (int j=1;j<=totalRows;j++, ci++)             {                //totalCols = ExcelWSheet.getRow(j).getPhysicalNumberOfCells();                //tabArray=new String[totalRows][totalCols];                int cj=0;                for (int l = 1; l < totalCols;l++, cj++) {                 //tabArray[ci][cj] = getCellData(j, l);                  Cell = ExcelWSheet.getRow(j).getCell(l);                   String CellData = formatter.formatCellValue(Cell);                  System.out.println(CellData);                   tabArray[ci][cj] = CellData;                  System.out.println(j);                 System.out.println(l);                 System.out.println(tabArray[ci][cj]);                 System.out.println("tabArray["+ci+"]["+cj+"]: "+tabArray[ci][cj]);             }              }            System.out.println(tabArray);     }      catch (FileNotFoundException e)      {          System.out.println("Could not read the Excel sheet");          e.printStackTrace();      }      catch (IOException e)      {          System.out.println("Could not read the Excel sheet");          e.printStackTrace();      }finally {          ExcelFile.close();     }      return tabArray;  }   ///// Cell = ExcelWSheet.getRow(j).getCell(l); here where its throwing null pointer exception.  coloumns heading are TestCases,Enquiry ID, Sl No., Material  need to read from the 2nd column Enquiry ID only and pass one by one in data driven framework.  want to read enquiry ids from excel and pass it to my @test 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?


I came across the following statement:  International law, after all, is a system of manners written large.  I'm a native English speaker and translator, and I'm having a hard time translating this statement because I'm not clear on what is meant by written large. I wouldn't even know how to paraphrase this. Please answer if you're sure of the answer - no guesses please.

I have seen this used with other words besides "large" and "small".  What other words can be used? Can this structure be used more generally with other adjectives?


Does anyone know if it's possible to change the Spotlight default search behavior to search file names, not contents? Right now, bringing up the Spotlight field and typing "terrible" brings up a bunch of documents that have the word "terrible" somewhere in them. If you use the Finder search dialog, of course it's possible to select the 'Filename contains "terrible"' option manually, but I'd like to make this the default.

In Finder when I type something in the textbox the default is to search the whole mac in the contents of the files. I was able to change the default to search the current directory, but didn't see an option to change search for contents to search for file name. How can that be changed?


I started a 2D Tilegame programmed with libgdx which needs potentially infinite tiles. That means when the player arrives the border of the map it should be possible to generate even more tiles. So a simple 2D Array is not the best datastructure for that purpose.  A better solution I found here in the comments from dlras2:   it seems like he put 2D arrays in 2D arrays and that again and again, that reduces a lot of memory compared to one array for all tiles:   The problem is that I dont know before how many times the arrays will be encapsulated so it should be easily possible to wrap a new Array around if it is needed.  dlras2 also posted his code in C#, but I dont understand anything from it. Do you have an idea how to implement such a datastructure of recursive Arrays in Java? Or how to translate the whole C# code into Java? I hope the other stuff like putting tiles in the right array I'll solve by my selve.

I have a 2D platformer that currently can handle chunks with 100 by 100 tiles, with the chunk coordinates are stored as longs, so this is the only limit of maps (maxlong*maxlong). All entity positions etc etc are chunk relevant and so there is no limit there.  The problem I'm having is how to store and access these chunks without having thousands of files. Any ideas for a preferably quick & low HD cost archive format that doesn't need to open everything at once?


I'm a new for blender i'm watching on youtube about adjust major segment but i find not found this menu on blender 2.90.1 Where is major segment in blender 2.9x

The tutorial I read is based on 2.79. So I'm not sure if it's still the same name in 2.8. But I can't find anything providing similar functionalities.


I tested my regex with Regex101 already, but when I tried in Python 3.5.1 it returns None  Here's my   And here's my Python code. Not sure if I miss anything.  Python 3.5.1 |Anaconda 2.4.0 (x86_64)| (default, Dec  7 2015, 11:24:55) [GCC 4.2.1 (Apple Inc. build 5577)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import re >>> p = re.compile('([01]?[0-9]+:?[0-9]*(?:[AP]M)?)-([01]?[0-9]+:?[0-9]*(?:[AP]M)?)', re.MULTILINE) >>> m = p.match('NO PARKING (SANITATION BROOM SYMBOL) 7AM-7:30AM EXCEPT SUNDAY') >>> print(m) None >>>

What is the difference between the search() and match() functions in the ?  I've read the  (), but I never seem to remember it.  I keep having to look it up and re-learn it.  I'm hoping that someone will answer it clearly with examples so that (perhaps) it will stick in my head.  Or at least I'll have a better place to return with my question and it will take less time to re-learn it.


Let $X$ be a normed linear space, then the zeros of a discontinuous linear functional is dense in $X$.  If $Z_f$ is set of zeros then $Z_f$ will not be closed i.e. $Z_f\subsetneq \overline{Z_f}$, but don't know what to do after that.

I need to prove that: If a nonzero linear functional $f$ on a Banach Space $X$ is discontinuous then the nullspace $N_f$ is dense in $X$.   To prove that $N_f$ is dense, it suffices to show that $\overline N_f = X$ which is equivalent to $(X \setminus N_f)^o=\emptyset$. (the interior of complement of $N_f$ is null set.) Since $f$ is a linear functional and is discontinuous, it has to be unbounded. I don't know exactly how to utilize these observations.   Also on a related topic, I'm a little confused about how to exploit the a Linear Functional $f:X \to R$ or a Linear Operator $T:X \to Y$ being unbounded. Can I say that if a linear operator is unbounded then exists a sequence $<x_n>$ in $X$ s.t.  $||Tx_n|| > n^2||x_n||$ for each $n$ or $||Tx_n|| > n||x_n||$ ?


I would like to reply to a statement Look forward to seeing you tomorrow.   Can I write I look forward too to see you tomorrow?   OR   I look forward to see you tomorrow too/as well?  I would appreciate if anyone could point out the mistake(s) in the above two responses. Also, if the two statements are not correct, what could be the alternative sentence?  Thank you for your help.

Which of the  2 sentences is correct?  Sam is looking forward to see the Rocky mountains.  Sam is looking forward to seeing the Rocky mountains.